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DEMONSTRATIONS OF
ANATOMY.

/VA'.f

ELLIS'S DEMONSTRATIONS

ANATOMY

BEING A

IDE TO THE KNOWLEDGE OF THE HUMAN BODY

DISSECTION

tETlJOflftt) CUttion

REVISED AND EDITED BY

CHRISTOPHER ADDISON, M.D., B S. (Lond.)

F.R.C.S.

LECTURER OX ANATOMY, CHARING CROSS HOSPITAL, MEDICAL SCHOOL ;

FORMERLY HUNTERIAN PROFESSOR. ROYAL COLLEGE OF SURGEONS,

ENGLAND ; EXAMINER IN ANATOMY. ROYAL COLLEGE OF

SURGEONS. ENGLAND, ETC.

ILLUSTRATED BV 'Sm ENGRAVINGS ON WOOD, OF
WHICH 75 ARE IN COLOR

NEW YORK

WILLIAM WOOD AND COMPANY

MDCCCCVI

PREFACE.

In preparing this edition of Ellis*s " Demonstrations of
Anatom}^" it has been my first care to preserve those
features for which the book has been so justly vahied in
the past, and not to interfere with its general style and
character.

The advances in the knowledge of anatomy during recent
years and the present order of teaching have, however,
necessitated many changes.

The matter has been altogether re-arranged, and it now
follows the ordinary course of dissection as taken by students,
beginning with the simpler anatomy of the upper and lower
limbs and ending with the more complex parts of the head
and neck and the organs contained therein.

In some places old matter has been taken away, and in
many parts new work has been brought in, especially in those
dealing with the different viscera. In this connection I wish
to acknowledge the debt I owe to the works, amongst others,
of Birmingham, Cunningham, Symington, Keith, Dixon,
Elliot Smith, Berry, Jonnesco, Young and Robinson.

Sixty-two illustrations have been added, twenty-seven of
them in colours, and amongst the subjects of these latter are
those of many of the bones showing the attachments of^the
muscles. Forty- eight old illustrations have been reproduced
in colour, and several of the blocks have been retouched.

vi I*REFACI5.

Mr. T. P. Collings has devoted much care to the execution
of this part of the work.

I am grateful to the publishers for the ready manner in
which they met my requests ; and my sincere thanks are due
to Mr. W. S. Fenwick, B.Sc, for his help in preparing rough
drawings of some of the new illustrations, in reading .proofs,
and for many good suggestions. He also, with Mr. A. E.
Ironside, has carried through the work on the Index.

CHEISTOPHER ADDISON.

CONTENTS.

CHAPTER I.

DISSECTION OF THE UPPEK LIMB.

Superficial Parts of the Back

PAGE
1

CHAPTER II.

DISSECTION OF THF TPPEK LIMB.

Section 1. The Axilla J J

2. Scapular Muscles, Vessels, Nerv^es and Ligaments . . 28

3. The Front of the Arm ^^

The Back of the Arm 50

4. The Front of the Forearm 5*

5. The Palm of the Hand ^^

6. The Back of the Forearm ^p

7. Ligaments of the Shoulder, Elbow, Wrist, and Hanil . . 92

The Elbow Joint ^^

The Wrist Joint ^^

CHAPTER III.

DISSECTION OF THE LOWER LIMB.

Section 1. The Buttock, or Gluteal Rpjrion
2. The Popliteal Space .

The Back of the Thigh .

109

124
130

CHAPTER IV.

DISSECTION OF THE LOWER LTMB.

Section 1. The Front of the Thigh 1^5

Parts concerned in Femoral Hernia 143

Scarpa's Triangular Space 146

Deep Parts of the Front of the Thigh . . . . 150

2. The Inner Side of the Thigh 1^1

3. The Hip- Joint 1^^

4. The Front of the Leg and Foot 174

5. The Back of the Leg 1^^

6. The Sole of the Foot ^^'

CONTENTS.

Section 7. Ligaments of Knee, Ankle, and Foot
Tibio-Fibular Articulations .
Articulation of the Ankle

PAGE

212
221
222

CHAPTER V.

DISSECTION OF THE PERINEUM.

Section 1. Perineum of the Male ....
Posterior Half of the Space
Anterior Half of the Perineal Space
2. Perineum of the Female ....

236
237
243
255

CHAPTER VI.

dissection of the abdomen.

Section 1. Wall of the Abdomen ....
The Spermatic Cord and the Testis .

2. Hernia of the Abdomen

3. Cavity and Regions of the Abdomen

Relations of the Viscera

The Peritoneum ....

Mesenteric Vessels and Sympathetic Nerves

Relations of Aorta and Vena Cava .

Removal of the Intestines

Small Intestine ....

Large Intestine .....

Relations of the Duodenum and Pancreas

The Stomach Bed ....

Coeliac Axis and Portal Vein .

Sympathetic and Vagus Nerves

The Stomach

Duodenum and Pancreas D's«ected
The Spleen .....

The Liver

The Gall- Bladder ....
Kidneys and Ureters ....
Suprarenal Bodies ....
Diaphragm with the Aorta and Vena Cava
Deep Muscles of the Abdomen .
Spinal and Sympathetic Nerves

260
277
285
'i96
300
307
314
319
320
321
324
327
330
331
336
338
341
343
345
351
353
357
358
368
371

CHAPTER VIL

DISSECTION OF THE PELVtS.

Section 1. Cavity of the Pelvis 376

The I'eritoneum, the Pelvic Fascia and the Muscles of

the Outlet 376

Relations of the Viscera in the Male 384

>> ,, ,, Female .... 390

Vessels and Nerves of the Pelvis 395

CONTENTS. ix

PAGE

Section 2. Anatomy of the Visoera of the Male Pelvis .... 405

The Bladder 409

The Urethra and Penis 411

Rectum 417

3. Anatomy of the Female Pelvic Vi.scera 418

The Vagina 419

The Uterus 420

Ovaries and Fallopian Tubes . . . . . 423

Bladder, Urethra, and Rectum 425

4. Ligaments of Pelvis 427

CHAPTER VIII.

DISSECTION OF THE THOKAX.

Section 1. Walls of the Thorax 436

2. Cavity of Thorax ......... 441

The Plenrfe 442

Relations of the Lungs ....... 446

Pericardium ........ 449

Heart, and its Large Vessels . . . . . 452

Nerves of the Thorax ....... 470

Opening of Aorta and Structure of Heart . . • . . 473

Trachea and Lungs ....... 477

Parts of Spine, and the Sympathetic Cord . . 480

3. Ligaments of the Trunk 489

CHAPTER IX.

DISSECTION OF THE HEAD AND NECK.

1. External Parts of the Head ....

2. Internal Parts of the Head

3. Deep Di.s.section of the Back ....

4. The Spinal Cord and its Membranes

5. Dis.section of the Face .....

External Parts of the Nose ....
The Appendages of the Eye ....
The External Ear

6. Dissection of the Neck ......

Posterior Triangular Space

Front of the Neck . . .

Anterior Triangular Space ....

7. The Ptery go-Maxillary Region ....

8. The Submaxillary Region

9. The Deep Vessels and Nerves of the Neck

10. The Orbit

11. The Pharynx and the Cavity of the Month

12. The Nose

13. The Spheno-Palatine and Otic Ganglia, the Final Branches

of the Internal Maxillary Vessels, the Facial Nerve, and
the Internal Carotid Artery in the Temporal Bone j^ . .

499
507
519
538
550
565
566
569
572
574
579
580
607
619
626
639
654
667

673

X ' CONTENTS.

PAGE

Section 14. The Tongue 682

15. The Larynx 688

16. The Hyoid Bone, the Caitilages and Ligaments of the Larynx,

and the Structure of the Trachea 698

17. The Prevertebral Muscles and the Vertebral Vessels . 704

18. Ligaments of the Vertebrae and riavicle .... 707

CHAPTKR X.

DISSECTION OF THE liUAlN.

Section 1. Membranes and Vessels ........ 715

2. The Base of the Brain and the Origin of the Cranial Nerves . 725

3. The Medulla Oblongata and Pons Varolii 731

The Pons Varolii 738

4. Dissection of tiie Cerebrum ..... .740

The Fissure.s, Sulci and Convolutions .... 745

Interior of the Cerebrum . . ..... 755

5. The Cerebellum, the Fourth Ventricle, and the Nuclei of the

Cranial Nerves. ........ 776

CHAPTER XL

Dissection of the Eye ........... 790

CHAPTER XII.

Dissection of the Ear 803

The External Ear . . 803

The Middle Ear 805

The Internal Ear 814

INDEX 823

^^V. 3<WvV S- \^o.Vh

DEMONSTRATIONS OF ANATOMY.

DISSECTION OF THE UPPER LIMB.

CHAPTER I.
DISSECTION OF THE BACK.

General Directions. The student begins his work in practical
anatomy by the dissection either of the upper or of the lower limb.
During the first three days that the subject is in the dissecting-room
it is placed in the lithotomy position for the dissection of the
perineum by the workers on the abdomen. On the fourth day
the student begins the dissection of the back or of the buttock,
according as to whether he has been allotted an upper or a lower
limb.

In removal of the slvin the edge of the knife should be kept How to
directed towards it so as to remove the skin, and no more. The thTskin.
underlying tissue, consisting of the superficial fascia and containing
the cutaneous nerves and bloodvessels and a variable amount
of fat, is to be left behind. Therein the operations of dissection
are the reverse of those of surgery, for the surgeon, in making
a flap, is careful to remove a considerable amount of the subjacent
tissues along with the skin so as to preserve its blood and nerve
supply.

Dissection of the Back. The dissection of the back is under- Time for
taken conjointly by the dissectors of the head and of the upper '^^^^ '°"'
limbs, the former preparing the neck, the latter making ready the
dorsal and lumbar regions. Two days are allowed to the dissector
of the upper limb ; in which time he will examine the fii-st two
layers of the muscles of the back and the associated vessels and
nerves.

Position of the Body. The body lies with the face down-
wards. The trunk is raised l)y l)locks placed beneath the chest
and the pelvis, so that the limits hang over the end and sides of the

D.A. B

DISSECTION OF THE BACK.

dissecting table. The head is to be depressed and fastened with
hooks so as to make tense the neck.

Surface Anatomy. Before commencing the dissection of any
part the student should examine the surface of the body so as to
define the bony and other landmarks by which the surgeon or
physician is guided in his practice. At the upper part of the neck,
posteriorly, in the middle line will be felt the external protuberance
of the occipital bone, and running outwards from this will be found
the superior curved line of the same bone. Passing downwards and
outwards from this to the upper part of the shoulder is a ridge
produced by the outer border of the trapezius muscle.

At the lower part of the neck in the middle line the prominent
spine of the seventh cervical vertebra is readily found, and the
spines of the one or two succeeding dorsal vertebrae. Below this
the spines of the vertebrae can be felt as the fingers are passed down
the furrow in the middle of the back, but the spines are much
obscured by the strong ligaments which pass over and between
them. The furrow is produced by the strong erector spince muscles
which run longitudinally on either side. At the lower end of the
back the series of spines can be traced on to the sacrum, at the
lower part of which they disappear, and the coccyx is then felt
bending forwards at the bottom of the furrow between the two
sides of the buttock. At the side of the back the crest of the ilium
runs outwards on either side, its highest part being on the same
level as the spine of the fourth lumbar vertebra and its posterior
superior spine lying at the Ijottom of a little depression opposite the
second sacral spine. The lower four or five ribs can be felt below
the scapula, and it is to be remembered that the twelfth rib is often
short, and its tip can, in those cases, only be made out by dee]3
pressure at the outer border of the erector spinas muscle, two inches
or so above the iliac crest. The upper angle, the vertebral l)order,
the lower angle, the spine, and acromion process of the scapula,
and the outer part of the clavicle should next be made out,
and the matter will be made easier if the limb be moved about
during the examination. When the limb is placed down beside
the body the upper angle of the scapula is opposite the second
intercostal space, the root of the spine is on a level with the spine
of the third dorsal vertebra, and the lower angle is usually over the
seventh intercostal space. Finally, running upwards to the upper limb
from the side of the body is the fold produced by the latissimus dor si
muscle, which forms the posterior boundary of the armpit, or axilla.

Dissection. The first step is to raise the skin in two flaps by
means of the following incisions : (1) from the spine of the seventh
cervical vertebra along the middle line to the lower end of the
sacrum (fig. 1, a, b and c) ; (2) transversely outwards from the spine
of the seventh cervical vertel)ra to the outer border of the acromion
(fig. 1, a — e) ; (3) upwards and outwards from the last dorsal spine
along the posterior fold of the axilla to the upper limb (fig. 1, A— f) ;
(4) outwards from the lower end of the median incision two- thirds
of the way along the iliac crest (fig. 1, a — g). The two flaps of

CUTANEOUS NEKVES.

skin, one below and the otlier al)Ove incision F, are to be turned
outwards,

A gieat part of the trapezius muscle will be found under the
upper flap, and of the latissimus dorsi under the lower flap.

The reflection of the skin from over the upper part of the
trapezius is performed by the dissector of the head and neck.

The cutaneous nerves should first be sought for in the superficial cutaneoi
fatty layer. They are accompanied by small arteries which will "'^''''^'^ -
guide the student to their position. The nerves vary much in size

A B

Fig. 1. — Plan of the Chief Skin Incisions.

in the difi'erent parts of the Ijack, and their nimiber is also irregular ;
as a general ride, there is one opposite each vertebra except in the
neck.

Over the upper part of the thorax, they will be found near the
spines of the vertebrae, where they lie at first beneath the fat ; but
at the lower part, and in the loins, they issue in a line with the
angles of the ribs.

Cutaneous Nerves. The tegumentary nerves are derived from how
the posterior primary divisions of the spinal nerves, which divide ^"^^
amongst the deep muscles into two branches, inner and outer.
Arteries accompany the greater number of the nerves, bifurcate like
them, and furnish cutiuieous offsets.

B 2

DISSECTION OF THE BACK.

Ill the
dorsal
region.

Ill the
loins.

The student is now concerned with branches of the dorsal and

lumbar nerves. See fig. 2.

Dorsal nerves (D. 1 — 12). These are furnished by both

the inner and outer branches — the upper six or seven from the

inner, and the lower five or six
from the outer. On the surface
they are directed outwards in the
integument over the trapezius and
latissimus dorsi muscles. The upper
nerves perforate the trapezius near
the spines of the vertebrae ; and
the liranch of the second, which is
larger than the rest, extends out-
wards over the scapula. The loioer
nerves pierce the latissimus dorsi
mostly in a line with the angles
of the riljs ; the number of the
superficial offsets from these nerves
often varies.

Lumbar nerves (L. 1 — 3).
In the loins the nerves are derived
from the outer l^ranches of the first
three lumbar nerve trunks ; they
perforate the latissimus dorsi muscle
at the outer l)order of the erector
spinse, and crossing the iliac crest
of the hip-bone, are distributed in
the integuments of the buttock.

First Layer of Muscles (fig. 3).
Two muscles, the trapezius and the
latissimus dorsi, are included in
this layer, and are now to be
cleaned.

Dissection. The superficial
fatty layer and the unimportant
deep fascia are to be removed
together from the trapezius and
latissimus dorsi in the direction of
the fibres of each, viz., from the
shoulder to the spinal column ; and
the upper limb is to be carried
l)ackwards or forwards according

as it may be necessary to put the different portions of the muscles

on the stretch.

Some of the cutaneous nerves and vessels may be^ left in order

that they may be afterwards traced through the muscles to their

origin.
Trapezins: The TRAPEZIUS MUSCLE (fig. 3, a) is triangular in shape, with

the base towards the spine, but the two muscles together have a
origin; trapezoid form. The muscle has an extensive oriyin^ by short

Dissection.

Fig. 2.

-Cutaneous Nerves op
THE Back.

TRAPEZIUS MUSCLE.

tendinous fibres, from the spines of all the dorsal and of the seventh
cervical vertebrae, and their supraspinous ligaments, from the liga-
nientuni iiudiae, and from the inner third of the superior curved

Fig. 3.—

A. Trapezius,

B. Latissimus dorsi.

c. Levator anguli scapulse.
D. Rhomboideus minor.

Muscles of thk Back.

Rhomboideus major.

F. Splenius.

G. Serratus posticus inferior.

On the left side the first layer is shown, and on the right side the second
layer, with part of the third.

line of the occipital bone. From this origin the fibres are directed
outwards, converging to the shoulder, and are inserted into the insertion ;
outer third of the cla^ncle (fig. 5, p. 18), at its posterior aspect,
into the inner border of the acromion, and into the upper border

DISSECTION OV THE BACK.

relations ;

action

in rotation
of bone.

Division
of the
trapezius:

inner part
reflected ;

outer part
reflected.

Spinal
accessorj-
nerve in
trapezius.

Clean parts
beneath :

lieneath the
clavicle ;

of the spine of the scapula as far as an inch from the root of that
process, as well as into a rough prominence on the loAver margin of
the spine near the inner end (fig. 12, p. 32).

The muscle is subcutaneous. The lowest fleshy fibres end in a
small triangular tendon, which glides over the smooth surface at
the root of the spine of the scapula. The upper edge forms the
hinder boundary of the ])Osterior triangular space of the neck. By
its insertion the trapezius corresponds with the origin of the deltoid
muscle, which covers the shoulder.

Action. If all the fibres of the muscle act, the scapula gliding
on the ribs is moved upwards and towards the spinal column ; but
the upper fibres can assist other muscles in elevating, and the lower
fibres will help in depressing that bone.

When the scapula is prevented from gliding on the ribs, the
trapezius imparts a rotatory movement to it by raising the acromion,
and thereby assists in raising the arm above the horiz(jntal when it
has been brought up to that position away from the body by other
muscles.

Dissection. The dissectors of the head and neck and upper
limb will now in their difterent parts divide the trapezius muscle
vertically about two inches from its vertebral attachment, and the
parts will be reflected inwards and outwards respectively. The
inner portion is thin, and after it has been turned up the ligamentum
nuchse from Avhich it arises in the middle line of the neck will be
l)rought into view.

The LIGAMENTUM NUCH^ is a fibrous band, which extends from
the spinous process of the seventh cervical vertebra to the external
occipital protuberance. From its deep surface a thin lamina of
fil)res is sent forwards to be attached to the external occipital crest
and to the spines of the cervical vertel^rse above the seventh, and
thereby a median partition l)etween the muscles of the two sides
of the neck is formed.

Dissection. The stout outer part of the trapezius should be
carefully reflected, and in the somewhat tough subjacent tissue
a large nerve — the spinal accessory — will be found running down-
wards and outwards from the neck on to the deep surface of the
muscle. More or less parallel with the spinal accessory, but below
it, two smaller nerves, from the third and fourth cervical, will then
be made out. Branches of the superficial cervical artery will also
be seen entering the muscle in the same neighl)Ourhood.

The SPINAL ACCESSORY NERVE (the eleventh cranial), having
crossed the posterior triangle of the neck, passes beneath the
trapezius, and forms a plexiform union with the branches of the
third and fourth nerves of the cervical plexus. The nerve can be
followed nearly to the lower border of the muscle.

Dissection. The parts covered by the trapezius will next be cleaned.

The dissector of the neck is responsible for displaying the struc-
tures which lie deeply in the neck beneath the clavicle, but the
worker on the upper limb will take note of them later on. The
parts in question are the posterior belly of the omohyoid muscle

LATISSIMUS DORSI MUSCLE. 7

with the suprascapular nerve and vessels, the transverse cervical
vessels from which the superficial cervical already referred to will
be seen to spring, and the small nerves to the levator anguli
scapulae and rhomboid muscles.

The dissector of the upper limb will find three muscles pro- muscles
ceeding from the vertebral column to the vertebral border of the ll^^^^
scapula, viz., the levator anguli scapulae, the rhomboideus minor scapula,
and major, from above downwards, and these should be cleaned in
the direction of their fibres. The rhomboideus minor and major
muscles are often blended together.

Beneath the lowest part of the reflected trapezius a thin fibrous
lamina (aponeurosis), from which the upj^er part of the latissimus
dorsi muscle takes origin from the lower dorsal spines, will be
revealed, and care should be taken that it is not cut away.

The LA.TISSIMUS DORSI (fig. 3, B) is the widest muscle of the Latissimus

back, and is thin and aponeurotic at its attachment to the spine ^JJ^n f^m
and pelvis. It arises along the middle line from the spinous spine,
processes of the six lower dorsal, all the lumbar, and the upper
sacral vertebrae, as well as from the supraspinous ligaments. On
the outer side it arises from the posterior third of the outer edge of pelvis,
the iliac crest by its aponeurosis, and from the lowest three or four
ribs by as man}' fleshy processes, which interdigitate with slips of ribs ;
the external oblique muscle of the abdomen. And in many bodies
it receives another fleshy slip from the inferior angle of the
scapula. The fibres are directed outwards and upwards, con-
verging rapidly ; and the muscle, much reduced in breadth, turns
round the lower border of the teres major, to be inserted by tendon
into the bottom of the bicipital groove of the humerus (fig. 17, insertion
p. 44), where it will be subsequently seen. humenis-

The muscle is superficial, except at the upper and inner part,
where it is covered to a small extent by the trapezius. Farther
out there is a space between the two, in which the rhomboid and relations ;
infraspinatus muscles appear. The outer border overlaps the
edge of the external oblique muscle of the abdomen in the interval
between the last rib and the iliac crest. The aponeurosis of the
latissimus is in its lower part incorporated in the posterior layer
of the fascia lumborum, of which it forms the chief constituent.

Action. If the arm is hanging loose, the muscle can move it use
behind the back, rotating it inwards at the same time. If the limb nmb^js free
is raised, the latissimus, combining with the large pectoral and teres
muscles, %\'ill depress the humerus.

Supposing the arm fixed, the latissimus assists the pectoralis and fixed,
major in drawing the movable trunk towards the himierus, as in
the act of climbing.

Dissection. The latissimus is to be divided about midway Dissection
between the spines of the vertebrae and the angle of the scapula, {aJ|s1mus.
and the pieces are to be reflected inwards and outwards. In
raising the inner half of the muscle, care must be taken not to
destroy either the thin lower serratus muscle, with which it is
united, or the aponeurosis continued downwards from the serratus.

DISSECTION OF THE BACK.

Parts

beneath
latissimus,

Second

muscular

layer.

Levator
anguli
scapulae :

relations

and use
on scapula,

on the neck.

Rhomboid
muscles.

Small
muscle.

Large
muscle :

origin ;
in.sertion

relations.

In tlie interval between the last rib and the iliac crest the
latissimus is adherent to the aponeurosis of the transversalis
abdominis miLscle, and should not be detached from it.

Parts covered by the latissimus. The latissimus dorsi lies on the
erector spinse, the serratus posticus inferior, the lower ribs with
their intercostal muscles, and the lower angle of the scapula, with
parts of the rhomboideus major, infraspinatus, and teres major
muscles. Nearer the humerus it turns round the teres major, and
is placed in front of that muscle at its insertion. In passing from
the chest to the arm, the latissimus forms part of the posterior
boundary of the axilla.

The Second Layer op Muscles (fig. 3, c, d, e), comprising
the elevator of the angle of the scapula, and the large and small
rhomboid muscles are now to be examined, as well as the posterior
belly of the omohyoid muscle, the suprascapular artery and nerve,
and the transverse cervical artery and its brandies, already referred
to (p. 7).

The LEVATOR ANGULI SCAPULA (fig. 3, c) arises by tendinous
slips from the posterior tubercles of the transverse processes of the
upper four cervical vertebrae. The fibres form an elongated muscle,
which is inserted into the base of the scapula between the spine and
the superior angle (fig. 12, p. 32).

At its origin the levator lies beneath the sterno-mastoid, and, at its
insertion, beneath the trapezius, where it meets the serratus magnus
muscle ; the rest of the muscle appears in the posterior triangular
space of the neck. Beneath it are some of the other cervical muscles,
viz., splenius colli and cervicalis ascendens.

Action. The muscle raises the angle and hinder part of the
scapula, and depresses the acromion ; but in combination with the
upper fibres of the trapezius, which prevent the rotation down of
the acromion, it shrugs the shoulder.

When the shoulder is fixed, the neck can be bent to the side by
the levator.

Rhomboidei MUSCLES. The muscular layer of the rhomboidei
is attached to the base of the scapula, and consists of two pieces,
large and small, which are usually separated by a slight interval.

The RHOMBOIDEUS MINOR (fig. 3, d) is a thin narrow band, which
arises from the spines of the seventh cervical and first dorsal vertebrae,
and the ligamentum nuchee, and is inserted into the base of the
scapula, opposite the smooth surface at the root of the spine (fig. 12).

The RHOMBOIDEUS MAJOR (fig. 3, e) is much larger than the
preceding muscle. It arises from the spines of four or five dorsal
vertebrae below the rhomboideus minor, and from the supraspinous
ligaments ; and its fibres are directed outwards and downwards to be
inserted into the base of the scapula between the spine and the lower
angle (fig. 12). Sometimes the upper fibres are not fixed to the
scapula directly, but end on a tendinous arch passing down the bone.

The rhomboidei are for the most part covered by the tra^^ezius
and latissimus ; but a portion of the larger muscle is subcutaneous
near the scapula.

SCAPULAR VESSELS AND NERVES. 9

Action. From the direction of their fibres both rhomboidei vdW Use by-
draw the base of tlie scapuhi upwards and backwards, so as to
depress the acromion. In combination with the trapezius they with others,
carry the scapula directly back ; and acting with the serratus
magnus, they serve to fix the scapula.

The OMOHYOID MUSCLE consists of two fleshy bellies, anterior Posterior

bellv of

and posterior, which are united by an intervening tendon. Only omohyoid :
the posterior half is now seen.

The muscle arises from the upper border of the scapula behind origin
the notch, and from the ligament converting the notch into a foramen, nation ;
The fibres form a thin, riband-like muscle, which is directed for-
wards across the lower part of the neck, and ends anteriorly in a
tendon beneath the sterno-mastoid muscle. This belly is partly relations,
placed beneath the trapezius, and is partly superficial in the posterior
triangular space of the neck, where it lies above the clavicle and
the subclavian artery, and crosses the l)rachial plexus and the
suprascapular nerve.

Action. The use of the muscle will be considered in the neck.

The SUPRASCAPULAR ARTERY is a branch of the subclavian, and Supra-
is directed outwards through the lower part of the neck to the artery^*^
upper border of the scapula. It runs behind the clavicle, and
crosses the suprascapular ligament in front of the posterior belly of
the omohyoid nuiscle, to enter the supraspinous fossa. Its termi-
nation on the dorsum of the scapula will be seen in the dissection
of the shoulder (p. 38). Before entering the fossa it gives off a
sujjra-acromial branch, which perforates the trajiezius muscle, and offset,
ramifies over the acromion.

The SUPRASCAPULAR NERVE is an offset of the brachial plexus Supra-

scADulsir

(fig. 8, p. 26), and inclines downwards beneath the omohyoid muscle nerve,
to the notch in the upper border of the scapula, through which it
passes into the supraspinous fossa (p. 38).

The TRANSVERSE CERVICAL ARTERY, also a branch of the sub- Transverse

clavian, has the same direction as the suprascapular, towards artery
the upper angle of the scapula, but is higher than the clavicle.
Crossing the upper part of the space in which the subclavian artery
lies, it passes beneath the trapezius, and divides into two branches : divides into
superficial cervical and posterior scapular.

a. The superficial cervical branch is distributed chiefly to the superticiai
under-surface of the trapezius, though it furnishes offsets to the levator
anguli scapulae and the cervical glands.

b. The posterior scapular branch crosses under the levator anguli posterior
scapulae, and descends along the base of the scapula beneath the
rhomboid muscles. When these muscles are divided, the artery

will be seen to furnish branches to them, and to give small anasto-
motic twigs to both surfaces of the scapula. This branch arises
very frequently from the third part of the subclavian trunk as a
separate artery from the superficial cervical.

The suprascapular and transverse cervical veins have the same Accompany-
course and branches as the arteries above described ; they open °
into the external jugular, near its junction with the subclavian vein.

DISSECTION OF THE BACK.

Nerve of
rhomboid
muscles.

Serratus
inagnus
muscle.

Nerve to the rhomboid muscles. This slender offset of the
brachial plexus (fig. 8, p. 26) courses beneath the elevator of the
angle of the scapula, and is distributed to the rhomboidei on their
deep surface. Before its termination it supplies one or two twigs
to the elevator of the scapula.

Dissection. The levator anguli scapulae and the rhomboid
muscles are now to be divided about half-way between their
origin and insertion, and the parts turned inwards and outwards.
The small nerve to the rhomboids will be found running down to
the deep surface of the muscles about an inch to the inner side of
the upper angle of the scapula, and the posterior scapular artery
running close to the vertebral border of the scapula beneath the
rhomboid attachment will be traced out. Finally, the vertebral
border of the scapula will be drawn outwards, the loose connective
tissue space between it and the chest-wall will be opened up, and
the inner surface of the serratus magnus muscle, which is inserted
into the whole length of the inner surface of this border of the
bone, will be cleaned.

DISSECTION OF THE UPPER LIMB.

CHAPTER II.
DISSECTION OF THE AXILLA.

Section I.

The wall of the chest and the axilla, which are described in this Time for
Section, are to be dissected in six days, so that the senior student ^^'•'^•''*'^*^i*'"-
may be free to begin work on the thorax.

Position. The body is lying on the back, the thorax raised to a Position of
convenient height by a block, and the arm, being slightly rotated *^® ^*^^ "
outwards, is to be placed at a right angle with the trunk, a long
l.)oard being passed under the shoulders from side to side for the
support of the arms when they are drawn out from the body.

SuRFACE-MARKiXG. On the front of the chest is seen the pro- Surfece-
minence of the mamma, large in the female, but small and rudi-
mentary in the male, with the nipple projecting from it near the^J*™"^'"^
centre. In the male the nipple is placed most frequently over the "
fourth intercostal space, sometimes over the fifth rib, and occasionally nippip.
at a still higher or lower level. Its position in the female varies
greatly with the development of the mamma.

Between the arm and the chest is the hollow of the axilla, in the Armpit
outer part of which the large vessels and nerves of the limb are
lodged. The extent of this hollow may be seen to vary much with
the position of the limb to the trunk ; for in proportion as the arm
is elevated, the folds l^ounding it in front and behind are carried
upwards and rendered tense, and the depth of the space is dimi-
nished. In this part the skin is of a dark colour, and is furnished
with hairs and large sweat-glands.

If the arm is forcibly raised and moved in different directions, Head of the
while the fingers of one hand are placed in the armpit, the head of "'"^^"•''•
the humerus may be recognised.

On the outer side of the limb is the prominence of the shoulder ; shoulder

3. roll oi Don©

and immediately above it is an osseous arch, which is formed in
front by the clavicle, behind and externally by the spine and the
acromion process of the scapula. Continued downwards from intermus-
about the middle of the clavicle is a slight depression between the ^!!i^I;i^;

or pressions,

pectoral and deltoid muscles, and by pressing the fingers into this
hollow the coracoid process of the scapula can be made out. A
second groove, extending outwards from the sternal end of the

DISSECTION OF THE UPPER LIMB.

Aim : its
prominence
and grooves,

Promi-

around the
elbow-joint.

Reflect skin.

Superficial
fascia.

Deep fascia :

thickest
over axilla.

Cutaneous
nerves :

from cervi-
cal plexus

clavicle, corresponds with the interval between the clavicular and
the sternal origins of the great pectoral muscle.

Along the front of the arm is the prominence of the biceps
muscle ; and on each side of that eminence is a groove, which sub-
sides inferiorly in a dei)ression in front of the elbow-joint. The
groove on the inner side of the biceps is the deeper, and indicates
the position of the brachial vessels.

If the elbow-joint be slightly flexed, the prominences of the
outer and inner condyles of the humerus will be rendered evident,
especially the inner. Below the outer condyle, and separated
from it by a slight interval, the head of the radius is placed, and
may be recognised by rotating that l)one, the fingers at the same
time being placed over the head. At the back of the elbow is the
prominence of the olecranon, and to the outer side of this, when tlie
forearm is fully bent, a projection is formed b>y the capitellum.

Dissection. The first step in the dissection is to raise the skin
from the side of the chest and the armpit, over the great pectoral
muscle and the hollow of the axilla, by means of the following
incisions : — One is to be made along the middle of the sternum
(fig. 1, B. 2). A second is carried along the whole length of clavicle
and continued downwards over the outer side of the shoulder for
about three inches (fig. 1, B. 5). From the lower end of the sternum
a third cut is to be directed outwards over the side of the chest,
as far back as to a level with the posterior fold of the arm})it
(fig. 1, B. 7), and a fourth is taken upwards and outwards from the
lower end of the sternum along the anterior folds of the axilla on to
the arm opposite the lower end of the shoulder cut (fig. 1, B. 6).

The flaps of skin thus marked out are to be reflected outwards
beyond the axilla ; but they should Ije left attached to the bodj', in
order that they may be used for the preservation of the part.

The subcutaneous fatty layer of the thorax resembles the same
structure in other parts of the body ; but in this region it does not
usually contain much fat.

Beneath the subcutaneous layer is the stronger deep fascia, which
closely invests the muscles, and is continuous with the fascia of the
arm. It is thin on the front of the chest, but becomes thick where
it is stretched across the axilla. An incision through it, over the
armpit, will render evident its increased strength in this situation,
and the casing that it gives to the muscles bounding the axilla ; and
if the forefinger be introduced through the opening, some idea will
be gained of its capability of confining an abscess in that hollow.

Dissection. The cutaneous nerves of the side of the chest are
first to be sought. At the spots where they are to be found
they are placed beneath the fat, which must be cut through to
expose them ; and those over the clavicle lie also beneath the super-
ficial platysma muscle. Small vessels for the most part accompany
the nerves, and indicate their position.

Some of the nerves (from the cervical plexus) cross the clavicle
at the middle, and the inner end. Others (anterior cutaneous of the
thorax) appear at the side of the sternum, — one through each inter-

CUTANEOUS NERVES OF CHEST. 18

costal space. And the rest {lateral cutaneous of the thorax) should
be looked for along the side of the chest, about an inch behind the
anterior fold of the axilla, there being one from each intercostal and inter-
space except the first. As these last-mentioned nerves pierce the J^g^A^s •
wall of the thorax, they divide into anterior and posterior branches.
The posterior branches of the highest two of them are larger than
the rest, and are to be followed across the armpit, where a junction

will be found with a l»ranch (nerve of Wrisberg) of the brachial n?rye of
- ^ °^ Wnsberg.

plexus.

Cutaneous nerves from the cervical plexus. These cross Cutaneous
the clavicle and are distributed to the skin over the pectoral muscle, "erviaii'
The most internal branch (sternal) lies near the inner end of the plexus,
bone, and reaches but a short distance below it. Other branches
(clavicular), two or more in number and larger, cross the middle
of the clavicle, and extend to near the lower border of the pectoralis
major ; they join one or more of the anterior cutaneous nerves.

The Cutaneous Nerves of the Thorax are derived from the Cutaneous
trunks of the intercostal nerves between the ribs. Of these there intercostais.
are two sets : — One set, the lateral cutaneous ne?Tfs, . arise about
midway between the spinal column and the sternum. The other
set, the anterior cutaneous nerves, are the terminations of the same
trunks at the anterior ends of the intercostal spaces.

The anterior cutaneous nerves are slender filaments which One near
pierce the pectoral muscle, and are directed outwards to supply the
skin and the mammary gland. The offset of the second nerve joins
a cutaneous l)rancli from the cervical plexus. Small branches of
the internal mammary vessels accompany these nerves.

The LATERAL CUTANEOUS NERVES (fig. 4, p. 15) issue with com- The other

, ,-,,.. ^ ^ -. ^ , ' on side of

panion vessels between the digitations of the serratus magnus the chest ;

muscle, and divide into anterior and posterior branches. There is

not usually any lateral cutaneous nerve from the first intercostal

trunk.

The anterior offsets (fig. 4 ^, p. 15) bend over the pectoral muscle, these have
and end in the integuments and the mammary gland ; they increase ^" ^'°* *^
in size down%vards, and the lowest give twigs to the digitations of
the external oblique muscle. The cutaneous nerve of the second
intercostal trunk commonly wants the anterior oftset.

The ^posterior offsets (fig. 4 8, p. 15) end in the integuments over posterior
the latissimus dorsi muscle and the back of the scapula, and decrease ^^"^ ^^'
in size from above downwards.

The lateral branch of the second intercostal nerve (fig. 4 7 p. 15) One reaches
is larger than the rest, and is named the iritercosto-humeral. Per-
forating the fascia of the axilla, it is distributed to the skin of the
arm (p. 43). As it crosses the axilla it is divided into two or more
pieces, and is connected to the nerve of Wrisberg, or lessei' internal
cutaneous, l)y a filament of variable size.

The branch of the third intercostal nerve gives filaments likewise Third nerve,
to the armpit and the inner side of the arm.

The Mamma is the gland for the secretion of the milk, and is The breast:
situate on the lateral part of the front of the chest.

DISSECTION OF THE UPPER LIMB.

with its
dimensions

Position and
form of the
nipple :

the areola
colour is
variable ;
skin has
glands.

Breast or
the male.

Structure.

Investing

and librous
tissue.

Lactiferous
ducts :

open on end
of nipple.

Muscular
tissue in
nipple.

form and Resting Oil the great pectoral muscle, it is nearly hemispherical ^

position ; jj-^ form, but most prominent at the inner and lower aspects. Its '*
dimensions and weight vary greatly. In a breast not enlarged by
lactation, the width is commonly about four inches. Longitudinally
it extends from the third to the sixth or seventh rib, and trans-
versely from the side of the sternum to the axilla. Its thickness
and weight, is about one inch and a half. The Aveight of the mamma ranges
from six to eight ounces.

Nearly in the centre of the gland (rather to the inner side) rises
the conical or cylindrical projection of the nipple or inamilla.
This prominence is about half an inch or rather more in length, is
slightly turned outwards, and presents in the centre a shallow
depression, where it is rather redder. Around the nipple is a
coloured ring — the areola, about an inch in width, the tint of
which is influenced Ijy the complexion of the body, and Ijecoines
darker during pregnancy and lactation. The skin of the nipple
and areola is provided with numerous papillae and glands ; and on
the surface are some small tubercles marking the position of the
latter.

In the male the mammary gland resembles that of the female in
general form, though it is much less developed ; and it possesses a
small nipple, which is surrounded by an areola provided vc'iVa hairs.
The glandular or secretory structure is imperfect.

Structure. The mamma is a compound racemose gland, and
consists of small vesicles, which are united to form lobules and
lobes, and connected with each lobe is an excretory or lactiferous
duct

A layer of areolar tissue, containing masses of fat, surrounds the
gland, and penetrates into the interior, subdividing it into lobes ;
but between the lobules of the gland, and in the nipjjle and areola,
there is not any fatty substance. Some fibrous septa fix the gland
to the skin, and support it, being spoken of as the ligamenta sus-
pensoria of Astley Cooper.

The ducts issuing from the several lobes (about twenty) are
named from their office galadophorous ; they converge to the areola,
where they swell into oblong dilatations or reservoirs (sinuses) of
one-sixth to one-third of an inch in width. Onwards from that
spot the ducts become narrower ; and, surrounded by areolar
tissue and vessels, they are continued through the nipple, nearly
parallel . to one another, to open on the summit by apertures
smaller than the canals, and varying from the size of a bristle to
that of a common pin.

Nipple. The substance of the nipple is composed in great part of
a network of interlacing bundles of plain muscular tissue, through
which the lactiferous ducts pass to the surface. Some of the
bundles extend from base to apex of the nipple ; and surrounding
the base is a set of circular fi1)res, with which radiating Inmdles
decussate.

Arteries of Blood-vessels. — The arterics^XQ supplied by tlie axillary, internal mammary,
lie gland ^„^j intercostal, and enter both surfaces of the gland. The veins end

THE MAMMA.

principally in the axillary and internal mammary trunks ; but others enter and veins,
the intercostal veins.

The nerves are supplied from the anterior and lateral cutaneous branches Xerves.
of the thorax, viz., from the third, fourth, and fifth intercostal nerves.

The lymphatics of the inner side open into the sternal glands ; those of Lymphatics,
the outer side pass to the axillary glands.

Fig. 4. — View of the Dissected Axilla. (Illustrations of Dissections).

Muscles :

Pectoralis major.
Pectoralis minor.
Serratus magnus.
Latissimus doi-si.
Teres major.
Subscapularis.
Coraco-bi-achialis.
Biceps.

Vessels :

a. Axillary artery.

b. Axillary vein.

c. Subscapular vein.

d. Subscapular artery.

e. Posterior circumflex artery.

Nerves:

1. Median.

2. Internal cutaneous.

3. Ulnar.

4. Musculo-spiral.

5. Nerve of Wrisberg.

6. Internal cutaneous of musculo-

spiral.

7. Intercosto-humeral.

Q T>«c4.^,.:„,. ( branches of lateral

8. Posterior ) . r .i

f. . , . < cutaneous of the

9. Anterior ) ^j^^^^^

Dissection (fig. 4). With the limb drawn outwards (abducted) Dissection
from the trunk, the student should now remove the fascia and the muSe!*'^
fat from the surface of the great pectoral muscle. In cleaning the
muscle the scalpel should be carried in the direction of the fibres,
viz. from the aini to the thorax ; and the dissection may be begun

DISSECTION OF THE UPPER LIMB.

Remove fat
of axilla.

Follow
vessels.

at the lower border on the right side, but at the upper border ou
the left side. In the groove at the upper border, between the
pectoralis major and the deltoid, a small vein, the cephalic^
will be seen, and subjacent to this a small artery, the descending
01- humeral branch of the acromio-thoracic, will be found running
downwards.

The fascia and the fat are then to be taken from the axilla,
without injury to the numerous vessels, nerves, and glands in the
space. The dissection will be best executed by cleaning first the
large axillary vessels at the outer part, where these are about to
enter the arm, and then following their branches which are
directed to the chest, viz., the long thoracic under cover of the
anterior boundary of the armpit, and the subscapular along the
posterior boundary. With the latter vessels the middle and lower
subscapular nerves will be found, and just below them at their
origin, turning backwards near the humerus, are the posterior
circumflex artery and the circumflex nerve. Some arterial twigs
entering the axillary glands should also l)e traced out.

In taking away the fascia and fat from the muscles at the back
of the space, the small internal cutaneous branch of the musculo-
spiral nerve (fig. 4^) should be looked for near the great vessels.
Trace nerves The nerves of the brachial plexus about the axillary vessels in
of plexus, ^i^g outer part of the space are then to be defined. The smallest of
these, which is commonly destroyed, is the nerve of Wrisberg ; it
lies close to the hinder edge of the axillary vein, and joins with the
intercosto-humeral nerve,
and on inner Finally, when cleaning the serratus magnus muscle on the ribs,
the student will seek on its surface for the posterior or long
thoracic nerve (fig. 6 **, p. 21) which runs down longitudinally
towards the back part of the muscle. The posterior offsets of the
intercostal nerves crossing the axilla will also Ije cleaned.

Clean back
of space.

wall.

THE AXILLA.

Situation
and foiin of
the armpit.

Boundaries

anterior
wall :

l)Osterior
wall.

The axilla is the hollow between the arm and the chest (fig. 4).
It is somewhat pyramidal in form, with its apex directed upwards
to the root of the neck. The space is larger near the thorax than
at the arm, and its boundaries are as follows : —

Boimdaries. In front and l)ehind, the si)ace is limited by the
muscles passing from the trunk to the upper limb. In the anterior
wall are the two pectoral muscles, but these take unequal shares in
its construction : the pectoralis major (a"^) extends over the whole
front of the space, reaching from the clavicle to the edge of the
anterior fold ; while the pectoralis minor (b) corresponds only to
about the middle third of the wall.

In the posterior wall, from above downwards, lie the sub-

scapidaris (p), the latissimus dorsi muscle (d), and the teres major (e)

muscles. The free margin of this wall, or the posterior fold, is

formed by the latissimus dorsi and teres major muscles, and is

* The letters and figures refer to fig. 4.

CONTENTS OF AXILLA. 17

thicker and more prominent than the anterior, especially near
the arm.

On the inner wall of the axilla lie the first five ribs, mth their inner wall ;
intervening intercostal muscles, and the part of the serratus magnus
(c) taking origin from those bones. On the outer side the space outer wall ;
has but small dimensions, and is limited by the humerus and the
coraco-brachialis and biceps muscles (g and h).

The apex of the hollow is situate between the clavicle, the upper apex ;
margin of the scapula, and the first rib ; and the forefinger may be
introduced into the space for the purpose of ascertaining the upper
Itoundaries, and the depth. The base of the pyramidal fossa is base.
turned downwards, and is closed by the thick aponeurosis reaching
from the anterior to the posterior fold.

Contents of the space. In the axilla are contained the axillary contents of
vessels and the brachial plexus of nerves with their branches ; ^^® space,
some branches of the intercostal nerves ; together w^th lymphatic
glands, and a large quantity of loose areolar tissue and fat.

Position of the trunks of vessels and nerves (fig. 4). The large Position of
'xiilary artery (a) and vein (b) cross the outer portion of the^fg^jg.

ice in passing from the neck to the upper limb. The part
or each vessel now seen lies close to the humerus, reaching
beyond the line of the anterior fold of the armpit, and is
covered only by the common superficial coverings, viz., the skin,
the fatty layer or superficial fascia, and the deep fascia. Behind
the vessels are the subscapularis (f) and the tendons of the latis-
simus and teres muscles (d and e). To their outer side is the
coraco-brachialis muscle (g).

On looking into the space from below, the axillary vein (6) lies vein ;
on the thoracic side of the artery.

After the vein has been drawn aside, the artery will be seen to nerves,
lie amongst the large nerves of the upper limb, having the median
trunk (1) to the front and outer side, and the ulnar (3) and the
small nerve of Wrisl^erg (^) to the inner side, the internal cutane-
ous (2) to the inner side and somewhat in front, and the musculo-
spiral (*) and circumflex nerves beneath it. This part of the artery

\'es l)ranches to the side of the chest and the shoulder. The vein

;eives some branches in this spot.

Position of the branches of vessels and nerves. The several branches Situation of
of the vessels and nerves have the undermentioned position with ^^^^"ches :
ifspect to the boundaries of the axilla.

Close to the anterior fold, and concealed by it, the long thoracic in front ;
artery rmis to the side of the chest. Taking the same direction,
though nearer the middle of the hollow, a small external mammary
artery and vein are occasionally present.

Passing down the posterior wall, within the free margin of the behind ;
fold in contact with the lower edge of the subscapularis muscle,
are the subscapular vessels and nerves (d) ; and near the outer,
humeral, end of the subscapularis the posterior circumflex vessels (e)
and the circumflex nerve bend backwards beneath the large
trunks.

D.A. C

DISSECTION OP THE UPPER LIMB.

inside.

Lymphatic
glands
of the
axilla

and vessels

joining

them.

On the inner boundary, at the npper part, are a few small
branches of the superior thoracic artery, which ramify on the
serratus muscle ; but these are commonly so unimportant, that
this part of the axillary space may be considered free from vessels
with respect to any surgical operation. Eunning down the outer
surface of the serratus magnus towards the back of the axilla is
the nerve to that muscle (long or posterior thoracic) ; and coming
through the inner wall of the space, under cover of the pectoral
muscles, are the lateral cutaneous nerves of the thorax, the
highest of which is directed across the axilla to the arm, and
receives the name intercosto-humeral (7).

The lymphatic glands of the axilla are arranged in three sets :
one is placed along the inner side of the great blood-vessels ;
another occupies the hinder part of the space, lying near the sub-
scapular vessels ; and the third accompanies the long thoracic
artery, beneath the margin of the pectoralis major. Commonly
there are in all ten or twelve ; but in number and size they vary
nmch. Small twigs from the branches of the axillary vessels are
furnished to them.

The glands by the side of the blood-vessels receive the lymphatics
of the arm ; those along the hinder boundary are joined by the

ORALIS

Fig. 5. — The Clavicle, showing the Upper and a Part
OP THE Anterior Surface.

Pectoralis
major ;

ongms ;

insertion ;

relations.

lymphatics of the side of the chest and of the back, and those
beneath the pectoral muscle by the lymphatics of the front of the
chest, and from the outer part of the mamma. The efferent
vessels unite to form a trunk, which opens into the lymphatic duct
of the neck of the same side ; or some may enter separately the
subclavian vein.

The PECTORALIS MAJOR (a) is triangular in shape, with the base
at the sternmn, and the apex at the arjn. It arises from the inner
half of the front of the clavicle (fig. 5), from the anterior surface of
the sternum and the cartilages of the upper six ribs, and below
from the aponeurosis of the external oblique muscle of the abdomen.
From this wide origin the fibres take different directions — those
from the clavicle l^eing inclined obliquely downwards, while the
lower ones ascend behind the upper portion of the muscle ; and all
end in a tendon, which is inserted (fig. 17, p. 44) into the pectoral
ridge on the outer side of the bicipital groove of the humerus, along
which a thin prolongation is sent upwards to the head of the bone.

This muscle bounds the axilla in front, and its lower border

PECTORALTS MAJOR. 19

forms the anterior fold of the hollow. Covering it are the integu-
ments, with the mamma and the thin deep fascia, as well as the
platysma close to the clavicle. The upper border is adjacent to the
deltoid muscle, the cephalic vein, and a small artery lying between
the two. Between the cla\dcular and sternal origins is a narrow
interval, which corresponds to a depression on the surface. The
parts beneath the pectoralis major will be seen subsequently.

Action. If the humerus is hanging, the muscle will move Use: flexes,
forwards the limb until the elljow reaches the front of the trunk, ^^^^^^ »">
and will rotate it inwards.

When the limb is raised, the pectoralis depresses and adducts it and adducts
(draws it to the side of the body) ; and acting with other muscles ^'^"^ '
inserted into the humerus, it may dislocate the head of that bone
when the lower end is raised and fixed, as in a fall on the elbow.

Supposing both limbs fixed, as in climbing, the trunk will be raises ribs,
raised by both muscles ; and the lower fibres can elevate the ribs
in lal)orious breathing.

Dissection (figs. 6 and 7). The great pectoral muscle is to be cut Dissection.
across now in the following manner : —

Divide the clavicular part of the muscle and find the subjacent Cut clavi-
branches of nerve and artery. In reflecting the cut piece of the Sf the^^**
muscle, press the limb against the edge of the table, for the Pectoral,
purpose of raising the clavicle and rendering tight the fascia
attached to that bone. Carefully remove the fat, and a piece of
fascia prolonged from the upper border of the small pectoral muscle,
(the membranous costo-coracoid sheath) will be seen close to the
clavicle, covering the axillary vessels and nerves.

The cephalic vein is to be defined as it crosses inwards to the Trace
axillary vein. A branch of a nerve (the external anterior thoracic), nerS^'^'^
and the acromio-thoracic vessels, perforate the fascia over the axillary
trunks, and are to be followed to the clavicular part of the pectoral
muscle. A second branch of the external anterior thoracic nerve,
with accompanying arteries, will be found passing downwards over
the upper border of the pectoralis minor into the sternal part of the
major muscle. These nerves and arteries should now be cleaned.

The remaining part of the pectoralis major may then be cut about Divide the
its centre, and the pieces thrown inwards and outwards. Any fat muscie.^'^^
coming into view is to be removed ; and the tendon of the pectoralis
is to be followed to the humerus. In raising the pectoralis major
note will l)e taken of a small nerve (internal anterior thoracic),
which usually pierces the minor muscle to enter the lower part of
the major.

Insertion of the pectoralis major. The tendon of the pectoralis Tendon of
consists of two layers, anterior and posterior, at its attachment to ^^^ ^^ '^'
the bone ; — the anterior receives the clavicular and upper sternal
fibres ; and the posterior gives attachment to the lower ascending
thoracic fibres. The tendon is from two inches to two inches and a
half wide, and sends upwards one expansion over the bicipital
groove to the capsule of the shoulder-joint, and another downwards
to the fascia of the arm (see humerus, fig. 17, p. 44).

C 2

DISSECTION OF THE UPPER LIMB.

Parts

covered by
the muscle,

Pectoral is
minor :

origin ;
insertion

relations :

Dissection
of axillary
sheath and
costo-co-
racoid
fascia.

Costo-cora-
coid mem-
brane

conceals
siibclavius,

and joins
sheath of

vessels.

Axillary
sheath

strongest in
front.

Clean the
vessels.

Paris covered by the pedoralis. The great pectoral muscle covers
the pectoralis minor, and forms alone, above and below that muscle,
the anterior boundary of the axilla. Between the pectoralis minor
and the clavicle it conceals the subclavius muscle, the sheath con-
taining the axillary vessels, and the branches perforating that sheath.
Below the pectoralis minor it lies on the side of the chest, on the
axillary vessels and nerves, and on the bicef)s and coraco-brachialis
muscles near the humerus.

The PECTORALIS MixoR (figs. 6 and 7) is also triangular in
shape, and extends from the thorax to the shoulder. It arises
from the third, fourth, and fifth ribs, immediately external to their
cartilages, by tendinous slips which are blended with the ajDoneuroses
in the intercostal spaces. The fibres converge to their insertion into
the anterior half of the coracoid process of the scapula, at its upper
and inner part (fig. 10, p. 29).

This muscle assists the pectoralis major in forming the anterior
wall of the axilla, and near its insertion it lies over the large vessels
and the accompanying nerves. The upper border is separated from
the clavicle by a triangular interval. The lower border projects
beyond the pectoralis major close to the chest ; and along it the long
thoracic vessels lie. The tendon of insertion is united with the
coraco-brachialis and short head of the biceps.

Action. It draws the scapula forwards and downwards ; and in
laborious breathing it becomes an inspiratory muscle, taking its fixed
point at the shoulder.

Dissection. Supposing the clavicle raised by pressing back-
wards the arm, as before directed, the tube of fascia around the
axillary vessels will be demonstrated by making a transverse cut
below the costo-coracoid membrane so that the handle of the
scalpel can be passed beneath it. Then, by dividing the mem-
brane itself near the clavicle and raising the lower border of the
subclavius, this muscle will be seen to be encased by fascia, which is
attached to the bone both before and behind it.

The costo-coracoid membrane or ligament is a firm band which
is attached on the inner side to the first rib, and on the outer
side to the coracoid process of the scapula. Between these points it
is inserted into the under-surface of the clavicle, enclosing the sub-
clavius muscle (fig. 6 d). The fascia that encases the small pectoral
muscle is joined to the membrane above, and, in addition, the deep
stratum of the membrane, beneath the subclavius muscle, is blended
with the front of the axillary sheath.

The sheatli of the axillary vessels and nerves (e)* is a funnel-
shaped tube, prolonged from the fascia covering the scaleni muscles
in the lower part of the neck. It is strongest near the subclavius
muscle, where the costo-coracoid band joins it. The anterior part
of the sheath is perforated by the cephalic vein (e), the acromio-
thoracic artery (a), and the anterior thoracic nerves (l and 2).

Dissection. After the costo-coracoid membrane has been ex-

The letters and figuies refer to fig 6. In fig. 7 the parts are named.

THE SUBCLAVIUS.

aiuineJ, the remains of it are to be taken away ; and the subclavius
muscle, and the axillary vessels and nerves_^witli their branches, are
to be carefidJy cleaned.

The SUBCLAVIUS (fig. 6, d) is a small elongated muscle, placed subcianus

muscle

Fig. 6.

-Second View of the Disskctiok of the Chest
(Illustrations of Dissectioks).

Muscles andfascke :

Long thoracic branch.

Pectoralis major, cut.
Pectoralis minor.

Subscapular branch.

Axillary artery.

Serratus magnus.

€.

Cephalic vein.

1).

Subclavius, encased iu the

Brachial veins joining the

costo-coracoid membrane.

axillary vein, g.

Axillary sheath.

Subscapularis.

Latissimus doi-si.

Nerves :

Teres major.
Coraco-brachialis.

and 2. Anterior thoracic

Biceps.

brauches.
Long subscapular branch.

Vessels :

Nerve to the serratus.

Acromio-thoracic branch.

Intercosto-bumeral.

below the clavicle. It arises l»y a tendon from the fii-st rib and its

cartilage at their junction, in front of the costo-clavicular ligament.

The fibres pass outwards and somewhat upwards, and are inserted

into a groove on the under- surface of the clavicle, which reaches is attached

to clavicle

DISSECTION OF THE UPPER LIMB.

and first rib
relations ;

AXILLARY
ARTERY :

extent ;

depth.

above small
pectoral ;

with
muscles,

and nerves.

Beneath
pectoral

with
muscles,

and nerves.

And beyond
the small
pectoral :
with
muscles,

with vein,
and ner^'es.

between the two rough impressions for the costo- and coraco-
claviciilar ligaments.

The muscle crosses the large vessels and nerves of the limh, and
is enclosed, as before said, in a sheath of fascia.

Action. It depresses the clavicle, and indirectly the scapula.

The AXILLARY ARTERY (figs. 6 and 7) continues the subclavian
trunk to the upper limb. The part of the vessel to which this name
is applied is contained in the axilla, and extends from the
outer border of the first rib to the lower edge of the teres
major muscle (h).

In the axillary space its position will be marked by a line from
the centre of the clavicle to the inner edge of the coraco-1 )rachialis.
Its direction will vary with the position of the limb to the trunk ;
for when the arm lies by the side of the body the vessel is arched,
its convexity being upwards ; but when the limb is raised to the
level of the shoulder, it is somewhat curved in the opposite direc-
tion. In the upper part of the axilla the vessel is deeply placed,
but it becomes superficial as it approaches the arm.

Its relations with the surrounding objects are numerous ; and the
description of these will be methodised by dividing the artery into
three -parts, the first above, the second beneath, and the third below
the small pectoral muscle.

Above the small pectoral muscle, the artery is contained in the
axillary sheath of membrane (e), and is concealed by the clavicular
portion of the great pectoral muscle. Behind it are the intercostal
muscles of the first space and the first digitation of the serratus
magnus.

To the thoracic side is placed the axillary vein (^). The cephalic
vein (e) and offsets of the acromio-thoracic vessels cross over it.

On the acromial side lie the cords of the brachial plexus ; super-
ficial to it is the external anterior thoracic nerve ; and beneath it is
the posterior or long thoracic, descending on the serratus magnus.

In its second part, the pectoralis minor and major (b and a) are
superficial to the artery. But there is not any muscle immediately
in contact behind, for the vessel is placed across the top of the
axilla, particularly when the limb is in the position required by the
dissection.

The companion vein (g) lies to the inner side, but separated from
the arterial trunk Tjy the inner cord of the l)rachial plexus, which
has crossed behind the artery to its inner side.

In this position the cords of the brachial plexus lie around it,
one being outside, another inside, and the third behind the artery.

Beyond the pectwalis minor, the artery is at first concealed by
the lower border of the great pectoral muscle (a) ; but thence to its
termination it is covered only by the integuments and the fascia.
Beneath it are subscapularis muscle (f) and the tendons of the
latissimus and teres (g and h). To the outer side is the coraco-
brachialis muscle (j).

The axillary vein remains on the thoracic side of the artery.

In this, its third part, the artery lies in the midst of the large

AXILLARY ARTERY.

trunks of nerves into which the brachial plexus has l)een resolved.
On the outer side is the median nerve, with the niusculo-cutaneous
for a short distance ; and on the inner side are the ulnar and the
nerve of Wrisberg (lesser internal cutaneous), the latter being
directed behind, or sometimes through, the vein to its inner side.
Superficial to the vessel is the internal cutaneous and the inner
head of the median passing outwards ; and behind are the musculo-
spiral and circumflex nerves, the latter extending only as far as the
border of the subscapular muscle.

The BRANCHES of the axillary artery are furnished to the wall of Branches.
the thorax and the shoulder. The thoracic branches are, as a rule,
four in nmnber ; two (superior and acronuo-thoracic) arise from the

External anterior thoracic nerve.

Cephalic vein
-Musculo-cutaneous nerve.

Anterior circumflex
arter\-.

Posterior circumflex
arterj'.
Coraco brachialis.

Internal
cutaneous nerve.
Subscapular
artery
Intercosto-
hiuneral nerve.
Median nerve.

Ulnar nerve.
Teres major.

Brachial

plexus.

Axillary
artery.

Axillary vein.

Thoracic axis.

Long subscapu.
lar nerve.
Lowest sub-
scapular nerve.
Internal ante-
rior thoracic
nerve.

Long thoracic
artery.

major.
Serratns magnus,

Fig.

-Parts beneath the Pectoralis Major (Diagrammatic).

artery above the pectoralis minor, one (alar thoracic) beneath that
muscle, and one (long, or inferior, thoracic) at its lower border.
Three branches are supplied to the shoulder, viz., subscapular and
two circumflex ; they arise close together, at the border of the
subscapularis muscle. Occasionally a . small external mammary
artery is present.

The superior tJwracic branch is the highest and smallest offset, and Upper
arises opposite the first intercostal space ; it ramifies on the side of
the chest, anastomosing with the intercostal arteries. Very com-
monly this vessel arises with the acromio-thoracic, and the trunk of
origin is then spoken of as the thoracic axis (fig. 7).

The acromio-thoracic branch is a short trunk on the front Acromio-
thoracic

DISSECTION OF THE UPPER LIMB.

offsets are
internal,

external,

ascending,

and de-
scending.

Alar tho-
racic.

Long tho-
racic.

External
mammary.

Subscapular

dorsal
branch,

which give

infra-

scajjular.

Anterior
and

posterior
circumflex.

Muscular.

Axillary
vein:

of the artery, which appears at the upper border of the pecto-
ralis minor, and opposite the interval between the large pectoral
and deltoid muscles. Its principal offsets are directed inwards and
outwards : —

a. The inner or thoracic set supply the pectoral muscles, and give
a few offsets to the side of the chest, which anastomose with the
intercostal and other thoracic arteries.

h. The outer or acromial set enter the deltoid, and some twigs
perforate that muscle to anastomose over the acromion with a branch
of the suprascapular artery.

c. A small clavicular branch ascends to the subclavius muscle.

d. The humeral branch runs downwards with the cephalic vein
between the pectoral and deltoid muscles, to which it is distributed.

The alar thoracic is very inconstant as a separate branch, its place
being frequently taken by offsets of the subscapular and long
thoracic arteries ; it is distril)uted to the glands and fat of the
axilla.

The long thoracic branch is directed along the border of the
pectoralis minor to about the fifth intercostal space ; it supplies
the pectoral and serratus muscles, and anastomoses, like the other
branches, with the intercostal and thoracic arteries. In the female
it gives branches to the mammary gland.

An external mammary artery is frequently met with, especially in
the female ; its position is near the ndddle of the axilla with a
companion vein. It supplies the glands, and ends in the wall of
the thorax l^elow the long thoracic.

The subscapular branch courses with a nerve of the same name
along the subscapularis muscle, just within the fold of the
latissimus dorsi, as far as the lower angle of the scapula, where
it ends in branches for the serratus niagnus, latissimus dorsi,
and teres major muscles. It also gives many off-sets to the
glands of the space.

Near its origin the artery sends backwards a considerable dorsal
branch round the lower border of the subscapular muscle, which
gives an infrascapular offset to the ventral aspect of the scapula, and
then turns to the dorsum of that bone, where it will be afterwards
dissected (p. 38).

The subscapular artery is frequently combined at its origin with
other branches of the axillary, or with branches of the brachial
artery.

The circumflex branches wind round the humerus below the sub-
scapular muscle. The anterior is small, and passes outwards beneath
the coraco-brachialis and l)iceps, and should be looked for by draw-
ing the axillary artery a little away from the coraco-brachialis
muscle. The -posterior is much larger, and disappears with the
companion nerve between the subscapularis and teres major muscles.
They will be followed in the dissection of the shoulder.

Small muscular offsets enter the coraco-brachialis muscle.

The AXILLARY VEIN {g) continues upwards the basilic vein of
the arm, and has the same extent as the axillarv arterv. It lies to

BRACHIAL PLEXUS. 25

the thoracic side of its artery, and receives corresponding thoracic exteutand
and shoulder branches. Opposite the suljscapiilar muscle it is relations;
joined externally by a large vein, which is formed by the im^ion of ^"^''^•^•
the vense comites of the brachial artery ; and near the cla\icle the
cephalic vein opens into it.

Dissection. The continuity of the axillary with the suljclavian Dissection
artery will now be displayed by removing the middle third of the pfexm*!**'*^
clavicle and the sul>jacent portion of the subcla^^us muscle and
cleaning the vessel Ijeneath the bone. After this the dissector will
follow out the branches of the brachial plexus, cut through the
pectoralis minor near its insertion into the coracoid process, and
turn it towards the chest, but ^v^thout injuring the thoracic nerves.
The axillary vessels are next to be ligatured, di\ided below the
second rib above the ligature, and to be drawn down with hooks,
care l>eing taken to preserve the loop of communication l)etween
the external and the internal anterior thoracic nerves ; and their
tlioracic branches may be removed at the same time. A dense
fascia is to be cleared away from the large nerves of the plexus.

The BRACHIAL PLEXUS (figs. 7 and 8) results from the interlace- Xerves
ment of the anterior branches of the lower four cerWcal nerves and ^^S
the larger part of the first dorsal ; and a slip is added to it alx)ve plexus,
from the fourth cervical nerve. It is placed successively in the its situation
neck and the axilla, and ends opposite the coracoid process in the
nerves of the limb. The part of the plexus alx)ve the clavicle is
described in the dissection of the head and neck. The part and reia-
below the claWcle has the same relations to surrounding musclas **°°^'

the axillary artery ; and in it the nerve-trunks are disposed as
•Hows :- —

As the plexus enters the axilla it consists of three cords, inner, The nerves

outer, and posterior, which lie together in a bundle on the outer cords

side of the artery. Beneath the pectoralis minor the three cords around the

art6rv

embrace the vessel, being placed as their names indicate — the fii-st
inside, the second outside, and the third behind the artery. Near
the lower edge of the small pectoral muscle, the cords divide to
form the large nerves of the limb.

The branches of the plexus below the clavicle arise from the branches:
several cords in the following way (fig. 8) : —

The outer cord furnishes one anterior thoracic branch (eat), the outer cord ;
musculo-cutaneous (mc), and the outer head of the median nerve (m).

The inner cord gives origin to a second anterior thoracic nerve inner cord ;
(iat), the internal cutaneous (ic), the nerve of Wrisberg (w), the
inner head of the median (m), and the ulnar nerve (u).

The posterior cord furnishes the subscapular branches (si, s2, and po^rior
s3), and ends in the circumflex (c) and musculo-spiral (ms) trunks.

Onlv the thoracic and subscapular nerves are exposed to their The follow-

. '^ . , ^ . . Mil • i-L ^^S ai'e seen

termination at present ; the remaining nerves will be seen in the now, ^iz.—
subsequent dissections.

The anterior thoracic branches (fig. 6, ^ and 2, p. 21, and fig. 7, two anterior
p. 23), two in number, are named outer and inner, like the cords °'**^*^*
from which thev come.

DISSECTION OF THE UPPER LIMB.

Fia. 8. DlAORAM OP THE BRACHIAL PlEXUS. ThE DOTTED LINK INDICATES

THE LEVEL AT WHICH THE CORDS ARE CROSSED BY THE CLAVICLE.

c IV. to c. VIII. Fourth to eighth
cervical nerves.

D I. and D II. First and second
dorsal nerves.

1 i and 2 i. First and second inter-
costal nerves.

ih. Intercosto-hunieral nerve.

phr. Phrenic nerve.

Supradavimlar branches of brachial
plexus :

rh. Branch to rhomboids,
sps. Suprascapular,
sc. Branch to subclavius.
pt. Posterior thoracic.

Infraclavicular h'ancJies :

From outer cord —
eat. External anterior thoracic,
mc. Musculo-cutaneous.
m. Median.

From inner cord —
iat. Internal anterior thoracic,
w. Nerve of Wrisberg.
ic. Internal cutaneous,
u. Ulnar,
m. Median.

From posterior cord —
s 1. Upper.
s 2. Middle,
s 3. Lower subscapular,
c. Circumflex,
ms. Musculo-spiral.

BRACHIAL PLEXUS

Tlie outer nerve crosses over the axillary artery, to the under-
surface of the great pectoral luuscle in which it ends. On the
inner side of the vessel it communicates with the following branch.

The inner nerve comes forwards l)etween the artery and vein, and
after receiving the offset from the outer, ends in many branches to
the under-surfjice of the pectoralis minor. Some twigs enter the
great pectoral muscle after passing either through the pectoralis
minor or above its 1x)rder.

The subscapular nerves are three in number, and supply the
muscles bounding the axilla behind : —

The 2tpper turve is the smallest, and enters the upper part of the
subscfipularis muscle.

The middk or long subscapular nerve accompanies the subscapular
artery along the posterior wall of the axilla, and supplies the
latissimus dorsi muscle (fig. 7).

The lower subscapular nerve gives a branch to the lower i)art of
the subscapularis muscle,
and ends in the teres
major.

Another branch of the
plexus, the posterioi' or
long tharacic nerve or
7ierve to the serratus, lies
on the inner side of the
axilla (fig. 6, *). It arises
al)ove the clavicle from
the fifth, sixth, and
seventh cervical nerves
fig. 8, pt), and descends
behind the axillary ves-
sels to reach the outer
surface of the serratus
magnus miLscle.

The LATISSIMUS DORSI

MUSCLE (fig. 7) may be
examined as far as it
enters into the posterior
wall of the axilla. Arising from the Ijack of the trunk (p. 7),
and crossing the lower angle of the scapula, the muscle ascends
to be inserted into the bottom of the bicipital groove, by a tendon
one inch and a half in width, in front of the teres major ; at
the lower border aponeurotic fibres connect the two, but a bursa
intervenes between them near the insertion (fig. 17, p. 44).

Dissection. To lay bare the serratus magnus, the arm is to be
drawn from the trunk, so as to separate the scapula from the thorax.
The nerves of the brachial plexus should be included in a ligature
so as to hold them together, and cut through opposite the third rib ;
and the fat and connective tissue should be cleaned from the
muscular fibres.

The SERRATUS MAGNUS MUSCLE (fig. 9) extends from the side

and iuner.

Three sub-
scapular :

to subsca-
pularis,

latissimus
dorsi,

and teres
major.

Fig. 9. — The Serratus Magnus.

insertion.

Dissection
of the ser-
ratus.

Serratus
magnus :

DISSECTION OF THE UPPER LIMB.

origin

three parts
the muscle ;

relations ;

of the chest to the base of the scapula, and clothes the inner wall
of the axilla. It arises from the upper eight or nine ribs by as
many slips or digitations, and passes backwards, diminishing in
breadth, to be inserted into the whole length of the l)ase of the
scapula on the ventral aspect. From a difference in the arrangement
of the slips, the muscle is divided into three parts ; —

The wpjper part is formed by the first digitation, which is thicker
than the others, and springs from the first and second ribs, as well
as from a tendinous arch between them : it is inserted into an
impression in front of the upper angle of the scapula. The middle
part is thin, and comprises two digitations, which spread out from
the second and third ribs to the vertebral border of the scapula.
The loiver part is the strongest, and consists of the remaining five
or six slips, which converge from their ribs (fourth to eighth or
ninth) to a special surface on the ventral aspect of the lower angle
of the scapula.

The serratus is in great part concealed by the pectoral muscles,
the axillary vessels and nerves, and the scapula, with the subscapu-
laris and latissimus dorsi muscles. Its deep surface rests against
the ribs and the intercostal muscles. The lower slips interdigitate
with like processes of the external oblique muscle.

Action. The whole muscle acting, the scapula is carried forwards.
But the lower jmrt can move forwards the lower angle alone, so as
to rotate the bone, and turn the glenoid cavity upwards as in
raising the arm above the level of the slioulder. The lowest slips
may evert the ribs in forced inspiration.

Removal of the limb. The limb is now to be drawn aAvay
from the side of the body and removed by cutting through the
serratus magnus muscle about an inch from its insertion into the
vertebral border of the scapula, by dividing the omohyoid muscle
and the suprascapular vessels and nerves near the upper border of
the bone and the latissimus dorsi near the lower angle. The
ligatures embracing the axillary vessels and the nerves of the
brachial plexus should be fixed to the outer fragment of the clavicle
or to the subjacent soft parts, so as to retain them approximately in
their position.

Position.

Dissection
of muscles.

Section II.

SCAPULAR MUSCLES, VESSELS, NERVES, AND LIGAMENTS.

Position. After the limb has been separated from the trunk it
is to be placed with the subscapularis uppermost.

Dissection. The different muscles that have been traced to the
scapula in the dissection of the front of the chest and of the back
are now to be followed to their insertion into the bone. A small
part of each, about an inch in length, should be left for the pur-
pose of showing the attachment.

Fig. 10 shows the attachments of the muscles to the ventral
surface of the bone, and fig. 12 (p. 32) to the dorsal surface.

SC A POLAR MUSCLES.

Between the larger rhomboid muscle and the serratus magnus, at
the base, or vertebral border, of the scapula, run the posterior
scapular artery and vein, the ramifications of which are to be
traced.

To the borders and the angles of the scapula the following Muscles
muscles are connected : — attached

From the upper margin of the scapula arises one muscle, the to upper
omohyoid (fig. 11, e). About half an inch wide at its origin, the SS^SpJla,
muscle is attached to the edge of the bone behind the notch, and
sometimes to the ligament which bridges over the notch.

Along the ajcillary margin arise the long head of the triceps to axillary
(fig. 22, A, p. 51), and the teres minor (h) and major (g) muscles ; '"*^°'

Trapezius.

Deltoi

Supraspinatus,

Biceps (short head)
and coraco-brachialis.

PecLoralis minor.
Glenoid ligament.
Triceps (long head).

Fig. 10. — The Scapula prom the Froitt.

but these attachments will be ascertained in the progress of the
dissection.

The vertebral border of the bone has four muscles inserted into it. and to ba.se ;
Between the superior angle and the spine is the levator anguli
scapulae (figs. 12 and 13, h) ; opposite the spine the rhomboideus
minor (j) is attached ; and between the spine and the inferior angle
the rhomboideus major (k) is inserted : the upper fibres of the last
muscle often end in an aponeurotic arch, which is fixed to the bone
above and below. In front of these muscles, and inserted into the
base of the scapula along its whole length, is the serratus magnus
muscle (figs. 10 and 11, d), the upper and lower parts of which
are much thickeneil, and occupy special surfaces on the ventral
aspect of the corresponding angles of the bone.

The insertion of the small pectoral muscle into the anterior half to eoracoid

^ process.

DISSECTION OF THE UPPER LIMB.

Dissection,

nerves
of sub-
scapularis.

Subscapu-
laris :

origin ;

insertion ;

relations

of the coracoid process at its upper and inner part is also seen

(fig. 11, F).

Dissection. By the separation of the serratiis from the suh-
scapularis there comes into view a thin fascia, which l>elongs to the
latter muscle, and is fixed to the l)one round its margins ; after it
has been observed, it may be taken aM'ay.

In cleaning the muscle, the short, uppermost, suljscapular branch,
of the posterior cord of the brachial plexus will be found entering

its upper part under
cover of the axillary
vessels, and a branch
from the lowest sub-
scapular nerve will be
seen to enter its lower,
or axillary, border.

The subscapularis
muscle is to he followed
forwards to its inser-
tion into the humerus ;
and the axillary vessels
and nerves, with their
offsets to the muscles,
should be well cleaned.

The SUBSCAPULARIS

MUSCLE (fig 11, a) lies
beneath the scapula,
and is for the most
part concealed by that
bone when the limb is
in its natural position.
It arises from the con-
cave ventral surface of
the scapula, except
near the upper and
lower angles, and over
the neck ; and a thick
portion of the muscle
is attached in the
groove along the axillary margin of the bone : many of the fleshy
fil)res spring from tendinous septa which are fixed to the ridges on
the surface of the scapula (fig. 10). The muscle is inserted by a tendon
into the impression on the small tulierosity of the humerus, and by
fleshy fil)res into the bone for nearly an inch below this part (fig. 17).
By one surface the muscle forms a part of the posterior wall of
the axilla, and is in contact with the axillary vessels and nerves,
and the serratus magnus. By the other it rests against the scapula
and the shoulder-joint ; and between its tendon and the root of the
coracoid process is a bursa, which generally communicates with the
synovial cavity of that joint.

The lower border of the muscle projects beyond the scapula, and

Fig. 11. — View of the Subscapularis
THE Surrounding Muscles.

A. Subscapularis.

B. Teres major.

c. Latissimus dorsi.

B. Serratus magnus.

E. Omohyoid,

p. Pectoralis minor.

G. Biceps.

H. Coraco-brachialis.

a. Suprascapular
artery.

1. Suprascapular
nerve, separated from
the artery by the supra-
scapular ligament.

THE DELTOID. 31

IS contiguous to the teres major, the latissimus dorsi, and the long
head of the triceps. The subscapular artery runs along this border,
and its dorsal branch, as well as the posterior circumflex artery and
the circumflex nerve, turn backwards below it.

Action. It rotates the himierus inwards, and when it is raised use.
it depresses that bone.

Dissection. The subsaipularis is to be separated from the Dissection
scapula, except that a thin layer of fibres, in which the ve&sels lie, ^ ^ ^
is to be left on the bone. As the muscle is raised, its tendinous
processes of origin, the connection between its tendon and the cap-
sule of the shoulder-joint, and the bursa are to be observed. A
small arterial anastomosis on the ventral surface of the scapula is
to be dissected out of the fleshy fibres.

The INFRASCAPULAR ARTERY is an offset of the dorsal branch of small infm-
the subscapular vessel (p. 24), and ramifies on the ventral surface artery .'*'^
of the scapula. Passing beneath the subscapular mascle, it forms
an anastomosis with small twigs of the suprascapular and posterior

ipular arteries.

Position. The examination of the muscles on the doi*sal surface Position of
of the scapula may be next undertaken. For this purpose the '™ "
limb is to be turned over ; and a block, which is deep enough to
make the shoulder prominent, is to be placed between the scapula
and the arm.

Dissection. The skin is to be removed from the prominence of Dissection
the shoidder, down to the middle of the outer side of the arm. shoufder.
After its removal some small cutaneous nerves are to be found in
the fat : the upper of these descend over the acromion ; and
a larger branch comes to the surface about half-way down the
posterior border of the deltoid muscle.

Superficial nerves. Branches of nerves, supraacromialy descend Cutaneous
to the surface of the shoulder from the cervical plexus. A cutaneous "^^^^''•
branch of the circumflex nerve (tigs. 13 and 23) turns forwards with
a small companion artery from beneath the posterior border of the
deltoid, and supplies the integmnents covering the lower two-thirds
of the muscle.

Dissection. The fat and fascia are now to be taken from the Dissection
fleshy deltoid, its fibres being made tense for the purpose. Be- muscle?*
ginning at the anterior edge of the muscle, the dissector is to carry
the knife upwards and downwards, following the direction of the
coarse muscular fasciculi. As the posterior edge is approached,
the cutaneous ner^e and vessels escaping from beneath it are to be
dissected out.

At the same time the fascia may be removed from the back of
the scapula, so as to denude the muscles there.

The DELTOID MUSCLE (fig. 13 F,) is triangular in form, Avith Deltoid
the base at the scapula and claWcle, and the apex at the humerus. '"""^ ^ '
It arises from the whole length of the lower border of the spine
of the scapula, the origin being aponeurotic towards the vertebral
border of the bone and blending with the dense fascia over the origin
infraspinatus mascle, from the outer edge of the acromion (fig. 12),

DISSECTION OF THE UPPER LIMB.

and inser-
tion ;

adjacent
parts.

It consists
of three
parts,

and from the outer half or third of the front of the clavicle (fig. 5).
Its fibres converge to a tendon which is inserted into the rough
triangular impression on the outer surface of the humerus, above
the middle (fig. 17, p. 44).

The anterior border is contiguous to the pectoralis major muscle ;
and the posterior rests on the infraspinatus, teres, and triceps
muscles. The origin of the muscle from the bones of the shoulder
corresponds with the insertion of the trapezius. At its insertion
the tendon of the deltoid is tmited with that of the pectoralis
major ; and a fasciculus of the brachialis anticus is attached to the
humerus on each side of it.

The middle or acromial portion of the deltoid is thicker than
the rest, and its fibres form large bundles which run obliquely

Short head of biceps and coraco-brachialis.

Trapezius,

Glenoid ligament

Triceps (long head),

Latissinms dorsi.

Fig. 12. — The Scapula from Behind.

Rhomboidens
minor.

between tendinous septa prolonged from the origin and insertion of
the muscle. The anterior or clavicular and posterior or spinous
portions are somewhat separate from the foregoing, and their fibres
converge to the anterior and posterior edges respectively of the
lower tendon.

Action. The acromial portion of the muscle raises the arm,
abducting it from the body ; the clavicular part flexes the
shoulder-joint, moving the arm forwards and inwards; and the
spinous part draws the arm backwards, or extends the shoulder-
joint.

Dissection (fig. 1 3). The deltoid is to be divided near its origin,
and is to be thrown down as far as the circumflex vessels and nerve
Subacromial beneath will permit. As the muscle is raised a large thick bursa
between it and the upper end of the humerus comes into sight,

which have
different

Dissection
to detach
deltoid.

PARTS COVERED BY DELTOID.

and In' pulling the arm down from the scapula it will be found to
extend beneath the acromion as a large recess. The loose tissue and
fat are to be taken away from the circumflex vessels and nerve ;
and the size of the bursa having been looked to, the remains are to
be removed. The insertion of the muscle should be defined.

Fig. 13. — View of the Muscles of the Dorsum op the Scapula, and o?
THE Circumflex Vessels and Nerve (Illustrations of Dissections).

Muscles :

A. Supraspinatus.

B. Infraspinatus,
c. Teres minor.

D. Teres major.

E. Latissimus dorsi.

F. Deltoid.

G. Triceps (long bead).

H. Levator anguli scapulae.
J. Rhomboideus minor.
K. Rbomboideus major.

Arteries:

a. Posterior circumflex.
h. Branch to teres minor.
c. Dorsal scapular.

Nerves :

1 . Circumflex trunk.

2. Its cutaneous offset.

3. Branch to teres minor.

Parts covered by deltoid. The deltoid conceals the upper end of the ^^^^s ^
humerus, and those parts of the dorsal scapular muscles which are the deltoid,
fixed to the great tuberosity. Lower down are the circumflex vessels
and nerve, and the upper part of the biceps muscle. In front of
the humerus is the coracoid process with its muscles.

Dissection. By followiDg back the posterior circumflex vessels ^^^^^^^^
and nerve through a space between the humerus and the long head circumflex
of the triceps (g), their connection with the axillary trunks will be ^ps.«els,

DA. P

DISSECTION OF THE UPPEE LIMB.

and an-
terior.

Two clrcum
flex arteries :

posterior,

its offsets.

One circum-
flex nerve,

which ends
in deltoid :

branches,
articular ;

posterior

anterior.

Infraspi-
natus :

origin,

insertion,

relations.

arrived at. In clearing the fat from the space a branch of the
nerve to the teres minor muscle is to be songht close to the border
of the scapula, where it is surrounded by dense fibrous tissue.

Arching outwards in front of the humerus is the small anterior
circumflex artery, which should also be cleaned.

The CIRCUMFLEX ARTERIES arise near the termination of the
axillary trunk (p. 24) ; they are two in number, and are named
anterior and posterior from their position to the humerus.

The anterior branch (fig. 7, p. 23) is a small artery, which arises
from the outer side of the axillary and courses outwards beneath the
coraco-brachialis and biceps muscles, and ascends in the bicipital
groove to the articulation and the head of the humerus ; it anasto-
moses with small offsets of the posterior circumflex.

The posterior circumflex artery (fig. 13, a), much larger than the
anterior, winds backwards through a quadrilateral space between
the humerus and the long head of the triceps, in company with the
circumflex nerve, and ends in large branches, in which it anastomoses
with the acromio-thoracic artery.

Brandies are given from it to the shoulder-joint, to the teres
minor, the long head of the triceps, and the integuments. It
anastomoses with the anterior circumflex artery round the neck of
the humerus and with branches of the superior profunda artery
in the substance of the triceps.

The CIRCUMFLEX NERVE (fig. 13,^) leaves the armpit with the
posterior circumflex artery and bends round the humerus, beneath
the deltoid muscle, in which it ends. Many large branches enter the
deltoid ; and one or two filaments pierce the fore part of the muscle
and l>ecome cutaneous.

Branches. As the nerve passes backwards it gives an articular
filament to the under-part of the shoulder-joint. Behind the
humerus it splits into two parts, an anterior and a posterior. The
posterior part furnishes (1) a branch to the teres minor, which has a
reddish gangliform swelling upon it, (2) a few twigs to the back
part of the deltoid, and (3) cutaneous branches which turn round
the edge of the muscle. The anterior part i:>asses round the humerus
with the posterior circumflex artery, and enters the fore part of the
deltoid muscle, a few twigs jmssing through the muscle to the skin
over it.

The INFRASPINATUS MUSCLE (fig. 13, b) occupies the infrasinnous
fossa of the scapula, and extends to the upper end of the humerus.
The muscle arises from the lower surface of the spine of the scapula,
from the dorsal surface of the bone below that process, except at the
neck and the narrow area along the axillary border where the teres
muscles are attached, and from a special fascia covering it. Its
fibres converge to a tendon, which is inserted into the middle
impression on the great tuberosity of the humerus, and joins with
the tendons of the supraspinatus and teres minor. The fleshy fibres
arising from the spine overlie the tendon of the muscle.

A part of the muscle is subcutaneous ; but the upper portion is
concealed by the deltoid, and the lower angle by the latissimus

TERES MUSCLES. 35

dorsi. The lower border is in contact with the teres minor, with
which it is often nnited. The muscle lies on the scapula and the
scapulo-humeral articulation ; and there is sometimes a small bursa
between it and the capsule of the joint.

Action. With the humerus hanging it acts as a rotator outwards ; and use.
and when the bone is raised it will move the arm backwards in
concert with the hinder part of the deltoid.

The TERES MINOR (fig. 1 3, c) is a narrow fleshy slip, which is Teres
often united inseparably with the preceding muscle. It arises on ^^^^^ •
the dorsum of the scapula from a special impression along the upper origin,
two-thirds of the axillary border of the bone, and from an inter-
muscular septum on each side ; and it is inserted by a tendon insertion,
into the lowest of the three marks on the great tuberosity of the
humerus, as well as by fleshy fibres into the bone below that spot,
about an inch altogether.

This muscle is partly covered by the deltoid ; it rests on the parts
long head of the triceps and the shoulder-joint. Underneath it ^™""'^ **>
the dorsal branch of the subscapular artery turns on to the back of
the scapula.

Action. The limb hanging, the muscle rotates it out and moves and use.
it liack ; the arm being raised, the teres depresses the humerus.

The TERES MAJOR MUSCLE (fig. 13, d) passes from the inferior Teres major:
angle of the scapula to the humerus. Its origin is from an oval origin ;
surface behind the inferior angle of the scapula, from the lower
half of the axillary border of the bone, and from the intermiLscular
septum between it and the teres minor. The fibres end in a tendon
which is inserted into the inner edge of the bicipital groove of the insertion ;
humerus.

The muscle assists in forming the posterior fold of the axilla, and
is situate beneath the axillary ves.sels and nerves near the humerus relations ;
(fig. 4). The upper border is contiguous to the subscapularis
muscle, and the lower is received into a hollow formed by the
latissimus dorsi, which covers the teres behind at its origin, and
in front at its insertion. At the humerus the tendon of the
muscle is about two inches wide, and is placed behind that of the
latissimus : the two are separated above by a bursa ; but they are
united below, and an expansion is sent from them to the fascia of
the arm. A second bursa is frequently present between the teres
and the bone.

Action. If the limb hangs, it is carried back behind the trunk, use on
and is rotated inwards by the muscle. The humerus being raised, ^"'^smg
the muscle depresses and adducts it.

With the limb fixed by the hand the teres will cause the lower and fixed
angle of the scapula to move forwards. ^""^'

Below the scapula, where the teres muscles separate from one Triangular
another, is a triangular interval, which is Ijounded in front by the ^P**^-
shaft of the himierus, and above and below by the teres minor and
major (fig. 13). The space is di^^ded into two by the long head
of the triceps. Through the anterior part, which is of a quadri- Quadriia-
lateral shape, the posterior circumflex vessels (a) and the circmnflex ^^™^ space.

DISSECTION OF THE UPPEE LIMB.

Dissection

of ligaments
of the
clavicle,

and of
scapula.

nerve (') pass ; and opposite the posterior triangular space the
dorsal branch (c) of the subscapular artery bends l)ack wards.

Dissection (fig. 14). The ligaments of the scapula and clavicle
should l>e examined.

A strong ligament (coraco-clavicular) ascends from the coracoid
process to the under-part of the clavicle. On removing the areolar
tissue it will be seen to consist of two parts, anterior and posterior,
differing in size, and in the direction of the fibres.

A capsular ligament, connecting the outer end of the clavicle
with the acromion, will be shown l)y taking away the fibres of the
trapezius and deltoid muscles.

Another strong band (coraco-acroniial) passing transversely
between the acromion and the coracoid process, and a small

Fig. 14. — Ligaments of the Clavicle and Scapula, and of the
Shoulder-joint (altered from Bourgery).

1. Conoid ligament.

2. Trapezoid ligament.

3. Coraco-acromial ligament.

4. Suprascapular ligament.

5. Capsule of shoulder- joint.

6. Tendon of long head of biceps,
entering the joint.

7. Tendon of subscapularis muscle.

8. Coraco-huraeral ligament.

fasciculus (suprascapular ligament), placed over the notch in the
superior border, are then to be defined.

Union of the LIGAMENTS OF THE CLAVICLE AND SCAPULA (fig. 14). The

scapuia.^"^ outer end of the clavicle forms a synovial joint with the acromion,

and is united to the coracoid process by a strong coraco-clavicular

ligament.

The CORACO-CLAVICULAR LIGAMENT consists of two portions, e^ich

having a difi'erent direction and designation.

The posterior piece (i), called conoid from its shape, is fixed by

its apex to the posterior and inner part of the coracoid process,

and by its base to the tubercle of the clavicle, at the junction of

the outer with the middle third of the bone,
and a square The anterior part (2) trapezoid ligament, is larger than the conoid ;

it is attached below to the inner border of the coracoid process along

Coraco-cla-
vicular has

a conical

LIGAMENTS OF SCAPULA. 37

the hinder half, and above to the line on the imder-surfaee of the
cla\'icle, which extends outwards from the tubercle before mentioned.
The two pieces of the ligament are in apposition behind, but are
usually separated by an interval in front.

Use. Both pieces of the ligament support the scapula in a state Use of liga-'
of rest. They serve also to restrain the rotatory movements of that '"^'^*'-
bone ; thus, when the acromion is rotated down, the motion is
checked by the trapezoid l^and, and when upwards by the conoid
piece.

AcROMio-CLAVicuLAR ARTICULATION. The articular surfaces of Joint with
the clavicle and acromion process of the scapula are connected ^^^^^^^'^ •
together by a capsule, which is thick above (superior ligament), but capsule,
very thin below.

An interarticular fibro-cartiluge is sometimes present at the upper ftbro-carti-
part of the joint ; and occasionally it forms a complete septum. If *^^'
the fibro-cartilage is perfect, there are two synovial cavities in the and synovial
joint ; if it is imperfect, there is only one. The joint should be
opened to see the cartilage and the synovial sac.

Movements. This articulation allows the scapula to change its Use of
position in relation to the clavicle when the former bone is moved, ^^^^ '
either in gliding over the surface of the thorax, or in being rotated
with the elevation and depression of the arm.

Scapular Ligaments. The special liganunts of the scapula are Ligaments
two in number, and extend from one point of the bone to another. ° scapu

1. The SUPRASCAPULAR ligament (^) is a narrow band stretching supra-
across the notch in the upper border of the bone. By one end it is ^^P"*^'
attached to the base of the coracoid process, and by the other to the
border behind the notch. It converts the notch into a foramen,
through which the suprascapular nerve passes.

•2. The CORACO- ACROMIAL ligament (^) is triangular in form, and coraco-
extends transversely between the acromion and the coracoid process.
Externally it is inserted by its apex into the tip of the acroniion ;
and internally, where it is much wider, it is attached to all the
outer border of the coracoid process, reaching backwards to the
capsule of the shoulder-joint. The ligament consists usually of two formed of
thickened bands, anterior and posterior, with a thinner intervening ^^P'*'^^*'-
part. It forms part of an arch above the shoulder-joint, which pre- use.
vents the head of the humerus being displaced upwards.

Dissection. The supra^^pinatus muscle should now be laid bare. Dissection,
the acromion process sawn through, and turned aside with the outer
end of the clavicle. A strong fascia will be seen to cover the sur-
face of the supraspinatus muscle, and is to be taken away after it
has been observed.

The supraspinatus muscle (fig. 13, a) has the same form as the Supraspina-
hollow of the bone which it fills. It arises from the surface of the
supraspinous fossa of the scapula, except over the neck, from the o"gin ;
upper side of the spine of the bone, and from the fascia covering its
surface. Its fibres end in a tendon, which crosses over the
shoulder-joint, and is inserted into the upper impression on the insertion ;
great tuberosity of the humerus.

DISSECTION OF THE UPPER LIMB.

relations

Dissection
of supra-
scapular

Supj-a-

scapular

artery

ends in
infraspina-
tus and

subscapular
and supra-
spinous
offsets.

Vein.

Suprascapu-
lar nerve :

branches,
muscular

and articu-
lar.

Posterior
scapular
artery.

Dorsal sca-
pular artery

The muscle is concealed by the trapezius and the acromion
process ; and it rests upon the scapula, the suprascapular vessels
and nerve, and the shoulder-joint. Its tendon joins that of the
infraspinatus at the attachment to the humerus.

Action. It comes into use with the acromial portion of the
deltoid in raising the limb and supporting the joint.

Dissection (tig. 22, p. 52). The vessels and nerves on the
dorsum of the scapula can be traced by detaching from behind
forwards the supraspinatus and infraspinatus nmscles, so as to leave
a thin layer of the fleshy fibres with the ramifying blood-vessels on
the surface of the bone. In the supraspinous fossa are the supra-
scapular vessels and nerve, which are to be followed beneath the
acromion to the infraspinous fossa ; and entering the infraspinous
fossa, beneath the teres minor muscle, is the dorsal branch of the
subscapular artery. The anastomosis between these vessels should
be pursued in the fleshy fibres and cleaned.

The SUPRASCAPULAR ARTERY (a) is derived from the thyroid axis
of the subclavian trunk (p. 9). After a short course in the neck
it crosses over the suprascapular ligament, and passing beneath the
supraspinatus muscle, ends in the infraspinous fossa, where it gives
oftsets to the infraspinatus muscle and the scapula, and anastomoses
with the dorsal branch of the subscapular artery and the posterior
scapular of the subclavian.

Before entering the supraspinous fossa, it gives a small branch to
the ventral surface of the scapula ; and beneath the supraspinatus it
furnishes offsets to that muscle, the bone, and the shoulder-joint.

The companion vein of the suprascapular artery joins the external
jugular vein.

The SUPRASCAPULAR NERVE (') is a branch of the brachial plexus
(5th and 6th cervical nerves ; fig. 8, sps., p. 26). At the upper
border of the scapula, it enters the supraspinous fossa beneath the
suprascapular ligament. In the fossa it supplies two branches to
the supraspinatus ; and it is continued beneath a fibrous band to
the infraspinatus muscle, in which it ends.

The nerve gives some articular filaments to the shoulder-joint,
and other oftsets to the scaj)ula.

The POSTERIOR SCAPULAR ARTERY runs along the base of the
scapula beneath the rhomboid muscles, furnishing ofl"sets to them
and to the surfaces of the bone. It has been more fully noticed
with the dissection of the back (p. 9).

The DORSAL SCAPULAR ARTERY (5) is a branch of the subscapular
(p. 24), and, after giving off its infrascapular oftset, turns round
the axillary border of the bone opposite the posterior of the two
spaces between the teres muscles. Entering the infraspinous fossa
beneath the teres minor, it supplies that muscle and the infraspi-
natus, and anastomoses with the suprascapular and posterior scapular
arteries. It sends a considerable branch downwards between the
teres muscles, towards the lower angle of the bone.

SUPERFICIAL STRUCTURES OF ARM.

Section III.

THE FRONT OP THE ARM.

Position. For the dissection of the superficial vessels and nerves Position,

on the front of the arm the limb should lie flat on the table, with

the anterior surface uppermost.

Dissection. The skin is to be raised from the fore and lateral and inci-
sions in the
skin.

Circumflex,

Upper external cutaneous
bninch of musculo-spiral.

Musculo-cutaneous

Median.

Supraclavicular.

Small internal cutaneous.
In tercasto-hiuneral .

^Branches of internal cutaneous.

Ulnar.

Fig. 15. — Diagram op Cutaneous Nerves of Front of Arm.

surfaces of the arm and elbow. One incision should be made
along the centre of the limb as far as two inches below the
bend of the elbow, and at the termination of this a second
cut half round the forearm. Strip the skin from the limb as
low as the transverse incision, leaving the fat and the cutaneous
vessels and nerves behind. For special dissections of the parts
in front of the bend of the elbow the incisions (13, 14, 15)

DISSECTION OF THE ARM.

Seek super-
ficial veins.

shown on fig. 1, B, should be used. The skin will thus remain
hinged along a narrow attachment running down the middle
of the back of the arm, from which it can be used to cover
the part.

The cutaneous veins (fig. 16) should be first sought for in
the fat. They are very numerous below the bend of the elbow, as
they issue from beneath the integument. In the centre of the
forearm is the median vein, which bifurcates rather below the
eibow, sending branches to either side. On the outer side is

Anastomotica
Magna Artery

Internal Cutaneous

Nerve ; posterior

branch.

Internal Cutaneous
Nerve ; anterior -^r
branch. ''

Musculo-cuta-
neous Nerve ;
posterior branch.

• Musculo-cutaneous
Nerve ; anterior
branch.

Radial
recurrent Artery.

Supinator longus.

Extensor carpi
Radialis longior.

Fig. 16. — Dissection op the Front of the Elbow (After Morris).

Trace cuta-
neous
nerves

of outer
side

the radial vein ; and internally are the anterior and posterior ulnar
veins, coming from the front and back of the forearm. At the
elbow the veins are united into two stems, one (basilic) passing
upwards along the inner side, and the other (cephalic) along the
outer side of the arm.

The cutaneous nerves are next to be traced out. Where they
perforate the deep fascia they lie beneath the fat ; and this layer
must be scraped through to find them.

On the outer side of the arm, about the middle, two external
cutaneous branches of the musculo-spiral are to be sought. In the
outer bicipital groove, in front of the elbow or rather below it, the

SUPERFICIAL VEINS OF ARM. 41

cutaneous part of the musculo-cutaneous nerve will be recognised.
See tig. 16.

On the inner part of the limb the nerves to the surface are more apd »«""•
numerous. Taking the basilic vein as a guide, the internal cuta- umb.
neous nerve of the forearm will be found by its side, about the
middle of the arm ; and a little external to this nerve is a small
cutaneous offset from it, which pierces the fascia higher up.
Finally follow down the small nerves which have been already met
with in the dissection of the axilla, viz., the iJitercosto-humeral, the
lesser internal cutaneous (nen'^e of Wrisberg), and the internal
cutaneous of the musculo-spiral.

Superficial fascia. The subcutaneous fatty layer forms a con- Superficial
tinuous investment for the limb, but it is thicker in front of the * "
elbow than in the other parts of the arm. At that spot it encloses
the superficial vessels and lymphatics.

CcTANEOUS Veins. The position and relations of the veins in Superficial
front of the elbow are to be attentively noted 1)V the dissector, '^^i^*-
l)ecause the operation of venesection is practised on one of them
(fig. 16).

The MEDIAN VEIN of the forearm di\4des into two branches, Median
internal and external, rather below the bend of the elbow ; ^^*"'
and at its point of di^dsion it is joined by an offset from a deep two
vein. The internal branch (median-basilic) crosses to the inner ™"*^
border of the biceps, and unites with the ulnar veins to form
the basilic vein of the inner side of the arm. The external
branch (rnedian-cephalic) is usually longer than the other, and by
its junction with the radial vein gives rise to the cephalic vein of
the arm.

The MEDIAN-CEPHALIC VEIN is directed obliquely, and lies over median-
the hollow between the biceps and the outer mass of muscles of the '^'^^ ^ '^ '
forearm ; beneath it is the trunk of the musculo-cutaneous nerve.
This vein is altogether removed from the brachial artery, and is
usually smaller than the median-basilic vein. If opened with a
lancet it does not generally yield much blood, in consequence of its
position in a hollow between muscles rendering compression of it
very uncertain and difficult.

The MEDIAN-BASILIC VEIN is more transverse in direction, and median-
larger than the preceding ; and it crosses the brachial artery. It '^^'^'*^-
is firmly supported by the underlying fascia, the aponeurosis of
the arm, strengthened by an offset from the biceps tendon, inter-
vening between it and the brachial vessels. Branches of the
internal cutaneous nerve lie beneath it, and some twigs of the same
nerve are placed over it.

The median-basiHc is the vein on which the operation of blood- Venesection,
letting is commonly performed. It is selected in consequence of its
usually larger size, and more superficial position, and of the ease
with which it may be compressed ; but, from its close proximity to
the brachial vessels, the spot to be opened should not be immediately
over the trunk of the artery.

The BASILIC VEIN, commencing as before said, ascends near Basilic vein.

DISSECTION OF THE AEM.

Cephalic
vein.

Superficial
lymphatics

and glands.

Superficial
nerves.

External
cutaneous
nerves :

two from
musculo,
spiral ;

and mus-
culo-cuta-
neous.

Internal

cutaneous

nerves.

lai^e

and small

the inner border of the biceps muscle to the middle of the arm,
where it passes beneath the deep fascia, and is continued into the
axillary vein. In this course it lies to the inner side of the brachial
artery.

The CEPHALIC VEIN is derived chiefly from the external branch
of the median, for the radial vein is oftentimes very small ; it is
continued to the shoulder along the outer side of the biceps, and
sinks between the deltoid and pectoral muscles to open into the
axillary vein near the cla^dcle.

The superficial lymphatics of the arm lie for the most part along
the basilic vein, and enter the glands of the axilla. A few lym-
phatics accompany the cephalic vein, and end in the upper axillary
glands.

One or more superficial lymphatic glands are commonly found a
little above the inner condyle of the humerus.

Cutaneous Nerves (fig. 15). The superficial nerves of the
arm apj)ear on the inner and outer sides, and spread so as to cover
the surface of the limb. With one exception (intercosto-humeral),
all are derived from the brachial plexus, either as distinct branches,
or as offsets of other nerves. On the outer side of the limb are
branches of the musculo-spiral and musculo-cutaneous nerves. On
the inner side are two internal cutaneous nerves from the plexus, a
third internal cutaneous from the musculo-spiral, and the intercosto-
humeral nerve.

The EXTERNAL CUTANEOUS BRANCHES OF THE MUSCULO-SPIRAL

NERVE are two in nimiber, and ajjpear at the outer side of the
limb about the middle. The wpper small one turns forwards
with the cephalic vein, and i-eaches the front of the elbow,
supplying the anterior part of the arm. The lower and larger
pierces the fascia somewhat farther down, and, after supplying
some cutaneous filaments to the back of the arm, is continued to
the forearm.

The MUSCULO-CUTANEOUS NERVE pierces the fascia in front of
the elbow ; it lies beneath the median-cejjhalic vein, and divides
into branches for the forearm.

The INTERNAL CUTANEOUS NERVE perforates the fascia in two
pieces, or as one trunk that divides almost directly into two. Its
anterior branch passes beneath the median-basilic vein to the front
of the forearm ; and the posterior winds over the inner condyle of
the humerus to the back of the forearm.

A slender oftset of the nerve pierces the fascia near the axilla,
and reaches as far, or nearly as far, as the elbow ; it supplies the
integuments over the biceps muscle.

The NERVE OP Wrisberg (small internal cutaneous) appears
behind the preceding, and extends to the interval between the
olecranon and the inner condyle of the humerus, where it ends in
filaments over the back of the olecranon. The nerve gives offsets
to the lower third of the arm on the inner and posterior surfaces,
and joins above the elbow the posterior branch of the larger internal
cutaneous nerve.

BICEPS MUSCLE. 43

The INTERNAL CUTANEOUS BRANCH OF THE MUSCULO-SPIRAL one from

NERVE, becoming subcutaneous in the upper third, winds to the spiral ;
back of the arm, and reaches nearly as far as the olecranon.

The INTERCOSTO-HUMERAL NERVE, a branch of the second inter- and inter-
costal (p. 13, and fig. 4), perforates the fascia near the axilla, and humeral,
ramifies on the inner side and posterior surface of the arm in the
upper half. The size and distribution of this nerve depend upon
the development of the small internal cutaneous and the offset of
the musculo-spiral.

The DEEP FASCIA of the arm is a white shining membrane, which Aponeurosis
surroujids the limb, and sends processes between the muscles. ° ^*™^
Over the biceps muscle it is thinner than elsewhere. At certain
points it receives accessory fibres from the subjacent tendons : thus, receives ac-
in front of the ell.'ow an offset from the tendon of the biceps joins it ; f^°^
and near the axilla the tendons of the pectoralis major, latissimus tendons ;
dorsi, and teres major send prolongations to it.

At the upper part of the limb the fascia is continuous with that disposition
of the axilla, and is prolonged over the deltoid and pectoral muscles '

to the scapula, clavicle, and chest. Below, it is continued to the and below ;
forearm, and is connected to the prominences of bone around the
■'1 bow-joint, especially to the supracondylar ridges of the humerus, forms inter-

is to give rise to the intermuscular septa of the arm. Spt£^^

Dissection. The muscles and vessels of the arm will next be
ilissected ; the limb is still to lie on the back, but the shoulder is
to be raised by means of a small block ; and the scapula is to be
fixed in such a position as to render tense the muscles. The inner
surface of the arm is to be placed towards the dissector.

The aponeurosis is to be reflected from the front of the arm by Dissection
an incision along the centre, like that through the skin ; and it is ° ^'^^ ^'
to be removed on the outer side as far as the outer supracondylar
ridge of the humerus, but on the inner side rather farther back
than the corresponding line, so as to lay bare part of the triceps of vessels,
muscle. In raising the fascia the knife must be carried in the
direction of the fibres of the biceps muscle ; and, to prevent the
displacement of the brachial artery and its companion nerves,
fasten them here and there with stitches.

In front of the elbow is a hollow containing the brachial vessels ; ?°J°^ ^
and into this the artery shoidd be followed, to show its ending in elbow,
the radial and ulnar trunks.

Muscles on the Front of the Arm. There are only three Position of
muscles on the front of the arm. The one along the centre of the of the arm.
limb is the biceps ; and that along its inner side, reaching about
half-way down, is the coraco-brachialis. The brachialis anticus lies
beneath the biceps. Some muscles of the forearm are connected to
the inner and outer condyles of the humerus, and to the ridge above
the outer condyle.

The BICEPS muscle (fig. 18, p. 45, and fig. 7, p. 23) forms the Bleeps
prominence seen on the front of the arm. It is wider at the brachii:
middle than at either end ; and the upper end consists of two
tendinous pieces of different lengths, which are attached to the

DISSECTION OF THE ARM.

origin from
the scapula

insertion
Into radius

scapula. The sJiort head is the innermost, and arises from the
tip of the coracoid process in common with the coraco-brachialis
muscle (fig. 10, p. 29) ; and the longhead is attached just above the
glenoid fossa of the scapula, within the capsule of the shoulder-joint
and is connecte(' with the glenoid ligament on either side of the fossa.
Muscular fibres spring from each tendinous head, and meet to form
a fleshy belly, which is somewhat flattened from before l)ack.
Inferiorly the biceps ends in a tendon, which is inserted into the
tuberosity of the radius (fig. 25, p. 61), having previously given oft'
a slip to the fascia in front of the elbow.

- — Supraspinatus.
f . ' "~^^\i Subscapularis.

Pectoralis major.

Supinator longus.

Ext. carpi radialis longior.
Common origin of extensors.

Latissimus dorsi.
Teres major.

Inner head of triceps.

Coraco brachialis.

Pronator teres.
Common origin of flexors.

Fig. 17. — The Humerus from the Front.

The muscle is superficial except at the extremities. At the
upper part it is concealed by the pectoralis major and deltoid
muscles ; and at the lower end the tendon dijjs into the hollow in
and beneath front of the elbow. Beneath the biceps are the musculo-cutaneous
nerve, the upper part of the humerus, and the brachialis anticus

parts
covering

it;

inner border muscle. Its inner border is the guide to the brachial artery below

the^artery ; ^^^ middle of the humerus, but above that spot the coraco-brachialis

muscle intervenes between them. The connection of the long head

of the biceps with the shoulder-joint and the insertion of the muscle

into the radius will be afterwards learnt.

radius Action. It bends the elbow-joint, and acts powerfully in

COKACO-BRACHIALIS.

supinating the radius. When the body is hanging by the hands it
will apply the scapula
firmly to the humerus,
and will assist in raising
the trunk.

With the arm hang-
ing and the radius fixed,
the long head will
assist the abductors in
removing the limb from
the side ; and, after
the limb is abducted,
the short head will aid
in restoring it to the
])endent position.

The CORACO-BRACHI-

ALis is partly concealed
by the biceps, and
extends to the middle
of the arm. Its origin
is fleshy from the tip
of the coracoid pro-
cess (fig. 10), and from
the tendinous short
head of the biceps. Its
fibres become tendinous
below, and are inserted
into a narrow mark
on the inner side of
the humerus, below
the level of the del-
toid (fig. 17). Some of
the fibres frequently
end on an aponeurotic
arch, which extends
from the upper end of
the humerus to the in-
sertion of the muscle.

The upper half of
this muscle is beneath
the pectoralis major
(fig. 20, p. 49) ; and
its inner part projects
beyond the short head
of the biceps, forming
a prominence in the
axilla. Its insertion is
covered by the brachial
vessels and the median
nerve. The coraco-brac

and the
trunk,

on humerus.

Coraco-
brachialis

ongin ;

insertion ;

18.— Axillary akd Brachial Arteries
(Quain's "Arteries").
1. Axillary artery 5. Superior profunda

relations ;

and brauches. The
small branch above the
figure is the supenor
thoracic, and the larger
branch close below the
acromio-th oracic.

2. Long thoracic.

3. Subscapular.

4. Brachial artery.

branch.

6 Inferior profunda.

7. Anastomotic.

8. Biceps muscle.

9. Triceps muscle.
The median and ulnar
nerves are shewn in
the arm ; the median
is close to the brachial
arteiy.

hialis lies over the subscapular muscle, the

DISSECTION OF THE ARM.

anterior circumflex vessels, and the tendons of the latissimus dorsi
and teres major. Along the inner border are the large artery
and nerves of the limb ; and the musculo-cutaneous nerve per-
forates it.

use on limb. Action. The coraco-brachialis moves forwards the arm, and
add nets it to the thorax.

arter^^ex- '^^^ BRACHIAL ARTERY (fig. 18,*) is a continuation of the axillary

tends to
elbow :

Superior profunda.

Branch to Olecranon Fossa.

Posterior terminal branch,

Anterior terminal branch

Radial recurrent.
Post. Interosseous recun'ent.

Brachial artery.

Inferior profunda.

Anastomatica Magna.

Anastomatica Magna, posterior

branch.

Anastomatica Magna, anterior

branch.

Olecranon Fossa.

Anterior ulnar recurrent.
Posterior ulnar recunent.

Fig. 19. — Anastomosis about the Elbow Joint.

trunk, and supplies vessels to the upper limb. It begins at the

lower border of the teres major muscle, and terminates rather

below the bend of the elbow, or opposite the neck of the radius,

in two branches, radial and ulnar, for the forearm.

position to The vessel is internal to the humerus in the upper part of its

the limb; course, but in front of the bone below the middle of the arm;

and its situation is indicated by the surface depression along the

inner border of the biceps and coraco-brachialis muscles.

wUhfescia Throughout the arm the brachial artery is superficial, being

BRACHIAL ARTERY. 47

covered only by the integuinents and the deep fascia ; but at the
bend of the elbow it oecomes deeper, and is crossed by the pro-
longation from the tendon of the biceps. Posteriorly the artery has
the following muscular connections (fig. 20, p. 49): — While it is and
inside the humerus it is placed over the long head of the triceps (f) '"'^^c^^'^'
for two inches, but separated partly by the musculo-spiral nerve
and profunda vessels, and over the inner head (g) of the same
muscle for about an inch and a half. But when the vessel j)asses
to the front of the bone it lies on the insertion of the coraco-
brachialis (g) and on the brachialis anticus (h). To the outer
side are the coraco-brachialis and biceps muscles (c and b), the latter
overlapping it.

Veins. Venae comites lie along the sides of the artery (fig. 20, d), with veins,
encircling it with cross branches, and the median-basilic vein
crosses over it at the elbow. The basilic vein is near the artery,
on the inner side, above ; but it is superficial to the fascia in the
lower half of the arm.

The nerves in relation vrith the artery are the folloAving : — and with
The internal cutaneous (fig. 20, 2) is in contact with the vessel
until it perforates the fascia about the middle of the arm. The
ulnar nerve ("*) lies to the inner side as far as the insertion of
the coraco-brachialis muscle ; and the musculo-spiral is behind
for a distance of two inches. The median nerve (fig. 20, l) is close
to the vessel throughout, but alters its position in this way : —
as low as the insertion of the coraco-brachialis it is placed on
the outer side, but it then crosses obliquely over, or occasionally
under, the artery, and becomes internal about two inches above
the elbow-joint.

Unusual position. The brachial tnink occasionally leaves the inner Deviation
border of the biceps in the lower half of the arm, and courses along the in position;
intertnuscnlar septum, with or without the median nerve, to near the
inner condyle of the humerus. At this spot the vessel is directed to its
ordinary position in front of the elbow, beneath the upper fibres of the
pronator teres, which has then a wide origin. In this unusual course the
artery lies behind a projection (supracondylar process) of the humerus.

Muscular covering. In some bodies the brachial artery is covered by an in muscular
additional slip of origin of the biceps, or of the brachialis anticus muscle, covering.
And sometimes a slip of the brachialis may conceal, in cases of high
origin of the radial, the remainder of the arterial trunk continuing to the
forearm.

High division. Instead of a single trunk, there may be two vessels in 4*"^^
the lower part, or even the whole length of the arm, owing to an un- °" ^'
usually high origin of one of the arteries of the forearm, more frequently
the radial.

Vasa aherrantia. Occasionally a long slender vessel passes from the Aberrant
brachial or the axillary trunk to the radial, rarely to the ulnar artery. vessels.

Branches spring both externally and internally from the brachial its branches
artery (fig. 18). Those on the outer side, muscular, supply the j^jgcular
coraco-brachialis, biceps, and brachialis anticus, as well as the lower
part of the deltoid ; those on the inner side are the superior
and inferior profunda, the medullary artery of the humerus,

DISSECTION OF THE ARM.

superior
profunda,

inferior
profunda,

artery to
bone.

and anas-
tomotic.

Veins end in
the axillary.

Nerves on
front of arm.

Median
nerve with
the artery

has not any
branch.

and the anastomotic branch. The superior and inferior pro-
funda and the anastomotic branches of the brachial form a free
anastomosis about the elbow-joint with various arteries of the
forearm, and the accompanying scheme (fig. 19) represents the
general arrangement.

The superior profunda branch (^) is larger than the others, and
leaves the artery near the lower border of the teres major ; it winds
backwards with the musculo-spiral nerve to the triceps muscle, and
will be dissected with the back of the arm (p. 53).

The inferior profunda branch C') arises opposite the coraco-
brachialis muscle, and accompanies the ulnar nerve to the interval
between the olecranon and the inner condyle of the humerus.
There it anastomoses with the posterior ulnar recurrent and anasto-
motic branches, and supplies the triceps. It often arises in common
with the superior profunda artery.

The medullary artery of the humerus arises near the inferior^
profunda, generally associated with various muscular branches, and
enters the aperture about the middle of the humerus, being directed
downwards.

The anastomotic branch (') arises one or two inches above the
elbow, and its main branch courses inwards through the inter-
muscular septum to the hollow between the olecranon and the
inner condyle of the humerus. Here the artery anastomoses with
the inferior profunda and posterior ulnar recurrent branches, and
gives twigs to the triceps muscle ; one of the offsets forms an arch
across the back of the humerus with a branch of the superior
profunda.

Before passing through the intermuscular system the artery sends
an offset to the pronator teres muscle in front of the internal condyle,
which joins the anterior ulnar recurrent vessel.

The BRACHIAL VEINS (fig. 20, d) accompany the artery, one on
each side, and have branches of communication across that vessel ;
they receive tributary veins corresponding to the branches of the
artery. Above, they usually join into one, which enters the
axillary vein near the subscapular muscle.

Nerves of the arm (fig. 20). The nerves on the front of
the arm are derived from the terminal cords of the brachial
plexus. They furnish but few offsets above the elbow, b.eing
for the most part continued to the forearm and the hand.
The cutaneous branches of some of them have been already
referred to (p. 42).

The MEDIAN NERVE (') arises from the l)rachial plexus by two
heads, one from the outer, and the other from the inner cord
(fig. 7, p. 23), and accompanies the brachial artery to the forearm.
Beginning on the outer side of the artery, the nerve crosses over
(sometimes under) it near the middle of the arm, and is placed on
the inner side a little above the elbow. It does not give any branch
in the arm ; but there may be a fasciculus connecting it with the
musculo-cutaneous nerve. Its relations to muscles are the same as
those of the artery.

NERVES OF THE ARM.

The ULNAR NERVE (^), derived from the inner cord of the brachial Ulnar nen-e
plexus, lies close to the inner side at first of the axillary, and then
of the brachial artery as far as the insertion of the coraco-brachialis ;
then leaving the blood-vessel, it is directed backwards through the
inner intermuscular septum to the interval between the olecranon
and the internal condyle, being surrounded by the muscular fibres is without
of the triceps,
reaches the elbow-joint.

The INTERNAL CUTANEOUS (~) is mainly distributed in the fore- internal
arm. Arising from the inner cord of the plexus, it is at first nerve be-
superficial to the brachial artery as far as the middle of the arm, ?^^^ ^^^

There is not any branch from the nerve till it fa'^asthe

elbow.

20. — Dissection of the Inner Side op the Arm (Illustrations
OF Dissections).

Muscles :

A. Pectoralis major.

B. Biceps.

c. Cotaco-brachialis.

D and E. Latissimus and teres.

F. Long head of triceps.

G. Inner head of triceps.
H. Brachialis anticus.

Vessels :

a. Brachial artery.

b. Inferior profunda.

e. Anastomotic.

d. Internal vena comes, joining
the basilic vein a little above the
middle of the arm.

Nerves :

1. Median.

2. Internal cutaneous.

3. Nerve of Wrisberg.

4. Ulnar.

5. Muscular to the triceps.

6. Internal cutaneous from
musculo-spiral.

the

where it divides into two branches that perforate the investing
fascia and reach the forearm. Near the axilla it furnishes a small
offset to the skin of the front of the arm.

The NERVE OF Wrisberg (small internal cutaneous 3) arises xerve of
with the preceding. Concealed at first by the axillary vein, it is J^^eShe
directed inwards beneath (but sometimes through) that vein, and fascia,
joins with the intercosto-humeral nerve. Afterwards it lies along
the inner part of the arm as far as the middle, where it perforates
the fascia to end in the integument.

Musculo-
cutaneous
nerve in the
arm :

its muscular
branches.

Dissection.

Define
brachialis.

Brachialis
anticus :
origin ;

insertion :

relations of
surfaces,

of borders ;

use, fore-
arm free.

and fixed.

DISSECTION OF THE ARM.

The MUSCULO-CUTANEOUS NERVE, named from supplying muscles
and integuments, ends on the surface of the forearm. It leaves the
outer cord of the brachial plexus opjiosite the lower border of the
pectoralis minor, and immediately perforates the coraco-brachialis ;
it is then directed obliquely to the outer side of the limb beneath
the biceps and lying ujDon the brachialis anticus. At the front of
the elbow it becomes a cutaneous nerve of the forearm.

Branches. The nerve furnishes a branch to the coraco-brachialis
before entering the muscle, and others to the biceps and brachialis
anticus where it is placed between them.

Dissection. The brachialis anticus muscle will now be brought
into view by cutting through the tendon of the biceps near the
elbow, and turning upwards this muscle. The fascia and areolar
tissue should be taken from the fleshy fibres ; and the lateral extent
of the muscle should be defined on each side, so as to show that it
reaches the intermuscular septum largely on the inner side, but
only for a short distance above on the outer side.

Some care is required in detaching the brachialis on the outer
side from the muscles of the forearm, to which it is closely applied.
As the muscles are separated, the musculo-spiral nerve, accompanied
by a small branch of the superior profunda artery, comes into sight.

The BRACHIALIS ANTICUS (fig. 20, h) covers the elbow-joint and
the lower half of the front of the humerus. It arises from the
anterior surface of the humerus below the insertion of the deltoid
muscle, and from the intermuscular septa on the sides, viz., from
all the inner, but from only the upper part of the outer (fig. 17,
p. 44). The fleshy fibres converge to a tendon, which is inserted
into the impression on the front of the coronoid process of the
iilna (fig. 25, p. 61).

This muscle is for the most part concealed by the biceps. On it
lie the brachial vessels, with the median, musculo-cutaneous, and
musculo-spiral nerves. It covers the humerus and the articulation
of the elbow. Its origin embraces by two slips the tendon of the
deltoid ; and its insertion is placed between two fleshy points of the
flexor profundus digitorum. The inner border reaches the inter-
muscular septum in all its length ; but the outer is separated below
from the external intermuscular septum by two muscles of the
forearm, supinator longus and extensor carpi radialis longior.

Action. The brachialis brings forward the ulna towards the
humerus, and bends the elbow-joint.

If the ulna is fixed, as in climbing with the hands above the
head, the muscle bends the joint by raising the humerus.

BACK OF THE ARM.

Position of
the part.

Position. During the examination of the back of the arm, the
limb is to be raised in a semiflexed position by means of a block
beneath the elbow. The scapula is to be brought nearly in a line
with the humerus, so as to tighten the muscular fibres ; and it is to
be fastened with hooks in that position.

THE TRICEPS.

Bissection (fig. 22). On the back of the arm there is one muscle, Lay bare the
the triceps, beneath which are placed the musculo-spiral nerve and ^^^^^^^'
superior profunda vessels. The skin having been reflected and
the bursa over the olecranon process having been looked for, the
muscle will be laid bare readily, for it is covered only by fascia.
To take away the fascia, carry an incision along the middle of the
limb to the point of the elbow ; and in reflecting it the loose
subaponeurotic tissue should be removed at the same time.

Supra-spinatus.

Infraspinatus.
Teres minor.

Outer head of triceps.

Brachialis anticus.

Supinator longus.

n \

External condyle.

Internal condyle.

xrr-^

^\ Anconeus.

Trochlea.

Fig.

21.-

-The

Humerus

FROM BEHIND.

Separate the middle from the inner and outer heads of the and separate
muscle, and clear the interval between them, tracing the musculo- ^^^^^'
spiral nerve and vessels beneath the muscle. Define the outer
head, which reaches down to the spot at which the musculo-spiral
nerve appears on the outer side.

The TRICEPS MUSCLE (fig. 22) is divided superiorly into three Triceps
heads of origin, inner, outer, and middle. Two of these are attached Ji^ee heads :
to the humerus, and one to the scapula.

The middle or lo7ig head (a) has a tendinous origin, about an inch origin of
wide, from a rough mark on the axillary margin of the scapula head,
close to the glenoid cavity, where it is united with the capsule of
the shoulder-joint. The outer head (b) arises from the back of the of outer

head.
e2

DISSECTION OF THE AKM.

humerus along a narrow attachment

and of inner

direction of
the fibres ;

insertion

relations ;

Fig. 22. — Dissection op the Dorsal
Scapular Vessels and Nerve, and
OF THE Triceps Muscle.

Muscles :

A. Long head of
triceps.

B. Outer head, with
a bit of whalebone
beneath it to mark
the extent of its
attachment down the
humerus.

c. Inner head.

D. Anconeus.

E. Supinator longus.

F. Extensor carpi
radialis longior.

G. Teres major.

H. Teres minor.

I. Infraspinatus,
cut across.

J. Supraspinatus,
cut through.

Arteries :

a. Suprascapular.

b. Dorsal scapular.

c. Posterior cir-
cumflex.

Nerves :

1. Suprascapular.

2. Circumflex.

Two inter-
muscular
septa :

long head passes the shoulder it can
and adduct the arm.

The INTERMUSCULAR SEPTA should

extending from the root of
the large tuberosity to
the spiral groove. The
inner head (c), fleshy
and wide, arises from the
posterior surface of the
humerus below the spiral
groove, reaching laterally
to the intermuscular septa,
and gradually tapering up-
wards as far as the inser-
tion of the teres major.
From the different heads
the fibres are directed with
varying degrees of inclina-
tion to a wide common
tendon above the elbow.
Inferiorly the muscle is
inserted into the end of the
olecranon process of the
ulna, and gives an expan-
sion to the aponeurosis of
the forearm. Between the
tip of the olecranon and
the tendon there is some-
times a small bursa.

The triceps is super-
ficial, except at the upper
part where it is overlapped
by the deltoid muscle. It
lies on the humerus, the
musculo-spiral nerve, the
superior profunda vessels,
and the articulation of the
elbow. On the sides the
muscle is united to the
intermuscular septa ; and
the lowest fibres are con-
tinuous externally with the
anconeus — a muscle of the
forearm.

Action. All the pieces
of the triceps combining
in their action will bring
the ulna into a line with
the humeru.s, and extend
the elbow-joint. As the

depress the raised humerus,

be carefullv noticed. Thev

SUPERIOR PROFUNDA ARTERY. 53

are fibrous processes continuous witli the investing aponeurosis of
the arm, which are fixed to the ridges leading to the condyles of the
humerus, separating the muscles of the front and back of the limb,
and giving attachment to the fleshy fibres.

The internal is the stronger, and reaches as high as the coraco- an inner
Itrachialis muscle, from which it receives some tendinous fibres. *"
The brachialis anticus is attached to it in front, and the triceps
behind ; the ulnar nerve and the inferior profunda and anastomotic
vessels pierce it.

The external septum is thinner, and ceases at the deltoid muscle, an outer.
Behind it is the triceps ; and in front are the brachialis anticus
and the muscles of the forearm (supinator longus and extensor
carpi radialis longior) arising above the condyle of the humerus :
it is pierced by the musculo-spiral nerve and the accompanying
vessels.

Dissection. To follow the superior profunda vessels and the Dissection
iiiusculo-spiral nerve., the middle and outer heads of the triceps and'nervo.
should be cut across over them, and the fatty tissue should be
removed. The trunks of the artery and nerve are to be afterwards
followed below the outer head of the triceps to the front of the
humerus. The veins may be taken away.

To trace out the branches of the nerve and artery which descend
to the elbow and the anconeus muscle, the triceps is to be divided
along the line of union of the outer with the middle head.

The SUPERIOR PROFUNDA branch of the brachial artery (see Superior
fig. 19, p. 46) turns to the back of the humerus \Wth the musculo- arte^ry *
spiral nerve between the inner and outer heads of the triceps ; in
this position it supplies branches to the triceps and deltoid muscles, nes behind
and is continued onwards in the groove in the bone to the outer ^^^ hume-
part of the arm, where it divides in to its terminal offsets {anterior and
posterior). One of these, which is very small, courses on the musculo-
spiral nerve to the front of the elbow, anastomosing with the recurrent
radial branch ; while a larger one descends along the intermuscular
septum to the elbow, and joins the anastomotic and posterior inter-
osseous recurrent arteries.

Branches. Besides the terminal offsets of the vessel, a consider- supplies
able branch descends to the elbow in the inner head of the triceps, joins^a^nasto-

supplying the muscle, and communicating with the inferior profunda
and anastomotic branches of the brachial artery. One slender twig elbow;
accompanies a branch of the musculo-spiral nerve, and ends in the
anconeus muscle below the outer condyle of the humerus.

Two or more cutaneous offsets arise on the outer side of the arm, cutaneous
and accompany the superficial nerves, offsets.

The MUSCULO-SPIRAL XERVE (fig. 4,"* p. 15) is the largest trunk Muscuio-
of the posterior cord of the brachial plexus (p. 25), and is continued ^^^',^8°^
along the back and outer part of the limb to the hand. In the arm
the nerve winds with the superior profunda artery beneath the triceps
muscle. At the outer aspect of the arm it is continued between the to outer side
bracbialis anticus and supinator longus muscles to the external con- oft^earm-
dyle of the humerus, in front of which it divides into the radial and

DISSECTION OF THE FOREARM.

Branches.

Internal

cutaneous

branch.

Two exter-
nal cuta-
neous.

Branches to
the triceps,

ulnar
collateral
and an-
coneus,

brachialis
anticus and
muscles of
forearm.

Directions.

posterior interosseous nerves (fig. 37,^ and ^). The brachialis anticus
and supinator longus muscles are sometimes partly l)lended, and it
may be necessary in such cases to cut through some muscular fibres
to fully expose the last part of the nerve. The nerve gives
muscular branches and cutaneous offsets to the inner and outer
sides of the limb.

a. The internal cutatieous branch of the arm (fig. 20,^ also fig. 15,
p. 39) is of small size, and arises in the axillary space in common
with the branch to the inner head of the triceps ; it is directed across
the posterior boundary of the axilla to the inner side of the arm,
where it becomes cutaneous in the upper third, and is distributed as
before said (p. 43).

6. The external cutaneous branches, springing at the outer side of
the limb, are two in number ; they are distributed in the integuments
of the arm and forearm (pp. 42 and 57).

c. The muscular branches to the triceps are numerous, and supply
all three heads. One slender offset (often called the ulnar collateral
branch) for the inner head arises in common with the internal
cutaneous branch, and descends close to the ulnar nerve to enter the
muscular fibres at the lower third of the arm. Another long and
slender branch behind the humerus, appearing as if it ended in the
triceps, can be followed downwards to the anconeus muscle.

d. On the outer side of the limb the musculo-spiral nerve supplies
the brachialis anticus in part, and two muscles of the forearm, viz.,
supinator longus and extensor carpi radialis longior.

Directions. As the dissection of the arm has been completed as
far as the elbow, it will be advisable to keep moist the shoulder-
joint until it is examined with the other ligaments.

Section IV.

THE FRONT OF THE FOREARM.

Position of
the limb.

Surface of
the forearm,

Bony pro-
jections.

Line of the
wrist-joint.

Position. The limb is to be placed with the palm of the hand
uppermost ; and the marking of the surface and the projections of
bone are first to be noted.

Surface-marking. On the anterior aspect of the forearm are two
lateral depressions, corresponding with the position of the main
vessels. The external is placed over the radial artery, and inclines
towards the middle of the limb as it approaches the elbow. The
internal groove is evident only below the middle of the forearm,
and points out the place of the ulnar artery.

The bones (radius and ulna) are sufficiently near the surface to
be traced in their whole length : each ends below in a point on
either side of the wrist — the styloid process ; and that of the radius
is the lower. A transverse line separates the forearm from the
hand, and the articulation of the wrist is about three-quarters of an
inch above it.

SURFACE-MARKING OF FOREARM. 55

On each side of the palm of the hand is a large projection ; the surface of
external of these (thenar) is formed by muscles of the thumb, and P*^^ °^ ^^^®
the internal (hypothenar) by muscles of the little finger. At the
upper end of the latter the prominent pisiform bone is easily felt ;
and towards the outer side of the wrist, below the end of the radius,
the tuberosity of the scaphoid bone is to be recognised. Between
the muscular eminences is the hollow of the palm, which is pointed
towards the wrist. Two transverse lines are seen in the palm, but
neither reaches completely across it ; they result from the bending
of the fingers at the metacarpophalangeal articulations, but the
lower one is nearly half an inch above the three inner joints when
the fingers are extended.

The position of the superficial palmar arch of arteries is marked Position of
by the middle third of a line drawn across the palm from the root JrcJ^^
of the thumb when that digit is placed at a right angle to the hand ;
the deep palmar arch is about a finger's breadth nearer the wrist.

Transverse lines on the palmar aspects of the thumb and fingers Surface of
correspond to the articulations of the phalanges ; but while the *^® ^^s^^'
middle and lower ones are a little above the two interphalangeal
articulations, the upper one is fully half an inch below the metacarpo-
phalangeal joint.

Dissection. With the limb lying flat on the table, an incision Dissection
is to be carried through the skin along the middle of the front of the the^kh}!^
forearm, as far as an inch beyond the wrist ; and at its termination
a transverse one is to cross it. The skin is to be reflected carefully
from the front and back of the forearm, without injury to the
numerous superficial vessels and nerves beneath : and it should be
taken also from the back of the hand by prolonging the ends of
the transverse cut along each margin to a little beyond the knuckles.
The whole of the forefinger should have the integument removed
from it, in order that the nerves may be followed to the end.

The superficial vessels and nerves can be now traced in the fat : Seek the
they have the following position, and most of them have been partly ^"Ss^an(i
dissected : — along the inner side, with the ulnar veins, is the con- nerves in
tinuatiou of the internal cutaneous nerve ; and near the wrist there
is occasionally a small offset from the ulnar nerve. On the outer
side, with the radial vein, is the superficial part of the musculo-
cutaneous nerve.

Close to the hand, in the centre of the forearm, and inside the
tendon of the flexor carpi radialis, which can be rendered tense by
extending the wrist, the small palmar branch of the median nerve
should be sought beneath the fat. On the ulnar artery, close out-
side the pisiform bone, a small palmar branch of the ulnar nerve is
to be looked for.

Near the middle of the back of the forearm the large external behind,
cutaneous branch of the musculo-spiral nerve is to be traced onwards ;
and oftsets are to be followed to this surface of the limb from the
nerves in front on either side.

On the posterior part of the hand is a plexus of superficial veins, and on the
Winding back below the ulna is the dorsal branch of the ulnar ^d^^^^^^^

DISSECTION OF FRONT OF FOREARM.

Subcuta-
neous veins

plexus on
the hand ;

radial ;

ulnar,

and poste-
rior :

median.

Superficial
nerves of
forearm

and back of
hand are-

internal
cutaneous.

exteiTial
cutaneous ;

nerve ; and lying along the outer border of the hand is the radial
nerve ; these should be traced to the fingers.

Cutaneous Veins. The superficial veins are named median,
■ radial, and ulnar, from their position in the limb.

Dorsal plexus of the hand. This network receives the super-
ficial veins from both surfaces of the fingers ; and from it, on the
outer and inner sides, the radial and posterior ulnar veins proceed.

The radial vein begins in the outer part of the plexus above
mentioned, and in some small radicles at the back of the thumb.
It is continued along the forearm, at first behind and then on the
outer border as far as the elbow, where it gives rise to the cephalic
vein by its union with the outer branch of the median vein (fig. 16,
p. 40). In many bodies a considerable branch passes from the
lower part of the radial vein to join the median vein on the front of
the forearm.

The ulnar veins (fig. 16) are anterior and posterior, and occupy
the front and back of the limb.

The anterior begins near the wrist by the junction of small roots
from the hand, and runs on the inner part of the forearm to the
elbow, where it opens either into the median-basilic or posterior
ulnar vein.

The posterior ulnar vein arises from the inner part of the dorsal
plexus of the hand, and is continued along the back of the forearm
nearly to the elbow ; here it bends forward to join the inner branch
of the median and form the basilic vein.

The MEDIAN vein takes origin near the wrist by small branches
which are derived from the palmar surface of the hand. It is
directed along the centre of the forearm nearly to the elbow, and
there divides into median-basilic and median-cephalic, which unite,
as l)efore seen, with the radial and ulnar veins. At its point of
bifurcation the median receives a large communicating branch from
the deep veins l)eneath the fascia.

Cutaneous Nerves (fig. 15, p. 39, and fig. 23, p. 57). Some of
the superficial nerves of the forearm are continued from the arm,
those on the inner side from the large internal cutaneous nerve and
those on the outer from the lower external cutaneous branch of the
musculo-spiral and the musculo-cutaneous. On the fore part of the
limb there is occasionally a small offset of the ulnar nerve near the
wrist. On the back of the hand is the termination of the radial
nerve, together with the dorsal branch of the ulnar nerve.

The internal cutaneous nerve (p. 49) is divided into two.
The anterior branch extends on the front of the forearm as far as the
wrist, and supplies the integuments on the inner half of the anterior
surface. Near the wrist it communicates sometimes with a cutaneous
offset from the ulnar nerve (fig. 15). The posterior branch continues
along the back of the forearm (ulnar side) to the lower part (fig. 23).

The musculo-cutaneous nerve (cutaneous part, p. 50) is pro-
longed on the radial border of the limb to the ball of the thumb,
over which it terminates in cutaneous ofi'sets. Near the wrist the
nerve is placed over the radial artery, and some twigs pierce the

CUTANEOUS NERVES.

fascia to ramify on the vessel, and supply the carpal articulations.
A little above the middle of the forearm the nerve sends back-
wards a branch to the posterior aspect, which reaches nearly to
the wrist, and communicates with the radial and the following
cutaneous nerve (fig. 23).

The LOWER EXTERNAL CUTANEOUS BRANCH OF THE MUSCULO- external

SPIRAL NERVE (p. 42) descends along the hinder part of the fore- ^ugc^JJ,"'' °*^

spiral ;

Supra-acroiuial.

Circumflex.

Internal cutaneous branch
of musculo spiral.

Intercosto humeral-

Posterior branch of internal
cutaneou

Dorsal branch of ulnar.

Ui)pei- external cutaneous branch of
musculo-spiral.

Lower external cutaneous branch of
mu.sculo-spiral.

Posterior branch of musculo-
cutaneous.

Radial.

Branches of ulnar and median nerves
from anterior aspect.

Fig. 23.— Nerves of the Back of the Akm.

arm as far as the wrist. Near its termination it joins the preceding
nerve (fig. 23).

The RADIAL NERVE ramifies in the integmnent of the Ijack of radial nerve,
the hand and some of the digits. It becomes cutaneous at the
outer border of the forearm in the lower third, and, after giving
some filaments to the posterior aspect of the limb, divides into two
branches (fig. 23) : —

One (external) is joined by the musculo-cutaneous nerve, and is ending by
distributed on the radial border and the ball of the thumb.

The other branch (internal) supplies the remaining side of the internal

DISSECTION OF FRONT OF FOREARM.

which
supply
digits ;

and branch
of ulnar
nerve to
back of
hand and
fingers.

Extent of
nerves on
fingers.

Deep fascia
of forearm :

thumb, both sides of the next two digits, and half the ring finger ;
so that the radial nerve distrilnites the same numljer of digital
branches to the dorsum as the median nerve furnishes to the palmar
surface. This portion of the radial nerve communicates with the
musculo-cutaneous and ulnar nerves ; and the offset to the con-
tiguous sides of the ring and middle fingers is joined by a twig from
the dorsal branch of the ulnar nerve.

The DORSAL BRANCH OF THE ULNAR NERVE (fig. 23) gives offsets

to the rest of the fingers and the back of the hand. Appearing by the
styloid process of the ulna, it joins the radial nerve in an arch across
the back of the hand, and is distributed to both sides of the little
finger, and to the ulnar side of the ring finger ; it communicates
with the part of the radial nerve furnished to the space between
the ring and middle fingers ; and sometimes it supplies this space
entirely.

The dorsal digital nerves are much smaller than those on the
palmar aspect, and cannot be followed on the fingers farther than
the base of the second phalanx. On the sides of the finger each
communicates with an offset from the palmar nerve.

The APONEUROSIS of the forearm is continuous with the similar
investment of the arm. It is of a pearly white colour, and is formed
of fibres which cross obliquely. The membrane is thicker behind

at the
wrist;

posterior

annular

ligament.

Take away

nerves, and
veins.

Clean out
hollow of
elbow.

At the upper part it receives prolongations from the tendon of the
l^iceps in front, and of the triceps behind ; and it gives origin to
the muscles springing from the condyles of the humerus. Longi-
tudinal white lines indicate the position of deep processes (inter-
muscular septa), which separate the muscles, and give origin to
their fleshy fibres. On the back of the forearm the fascia is
attached to the hinder border of the ulna, and to the margins of a
triangular surface at the upper end of that l)one, which is left
subcutaneous.

At the wrist the fascia joins the anterior annular ligament ; and
near that band the tendon of the palmaris longus pierces it, and
receives a sheath from it. Close to the pisiform bone there is an ■
aperture through which the ulnar vessels and nerve enter the fat of
the hand. Behind the wrist it is thickened by transverse fibres,
giving rise to the posterior annular ligament ; but on the back
of the hand and fingers the fascia becomes very thin.

Dissection. The skin is now to be replaced on the back of the
forearm and hand, in order that the denuded parts may not become
dry. Beginning the dissection on the anterior surface of the limb,
let the student divide the aponeurosis as far as the wrist, and take
it away with the cutaneous vessels and nerves, except the small
palmar cutaneous offsets of the median and ulnar nerves near the
hand. In cleaning the muscles it will be impossible to remove the
aponeurosis from them at the upper part of the forearm without
cutting the muscular fibres.

In front of the elbow is the hollow, already partly dissected,
between the two masses of muscles arising from the inner and outer

DISSECTION OF FRONT OF FOREARM.

sides of the humerus. The space should he caiefuUy cleaned, so as
to display the hrachial
and forearm vessels, the
median nerve and
hranches, the musculo -
spiral nerve, and the re-
current radial and ulnar
arteries.

In the lower half of
the forearm a large artery,
radial. Is to be laid bare
along the outer side of
the tendon of the flexor
carpi radialis ; and at the
inner side, close to the
annular ligament, the
trunk of the ulnar artery
\vill be recognised as it
omes superficial. These
~^els and their branches
aould be carefully
.leaned ; and the adjoining
muscles may be fixed with
titches to prevent their
placement.

rhe anterior annular
, anient of the wrist,
vhich arches over the
tendons passing to the
hand, is next to be de-
fined. This strong band
is at some depth from
the surface ; and while
the student removes the
fibrous tissue superficial
to it, he must take care
of the small branches of
the median and ulnar
nerves to the palm of
the hand. The ulnar
vessels and nerve (covered
by an expansion connected
with the tendon of the
flexor carpi ulnaris internal
to the pisiform bone) pass
over the ligament, and
will serve as a guide to
its depth.

Hollow in front of

Define
anterior
annular
ligameut.

Fig. 24.— Superficial Vikw of the Fork-
arm (QcAis's "Arteries").

1. Radial artery, with its nerve outside.

2. Ulnar artery and nerve.

3. Pronator teres.

4. Flexor carpi radialis.

5. Palniaris lougus.

6. Flexor siiblimis digitorum.

7. Flexor carpi ulnaris.

8. Supinator longus.
Biceps.

9- liiceps. Hollow in

Jt . front of the

THE ELBOW (fig. 25). This hoUow is situate between the inner ^ibow:

DISSECTION OF FRONT OF FOREARM.

boundaries ;

contents of
the space

and their
position to
one another

lymphatic
glands.

Superficial
group
contains
five muscles,

Pronator
teres:

origin
by two
heads :

insertion ;

relations ;

and the outer muscles of the forearm, and is triangular in shape,
with the wider part towards the humerus. It is bounded on the
outer side by the supinator longus muscle, and on the inner side
by the pronator teres. The aponeurosis of the limb is stretched
over the space ; and the bones, covered by the brachialis anticus
and supinator brevis, form the deep boundary.

Contents. In the hollow are lodged the termination of the
brachial artery, with its veins, and the median nerve ; the musculo-
spiral nerve ; the tendon of the biceps muscle ; and small recurrent
vessels, with much fat.

These several parts have the following relative position : — The
tendon of the biceps is directed towards the outer boundary to
reach the radius ; and on the outer side, concealed by the supinator
longus muscle, is the musculo-spiral nerve. Nearly in the centre
of the space are the brachial vessels and the median nerve, the
nerve being internal ; but as the artery is inclined to the outer
side of the limb, they soon become distant from one another about
half an inch. The brachial artery divides here into two trunks,
radial and ulnar ; and the recurrent radial and ulnar branches
appear in the space, the former on the outer, and the latter on
the inner side.

Two or three lymphatic giands lie on the sides of the artery,
and one below its point of splitting.

Muscles on the Front of the Forearm (fig. 24). The
muscles on the front of the forearm are divided into a superficial
and a deep group.

In the superficial group there are five muscles, which are fixed
to the inner condyle of the humerus by a common tendon, and lie
in the undermentioned order from the outer to the inner side : —
(1) pronator radii teres, (2) flexor carpi radialis, (3) pal maris longus,
(4) flexor carpi ulnaris ; and deeper and larger than any of these
is (5) the flexor sublimis digitorum.

The deep group will be met with in a subsequent dissection
(p. 67).

The PRONATOR RADII TERES (fig. 24,") arises from the inner condyle
of the humerus l)y the common tendon, from the ridge above the
condyle by fleshy fibres (fig 17, p. 44), from the fascia over it, from
the septum between it and the flexor carpi radialis, and l)y a second
tendinous slip from the inner edge of the coronoid process of the
ulna. It is inserted by a flat tendon into an impression, an inch in
length, on the middle of the outer surface of the radius (fig. 36, p. 86).

The muscle is superficial except at the insertion, where it is
covered by the radial artery, and some of the outer set of muscles,
viz., supinator longus. and radial extensors of the wrist. The
pronator forms the inner boundary of the triangular space in front
of the elbow ; and its inner border touches the flexor carpi radialis.
By gently separating the muscle from the rest, it will be found to
lie on the brachialis anticus, the flexor sublimis digitorum, and
the ulnar artery and the median nerve, the small deep head of
origin intervening between the artery and nerve.

MUSCLES ON FRONT OF FOREARM.

Action. The pronator assists in bringing forwards the radius use on
over the ulna, so as to pronate the hand. When the radius is fixed,
the muscle raises that bone towards the humerus, bending the and elbow,
elbow -joint.

The FLEXOR CARPI RADiALis (fig. 24, "*) takes its origin from the Radial
common tendon, from the aponeurosis of the limb, and from the thg^^gt
intermuscular septum on each side of it. The tendon of the muscle,
becoming free from fleshy fibres about the middle of the forearm,
passes through a groove in the trapezium, in a special sheath at the
outer side of the anterior annular ligament, to be inserted mainly

Triceps.

Flexor sublimis digitorum.

Flexor carpi ulnaris.

Flexor longus poUicis.

Brachialis anticus.
Pronator radii teres.

Biceps.
Supinator brevis.

Supinator longus.

Fig. 25. — The Radius axd Ulna from the Front.

into the base of the metacarpal bone of the index finger, and by a
slip into that of the middle finger.

The muscle rests chiefly on the flexor sublimis digitorum ; but The muscle
near the wrist it lies over the flexor longus pollicis, — a muscle of ficiai,
the deep group. As low as the middle of the forearm the flexor
carpi radialis corresponds externally with the pronator teres, and
below that with the radial artery, to which its tendon is taken as
the guide. The ulnar border is in contact at first with the palmaris iJ^^dm"**^
longus muscle, and for about two inches above the wrist with the artery,
median nerve.

Action. The hand being free, the muscle first flexes the wrist- Use on wrist
joint, inclining the hand somewhat to the radial side ; and it will ^ ^^'

DISSECTION OF FRONT OF FOREARM.

Long palmar
muscle

lies over
annular
ligament
and joins
fascia of
palm;

assi&t in bringing forwards the lower end of the radius in pronation.
Still continuing to contract, it bends the elbow.

The PALMARis LONGUS (fig. 24,^) is sometimes absent, or it
may present great irregularity in the proportion between the fleshy
and tendinous parts. It arises, like the preceding muscle, from
the common tendon, the fascia, and the intermuscular septa. Its
slender tendon is continued along the centre of the forearm ; and
piercing the aponeurosis, it passes over the annular ligament to end
in the palmar fascia, sending a slip to the abductor muscle of the
thumb.

The palmaris is situate between the flexor carpi radialis and
iilnaris, and rests on the flexor sublimis digitorum.

Action. Rendering tense the palmar fascia, the palmaris will

Flexor carpi
ulnaris :
origin by
two heads ;

insertion ;

adjacent
parts ;

Course and
extent of
the radial
artery.

Situation in
the forearm.

The FLEXOR CARPI ULNARIS (fig. 24,7) aHses by a narrow slip
in common with the other muscles from the inner condyle of the
humerus, from the intermuscular septum between it and the flexor
sublimis digitorum, and by a broad aponeurosis from the inner
margin of the olecranon and the posterior border of the ulna for the
upper two-thirds of its length (fig. 36, p. 86). The fibres pass down-
wards and forwards to a tendon on the anterior aspect of the muscle in
the lower half, some joining it as low as the wrist. The tendon is
inserted into the pisiform l)one, from which fibrous bands pass on
to the hook of the unciform and to the base of the fifth metacarpal
bones representing the distal part of the tendon (the pisi-imciform
and pisi-metacarpal ligaments). Also a process passes inwards from
the tendon near its insertion on to the face of the anterior annular
ligament covering over the ulnar artery and nerve.

One surface of the muscle is in contact with the fascia ; and its
tendon, which can be felt readily through the skin, serves as the
guide to the ulnar artery. To its radial side are the palmaris and
flexor sublimis digitorum muscles. When the attachment to the
inner condyle has been divided, the muscle will be seen to conceal
the flexor profundus digitorum, the ulnar nerve, and the ulnar
vessels ; between the attachments to the condyle and the olecranon
the ulnar nerve enters the forearm.

Action. The wrist is bent, and the hand is drawn inwards by
the contraction of the muscle.

The RADIAL ARTERY (fig. 24,1) jg one of the vessels derived
from the bifurcation of the brachial trunk, and extends to the palm
of the hand. It is placed first along the outer side of the forearm
as far as the end of the radius ; next it winds backwards below the
extremity of that bone ; and finally it enters the palm of the hand
through the first interosseous space. In consequence of this cir-
cuitous course, the artery will be found in three different dissections,
viz., the front of the forearm, the back of the wrist, and the palm
of the hand.

I7i the front of the forearm. In this region of the limb the position
of the artery will be marked on the surface by a line from the
centre of the hollow of the elbow to the fore part of the styloid

RADIAL ARTERY. 63

process of the radius. This vessel is smaller than the ulnar artery,
though it appears in direction to be the continuation of the brachial
trunk. It is partly deep and partly superficial ; and where it is
superficial, it can be felt beating as the pulse near the wrist during life.

In its ujyper half the vessel is placed under cover of the supinator Relations to
longus {^) ; and it rests successively on the follo^^dng muscles : — the SS^uppeV
tendon of the biceps {^), the fleshy supinator brevis, the pronator ^^^^ •
teres (•"'), and part of the thin, radial origin of the flexor sublimis (^).

In its lower half the artery is superficial, being covered only by in lower
the integuments and the deep fascia. Here it is placed in a hollow ^^^''
between the tendons of the supinator longus (^) and flexor carpi
radialis (•*), and it lies, in this part, from above down on the origin
of the flexor sublimis, on two muscles of the deep group, viz., flexor
longus pollicis and pronator t^uadratus, and lastly on the end of
the radius.

Veins. Yente comites lie on the sides, with cross branches over to veins ;
the artery.

Nerve. The radial nerve is on the outer side of the artery in the to nerve,
upper two-thirds of the forearm, but is separated from the vessels
by a slight interval near the elbow. In the lower third the nerve
passes backwards and becomes superficial behind the tendon of the
supinator longus.

Branches. The radial artery in this part of its course furnishes Branches :
many unnamed muscular and cutaneous offsets, and three named
branches, viz., recurrent radial, superficial volar, and anterior carpal,

a. The radial recurrent (fig. 24) is the first branch, and supplies radial re-
the muscles on the outer side of the limb. Its course is almost <^'^"^'** •
transverse to the supinator longus, beneath which it terminates in
that muscle and the two radial extensors of the wrist. One offset
ascends beneath the supinator, and anastomoses with the superior
profunda branch of the brachial artery.

h. The superficial volar branch (fig. 27, c, p. 72) is very variable superficial
in size, and arises near the lower end of the radius. It is directed ^^ ^ '
towards the palm of the hand, across or through the mass of
muscles in the ball of the thumb ; and it either ends in those
muscles, or joins the superficial palmar arch.

c. The anterior carpal branch is very small, and will be seen in anterior
the examination of the deep muscles. Arising rather above the ^"^ '
end of the radius, it passes transversely inwards at the lower border
of the pronator quadratus, and anastomoses with a similar branch
from the ulnar artery. From the arch thus formed offsets are given
to the carpus.

Peculiarities of the radial artery. Sometimes the radial arises high in the Variations
arm, and its course then is close to the brachial artery, along the edge of the of the
biceps muscle ; and in passing the bend of the elbow it is occasionally sub- ^^
cutaneous, i.e. , above the deep fascia, and liable to injury in venesection. In
the forearm the artery may likewise be subcutaneous, and superficial to the
supinator longus muscle.

Dissection. To bring into ^-iew the flexor subUmis digitorum. Dissection
the flexor carpi radialis and palmaris longus must be cut through gubUmis.

DISSECTION OF FRONT OF FOREARM.

Superficial
flexor of
fingers :
origin from
three bones
of limb ;

insertion ;
relations ;

use on
fingers,

on elbow
and wrist.

Ulnar artery
ends in palm
of hand.

Course in
upper half

and rela-
tions to
muscles :

in lower
half;

relations to
muscles :

near the inner condyle of the humerus, and turned to one side.
Small branches of the ulnar artery and median nerve may be seen
entering the under-surfaces of those muscles. For the present the
pronator teres may be left uncut.

The FLEXOR SUBLIMIS DiGiTORUM (flexor perforatus, fig. 24, 6) is
the largest of the superficial muscles, and is named from its position
to another flexor in the deep set. It arises in common with the
foregoing muscles from the inner condyle of the humerus and the
intermuscular septa, also from the internal lateral ligament of the
ell)OW-joint and the inner margin of the coronoid process of the
ulna, and by a thin layer from the oblique line of the radius, as well
as frequently from the anterior border of that bone for a distance of
one or two inches below the insertion of the pronator teres (fig. 25).
Below the middle of the forearm the muscle ends in four tendons,
which are continued beneath the annular ligament and through the
hand, to be inserted into the middle phalanges of the fingers (fig. 32,
p. 78), after being perforated by the tendons of the deep flexor.

The flexor sublimis is in great part concealed by the other
muscles of the superficial group ; and the radial vessels lie on the
attachment to the radius. Along the inner border is the flexor
carpi ulnaris, with the ulnar vessels and nerve. The tendons of
the muscle are arranged in pairs before they pass beneath the
annular ligament of the wrist, the middle and ring finger tendons
being anterior, and those of the index and little finger posterior in
position. On dividing the condylar and coronoid attachments the
muscle will be seen to cover two deep flexors (flexor profundus
digitorum and flexor longus pollicis), the median nerve, and the
upper part of the ulnar artery.

Action. The flexor bends first the middle and then the proximal
joints of the fingers ; but when the first phalanges are fixed by the
extensor of the fingers, the superficial flexor moves the second
phalanges alone.

After the fingers are bent the muscle will help in flexing the
wrist and elbow-joints.

The ULNAR ARTERY (fig. 26, g) is the larger of the two branches
coming from the bifurcation of the brachial trimk, and is directed
along the inner side of the limb to the palm of the hand, where it
forms the superficial palmar arch, and supplies most of the fingers.
In the forearm the vessel has an arched direction ; and its depth
from the surface varies in the first and last parts of its course.

In the upper half the artery is inclined obliquely inwards from
the centre of the elbow to the inner side of the limb. It courses
between the superficial and deep muscles, being covered by the
pronator teres, flexor carpi radialis, palmaris longus, and flexor
sublimis. Beneath it lies on the brachialis anticus for a short
distance, and afterwards on the flexor profundus (c).

In the lower half it has a straight course to the pisiform bone,
and is covered by the integuments and fascia, and by the flexor
carpi ulnaris. To the outer side are the tendons of the flexor
sublimis. Beneath it is the flexor profundus (c).

ULNAR ARTERY.

venae
comites ;

nerves in
relation :

Veins. Two veins ac-
company the artery, and
are united across it at
intervals.

Nerves. The median
nerve Q) lies to the inner
side of the vessel for about
an inch, but then crosses
over it to gain the outer
side, the coronoid head of
the pronator teres being
placed between the two.
Rather above the middle
of the forearm the ulnar
nerve (^) reaches the
artery, and continues
thence on the inner side ;
and a small branch (»),
sending twigs around the
artery, courses on it to
the palm of the hand.

On the annular liga-
me^it the artery has passed
through the fascia, and
lies close to the pisiform
bone. The ulnar nerve,
with its palmar branch,
still accompanies the ves-
sel on the inner side.

Brandies. The greater
number of the offsets of
the artery are distributed
to the muscles. Its named
branches are the follow-
ing :—

a. The anterior ulnar
recurrent branch fre-

Fir 26 —Dissection of the Deep Muscles of the Forearm, and op

^ '■ THE Vessels A.B Nerves between the Two Groups of Muscles

(Illustrations of Dissections).

anterior and

Muscles :

A. Pronator teres.

B. Flexor longus pollicis.

Flexor profundus digitorum.
Pronator quadratus.
Flexor carpi ulnaris.

Arteries :
Radial trunk.
Superficial volar branch.
Uluar trunk.

d. Its posterior recurrent branch.

e. Anterior interosseous.
/. Median artery.

g. Brachial trunk.
Nerves :

1. Median.

2. Anterior interosseous.

3. Cutaneous palmar branch.

4. Ulnar trunk.

5. Cutaneous palmar branch of
ulnar.

D.A.

DISSECTION OF FRONT OF FOREARM.

posterior
recurrent,

interos-
seous.

carpal,

and meta-
carpal.

quently arises in common with the next, and ascends on the
brachial is anticus muscle, to join the branch of the anastomotic
artery beneath the pronator teres. It gives offsets to the contiguous
muscles.

h. The posterior ulnar recurrent branch (d), of larger size than
the anterior, is directed beneath the flexor sublimis muscle to the
interval between the inner condyle and the olecranon. There it
passes with the ulnar nerve between the attachments of the flexor
carpi ulnaris, and joins the ramifications of the inferior profunda
and anastomotic arteries on the inner side of the ell)ow-joint. Some
of its offsets enter the muscles, and others supply the articulation
and the ulnar nerve.

c. The interosseous artery is a short thick trunk, which is
directed backwards towards the interosseous membrane, and divides
into anterior and posterior branches, which will be afterwards
followed.

d. The carpal branches (anterior and posterior) ramify on the
front and back of the carpus, on which they anastomose with
corresponding offsets of the radial artery, and form arches across
the wrist.

e. The metacarpal branch arises from the artery near the lower
end of the ulna, and runs along the metacarpal bone of the little
finger, of which it is the inner dorsal l)ranch.

The origin

and course
may vary.

Peculiarities of the ulnar artery. The origin of the artery may be trans-
ferred to any point of the main vessel in the arm or axilla. In one instance
R. Quain found the ulnar artery arising between two and three inches below
the elbow.

When it begins higher than usual, it is generally superficial to the flexor
muscles at the bend of the elbow, but beneath the aponeurosis of the forearm,
though sometimes it is subcutaneous with the supeificial veins.

Ulnar nerve
in the fore-
arm.

Its branches
are

to elbow,
joint ;

to two
muscles of
forearm ;

cutaneous
branch of
palm of
hand :

The ULNAR NERVE (fig. 26, ^) enters the forearm between the
attachments of the flexor carpi ulnaris to the olecranon and inner
condyle of the humerus. Under cover of that muscle the nerve
reaches the ulnar artery somewhat above the middle (in length) of
the forearm, and is continued on the inner side of the vessel to the
hand. On the annular ligament the nerve is rather deeper than the
artery. It gives off the following branches : —

a. Articular nerves. In the interval between the olecranon
and the inner condyle, slender filaments are furnished to the
joint.

b. Muscular branches arise from the nerve near the elbow, and
supply the flexor carpi ulnaris and the inner half of the flexor
profundus digitorum.

c. Cutaneous nerve of the forearm and hand (fig. 15, p. 39). A
small palmar branch (5) arises about the middle of the forearm, and
descends on the ulnar artery, sending twigs around that vessel,
to end in the integuments of the palm of the hand ; sometimes a
cutaneous offset perforates the aponeurosis near the wrist, and
joins the internal cutaneous nerve.

NERVES OF THE FOREARM. 67

d. The dorsal cutaneous nerve ofthehand (fig. 23, p. 57) leaves the cutaneous
trunk about two inches above the end of the ulna, and passes obliquely ^^^ of
backwards beneath the flexor carpi ulnaris ; perforating the aponeu- hand,
rosis, it is distributed on the back of the hand and fingers (p. 58).

The MEDIAN NERVE (fig. 26, 1) leaves the hollow of the elbow Median
between the heads of the pronator teres, and runs in the middle ?J"|f ^^^
line of the limb to the hand. It is placed beneath the flexor two groups
sublimis as low as two inches from the annular ligament, where it °^ ^^^^^^^s,
becomes superficial along the outer border of the tendons of that
muscle. Lastly, the nerve passes beneath the annular ligament to
the palm of the hand, and its position in this part may be marked
on the surface by the tendon of the palmaris longus. It supplies
the muscles on the front of the forearm, and furnishes a cutaneous
offset to the hand.

Muscular offsets leave the trunk of the nerve near the elbow, and it supplies
are distributed to all the superficial muscles except the flexor carpi *^® ^^^"^
ulnaris ; in addition the nerve supplies the deep layer of muscles except one
through its interosseous branch (p. 69), except the inner half of *"^ * ^*^'
the flexor profimdus digitorum.

The cutaneous palmar branch (^) arises in the lower fourth of the and a branch
forearm ; it pierces the fascia near the annular ligament, and crosses {j^,5J'™ °^
over that band to reach the palm (fig. 15, p. 39).

The RADIAL Nl5RVE is the smaller of the two branches into which Radial nerve
the musculo-spiral divides at the elbow. This nerve is placed along ^^ forearm,
the outer border of the limb, under cover of the supinator longus
and on the outer side of the radial artery, to the junction of the
middle and lower thirds of the forearm, where it becomes
cutaneous at the posterior border of the supinator tendon. It finally it ends on
divides into two branches, which are distributed on the dorsum of ^^^ °^ *^®
the hand and digits (fig. 23). No muscular offset is furnished by
the nerve.

Dissection (fig. 26). To examine the deep layer of muscles it Dissection
will be necessary to draw well over to the radial side of the forearm ^^ **®®P
the pronator teres, to detach the flexor sublimis from the radius, and
to remove its fleshy part. A thin layer of fascia, which is most
distinct near the wrist, is to be taken away ; and the anterior
interosseous vessels and nerve, which lie on the interosseous mem-
brane, and are concealed by the muscles, are to be traced out.

Over the bones at the lower end of the forearm the arch of the show carpal
anterior carpal arteries may be defined. *'"*'^-

Deep Group of Muscles. There are three deep muscles on the Three mus-
front of the forearm. One, covering the ulnar, is the deep flexor of ^^^ *get^^
the fingers ; a second rests on the radius, the long flexor of the
thumb ; and the third is the pronator quadratus, which lies beneath
the other two, over the lower ends of the bones.

The flexor profundus digitorum (flexor perforans, fig. 26, c) Deep flexor
arises from the anterior and inner surfaces of the ulnar for three- of ^^g^i^ '•
fourths of the length of the bone (fig. 25, p. 60), from the inner half °"Sin .
of the interosseous ligament for the same distance, and from the
aponeurosis of the flexor carpi ulnaris. The muscle has a thick

f 2

DISSECTION OF FRONT OF FOREARM.

insertion :

parts
around it

use on
fingers and
wrist.

How fingers
are bent.

Long flexor
of thumb :

origin

insertion ;
pai-ts above

and beneatii
it:

Pronator
quadratus

is deep in
position ;

Anterior in-
terosseous
artery.

fleshy belly, and ends in tendons which, passing beneath the
annular ligament, are inserted into the last phalanges of the fingers
(fig. 32, p. 78). The portion of the muscle furnishing the tendon
to the index finger is separated from the rest by a layer of areolar
tissue, and arises chiefly from the interosseous membrane.

Lying over the muscle are the ulnar vessels and nerve, the
superficial flexor of the fingers, and the flexor carpi ulnaris. The
deep surface rests on the ulna and the pronator quadratus muscle.
The outer border touches the flexor longus pollicis and the anterior
interosseous vessels and nerve.

Action. The muscle bends the joints of the fingers and the wrist ;
but it does not act on the last phalanx till after the second has been
moved by the flexor sublimis.

The fingers are usually bent in the following order : — firstly, the
articulation between the first (proximal) and the middle phalanges ;
secondly, the last phalangeal joint ; and thirdly, the metacarpo-
phalangeal.

The FLEXOR LONGUS POLLICIS (fig. 26, b) arises from the anterior
surface of the radius below the oblique line (fig. 25), as low as the
pronator quadratus, and from the outer part of the interosseous
membrane ; it is also joined in most cases by a distinct slip arising
in common with the flexor sublimis digitorum either from the internal
condyle of the humerus or the coronoid process of the ulna. The
fleshy fibres descend to a tendon, which is continued beneath the
annular ligament, and is inserted into the last phalanx of the thimib.

The greater part of the muscle is covered by the flexor sublimis
digitorum ; and the radial vessels rest on it for a short distance
below. It lies on the radius and the pronator quadratus. To the
inner side is the flexor profundus digitorum.

Action. This muscle is the special flexor of the last joint of the
thumb, but it also aids in bending the other joints of that digit and
the wrist.

The PRONATOR QUADRATUS (fig. 26, d) is a flat muscle cover-
ing the lower fourth of the bones of the forearm. It arises from
the anterior surface of the ulna, where it is widened by a
somewhat linear and partly tendinous origin, and is inserted into
the fore and inner parts of the radius for about two inches (fig. 25).

The anterior surface is covered by the tendons of the flexor
muscles of the digits, and by the radial vessels ; and the posterior
surface rests on the radius and ulna with the intervening membrane,
and on the interosseous vessels and nerve. Along its lower border
is the arch formed by the anterior carpal arteries.

Action. The end of the radius is moved inwards over the ulna by
this muscle, and the hand is pronated.

The ANTERIOR INTEROSSEOUS ARTERY (fig. 26, e) is continued on
the front of the interosseous membrane between the two flexors or
in the fibres of the flexor profundus digitorum, till it reaches an
aperture in the membrane near the upper border of the pronator
quadratus. At that spot the artery turns from the front to the
back of the limb, and descends to the back of the carpus, where

DISSECTION OF THE HAND. 69

it ends by anastomosing with the posterior interosseous and carpal
arteries.

Branches. Numerous offsets are given to the deep muscles. Branches:

One long branch, median (/), accompanies the median nerve,
which it supplies, and either ends in the flexor sublimis, or is con-
tinued beneath the annular ligament to the palmar arch.

Above the middle of the forearm the medullary arteries of the medullary to
radius and ulna arise from the vessel. ® "^^'

Where it is about to pass through the interosseous membrane and carpal,
it furnishes twigs to the pronator quadratus ; and one branch is
continued beneath that muscle to anastomose with the anterior
carpal arteries.

The ANTERIOR INTEROSSEOUS NERVE (fig. 27, 2) is derived from Anterior

the median, and accompanies the artery of the same name to the n^rt^ends^
jironator quadratus muscle, the under-surface of which it enters, in pronator.
Branches are given by it to the flexor longus pollicis and to the outer
part of the flexor profundus digitorum muscles.

Dissection. The attachment of the biceps and brachialis anticus Dissection,
to the bones of the forearm may be now cleaned and examined.

The insertion of the brachialis anticus takes place by a broad thick insertion of
tendon, about an inch* in length, which is fixed into the inner and aJticus!^^
lower parts of the rough impression on the front of the coronoid
process of the ulna.

Insertion of the biceps. The tendon of the biceps is inserted into insertion of
the rough hinder part of the tuberosity of the radius, a bursa '^^^^*
separating it from the fore part of the prominence. Near its
attachment the tendon is twisted, so that the anterior surface be-
comes external. The supinator brevis muscle partly surrounds the
insertion.

Section V.

THE PALM OF THE HAND.

Dissection (fig. 27, p. 72). The digits should be well sepa- Dissection,
rated and fixed firmly to a board with tacks, and the skin reflected
from the palm of the hand by means of tico incisions. One is to be
carried along the centre of the palm from the wrist to the fingers ; Clean small
and the other is to be made from side to side at the termination of muscle,
the first. In raising the inner flap, the small palmaris brevis
muscle will be seen at the inner margin of the hand ; and its
insertion into the skin may be left till the muscle has been learnt.
In the fat the ramifications of the palmar branches of the median and ti-ace

1 , . 1 . T cutaneous

and ulnar nerves are to be traced. nerves.

The student slioidd remove the fat from the palmaris muscle, and Define the
from the strong palmar fascia in the centre of the hand ; and he fa^sda^
should ta,ke care not to destroy a fibrous band (transverse ligament)
which lies across the roots of the fingers. When cleaning the fat

DISSECTION OF THE HAND.

digital
vessels and

and expose

digital

sheaths.

Cutaneous

palmar

nerves,

one from
median,

the other
from ulnar.

Palmaris
brevis is a
cutaneous
muscle ;

Palmar
fascia.

Its central
part

ends in a
piece for
each finger,

and in the
skin.

Dissection.

Deep ending
of the j)ieces
of fascia.

from the palmar fascia he will recognise, opposite the clefts between
the fingers, the digital vessels and nerves, and must be especially
careful of two, viz., those of the inner side of the little finger and
outer side of the index finger, which appear higher up in the hand
than the rest, and are more likely to be injured. By the side of
the vessels and nerves to the fingers four slender luml:)ricales muscles
are to be exposed.

Lastly, the skin and the fat may be reflected from the thumb and
fingers by an incision along each, in order that the sheaths of the
tendons with the collateral vessels and nerves may be laid bare.

Cutaneous palmar nerves. Small twigs are furnished to the integu-
ment from both the median and ulnar nerves in the hand ; and two
branches descend from the forearm.

One is the offset of the median nerve (p. 67) which crosses the
annular ligament ; it extends to about the middle of the palm, and
is united with the palmar branch of the ulnar ; a few filaments are
furnished to the ball of the thumb.

The other palmar branch is derived from the ulnar nerve (p. 66),
and has been traced on the ulnar artery to the hand ; it is distributed
to the upper and inner part of the palm.

The PALMARIS BREVIS (fig. 28, h) is a small flat muscle, about an
inch and a half wide, the fibres of which are collected into separate
bundles. It arises from the palmar aponeurosis, and its fibres are
directed transversely to their insertion into the skin at the inner
border of the hand.

This muscle lies over the ulnar vessels and nerve. After it has
been examined it may be thrown inwards with the skin.

Action. It draws outwards and wrinkles the skin of the inner
side of the palm.

The PALMAR FASCIA or aponeurosis consists of a central and two
lateral parts ; but the lateral, which cover the muscles of the
thumb and little finger, are so thin as not to require a special
notice.

The central fart is a strong, white layer, which is pointed at the
wrist, but expanded towards the fingers, where it nearly covers the
palm of the hand. Above, the fascia receives the tendon of the
palmaris longus, and is connected to the annular ligament ; and
below, it ends in four processes, which are continued downwards,
one for each finger, to the sheaths of the tendons. At the point of
separation of the pieces from one another some transverse fibres are
placed, which arch over the lumbricalis muscle and the digital
vessels and nerve appearing at this spot. From the pieces of the
fascia a few superficial longitudinal fibres are prolonged to the
integument near the cleft of the fingers.

Dissection. Now follow one of the digital processes of the
fascia to its termination. First remove the superficial fibres, and
then divide the process longitudinally by inserting the knife
beneath it opposite the head of the metacarpal bone.

Ending of the processes. Each process of the fascia sends back-
wards an offset on each side of the tendons, wbich is fixed to the

THE ULNAR ARTERY. 71

deep ligament connecting together the heads of the metacarpal
bones, and to the edge of the metacarpal bone for a short distance.

The superficial transverse ligament of the fingers is a thin fibrous Transverse
band, which stretches across the roots of the four fingers, and is ['^Sbggjjf
contained in the fold of skin, forming the rudiment of a web
between them. Beneath it the digital nerves and vessels are con-
tinued onwards to their terminations.

Sheath of the flexor tendons. Along each finger the flexor tendons Sheath of
are retained in place against the phalanges by a fibrous sheath. ^^® tendons
Opposite the middle of the fii*3t and second phalanges the sheath is varies in
strengthened by a strong fibrous band {vaginal ligainent)^ which is thickness ;
almost tendinous in consistence, but opposite the joints it consists
of a thin membrane with scattered and oblique fibres. The has a syno-
sheath will be opened later on in the examination of the flexor ^^*^ ^'^'
tendons.

Dissection. The palmar fascia should next be taken away. On Dissection,
the removal of the fascia the palmar arch of the ulnar artery and
the median and ulnar nerves become apparent.

PaKMAR part of the UtNAR ARTERY (fig. 28). In the palm of superficial

the hand the ulnar artery di\ddes into two branches, superficial palmar
and deep. The larger — superficial — branch is directed towards the
muscles of the thumb, where it communicates with two offsets of
the radial trunk, ^^z., the superficial volar branch (c) and the
1 'ranch to the radial side of the forefinger (/). The curved part
(jf the artery, which lies across the hand, is named the superficial
palmar arch (d). Its convexity is turned towards the fingers, and position in
its position in the palm would be nearly marked by a line across ^^^ ^^^^ >
the hand from the cleft of the thimib.

The arch is comparatively superficial, being covered for the most relations,
part only l)y the integmnents and the palmar fascia ; but at the
inner border of the hand the palmaris brevis muscle (h) lies over it.
Beneath it are the flexor tendons and the lu-anches of the ulnar and
median nerves. Vense comites lie on its sides.

The deep or communicating branch of the ulnar artery (fig. 312, jj^gp
p. 77) passes backwards with the deep part of the ulnar nerve, ^'^^'^^J
l>etween the aVxluctor and short flexor muscles of the little
finger, to inosculate with the deep |)almar arch of the radial artery
(p. 80).

Branches. From the convexity of the superficial arch proceed
the digital arteries, and from the concavity some small offsets to
the palm of the hand.

The digital branches (g) are four in number, and supply both four digital
sides of the three inner fingers and one side of the index finger, branches:
The branch to the inner side of the hand and little finger is un-
divided ; but the others, lying over the three inner interosseous
spaces, bifurcate below to supply the contiguous sides of the corre-
sponding digits. In the palm these branches are accompanied by
the digital nerves, which they sometimes pierce.

Near the roots of the fingers they receive communicating branches these join
from offsets of the deep arch ; but the digital artery of the inner ^S^^arch ^^

DISSECTION OF THE HAKD.

side of the little finger has its communicating l^ranch about the
middle of the palm,
termination From the point of bifurcation the arteries extend along the sides
of the fingers ; and over the last phalanx the vessels of opposite

on the
fingers ;

Fig.

27.— Superficial Dissection of the Palm of the Hand
(Illustrations of Dissections).

Muscles :

a. Abductor pollicis.

c. Outer head of flexor

brevis.
D. Abductor transversus

pollicis.
H. Palmar is brevis.

Arteries :

a. Ulnar.
6. Radial.

c. Superficial volar branch.

d. Superficial palmar arch.

e. Branch uniting the arch

with /, the radial digital branch
of the forefinger.

g. Digital branches of the
superficial arch.

Nerves .
Ulnar, and

2, its two

digital branches.

3. Median, and 5, its digital
branches.

4. Branch of the median to
thumb-muscles.

5 (on the annular ligament).
Communicating branch from the
median to the ulnar.

sides unite in an arch, from the convexity of which ofi*sets proceed

to supply the ball of the finger. Branches are furnished to the

and arche.H finger and the sheath of the tendons ; and twigs are supplied to the

THE MEDIAN NERVE IN THE HAND. 73

I phalangeal articulations from small arterial arches on the bones,
an arch being close above each joint. On the dorsum of the last
phalanx is a plexus from which the nail pulp is supplied.

Palmar part of the ulnar nerve (fig. 27, i). The ulnar Ulnar nerve
nerve, like the artery, divides, on or near the annular ligament, into ^^^ ^ ^
a super jkial and a deep part.

The deep part accompanies the deep branch of the artery to the divides into
muscles, and will be dissected with that vessel (fig. 31). ®®^ ^"^

• The superficial part furnishes an oftset to the palniaris brevis superficial
muscle, and some filaments to the integument of the inner part of ^^ ^"
the hand, and ends in two digital nerves for the supply of both
sides of the little finger and half the next.

Digital nerves 0). The more • internal nerve is undivided, like Digital

ry T i • nerves are

the corresponding artery. two.

The other is directed to the cleft between the ring and little
fingers, and bifurcates for the supply, of their opposed sides ; in the
palm of the hand this branch is corrected with an offset (^) of the
median nerve.

Along the sides of the fingers the digital branches have the same
juTangement as those of the median nerve.

Palmar part of the median nerve (fig. 27,^). As soon as the Median
median nerve issues from beneath the annular ligament it becomes piie\ mus-^
enlarged and somewhat flattened, and divides into two nearly equal 5^.^?^*"^
parts for the supply of digital nerves to the thiunb and the remain-
ing two fingers and a half ; the outer part also furnishes a small
muscular branch to the ball of the thumb. The branches of the
nerve are covered by the fascia and the superficial palmar arch ;
and beneath them are the tendons of the flexor muscles.

a. The muscular branch (^) supplies the flexor brevis, the Branch to
abductor, and the opponens poUicis muscles. ^^^ ^^'

b. The digital nerves (•^) are five in number. Three of them are Five digital
undivided, and come from the external of the two pieces into which ^^^''^^ •
the trimk of the median splits. The other two spring from the

inner piece of the nerve, and are bifurcated, each supplying the
opposed sides of two fingers.

The first two nerves belong to the thumb, one on each side, and first two,
the outer one communicates with a ]:»ranch of the radial nerve.

The third is directed to the radial side of the index finger, and third,
gives a branch to the most external lumbrical muscle.

The fourth furnishes a nerve to the second lumbrical muscle, and fourth,
divides to supply the contiguous sides of the fore and middle
fingers.

The fifth also divides into two branches, which are distributed to fifth,
the opposed sides of the middle and ring fingers ; it communicates
with a branch of the ulnar nerve.

On the fingers. On the sides of the fingers the nerves are in front On the sides
of the arteries, and reach to the last phalanx, where they end in ^^g^.
filaments for the ball, and the pulp beneath the nail. In their
course downwards the nerves supply chiefly tegumentary branches, lateral
One of these (the dmsal branch) is directed backwards by the side of offsets.

DISSECTION OF THE HAND.

Dissection
of the flexor
tendons.

Divide

annular

ligament

and open
sheaths.

Superficial

flexor

tendons

in the hand
insertion :

slit for the
deep flexor.

Dissection.

Tendons of
deep flexor

the first phalanx, and, after uniting with the digital nerve on
the back of the finger, is continued to the dorsum of the last
phalanx.

Dissection. The tendons of the flexor muscles may next be
followed to their termination. To expose them, the ulnar artery
should be cut through below the origin of the deep Ijranch ; and the
superficial volar branch of the radial having been divided, the
palmar arch is to be thrown towards the fingers. The ulnar and
median nerves are also to be cut below the annular ligament, and
turned downwards.

A longitudinal incision is to be made through the centre of the
annular ligament without injuring the muscles that arise from it,

and the pieces of the ligament
are to be thrown to the sides.

Finally, the sheaths of the
fingers may be opened in order
to show 'the insertion of the
tendons.

Flexor Tendons. Beneath
the annular ligament the ten-
dons of the deep and superficial
flexors are surrounded by a large
and loose synovial membrane,
which projects upwards into the
forearm and downwards into the
hand, and sends an offset into
the digital sheath of the thumb,
and usually one into that of the
little finger (fig. 28). The syno-
vial sheath belonging to the ten-
don of the flexor longus poUicis
is often separate from the rest.

Flexor sublimis. The ten-
dons of the flexor sublimis are
superficial to those of the deep
flexor beneath the ligament ; and
all four are nearly on the same level, instead of Ijeing arranged in
pairs as in the forearm. After crossing the palm of the hand they
enter the digital sheaths (figs. 29 and 30) ; and each is inserted by two
processes into the margins of the middle phalanx, about the centre.
As it enters the sheath, the tendon of the flexor sublimis conceals
that of the flexor profundus ; but opposite the lower half of the
first phalanx it is split for the passage of the latter tendon.

Dissection. To see the tendons of the deep flexor and the lum-
brical muscles, the flexor sublimis must be cut throiTgh above the
wrist, and thrown towards the fingers. Afterwards the synovial
membrane and areolar tissue should be taken away.

Flexor profundus. At the lower border of the annular liga-
ment the tendinous mass of the flexor profundus is divided into four
pieces, though in the forearm only the tendon of the index finger is

28. — Synovial Sheaths op
THE Flexor Tendons.

FLEXOR TEXDONS.

distinct from the rest. From the ligament the four tendons are cross the
directed through the hand to the fingers ; and in their course they ^^°^
-^ origin to the small lumbricales muscles. At the root of the
_er each enters the digital sheath with a tendon of the flexor
liuiis, and having passed through that tendon, is inserted into the to their
~.^ of the last phalanx (fig. 30). insertioiu

Between both flexor tendons and the bones are short folds of short folds
the synovial membrane, one for each (vincula accessoria, ligartienta ^ ^^^

Fig. 29.

Figures of the Texdons and Short Muscles of one Finger,
WITH THE Sheath op the Flexor Tendons.

a. Extensor tendon, with interosseous {h) and lumbrical (c) muscles
joining it.

d. Tendo-n of flexor sublimis passing into its sheath, the thicker
parts of which are marked e and /.

brevia, fig. 30). By means of this each tendon is connected with flexor ten-
the capsule of the joint, and the lower part of the phalanx im-
mediately above the bone into which it is inserted. A thin fold
{ligamentum longum) will also be seen passing to the shaft of the
first phalanx.

The LUMBRICALES (fig. 31, I, p. 77) are four small muscular slips, Lumbrical
which « me from the tendons of the deep flexor near the annular ™"**^l**s =

DISSECTION OF THE HAND.

origin,
insertion,

relations,

and use.

Tendon of
long flexor
of thumb ;

its insertion.

Dissection
of deep
arch,

and of
muscles of
thumb and
little finger.

Five mus-
cles to
thumb.

Abductor :

attach-
ments,

relations,

and use.
Dissection.

ligament ; the outer two springing each from a single tendon, while
the inner two are connected each with two tendons. They are
directed to the radial side of the fingers, to be inserted into the ex-
panded extensor tendon on the dorsal aspect of the metacarpal phalanx
(fig. 30, c).

These muscles are concealed for the most part by the tendons
and vessels that have been removed ; but, as already seen, they are
subcutaneous for a short distance between the processes of the
palmar fascia.

Action. The lumbricales assist in bending the metacarpo-
phalangeal joints, and, by their insertion into the extensor tendons,
they straighten the interphalangeal joints.

Tendon of the flexor longus pollicis. Beneath the annular ligament
this tendon is external to the flexor profundus ; and in the hand it
inclines outwards between the outer head of the flexor brevis and
the adductor obliquus pollicis (fig. 31), to be inserted into the last
phalanx of the thumb. The common synovial membrane surrounds
it beneath the annular ligament, and sends a prolongation, as before I
said, into its digital sheath.

Dissection (fig. 31). The deep palmar arch with the deep
branch of the ulnar nerve, and some of the interosseous muscles,
will come into view if the flexor profundus is cut above the wrist,
and thrown with the lumbricales muscles towards the fingers ; but
in raising the tendons the student should preserve the fine nerves
and vessels entering the inner two lumbrical muscles.

The short muscles of the thumb and little finger are next to be
prepared. Some care is necessary in making a satisfactory separation
of the difterent small thumb-muscles ; but those of the little finger
are more easily defined.

Short Muscles of the Thumb (fig. 31). These are five in
number. The most superficial is the abductor pollicis (a) ; and
beneath it is the opponens pollicis (b), which will be recognised by
its attachment to the whole length of the metacarpal bone. To the
inner side of the last is the short flexor (c) ; below this and below
the tendon of the long flexor is the adductor obliquus (c') ; and the
wide muscle coming from the third metacarpal bone is the adductor
transversus (d).

The ABDUCTOR POLLICIS (a) is the most superficial muscle, and
is aljoiit an inch wide. It arises from the upper part of the annular
ligament on the outer side, and from the tuberosity of the scaphoid
bone ; and it is inserted into the base of the first phalanx of the
thumb at the radial margin, sending a slip to join the tendon of the
extensor longus pollicis.

The muscle is subcutaneous, and rests on the opponens pollicis ;
it is joined at its origin by a slip from the tendon of the palmaris
longus, and often by one from the extensor ossis inetacarpi pollicis.

Action. The abductor pollicis moves the thumb in the direction
of its radial l)order away from the index finger.

Dissection. The opponens pollicis will be seen on cutting
through the abductor. To separate the muscle from the sliort

SHORT MUSCLES OV THE THUMB.

flexor on the inner side, the student should begin near the head of
the metacarpal bone, where there is usually a slight interval.

The OPPOXENS POLLicis (b) arises from the annular ligament Opponens
beneath the preceding, from the tubercle of the scaphoid beneath JjJSftacarpai

bone

Fig. 31.

-Deep Dissection of the Palm of
(Illustrations of Dissections).

the Hand

Muscles .

Abductor pollicis.
Opponens pollicis.
Flexor brevis pollicis.
Adductor obliquus

pol-

transversus

c'.

licis.

D. Adductor
pollicis.

E. Abductor minimi digiti.

f. Flexor brevis minimi
digiti.

G. Opponens minimi digiti.

I. Lumbricales.

J. First dorsal interosseous.

Vessels :

a. Ulnar artery, cut.

b. Its deep branch.

c. Deep palmar arch.

d. Radial digital artery of the
index linger.

e. Arteria princeps pollicis.
/. Interosseous arteries,

Nerves :

1. Ulnar nerve, cut.

2. Its deep part, continued at 4
to some of the thumb muscles.

3. Offsets to the inner two
lumbricales.

the abductor, and from the outer side of the ridge of the trapezium ;
and it is inserted into the outer surface and radial border of the
metacarpal bone for the whole length.

This muscle is for the most part concealed by the abductor, beneath

^ *' former:

DISSECTION OF THK HAND.

Flexor
brevis
poUicis.

though it projects on its outer side. Along its inner Ijorder is th'i
flexor brevis pollicis. j

Action. It draws the metacarpal hone inwards over the pain;
rotating it at the same time, so as to turn the ball of the thuml
towards the fingers, thus producing the movement of opposition.

The FLEXOR BREVIS POLLICIS * (c) cunses from the lower borde
of the outer part of the annular ligament, and is inserted into th(
outer margin of the base of the first phalanx of the thumb ; it-

Flexor carpi radial is.

Flexor carpi
ulnaris.

Abductor minimi
digiti.

Opponens minimi
digiti.

Palmar interossei.

Adductor trans-

versus.

Opponens minimi

digiti.

Flexor brevis
minimi digiti.

Interossei.

Flexor profundus
digit orum.

Abductor pollicis.

Opponens iioUicis.

Deep head tlexor
brevis pollicis.
Part of first dorsal

interosseus.
Opponens pollicis.

Adductor obli-
quus (encircled
by ring).

Flexor loiigus
pollicis.

Dorsal interossei.

Flexor sublimis
digitorum.

Fig. 32. — The Bones of the Hand showing the Muscular Attachments.

outer head
to external
sesamoid
bone;

relations ;

tendon contains a sesamoid bone close to its insertion. It lies along
the inner border of the opponens pollicis, and is superficial to the
tendon of the long flexor.

Action. The muscle bends the metacarpo-phalangeal joint, and
assists the opponens in drawing the thumb forwards and inwards
over the palm.

* An inner head of the flexor brevis is commonly described as a small
slip, which is concealed by the adductor obliquus pollicis, and which will be
subsequently seen to p.-^ss from the ulnar side of the first metacarpal bone to
be insei'ted^into the first phalanx with that muscle. It belongs, however, to
the same plane of muscles as the adductors, and will be described with the
adductor obliquus pollicis.

SHORT MUSCLES OF THE LITTLE FINGER. 79

The ADDUCTOR OBLiQurs POLLicis (c') arises deeply in the hand Adductor
from the sheath of the flexor carpi radialis, the anterior ligaments obiiqnus:
of the carpus, the os magnum, and the bases of the first, second, and origin ;
third metacarpal bones (fig. 32). Directed obliquely downwards and pa.sses to
outwards, the greater part of the muscle is insert^c? into the ulnar side ge^Sid
of the base of the first phalanx in union M-ith the adductor trans- bone,
versus, a sesamoid bone being formed in the tendon over the head
of the metacarpal bone. A small slip of the muscle usually passes and sends a
outwards beneath the tendon of the long flexor to join the insertion J^^al ;
of the outer head of the flexor brevis.

The tendon of the flexor longus pollicis lies between this muscle relations ;
and the flexor breWs ; and its origin is covered by the outer tendons
of the flexor profundus and the lumbricales. It lies over the
first dorsal interosseous muscle, and the ending of the radial
artery.

Action. It flexes the metacarpo-phalangeal joint, and draws the use.
thumb over the palm.

The ADDUCTOR TRANSVERSUS POLLICIS (d) is triangular in shape, Adductor
with the ai)ex at the thumb, and the base in the centre of the palm, tra^sversus
Its origin is from the ridge on the lower two-thirds of the palmar
aspect of the third metacarpal bone (fig. 32) ; and its insertion is into joins
the inner side of the first phalanx of the thumb, in common with the obHqiras ;
last muscle. From the conjoined insertion of the two adductors a
slip is sent to the tendon of the extensor longus pollicis.

The anterior surface is in contact with the tendons of the flexor relations

fundus and the lumbrical muscles ; and the posterior surface lies

r the interosseous muscles of the first and second spaces, with the
rvening metacarpal bone. The deep palmar arch separates this

<d.e from the adductor obliquus.

Action. It draws the thumb towards the centre of the palm. audu.se.

-^HORT Muscles of the Little Finger (fig. 31). In the Two or three
ii} pothenar eminence there are the aMuctor and opponens muscles ™ttle fineer
of the little finger, and sometimes a short flexor.

The ABDUCTOR minimi digiti (e) is superficial to the opponens Abductor
muscle. It arises from the pisiform lx)ne, and is inserted into the is beneath
ulnar side of the base of the first phalanx of the little finger ; an ^^^ '
oftset from it reaches the extensor tendon on the back of the phalanx.
The palmaris brevis partly conceals the muscle.

Action. Firstly it draws the little finger away from the others ; use.
but continuing to act, it bends the metacarpo-phalangeal joint.

The flexor brevis minimi digiti (f) is placed at the radial Flexor
V'- jrder of the preceding muscle. It takes origin from the tip oftenVb-
of the process of the unciform bone, and slightly from the sent ;
annular ligament ; and it is inserted with the abductor into the
first phalanx.

It lies on the opponens ; and near its origin it is separated relations
from the abductor by the deep branches of the ulnar artery
and nerve.

Action. It flexes and abducts the first phalanx of the little and use.
finger.

DISSECTION OF THE HAND.

Opponens
attach-
ments ,

relations,
and use.

Dissection
of deep arch
and

interosseous
muscles and
fascia.

Radial
artery in
hand

forms deep
arch,

which lies
near carpal
bones,

and beneath
muscles,

with venae
comites.

Branches :
recurrent ;

perforating ;

palmar in-
terosseous.

Digital
branches :

The OPPONENS MINIMI DiGiTi (g) resembles the opponens pollicis
in being attached to the metacarpal bone. Its origin is from the
hook of the unciform bone, and the lower part of the annular
ligament ; its insertion is into the ulnar side of the metacarpal
bone of the little finger.

The opponens is partly overlaid by the preceding muscles ; and
beneath it the deep branches of the ulnar artery and nerve pass.

Action. It raises the inner metacarpal bone, and moves it
towards the others, so as to deepen the hollow of the palm.

Dissection. The radial artery comes into the hand between the
first two metacarpal bones ; and to lay bare the vessel it will be
requisite to detach the origin of the adductor obliquus pollicis. The
deep palmar arch and the branch of the ulnar nerve accompanying
it, together with their offsets, are to be dissected out.

A fascia which covers the interosseous muscles is to be removed,
after the dissector has observed its connection with the transverse
ligament uniting the heads of the metacarpal bones.

Kadial artery in the hand (fig. 31). The radial artery enters
the palm at the first interosseous space, between the heads of the
first dorsal interosseous muscle ; and after furnishing one branch to
the thumb, and another to the index finger, it turns across the hand
towards the ulnar side, forming the deep arch.

The dee}') palmar arch (c) extends from the upper end of the first
interosseous space to the base of the metacarpal bone of the little
finger, where it joins the deep branch of the ulnar artery (6). Its
convexity, which is but slight, is directed downwards ; and its
situation is nearer the carpal bones than that of the superficial arch.
The arch has a deep position in the hand, and lies on the metacarpal
bones and the interosseous muscles. It is covered by the long flexor
tendons, and in part by the adductor obliquus pollicis and oi^ponens
minimi digiti muscles. Two veins accomjmny it. The branches of
the arch are the following : —

a. Recurrent hrcmches pass from the concavity of the arch to the
front of the carpus ; these supply the bones and joints, and anastomose
with the anterior carpal arteries.

h. Three perforating arteries pierce the inner three dorsal interos-
seous muscles, and communicate with the interosseous arteries on the
back of the hand.

c. Usually there are three "palmar interosseous arteries (/ ), which lie
over the inner three intermetacarpal spaces, and terminate by joining
the digital branches of the superficial palmar arch at the clefts of
the fingers. An off'set of the inner one, or a separate branch of the
arch, joins the digital artery to the inner side of the little finger
(p. 71). These branches supply the interosseous muscles, and the
two or three inner lumbricales ; they vary much in their size and
arrangement. Their size, as a rule, varies inversely with that of
the corresponding digital branches of the superficial arch, which they
join at the cleft between the fingers.

d. Digital branches of the radial. The arteria p'inceps pollicis (e)
runs along the first metacarpal bone to the interval between the

THE INTEROSSEOUS MUSCLES. fil

adductor obliquus and the flexor brevis poUicis, where it divides artery of
into the two collateral branches of the thumb ; these are distributed ^^^ thumb ;
like the arteries of the superficial arch (p. 72).

e. The radial digital branch of the index finger (d) (arteria artery of
radialis indicis) is directed over the first dorsal interosseous ^^ ^^^^'
muscle (j), and beneath the adductors of the thumb, to the radial
side of the forefinger. At the lower border of the adductor
transversus (d), this branch is iisually connected by an offset
with the superficial palmar arch ; and at the end of the digit it
unites with the branch furnished to the opposite side by the ulnar *

artery.

The DEEP PART OF THE ULNAR NERVE (2) accompanies the deep Deep branch

arterial arch as far as the muscles of the thumb, where it terminates ng^y" t^
in oftsets to the two adductors.

Branches. Near its origin the nerve furnishes branches to the muscular
muscles of the little finger. In the palm it gives offsets to all the **^'*^''-
palmar and dorsal interosseous muscles, and to the inner two
lumbrical muscles (^), besides the terminal branches before men-
tioned.

The TRANSVERSE METACARPAL LIGAMENT is formed by cross fibres Transverse

uniting the palmar ligaments of the metacarpo-phalangeal articula- mSSrpus.
tions of the fingers, and serves to bind together the heads of the
inner four metacarpal bones. To its upper border the fascia cover-
ing the interosseous muscles is attached. The ligament should now
taken away to see the interosseous muscles.

The INTEROSSEOUS MUSCLES, SO named from their position Seven inter-
between the metacarpal bones, are seven in number. Two muscles mSSS
«' cupy each space, except the first, where there is only one. They
arise from the metacarpal bones, and are inserted into the fii-st
phalanges of the fingers and the expanded extensor tendons. They divided into
are diWded into palmar and dorsal ; but all are seen in the palm of dorealf
tlie hand, though the former project more than the others.

The palmar muscles (fig. 33), three in numljer, are smaller than Painaargo
the dorsal, and have each a single origin from the side of the ring, and
metacarpal bone of the finger to which it belongs. The first is kittle lingers,
placed on the ulnar side of the index finger, the second and third
on the radial side of the ring and little fingers respectively.

The dorsal muscles (fig. 34), one in each space, arise by two Dorsal : two
heads from the lateral surfaces of the metacarpal bones between fi^^r*) one
\vhich they lie. The first (abductor indicis) is inserted on the each to
radial side of the index finger, the second on the radial and the ring lingers,
third on the ulnar side of the middle finger, and the fourth on the
ulnar side of the ring finger.

Both sets of muscles have a similar termination (fig. 29, Common
p. 75) : the fibres end in a tendon, which is inserted into the side '^^ ^£ °
of the first or metacarpal phalanx, and sends an expansion to join
the extensor tendon on the dorsum of the bone.

Action. They bend the metacarpo-phalangeal joints by their Action as
attachment to the first phalanx, and extend the two interphalangeal extensors,
joints through their union with the extensor tendon.

D.A. G

DISSECTION OF THE HAND,

as abductors
and adduc-
tors.

Dissection.

Annular
ligament
of front
of wrist.

The interosseous muscles also separate and approximate the
straightened fingers, the palmar set adducting the index, ring and
little fingers towards the middle digit ; while the dorsal abduct
their fingers from the median line of the hand, the two fixed t<>
the middle finger moving it to either side of that line.

Dissection. The attachments of the annular ligament to thf
carpal bones on each side are next to be dissected out by taking
away the small muscles of the thumb and little finger. Before
reading its description, the ends of the cut ligament may be placed
in apposition, and fixed with a stitch.

The ANTERIOR ANNULAR LIGAMENT is a broad band, which
arches over and binds down the flexor tendons of the fingers. It is

Fig. 33.— The Three Palmar
Interosseous Muscles.

a. Muscle of the little finger.
h. Muscle of the ring finger.
c. Muscle of the index finger.

Fig. 34. — The Four Dorsal
Interosseous Muscles.

d. Muscle of the index finger.

e and/. Muscles of the middle finger.

g. Muscle of the ring finger.

attached internally to the pisiform and the hook of the unciform,

and externally to the tuberosity of the scaphoid and the ridge of

the trapezium, as well as by a deeper process to the trapezoid bone

on the inner side of the groove for the flexor carpi radialis. By its

upper border it is continuous Avith the aponeurosis of the forearm ;

and anteriorly it is joined by the palmar fascia. Over it lie the

palmaris longus tendon and the ulnar vessels and nerve.

Dissection. Dissection. Follow the tendon of the flexor carpi radialis to its

insertion into the metacarpal bones, by dividing the overlying part

of the anterior ligament.

Insertion of The tendon of the flexor carpi radialis^ in passing through the

raSi?^^ ^^^^ to its insertion lies in a groove in the trapezium between the

SUPERFICIAL MUSCLES. 83

attachments of the annular ligament, but not within the arch of
that band ; here it is bound down by a fibrous sheath and is
lined by a synovial membrane. The tendon is inserted into the
base of the metacarpal bone of the index finger, and sends a slip
to that of the middle digit.

Section YT.

THE BACK OF THE FOREARM.

Position. During the dissection of the Irnck of the forearm the Position,
limb lies on the front, and a small block is to be placed beneath
the wrist for the purpose of stretching the tendons.

Dissection (fig. 35). The fascia and the cutaneous nerves and Takeaway
vessels are to be reflected from the njuscles of the forearm, and from ficial nerves
the tendons on the back of the hand ; but in removing the fascia J^^j*^^®
in the forearm, the student must be careful not to cut away the
posterior interosseous vessels, which are in contact with it on the
ulnar side in the lower third. A thickened band of the fascia
opposite the carpus (the posterior annular ligament) is to be left.

Let the integument be removed from the fingers, in order that Strip
the tendons may be traced to the end of the digits.

The several muscles should l)e separated from one another up to Separate
tlieir origin, especially the two radial extensors of the wrist.

The POSTERIOR ANNULAR LIGAMENT (k) is a part of the deep Annular
} iscia, thickened by the addition of transverse fibres, and is situate behind the
' opposite the lower ends of the bones of the forearm. This Imnd is ^""^t.
attached on the out^r side to the radius, and on the inner side to the
\ ramidal and pisiform bones. Processes from it are fixed to the

lies beneath, and confine the extensor tendons. The ligament
>vill subsequently be examined more in detail.

Superficial Layer of Muscles (fig. 35). The muscles of the Superficial
back of the forearm are arranged in a superficial and a deep layer, ^ven
The superficial layer contains seven muscles, which arise, in part by muscles,
a common tendon, from the outer side of the humerus, and are
placed in the following order from without inwards : — the long
supinator (a), the long and short radial extensors of the wrist (b
and c), the common extensor of the fingers (d), the extensor of the
little finger (e), and the ulnar extensor of the wrist (f). There is
one other small muscle near the elbow — the anconeus (g).

The supinator radii longus (a) reaches upwards into the arm, supinator
and limits on the outer side the hollow in front of the elbow. It ^°°^^-
arises from the upper two-thirds of the external supracondylar ridge °"^*" '
c.f the humerus, and from the front of the external intermuscular
-eptum of the arm. The fleshy fibres end about the middle of the
forearm in a tendon, which is inserted into the lower end of the insertion ;
radius, close above the styloid process.

In the arm the margins of the supinator are directed towards the relations ;
surface and the bone, but in the forearm the muscle is flattened over

and use,
radius free

and fixed.

Extensor
carpi radialis
longior :
origin ;

DISSECTION OF THE BACK OF THE FOKEARM.

the others, with its edges forwards
and backwards. Its anterior border
touches the biceps and the pro-
nator teres ; and the posterior is
in contact with both radial ex-
tensors of the wrist. Near its
insertion the supinator is covered
by two extensors of the thumb.
Beneath the muscle are the bra-
chial] s anticus and the musculo-
spiral nerve, the extensors of the
M'rist, the radial vessels and nerve,
and the radius.

Action. The chief use of the
supinator longus is to bend the
elbow-joint; but if the radius is
either forcibly pronated or supi-
nated, the muscle can put the
hand into a state intermediate
between pronation and sujnnation.

If the radius is fixed, as in
climbing, the muscle will bring up
the humerus, bending the elbow.

The EXTENSOR CARPI RADIALIS

LONGIOR (b) arises from the lower
third of the external supracondylar
ridge of the humerus, from the
front of the external inter-
muscular septum, and from the
septum between it and the next
muscle. It lies on the short radial
extensor, being partly covered by
the supinator longus ; and its
tendon passes beneath the extensors
of the thumb, and the annular

FiQ, 35. — Superficial Dissection of the Back of the
Forearm. (Illustrations of Dissections).

licis.

Muscles :
Supinator longus.
Extensor carpi radialis longior.
Extensor carpi radiahs brevior.
Extensor communis digitorum.
Extensor minimi digiti.
Extensor carpi ulnaris.
Anconeus.
Extensor ossis metacarpi pol-

Extensor brevis pollicis.
Extensor longus pollicis.
Posterior annular ligament.

L. Bands uniting the tendons of
the common extensor on the back of
the hand.

N. Insertion of the common extensor
into the second and third phalanges.

Arteries :
a. Posterior interosseous.

1. Radial.

2. Posterior carpal arch.

h. Dorsal interosseous branch.
4. Dorsal branches to thumb and
forefinger.

SUPERFICIAL MUSCLES. 85

ligament, to be inserted into the base of the metacarpal bone of insertion ;
the index finger. Along its outer border lies the radial nerve.

Action. The long extensor straightens the wrist and abducts the and use.
hand ; it can also bend the elbow-joint.

If the hand is fixed in climbing, it will act on the humerus like
the long supinator.

The EXTENSOR CARPI RADIALIS BREVIOR (c) is attached, to the Extensor

outer condyle of the humerus by a tendon common to it and the ^Jfaijg
three following muscles, viz., common extensor of the fingers, brevior:
extensor of the little finger, and ulnar extensor of the wrist ; it
takes origin also deeply from the external lateral ligament of the origin ;
elbow-joint. The tendon of the muscle is closely applied to the
preceding, and after passing with it through the same compartment
of the annular ligament, is inserted into the base of the metacarpal inseri;ion ;
bone of the middle finger.

Concealed on the outer side by the two preceding muscles, this parts
extensor rests on the radius and two of the muscles attached to it, *™^^" ^^'
viz., supinator brevis, and pronator teres. Along its inner side is
the common extensor of the fingers ; and the extensors of the thumb
i-^sue between the two. Each radial extensor has usually a bursa
Ijeneath the tendon, close to its insertion.

Action. This muscle acts in the same way as its fellow, and "se.

The EXTENSOR COMMUNIS DIGITORUM (d) is Single at its origin, Common

but is divided below into four tendons. It arises from the common of ^"gere •

tendon, from the fascia, and from aponeurotic septa between it and

the adjacent muscles. At the lower part of the forearm the muscle origin ;

ends in four tendons, which pass through a compartment of the

annular ligament with the extensor indicis, and are directed along division into

the back of the hand to their insertion into the second and third {^nJons •

phalanges of the fingers.

On the fingers the tendons have the following arrangement. On insertiion
ilie dorsum of the first phalanx each forms an expansion with the ^'Jj^jjJ^J^gg .
tendons of the lumbricalis and interosseous muscles (fig. 29, j). 75).
At the lower part of that phalanx the expansion divides into three
parts (fig. 35, n) ; — the central one is fixed into the base of the
second phalanx, while the lateral pieces unite, and are inserted into
the base of the last phalanx. Opposite the first two articulations of
each finger the tendon sends down lateral bands to join the capsule
of the joint. On the fore and little fingers the expansion is joined
by the special extensor tendons of those digits.

This muscle is placed between the extensors of the wrist and relations of

1116 niU-Sclc *

little finger, and conceals the deep layer. On the back of the hand
the tendons are joined by cross bands (l), thinnest between the
index finger tendon and its neighbour, and strongest between the
ring finger tendon and its collateral tendons, so that they prevent
the ring finger being raised if the others are closed.

Action. Tlie muscle straightens the fingers and separates them use,
from each other. It acts especially on the first phalanges, the two ^^ ^
interphalangeal joints being extended mainly by the interosseous
and lumbricales muscles.

DISSECTION OF THE BACK OF THE FOREARM.

on elbow
and wrist.

Extensor of
little finger :

ongni

The digits being straightened, it will assist the other muscles in i
extending the wrist and the elbow.

The EXTENSOR MINIMI DiGiTi (e) is the most slender muscle on ;
the back of the forearm, and appears to be but a part of the common
extensor. Its origin is in common with that of the extensor com-
munis, but it passes through a distinct sheath of the annular liga-
termination; ment. Beyond the ligament the tendon splits into two, and the
outer part is joined by the fourth tendon of the common extensor :
finally, both parts enter the common expansion on the first phalanx
of the little finger.

Triceps.

Supinator brevis.

Pronator teres.

Extensor brevis pollici^

Extensor carpi ulnaris.
Flexor carpi ulnaris.

Flexor profundus digitorum.

Extensor longus pollicis.
Flexor carpi ulnaris.

Extensor indicis.

Fig. S6.— The Radius and Ulna from behind.

and use.

Extensor
carpi ulna-
ris:

origin

Action. It extends the little finger and moves back the wrist
and elbow. As the inner piece of the split tendon is not united
with the common extensor, it can straighten the digit during flexion
of the other fingers.

The EXTENSOR CARPI ULNARIS MUSCLE (f) arises from the com-
mon tendon, the aponeurosis of the forearm, and an intermuscular
septum on its outer side ; it is also fixed by fascia to the middle
third of the posterior border of the ulna below the anconeus
muscle (fig. 36). Its tendon becomes free from fleshy fibres near
the annular ligament, and passes through a separate sheath in that
structure to be inserted into the tuberosity at the base of the
metacarpal bone of the little finger.

DEEP MUSCLES. 87

Beneath this extensor are some of the muscles of the deep layer, relations ;
with part of the ulna. On the outer side is the extensor of the
little finger, with the posterior interosseous vessels.

Action. The ulnar extensor straightens the wrist, and inclines the and use.
hand towards the ulnar side : it can then extend the elbow-joint.

The ANCONEUS (g) is a small triangular muscle near the elbow. Anconeus
It arises from the outer condyle of the humerus by a tendon distinct origin ;
from, and on the ulnar side of the common tendon of the foregoing
muscles. From this origin the fibres diverge to their insertion into insertion ;
the outer side of the olecranon, and into the impression on the upper
third of the posterior surface of the ulna (fig. 36).

The upper fibres are nearly transverse, and are contiguous to the touches the
lowest of the triceps muscle. Beneath the anconeus lie the supinator *^*^^P^;
brevis muscle, and the interosseous recurrent vessels.

Action. It assists the triceps in extending the elbow. use.

Dissection (fig. 37). For the display of the deep muscles of Dissection
the back of the forearm, and of the posterior interosseous vessels and of muscles^*^
nerve, three of the superficial nuiscles, viz., extensor communis
•ligitorum, extensor minimi digiti, and extensor carpi ulnaris, are to
be di^ided above and turned aside ; and the small branches of the
nerve and artery entering these muscles may be cut.

The loose tissue and fat are then to be removed from the muscles,
and from the ramifications of the artery and nerve ; and a slender and interos.
part of the nerve, which sinks beneath the extensor of the second and"nervr^''
phalanx of the thumb about the middle of the forearm, should be
traced beyond the wrist.

The deep muscles should be carefully separated, since the outer
two of the thumb are not always very distinct from each other.

Deep Layer of Muscles (fig. 37). In this layer there are five Five
muscles, viz., one supinator of the forearm, and four special extensor ^e^deeV"
muscles of the thumb and index finger. The highest muscle, partly ^^Y^^-
surrounding the upper third of the radius, is the supinator brevis (d).
Below this are the three muscles of the thumb in the following
order : — the extensor of the metacarpal bone (e), the extensor of
the first (f), and that of the second phalanx (g). On the ulna the
indicator muscle (h) is jilaced.

The extensor OSSIS METACARPI POLLICIS (e, fig. 37, also Extensor

fig. 36) is the largest and highest of the extensor muscles of n^etacarpi

the thumb, ancl is sometimes united with the supinator brevis. It pollicis:

arises from the posterior surface of the radius in its middle third, origin ;

below the supinator brevis, from a special narrow impression on

the ulna, occupying the upper third of the outer division of the

posterior surface, and from the intervening interosseous membrane.

The tendon is directed outwards over the radial extensors of the

wrist, and through the annular ligament, to be inserted into the insertion;

base of the metacarpal bone of the thumb, and by a slip into

the trapezium : another slip is frequently continued to the abductor

pollicis.

The muscle is concealed at first by the common extensor of the muscle
the fingers ; but it becomes superficial in the lower third of the ^l^ ^^^

DISSECTION OF BACK OF FOKEARM. '

forearm between the last muscle
and the radial extensors of the
wrist (fig. 35). Opposite the
carpus the radial artery winds
backwards beneath its tendon.
Between the contiguous borders
of this muscle and the supinator
brevis the posterior interosseous
artery (a) appears.

Action. By this muscle the
thumb is carried outwards and
backwards from the palm of the
hand, and the hand is moved to
the radial side.

The EXTENSOR BREVIS POLLICIS

(ext. primi internodii poll. ; f ; ,
fig. 35, 1.) is the smallest muscle of
the deep layer, and its tendon ac-
companies that of the preceding
extensor. Its origin, about one inch
in width, is from the radius and the
interosseous membrane, close below
the attachment of the last muscle
(fig. 36). The tendon passes through
the same space in the annular liga-
ment as the extensor of the meta-
carpal bone, and is inserted into
the base of the first phalanx of
the thumb. With respect to sur-
rounding parts, this muscle has
similar relations to the preceding.
Action. It extends first the
proximal phalanx and then the
metacarpal bone, like its com-
panion.

The EXTENSOR LONGUS POLLICIS

(ext. secundi internodii poll. ; g)

Fig. 37. — Deep Dissection of the Back of the Forearm (Illustrations
OF Dissections).

Muscles :

A. Supinator longus.

B. and c. Radial extensors of the
carpus, cut.

D. Supinator brevis.

e. Extensor ossis metacarpi pollicis.

F. Extensor brevis pollicis.

G. Extensor longus pollicis.
H. Extensor indicis.

I. Posterior annular ligament.

Arteries :
a. Posterior interosseous.
h. Interosseous recurrent.

c. Ending of the anterior inter-
osseous.

d. Radial.

e. Dorsal branches to the thumb
and forefinger.

/. Dorsal carpal arch.

g. Two dorsal interosseous of the

hand. ,,

Nerves :

2. Radial.

3. Posterior interosseous at its
origin, and

4. Near its"ending on the back of
the carpus.

THE SUPINATOR BREVIS. 89

arises from the middle third or more of the ulna below the origin ;

anconeus, along the ulnar side of the extensor of the metacarpal

bone (fig. 36) ; and from the interosseous membrane below, for

about an inch. Its tendon, passing through a distinct sheath in the

annular ligament, deeply grooving the radius, is directed along

the dorsum of the thumb to be inserted into the base of the last insertion ;

phalanx.

The belly of the muscle is covered by the extensor carpi ulnaris relations ;
and the extensors of the fingers, but the tendon becomes superficia_
close to the wrist. Below the annular ligament its tendon crosses
the extensors of the wrist and the radial artery.

Action. It first extends both phalanges of the thumb, and and use.
then helps in moving backwards the metacarpal bone and the
hand.

The EXTENSOR iNDicis (indicator ; h) arises on the inner side of Indicator
the last muscle from the ulna for two or three inches (fig. 36), usually ™"^ ^"
below the middle and from the lower part of the interosseous
membrane. Near the wrist the tendon becomes free from muscular origin ;
fibres, and passing beneath the annular ligament with the common
t xtensor of the fingers, is applied to, and blends with the external insertion ;
tendon of that muscle in the expansion on the first phalanx of
the forefinger.

Until this muscle has passed the ligament it is covered by the
superficial layer, but it is afterwards subaponeurotic.

Action. The muscle can point the forefinger, even when the three and use.
inner fingers are bent ; and it will help the common extensor of the
digits in drawing back the hand.

Dissection. To lay bare the supinator brevis, it will lie necessary Dissection
to detach the anconeus from the external condyle of the humerus, brevis!"*
and to cut through the supinator longus and the radial extensors of
the wrist. After those muscles have been divided, the fleshy fibres
of the supinator are to be followed forwards to their insertion into
the radius ; and that part of the origin of the flexor profundus
digitorum which lies on the outer side of the insertion of the
brachialis anticus, is to be removed.

The SUPINATOR BREVIS (d) suFTounds the upper part of the Origin of
radius, except at the tuberosity and the front of the bone below it. natorP^*'
It arises from the external margin of the ulna for a distance of two
inches, as well as from a depression below the small sigmoid cavity ;
also from the orbicular ligament of the radius and the external
lateral ligament of the elbow-joint. The fibres pass outwards and
forwards, and are inserted into the upper third or more of the radius, and inser-
except at the fore and inner parts, reaching downwards to the *'°° '
insertion of the pronator teres, and forwards to the oblique line of
the bone (fig. 25, p. 61 ; and fig. 36).

The supinator brevis is concealed altogether at the posterior and
external aspects of the limb by the muscles of the superficial layer ;
and anteriorly the radial vessels and nerve lie over it. The lower overiying
border is contiguous to the extensor ossis metacarpi pollicis, oidy and con-
the posterior interosseous vessels (a) intervening. Through the S^".^

DISSECTION OF THE BACK OF THE FOREARM.

Posterior

interosseous

artery

between the
layers of
muscles,

and super-
ficial :

its recur-
rent branch.

Posterior
interosseous
nerve :

position to
muscles ;

termination
on back of
the carpus ;

its muscular

Radial

artery at
wrist :

relations to

parts

around.

and nerves.

Branches
are small :

to back of
carpus ;

substance of the umscle the posterior interosseous nerve (^) winds to
the back of the limb.

Action. When the radius has been moved over the ulna in
pronation, the short supinator comes into play to bring that bone
again to the outer side of the ulna.

The POSTERIOR INTEROSSEOUS ARTERY (fig. 37, ct) is an offset
from the common interosseous trunk (p. 66), and reaches the back
of the forearm above the membrane between the bones. Appearing
between the contiguous borders of the supinator brevis and extensor
ossis metacarpi poUicis, the artery descends at first l)etween the
superficial and deep layers of muscles ; and afterwards with a
superficial position in the lower third of the forearm, along the
tendon of the extensor carpi ulnaris as far as the wrist, where it
ends by anastomosing with the carpal and anterior interosseous
arteries. It furnishes muscular offsets to the surrounding muscles,
and the following recurrent branch : —

The recurrent branch (b) springs from the artery near the beginning,
and ascends on or through the fil)res of the supinator, but beneath
the anconeus, to supply both those muscles and the elbow-joint ;
it anastomoses with the superior profunda artery and the recurrent
radial (fig. 19, p. 46).

The POSTERIOR INTEROSSEOUS NERVE (^) is derived from the
niusculo-spiral trunk (p. 53), and winds backwards through the
fibres of the supinator brevis. Issuing from the supinator, the nerve
is placed between the superficial and deep layers of muscles as far
as the middle of the forearm. Much reduced in size at that spot, it
sinks beneath the extensor of the second phalanx of the thumb, and
runs on the interosseous membrane to the back of the carpus.
Finally, the nerve enlarges beneath the tendons of the extensor
communis digitorum, and terminates in filaments to the articulations
of the carpus.

Brandies. It furnishes offsets to all the muscles (^f the deep layer,
and to those of the superficial layer with the exception of the three
following, viz., anconeus, supinator longus, and extensor carpi radialis
longior.

Radial artery at the wrist (fig. 37). The radial artery (d),
with its venae comites, winds below the radius to the back of the
carpus, and enters the palm of the hand at the first interosseous
space, between the heads of the first dorsal interosseous muscle. At
first the vessel lies deeply on the external lateral ligament of the
wrist-joint, and beneath the tendons of the extensors of the meta-
carpal bone and the first phalanx of the thuml) ; but afterwards it is
more superficial, and is crossed by the tendon of the extensor of the
second phalanx of the thumb.

Oftsets of the nmsculo-cutaneous nerve entwine around the artery
(p. 56), and branches of the radial nerve are superficial to it. Its
branches are numerous but inconsiderable in size : —

1. The dorsal carpal branch (/) passes transversely beneath the
extensor tendons, and forms an arch {the dorsal, or posterior, carpal
arch) J with a corresponding offset of the ulnar artery ; this arch is

BRANCHES OF THE RADIAL ARTERY. 91

joined liy the interosseous arteries, especially by the posterior
terminal branch of the anterior interosseous.

From the dorsal carpal arch l)ranches {g) descend to the third dorsal inter-
and fourth interosseous spaces, and constitute two of the three osseous ;
dorsal interosseous arteries : at the cleft of the fingers each divides
into two, which are continued along the dorsum of the digits.
Below, they communicate with the digital arteries ; and above,
they are joined by the perforating branches of the deep palmar
arch.

2. The metacarpal or first dorsal interosseous branch of the radial metacarpal ;
(fig. 35, b) gains the space between the second and third metacarpal

bones, and receives, like the corresponding arteries of the other
spaces, a perforating branch from the deep palmar arch. Finally,
it is continued to the cleft of the fingers, where it joins the digital
artery of the superficial palmar arch, and gives small dorsal branches
to the index and middle fingers.

3. Two small dorsal arteries of the thumb arise opposite the dorsal
metacarpal bone, along which they extend, one on each border, to thumb^ °
be distributed on its posterior aspect.

4. The dorsal branch of the index finger is distributed on the radial and fore-
edge of that digit. °^'^'

The diff'erent divisions of the annular ligament may now be seen Sheaths of
more completely by cutting the sheaths of the ligament over the fi^JjJent
several tendons passing beneath. There are six separate compart-
ments, and each is lubricated by a synovial membrane. The most out inwai-ds.
external one lodges the first two extensors of the thumb. The next
is a large hollow for the two radial extensors of the wrist ; and a
small space for the long extensor of the thumb follows on the ulnar
side. Farther to the inner side is the common sheath for the
extensor of the fingers, and that of the forefinger ; and then comes
a slender compartment for the extensor of the little finger. Internal Bones
to all is the space for the extensor carpi ulnaris. The last muscle the tendons,
grooves the ulna ; but the others lie in hollows in the radius in the
order mentioned above, with the exception of the extensor minimi
digiti which is situate between the bones.

Dissection. If the supinator brevis be divided by a vertical To see
incision, and reflected from the radius, its attachment to that bone sui^inatorl^
will be better understood.

The posterior interosseous nerve, and the oflFsets from its gangli- interosseous
form enlargement, may be traced more completely after the tendons
of the extensor of the fingers and indicator muscle have been cut
at the wrist.

The posterior surface of the dorsal interosseous muscles of the and inter-
hand may next be cleaned, so that their double origin, and their muscles,
insertion into the side, and on the dorsum of the phalanges, may be
fully observed. Between the heads of origin of these muscles the
posterior perforating arteries appear.

Lastly, the outer head of the first dorsal interosseous muscle is to Passage
l)e divided, and carefully separated from the first metacarpal bone, artery into
so as to display the passage of the radial artery into the palm. v^im.

DISSECTION OF THE UPPER LIMB.

Section VII.

LIGAMENTS OF THE SHOULDER, ELBOW, WRIST, AND
HAND.

Directions.

Dissection
of external
ligaments of
shoulder.

Shoulder-
joint,
outline of.

Looseness.

Capsular
ligament ;

attach-

aperture ;

muscles
around :

accessory
band.

Dissection
of internal
stnictures.

Directions. The ligaments of the remaining articulations of the
limb, which are still moist, may be examined at once ; but if any
of them have become dry, they may be softened by immersion in
water, or with a wet cloth, while the student learns the others.

Dissection. For the preparation of the external ligaments of
the shoulder-joint the tendons of the surrounding muscles, viz.,
subscapularis, supraspinatus, infraspinatus, and teres minor, must
be detached from the capsule ; and as these are closely united with
the capsule some care will be needed not to injure it.

The Shoulder-Joint. This l)all and socket joint (fig. 38) is
formed between the head of the humerus and the glenoid fossa of
the scapula. Enclosing the articular ends of the bones is a fibrous
capsule lined by a synovial membrane. A ligamentous band
(glenoid ligament) deepens the shallow scapular cavity for the
reception of the large head of the humerus.

The bones are but slightly bound together by ligaments, for, on
the removal of the muscles, the head of the humerus may be draAvn
from the scapula for the distance of an inch.

The capsular ligament (fig. 14, ^, p. 36) encloses the articular
portions of the bones. It is much thickened al)ove, and is thin
below. The surrounding tendons are closely adherent to it above,
in front and behind.

By the one end it is fixed around the articular surface of the
scapula, where it is connected with the long head of the triceps.
By the other the ligament is fixed (fig. 38) to the neck of the
humerus close to the articular surface above, but at a little dis-
tance down the bone below ; and its attachment is interrupted
between the tuberosities (6) by the tendon of the biceps muscle,
across which fibres are continued, covering in the groove (fig. 14).
On the inner side there is an aperture in the capsule, below the
coracoid process, through which the synovial membrane of the joint
is continuous with the bursa beneath the tendon of the subscapularis.

The following muscles surround the articulation ; — above and
behind are the supraspinatus, infraspinatus, and teres minor ; below
are the long head of the triceps and the lower part of the subscapu-
laris ; and in front it is covered by the last-named muscle.

On the upper part of the capsule is a thick band of fibres — the
coraco-humeral or accessory ligament (fig. 14, ^), which springs from
the outer side of the coracoid process of the scapula, and widening
over the top of the joint, is attached to the great tulierosity and
margins of the bicipital groove.

Dissection. To see the interior of the articulation cut away the
posterior part of the capsule, leaving its attachments to the humerus

LIGAMENTS OF THE SHOULDEK-JOINT.

and scapula, dislocate the head of the humerus through the hole
thus made and saw it off close to the capsular attachment. When
this has been done, the glenoid ligament, the tendon of the biceps and
the gleno-humeral hands on the articular aspect of the front part of
the capsule will be manifest.

The tendon of the biceps muscle arches over the head of the humerus, Tendon of
and serves the purpose of a ligament in supporting the bone. It
is attached to the upper part of the head of the scapula (fig. 38, (^),
and is united on each side with the glenoid ligament. At first
flat, it afterwards becomes round, and enters the groove between
the tuberosities of the humerus, where it is surrounded by the
synovial membrane. The transverse fibres bridging across the Transverse
bicipital groove are^spoken of as the transverse humeral ligament. ligament

Fig. 38. — ^View of the Interior op the Shoulder-Joint.

a. Attachment of the capsule to
the neck of the humerus.

b. Interval of the bicipital
groove.

c. Glenoid ligament around the
glenoid fossa.

d. Tendon of the long head of the
biceps fixed at the top of the fossa.

The glenoid ligament (fig. 38, c) is a narrow fibrous band
surrounds the fossa of the same name, increasing it for the recep-
tion of the head of the humerus. It is connected in part with the
sides of the tendon of the biceps ; but most of its fibres are fixed
separately to the margin of the glenoid fossa.

The gleno-humeral ligaments are three bands, or folds, seen on the
articular aspect of the fore part of the capsule. The superior is
exposed by cutting away the biceps tendon in the joint, and appears
as a small fold along the inner border of the tendon. The middle
one springs from the margin of the glenoid cavity below the fore-
going and passes obliquely downwards below the tendon of the
subscapularis to the lesser tuberosity of the humerus, and the
inferior is a strong band parallel with and below the middle, passing
to the humerus between the attachments of the subscapularis and
teres minor muscles.

which Glenoid
ligament.

DISSECTION OF THE UPPER LIMB.

Synovial
membrane

Surface of
humerus ;

of scapula.

Kinds of
movement

The synovial membrane lines the articular surface of the capsule,
and is continued through the aperture on the inner side to join the
bursa beneath the sul)scapular muscle. The membrane is reflected
around the tendon of the biceps, and lines the upper part of the
bicipital groove of the humerus.

Articular surfaces (fig. 38). The convex articular head of the
humerus is about three times as large as the hollow of tlie scapula,
and forms rather less than the half of a sphere. The head of the
bone is supported on a short neck, which is joined to the shaft at
an oljtuse angle.

The glenoid fossa of the scapula is oval in form with the larger
end down, and is very shallow. Its margin is slightly more
prominent below than above.

Movements. The looseness of the capsule, the shallowness of the
glenoid cavity and its smallness as compared with the extent of the
articulating head of the humerus allow of the movements of this
joint being both free and extensive. There is the common angular
motion in four directions, with the circular or circumductory ; and
in addition a movement of rotation.
Flexion and In the swinging to and fro movement, the carrying forwards and
inwards of the humerus , constitutes flexion ; and the moving it
extension Imck wards and outwards, extension. Flexion is freer than extension,
as the scapula follows the humerus, undergoing a rotation upwards,
so that the whole range of movement of the arm in this direction
is much greater than that taking place in the reverse articulation.
In extension the scapula is similarly rotated downwards, the lower
angle approaching the vertebral column.

Flexion of the humerus upon the scapula is checked by the
twisting of the capsule, and by the meeting of the small tuberosity
of the former bone with the coraco-acromial arch. Extension is
limited mainly by the coraco-humeral ligament.

Abduction and adduction. In abduction, the arm is moved
outwards away from the body ; and in adduction, it is brought
downwards to the side. These movements, like the foregoing,
are accompanied, and their range is increased by rofcition of the
scapula.

When the limb is abducted, the head of the humerus glides
downwards in the glenoid cavity, and projects beyond it against
the lower part of the capsule, which is stretched ; while the great
tuberosity sinks beneath the acromial arch, which sets a limit to
the movement. In this condition a little more movement down
of the head, either by muscles depressing it or by force elevating
the farther end of the bone, will throw it out of place, giving rise
to dislocation.

In adduction, the head of the humerus rises in the socket, and
the coraco-humeral ligament being tightened checks the movement.
In circumduction, the humerus passes in succession through the
four different states above mentioned, and the limb describes a
cone, the apex of which is at the shoulder and the 1mse at the
digits.

are accom-
panied by
rotation of
scapula.

Checks to
movements.

Abduction.

Adduction.

Circum-
duction.

LIGAMENTS OF THE ELBOW-JOINT.

notation. There are two kinds of lotatorj- moveineiit, viz., in Rotation;
and out ; and in eacli the humerus revolves around an axis passing
from the centre of the head through the shaft to the lower end of
the bone.

In rotation in, the great tuberosity moves forwards and inwards, in, and
tlie head of the bone glides backwards in the glenoid cavity,
and the hinder part of the capsule is

rendered tense. In rotation out, the ^^^ out.

movements of the parts of the humerus
are reversed, and the front of the cap-
sule is stretched. The movements are
stopped by the tightening of the cap-
sule, assisted by the muscles on the back
and front of the joint respectively.

THE ELBOWS-JOINT.

5— J

Dissection. To make the necessary
dissection of the ligaments of the elbow,
the brachialis anticus must be taken
away from the front, and the triceps
from the back of the joint. The
muscles connected with the outer and
inner condyles of the humerus, as
well as the supinator brevis and the
flexor profundus digitorum, are to be
removed. With a little cleaning the
four ligaments — anterior, posterior,
and two lateral — will come into view.

The interos-seous membrane between
the bones of the forearm will also be
prepared by the removal of the muscles
on both surfaces.

The Elbow- Joint (fig. 39). In
this articulation the lower end of the
humerus is received into the hollow
of the ulna, so as to produce a hinge-
like arrangement ; and the upper end
of the radius assists to form the outer
part of the joint. Where the bones
touch, the surfaces are covered with
cartilage ; and they are united by the
following ligaments : —

The external lateral ligament is a roundish fasciculus, which is
attached by one end to a depression below^ the outer condyle of
the humerus, and by the other to the orbicular ligament roimd the
head of the radius. A few of the posterior fibres pass backwards
to the external margin of the olecranon.

The internal lateral ligament is triangular in shape. It is pointed
at its upper extremity, and is connected to the inner condyle of

Dissection
of the elbow-
joint.

Fig. 39. — The Ligaments of
THE Elbow-Joint, and op
THE Radius and Ulna
(Bourgery).

1. Capsule of the elbow-joint.

2. Oblique ligament.

3. Interosseous membrane.

4. Aperture for blood-vessels.

5. Tendon of the biceps.

Bones
forming the
elbow-joint.

External

lateral

ligament.

Internal

lateral

ligament.

DISSECTION OF THE UPPEK LIMB.

Anterior
ligament.

Posterior
ligament.

Dissection.

Synovial
membrane.

Lower end
of the
humerus :

two articu-
lar surfaces,

and three

Upper end
of the ulna.

Head of the
radius.

Kinds of
motion :

bending ;

the humerus. The fibres diverge, and are inserted in this way : —
The anterior, which are the strongest, are fixed to the edge of the
coronoid process ; the posterior are attached to the side of the
olecranon ; and a few middle fibres join a band passing transversely
over the notch between the olecranon and the coronoid process. The
ulnar nerve is in contact with the ligament ; and vessels enter the
joint by the aperture beneath the transverse band.

The anterior ligament is thin, and its fibres are separated by
intervals in which masses of fat are lodged. By its upper edge
the ligament is attached to the front of the humerus, and by its
lower to the front of the coronoid process and the orbicular
ligament of the radius. The brachialis anticus muscle covers it.

The posterior ligament is much thinner and looser than the
anterior, and is covered completely by the triceps muscle.

Superiorly it is attached to the humerus above the fossa for the
olecranon ; and inferiorly it is inserted into the olecranon. Some
few fibres are transverse between the margins of the fossa before
mentioned.

Dissection. Open the joint by an incision across the front near
the humerus, and disarticulate the bones, in order that the articular
surfaces may be seen.

The synovial membrane of the joint passes from one bone to
another along the deep surface of the connecting ligaments. It is
continued downwards on the inner surface of the orbicular ligament,
and serves for the joint of the head of the radius with the small
sigmoid cavity of the ulna.

Articular surfaces. The articular surface of the lower end of
the humerus is divided into two parts for the bones of the forearm.
That for the radius, on the outer side, forms a rounded eminence
(capitellum) which is confined to the front of the Ijone. The
surface in contact with the ulna (trochlea) is limited internally
and externally by a prominence, and hollowed out in the centre.
On the front of the humerus above the articular surface are two
depressions which receive the coronoid process of the ulna and the
head of the radius during flexion of the joint; and on the posterior
aspect is a large fossa for the reception of the olecranon in extension
of the joint.

On the end of the ulna the articular surface of the great sigmoid
cavity is narrowed in the centre, but expanded above and below
(fig. 40). A median ridge, which is received into the hollow of
the trochlea, extends from the upper to the lower end of the fossa ;
and across the bottom of the cavity the cartilage is wanting over a
small space between the coronoid and olecranon processes.

The head of the radius presents a circular depression with a
raised margin, which plays over the capitellum of the humerus.

Movement. This joint is like a hinge in its movements, per-
mitting only flexion and extension.

Inflexion, the bones of the forearm move forwards, each on its
own articular surface, so as to leave the back of the humerus
uncovered. The movement is checked by the meeting of the arm

UNION OF RADIUS AND ULNA.

and forearm ; and the posterior and internal lateral ligaments are
stretched.

In extension, the ulna and radius move on the articular surface extending,
of the humerus until they come into a line with the arm-bone.
This movement is checked by the anterior ligament, and the muscles
on the front of the joint.

Union of the Radius and Ulna. The radius is connected Radius is
with the ulna at both ends l)y means of synovial joints and sur- ^^^^^ ^
rounding ligaments ; and the shafts of the l)ones are united by
interosseous ligaments.

Upper radio-ulnar articulation. In this joint the head of at the upper
the radius is received into the small sigmoid cavity of the ulna, and ®°^ ^^
is kept in place by the following
ligamentous band : —

The annular or orbicular liga-
ment (fig. 40, a) is about one-
third of an inch wide, and is
stronger behind than before ; it

]tlaced around the prominence

the head of the radius, and is
attached to the anterior and pos-
terior edges of the small sigmoid
cavity of the ulna. Its upper
l)order, the thicker, is connected
Avith the ligaments of the elbow-
joint ; Imt the lower is free, and
is applied around the neck of the
radius. In the socket formed by
this ligament and the cavity of
tlie ulna the radius moves freely.

The synovial membrane is a
prolongation of that lining the
ellx)w-joiut ; it projects inferiorly

between the neck of the radius and the lower margin of the annular
ligament.

Ligaments of the shafts of the bones. The aponeurotic Union of the
stratum connecting together the bones nearly their whole length
consists of the two following parts : —

The interosseous membrane (fig. 39, ^) is a thin fibrous layer, which interosseous
is attached to the contiguous margins of the radius and ulna, and " ^^^
forms an incomplete septum between the muscles on the front and
Ijack of the forearm. Most of its fibres are directed obliquely
downwards and inwards, though a few on the posterior surface have
an opposite direction. Superiorly, the membrane is wanting for a is deHclent
considerable space, and through the interval the posterior inter-
osseous vessels pass backwards. Some small apertures exist in it
for the passage of vessels ; and the largest of these (^) is about two
inches from the lower end, through which the anterior interosseous
artery turns to the Ijack of the wrist. ITie membrane gives
attachment to the deep muscles.

D.A. H

Fig. 40.— View of the Orbicular
Ligament («), which retains
THE Upper End of thk Radius synovial

AGAINST THE UlNA.

membrane.

DISSECTION OF THE UPPER LIMB.

oblique
ligament.

The lower
end after.

Kind of
motion of
radius :

Ijronation,

sui)ination

axis of
motion

use of
ligaments ;

in fracture
motion

The oblique ligament (fig. 39, -) is a slender band above the
interosseous membrane, the fibres of which have a direction opposite
to those of the membrane. By one end it is fixed to the lower end
of the coronoid process, and by the other to the radius below
the tuberosity. The ligament divides into two the space above
the interosseous membrane. Oftentimes this band is not to be
recognised.

The lower radio-ulnar articulation cannot be well seen till after
the examination of the wrist-joint.

Movement of the radim. The radius moves forwards and
backwards upon the ulna. The forward motion, directing the
palm of the hand backwards, is called pronation ; and the back-
ward movement, l)y which the palm of the hand is turned to the
front, is named supination.

In pronation, the upper end of the bone rotates within the band
of the orbicular ligament without shifting its position to the ulna.
The lower end, on the contrary, moves over the ulna from the outer
to the inner side, describing nearly half a circle ; and the shaft
crosses obliquely that of the ulna.

In supination, the lower end of the radius turns backwards over
the ulna ; the shafts come to be placed side by side, the radius
being external ; and the upper end rotates from within out in its
circular band.

In these movements the radius revolves round an axis, internal
to the shaft, which is prolonged upwards through the neck and
head of the ])one, and downwards through the styloid process of
the ulna.

The upper end of the l)one is kept in place by the orbicular
ligament ; the lower end by the triangular fibro-cartilage ; and the
shafts are united by the interosseous ligament, which is tightened
in supination, and relaxed in pronation.

In fracture of either bone the movements cease ; in the one case
because the radius cannot Ije moved unless it is entire ; and in the
other because the broken ulna cannot support the revolving radius.

THE WRIST-JOINT.

bissection.

Bones form-
ing wrist-
joint
united by

external
lateral.

Dissection. To see the ligaments of the wrist-joint, the tendons
and the annular ligaments must be removed from both the front
and back ; and the fibrous structures and the small vessels should
be taken from the surface of the ligaments.

The Wrist- Joint (radio-carpal articulation; fig. 41). The
lower end of the radius, and the first row of the carpal bones,
except the pisiform, enter into this joint. Four ligaments connect
the bones, viz., anterior and posterior, and two lateral. The ulna
is shut out from the articulation by a piece of fibro-cartilage.

The external lateral ligament is a short Imnd, which passes
from the styloid process of the radius to the outer part of the
scaphoid l3one.

THE WRIST-JOINT.

The internal lateral ligament is longer and thicker than the
external. It is attached by one end to the styloid process of the
ulna, and l)y the other to the rough upper part of the pyramidal
bone. Some of the anterior fibres are continued to the pisiform bone.

The anterior ligament (fig. 41, i) springs from the radius, and is
inserted into the first row of carpal bones, except the pisiform on
the anterior surface.

The posterior liganunt (fig. 44, \ p. 103) is membranous, like the
anterior, and its fibres are directed downwards and inwards from
the radius to the same three
carpal bones on the posterior
aspect.

Dissection. To see the
form of the articular sur-
faces, the joint may be
opened by a transverse in-
cision through the posterior
ligament, near the bones of
the carious.

Articular surfaces. The
end of the radius, and the
fibro-cartilage (fig. 42, c)
uniting it with the ulna
form a shallow socket for
the reception of the carpal
bones ; and the surface of
the radius is divided by a
prominent line into an ex-
ternal triangular, and an
internal square impression.
The three carpal bones of
the first row constitute a
convex eminence, which is
received into the hollow
lief ore mentioned in this
way : the scaphoid bone is

opposite the external triangular mark of the radius ; the semilimar
bone touches the square impression and the greater part of the
triangular fibro-cartilage ; while the small articular surface of the
pyiamidal bone is in contact with the apex of the fibro-cartilage
and the adjoining part of the capsule.

The synovial membrane has the arrangement common to simple
joints. This joint communicates occasionally with the lower radio-
ulnar articulation by means of an aperture in the fibro-cartilage
between the two.

Movements. The principal movements taking place in the radio-
carpal articulation are flexion and extension. Lateral motion occurs
only to a limited extent.

Flexion and extension. In flexion the hand is moved forwards,
while the carpus glides on the radius from before backwards, and

H 2

internal
lateral,

anterior and

posterior
ligaments.

Dissection.

Surface of
radius :

Fig. 41. — Front View of the Articu-
lations OF THE Wrist, and Carpal
AND Metacarpal Bones (Bourgery).

1. Anterior ligament of the wrist- joint.

2. Capsule of the joint of the metacarpal
bone of the thumb with the trapezium.

3. Pisiform bone, with its ligamentous
bands.

4. Transverse bands uniting the bases
of the metacarpal bones.

of fii-st row
of carjjal
bones :

opposed
surfaces.

Synovial
sac.

Kinds of
motion :

flexion ;

100

DISSECTION OF THE UPPER LIMB.

extension.

Lower ends
of radius
and ulna
joined by-

capsule,

triangular
tibro-carti-
lage:

attach-
ments,

and lela-
tions.

Synovial
membrane.

Bones are
joined into
two rows.

Dissection
of carpal

and meta-

cari)al

joints.

How first
row is
united

projects behind, stretching the posterior ligament. In extension
the hand is carried backwards, and the row of carpal bones moves
in the opposite direction, viz., from behind forwards, so as to cause
the anterior ligament to l)e tightened. The backward movement
is not so free as the forward.

Lower radio-dlnar articulation. In this articulation the
head of the ulna is received into the sigmoid cavity of the radius ;
— an arrangement just the opposite to that between the upper ends
of the l)ones.

The chief bond of union between the bones is a strong libro-
cartilage ; but a capsule, consisting of scattered fibres, surrounds
loosely the end of the ulna.

The triangular fibro-cartilage (fig. 42, c) is placed transversely
below the end of the ulna, and is thickest at its margins and apex.
By its base the cartilage is fixed to the ridge which separates the
carpal from the ulnar articulating surface of the radius ; and by its

apex to the styloid process of the
ulna, and the depression at the root
of that projection. Its margins are
united with the contiguous anterior
and posterior ligaments of the wrist-
joint ; and its surfaces enter into the
radio-carpal and the lower radio-ulnar
articulations. It serves to unite the
radius and ulna, and to form part
of the socket for the carpal bones.
Occasionally it is perforated by ai\
aperture. ' \

The synovial membrane is very
loose, and ascends between the radius
and the ulna : it is separated from
that of the wrist - joint by the
triangular fibro-cartilage.
The motion in this articulation is referred to with the movements
of the radius (p. 98).

Union of the Carpal Bones. The several bones of the carpus
(except the pisiform) are united into two rows by small dorsal,
palmar, and interosseous bands ; and the two rows are connected
together by wide separate ligaments.

Dissection. The articulations of the carpal bones with each other
will be prepared by taking away all the tendons from the hand, and
cleaning carefully the connecting ligamentous bands. Two distinct
ligaments from the pisiform bone to the unciform {pisi-unciform)
and to the fifth metacarpal (jJ^'si-riietacarpal) are to be defined in the
palm (p. 62).

At the same time the ligamentous bands uniting the meta-
carpal with the carpal bones, and with one another should be
dissected.

Bone8 of the first row (fig. 43). The semilunar bone is
united to the scaphoid and pyramidal by dorsal (d) and palmar

Fig. 42. — Lower Ends of the
Forearm Bonks with the
Uniting Fibro-Cartilage.

a.- Radius. b. Ulna.

c. Triangular fibro-cartilage.

ARTICULATIONS OF THE CARPUS.

101

Separate
ligaments of
pisiform

Second row
is like first.

degree

transverse bands ; as well as by small interosseous ligaments at the
upper part of the contiguous surfaces.

The pisiform bone is articulated to the front of the pyramidal by
a distinct capsule and synovial sac. It has further two special liga-
ments ; one of these is attached to the process of the unciform, and
the other to the base of the fifth metacarpal bone.

The BONES OF THE SECOND ROW (fig. 43) are connected together
in the same way as those of the first, viz., by a doisal (i) and a
palmar band of fibres from one bone to another. Between the con-
tiguous rough surfaces of

the several bones are in- a^^^^M^^

terosseous ligaments, one in
each interval.

Movement. Only a small
of gliding motion
is permitted l)etween the
different carpal bones of
each row, in consequence
of the flattened articular
surfaces, and the short
ligaments uniting one to
another ; and this is less
in the second than in the
first row.

One row with another
(transverse carpal joint ;
fig. 43). The two rows
of carpal bones are con-
nected by an anterior and
posterior, and two lateral
ligaments.

The anterim' ligament ( p)
consists of strong filn-es,
which for the most part
converge from the three
bones of the first row to
the OS magnum. The

posterioi' ligament is thinner and looser ; and its strongest fibres posterior,
are transverse.

Of the lateral ligaments the external (k) is the better marked, and
extends between the trapezium and scaphoid bones ; the internal {I)
passes from the pyramidal to the unciform bone.

Dissection. After the division of the lateral and posterior liga- Dissection
ments, tJie one row of bones may be separated far enough from the
other to allow the articular surfaces to be seen.

Articular surfaces. The three bones of the first row, viz.,
scaphoid («), semilunar (6), and pyramidal (c), together form an
arch with its concavity turned downwards, while externally the
scaphoid presents a convexity to the second row. The lower arti-
cular surface has a corresponding form, the os magnum and unciform

Fig. 43. — Articulations op the Carpal
Bones, the Joint between the Two
Rows being Opened Behind.

a. Scaphoid bone.
h. Semilunar.

c. Pyramidal.

d. Dorsal trans-
veree bands between
those bones.

€. Trapezium.
/'. Trapezoid.
g. Os magnum.
h. Unciform.

i. Dorsal trans-
verse bands joining
the bones.

h. Externallateral
ligament of the inter-
carpal joint.

I. Internal lateral
ligament.

p. Anterior liga-
ment.

anterior,

and lateral
ligaments.

Form of
joint-sur-
faces.

102

DISSECTION OF THE UPPER LIMB.

One synovial
cavity for
tlie carpal
bones,

and some
meta-
carpals.
Kinds of
motion :

flexion ;

extension.

Combined
movements
of radio-
carpal and
transverse
carpal
joints ;

flexion and
extension ;

abduction ;

adduction ;

and circum-
duction.

Metacarpal
bones joined
at bases,

with

synovial

joints,

and at

making up a condyloid projection which is received into the arch
of the first row, and the trapezium and trapezoid forming a slight
hollow for the couA^exity of the scai)hoid bone.

One synovial sac serves for the articulation of all the carpal hones,
except the pisiform with the pyramidal. The cavity extends trans-
versely between the two rows of the carpus, and is continued
upwards and downwards between the individual bones. The offsets
upwards are two, and they sometimes open into the cavity of the
wrist-joint ; but the offsets in the opposite direction are three, and
may be continued to all, or only to the two outer of the four
inner carpo-metacarpal joints.

Movements. Owing to the irregular shape of the articular
surfaces, only forward and backward movements are permitted in
the transverse carpal joint.

Flexion. As the hand is brought forwards, the os magnum and
unciform move backwards in the socket formed by the first row,
while the trapezium and trapezoid advance over the scaphoid, and
the posterior ligament is tightened.

Extension. The backward movement is freer than flexion. The
trapezium and trapezoid glide l)ackwards over the scaphoid, and the
OS magnum and unciform project on the palmar aspect, the move-
ment l)eing checked by the anterior ligament of the joint and the
strong flexor tendons.

The axes upon which the movements of flexion and extension of
the radio-carpal and transverse carpal joints take place are not
strictly transverse, but oblique in opposite directions, that of the
proximal articulation ha\'ing its inner end directed forwards, while
that of the distal articulation is inclined from without inwards and
backwards. In order therefore to move the hand directly forwards
or backwards, both joints are called into play simultaneously. By
a combination of flexion in the one joint with extension in the
other, lateral movements {abduction and adduction) of the hand are
produced. Thus, abduction results from flexion of the radio-c^irpal
and extension of the transverse carpal articulation, and adduction,
which is the freer movement, from extension of the radio-carpal
and flexion of the transverse carpal joint. In circumd.uctio7i the
hand passes successively through the several states of angular move-
ment, descril)ing a cone with the apex at the wrist, and the
excursion is greater in the direction of flexion and adduction than
in the opposite directions.

Union of the Metacarpal Bones. The meUicarpal bones of
the four fingers are connected at their bases by the following liga-
ments: — A dorsal (fig. 44) and palmar (fig. 41) fasciculus of fibres
passes transversely from each bone to the next ; and the bands in
the palm are the strongest. Besides these, there is a short interosseous
ligament between the contiguous rough surfaces of the bones.

Where the metacarpal bones touch they are covered by cartilage ;
and between the articular surfaces there are prolongations of the
synovial cavity serving for their articulation with the carpus.

At their__distal ends the same four metacarpal bones are connected

CARPO-METACAEPAL ARTICULATIONS.

103

Motion

bending

by the transverse ligament^ which was seen in the dissection of the
hind (p. 81).

Union of the Metacarpal and Carpal Bones. The meta- carpai and
cariml lx)nes of the fingers are articulated with the carpal liones |^f^^^^^
after one plan ; but the lx)ne of the thumb has a separate joint.

The metacarpal bone of tlie thumb articulates with the trapezium ; That of the
and the ends of the ]>ones are encased in a capsular ligament thumb,
(fig. 41, 2), which is lined
by a simple synovial mem-
brane.

The thumb - joint pos-
sesses angular movement
in opposite directions, with
opposition and circumduc-
tion, thus : —

Flexion and extension.
When the joint is flexed,
the metacarpal lx)ne is
brought in front of the
palm ; and as the move-
ment proceeds, the thumb
is gradually turned towards
the fingers, passing into the
state of opposition. In this
way the thumb may be
made to touch the palmar
surface of any or all of the
fingers, the phalanges of the
latter being somewhat bent
at the same time. Exten-
sion of the joint is very
free, and by it the meta-
carpal bone is removed from the pahn towards the outer border of
the forearm.

Abduction and adduction. By these movements the thumb is and lateral
placed in contact with, or removed from the forefinger. "™^ ***"'

The metacarpal bones of the fingers receive longitudinal bands Joints of
from the carpal lx)nes on both aspects, thus : — "°^

The dorsal ligaments (fig. 44) are two to each, except to the bone have dorsal
of the little finger. The bands of the metacarpal bone of the fore-
finger come from tlie trapezium and trapezoid : those of the third
metacarpal are attached to the trapezoid and os magnimi ; the bone
of the ring finger receives its bands from the os magnum and
unciform ; and to the fifth metacarpal bone there is but one
ligament from the uncifonu.

The palmar ligaments (fig. 41), usually one to each metacarpal and palmar
bone, are weaker and less constant than the dorsal. These liga- *" '' '
ments may be oblique in direction ; and sometimes a band is di^^ded
between two, as in the case of a ligament passing from the trapezium
to the second and third metacarpals. One or more may be wanting

Fig. 44. — Postbrior Ligaments of the
Wrist, and Carpal and Metacarpal
Bonks (Bourgkry).

1. Posterior radio-carpal.

2. Carpo - metacarpal capsule of the
thumb.

3. 3. Transverse bands between the extending;
bases of the metacarpal bones.

104

DISSECTION OF THE UPPER LIMB.

lateral band

Very little
motion.

Dissection.

Articular
surfaces.

and contact.

Synovial
.sacs, two

or three.

Interosseous
ligaments,

metacarpal,
and carpal.

Metacarpo-
I)halangeal
articula-
tions ;

Dissection
of finger-
joints.

lateral
ligaments ;

On the ulnar side of the metacarpal hone of the middle digit is
a longitudinal lateral harid, which is attached above to the os mag-
num and unciform, and below to a rough part on the inner side of
the base of the above mentioned bone. Sometimes this band
isolates the articulation of the last two metacarpals with the
unciform l)one from the remaining carpo-metacarpal joint ; but
more frecLuently it is divided into two parts, and does not form a
complete partition.

This band may be seen by opening from behind the articulation
Ijetween the unciform and the last two metacarpal bones ; and by
cutting through the transverse ligaments joining the third and
fourth metacarpals so as to allow their separation.

Movement. Scarcely any appreciable antero-posterior movement
exists in the articulations of the bases of the metacarpal l)ones of
the fore and middle fingers ; but in the ring and little fingers the
motion is greater, with a slight degree of opposition.

Dissection. The articular surfaces of the bones in the carpo-
metacarpal articulation may be seen by cutting through the rest of
the ligaments on the posterior aspect of the hand.

Articular surfaces. The metacarpal bone of the forefinger has
a broad, notched articular surface, which receives the prominence
of the trapezoid bone, and articulates laterally with the trapezium
and OS magnum. The middle finger metacarpal articulates with
the OS magnum. The metacarpal bone of the ring finger touches
the unciform bone and the os magnum. And the little finger bone
is opposed to the unciform.

Synovial sacs. Usually two synovial sacs are interposed between
the carpal and metacarpal bones, viz., a separate one for the bone
of the thumb, and offsets of the common carpal synovial sac (p. 102)
for the others. Sometimes there is a distinct synovial sac for the
articulation of the two inner metacarpals Avith the unciform bone.

Interosseous Ugar)ients. The interosseous ligaments between the
bases of the metacarpal bones may be demonstrated by detaching
one bone from another ; and those uniting the adjacent carpal bones
may be shown in the same way.

Union of Metacarpal Bone and First Phalanx (fig. 45).
In this joint the convex head of the metacarpal bone is received
into the glenoid fossa of the phalanx, and the two are united by
the lateral, anterior and posterior ligaments.

Dissection. For the examination of this joint it will be requisite
to clear away the tendons and the tendinous expansion around it.
A lateral ligament on each side, and an anterior thick band are to
be defined. One of the joints may l)e opened to see the articular
surfaces.

The same dissection may be made for the articulations between
the phalanges of the fingers.

The lateral ligaments (a) are triangular in form ; attached above
to the lower part of the tubercle on the side of the head of the
metacarpal bone, and below the phalanx and to the anterior
ligament.

JOINTS OF PHALANGES.

105

The anterior ligament (b) is a strong and dense band, which is
fixed firmly to the phalanx, but loosely to the metacarpal bone.
It L« grooved for the flexor tendon ; and to its sides the lateral
ligaments are united.

On the dorsal aspect of the joint, the capsule is completed by
a thin layer of connective tissue which supports the syno\dal
membrane, and is closely covered by the extensor tendon. The
synovial membrane of the joint is a simple sac.

In the articulation of the thumb two sesamoid bones are con-
nected with the anterior ligament, and receive most of the fibres of
the lateral ligaments.

Movements. Motion in four opposite directions, together with
circumduction, take place in these condyloid joints.

Flexion and extension. In flexion, the phalanx glides forwards
over the head of the metacarpal bone, find leaves this exposed to
form the knuckle when the finger
is shut. The lateral ligaments and
the extensor tendon are put on the
stretch as the joint is bent. In
txtension the anterior ligament and ,
the flexor tendons are stretched, and
limit the movement.

Abduction and adduction are the
lateral movements of the finger
from or tow^ards the middle line
of the hand. The lateral ligament
of the side of the joint which is
rendered convex is tightened, and
the other is relaxed.

The circumductory motion is less
impeded in the fore and little

fingers than in the others. In the joint of the thumb the movements,
especially to the side, are much less extensive than in the fingers.

Union of the Phalanges. The ligaments of these joints are
similar to those in the metacarpo-phalangeal articulations, viz., two
lateral, an anterior and a membranous posterior.

The lateral ligaments are triangular in form. Each is connected
by its apex to the proximal phalanx at the side of the head ; and
by its base to the distal phalanx and the anterior ligament.

The anterim- ligament has the same mode of attachment between
the extremities of the bones as in the metacarpo-phalangeal joint,
but it is not so strong.

There is a simple synovial membrane present in the joint.

The joint of the second with the last phalanx is like the pre-
ceding in the number and disposition of its ligaments ; but all the
articular bands are much less strongly marked.

Articular surfaces. The head of each phalanx is marked by a
pulley-like surface. The base presents a hollow on each side of a
median ridge, which fits into the central depression of the opposed
articular surface.

anterior
ligament ;

posterior.

Synovial
sac.

Joint of
thumb.

Kinds of
motion :

bendins

extending

lateral
motion

Fig. 45.

circumduc-
tory.

Joints of the

Ijhalanges

have

lateral and

anterior
ligaments.

Synovial
sac.

Last joint.

Surfaces of
the bones.

106

DISSECTION OF THE UPPER LIMB.

Kinds of
motion :

bending,

extending.

Movements. The two interphalangeal joints can be bent and
straigbtened like a hinge.

Flexion and extension. In flexion, the distal phalanx moves
round the proximal in each joint, and the motion is checked by
the lateral ligaments and the extensor tendon : in the joint between
the middle and the metacarpal phalanx this movement is most
extensive. In extension the farther phalanx comes into a line
with the nearer one, and the motion is stopped by the anterior
ligament and the flexor tendons.

CHIEF ARTEKIES OF THE UPPER LIMB.

107

TABLE

OF THE CHIEF ARTERIES OF THE UPPER LIMB.

/I. Axillary
artery.

Tlioracic axis
long thoracic
alar thoracic

Acromial
thoracic (superior)

I clavicular
Uiumeral.

(Doraal scapular J,^""^"^^^-
\ muscular. ^ P"^*^'

subclavian is
)ntinup<l in the
m by

2. brachial
arterj' .

3. radial
artery .

4. ulnar
artery

subscapular .

anterior circumflex

posterior circumflex

\extemal mammary (occasional).

(Muscular to triceps

■Superior profunda. . • |„,-'™tTnd\"L»tom«Uc

medullary

j Muscular to triceps
inferior profunda . . ■ \ anastomotic.

anastomotic

y^ muscular.

Reciurrent
muscular
superficial volar
anterior cari>al

posterior carpal

doi-sal interosseous

dorsal of thumb

dorsal of index finger

palmar of thumb (princeps poUicis)

radial of index finger
\deep arch

(Recurrent
I)erforating
palmar inter-
osseous.

/Anterior recurrent
posterior reciuxent
interosseous
muscular
\ anterior cariial
posterior carpal
communicating to deep arch
superficial arch .

posterior

j Medullary
\ median
(muscular.

( Recurrent
' \ muscular.

j Four digital branches
- cutaneous
I muscular.

108

SPINAL NERVES OF THE UPPER LIMB.

TABLE OF THE SPINAL NERVES OF THE UPPER LLMB.

Sxternal
nternal.

/ Anterior thoracic . -f External

subscapular

circumflex

Brachial
Plexus gives
oft" below the
clavicle .

[ Superior

4 middle or long

( inferior.

(Articular
cutaneous
to teres minor
to deltoid.

nerve of Wrisberg

. , , , I cutaneous in arm

internal cutaneous . J anterior of forearm
( posterior of forearm.

musculo-cutaneou;

median

ulnar

i' To coraco-brachialis,
biceps and
brachialis anticus
external cutaneous of forearm
articular to carpus.

/To pronator teres, flexor carpis ^ „

radialis, palmaris longus, and flexor I " "f,^°r ^ongrn^

. sublimis digitorum , voihciii

• ■{ anterior interosseous . . J '^'^ flexor profundus

cutaneous palmar " "} , digitorum in part

to muscles of thumb in pait ^° pronator

Vflve digital branches. \ <l"adratus.

Articular to elbow
to flexor carpi ulnaris
to flexor profundus in part
cutaneous branch of forearm and
/ palm
dorsal cutaneous of the hand

superficial palmar diA'ision .

^ deep palmar nerve.

/Communicating
I two digital
branches
( to palmaris brevis.

musculo-spiral

/Internal cutaneous
' to triceps

and anconeus
external cutaneous, upper and lower
to supinator longus and exten.sor
carpi radialis longior

posterior interosseous

Sadial

J Muscular
( articular.

/ Cutaneous of back
I of hand, of
thumb, of index
and middle fingers
and half the ring.

CHAPTER III.
DISSECTION OF THE LOWER LIMB.

Section I.

THE BUTTOCK, OK THE GLUTEAL REGION.

hiredions. Both this Section and the following; one are to he Directions,
completed hy the student in the four days appointed for the
l>ody to lie in the prone position, and the student who is com-
licncing his work in practical anatomy by the dissection of the

^\'er limb should read the gefural directions for the beginner
"U p. 1 before proceeding Avith this section.

Position. During the dissection of the back of the thigh the Position of
1 K )dy is placed mth the face down and the pelvis is to be well ^^^ ^'
raised by blocks.

Surface marking. At the upper part of the buttock, by Surface-
exercising deep pressure, the student will make out the crest of
the iliac bone, and on tracing this inwards the posterior superior
iliac spine will be felt opposite the second sacral spine ; and
tliis part marks the middle of the sacroiliac joint. Internally
the lower part of the sacrum and the coccyx will be found at the
liottom of the natal furrow. Inferiorly, the thick fold of the nates
is very CA-ident, and above this the mass of the gluteiLS maximus
muscle contributes largely to the prominence of the buttock.
About three or four inches below the anterior part of the iliac
crest on the outer side of the thigh is the great trochanter of the
femur, and by pressing upwards beneath the inner part of the fold
of the nates the tuberosity of the ischium can be felt. A line
(Nelaton's) drawn from the anterior superior iliac spine to the
most prominent part of the ischial tuberosity passes just over the
highest part of the great trochanter and is used in surgery for
ascertaining the degree of displacement of that jjart of the bone
in various conditions.

Dissection. The integument is to be raised from the buttock Take up the
by means of the following incisions (fig. 1, a, p. 3) — One is to be
made along the whole length of the iliac crest, and continued in
the middle line of the sacrum to the tip of the coccyx (g). Another
is to be l)egun where the first terminates, and is to be carried out-
wards and downwards across the thigh, ending alx)ut six inches

110 DISSECTION OF THE BUTTOCK.

below the great trochanter (h). The flap of skin thus marked out
is to be thrown forwards,
seek cuta- Many of the cuUmeous nerves of this region will be found in the

onttfe^cS ^^t along the line of the iliac crest (fig. 46). Thus, in front, but
rather below the crest, are branches of the external cutaneous.
Crossing the crest towards the fore part is a large offset of the last
dorsal nerve ; and usually farther back, but close to the bone, a
smaller l^ranch from the ilio-hypogastric nerve. At the outer
border of the erector spinsD are two or three branches of the
lumbar nerves.

and by .side By the side of the sacrum and coccyx two or three offsets of the
of sacrum : g^cral nerves are to be looked for beneath the fat.
other nerves The remaining cutaneous nerves are derived from the small
sciaSc^^ sciatic, and must be sought beneath the fat along the line of the
below: lower incision, where they come from underneath the gluteus

maximus. Some turn upwards over that muscle, and others are
directed down the thigh,
cutaneous Cutaneous arteries accompany all the nerves, and will serve as

arteries. g^^i^jes to their situation.

Sources of CuTANEOUS Nerves (fig. 46, also fig. 2, p. 4). The nerves

^!*^^"^"f, distributed in the integuments of the buttock are small but

numerous, and are derived from the last dorsal nerve, from

branches of the lumbar and sacral plexuses, and from the posterior

primary divisions of the lumljar and sacral nerves.

from last The LAST DORSAL NERVE (fig. 46) (^) Supplies the buttock by

dorsal ; means of its lateral cutaneous l)ranch. This oftset perforates the

muscles of the abdomen, and crosses the front of the iliac crest

to be distributed over the fore part of the gluteal region, as low as

the great trochanter.

from lumbar Nerves OF THE LUMBAR PLEXUS. Parts of two nerves of the

p exus, plexus of the lumbar nerves, viz., ilio-hypogastric from the first,

and the external cutaneous from the second and third, are spent in

the integuments of this region.

through The iliac branch of the ilio-hypogastric (^) crosses the iliac crest in

gastrS and ^^^^^ ^^ ^^^ lumbar nerves, lying in a groove in the bone, and

extends generally only a short distance l)elow the crest,
external Ofi'sets of the posterior branch of the external cutaneous nerve of

cu aneous ; ^^^ thigh bend l)ackwards to the integuments above the great
trochanter, and cross the ramifications of the last dorsal nerve
(see fig. 2, p. 4).
froinpos- Posterior primary branches. The oftsets of the posterior

branches of primary pieces of the lumbar nerves (^) are two or three in number,
lumbar ^nd cross the crest of tlie ilium at the outer edge of the erector
spinse ; they ramify in the integuments of the middle of the buttock,
and some branches may be traced nearly to the great trochanter,
and sacral The branches of the sacral nerves (^) perforate the gluteus maxi-

mus neiir the sficrum and coccyx, and are then directed outwards
for a short distance in the integuments over the muscle. These
ofi'sets are usually two in number : the largest is opposite the lower
end of the sacrum, and the other by the side of the coccyx.

nerves ;

CUTANEOUS NERVES.

Ill

Small sciatic C). This nerve of the sacral plexus sends super- from^sacral
ficial branches to the buttock. Its cutaneous offsets appear along ^' *'^"'''

Fig. 46. — Sui'Krficial View of the Buttock of the Left Side
(Illustrations op Dissections).

A. Gluteus maximus muscle, with
the gluteus medius projecting above it.

a. Continuation of sciatic artery
along the back of the thigh.

Nerves :

1. Small sciatic trunk.

2. Its cutaneous thigh branches.

3. Inferior pudendal.

4. Branches of perforating cuta-
neous.

5. Cutaneous of the sacral.

6. Posterior branches of the lumbar
nerves.

7. Ilio-hypogastric.

8. Last dorsal.

the lower border of the gluteus maximus, accompanied by super- througi
ficial Ijranches of the sciatic artery ; two or three ascend round the gdatic,
edge of the muscle, and are lost in the integuments of the lower

112

DISSECTION OF THE BUTTOCK.

and perfo-
rating
cutaneous
branch.

Clean
gluteus
maximus ;

mode of
proceeding.

Fascia of the
buttock.

part of the Inittock ; the remaining branches (2) descend to the
thigh, and will be afterwards noticed on it (p. 130).

The PERFORATING CUTANEOUS NERVE of the sacral plexus (^)
turns round the edge of the gluteus maximus near the coccyx, and
supplies the skin of the adjacent part of the buttock : this nerve
has been exposed in the dissection of the perineum.

Dissection. The thin and unimportant deep fascia of this region
may be disregarded, in order that the great gluteal muscle, which
is one of the most difficult in the l)ody to clean, may be well dis-
played. To lay bare the muscle, let the student turn aside the
cutaneous nerves, and adduct and rotate inwards the limb to make
tense the muscular fibres. Having cut through the fat and fascia
from the origin to the insertion, let him carry the scalpel along one
bundle of fibres at a time in the direction of a line from the sacrum
to the femur, until all the coarse fasciculi are cleaned. If the
student has a right limb, it will be more convenient to begin the-
dissection at the upper border ; l)ut if a left limb, at the lower
margin of the muscle.

The fascia of the buttock is a prolongation of that enveloping the
thigh, and is fixed to the crest of the ilium, and to the sacrum and

Gluteus
maximus :

origin

maximus, and gives attachment superiorly to the gluteus medius,
which it covers ; in this place, indeed, the student often has some
difficulty in defining the edge of the greater gluteus, since at the
edge of the muscle the fascia splits to encase it.

The GLUTEUS MAXIMUS (fig. 46, a) is the most superficial
muscle of the Ijuttock, and reaches from the pelvis to the upper
part of the femur. Its origin from the pelvis is fleshy, and is
connected with bone and with aponeurosis : — Thus, the muscle is
attached, from above down, to the posterior fourth of the iliac
crest, and to a special impression on the hip-l)one above the superior
curved line (fig. 47) ; next, to the aponeurosis of the erector spinse
muscle ; then to the back of the fourth and fifth pieces of the
sacrum, and the back of the coccyx ; and lastly, to the back of the
whole length of the great sacro-sciatic ligament. From this
extensive origin the fibres are directed dowuM'ards and outwards to
their iyisertion : — The whole of the upper half of the muscle, and a
few superficial fibres of the lower half are inserted into the strong
fascia lata (ilio-tibial l)and) of the outer side of the thigh ; and the
remainder are fixed into the rough line (gluteal ridge) leading from
the linea aspera to the great trochanter of the femur (fig. 61,
p. 158).

The gluteus forms the prominence of the buttock, and resembles
the deltoid muscle of the arm in its situation and in the coarse-
ness of its texture. Its cutaneous svirface is covered by the common
integument/S and the investing fascia of the limb, and by the superficial
nerves and vessels. The structures in contact with the under surface
will be seen when the muscle is cut through. The upper border
and borders; overlies the gluteus medius. The lower edge, which is longer
and thicker than the upper, in its inner part bounds posteriorly

insertion ;

relations of
the surfaces

THE GLUTEUS MAXIMUS.

113

oil
femur.

the perineal space, and in the rest of its extent lies obliquely acrose
I he back of the thigh. The hamstring muscles and the sciatic
vessels and nerves issue beneath it.

Action. With the femur hanging the muscle extends the hip-joint use
by pulling back that bone. The upper part abducts, but the part
inserted into the femur adducts the limb and rotates it outwards.

When the limb is fixed, and the body is raised from a sitting on pehis,
into a standing posture, the gluteus acts as an extensor of the
articulation by moving back the pelvis ; and in standing on one

Obliquus abdominis internus.

Litissimiis dorsi

Obliquus abdominis extemus.
Tensor fasciae femoris.

SartoriTis.

Straight head ) Rectus
Reflected head i^ femoris.
Pectineus.

Pyriformis,
Gemellus superior.
Gemellus inferior.

Semimembranosus
Semitendinosus and biceps

Adductor longus.

Quadratus femoris
Adductor magnus,

Gracilis.

Adductor brevis.

FiQ. 47. — Os Inxominatum : Outer and Posterior View.

leg, the muscle can draw the sacrum towards the femur, so as to
turn the face to the opposite side.

By tightening the ilio-tibial band (which is attached, below, to and on knee,
the front of the outer tuberosity of the tibia, to the outer side of
the patella and to the fascia over the muscles of the front of the
leg), the gluteus maximus also supports and steadies the knee-
joint in the extended position. In this action it is assisted by the
tensor fasciae femoris, which corrects the tendency of the gluteus
to draw the ilio-tibial band backwards.

Dissection (fig. 48). The gluteus maximus is to be cut across Divide the
a little external to the middle ; and the depth of the muscle will ll^xlmus

D.A. I

114

DISSECTION OF THE BUTTOCK.

clean parts
beneath.

remove
origin,

and dissect
out sacral
nerves.

Parts

covered by
gluteus at
its origin

and inser-
tion :

and by the
intervening
piece of the
muscle.

be ascertained by the fascia and some vessels beneath it. When
this intermuscular layer is arrived at, the outer piece of the gluteus
may be at once thrown towards its insertion ; but the inner piece
is to be carefully raised, and the branches of the inferior gluteal
nerve, and of the gluteal and sciatic arteries entering its deep
surface, are to be cleaned.

The loose fat is then to be taken away from the hollow between
the pelvis and the trochanter, without injuring the vessels and
nerves ; and the several muscles are to be cleaned, the fibres of
each being made tense at the time of its dissection by rotating the
femur. The vessels, nerves, and muscles, which are to be defined
may be ascertained by referring to the enumeration below of the
parts beneath the gluteus. In removing the areolar tissue from
the ischial tuberosity and from the great trochanter, a bursa over
each prominence of bone may be observed.

Lastly, the fil^res of the muscle are to he detached at their origin ;
and the inner piece may be removed entirely by cutting through
the vessels and nerves that enter it. In doing this the sacral nerves
are to be dissected out of the fleshy fibres, and to be followed to the
surface of the great sacro-sciatic ligament, where they will l)e
afterwards seen.

Parts beneath the gluteus (fig. 48). At its origin the gluteus
maximus rests on the pelvis, and conceals part of the ilium, sacrum
and coccyx, also the ischial tuberosity with the origin of the ham-
string muscles (l) and the great sacro-sciatic ligament (k). At its
insertion it covers the upper end of the femur, with the great
trochanter, and the origin of the vastus extern us (i). Between
the muscle and the trochanter is a large, loose synovial
membrane ; between it and the vastus externus is another
synovial sac ; and occasionally there is a third over the ischial
tuberosity.

In the hollow between the pelvis and the femur the muscle
conceals, from above downwards, the undermentioned parts
(fig. 48) : — First, a portion of the gluteus medius (a) ; and below
it the pyriformis (b), with the superficial branch of the gluteal
vessels between the two. Coming from beneath the pyriformis are
the inferior gluteal nerve supplying the gluteus maximus, and the
large (^) and small sciatic nerves, with the sciatic vessels, which
descend to the thigh between the great trochanter and the ischial
tuberosity ; and internal to the sciatic are the pudic vessels and
nerve, and the nerve to the obturator internus muscle, which
are directed inwards through the small sacro-sciatic foramen.
Still lower down is the tendon of the obturator internus muscle (d)
with a fleshy fasciculus — the gemellus (c and e) — above and below
it. Next comes the quadratus femoris muscle (g) with the upper
part of the adductor magnus (h) ; at the upper border of the
quadratus, and deep to it, is the tendon of the obturator externus ;
and at the lower border, between it and the adductor, issues one of
the terminal branches of the internal circumflex artery with its
veins.

PARTS UNDER THE GLUTEUS MAXIMUS.

115

Dissection. Tracing back the oflfsets of the sacral nerves which Trace sacral
perforate the gluteus, and removing a fibrous stratum which covers "e'^'^*^-
them, the looped arrangement of the fii'st three nerves on the great

Superior gluteal nerve. Sui>erficial branch of gluteal artery.

Small sciatic nerve
Sciatic artery.
Pudic nerve
Pudic arterv,

Nerve to obtu
rator intenius,

Long pudendal
ner^•e.
Cutaneous vf
thigh of small
sciatic nerve.
Jluscular branch
of great sciatic
nerve.

Smail sciatic nerve.
Sciatic artery

Last dorsal
ne^^'e.

Anastomotic branch
of sciatic artery.

Internal circumflex
artery.

First perforating
artery.

Fig. 48. — Second View of tue Dissection op the Bitttock (Illustrations
OF Dissections).

Muscles :

A. Ghiteus medius.

B. Pyriformis.

c. Upper gemellus.

D. Obturator internus.

E. Lower gemellus.

F. Obturator externus.

G. Quadratus femoris.

H. Adductor magnus.

I. Vastus externus.

J. Gluteus njaximus, cut.

K. Great sacro- sciatic ligament.

L. Hamstring muscles.

Nei-ves :
6. Great sciatic.

Above the small sciatic are branches of the lower gluteal nerve, cut.

sacro-sciatic ligament will appear. Finally, the nerves may be
followed inwards beneath the multifidus spinas to the posterior
sacral foramina.

I 2

116

DISSECTION OF THE BUTTOCK.

The sacral
nerves are
united
beneath
gluteus :

cutaneous
offsets.

Gluteus
niedius

arises from
hip-bone,

and inserted
into tro-
chanter :

relations ;

use with

limb

hanging,

both limbs
tixed,

in standing
on one leg,

and walking.

Detach
gluteus
niedius to
see gluteal
vessels

and nerve.

Gluteal
artery is

divided into
two :

superficial

and deep
parts ;

Sacral nerves. The external x^ieces of the posterior primary
branches of the first three sacral nerves, after passing outwards
beneath the niultifidns spinae, are joined to one another by loops
on the surface of the great Scicro-sciatic ligament.

Two or three cutaneous offsets are derived from this inter-
coniniunication, and pierce the fibres of the gluteus maximus to be
distributed on its surface as already seen.

The GLUTEUS MEDius (fig. 48, a) is triangular in form, with its
base at the iliac crest, and apex at the femur. It arises from the
outer surface of the ilium between the crest and the superior curved
line above, and the middle curved line below (fig. 47) ; and many
superficial fibres come from the strong fascia covering the front
of the muscle. The fibres converge to a tendon, which is inserted
into an impression running downwards and forwards across the
outer surface of the great trochanter, extending from the tip
behind to the root in front (fig. 61, p. 158).

The superficial surface is concealed in part by the gluteus maxi-
mus ; and the deep is in contact with the gluteus minimus, and
the gluteal vessels and nerve. The anterior border lies over
the gluteus minimus, and is in contact with the tensor fasciae
femoris. The posterior is contiguous to the pyriformis, only the
superficial part of the gluteal vessels intervening. A small bursa
is interposed between the tendon of insertion and the trochanter.

Action. The whole muscle abducts the hanging femur ; and the
anterior fibres rotate the limb inwards.

Both limbs resting on the ground, the muscles assist in fixing the
pelvis. In standing on one leg this gluteus will aid in balancing
the pelvis on the top of the femur, and will draw the body over to
the same side.

In walking the fore part of the muscle acts in rotating the pelvis
over the fixed limb.

Dissection. The gluteus medius is now to be detached from
the pelvis, and partly separated from the gluteus minimus beneath,
so that the gluteal vessels and the superior gluteal nerve may come
into view. The two chief branches of the artery — one being near
the upper border of the gluteus minimus, and the other lower down
— are to be traced beneath the fleshy fibres as the reflection of the
gluteus is proceeded with ; and the main piece of the nerve is to
1)6 followed forwards to the tensor fascia femoris muscle. The
branches of the artery and nerve to the gluteus medius will be cut
in remo\dng that muscle.

The GLUTEAL ARTERY is the largest branch of the internal iliac,
and issues from the pelvis above the pyriformis muscle, where it
at once divides into superficial and deep parts : —

The superficial part (fig. 48) enters the under surface of the
gluteus maximus and ramifies in that muscle. Some terminal
twigs pass inwards over the sacrum, and others are given to
the integuments.

The deep part (fig. 50, a, p. 122) is the continuation of the artery,
and subdivides into two pieces which run between the two smaller

THE GLUTEAL VESSELS. 11^

glutei. One (superior ; b) courses along the upper l)order of the

gluteus minimus (supplying mostly the medius) to the front of the

iliac crest, where it anastomoses with the ascending branch of the the latter

external circumflex artery. The other portion (inferior ; c) is and^'iower'^

directed forwards over the middle of the smallest gluteal muscle, i>ranch.

with the nerve, towaixls the anterior lower iliac spine, where it

enters the tensor fasciae femoris, and communicates with the

external circumflex artery (p. 159) : many ofi"sets are furnished

to the gluteus minimus, and some pierce that muscle to supply the

hip-joint.

VeiJi. The companion vein with the artery enters the pelvis, Gluteal
and ends in the internal iliac vein, ^®"''

The SUPERIOR GLUTEAL NERVE (fig. 50, ^) is the highest branch Superior

of the sacral plexus, and arises from the lumbo-sacral cord and the yene
first sacral nerve (fig. 49, p. 120). It accompanies the gluteal
artery, and divides into two for the supply of the gluteus medius is muscular,
and minimus ; its lower branch terminates anteriorly in the
tensor fasciae femoris (b).

The GLUTEUS MINIMUS (fig. 50, c) is triangular in shape, and Gluteus
arises from the dorsum of the ilium between the middle and inferior '"•"i™"=* -
curved lines, extending l>ackwards as far as the middle of the
anterior margin of the great sciatic notch (fig. 47). Its tendon
is inserted into an impression along the fore part of the great attacli-
trochanter of the femur Cfig. 60, p. 157), where it is united'"^""*
inferiorly with the gluteus medius : some fibres are attached to
the capsule of the hip-joint.

One surface is in contact with the gluteus medius, and the gluteal relations;
vessels and nerve ; the other with the hip-bone, the hip-joint, and
the outer head of the rectus femoris muscle. The anterior border
lies by the side of the gluteus medius ; and the posterior is covered
by the pyriformis muscle. A bursa is placed l^etween the tendon
and the bone.

Action. This muscle agrees in its action with the gluteus use like
medius ; but as it reaches farther backwards, the hinder fibres ™^*"^-
may also have some influence in rotating the hanging femur
outwards.

Dissection. Cut through the smallest gluteal muscle near the Divide
ilium, and define the tendinous portion of the rectus femoris under- f™^^eus*
neath it, close above the hip-joint. Wliile detaching the gluteus °
from the parts underneath, the student will notice the connection
between its tendon and the capsule of the joint.

The deep vessels to the articulation may be observed and followed trace deep
as the muscle is removed. vessels.

The posterior or reflected head of the rectus femoris is a tendon as Posterior

wide as the finger, and about two inches long, which is fixed into ^^t*is^^'*®

the impre&sion above the margin of the acetabulum. In front it

joins the straight head of the muscle, which is attached to the

anterior inferior iliac spine ; and its lower border is connected with

the capsule of the hip-joint.

The PYRIFORMIS (fig. 48, b and fig. 50, f) arises in the pelvis Origin of

pyriformis ;

118

DISSECTION OF THE BUTTOCK.

insertion

relations in
foramen,

in buttock ;

use with
femur hang-
ing, and
raised ;

botli limbs
on ground,

only one.

Dissect out
the chief
vessels and
nerves,

and mus-
cular ]
branches.

The vessels
come from
the iliac.

Sciatic
artery :

course
and ending :

branches ;—
coccygeal ;

branch to
sciatic
nerve ;

from the front of the sacrum between and outside the second,
third, and fourth foramina, and leaves that cavity through the
great sacro-sciatic foramen to end in a rounded tendon, which is
inserted into the upper edge of the great trochanter of the femur
(fig. 60, p. 157).

The muscle occupies the greater part of the sacro-sciatic foramen,
and divides the vessels and nerves passing through that aperture
into two groups : — Above it are the gluteal vessels and the superior
gluteal nerve ; and helow it the sciatic and pudic vessels and nerves,
and some other branches of the sacral plexus. Its upper border is
contiguous to the gluteus medius ; and its lower, to the superior
gemellus. Like the other rot-ator muscles in this situation, it is
covered l)y the gluteus maximus, and by the gluteus medius at the
insertion ; it rests on the gluteus minimus, which separates it from
the hip-joint. Its tendon is united by fibrous tissue to that of the
obturator and gemelli.

Action. The pyriformis rotates out the femur when that bone is in
a line with the trunk ; but if the hip-joint is l)ent it abducts the liml).

Both limbs being fixed, the muscles l)alance the pelvis, and help
to make the trunk erect after stooping to the groimd. In standing
on one leg, besides assisting to support the trunk, the pyriformis
turns the face to the opposite side.

Dissection. The pyriformis may now be cut across and raised
towards the sacrum, to allow the dissector to follow upwards the
sciatic and pudic vessels, and to trace the accompanying nerves to
their origin from the sacral plexus.

A small nerve to the obturator intern vis (fig. 50, ^) and gemellus
superior is to be sought for in the fat at the lower border of the
plexus passing over the spine of the ischium on the outer side of the
internal pudic artery. A branch to the quadratus and inferior
gemellus (^') may be found l)y raising the trunk of the great sciatic
nerve ; but this will be followed to its termination after the muscles
it supplies have been seen.

Sciatic and Pudic Vessels. The arteries on the back of the
pelvis, below the pyriformis muscle, are branches of the internal
iliac, which will be described in dissection of the pelvis.

The SCIATIC ARTERY (fig. 48) supplies the buttock below the
gluteal. After escaping from the pelvis below the pyriformis,
it descends with the small sciatic nerve over the gemelli and
obturator internus muscles, as far as the lower border of the gluteus
maximus ; in its course the artery gives oft" many branches with the
superficial off'sets of its companion nerve ; and, much reduced in
size, it is continued with that nerve along the back of the thigh.
In this course it furnishes the following branches : —

a. The coccygeal branch arises close to the pelvis, perforates the
great sacro-sciatic ligament and the gluteus maximus, and ramifies
in this muscle, and on the back of the sacrum and coccyx.

6. The branch to the great sciatic nerve (comes nervi ischiadici) is
very slender, and entering the nerve near the pelvis, ramifies in it
along the thigh.

SCIATIC AND PDDIC VESSELS. 119

c. Muscular branches enter the gluteus maximus, the upper muscular ;
gemellus, and obturator internus ; and by means of a branch to

the quadratus, which passes with the nerve of the same name
beneath the gemelli and obturator internus, it gives offsets to the
hip-joint and the inferior gemellus.

d. Anastomotic branch (fig. 48). Varying in size, this arters' is anasto-
directed outwards along the lower border of the pyriformis to the ^^ ^^'
root of the great trochanter, where it anastomoses with the internal
circumflex and first perforating arteries.

The INTERNAL PUDic ARTERY (fig. 48) belongs to the perineum Pudic
and the genital organs : it is smaller than the sciatic, internal to ^^^^
which it lies. Only the small part of the vessel which winds over crosses the
the ischial spine is seen on the back of the pelvis, for it enters the ^^^^^]
perineal space through the small sacro-sciatic foramen, and is there
distributed.

It supplies a small branch over the back of the sacrum, which offseta.
anastomoses with the gluteal and sciatic arteries ; and a twig from
it accompanies the nerve to the obturator internus muscle.

The veins with the sciatic and pudic arteries receive tributaries Veins,
corresponding with the branches of those arteries at the back of the
pelvis, and open into the internal iliac vein.

Nerves. The nerves appearing at the back of the pelvis, below Nerves come
the pyriformis, are derived from the plexus {sacral plexus) formed p^'^^^'*
within the pelvis by anterior branches from the lower two lumbar and
the upper four sacral nerves; the largest are furnished to parts
beyond the gluteal region, but some are distributed to the muscles
at the back of the pelvis.

The inferior gluteal nerve is larger than the superior, and inferior
arises from the upper part of the sacral plexus (fig. 49, i g). The fiuteus
short trunk is directed backwards below the pyriformis, and divides ™aximus.
into numerous branches which radiate upwaixls and downwards,
and enter the gluteus maximus midway between its origin and
insertion.

The SMALL SCIATIC (fig. 48) is a cutaneous nerve of the back Small
of the thigh. It springs from the second and third sacral nerves cuSneous*
(fig. 49, s s), and takes the course of the sciatic artery as far as the nerve;
lower border of the great gluteus, where it gives many cutaneous
branches. Much diminished in size at that spot, the nerve is
continued along the iDack of the thigh beneath the fascia, and
ends below the knee in the integuments of the Irnck of the leg. ends in the
The branches distributed to, or near the buttock, are the ^®^ '
following : —

The ascending or gluteal cvlaneous branches (fig. 46) turn upwards ascending
round the border of the gluteus maximus, and are distributed to
the skin over the lower third of the muscle.

The descending cutaneous branches (fig. 46, 2) supply the integu- and
ments of the upper third of the thigh at the inner and posterior
a.spects. One of these branches (fig. 48), which is larger than the branches ;
others, is distributed to the genital organs, and is named inferior i„ferior
pudendal ; as it courses to the perineum, it turns below the pudendal

120

DISSECTION OF THE BUTTOCK.

Great sciatic
nerve :

outline of ;

ischial tuberosity, and perforates the fascia lata at the inner side
of the thigh to end in the scrotum.

The GREAT SCIATIC (fig. 48, 6) is the largest nerve in the body.
It is the source of all the muscular, and most of the cutaneous

Fig. 49. — Diagram of the Sacral Plexus from Behind.

LSC. Lumbo-sacral cord formed
by the fifth lumbar nerve and a
small branch from the fourth.

SI to S 5. First to fifth sacral
nerves.

g s. Great sciatic nerve.

s s. Small sciatic.

sg. Superior gluteal.

i g. Inferior gluteal.

p. Pudic.

p c. Perforating cutaneous.

py. Branch to pyriformis.

0 i. Nerve to obturator intern us.

q. Nerve to quadratus femoris.

The remaining references are explained in the dissection of the plexus in
the pelvis.

branches to the limb beyond the knee, as well as of the muscular
branches at the back of the thigh.

At its origin it ap]3ears to be a prolongation of the sacral plexus
(fig. 4:9, g s). It is directed through the buttock to the back of
the thigh, and rests, in succession, on the superior gemellus, the
tendon of the obturator interims, the inferior gemellus and the
iio braiichin quadratus femoris muscles below the pyriformis. Commonly it

this region. ^ ^ - . . i i i i ■ • • •

does not supply any branch to the buttock, but it may give origin

course m
the buttock ;

BRANCHES OF THE SACRAL PLEXUS. 121

to one or two filaments to the hip-joint. Frequently the nerve is
divided into two large trunks at its origin, and one of them (the
external popliteal) pierces the fibres of the pyriformis muscle.

The PUDic NERVE (fig. 48) winds over the small sacro-sciatic Pudic nerve,
ligament on the inner side of its companion artery, and is dis-
tributed with this vessel to the perineum and the genital organs.
Xo branch is supplied to the buttock.

Small MUSCULAR branches of the sacral plexas are furnished to Muscular
the external rotators except the obturator externus. ™"^ ^^ *

The branch to the pynformis, from the second sacral nerve, is to
seen in the dissection of the sacral plexus in the pehds. P^" ^'™*'' '

The nerve to the obturator internus (fig. 50,^) arises from the to obturator
upper part of the plexus, and is directed to its muscle through "i^^rior^"
the small sacro-sciatic foramen external to the pudic vessels : it gemellus ;
gives off a small twig to the superior gemellus (').

The nerve to the quadratus fenmris (fig. 50,^) is a slender branch, toquad-
which passes with a companion artery beneath the gemelli and the inferior ^
obturator to the anterior surface of its muscle. This branch will gemellus.
Ije seen more fully in ^ subsequent dissection, when offsets from it
to the inferior gemellus and the hip-joint may be traced.

Dissection. To see the remaining external rotator muscles, hook Clean rota-

; le the great sciatic nerve, and take away the branches of the
sciatic artery if it is necessary. In cleaning these muscles the
limb should be rotated inwards. The gemelli are to be separated
from the tendon of the obturator internus.

The superior gemellus (fig. 48, c) is the higher of the two Superior
muscular slips along the sides of the tendon of the obturator g®™^'^"'''
muscle. Internally it arises from the outer and lower part of the
ischial spine (fig. 47, p. 113), and externally it is inserted with the
obturator into the great trochanter. Occasionally the muscle is
absent.

The INFERIOR gemellus (fig. 48, e) is larger than its fellow. Inferior
Its origin is connected with the upper part of the ischial tuberosity, ^®™^ "^ '
along the lower edge of the groove for the obturator internus muscle
(fig. 47) ; and its insertion is in common with the obturator tendon.
This muscle is placed between the obturator internus and quad- both in-
i-atus, but near the femur the tendon of the obturator extenius ob^rator*^^^
comes into contact with its upper border.

Action. These small fieshy slips are but accessory pieces of use to help
origin to the internal obturatoi', with which they combine in use. obturator.

The OBTURATOR INTERNUS (fig. 48, d) adses from the hip-bone obtm-ator
inside the pehis, and passes to the exterior through the small i"^™"^
sacro-sciatic foramen. The tendon of the muscle is directed outside
outwards over the hip-joint, and is inserted with the gemelli, in ^ ^^^'
front of the pyriformis, into the inner side of the great trochanter, '

at the upper and fore part (fig. 60, p. 157).

Outside the pelvis the obturator is mostly tendinous, and is relations;
embraced by the gemelli muscles, which near the pelvis meet
beneath the tendon ; but near the trochanter they cover it.
Crossing the muscle are the large and small sciatic nerves and the

122

DISSECTION OF THE BUTTOCK.

tendon is sciatic vessels ; and covering the whole is the gluteus niaximus.
the'edge^of ^^^ cutting through the tendon and raising the inner end, it will

the pelvis ;

Fia. 50. — Third View of the Dissection op the Buttock
(Illustrations ov Dissections).

Muscles :
(xluteus niaximus, cut.
Tensor fasciae latfe.
Gluteus minimus.
Gluteus medius, cut.
Pyriformis.
Gemellus superior
Obturator internus, cut.
Gemellus inferior.

c.
j>.

F.
G.
H.
I.

K. Quadratus femoris, cut.

L. Obturator externus.

N. Adductor raagnus.

o. Hamstrings.

P. Great sacro-sciatic ligament.

Arte7'ies :

a. Gluteal.

b. Its upper, and c, its lower j)iece.

d. Sciatic.

e. Pudic.

/. Internal circumflex.
(/. Its ascending, and h, its trans-
verse offset.

i. First perforating.
k. External circumflex.

Nerves :

1. Superior gluteal.

2. Sacral.

3. Small sciatic, cut.

4. Pudic.

5. Nerve to obturator internus.

6. Nerve to quadratus and inferior
gemellus.

7. Branch to upper gemellus.

8. Great sciatic.

INTERNAL CIRCUMFLEX ARTERY. 123

3e found divided into four or five pieces as it turns over the ischium
fig. 50, h) ; at this spot the l)one is covered with cartilage, which
brms ridges corresponding to the inten-als between the tendinous
dips, and the surfaces are lubricated by a syno\'ial sac. There is
5onietiines another bursa between the tendon and the hip-joint.

Action. The action of this muscle is in all respects the same as use like
that of the pyriformis (p. 118), although, as it acts at a greater P>'"^'^'"™*^-
tnechanical advantage, it is a much more powerful external rotator.

The QUADRATUS FEMORis (fig. 48, g) is situate between the Quadratus
[inferior gemellus and the adductor magims. Internally it arises ^™°"^-
[from the out^r border of the ischial tuberosity for two inches, by the °"^^ »
• of the semimembranosus and adductor magnus (fig. 47, p. 1 13) ;
rnally it is inserted into an eminence on the posterior inter- insertion ;
tiuchanteric ridge of the femur (tubercle of the quadratus), and
along a line on tlie upper end of that bone for a1x)ut one inch and a
half, above the attachment of the great adductor (fig. 61, p. 158).

By one surface it is in contact with the sciatic vessels and nerves, parts over
and the gluteus maximus. Bv the other it rests on the obturator and beneath

. . ' it

externus, the internal circimiflex vessels, and its small nerve and '
vessels. Between its lower border and the adductor magnus the and at lower
transverse branch of the internal circmuflex artery issues. Between ^^ '
it and the small trochanter is a bursa, which is also common to the
upper part of the adductor magnus.

Action. The quadratus difi'ers from the foregoing muscles of the 'ise.
same group in 1>eing able to rotate the femur outwards when the
hip-joint is bent, as well as in the extended position ; and it will
assist slightly in adducting the limb.

Dissection (fig. 50). The quadratus and the gemelli muscles Divide
may now be cut across, in order that their small nerve and art^r}*, quadratus
the ending of the internal circumflex artery, and the obturator
externus may be dissected out.

The INTERNAL CIRCUMFLEX ARTERY (fig. 50) from the profunda internal
femoris artery (p. 166) divides finally into two pieces. One ^^l^JJ^^^^
{ascending) runs beneath the quadi-atus (in this position of the
body) to the pit of the trochanter, where it anastomoses with the
gluteal and sciatic arteries, and supplies the lx)ne. The other ends in two
{transverse) passes between the quadratus and adductor magnus b™"<=^^-
to the hamstring muscles, and communicates with the perforating
arteries.

The OBTURATOR EXTERNUS (fig. 50, l) will be dissected at its Obturator
origin in the front of the tbigh. The part of the muscle now laid ^'^^^^
bare winds below the hip-joint, and ascends to be inserted into the js inserted
pit at the root of the trochanter. trocii^nter ;

On the back of the pelvis the obturator externus is covered by the relations ;
quadratus, except near the femur where it is exposed l^etween that
muscle and the inferior gemellus. Its deep surface is in contact
with the capsule of the hip-joint and the neck of the femur.

Action. Like the quadratus femoris, it rotates the femur out- use.
wards in all positions of the limb : it is also to a slight extent an
adductor and flexor of the hip-joint.

124 .

Sacro-sciatic
ligaments :

large,

and small

fOlTll two

foramina ;

small, with
contents ;

large, and
parts pass-
ing tlirongh
it.

DISSECTION OF THE POPLITEAL SPACE.

The SACRO-SCIATIC LIGAMENTS pass froiii the sacrum and coccy?
to the ischium : they are two in numl)er, and are named great anc
small.

The great or posterior ligament (fig. 50, p) is attached above tc
the posterior inferior iliac spine, and to the side of the sacrum and
coccyx ; and lielow, to the inner margin of the ischial tuberosity
sending forwards a prolongation along the ramus of the bone : sorat
of the superficial fibres are continued over the tuberosity into the
long head of the biceps.

It is wide next the sacrum, and becomes narrower below ; but it
is somewhat expanded again at the tuberosity. On the cutaneou
surface are the branches of the sacral nerves ; and the gluteus maxi-
mus conceals and takes origin from it. Branches of the sciatic
artery and a cutaneous nerve from the sacral plexus perforate it.

The small or anterior ligament passes from the sacrum and coccyx
to the ischial spine, but this band will be more fully seen in the
dissection of the pelvis.

These ligaments convert the deep sacro-sciatic notch of the dried
pelvis into two foramina. Between their insertion into the spine
and tuberosity of the hip-bone is the small sacro-sciatic foramen,
which contains the internal obturator muscle with its nerve and
vessels, and the pudic vessels and nerve. And above the smaller
ligament is the large sacro-sciatic foramen, which gives passage to
the pyriformis muscle, with the gluteal vessels and the superior
gluteal nerve above it, and the sciatic and pudic vessels and nerves,
the inferior gluteal nerve, and the nerves to the obturator internus
and quadratus femoris below it.

Section II.

THE POPLITEAL SPACE AND THE BACK OF THE THIGH.

Directions.

Position

Take the
skin from
over the
ham.

Seek the

cutaneous

nerves.

Directions. The ham or popliteal space should be taken after the
buttock, in order that it may be seen in a less disturbed state than
if it were dissected after the examination of the muscles at the back
of the thigh. When this space has been learnt, the student will
return to the dissection of the thigh.

Position. The limb should be raised on blocks into the hori-
zontal position.

Dissection (fig. 51, p. 126). To remove the skin from the
popliteal region, let a longitudinal incision be made behind the knee
from a distance of six inches above to four inches below the joint.
At each extremity of this cut make a transverse incision, and raise
the skin in two fiaps, the one being turned outwards and the other
inwards.

In the fat are some small cutaneous nerves, viz., one or two twigs
in the middle line of the limb from the small sciatic nerve beneath

ANATOMY OF THE POPLITEAL SPACE. 125

the fa.scia ; and some offsets of the internal cutaneous nerve towards
the inner side. After the subcutaneous fat is removed, the special
fascia of the limb will be brought into view.

Fascia lata. Where this fascia covers the popliteal space it is FasRiaof
Jtjstrengthened by transverse fibres, particularly on the outer side ; ov|r"he

and it is connected laterally with the tendons bounding that ham.
Jt interval. The short saphenous vein perforates it opposite the knee,
i or a little lower down.

Dissection (fig. 51, p. 126 ; also fig. 53, p. 131). The fascia Remov(
over the ham is now to be removed without injuring the small
sciatic nerve and accompanying artery, and the short saphenous
vein, which are close beneath it. A large quantity of fat may be and take the
next taken out of the space, but without injury to the several small ham.
vessels and nerves in it.

In cleaning the space the student will come upon the large inter- Seek the
nal popliteal nerve in the middle, and the external popliteal on the the^lpa^^.
outer side. Both nerves give branches ; and the numerous offsets
of the inner will be recognised more certainly by tracing them from
above downwards along tlie trunk of the nerve, than by proceeding
in the opposite direction : in fat bodies the two small nerves from the
inner popliteal trunk to the knee-joint are difficult to find. Under
cover of the outer boundary, and deep in the space, is an articular
nerve from the external popliteal.

In the bottom of the space are the popliteal vessels, the vein Clean the
being more superficial than the artery. The student is to seek an ^'®^-^®^^ •
articular branch (superior) on each side, close above the condyle of
the femur, and to clean numerous other branches of the vessels to
the muscles around, especially to those of the calf. On the upper iind obtu-
I»art of the artery, the branch of nerve from the obturator to the ^^^ nerve,
knee-joint is to be found ; and on the sides of the artery are three and glands,
or four lymphatic glands in the fat.

The POPLITEAL SPACE, or ham (fig. 51) is the hollow behind The ham :
the knee : it allows of the free flexion of the joint, and contains the
large vessels of the limb. When dissected, this interval has the situation
form of a lozenge, and extends upwards along one-third of the
femur, and downwards along one-sixth of the tibia ; but in the
natural condition the muscles on the sides are approximated by
the fascia of the limb, and the space is limited to the region
immediately above the joint.

This hollow is situate between the muscles on the l)ack of the boundaries,
limb ; and the lateral boundaries are therefore formed by the muscles
of the thigh (hamstrings), and leg. Thus, on the outer side, is the outer
biceps muscle (^) as far as the joint, and the plantaris and the
external head of the gastrocnemius (^) beyond that spot. On the and inner :
inner side, as low as the articulation, are the semimembranosus (^)
and semitendinosus (^) muscles with the gracilis and sartorius between
them and the femur ; and below the joint is the inner head of the
gastrocnemius (^). The upper point of the ham is formed by the limit above
apposition of the inner and outer hamstrings ; and at the lower *"^ ^^^'"'^ '
point the heads of the gastrocnemius touch each other.

126

DISSECTION OF THE POPLITEAL SPACE.

superticial
and deep
boundaries

greatest
width and
depth ;

contents.

Popltieal
artery :

extent

only a small
part in
space

Stretched over tlie cavity are the fascia lata and the integument.^
In the deep boundary, or the floor, are the following structures :—
the surface on the back of the femur included between the suj^rn
condylar (popliteal surface), the posterior ligament of the knee

joint, and part of the popliteu;
muscle with the upper end of th«
tibia (fig. 52, p. 128).

The popliteal space is widest am
deepest immediately above tht
femoral condyles. (Above anr
below it communicates, beneatl
the muscles, with the back of th<
thigh and leg.)

In the hollow are containec
the popliteal vessels with theii
l)ranches, and the ending of the
external saphenous vein ; the pop
liteal trunks of the great sciatic
nerve, and some of their branches
together wdth lymphatic glands,
and a large quantity of fat. The
small sciatic nerve and its vesseh
are placed superficially in the
ham ; and a branch of the obtu-
rator nerve lies on the artery in
the bottom of the space.

The POPLITEAL ARTERY (fig. 51»

and fig. 5 2) is the continuation of the
superficial femoral,and reaches from
the opening in the adductor mag-
nus to the lower border of the pop-
liteus muscle, where it terminates
by bifurcating into the anterioi
and posterior tibial arteries. A
portion of the artery lies in the
popliteal space, and is not covered
by muscle ; Ijut iDoth above and
below, it is concealed by the

The part in
the ham :

course and
relations ;

Fig. 51. — View of the Popliteal
Space (Quain's Arteries).

1. Popliteal vessels.

2. Internal popliteal nerve.

3. External popliteal nerve.

4. Semimembranosus muscle.

5. Semitendinosus muscle.

6. Biceps muscle.

7. 8. Inner and outer heads of the
gastrocnemius muscle. The super-
ficial vein on the gastrocnemius is
the short saphenous, which enters
the popliteal.

muscles bounding the hollow. The
description of the artery may be
conveniently divided into two
parts — one reaching to the lower
limit of the ham, and the other
being beneath the gastrocnemius.
As far as the ham the vessel is
inclined obliquely from the inner side of the limb to the interval
between the condyles of the femur, and is then directed along the
middle of the space over the knee-joint. The artery is overlain
by the belly of the semimembranosus muscle to within an inch
of the internal condyle ; but thence onwards it is situate between

POPLITEAL ARTERY AND BRANCHES. 127

the heads of the gastrocnemius, and is covered only by the fascia lata
and the integuments. Beneath it is the femur, with the posterior
ligament of the knee-joint.

In contact with the vessel, and somewhat on the outer side at position of
first, lies the popliteal vein, so that on looking into the space, the ^^^'°'
arterial trunk is almost covered ; but in the interval between the
heads of the gastrocnemius, the vein and its branches altogether
conceal the artery. In the lower part of the ham the short saphen-
ous vein (fig. 53, 1, p. 131) and the muscular branches of the artery
are also superficial to the popliteal trunk.

More superficial than the large vessels, and slightly external to and of the
them in position, is placed the internal popliteal nerve, which, with '^^^^^^•
its branches, lies over the artery, like the vein, between the heads
of the gastrocnemius. In the bottom of the hollow the small
obturator nerve runs on the artery to the joint.

Dissection. To see the deep part of the artery, the inner head Cut inner
of the gastrocnemius should be cut through and raised. On remov- gastrocne-^
ing the areolar tissue the vessels and nerves will appear. The ™i^^^-
lower articular branches of the vessels and nerve are now brought
into view ; — the inner artery is below the head of the tibia, and
the outer, higher up, between the femur and the fibula, each mth
a vein ; and a companion nerve.

Beyond the ham. While the artery is beneath tJie gastrocnemius Art<ry be-
sinks deeply into the limb ; here it is crossed by a small muscle — ^°" ^^ '
tlie plantaris (c), and the ending is concealed by the soleus (b).
It rests on the popliteus muscle.

Both the companion vein and the internal popliteal nerve change position of
their position to the artery, and gradually cross over it, so as to ne"ve.°
lie on its inner side at the lower border of the popliteus.

Sometimes the artery bifurcates as high as the back of the knee-joint ; and High
then the anterior tibial artery may lie beneath the popliteus muscle. division.

Branches (figs. 52 and 53) are fui*nished by the artery to the Branches of
surrounding muscles, to the integuments, and to the articulation ; — artery,
those that belong to the joint are five in number, and are called
articular, viz., two superior, inner and outer ; two inferior, also
inner and outer ; and a central or azygos branch.

1. The muscular branches are upper and lower. The upper set. Muscular
three or four in number, arise above the knee, and end in the semi- ^^^ ^^'
membranosus and biceps muscles, communicating with the per-
forating and muscular branches of the profunda. The lower set
(sural) are furnished to the muscles of the calf, viz., gastrocnemius,
soleus, and plantaris.

2. The cutaneous or superficial sural branches descend to the skin and cuta-
of the calf of the leg : they are usually three in number, one in the
middle line, and one over each head of the gastrocnemius.

3. The superior articular arteries arise from the popliteal trunk. Articular
one from the inner and one from the outer side, above the condyles are fl?e?
of the femur ; they are directed almost transversely beneath the ^^^^
hamstring muscles, and tiun round the bone to the front of the joint, superior:

128 -

DISSECTION OF THE POPLITEAL SPACE.

external :

internal.

The external branch perforates the intermuscular septum, and
divides in the substance of the crureus. Some of the branches
end in that muscle, and anastomose with the external circumflex
(of the profunda) ; others descend to the joint and anastomose with
the lower external articular artery ; and one offset forms an arch
across the front with the anastomotic artery.

The internal artery^ oftentimes very small, winds beneath the

Popliteal artery

Adductor iiiagnus.
Upper muscular.

Upper muscular.

Tendon of adductor
magnus.

Upper internal articular.

Azygos.
Semimembranosus .
Gastrocnemius (inner
head).

Lower muscular.
Expansion to posterior
ligament of joint.

Expansion over popliteus.

Lower internal articular.
Internal lateral ligament.

Long head
Short head

\ Bleep:

Upper external articular

Lower muscular.
Gastrocnemius (outer

head).
Tendon of biceps.

Plantaris.

External lateral ligament.
Lower external articular.
Expansion over tendon
of popliteus.

Popliteus.
Anterior tibial.

Posterior tibial.

Fig. 52. — Popliteal Artery and Branches.

Two

inferior ;

external

tendon of the adductor magnus, and terminates in the vastus in-
ternus ; it supplies this and the knee-joint, and communicates with
the deep part of the anastomotic artery.

4. The inferior articular arteries lie beneath the gastrocnemius,
but are not on the same level on opposite sides of the limb ; for
the inner one descends below the internal tuberosity of the tibia,
while the outer one is placed above the head of the fibula. Each
lies beneath the lateral ligament of its own side.

The external branch supplies the outer side of the knee-joint,

POPLITEAL NERVES AND BRANCHES. 129

anastomosing with the other vessels on the articulation, and with
the recurrent branch of the anterior tibial artery ; it sends an offset
beneath the ligament of the patella to join a twig from one of the
internal branches.

The internal artery ramifies over the front of the internal internal,
tuberosity of the tibia, and anastomoses with the upper internal
and loMer external articular branches, and with the superficial
branch of the anastomotic artery.

5. The azygos branch enters the joint through the posterior liga- And one
ment, and is distributed to the ligamentous structures, the fat, and arte^.
the synovial membrane of the interior.

The POPLITEAL VEIN (fig. 53, h) originates in the union of the Popliteal
anterior and posterior tibial venee comites, and has the same extent ^^'"*
and relations as the artery it accompanies. At the lower border of position to
the popliteus muscle the vein is internal to the arterial trunk ; ^ ® artery ,
between the heads of the gastrocnemius, it is superficial to that
vessel ; and thence to the opening in the adductor magnus it lies to
the outer side of, and close to, the artery. It is joined by branches branches,
corresponding with those of the artery, as well as by the short
Iienous vein.

The Popliteal Nerves (fig. 51) p. 126) are the two large Popliteal
trunks derived from the division of the great sciatic in the thigh two,
i'p. 133), and are named internal and external. Each furnishes inner and
• utaneous and articular offsets, but only the inner one supplies °"^''-
branches to muscles.

The INTERNAL popliteal nerve (2) is larger than the external, internal
and occupies the middle of the ham : its relations are similar to Sene:*
those of the artery, that is to say, it is partly superficial, and
partly covered l)y the gastrocnemius. The nerve is continued to
the back of the leg, where it is called posterior tibial ; the name
popliteal is retained only to the lower border of the popliteus
muscle. Its position to the vessels has been already noticed, branches
The branches arising from it are the following : —

a. Two small articular twigs (fig. 53, ^) are furnished to the knee- two
joint with the vessels. One accompanies the lower internal ^^ '^" * '
articular artery to the front of the articulation, and is the larger ;

the other takes the same course as the azygos artery, and enters the
back of the joint ^vith it.

b. Muscidar branches arise from the nerves between the heads of four

the gastrocnemius. One is furnished to each head of the gastro- "^^^scular ;
cnemius, and the outer of these usually supplies the plantaris.
Another descends beneath the gastrocnemius, and enters the pos-
terior surface of the soleus. And a fourth penetrates the popliteus
at the anterior aspect, after turning round the lower border.

c. The tibial communicating branch (fig. 71,^, p. 188) is a and one
cutaneous offset to the leg and foot. It lies beneath the fascia, and the tibial '
between the heads of the gastrocnemius, as far as the middle of the ^^'^^"
leg, where it becomes superficial, and unites with the peroneal com-
municating branch of the external popliteal, to form the short
saphenous nerve (p. 187).

D.A. K

130

DISSECTION OF THE THIGH.

External
popliteal
nerve :

course
and ending

branches,
articular,

peroneal
communi-
cating,

and lateral
cutaneous
of leg.

Articular
nerve of the
obturator.

Lymphatic
glands
around the
artery.

The EXTERNAL POPLITEAL NERVE (peroneal ; fig. 51,'-) lies along
the outer boundary of the ham, and is at first concealed by the
edge of the biceps muscle ; becoming superficial, it is continued
over the outer head of the gastrocnemius, following the hinder
border of the biceps tendon, until it is below the head of the fibula.
There it enters the fibres of the peroneus longus, and divides
beneath that muscle into two — musculo-cutaneous and anterior
tibial. Its branches are articular and cutaneous : —

a. The articular nerve, arising high in the space, runs with the
upper external articular artery to the outer side of the knee, and
sends a twig along the lower articular artery : both enter the
joint.

h. The peroneal communicating branch (fig. 71, "*, p. 188) soon
pierces the fascia, and descends over the outer head of the gastro-
cnemius to join the tibial communicating from the internal popliteal
in the short saphenous nerve.

c. One or two lateral cutaneous branches aiise either in common
with the preceding or se^Darately, and supply the skin of the outer
side of the leg, reaching nearly to the external malleolus.

The ARTICULAR BRANCH OF THE OBTURATOR NERVE (fig. 53, ')

perforates the adductor magnus (p. 164), and is conducted by the
popliteal artery to the back of the knee. After supplying filaments
to the vessels, the nerve enters the articulation through the posterior
ligament.

The POPLITEAL LYMPHATIC GLANDS are situate round the large
arterial trunk. Two or three are ranged on the sides ; while one
is superficial to, and another beneath the vessel : they are joined by
the deep lymphatic vessels, and by the superficial set with the
external saphenous vein.

Dissect the
back of the
thigh.

Seek out
cutaneous
nerves ;

Clean

muscles and
nerves.

Three
muscles on
back of
thigh:

situation.

THE BACK OF THE THIGH.

Dissection (fig. 53). After the popliteal space, the student
may proceed with the dissection of the back of the thigh. The
piece of skin between the buttock and the ham should be divided
in the middle line and reflected to the sides. In the fat on the
outer side of the limb fine oflFsets of the external cutaneous nerve
of the thigh may be found ; and along the middle some filaments
from the small sciatic nerve pierce the fascia.

Remove the deep fascia of the liml), taking care of the small
sciatic nerve and its artery. Lastly, clean the hamstring muscles ;
trace the arteries from the front of the thigh, which perforate the
muscle to get to the back ; and clean the branches of the great
sciatic nerve to the muscles.

Muscles. The muscles behind the femur are flexors of the
knee-joint. They reach from the jDelvis to the bones of the leg,
and are named hamstrings from the cord-like appearance on the
sides of the ham. They are three in number, viz., biceps, semi-
tendinosus, and semimembranosus. The first of these lies on the
outer, and the other two on the inner side of the popliteal space.

THE HAMSTRING MUSCLES.

131

The BICEPS (tig. 53, d)
has two lieads of origin,
long and short, which are
attached to the pelvis and
the femur. The long head
arises from the lower and
inner impression on the
ischial tuberosity, in com-
mon Avith the semitendi-
nosus muscle (fig. 47,
p. 113). The short head
arises from the femur
l)elow the gluteus maxi-
mus ; from the outer lip of
the linea aspera, from the
upper three-fourths of the
line leading to the outer
condyle, as well as from
the external intermuscular
- ptum (fig. 61, p. 158).
The fibres end IkjIow in a
i'udon, which is inserted
into the head of the fibula
embracing the external
lateral ligament (fig. 68,
p. 179); and a slight
piece is prolonged to the
head of the til)ia.

The muscle is super-
ficial except at its origin,
where it is covered by the
gluteus maximus ; it rests
on the upper end of the
semimembranosus, on the

Biceps

a long

and a short
head ;

■J is inserted
into the

g" fibula and
tibia :

relations :

Fig. 53. — Dissection of the Back op the Thigh (Illustrations

OP Dissections).

Muscles :

A. Gluteus maximus,
cut below, and partly
raised.

B, Quadratusfemoris.
c. Adductor niagnus.

D. Biceps.

E. Semitendinosus.

p. Semimembranosus.

G. Outer, and h, inner
head of the gastro-
cnemius.

Vessels :

a. Sciatic artery.

b. Ending of internal

cii-cumflex to hamstrings.

c. First, d, second,
and e, third perforating
arteries.

/. Muscular branch of
profunda.

g. Popliteal artery.

h. Popliteal vein.

i. Short saphenous
vein.

k. Upper external,
and I, upper internal
articular artery.

Nerves :
1. Small sciatic, cut.

2. Large sciatic.

3. Branch to ham-
strings from 1 arg e
sciatic.

4. External jwpliteal.

5. Communicating
peroneal.

7. Articular branch
of obturator to knee.

8. Internal popliteal.

9. Articular branch
to knee of the internal
popliteal.

10. Tibial communi-
cating.

K 2

132

DISSECTIOK OF THE THIGH.

use on knee

and hip-
joints,

on pelvis,

and femur.

Semitendi-
nosus is
attached to
pelvis and
tibia ;

parts in
contact
with it ;

use on
knee

and hip-
joints,

on the
pelvis.

Semimem-
branosus
reaches from
pelvis to
tibia ;

parts around
it;

great sciatic nerve and on tlie adductor magnus muscle. On the
inner side are the semitendinosus and semimembranosus as far as
the ham. Its tendon gives an offset to the deep fascia of the
limb.

Action. It can Ijend the knee if the leg-bones are not fixed, and
afterwards rotate out the tibia ; and the long head will extend the
bent hip-joint when the knee is straight.

The leg being supported on the ground, the long head will assist
in balancing and erecting the pelvis ; and the short head will draw
down the femur so as to l^end the knee in stooping.

The SEMITENDINOSUS (fig. 53, e) is a slender muscle and received
its name from its appearance. It arises from the tuberosity of the
ischium with the long head of the biceps, and by fleshy fibres from
the tendon of that muscle. Inferiorly it is inserted into the inner
surface of the tibia, close below the gracilis, and for a similar extent
(fig. 68, p. 179).

This muscle, like the biceps, is partly covered by the gluteutJ
maximus. About its middle an oblique tendinous intersection may
be observed. It rests on the semimembranosus, and on the internal
lateral ligament of the knee-joint. The outer border is in contact
with the biceps as far as the lower third of the thigh. As the
tendon turns forwards to its insertion, an expansion is continued
from it to the fascia of the leg ; and it is attached, with the gi'acilis,
on a level with the tubercle of the tibia, the two being separated
from the internal lateral ligament l^y a bursa.

Action. If the leg is movable, the muscle bends the knee and
rotates inwards the tibia. Supposing the knee-joint straight but
the hip-joint bent, the femur can be depressed, and the hip extended
by this and the other hamstrings.

Should the limbs be fixed on the ground, the muscle will assist
in balancing the pelvis, or in erecting the trunk from a stooping
posture.

The SEMIMEMBRANOSUS MUSCLE (fig. 53, f) is teudiuous at both
ends, and receives its name from the meml^raniform appearance of
the upper tendon. The muscle arises from the upper and outer
impression on the ischial tuberosity (fig. 47, p. 113); and it is
inserted l^elow into the inner and hinder part of the head of the tibia
(fig. 73, p. 191), and from this position one fibrous expansion is sent
outwards across the back of the knee-joint to the outer side of the
external condyle of the femur, forming thereby the strongest part of
the posterior ligament, and another proceeds downwards as a fascial
investment over the back of the popliteus muscle (fig. 52, p. 128).

The muscle is thick and fleshy below, where it bounds the
popliteal space. On it lies the semitendinosus, which is lodged,
together with the long head of the biceps, in a hollow in the upper
tendon ; and beneath it is the adductor magnus. Along the outer
border is first the great sciatic, and then the internal popliteal
nerve. Between its tendon and the inner head of the gastrocnemius
is a large bursa. The insertion of the muscle above described will
be dissected with the knee-joint (p. 214).

BRANCHES OF PROFUNDA ARTERY. 133

Action. This hamstring m united with the preceding in its action, use on knee
for it bends the knee and rotates in the tibia ; and with the knee
straight it will limit flexion of the hip, or extend this joint after and hip-
the femur has been carried forwards. The extension across the ^^"^^'^'
back of the joint serves to keep the posterior ligament clear of the
articulation in flexion of the leg.

When the foot rests on the ground, the semimembranosiLS acts on pelvis,
on the pelvis like the other hamstring muscles.

The GREAT SCIATIC NERVE (fig. 53, 2) Hes on the adductor magnus Great sciatic
muscle l)elow the buttock, and divides into the two popliteal nerA'es thJ\hiaii
al)out the middle of the thigh, though its point of bifurcation may
be carried upwards as far as the peh'is. In this extent the nerve
lies along the outer border of the semimembranosus, and is crossed
l»y the long head of the biceps.

BroMches. Near the buttock it supplies large branches to the supplies
flexor muscles, and a small one to the adductor magnus. ™'^*' ^*'

Small sciatic nerve -(fig. 53, i). Between the gluteus"maximus smaii

and the ham this small nerve is close beneath the fascia ; but it fp'**'/'.*?

. , , the thigh :

l>ecomes cutaneous below the knee, and accompanies the external

saphenous vein for a short distance.

Small cutaneous filaments pierce the fascia ; and the largest of cutaneous
these arises near the popliteal space. ° ^^ *

Dissection. To see the posterior surface of the adductor magnus, Detach the
and the l:>ranches of the perforating and anastomotic arteries at the
l»ack of the thigh, the han^string muscles must be detached from
the hip-bone and thrown down ; and the l)ranches of arteries and
nerves they receive are to be dissected out with care. All the parts
are to be cleaned.

Adductor magnus muscle (fig. 53, c). At its posterior aspect fy^^J'g^Jf
the large adductor is altogether fleshy, even at the opening in the adductor
lower third of the thigh, where the superficial femoral passes through '"^s^*^^-
it to become the popliteal ; and the upper fibres which come from
the pubic arch appear to form a part almost distinct from those
connected with the tuberosity of the ischium. In contact with
this surface are the hamstring muscles and the great sciatic nerve.
(The muscle will be described later in tha dissection of the thigh
from the front, p. 167.)

End of the perforating arteries (fig. 53, c, d, e). These Perforating
In-anches of the profunda femoris appear through the adductor a^t^^ies :
magnus close to the femur, and are directed outwards through the course
short head of the biceps and the outer intermuscular septum to the
vastus externus and crureus muscles ; but as the first branch is placed
higher than the attachment of the biceps, it pierces the gluteus
maximus in its course. In the extensor muscles they anastomose and ending;
together, and with the transverse and descending branches of the
external circumflex artery.

Muscular branches are furnished liy the perforating arteries to offsets to
the heads of the biceps ; and a cutaneous offset is given by each to theTkin?
the integuments of the outer side of the thigh, along the line of
the outer intermuscular septum.

134 DISSECTION OF THE THIGH.

Muscular MuSCULAR BRANCHES OF THE PROFUNDA (fig. 53, /), pierce

branches : ^^le adductor magnus internal to the preceding, and at some distance
number and from the femur (p. 166). Three or four in number, the highest

course \i. / / o

appears about fixe inches from the pelvis, and the rest in a line at
intervals of about two inches from one another : they are distributed
to the hamstring muscles, especially the semimembranosus, and
communicate below with oflPsets of the popliteal trunk.

Dissection. The muscles are to be taken away from the back
of the hip-joint and the areolar tissue removed from the back
of the capsule, so as to prepare for the dissection of the joint at a
later st-age,

CHAPTER IV.
DISSECTION OF THE LOWER LIMB.

Section I.

THE FRONT OF THE THIGH.

Position. During the dissection of the front of the thigh the body Position of
lies on the back, with the buttocks resting on the edge of the table, ^^^ ^^^^^'
and with a block of suitable size beneath the loins. The lower limb
should be stretched out on the table, slightly flexed at the knee
and rotated outwards to make eWdent a hollow at the top of the
thigh.

Surface-marking. Before any of the integument is removed from Objects on
the limb, the student should observe the chief eminences and hollows ^ ^"^ ***'^*
on the surface of the thigh.

The limit between the thigh and abdomen is marked, in front, by Limits of
the firm band of Poupart's ligament reaching from the anterior above.'^
superior spine of the ilium to the pubis. On the outer side, the
separation is indicated by the convexity of the iliac crest of the hip-
bone, which subsides behind in the sacrum and coccyx. Internally
is the projection of the pubis, from which the bony margin of the
subpubic arch may be traced backwards, forming the inner boundary
of the limb, to the ischial tuberosity.

On the anterior aspect of the thigh, and close to Poupart's liga- hoUow of
ment, is a slight hollow, corresponding with the triangular space of f^^j^^^^
Scarpa, in which the larger vessels of the limb are contained ; and
extending thence obliquely towards the inner side of the limb, is a
slight depression marking the situation of the femoral artery beneath. Groove over
The position of the arterial trunk is marked by the upper three- femoral
fourths of a line dra\m from the centre of the interval between the
symphysis pubis and the anterior superior iliac spine to the inner
condyle of the femur.

At the outer side of the liip, from three to four inches below and Position
behind the anterior part of the iliac crest, will be recognised the t/c^^nter
well-marked projection of the great trochanter of the femur. In a
thin body the head of the femur may be felt by rotating the limb Head of the
inwards and outwards, while the thumb of one hand is placed in f®"^"''-
front in the hollow below Poupart's ligament, and the fingers behind
the great trochanter.

At the knee the outline of the several bones entering into the Bony
formation of the joint may be traced with ease. In front of the of^ineeT^

136 DISSECTION OF THE THIGH.

patella ; jointj when it is half-bent, the rounded prominent patella maj^ be

perceived ; this bone is firmly fixed while the limb is kept in the

bent position, but is moved with great freedom when the joint is

condyles extended, so as to relax the muscles inserted into it. On each side

femur ; of the patella is the projection of the condyle of the femur, that on

the inner side being the larger. If the fingers are passed along the

sides of the patella while the joint is half bent, they will be con-

tuberosities ducted to the tuberosities of the head of the tibia, and to a slight

of the tibia. jjoHow between it and the femur.

The ham Behind the joint is a slight depression over the situation of the ham

behind. ^^ popliteal space ; and on its sides are firm boundaries, which are
formed by the tendons (hamstrings) of the flexor muscles of the knee.
Dissection. Dissection. The limb being placed as l)efore directed, the student
begin-s the dissection with the examination of the subcutaneous fatty
tissue with its nerves and vessels.
Take up At first the integument is to be reflected only from the hollow on

top"of the^ the front of the thigh below Poupart's ligament. An incision about
thigh. five inches in length, and only skin deep, is to be made from the

pubis along the inner border of the thigh (fig. 1, b, ^, p. 3). At
the lower end of the first incision, another cut is to be directed out-
wards across the front of the limb to the outer aspect ('^) ; and, at the
upper end, the knife is to be carried along the line of Poupart's
ligament as far as the crest of the ilium. The piece of skin included
by these incisions is to be raised and turned outwards, without taking
with it the subcutaneous fat.
Superficial The subcutaneous fatty tissue, or the siqyerjicial fascia, forms a
general investment for the limb, and is constructed of a network of
how formed; areolar tissue, with fat or adipose substance amongst the meshes.
As a part of the common covering of the body, it is continuous with
that of the neighbouring regions ; consequently it may be followed
inwards to the scrotum or the labium according to the sex, and
thickness upwards on the abdomen. Its thickness varies in different bodies,
^^"^^' according to the quantity of fat in it ; and when well developed it

may be divided into separate layers. Its relations will be made
more evident by the following dissection.
To raise the Dissection. To reflect the superficial fascia, incisions similar to
fas^Sf^'^^ those made in the skin are to be employed ; and the separation from
the subjacent structures is to be begun below, where the large
saphenous vein, and a condensed or membranous appearance on the
under surface, will mark the depth of the stratum. The layer of
fat may be thrown outwards readily by a few touches of the knife,
when the superficial vessels and inguinal lymphatic glands will come
into view.
Relations of The suhcutaneous layer decreases in thickness, and becomes more
faSr^**^ fibrous near Poupart's ligament ; and on its under aspect it has a
smooth and membranous surface. It conceals the superficial vessels
and the inguinal glands, and is separated by these from Poupart's
ligament*.
Dissection Dissectloil (fig. 54). The inguinal glands and the superficial

vessels are next to be cleaned by the removal of any surrounding

ANATOMY OF SUPERFICIAL PARTS.

137

fat ; but the student is to be careful not to destroy a deeper, very

thin layer of areolar tissue which is beneath them, and is visible on

the inner side of the centre of the limb. Three sets of vessels are

to be dissected out : — One set (artery and vein) is directed inwards to see the

to the pubes, and is named swp&rficial external pudic ; another, vessels^**

Superficial

circumflex iliac

artery.

Fig. 54.

-Dissection op the Superficial Parts op the Thigh
(Illustrations of Dissections).

Vessels

a. Internal saphenous vein.
h. Superficial external pudic.

c. Superficial epigastric.

d. Superficial circumflex iliac.

e. Inguinal glands.

/. Saphenous opening.

Nerves :

1. Ilio-inguinal.

2. External cutaneous.

3. Genito-crural.

4. Middle cutaneous. Small
unnamed vessels accompany the
different nerves to the integuments.

superficial epigastric, ascends over Poupart's ligament ; and the third,
the superficial circumflex iliac, appears at the outer part of the limb.
The large vein towards the inner side of the thigh, to which the
branches converge, is the internal saphenous.

Some of the small lymphatic vessels may be traced from one ij-mphatics
inguinal gland to another.

138

DISSECTION OF THE THIGH.

and nerves.

The arteries
from the
femoral.

One external
pudic
artery ;

another
beneath the
fascia.

Superficial
epigastric.

Superficial
circumflex
iliac.

Veins join
the saphe-
nous.

Inguinal
glands :
two sets.

which
receive
different
lymphatics.

Cribriform
fascia is

an areolar
membrane
over

saphenous
opening :

relation to

femoral

hernia.

A small nerve, the ilio-inguirud, is to be sought on the inner side
of the saphenous vein, close to the pubis ; and a branch of the
genito-crural nerve may be found a little outside the vein.

Superficial Vessels. The small cutaneous arteries at the top
of the thigh are the first branches of the femoral trunk, they pierce
the deep fascia (fascia lata), and are distributed to the integuments
and the glands of the groin and neighbourhood.

The SUPERFICIAL EXTERNAL PUDIC ARTERY (superior ; fig. 54, h)
crosses the spermatic cord in its course inwards, and ends in the
integuments of the penis and scrotum, where it anastomoses with
ofisets of the internal pudic artery.

Another external pudic branch (deep; p. 149) pierces the
fascia lata at the inner border of the thigh, and ramifies also
in the scrotum. In the female both branches supply the labium
pudendi.

The SUPERFICIAL EPIGASTRIC ARTERY (c) passes over Poupart's
ligament to the abdomen, and communicates with branches of tlie
deep epigastric artery.

The SUPERFICIAL CIRCUMFLEX ILIAC ARTERY frecpiently arises in
common with the foregoing and is the smallest of the three branches ;
appearing as two or more pieces at the upper part of the thigh near
the iliac crest, it is distributed in the integuments : it supplies an
offset with the external cutaneous nerve.

A vein accompanies each artery, having the same name as its com-
panion vessel, and ends in the upper part of the saphenous vein,
with the exception of that with the deep external pudic artery :
these veins will be noticed directly.

The SUPERFICIAL INGUINAL GLANDS (e) are arranged in two lines.
An upper set lies across the thigh, near Poupart's ligament ; and a
lower set is situate along the side of the saphenous vein. In the
lower or femoral group the glands are larger than in the upper, and
the lymphatic vessels from the surface of the lower limb enter them.
The upper or inguinal group is joined by the lymphatics of the
penis, by those of the surface of the abdomen, and by those of the
buttock. The glands vary much in numl)er and size ; and not
unfrequently some of the longitudinal set by the side of the vein
are blended together.

Cribriform fascia. Beneath, and to the inner side of, the internal
saphenous vein there is a thin layer of areolar tissue, which is some-
times described as a special deeper layer of the superficial fascia. This
stratum is continued across the aperture in the deep fascia
(saphenous opening ; fig. 54, /) through which the vein dis-
appears ; and being there perforated by many large lymphatic
vessels, as well as by the saphenous vein, the name cribriform fascia
has been given to this part. The cribriform fascia is closely united
to the outer margin of the saphenous opening ; and it is also ad-
herent to the subjacent crural sheath of the vessels in the aperture.
In a hernial protrusion through the saphenous opening, the cribri-
form fascia is stretched and pushed forwards by the tumour, and
forms one of the coverings.

INTERNAL SAPHENOUS VEIN. 139

Dissection. After lia\di}g observed the disposition of the super- Dissectiou
ticial fascia near Poupart's ligament, the student may proceed to of the thigh,
examine the remainder of the subcutaneous covering of the thigh,
together with the vessels and nerves in it.

To raise the skin from the front of the thigh, a cut is to be Take away
carried along the centre of the limb, over the knee-joint, to rather ^^^ ^^^^'
below the tubercle of the tibia. At the extremity of this a trans-
vei-se incision is to be made across the front of the leg, but this is
to reach farthest on the inner side. The skin may be reflected in
flaps iuwards and outwards ; and as it is raised from the front of
tlie knee, a superficial bursa between it and the patella will be
opened.

The saphenous vein is to be first traced out in the fat as far as and follow
the skin is reflected, but in removing the tissue from it the student vem.
should be careful of branches of the internal cutaneous nerve.

The cutaneous nerves of the front of the thigh (fig. 55, p. 140) Seekcutane-
are to be sought in the fat, with small cutaneous arteries, in the of f^^t of
following positions : — On the outer margin, below the upper third, thigh,
is placed the external cutaneous nerve. In the middle of the limb,
l)elow the upper third, lie the two branches of the middle
cutaneous nerve. At the inner margin are the ramifications of the
internal cutaneous nerve — one small offset appearing near the upper
part of the thigh, one or more about half-way do^\Ti, and one of the
terminal branches (anterior) about the lower third.

On the inner side of the knee three other cutaneous nerves are to and on side
be looked for : — One, a branch of the great saphenous, is directed " * *^ '"'^^•
outwards over the patella. Another, the trunk of the great saphe-
nous nerve, lies by the side of the vein of the same name, close to
the lower edge of the surface now dissected. And the third is a
terminal branch (posterior) of the internal cutaneous nerve, which
is close behind the preceding, and communicates with it.

Vessels. All the cutaneous veins on the anterior and inner as- Superficial
pects of the thigh are collected into one ; and this trunk is named ^ ^'"^'
saphenous from its manifest appearance on the surface.

The INTERNAL SAPHENOUS VEIN (fig. 54, rt) is the cutaneous internal
trunk of the inner side of the lower limb, and extends from the vein in
foot to the top of the thigh. In the part of its course now dis- ^^'8^
sected, the vessel lies inferioiiy somewhat behind the knee-joint ;
but as it ascends to its termination, it is directed along the inner
side and the front of the thigh. Near Poupart's ligament it pierces pierces
the fascia lata by a special opening named saphenous, and enters to join the
the deep vein (femoral) of the limb. femoral.

Superficial branches join it both externally and internally ; and Vems join-
near Poupart^s ligament the three veins corresponding mth the °
arteries in that situation, viz., superficial external pudic, superficial
epigastric, and superficial circumflex iliac, terminate in it. Towards may be
the upper part of the limb the veins of the inner side and back of at the top of
the thigh are frequently united into one branch, which enters the the thigh,
saphenous trunk near the aperture in the fascia lata ; and some-
times those on the outer side of the thigh are collected together in

140

DISSECTION OF THE THIGH.

Cutaneous
arteries.

Cutaneous
nerves.

unusual

state.

External
cutaneous,

posterior,
and

anterior
branches.

a similar way. When this arrangement exists three large veins will

be present on the front of the thigh, near the saphenous opening.

On the side of the knee the vein

receives a communicating branch from

the deep veins.

Some unnamed cutaneous arteries are
distributed to the integuments along
with the nerves ; and the superficial
branch of the anastomotic artery (p. 154)
accompanies the saphenous nerve and
its branches near the knee.

Nerves. The cutaneous nerves of
the thigh are derived from branches
of the lumbar plexus, and in greater
number on the inner than the outer
side.

Ilio-inguinal. This nerve is small,
and reaches the surface by passing
through the external abdominal ring
(fig. 55, '^) ; it sui^plies the scrotum, and
ends on the adjacent j^art of the thigh,
internal to the saphenous vein.

Genito-crural. The crural branch
of this nerve from the first and second
lumbar nerves, jiierces the fascia lata
near Poupart's ligament (fig. 55, ")
rather external to the line of the
femoral artery. After or before the
nerve has become sui3erficial it com-
municates with the middle cutaneous
nerve ; and it extends on the anterior
aspect of the thigh as far as midway
between the knee and the pelvis.

Occasionally this branch is of large
size, and takes the place of the external
cutaneous nerve on the outer side of
the limb.

The EXTERNAL CUTANEOUS NERVE

from the second and third lumbar
nerves ramifies on the outer aspect of
the limb (fig. 55, i). At first it is
contained in a prominent ridge of the
fascia lata on the outer margin of the
thigh, where it divides into an anterior
and a posterior branch.
The ^posterior branch subdivides into two or three others, which

arch backwards to supply the integuments half-way down the outer

side of the thigh.

The anterior branch appears on the fascia lata about four inches

from Poupart's ligament and is continued to the knee below the

Cutaneous Nerves
Front op the

External cutaneous.
Middle cutaneous.
Internal cutaneous.
Internal saphenous.
Patellar branch of

saphenous.
Genito-crural.
Ilio-inguinal.
Ilio-hypogastric on the

belly.

CUTANEOUS NEKVES. Ul

other ; it distributes branches laterally, but those towards the
posterior surface are luore numerous, and larger.

Middle cutaneous (tig. 55, 2). The nerve of the centre of the Middle
thigh is a cutaneous offset of the anterior crural (p. 160), and ^"**°^°"''
divides into two branches. It is transmitted through the fascia
lata about three inches from Poupart's ligament, and its branches reaches the
are continued to the knee. In the fat this nerve is united with ^"®®"
the genito-crural and internal cutaneous nerves.

Internal cutaneous. This nerve is derived from the anterior internal
crural trunk, and is divided into two branches (anterior and posterior) <^"^^®<*"^ •
which perforate the fascia at separate places.

The anterior branch becomes cutaneous in the lower third of the the anterior
thigh, in the line of the inner intermuscular septum (fig. 55, ^), ^^"<^^^
along which it is continued to the knee. It is distributed in the extends to
lower third of the thigh, as well as over the patella and the inner ^"^® '
side of the knee-joint, and is united with the patellar branch of
the internal saphenous nerve (fig. 55, »).

The posterior branch (fig. 71, ^, p. 188) perforates the fascia on the the posterior
inner side of the knee, behind the internal saphenous nerve, with J^^f *" *^®
which it communicates ; it furnishes offsets to the upper half of
the leg, on the inner surface.

Other small offsets of the nerve supply the inner side of the thigh, other small
and appear by the side of the saphenous vein. One or two come J]^?^ ^ ^^®
into view near the top of the vein, and reach as far as the middle
of the thigh ; and one, larger than the rest, becomes cutaneous
where the others cease, and extends as far as the knee.

The internal saphenous nerve (fig. 55, ^), a branch of the internal
anterior crural, is continued to the foot, but only a small part of it saphenous
is now visible. It pierces the fascia close below the knee on the passes to
iimer side ; and after communicating with the inner branch of the *^® ^^^ '
internal cutaneous, gives forwards some offsets over the head of the
tibia. Finally, it accompanies the saphenous vein to the leg and
foot.

Its patellar branch (fig. 55, °) appears on the inner side of the a branch on
knee above the preceding, and is soon joined by the internal cuta- P^t*^^*
neous nei-ve. It ends in many branches over the patella ; these
commmiicate with offsets from the middle and internal cutaneous fomis a
ner\'es, and form a network {patellar plexus) over the joint. plexus.

Dissection. Let the fat and the inguinal glands be now clean the
removed from the surface of the fascia lata, the cutaneous nerves ^^^ * '
being thrown aside to be traced afterwards to their trunks.

At the upper part of the thigh the cribriform fascia is to be and define
removed with great care so as to show the saphenous opening, ^nh"g.^^
without injury to the subjacent crural sheath ; and on the other side
of the aperture a semilunar border is to be defined by dividing the
fibrous bands that unite it to the front of the sheath.

The fascia lata is the dee]D aponeurosis of the thigh. It is of Fascia lata
a bluish-white colour, and surrounds the limb with a firm sheath ; i^*^^^*
but in fat bodies it is sometimes so slight as to be taken away mth
the subcutaneous fat.

142

DISSECTION OF THE THIGH.

Ilio-tibial
band.

Apertures
in fascia.

Processes
between the
muscles.

Connected
with bone
at upper
part of
thigh,

dift'erence at
lower part.

Bands on
sides of
patella ;
outer
strong,

inner weak.

Replace
flaps of
skin.

Saphenous
opening :

situation
and

size ;

no defined
border on
inner side ;

on outer
side the
falciform
margin,

It is strongest on the outer aspect of the limb, where it receives
the insertion of the tensor vaginae feinoris, and most of the gluteus
maximus muscle. This thickened part (ilio-tibial hand) is attached
above to the hip-bone, and below to the outer tul)erosity of the tibia
and the outer side of the patella, and helps to keej) the knee-joint
straight in standing, as explained on p. 113.

Numerous apert-ures exist in the fascia for the transmission of the
cutaneous nerves and vessels ; and the largest hole is near Poupart's
ligament, to permit the passage of the internal saphenous vein.

Processes prolonged from the deep surface form septa between,
and fibrous sheaths around, the several muscles. Two of the pro-
cesses are larger than the rest, and are named outer and inner
inter-muscular septa of the thigh ; they are fixed to the femur, so as
to limit on the sides the extensor of the knee. The position of
these partitions is marked by white lines on the surface.

At the top of the thigh the fascia is fixed to the prominent borders
of the pelvis. Thus, it is connected externally with the iliac crest,
and internally with the body of the pubis and the margin of the
pubic arch. Behind, it is joined to the lower end of the sacrum
and coccyx ; and in front, to Poupart's ligament between the pubis
and the iliac crest. Behind the knee-joint the fascia passes un-
interruptedly to the leg ; but in front of the articulation it blends
with an expansion from the extensor muscle, and is continued over
the joint and the patella, though separated from that bone by a
bursa, to be inserted into the heads of the tibia and fibula.

On each side of the patella is a band of almost transverse fibres
(retinaculum), which is attached to and supports the knee-cap.
The outer, thick and strong, is continuous externally with the ilio-
tibial band, and joins the insertion of the vastus externus at its
attachment to the patella : it guides the patella outwards when the
joint is bent. The inner band, of slight strength, is fixed to the
patella lower than the other, and unites with the insertion of the
inner vastus.

Directions. The flaps of skin which were removed from the front
of the thigh, to follow the cutaneous vessels and nerves, are to be
now stitched together to keep moist the subjacent parts ; and the
saphenous ojDening is to be learnt.

The SAPHENOUS OPENING in the fascia lata (fig. 54, /, p. 137), is
an oval aperture, which is situate rather internal to the middle line of
the thigh. It measures about half an inch in width, and one inch
and a half in length. Its upj^er extremity (superior cornu) is at
Poupart's ligament ; and its lower extremity (inferior cornu) is
distant from that structure aljout one inch and a half, and presents
(when dissected) a well-defined margin.

Internally, the saphenous opening has not any distinct margin,
for the membrane here (called the j^ubic jjortion of the fascia lata) is
continued outwards over the subjacent muscle (pectineus), and
behind the femoral vessels, to form the back of the crural sheath.

Externally, the fascia lata {iliac portion) forms a semilunar border,
when detached, the concavity of which is turned downwards and

ANATOMY OF FEMORAL HERNIA. L43

inwards. This edge is named from its shape the falciform margin of

the .saphenous opening (falciform process of Burns) ; it is superficial

to the femoral vessels, and is connected by fibrous bands to the

crural sheath, and to the cribriform fascia. Traced upwards, the winch joins

outer edge blends with the base of Gimbernat's ligament (part of {jgamentf **

Poupart's ligament) : and the upper end of this border, where it is and forms

internal to the subjacent femoral vein, has been named the femoral femoral

ligament.

The rigidity of the margin of the opening is much influenced by tenseness ot
the i^osition of the liml) : for with the finger beneath the upper part varies*^'"
of the falciform border, while the thigh is moved in difierent
directions, this band will be perceived to be most unyielding w^hen
the limb is extended and rotated outwards, and most relaxed when
the thigh is bent and turned in the opposite direction.

Through the lower cornu of the opening the saphenous vein is Parts
transmitted ; and through the upper part, close to the falciform ti^ougifthe
edge, a femoral hernia projects. Lymphatics and one or two super- opening,
ficial arteries also pass through it.

PARTS CONCERNED IN FEMORAL HERNIA.

To understand the anatomy of a hernial protrusion in the thigh. Anatomy
the dissector has to study the undermentioned parts, viz., the crural henn^°™
arch and Gimbernat's ligament, the crural sheath with its crural
canal and ring, together with a partition (septum crurale) between
the thigh and the abdomen.

Dissection (fig. 56). To examine Poupart's ligament and the Dissection
membranous sheath round the femoral vessels, the piece of the gf^^J/"^*^
fascia lata outside the saj^heuous opening is to be reflected inwards
by the following incisions : — One cut is to be begun near the upper
end of the falciform border, and to be carried outwards for one inch
and a half, parallel with and close to Poupart's ligament. Another
is to be directed obliquely downwards and inwards from the termina-
tion of the first, to a little below the inferior cornu of the opening.
When the triangular piece of fascia marked out by those incisions
has been raised and turned inwards, and the fat removed, the tube
on the vessels (crural sheath) will be brought into view as it
descends beneath Poupart's ligament.

With the handle of the scalpel the cniral sheath is to be separated
carefully from Poupart's ligament in front, and from Gimbernat's
ligament on the inner side.

Poupart's ligament or the crural arch (fig. 56, c) is the firm band Cmraiarch:
of the ajDoneurosis of the external oblique muscle of the abdomen, attacii-
which stretches from the front of the iliac crest to the pubis. , '
"WTien viewed on the surface the arch is curved downwards towards
the limb, so long as the fascia lata remains on the thigh. The
outer half is oblique. But the inner half is almost horizontal,
and widens as it approaches the pubis, where it is inserted into
the pubic spine and pectineal line of the hip-bone, forming Gim-
bernat's ligament (fig. 97, j). 263).

144

DISSECTION OF THE THIGH.

parts
closing
hollow
beneath.

The space between the crural arch and the hip-bone is larger in
the female than in the male, and is closed l)y parts passing from
the abdomen to the thigh. The outer half of the interval is filled
by the psoas and iliacus muscles, between which is the anterior
crural nerve, while the external cutaneous nerve lies on the iliacus
near the anterior superior iliac spine : in this part Poupart's liga-
ment is closely bound down to the muscle by its attachment to the
iliac fascia. The inner half is occupied by the femoral vessels and

Fig.

56. — Dissection op the Crural Sheath (Illustrations op
Dissections).

A. Iliac part of the fascia lata,
reflected.

B. Crural sheath, opened,
c. Poupart's ligament.

D. Fascia lata of the thigh in place.

J. Two septa dividing the space
of the crural sheath into thiee com-
partments.

Vessels :

vein, enclosed in the crural sheath
with c, a lymphatic gland.

d. Superficial circumflex iliac.

c. Superficial pudic.

/. Saphenous vein.

Nerves :

1. G-enito-crural.

2. Ilio-inguinal.

a. Femoral artery, and h, femoral 4. External cutaneous.

their sheath, with the upper end of the pectineus muscle ; the
crural branch of the genito- crural nerve issues on the outer side of
the artery.
Gimbernat's Gimbemat^s ligament, or the piece of the tendon of the external
oblique muscle which is inserted into the pectineal line, is about
three-fourths of an inch in length, and is triangular in shape (fig. 97).
Its apex is at the pubic spine : while its base is in contact with the
crural sheath, and is joined by the falciform ligament of the fascia
lata. By one margin (anterior) it is continuous with the crural

ligament :

form and
relations,

THE CRURAL SHEATH. 145

arch, and by the opposite it is fixed to the pectineal line. In the
erect position of the body the ligament is almost horizontal.

The crural ov femoral sheath (fig. 56, b) is a loose tube of mem- Crural
brane around the femoral vessels. It has the form of a funnel,
sloped unequally on the sides. The wide part of the tube is up-
wards ; and the narrow part ceases about two inches below Poupart's relations :
ligament, by blending with the common areolar sheath of the blood-
vessels. Its outer border is nearly straight, and is perforated by
the genito-crural nerve Q). Its inner border is oblique, and is
pierced by lymphatics, superficial vessels, and the saphenous vein (/) ;
this part of the sheath appears in the saphenous opening, and is
connected to the falciform margin and the cribriform fascia. In
front of the crural sheath is the iliac part of the fascia lata.

The sheath is continuous with the fasciae of the abdomen and how formed,
thigh in this way. The anterior part is a prolongation under
Poupart's ligament of the transversalis fascia lining the anterior
abdominal wall ; and the posterior part is formed externally by
the iliac fascia covering the psoas muscle, and internally by the
pubic part of the fascia lata covering the pectineus.

Crossing the front of the sheath, beneath the arch of Poupart's Deep crural
ligament, is a fibrous band, the deep crural arch, which will be ^^^
noticed later on in the description of the transversalis fascia.

Dissection (fig. 56). The student is to now open the crural Open the
sheath by an incision across the front, and to raise the anterior part sheath,
with hooks. Inside the tube are contained the femoral vessels,
each surrounded by its covering of areolar tissue, together with an
inguinal gland ; and if a piece of the areolar casing be cut out over Vessels have
both the artery and the vein, there will be an appearance of two sheath,
thin partitions, the one being situate on the inner side of the vein,
separating this vessel from the gland, and the other (J) between
the vein and the artery.

Interior of the crural sheath. The sheath is said to be divided Contents
into three compartments by two partitions ; and the position of sheath,
the so-called septa has been before referred to — one being internal
to the femoral vein, and the other between the two large vessels.
In the outer compartment is contained the femoral artery (a), lying ^P^J® , .^^
close to the side of the sheath ; in the middle one is placed the three :
femoral vein (b) ; and in the inner space (crural canal) only a
lymphatic gland (c) is situated.

The crural canal (fig. 56) is the innermost space in the interior the inner is
of the crural sheath : — Its length is about a third of an inch, and canaf^^
it reaches from the base of Girabernat's ligament to the upper cornu
of the saphenous opening. It decreases rapidly in size from above
down, and is closed below. The aperture by which the space com-
nmnicates with the cavity of the abdomen is named the crural ring.

In front of the canal are Poupart's ligament and the upper end parts
of the falciform margin of the saphenous opening ; while behind it
is the pectineus muscle. On the outer side of the canal, but within
the sheath, is the femoral vein. Through this channel the intestine
passes from the abdomen in femoral hernia.

D.A. L

146

DISSECTION OP THE THIGH.

Crural ring:

situation
and form

boundaries.

Crural

septum ;

Femoral
hernia :
detinition

first
vertical,

forwards,
and then
upwards,

How it is
to be pushed
back.

The crural ring is the upper opening of the crural canal. It is
on a level with the base of Gimbernat's ligament, and is larger in
the female than in the male. Oval in shape, its greatest measure-
ment is from side to side, in which direction it equals about half
an inch ; and it is filled by a lymphatic gland.

The structures around the ring are the superficial and the deep
crural arch in front, and the pubis covered by the pectineus muscle
behind. Internally is Gimbernat's ligament with the conjoined
tendon ; and externally (but within the sheath) is the femoral
vein.

Septum crurale. That part of the subperitoneal fatty layer which
is placed over the abdominal entrance to this crural canal has been
named crural septum from its position between the thigh and
abdomen. The situation of the septum is now visible, but its
characters will be ascertained in the dissection of the abdomen.

Femoral Hernia. In this kind of hernia there is a protrusion
of intestine into the thigh beneath Poupart's ligament. And the
gut descends in the crural sheath, being placed on the inner side of
the vein.

Course. At first the intestine takes a vertical direction in its
progress from the abdomen, and passes through the crural ring, and
along the crural canal as far as the saphenous opening. At this
spot it changes its course, and is directed forwards to the surface of
the thigh, where it becomes elongated transversely ; and should the
gut protrude still farther, the tumour ascends on the abdomen, in
consequence of the resistance being less in this direction than on
the front of the thigh.

The winding course of the hernia may suggest to the dissector
the direction in which attempts should be made to replace the in-
testine in the abdominal cavity. With the view of making the
bowel retrace its course, it will be necessary, if the protrusion is
small, to direct it backwards and upwards ; but if the hernia is
large, it must be pressed down first to the saphenous opening, and
afterwards backwards and upwards towards the crural canal and
ring.

During the manipulation to return the intestine to its cavity,
the thigh is to be raised and rotated inwards, in order that the
margin of the saphenous opening and the other structures may be
relaxed.

Scarpa's triangular space.

Triangular
space.

This hollow is situate on the front of the thigh, and lies beneath
the superficial depression seen near Poupart's ligament.

Dissection (fig. 57, p. 147). The space will appear on remov-
ing the fascia lata near Poupart's ligament. The muscular boundaries
on the sides may be first dissected, and the muscle on the outer
side (sartorius) should be fixed in place with stitches. Afterwards
the remains of the crural sheath are to be taken away ; and the
femoral vessels are to be followed downwards as far as the sartorius
seek nerves, muscle. On the outer side of the vessels clean the divisions of the

Clean out

Scarpa's

space.

Follow
vessels

SCARPA'S TRIANGULAR SPACE.

147

anterior crural nerve which lie immediately external to the artery,
together with the branches of a deep branch of the artery {profunda
femoris) which are buried in the fat. In removing the fat from ^^ ^^^^

Fig.

Dissection op Scarpa's Triangular Space (Illustrations
OP Dissections).

Muscles : e. Superficial external pudic.

/. Deep circumflex iUac.
g. Deep epigastric.
h. Femoral vein.
i. Inferior external pudic vein.
k. Internal saphenous vein.

Nerves :
The large anterior crural is close
outside the artery.

2. Offset to the pectineus.
8. Middle cutaneous.

4. Internal cutaneous.

5. Genito-c rural.

6. External cutaneous.

A. Sai-torius (unusually large in this
dissection).

B. Iliacus.
c. Tensor fasciae latse.

D. Rectus femoris.

E. Pectineus.

F. Adductor longus.

G. Gracilis.

Vessels :

a. Common femoral artery.

b. Superficial circumflex iliac.

c. Superficial epigastric.

behind the femoral artery, the student is to look for one or two
small nerves to the pectineus muscle, which pass inwards about an
inch below Poupart's ligament.

Scarpa's triangle (fig. 57) is an intermuscular space containing Contents

L 2

148

DISSECTION OF THE THIGH.

extent

base and
sides ;

roof and
floor.

Position of
femoral
artery ;

of vein :

of anterior
crural nerve.

Lymphatics

Femoral
artery:
extent ;

position to
femur and
parts
around ;

division
into two.

Superficial
portion :

relations to
parts
around :

the trunks of the blood-vessels of the thigh, and the anterior crural
nerve, with lymphatics and fat. It extends commonly over the
upper third of the thigh ; but the length varies with the breadth
of the sartorius, and the height at which this muscle crosses
inwards.

The base of the space is at Poupart's ligament ; externally it is
bounded by the inner border of the sartorius ; and internally by
the inner border of the adductor longus.

Towards the surface it is covered by the fascia lata, and by the
integuments with inguinal glands and superficial vessels. The
floor slopes backwards on each side towards the middle of the space ;
it is constructed externally, where it is of small extent, by the
conjoined psoas and iliacus (b) ; and internally by the pectineus
and adductor longus muscles (e and f), between and behind which,
near the large vessels, is a small piece of the adductor brevis.

The femoral artery runs through the deepest part of the hollow,
lying slightly outside the centre of the space, and supplies small
cutaneous offsets, as well as a large deep branch, the profunda ; and
a small offset (external pudic) is directed from it to the scrotum
across the inner boundary. On the inner side of the artery and
close to it is placed the femoral vein, which is here joined by the
saphenous and profunda branches. About a third of an inch
external to the vessel is situate the large anterior crural nerve
which lies deeply at first between the iliacus and psoas, but after-
wards becomes more superficial and divides into branches.

Deep lymphatics accompany the femoral vessels, and are continued
into the iliac glands in the abdomen ; they are joined by the superficial
lymphatics.

Femoral artery (fig. 57 and fig. 59, p. 153) This vessel is a
continuation of the external iliac, and extends from the lower border
of Poupart's ligament to the opening in the adductor magnus
muscle ; at that spot it passes into the ham, and takes the name of
popliteal. Occupying three-fourths of the length of the thigh, the
course of the vessel will be indicated, during rotation outwards of
the limb with the knee-joint half bent, by a line drawn from a
point midway between the symphysis pubis and the anterior
superior iliac spine, to the prominent tuberosity of the inner condyle
of the femur.

In the upper part of its course the artery lies rather internal to
the head of the femur, and is comparatively suj)erficial, being un-
covered by muscle ; but lower down it is placed along the inner
side of the shaft of that bone, and is beneatli the sartorius muscle.
This difference in its relations allows of a division of the arterial
trunk into two portions, an upper, superficial, and a lower, deep.

The upper part of the artery (fig. 57, a), which is now laid bare,
is contained in Scarpa's triangular space, and is from three to four
inches long. Its position in that hollow may be ascertained by the
line before mentioned.

Encased at first in the crural sheath for about two inches, it is
covered by the skin and the superficial fascia, and by the fascia

UPPER PART OF FEMORAL VESSELS. 149

lata and some inguinal glands. At its beginning the artery rests
on the psoas muscle ; and it is subsequently placed over the
pectineus (e), though at some distance from the muscle in this
position of the limb, and separated from it by fat, and the profunda
and femoral veins.

Its companion vein (h) is on the inner side and close to it at the position of
pubis, but is placed behind the artery lower down.

The anterior crural nerve lies on the outer side, being distant nerves,
about a third of an inch near Poupart's ligament ; and the internal
cutaneous branch of the nerve lies over the artery along the edge
of the sartorius. Crossing beneath the vessels is the nerve of the
pectineus (^).

Unusual position, A few examples of transference of the main artery of Unusual
the limb from the front to the back of the thigh have been recorded. In PO«*ition.
these cases the vessel passed from the pelvis through the great sacro-sciatic
foramen, and accompanied the great sciatic nerve to the popliteal space.

The BRANCHES of the artery in Scarpa's triangle are the superficial Branches:—
epigastric and circumflex iliac, two external pudic, and the deep
femoral branch. The cutaneous offsets have been seen (p. 138),
with the exception of the following, which lies at first beneath the
fascia lata.

The deep external pudic artery (fig. 57, e) arises separately from. An external
or in common with, the other pudic branch. It courses inwards ^^ *^*
over the pectineus muscle, and perforates the fascia lata at the
inner border of the thigh to end in the scrotum or labium pudendi,
according to the sex : in the fat it anastomoses with branches of the
superficial perineal artery.

The portion of the artery above the origin of the deep femoral
is called the common femoral, and the part below is styled the
superficial femoral to distinguish it from the deep.

The DEEP femoral artery or the prof iinda femoris {fig. 59,^) Profunda:
arises from the outer side of the common femoral trunk from one
or two inches below Poupart's ligament. Its distribution is to the origin,
muscles of the thigh, and will be afterwards followed. In the f^^P^pa'f
present dissection it may be seen to lie over the iliacus muscle, triangle;
where it gives the external circumflex artery to the outer part of
the thigh ; and then to turn, with a large vein, beneath the trunks
of the superficial femoral vessels to the inner side of the limb.

Variation in origin. The origin of the profunda may approach nearer to p^^n^a
Poupart's ligament until it arrives opposite that band ; or may even go beyond, varies,
and reach the external iliac artery (one example, R. Quain). And the
branch may recede farther from the ligament, till it leaves the parent
trunk at the distance of four inches from the commencement ; but in this
case the circumflex branches usually arise separately from the femoral. In
applying a ligature to the femoral artery in the upper part of the thigh,
the thread should be placed four inches below Poupart's ligament, in order
that the spot chosen may be free from the disturbing influence of so large an
offset.

Femoral vein (fig. 57, h). The principal vein of the limb, Femoral

while in Scarpa's triangle, has almost the same relative anatomy fii-st inside

the artery,

150 DISSECTION OF THE THIGH.

as the artery, and is similarly named ; its position to that vessel,
however, is not the same throughout. Beneath Poupart's ligament
it is on the inner side of the arterial trunk, and on the same level,
and is supported on the pubis between the psoas and pectineus
afterwards muscles ; but it soon winds behind the artery, and is placed
behind it. between the n)ain trunk and its deep branch. In this space it
receives the internal saphenous and deep femoral veins, and a
small branch running with the deep external pudic artery.

DEEP PARTS OF THE FRONT OF THE THIGH.

Muscles on The muscles on the front of the thigh are to be learnt next : they

the tiiigh. are the sartorius and the extensor of the knee ; and at the upper end

of the thigh is the small tensor of the fascia lata. Four muscles are

combined in the extensor, viz., rectus, crureus, vastus externus, and

vastus internus.

Vessels. The external circumflex Ijranch of the profunda artery lies

amongst the muscles and supplies them with branches ; and a large

Nerve. nerve, the anterior crural, furnishes offsets to them.

Take the Disscctioil. To proceed with the deeji dissection, the limb is to

the^front'of ^^^ retained in the same position as before, and the flaps of skin on

the thigh, the front of the thigh are to be thrown aside. The fascia lata is

to be cut along the middle line of the thigh and knee, and to be

reflected to each side nearly to the same extent as the skin. Over

the knee-joint the student is to note its attachment to the edges of

the patella, and its union with a prolongation from the tendon of

the extensor muscle of the knee.

Foilo\y ont In raising the inner piece of the fascia, the narrow sartorius

and^fix"it, iw^scle should be followed to its insertion into the tibia ; and

to prevent its displacement it should be fixed with stitches

along both edges. Care should be taken of the small nerves

in contact with the sartorius, viz., a plexus beneath it at the

middle of the thigh from the saphenous, internal cutaneous and

sppvp n^prvps obturator ; two branches of the internal cutaneous below its

serve nerves

^".^ontact middle — one crossing the surface, and the other lying along the
inner edge of the muscle ; and the trunk of the long saphenous
nerve escaping from Ijeneath it near the knee, with the j)atellar
branch of the same perforating it rather higher.

Dissect the Internal to the sartorius some strong muscles (adductors) are

uc ors, jjj^j^jj^g^ downwards from the pelvis to the femur. The student is to

lay bare the fore jjart of these muscles (fig. 58) ; and beneath the most

superficial (adductor longus), near Avhere it touches the sartorius,

he is to seek a branch of the obturator nerve to the plexus l^efore

and clean mentioned in the middle of the thigh. On the outer side of the

muscle. ^^^ sartorius is the large extensor of the knee, in cleaning which the
knee is to be bent, to make tense the fibres.

Dissect The smaller muscle at the uj)per and outer part of the thigh

fe.S ^^ (tensor fasciae femoris) is also to he cleaned ; and a strip of the
fascia, corresponding with the width of the muscle, should be left

THE FRONT OF THE THIGH.

alon. the outer aspect of the limb. Aiter this slip has been isolated
truest of the taJcia on the outer side of the thigh is to te divided

151

Fig. 58.-ScBrACE View or the Fbo»t o. thb '^:1''^^J^^:T'"'
AND Fascia Lata beiso remoted (Illcstkations Of Dissections).

Muscles :

Sartorius.
Iliacus.

Tensor fasciae femoris.
Rectus femoris.
, Vastus internus.
Pectineus.

G. Adductor longus.

H. Gracilis.

I Tendon of sartorius.

a. Femoral artery.

6. Femoral vein.

c. Internal saphenous vein.

by one or two transverse cuts, and is to be followed backwards to
its insertion into the femur.

152

DISSECTION OF THE THIGH.

Sartorius ;

ongin

course over
the thigh ;

insei-tion ;

relations of
the first or
oblique
portion,

of the
middle.

and of the
lower part ;

Use, the
limb free,

and fixed ;

standing on
one leg.

Divide the
sartorius.

show apo-
neurosis,

and dissect
the nerves

The SARTORIUS (fig. 58, a), is the longest muscle in the body,
and extends from the pelvis to the leg. It arches over the
front of the thigh, passing from the outer to the inner side of the
limb, and lies in a hollow between the extensor on the one side,
and the adductors on the other.

Its origin is tendinous from the upper anterior iliac spinous
process of the hip-bone, and from about half the interval between
this and the inferior process (fig. 47, p. 113). The fibres constitute
a riband-like muscle, which ends in a thin tendon below the knee,
and is inserted into the inner surface of the tibia (fig. 68, p. 179)
— mainly into a slight depression by the side of the tubercle for an
inch and a half, but also, by its upper edge, as far back as the
internal lateral ligament of the knee-joint. From the lower part
of the tendon also is an extension into the fascia of the leg.

The muscle is superficial throughout, and is perforated by some
cutaneous nerves and vessels. Its upper part is oblique, and forms
the outer boundary of Scarpa's triangle ; it rests on the following
muscles (fig. 58) ; iliacus (b), rectus (d), and adductor longus (g), as
well as on the anterior crural nerve and the femoral vessels. The
middle portion is vertical, and lies in a hollow between the vastus
internus (e) and the adductor muscles, as low as the opening for the
femoral artery ; but beyond that aperture, where it bounds the
popliteal space, it is placed between the vastus with the great
adductor in front, and the gracilis (h) with the inner hamstrings
behind. The femoral vessels and their accompanying nerves are
concealed by the middle portion of the muscle. The lower tendi-
nous part (I) rests on the internal lateral ligament of the knee-joint,
being superficial to the tendons of the gracilis and semitendinosus,
and separated from them by a prolongation of their synovial bursa :
from its upper border there is an aponeurotic expansion to join
that from the extensor over the knee ; and from its lower border is
given oflf another which blends with the fascia of the leg. Below
the tendon the long saphenous nerve appears with vessels ; and
piercing it is the patellar branch of the same nerve.

Action. The tibia and femur being free to move, the muscle
bends the knee and hip-joints over which it passes, giving rise to
rotation inwards of the tibia, and outwards of the femur.

With the limbs fixed, the two muscles will assist in bringing
forwards the pelvis in stooping ; and when standing on one leg the
muscle will help to rotate the body, so as to turn the face to the
opposite side.

Dissection (fig. 59). The sartorius is to be turned aside, or
cut through if it is necessary, to follow the remaining part of
the femoral artery.

Beneath the muscle is an aponeurosis between the adductor and
extensor muscles ; this is thin above, and when it is divided the long,
or internal, saphenous nerve will come into view. Parallel to the
saphenous nerve above, but outside it, is the nerve to the vastus
internus muscle, which sends an offset on the surface of the vastus
to the knee-joint : the latter may be traced now, lest it should be

THE FEMORAL VESSELS.

destroyed afterwards. The plexiis of nerves on the inner side of
the thigh may he more completely dissected at this stage.

153

i. Internal circum-
flex artery.

6. Deep external
pudic.

5. Superficial circumflex

iliac artery.
. 8. Anterior cmral nerve.

2. Profunda femoris

artery.
4. External circumflex

artery.

Fig.

5Q -Deep Part of the Femoral Artery and its Brakches, with
Muscles of the Thigh (Quain's Arteries).

1. Superficial femoral artery.

2. Deep femoral artery.

8. Internal circumflex ai-tery.

4. External circumflex artery.

5. Superficial circumflex iliac artery.

6. Deep external pudic artery.

7. Lower part of the aponeurosis
over the femoral artery.

8. Anterior crural nerve.

9. Pectineus muscle.

10. Adductor longua.

11. Gracilis.

12. Vastus internus.

13. Rectus femoris.

14. Sartorius, in part removed.

154

and vessels.

Aponeurosis
over the
femoral
artery

ends below
by a free
border.

Femoral
artery in
Hunter's
canal ;

relations

position of
veins and

saphenous
nerve.

DISSECTION OF THE THIGH.

The femoral vessels and their branches are to be carefully cleaned.
Where the superficial femoral artery passes to the back of the limb
its small anastomotic branch arises : this branch is to be pursued
through the fibres of the vastus internus, and in front of the adduc-
tor magnus tendon, to the knee ; an offset of it is to be followed
with the saphenous nerve.

The aponeurotic covering of the femoral vessels (fig. 59, 7) exists
where they are covered by the sartorius. It is thin above ; but
below it is formed of strong fibres, which are directed transversely
between the vastus internus on the outer side and the tendons of
the adductor muscles behind and to the inner side. Inferiorly,
this membranous structure ceases at the opening in the adductor
magnus Ijy a defined border, beneath which the long saphenous
nerve and the anastomotic vessels escape.

The SUPERFICIAL FEMORAL ARTERY (fig. 59, i) beneath the sartorius
muscle lies in a hollow between the muscles covered by the aponeu-
rotic expansion just described, until it reaches the opening in the
adductor magnus. The passage, thus formed, in which the artery lies,
is called Hunter's canal. Beneath the artery are the pectineus and
the adductor ljre\ds in part, the adductor longus, and a small piece
of the adductor magnus. On the outer side is the vastus internus.

The vein lies close to the artery, on its posterior and outer
aspect ; and in the integuments oftentimes an offset of the saphenous
passes across the line of the arterial trunk.

Lying along the front of the artery is the long saphenous
nerve, wdiich is Ijeneath the aponeurosis before noticed, but is not
contained within the areolar sheath of the vessels.

The femoral Splitting of the artery. Occasionally tlie femoral artery is split into two
artery may below the origin of the profunda ; but in all the cases that have been met

with, the branches have united again above the opening in the adductor

muscle.

be divided.

Branches ;

Anasto-
motic :

superficial,
and

deep part.

Muscular
branches.

Branches. One named branch — anastomotic, and muscular offsets,
spring from this part of the artery.

The anastomotic branch (fig. 62, A-, p. 165) arises close to the opening
in the adductor muscle, and divides at once into two branches,
superficial and deep : —

The superficial branch {n) continues with the saphenous nerve to
the lower border of the sartorius, and piercing the fascia lata,
ramifies in the integuments.

The deep branch {I) is concealed in the fibres of the vastus
internus, and descends in front of the tendon of the adductor
magnus to the inner side of the knee-joint, where it anastomoses
with the articular branches of the popliteal artery. A branch
passes outwards from it in the substance of the vastus muscle, and
forms an arch at the upper border of the patella with an offset of the
superior external articular artery.

Muscular branches. Branches for the supply of the muscles come
mostly from the outer side of the superficial femoral artery ; they
enter the sartorius, the vastus internus, and the adductor longus.

THE QUABHICEPS EXTEKSOR CKtIRlS. 155

The SUPERFICIAL FEMORAL VEIN Corresponds closely with the Supeificiai
femoral artery in its relations and its branches. v'ehu'^*

Dissection. The superficial femoral arteiy and vein are to be To expose
cut across just below the origin of the profunda, and are to be ™ont of the
thrown dowTiwards preparatory to the deeper dissection. After- femur,
wards all the fat, and all the veins, are to be carefully removed
from amongst the branches of the profunda artery and anterior
crural nerve. Unless this dissection is fully carried out, the upper
part of the vastus internus and crureus will not he prepared for
examination.

The TENSOR FASCI.E FEMORIS S. FASCIiE LAT^ (fig. 62, L, p. 165) Teusor

occupies the upper third of the thigh. It takes origin from the femoris

front of the crest of the ilium at the outer aspect, from the anterior arises from

superior spine and from the edge of the notch between this and the pelvis ;

inferior spine as far as the attachment of the sartorius (fig. 47, p. 113).

Its fibres form a fleshy belly about two inches wide, and are inserted

into the ilio-tibial band of the fascia lata about three inches below, ends in

and rather in front of the line of, the great trochanter of the femur. ^^^^^ '

At its origin the muscle is situate between the sartorius and pai'ts
the gluteus medius. Beneath it are the ascending oflsets of the ex- '

ternal circumflex artery ; and a branch of the superior gluteal nerve
enters its under surface. A strong sheath of fascia surrounds the
muscle.

Action. Supposing the limb moveable the muscle abducts the use on
thigh, and may help in rotating inwards the femur. '

When the limb is fixed it will support the pelvis, and assist in on pehis ;
balancing the latter on the femur in walking.

The chief function of the tensor vaginse femoris is, however, to on knee,
act with the gluteus maximus in tightening the ilio-tibial band so
as to support the extended knee.

Dissection. After the tensor has been learnt, the slip of fascia Cut through
extending from it to the knee may be cut through ; and when it is fasda!'^
detached from the muscles around, the rectus may be followed
upwards to its origin from the pelvis.

The QUADRICEPS EXTENSOR CRURIS COUSists of foUT partS or Great exteu-

heads, one long or superficial (rectus), which springs from the sorofknee.
pelvis, and three short or deep (vastus internus, crureus, and vastus
extei-nus) which arise from the femur : all are united below in a
common tendon.

The RECTUS FEMORIS (fig. 59, ^^) gives rise to a fleshy promi- Rectus has
nence on the front of the thigh. It arises from the pelvis by two oriJii\t
tendinous heads ; one, the anterior, is attached to the anterior pelvis ;
inferior iliac spine ; and the other, posterior, is fixed to a rough
mark on the outer surface of the ilium close above the acetabulum
(fig. 47, p. 1 13) : near their origin they join to form a single tendon, insertion
The fleshy fibres terminate l)elow in another tendon, which joins the mon tendon,
aponeuroses of the other muscles in the common tendon.

The rectus is larger in the middle than at the ends ; and its fibres is penni-

are directed from the centre to the sides, giving rise to the condition g^'™^^^^

called pemiiform. Its upper end is covered by the tensor fasciae except

above.

156

DISSECTION OF THE THIGH.

Cut the
rectus,
and display
three deep
heads of
extensor :

define
vastus
extemus

separate
crureus and
vastus
internus,

beginning
below.

and expos-
ing bare
surface of
bone.

Vastus
extemus
is thin at
the origin ;

ends in
common
tendon :

I in
contact
with the
surfaces.

Vastus
internus
arises from
femur and
adductor
tendons ;

femoris, iliacus, and sartorius ; but in the rest of its extent it is
superficial. It conceals branches of the external circumflex artery
and anterior crural nerve, and rests on the crureus and vasti. The
upper tendon of the rectus reaches farthest on the anterior surface ;
while the lower tendon is most extensive on the posterior aspect of
the muscle.

Dissection. To see the remaining muscles, cut across the rectus
near the lower end and raise it without injuring the branches of
vessels and nerves beneath (fig. 59). The muscular mass covering
the shaft of the femur is to be thoroughly cleaned, and its three
parts defined in the following way : —

The division between the vastus extemus on the outer side and :
the crureus in front is readily made in the situation of some vessels
and nerves, which descend along the anterior border of the vastus
externus.

To separate the vastus internus from the crureus, the loAver end
of the rectus must be turned down as far as possible, when a cleft
will be evident in the subjacent tendon above the inner part of the
patella. From this interval the division may be easily carried
upwards between the two muscles, but at the upper end some fleshy
fibres generally need cutting to complete the separation. If the
vastus internus be turned inwards ofi" the crureus, a large part of
the inner surface of the femur will be seen to be free from
muscular attachment.

The VASTUS EXTERNUS lias a narrow attachment to the femur in
comparison with its size (fig. 60, and fig. 61, p. 158). It takes origin
from the upper half of the femur, by a f)iece from half an inch to
an inch thick, which is attached to the root of the neck of the femur,
and the fore and outer parts of the root of the great trochanter ;
then along the outer side of the gluteal ridge, and the upper half
of the linea aspera ; and lastly from the contiguous external inter-
muscular septum. Inferiorly most of the fibres of the muscle end
in a flat tendon, which blends with those of the other portions in
the common tendon, Ijut the lowest fibres of all are inserted directly
into the outer border of the patella.

The vastus externus is the largest part of the t|uadriceps, and
produces the prominence on the outer side of the thigh. Its
cutaneous surface is aponeurotic above, and is partly covered by
the rectus, tensor vaginae femoris, and gluteus maximus muscles.
The deep surface rests on the crureus, and receives branches of the
external circumflex artery and anterior crural nerve.

The VASTUS INTERNUS (figs. 58, E, p. 151) also has a narrow
origin from the lower part of the anterior intertrochanteric line
and from the inner surface of the femur (figs. 60 and 61) along the
linea aspera, from the upper part of the internal supra-condylar
ridge, and, in the lower half of the thigh, from the front of the
tendons of the adductor longus and magnus. The fibres join an
aponeurosis which blends in the common tendon, and is also
attached directly to the inner margin of the patella reaching lower
than the vastus externus.

THE QUADRICEPS EXTENSOR CRURIS.

157

The muscular mass is in part covered by the sartorius and rectus, forms
])ut it projects between those muscles below. Some of the lower ab^"?^"^*^®
fibres are almost transverse, and will be able to draw the patella
inwards.

The CRUREUS arises from the upper three-fourths of the anterior Crureus has

widest

and outer surfaces of the femur, except where they are occupied by origin ;

Gluteus minimus
Vastus externus.

Pyrifonnis.

Obtiutitor internus and gemelli.

Anterior inter-trochanteric
line.

Popliteus.

Fia.

llio-psoas.
Vastus internus.

Subcrureus.

-The Femur prom the Front.

the vastus externus (figs. 60 and 61), and from the lower half of the

external inter-muscular septum. Its fibres end, like the other conamou

parts, in an aponeurosis which enters into the common tendon. ^° '"^ '

The rectus and vasti cover the crureus except for a small extent

at its lower and hinder part. It lies upon the bone and the sub- is deepest
1 part of all.

crureus muscle. ^

The common or suprapatellar tendon resulting from the union of Common

the foregoing is attached to the fore part of the upper border of the above'knee.

patella. It is oblong in shape, and about three inches long. A few

158

DISSECTION OF THE THIGH.

fibres are prolonged over the front of the bone into the ligamentum
patellae below, which forms the continuation of the tendon. Between
Siib-crureal the suprapatellar tendon and the femur there is a bursa, which
^^^^' usually opens into the knee-joint.

Lay bare Disscctioil. Tosee the continuation of the extensor tendon, and its

knee. ^ ^"^ insertion into the tibia, the student should divide along the middle

Obturator externus.

Quadratus femoris,
Ilio psoas.

Pectineus,

Vastus internus.
Adductor brevis.

Adductor longus.
Crureus,

Vastus internus,
Adductor magnus.

Gastrocnemius

/Inner head.
1 Outer head.

Gluteus medius.
Ghiteus maximus.

Vastus externus.

Crureus.

Vastus externus.
Biceps (femoral head).

Plantar! s,

Fig. 61. — The Fkmur from Behind.

line of the patella and knee-joint a thin aponeurotic layer, which is

derived from the lower fibres of the muscles and covers the joint.

On reflecting inwards and outwards the fibrous layer, the tendon

will be exposed.
Infrapa- The infrapatellar tendon, or ligamentum patellce, is about two

inserted"kito ^'^^^^^ l^ng, and is narrower and thicker than the part above the
tubercle of knee. It extends from the lower margin of the patella to the

tubercle of the tibia ; and a bursa separates it from the bone above

its insertion.

tibia ;

EXTERNAL CIRCUMFLEX ARTERY. 159

From the lower part of the vasti muscles a superficial aponeurotic expansion
expansion is derived : this prolongation, which is strongest on the °^^^* '
inner side, is united with the fascia lata and the other tendinous
offsets to form a capsule in front of the joint, and is fixed below to
the heads of the tibia and fibula.

Subcrureiis muscle. Beneath the crureus, near the knee-joint, is a Small sub-
thin layer of pale fibres, which is but a part of the large muscle, muscle
separated from the rest by areolar tissue. Atl ached to the femur in ends on the
the lower fourth, and often by an outer and inner slip, it ends in synovial
aponeurotic fibres on the synovial sac of the knee-joint.

Action. All parts of the quadriceps extend the knee-joint when Use with
the tibia is moveable ; and the rectus can flex the hip-joint over abie^"^°^^'
which it passes. The fleshy bellies are strong enough to break the
patella transversely over the end of the femur, or to rupture some-
times the common tendon.

With the tibia as the fixed point the vasti will bring forwards the with tibia
femur, and straighten the knee, as in rising from the stooping ^^ '
posture and in jumping. The rectus also will stay the pelvis on the
femur, or assist in moving it forwards in stooping.

The subcrureus draws upwards the pouch of synovial membrane how sub-
above the patella in extension of the knee. act?"^

Intermuscular septa. The processes of the fascia lata, which intermus-
limit the extensor muscle laterally, are named external and internal, cular septa
and are fixed to the linea aspera and the lines leading to the condyles ^® ^^^ •
of the femur.

The external septum is the stronger, and reaches from the insertion the outer
of the gluteus maximus to the outer condyle of the femur. It is stronger •
situate between the vastus externus and crureus on the one side,
and the short head of the biceps on the other, to all of which it
gives origin : it is perforated near the outer condyle by the upper
external articular vessels and nerve.

The inner partition is very thin along the side of the vastus the inner is
internus ; and its place is supplied by the strong tendon of the ^^*^^^^^°^*-
adductor magnus between the inner condyle and the linea aspera.

The EXTERNAL CIRCUMFLEX ARTERY (fig. 59,*, p. 153) is the chief External

vessel for the supply of the muscles of the front of the thigh. It artery'^^''

usually arises from the outer side of the deep femoral artery,

but often from the common trunk. It is directed outwards

through the divisions of the anterior crural nerve, and beneath the divides into

sartorius and rectus muscles, and supplies offsets to those muscles.

Its terminal branches are ascending, transverse, and descending : —

The ascending branch is directed beneath the tensor fasciae ascending,
femoris to the outer side of the hip, where it anastomoses with the
gluteal artery, and supplies the contiguous muscles.

The transverse branch, the smallest, divides into two or three transverse,
which enter the vastus externus, and anastomose with the per-
forating arteries.

The descending branch is the largest, and ends in pieces which are a'l^ de-
distributed to the crureus and vastus externus muscles. One con- branches,
siderable branch descends to the knee along the anterior border of

160

Anterior
crural nerve

divides into
two parts.

From its
superficial
part arise —
middle
cutaneous :

internal
cutaneous.

which has
anterior and

posterior
oranches

nerve to
pectineus

branches to
sartorius.

The deep
part gives
off branches

to rectus,

to vastus
extemus,

to crureus,

and to
vastus
intemus

DISSECTION OF THE THIGH.

the vastus externiis muscle in company with the nerve to the same,
and anastomoses with the upper external articular artery ; a small
offset courses over the muscle with a nerve to the joint. j

The ANTERIOR CRURAL NERVE (fig. 59) derived from parts of
the second, third and fourth lumbar nerves supplies the muscles,
and most of the integuments of the front of the thigh, and the
integuments of the inner side of the leg. Soon after the trunk
of the nerve leaves the abdomen and enters the thigh immediately
external to the common femoral artery it is flattened, and is divided
into superficial and deep divisions.

A. The SUPERFICIAL DIVISION gives off the middle and internal
cutaneous nerves, and branches to the sartorius and pectineus muscles.

The middle cutaneous nerve perforates the fascia lata, sometimes
also the sartorius, about three inches below Poupart's ligament, and
extends to the knee (p. 141).

The internal cutaneous nerve sends two or more small twigs
through the fascia lata to the integument of the upper two-thirds of
the thigh, and then divides in front of the femoral artery, or on the
inner side, into anterior and posterior branches. Sometimes these
branches arise separately from the anterior crural trunk.

The anterior branch is directed to the inner side of the knee.
As far as the middle of the thigh it lies over the sartorius, but it
then pierces the fascia lata, and ramifies in the integuments
(p. 141).

The posterior branch remains beneath the fascia lata as far as
the knee. While underneath the fascia the nerve lies along the
inner border of the sartorius, and joins in a plexus, about the
middle of the thigh, with offsets of the obturator, and nearer the
knee, with a branch of the internal saphenous nerve.

The nerve to the pectineus (fig. 57,^, p. 147) is slender, and is
directed inwards beneath the femoral vessels to the anterior surface
of the muscle : sometimes there are two branches.

Two or three branches to the sartorius arise in common with the
middle cutaneous nerve.

B. The DEEP DIVISION of the anterior crural nerve furnishes
branches to the several heads of the quadriceps extensor muscle,
and one cutaneous nerve — the long, or internal, saphenous.

The branch to the rectus enters the deep surface of the muscle ;
from this branch a twig is sent to the hip-joint.

The nerve to the vastus extemus divides into two or more parts
as it enters the muscle. From one of these an articular filament is
often continued downwards to the knee-joint.

Two or three branches to the crureus pass into the anterior surface
of the muscle ; and from the most internal a long twig descends to
the subcrureus and the knee-joint.

The nerve to the vastus intemus (fig. 62,"^, p. 165) is nearly as
large as the internal saphenous, in common with which it often
arises. To the upper end of the vastus it furnishes one or more
branches, and is then continued as far as the middle of the thigh,
where it ends in offsets to the muscle and the knee-joint.

ANTERIOR CRURAL NERVE. 161

Its articular branch (fig. 62, ^) is prolonged on or in the vastus,
and on the tendon of the adductor raagniis, to the inner side of the
knee-joint, where it is distributed over the synovial membrane of
the articulation. This small nerve accompanies the deep branch of
the anastomotic artery.

The internal or long saphenous nerve (fig. 59, p. 153) is the largest and long
branch of the anterior crural. In the thigh the nerve takes the nerve,
course of the deep blood-vessels, and is continued along the artery,
beneath the aponeurosis covering the same, as far as the opening in
the adductor magnus muscle. At that spot the nerve passes from
beneath the aponeurosis, and is prolonged under the sartorius
muscle to the upper part of the leg, where it becomes cutaneous.
It supplies two offsets while it is beneath the fascia in the thigh.

A commuTiicating branch arises about the middle of the thigh, which has a
and crosses inwards beneath the sartorius to join in the plexus of c^mmum-
the internal cutaneous and obturator nerves, or with the internal
cutaneous nearer the knee : this branch is often absent.

The patellar branch springs from the nerve near the knee-joint, andapa-
and perforating the sartorius muscle and the fascia lata, ends in the ^^^'*^ *'^*®*^'
integument over the knee (p. 141).

A branch of the superior gluteal nerve (p. 117) to the deep Nerve of
surface of the tensor fasciae femoris may be followed at this stage ^^9^
nearly to the lower end of the muscle. femoris.

Directions. After the examination of the muscles of the front Take next
of the thigh, with their vessels and nerves, the student is to learn Jore**^^"*^
the adductor muscles, and the vessels and nerves which belong to
them.

Section II.

THE INNER SIDE OF THE THIGH.

The muscles in this position are the three adductors, — longus, ihe adduc-
brevis, and magnus, with the gracilis and pectineus. These have tor muscles
the following position with respect to one another : — Internal to all, and their
and the longest, is the gracilis. Superficial to the others are the P^^^ition.
pectineus and the adductor longus ; and beneath the last two are
the short adductor and the adductor magnus.

In connection with these muscles, and supplying them, are the vessels and
profunda femoris artery with the accompanying vein, and the nerve,
obturator nerve.

Dissection. For the preparation of the muscles, the investing Dissection
fascia and tissue are to be taken away ; and the two superficial of adductor
adductors are to be separated from one another. Let the student muscles,
be careful of the branches of the obturator nerve in connection with ^e^®^-
the muscles, viz., those entering the flieshy fibres, and one issuing
beneath the adductor longus, to join the plexus at the inner side of
the thigh. Lastly, should any fat and veins be left with the Remove
profunda artery and its branches, they must be removed. veins.

The GRACILIS reaches from the pelvis to the tibia (fig. 62, c, p. 165), Gracilis
and is fleshv and riband-like above, but tendinous below. The takes origin

from the
D.A H pelvis ;

162

DISSECTION OF THE THIGH.

is inserted
into tibia ;

position to
other
muscles :

use on knee-
joint and
femur ;

on peh'is.

Pectineus :

origin from
pubis ;

inserted
into femur ;

relations
of surfaces,

and borders;

use on
femur, free

and fixed.

Adductor
longus ex-
tends from
pelvis to
femur ;

relations to
muscles and

muscle arises by a thin aponeurosis, two or three inches in depth,
from the pubic border of the hip-bone close to the margin, viz.,
opposite the lower half of the symphysis, and the upper part of the
pubic arch (fig. 47, p. 113). Inferiorly it is inserted l^y a flat tendon,
about one-third of an inch wide, into the inner surface of the tibia,
beneath and close to the sartorius (fig. 68, p. 179).

The muscle is superficial throughout. For two-thirds of the
thigh it is flattened against the adductors brevis and magnus, so as
to have its borders directed forwards and backwards ; and in the
lower third it intervenes between the sartorius and semimem-
branosus muscles, and helps to form the inner boundary of the
popliteal space. At its insertion the tendon is nearer the knee
than that of the semitendinosus, though at the same depth from the
surface, and both lie over the internal lateral ligament ; from the
tendon an expansion is continued to the fascia of the leg, like the
sartorius. A bursa separates the tendon from the internal lateral
ligament, and projects above it under the sartorius.

Action. It bends the knee-joint if the tibia is not fixed, rotating
inwards that bone, and then brings the movable femur towards
the middle line with the other adductors.

Supposing the foot resting on the ground, the gracilis will aid in
staying the pelvis on the limb.

The PECTINEUS (fig. 58, f, p. 151) is the highest of the muscles
directed from the pelvis to the inner side of the femur. It has a
fleshy origi7i from the pubic portion of the ilio-pectineal line, and
slightly from the surface in front of that line (fig. 47) ; and it is
inserted by a thin tendon, about two inches in width, into the femur
behind the small trochanter, and into the upper part of the line
which extends from that process to the linea aspera (fig. 61,
p. 158).

One surface of the miLScle is in contact with the fascia lata ; and
the femoral vessels lie over its lower part : the opposite surface
touches the obturator externus and adductor brevis muscles, and the
superficial portion of the obturator nerve. The pectineus lies
between the psoas and the adductor longus ; and the internal
circumflex vessels pass between its outer border and the psoas.

Action. It adducts the limb and bends the hip-joint. When
the femur is fixed it can support the pelvis in standing ; or it can
draw forwards the pelvis in stooping.

The ADDUCTOR LONGUS lies below the pectineus (fig. 58, g), and
is triangular in form, with the apex at the pelvis and the base at
the femur. It arises by a narrow tendon from the front of the
pubis in the angle between the crest and the symphysis (fig. 47) ;
and it is inserted into the inner edge of the linea aspera, blending
with the insertion of the subjacent adductors (fig. 61).

This muscle is situate between the gracilis and the pectineus, and
forms part of the floor of Scarpa's triangle. Its anterior surface is
covered near the femur by the femoral vessels and the sartorius ;
the posterior rests on the other two adductors, on the superficial
part of the obturator nerve, and on the deep femoral artery. The

obturator
nerve

ADDUCTOR BREVIS MUSCLE. 163

tendon of insertion is closely united to the adductor magnus and
vastus internus.

Action. With the femur movable, it will flex the hip-joint, and use on
with the aid of the other adductors will carry inwards the limb, so f'^'""'''
as to cross the thigh-bones. In walking it helps the other adductors
to project the limb.

With the femur fixed, the muscle holds and tilts forwards the pelvis, on pelvis.

Dissection. The adductor brevis muscle, with the obturator Dissection
nerve and the profunda vessels, will be arrived at by reflecting the °
two last muscles (fig. 62, p. 165). On cutting through thepectineus accessory
near the pubis and throwing it down, the dissector may find occa-
sionally the small accessory nerve of the obturator, which turns
beneath the outer border ; if this is present, its branches to the hip-
joint and the obturator nerve are to be traced out. The adductor cut adduc-
longus is then to be divided near its origin, and raised with care, so ^o^iongus
as not to destroy the branches of the obturator nerve beneath : its
tendon of insertion also is to be detached from that of the adductor
magnus beneath it, to see the Ijranches of the profunda artery.

Now the adductor brevis will be laid bare. A part of the to show
obturator nerve crosses over this muscle to the femoral artery, and adductor

orGvis ■

sends an oS'set to the plexus at the inner side of the thigh ; and
a deeper part of the same nerve lies beneath the muscle. The
muscle should be separated from the subjacent adductor magnus,
whereon the deep branch of the nerve lies. In this last step of the tmce
dissection, the student should follow the slender articular branch obturator

ncrvp

of the obturator nerve through the fibres of the adductor magnus and branch
(P-130). 1S,S.^

The accessory obturator nerve (Schmidt) is derived from the trunk Accessory
of the obturator, near its origin, and passes from the abdomen over obturator
the brim of the pelvis. In the thigh it turns beneath the pectineus,
and joins the superficial branch of the obturator nerve ; it supplies
an oS'set to the hip-joint "with the articular artery, and occasionally
one to the under-surface of the pectineus.

The ADDUCTOR BREVIS (fig. 62, d) has a fleshy and tendinous Adductor
origin, about one inch and a half in depth, from the front of the n^rowat
pubis below the adductor longus, and close outside the gracilis origin,
(fig. 47). It is inserted, behind the pectineus, into all the line and wide at
leading from the linea aspera to the small trochanter (fig. 61). '"^"^^ '^"'

In front of the muscle are the pectineus and the adductor parts in
longus, with the superficial part of the obturator nerve, and the front,
profunda artery ; but it is gradually uncovered by the adductor
longus below, and the contiguous parts of the muscles are blended
at their insertion into the femur. Behind the muscle is the adductor behind,
magnus, with the deep piece of the obturator nerve and a branch
of the internal circumflex artery. In contact with the upper border and at upper
lies the obturator extemus (f), and the internal circumflex artery ^°'''^^''-
passes between the two.

Action. This muscle add nets the limb with slight flexion of the Use,
hip-joint, like the pectineus. And if it acts from the femur, it an™^^xeT'
will balance and move forwards the pelvis.

164

dissectio:n of the thigh.

Obturator
nerve

is divided
into two.

The super-
ficial part

ends on
femoral
artery, and
joins plexus
in the thigh;

branches are
to hip-joint,

muscular to
adductors.

Deep part of
the nerve

ends in

adductor

magnus

and gives
branch to
knee-joint.

Dissect
profunda.

Profunda
artery:

origin,
course,

and ending

parts
around.

The OBTURATOR NERVE (jfig. 62, 1) is derived from portions of the
second, third, and fourth lumbar nerves, and supplies the adductor
muscles of the thigh, as well as the hip and knee-joints. The
nerve issues from the pelvis through the aperture in the upper
part of the thyroid foramen ; and it divides in that opening into
two parts, which are named superficial and deep, from their
position with respect to the adductor brevis muscle.

A. The superficial 'part (2) of the nerve is directed over the
adductor brevis, but beneath the pectineus and the adductor longus,
to the femoral artery, on which it is distributed : at the lower
border of the last muscle it furnishes an offset or two, joining
in a j)lexus with the internal cutaneous and saphenous nerves
(p. 141), and often helping to supply the integuments.*

In the aperture of exit, this piece of the nerve sends outwards an
articular twig to the hip-joint.

Muscular branches from this superficial part are furnished to the
pectineus (sometimes), adductors longus and brevis, and the gracilis.

B. The deep part C*) of the obturator nerve pierces the fibres of
the external obturator muscle, and, continuing beneath the
adductor brevis, is consumed chiefly in the adductor magnus. The
following offsets are supplied by it : —

. Muscular branches enter the obturator externus as the nerve
pierces it ; others are furnished to the large, and sometimes to the
short adductor.

A slender articular branch (fig. 62,^) enters the fibres of the
adductor magnus, and passes through this near the linea aspera to
reach the popliteal artery, by which it has been seen that it is
conducted to the back of the knee-joint.

Dissection. To prepare the profunda artery and its branches,
as far as they are to be seen on the front of the thigh, it will
be requisite to follow back the internal circumflex artery above
the upper border of the adductor brevis, and to trace the per-
forating branches to the apertures i:i the adductors near the
femur.

The DEEP FEMORAL (fig. 62, c) is the chief muscular artery of
the thigh, and arises from the common femoral about an inch and
a half below Poupart's ligament. At its origin the vessel is placed
on the outer side of the parent trunk ; but it is soon directed
inwards beneath the superficial femoral vessels to the inner side of
the femur, and ends at the lower third of the thigh in a small
branch that pierces the adductor magnus.

In Scarpa's triangle the vessel lies at first on the iliacus muscle.
On the inner side of the femur it is parallel to the superficial
femoral artery, though deeper in position ; and it is placed first
over the pectineus and adductor brevis, and thence to its termination
between the adductus longus and magnus.

* In some bodies the superficial part of the nerve is of large size and has a
distribution similar to that of the inner branch of the internal cutaneous nerve,
the place of which it takes : in such instances it joins freely in the plexus.

ADDUCTOR MUSCLES.

165

Fig. 62, — Deep Dissection of
THE Adductor Muscles,
WITH their Vessels and
Nerves (Iliustrations of
Dissections).

Muscles :

A. Adductor longus, cut.

B. Pectineus, cut.
c. Gracilis.

D. Adductor brevis.

E. Adductor magnus.

F. Obdurator externus.

G. Semimembranosus.
H. Vastus internus.
K. Rectus femoris.

L. Tensor fasciae latae.
N. Piece of the sartorius.
o. Iliacus.
p. Psoas.

Vessels :
a. Femoral artery, and
b. Femoral vein.

c. Trunk of the pro-

funda.

d. Internal, and e, ex-

ternal circumflex.

/. First, g, second, and
h, third perforat-
ing.

i. Muscular of the pro-
funda.

k. Anastomotic of the
femoral, with. I, its
deep, and «, its
superficial branch.
Nerves :

1. Obturator, joined by
the accessory ob-
turator nerve, with

2, the superficial,

and 4, the deep

part.
Cutaneous branch of

the obturator.
Articular branch to

the knee from the

deep part.
Anterior crural nerve.
Internal saphenous,

and 10, its patellar

branch.
Nei-ve to the vastus

internus, and 9, its

articular branch to

the knee.

166

DISSECTION OF THE THIGH.

Branches to
muscles of
the thigh
join freely.

External
circumflex.
Internal
circumflex

ends on
back of
thigh ;

supplies liip-
joint and
muscles.

Three per-
forating
branches :

first;
second ;
third

and the
ending is a
fourth.

Anasto-
motic
branches.

Profunda
vein.

Cut through

adductor

brevis.

Its BRANCHES are numerous to the surrounding muscles on the
front and back of the thigh, and maintain free anastomoses with
other vessels of the thigh ; through these communications the blood
finds its way to the lower part of the limb when the chief artery-
is obliterated either above or below the origin of the profunda.
The named branches are these : —

1. The external circumflex artery (fig. 62, e) has been described in
the dissection of the parts on the front of the thigh (p. 159).

2. The internal circumflex artery (fig. 62, d) arises from the inner
and posterior part of the profunda, and turns backwards between
the psoas and pectineus, but above the adductor brevis. Opposite
the small trochanter it ends in ascending and transverse branches,
which have been seen in the dissection of the buttock (p. 123). It
also supplies off'sets on the inner side of the thigh, viz. : —

An articular artery which enters the hip-joint through the notch
in the acetabulum ; and two muscular branches at the border of the
adductor brevis ; — one ascends to the obturator and the superficial
adductor muscles : the other, which is larger, descends with the
deep division of the obturator nerve beneath the adductor brevis,
and ends in this and the largest adductor.

3. The perforating arteries, three in number, pierce the ten-
dons of some of the adductor muscles close to the linea aspera
of the femur : they supply muscles on the back of the thigh,
and wind round the bone to end in the vastus externus and crureus
(p. 133).

The first (fig. 62, /) begins opposite the lower border of the
pectineus, and perforates the short and great adductors.

The second (g) arises below the middle of the adductor brevis,
and i^asses through the same muscles as the preceding.

The third (h) springs from the deep femoral trunk below the
adductor brevis, and is transmitted through the adductor magnus.
From the second or third perforating vessel a medullary artery is
supplied to the femur.

The terminal branch of the profunda (fourth perforating) pierces
the adductor magnus near the aperture for the femoral arter}^

4. Muscular or anastomotic branches (i) to the back of the thigh
(three or four in number) pass through the adductor magnus at
some distance from the linea aspera, and end in a chain of anasto-
moses in the hamstrings (p. 134).

The PROFUNDA VEIN results from the union of the different
branches corresponding with the off'sets of its companion artery. It
accompanies closely the artery of the same name, to which it is
superficial, and ends above in the common femoral vein.

Dissection. To bring into view the remaining muscles, viz.,
adductor magnus, obturator externus, and the insertion of the psoas
and iliacus, the adductor brevis is to be cut through near the pelvis,
and thrown down. Then the investing layer of fiiscia and areolar
tissue is to be removed from each muscle.

After the adductor magnus has been learnt, detach a few of its
upper fibres to examine the obturator externus.

ADDUCTOR MAGNUS MUSCLE. 167

The ADDUCTOR MAGNUS (fig. 62, e) is triangular in form, with Adductor
its base directed upwards, one side being attached to the femur, and '"asnus :
the other free at the inner side of the thigh.

The muscle arises from the conjoined rami of the pubis and origin is
ischium along their inner margin, and from the lower impression on "*''™^»
the ischial tuberosity (fig. 47, p. 113). The anterior fibres diverge dive^eto
from their origin, being horizontal above but more oblique below, ^^®*^ i«ser-
and are inserted into the back of the femur, from above downwards, ^Q^g ^gjug
along the inner side of the gluteal ridge, into the linea aspera, and horizoutai,
into the internal supracondylar line for about an inch (fig. 61,
p. 158). The posterior fibres, from the ischial tuberosity, are ^^^?^j
vertical in direction, and end at the lower third of the thigh in a
tendon, which is inserted into the inner condyle of the femur,
surrounding the adductor tubercle, and is connected by a fibrous
expansion to the lower part of the internal supracondylar line.

The muscle consists of two parts, which diflFer in their characters, and form
The anterior (puhic), thin and fleshy, forms a septum betwieen the ^^°P* ^•
other adductoi-s and the muscles on the back of the thigh ; but the
posterior (ischial) piece, partly fleshy and partly tendinous, con-
stitutes the inner thick margin of the muscle. On the anterior
surface are the other two adductors and the pectineus, with the Relations of
obturator nerve and the profunda vessels. The posterior surface ' '

touches the hamstring muscles and the great sciatic nerve. In and borders,
contact with the upper border are the obturator externus and the
quadratus femoris, with the transverse branch of the internal cir-
cumflex vessels ; and along the inner border lie the gracilis and the
sartorius. At its attachment to the femur the muscle is closely united
with the other adductors, particularly the adductor longus, and in
its lowest part with the vastus internus. Near the bone it is pierced
by apertures for the passage of the femoral and perforating
arteries.

Action. This muscle is a powerful adductor ; and the part arising ^Tse on
from the tuberosity is also an extensor of the hip. In standing, the . ' ".
latter part of the muscle, acting from the femur, has an important
influence in steadying the hip-joint ; and in walking, the great and '° ^* "'°"
other adductors co-operate with the gluteal muscles externally, to
support the pelvis on the fixed limb.

The opening in the adductor for the transmission of the superficial Opening for
femoral vessels into the popliteal space is tendinous at the anterior, ® ^ ^^^^ *
but fleshy at the posterior aspect. It is situate at the junction of
the upper three-fourths with the lowest fourth of the thigh, and is
larger than is necessary for the passage of the vessels. On the
outside it is bounded by the vastus intemus ; and on the inside by boundaries,
the tendon of the adductor magnus, with some fibres added from the
tendon of the long adductor.

The PSOAS and iliac us (fig. 62) arise separately in the abdomen. Psoas and
but are united in the thigh, the conjoined portion of the muscles the thigh :
lying beneath Poupart's ligament. The psoas (p) is inserted by insertion
tendon into the small trochanter of the femur ; and the fleshy "^^ femur ;
iliac us (o) mainly joins the tendon of the psoas, but a few of its

168

DISSECTIOK OF THE THIGH.

parts
arouud ;

Obturator
externus

origin ;

insertion.

The adduc-
tors cover
it;

and it

touches

hip-joint.

Use.

Detach
obturator.

Obturator
artery

divides into
two :

inner,

and outer
branch.

Branches of
the nerve.

fibres are fixed into a special triangular surface of bone in front of
and below the trochanter (fig. 61).

These muscles occupy the interval beneath Poupart's ligament
between the ilio-pectineal eminence and the anterior superior iliac
spinous process ; and below the pelvis the mass covers the capsule
of the hip-joint, a large bursa intervening. On the front of the
psoas is the common femoral artery, and between the two muscles
lies the anterior crural nerve. The pectineus and the internal
circumflex vessels are contiguous to the inner border, and the
sartorius and vastus internus touch the outer edge.

Action. These muscles act as flexors of the hip-joint ; and the
use of the psoas on the spinal column will be given with the
description of the muscle in the abdomen.

The OBTURATOR EXTERNUS (fig. 62, f) is triangular in form,
with the base at the pelvis and the apex at the femur. The filjres
of the muscle take origin from the outer surface of the obturator
membrane for the inner half, and from the bony circumference of the
thyroid foramen for a corresponding extent, — the bony attachment
being an inch wide opposite the body of the pubis, and reaching
inwards to the adductor brevis and magnus (fig. 47, p. 113). The
fibres are directed backwards and outwards to be inserted by a
tendon into the jjit at the root of the great trochanter.

This muscle is concealed by the pectineus, and adductor brevis
and magnus. It covers the obturator membrane and vessels, and
is pierced by the deep part of the obturator nerve. As it winds
back it is in contact with the lower surface of the hip-joint. The
insertion of the muscle has been seen in the dissection of the
buttock (p. 123).

Action. The muscle is an external rotator of the thigh, and to
a slight extent an adductor and flexor of the hip- joint.

Dissection. By detaching the obturator muscle from the pelvis,
the branches of the artery of the same name will be seen beneath
its fibres. The deep part of the nerve may be followed back to
the foramen at the same time. A better view will be obtained if
this dissection is deferred till after the liml) is removed.

The OBTURATOR ARTERY is a Ijranch of the internal iliac within
the pelvis, and enters the thigh through the top of the thyroid
foramen. In the aperture the artery divides into two branches,
which form a circle on the obturator membrane beneath the muscle : —

The internal branch runs along the inner half of the membrane,
and furnishes offsets to the obturator externus and the upper ends
of the adductor muscles.

The external branch descends close to the outer edge of the
foramen, and after giving a branch inwards to join the lower end
of the preceding, is continued to the ischial tuberosity and the
muscles arising therefrom. Offsets pass to both obturator muscles ;
and an articular twig is given to the hip-joint.

The nerves to the obturator externus come from the deep por-
tion of the obturator, and enter the posterior surface of the muscle.

THE HIP.JOINT.

169

Section III.
THE hip-jo:nt.

Dissection. The capsule of the hip-joint should now be cleaned.
Cut through the iliacus and psoas below Poupart's ligament, and
turn them down. In doing so a large bursa will be opened which j^Jo^^oa"*^^'^
facilitates the movement of these muscles over the front of the joint.
Sometimes it will l^e found that this bursa communicates with the
joint cavity through a thin part in the front of the capsule (fig. 63).
The rectus femoris, the sartorius, the tensor fascise femoris, and
the gluteus minimus should be cleared from the joint, and the
front, outer, and inner parts of the capsule cleaned, as has already
been done at the back. The intimate connection of the reflected

Pu bo-femoral ligament

Origin of rectus
femoris.

Tliin part of capsule,
sometimes per-
forated.

Upper portion of ilio-
femoral ligament.

Intermediate portion
of capsule, some-
times thin.
Lower portion of
ilio-femoral liga-
ment.

Fig. 63.— Anterior Aspect of Hip-joint.

head of the rectus and of the insertion of the gluteus minimus
with the adjacent part of the capsule will be noticed.

The Hip-joixt. This articulation is a ball and socket joint, the Hip-joint,
head of the femur being received into the acetabulum of the hip-
bone. Connecting the bones are the following ligaments : — one to •^^ ^V^*"

° . . " . ments.

deepen the receiving ca^dty, which is named cotyloid; another
between the articular surfaces of the bones — the inUrarticular ; and
a capsule around all.

In the capsule itself the student has to define a wide thick part Define its
in front, and a transverse band near the neck of the femur behind.

170

Capsule :

attachments
above

and below ;

thickness
varies.

Ilio-fenioial
ligament :

attach-
ments ;

division ;

and use.

Pubo-
femoral
band.

Thin part of
capsule.

Circular
band at back
of capsule :

Muscles
around.

DISSECTION OF THE THIGH.

The capsular ligament (fig. 63) is a tliick fibrous case, which
encloses the head and the greater part of the neck of the femur. It
upper margin is attached to the circumference of the acetabulum
close to the edge, as well as to a transverse ligamentous band over
the notch at the lower part of the cavity. Its lower margin is
inserted in front into the anterior intertrochanteric line ; behind, by
a very thin piece, into the neck of the femur about a finger's
breadth from the small trochanter and the posterior intertro-
chanteric line (fig. 64) ; and above, into the neck near the great
trochanter. The capsule differs much in strength and in the
arrangement of the fibres at the fore and hinder parts.

On the front it is strengthened by a broad and thick layer of
longitudinal fibres — the ilio-femoral ligament (fig. 63). This is
fixed above, where it is about an inch broad, to the lower part of
the anterior inferior iliac spine and to a rough mark continued
backwards therefrom on the outer surface of the ilium immediately
above the acetabulum below the reflected head of rectus muscle.
Becoming wider below, it is inserted into the whole length of the
anterior intertrochanteric line ; and its fibres generally form two
stronger bands (fig. 63), which are attached at the upper and lower
ends respectively of the intertrochanteric line, with a thinner part
in the middle. From this arrangement the name of the Y-shaped
ligament has also been given to it. From its position, the ilio-femoral
ligament will arrest extension of the joint ; and when the femur is
fixed in standing it will support the pelvis.

At the inner and fore part of the joint is a much smaller
band, which extends from the prominent portion of the pubis
internal to the acetabulum to the lower end of the anterior
intertrochanteric line, and is named the pubo-femoral ligament
(fig. 63).

Between the ilio-femoral and pubo-femoral ligaments, near the
hip-bone, the capsule is thin, and sometimes presents an open-
ing, through which the bursa under the ilio-psoas communicates
with the joint -cavity.

At the back of the capsule is a band of transverse fibres (zonular
band) (fig. 64, 6), about half an inch wide, which arches like a
collar over the neck of the femur. By its lower edge it is united
to the bone by a thin layer (c) of fibrous tissue and synovial mem-
brane ; at the upper edge it is joined by the longitudinal capsular
fibres (a). It gives insertion to the longitudinal fibres of the
capsule, and prevents that restriction of the swinging movement
which would result from their insertion into the hinder part of the
neck.

At the lower part of the capsule is another thickening (the ischio-
capsular band), which passes from the ischium below the acetabulum
into the lower and back part of the capsule.

Posteriorly the joint is covered by the obturator internus and
gemelli muscles, and anteriorly by the rectus femoris and ilio-
psoas. Above is the gluteus minimus, the tendon of which is
united to the capsule ; and below is the obturator externus.

LIGAMENTS OF HIP-JOINT.

Dissection (fig. 65, p. 173). The capsular ligament is now to
Ije divided over the prominence of the head of the femur, and this
bone l^eing disarticulated hut not detached, the cotyloid and inter-
articular ligaments inside it will appear. The interarticular or round
ligament is attached to the acetabulum by two pieces ; and to bring
these into view, the synovial membrane and areolar tissue must be
removed. The transverse ligament over the notch is also to be defined.

The cotyloid ligament is a narrow band of fibro-cartilage, which is
fixed to the margin of the acetabulum, and is prolonged across the
notch below, so as to form part of the transverse ligament. Its
fibres are not continued around the acetabulum, but are fixed to the
margin of the cavity, and cross one another in the band. It is

171

Cut open
the capsule.

Define round
ligament.

Cotyloid
ligament

attached

round

acetabulum;

Fig. 64. — Hinder Part of the Capsule op the Hip-joint.

Longitudinal fibres.
Zonular band.

c. Thin piece attached to the neck
of the femur about half-way down.

thickest at its attachment to the bone, and becomes gradually thinner
towards the free margin, where it is applied to the head of the femur.

This ligament fills up the hollows in the rim of the acetabulum, use.
deepens the socket for the femur, and makes a flexible margin to
the cavity, which can yield slightly when the neck of the femur is
pressed against it.

The transverse ligament bridges across the notch in the lower and Transverse
inner part of the margin of the acetabulum. It consists partly of
deep special fibres which are attached to the margins of the
notch, and partly of a superficial bundle from the cotyloid liga-
ment Beneath it is an aperture by which vessels and nerves

172

DISSECTION OF THE THIGH.

Round
ligament :

shape and

attach-
ments :

how to see
its action ;

loose in
extension :

tight in
flexion with
adduction
or rotation
outwards.

Synovial
membrane.

Detach the
limb.

Articular
surface of

femur.

Acetabu-
lum cartila-
ginous
externally.

Fat in the
bottom.

Kinds of
motion.

enter the acetabulum to supply the synovial membrane and the fat
in the bottom of that hollow.

The interarticular ligament (ligamentum teres, fig. 65, h) is a
band about an inch long, but of very variable thickness, Avhich
connects the head of the femur with the hip-bone. The ligament
has a triangular form, the apex of the triangle being fixed to the
pit on the head of the femur, and the Ijase joining the transverse
ligament. The free sides of the triangle are formed by two fibrous
bundles, an anterior or pubic (c), which is attached with the trans-
verse ligament to the pubic edge of the cotyloid notch, and a
posterior or ischial {d), which is stronger, and is inserted beneath
the transverse ligament into the ischial border of the notch.

To see the condition of the interarticular ligament in the different
movements of the joint, it should be examined in a specimen in
which the capsule is entire, and the floor of the acetabulum has
been cut out with a chisel from inside the pelvis.

During extension of the joint the ligament is relaxed ; and it
cannot be tightened so long as the fully extended position is
maintained.

In flexion of the joint the ligament is rendered somewhat tighter ;
but it is only fully stretched when, with the joint bent, the femur
is adducted or rotated outwards : the pubic fasciculus of the band
is especially tightened by the adduction, and the ischial slip l)y the
outward rotation.

A synovial membrane lines the capsular ligament, and is continued
along the neck of the femur to the margin of the articular surface.
In the bottom of the cotyloid cavity it is reflected over the fat in
that situation ; and it surrounds the ligamentum teres.

Dissection. To see the surface of the acetabulum, the lower
limb is to be separated from the trunk by dividing the interarticular
ligament, and l)y cutting through any parts that connect it to the
pelvis, and at this stage the pelvic attachments of the interarticular
ligament can be better displayed.

Surfaces of hone. The articular surfaces of the bones are not
completely covered with cartilage.

In the head of the femur is a pit into which the round ligament
is inserted.

The acetabulum is coated with cartilage at its circumference,
except opposite the cotyloid notch, and touches the head of the
femur by this part : this articular surface is deep above, but
gradually decreases towards the edges of the notch.

In the hollow of the cartilage, and close to the notch, is a mass
of fat, covering about one-third of the area of the cotyloid cavity,
which constitutes the " gland of Havers " : it communicates with
the fat of the thigh beneath the transverse ligament.

Movements. In this ball and socket joint, there are the same
kinds of movement as in the shoulder, viz., flexion and extension,
abduction and adduction, circumduction and rotation, but all of
them, with the exception of flexion, are of a much more limited
extent.

MOVEMENTS OF HIP-JOTNT.

173

Flexion and extension. In the swinging movement flexion is freer Swinging
than extension, the thigh being capable of such elevation as to touch "^°^'^'"^"
the belly.

While swinging, the head of the femur revolves in the bottom motion of
of the acetabulum, rotating around a horizontal axis ; and the Jemur^
rapidity and extent of the movements do not endanger the security
of the joint, the head of the bone not having any tendency to
escape.

In extension the strong ilio-femoral ligament (the inner band checks to
especially) is tightened, and stops the movement. Flexion is not

Fig. 65. — Hip- joint opened.

a. Part of the capsule.

6. Jnterarticular ligament : c, its

pubic, and d, its ischial attach-
ment.

naturally arrested by the ligaments of the joint, but by the meeting
of the soft parts of the thigh and abdomen.

In abduction and adduction the femur is remoA^ed from, or brought Lateral
towards, the middle line of the body, and, of the two, abduction is ^^'^'•'^^^'^^
the more extensive.

In l)oth states the head moves in the opposite direction to the motion of
shaft. Thus, as the femur is abducted, the head descends, and a ^^^ ^^^ '
great part of the articular surface projects below the acetabulum ;
and when the limb is raised to its utmost, the upper edge of the
neck meets the edge of the socket, so as to prevent further motion.
As the limb descends and approaches the other, the head rises in

174

state of the
ligaments.

Dislocation
in lateral
movements.

Circum-
duction.

Rotation :

inwards,

and

outwards.

Examine
attachment
of muscles.

DISSECTION OF THE LEG.

the socket of the joint, and is securely lodged, finally, in the deepest
part of the cavity.

In ahduction, the pubo-femoral ligament and lower part of the
capsule are tightened over the projecting head of the femur, the
upper part being relaxed. And in adduction, the outer band of
the ilio-femoral ligament is rendered tense and arrests the movement.

Dislocation may take place in both these lateral movements, the
edge of the cotyloid cavity serving as the fulcrum, on which the
femur can be lifted out of the hollow, and particularly in abduc-
tion with some flexion, for there the head of the femur is against
the thin under-part of the capsule.

In circu7nductio7i, the four kinds of angular m.otion above noticed
take place in succession, viz., flexion, abduction, extension, and
adduction ; and the limb describes a cone, the base of which is at
the foot, and the apex at the centre of the head of the femur.
This movement is less free than in the shoulder-joint.

There are two kinds of rotation, internal and external ; in the
former, the great toe is turned in ; and in the latter it is moved
outwards.

In rotation inwards, the head of the femur glides backwards
horizontally across the acetabulum, the great trochanter coming
forwards ; and the shaft of the bone revolves around a line internal
to it, which losses from the centre of the head to the inner condyle.
During this movement the posterior half of the capsule is put on
the stretch, and the anterior is relaxed.

In rotation outwards, the head of the bone turns forwards in the
cotyloid cavity, and the great trochanter is brought backwards.
The outer band of the ilio-femoral ligament is tightened and checks
the movement.

Dissection. After the limb is removed, the attachments of all
the muscles in the thigh are again to be examined carefully before
the dissection of the leg is undertaken. The muscles should not be
removed from the femur, but about two inches of each left attached
to the bone.

Section IV.

THE FRONT OF THE LEG.

Surface
marking.

In the leg
the tibia is
superficial,

Directions. Before the dissection of the leg is begun, the student
should make himself acquainted, as in the thigh, with the promi-
nences of bone and muscle on the surface, and with the markings
which indicate the position of the larger vessels.

Prominences of bone. The bones of the leg can be traced beneath
the skin from the knee to the ankle-joint. At the inner and fore
part is the tibia, which is subcutaneous in all its extent, and is
limited in front and behind by a sharp edge. Al)ove, it presents
in front a prominent tubercle into which the ligament of the

SDPERFICIAL MARKINGS OF LEG. 175

patella is inserted ; and on each side of tliis the tuberosities of the
bone are superficial. The internal tuberosity is a uniform rounded
prominence ; but the external forms a marked projection at the
outer and fore |)art of the knee. Below, the tibia ends on the
inner side of the ankle in the internal malleolar projection. On
the outer side of the leg the lower half of the fibula may be felt
with ease, but the upper half with more difficulty in consequence
of the prominence of the muscles of the calf. The head of this bone and the
may be recognised below the knee ; and the lower end forms the ^^.^ "^
malleolus on the outer side of the ankle-joint.

At the sides of the ankle are the prominent malleoli, the external Ankle-joint,
being nearer to the heel ; and when the joint is extended, the head
of the astragalus can be felt below the tibia.

Muscles and vessels of the leg. On the back of the leg is the swell Behind are
of the calf : this is formed by the gastrocnemius and soleus J^g^ and ^
muscles, and therefrom descends the firm band of the tendo tendo
Achillis, by which those muscles are connected with the heel, -^^^^i^iis.
Between the tendon and the edge of the tibia, but nearer the J^biai'^'"'^
former, is placed the superficial part of the posterior tibial artery, vessels.
In front, between the tibia and fibula are the flexor muscles of the Line of
ankle and the extensors of the toes, amongst which the anterior ti'bia?"'^
tibial artery lies deeply, and the position of the vessel is indicated artery,
by a line from a point midway between the head of the fibula and
the projection of the external tuberosity of the tibia to the centre
of the ankle-joint.

Prominences of the foot. At the inner border of the foot, about Inner
an inch and a half in front of the internal malleolus, is the t^e foo2
tuberosity of the navicular bone ; while one inch and a half further
forwards is a slight depression marking the articulation between the
internal cuneiform and the metatarsal bone of the great toe. About
the centre of the outer border of the foot is the tuberosity of the Outer
fifth metatarsal bone. A line along the dorsum of the foot, from ^^'
the centre of the ankle-joint to the interval between the inner two artery,
toes, will lie over the position of the main artery.

Position. The limb is to be raised to a convenient height by Position of
blocks beneath the knee, and the foot is to be extended in order ^^^ ^""*''
that the muscles on the front of the leg may be put on the stretch.

Dissection. To enable the dissector to raise the skin from the ^.ise the
front of the leg and foot, one incision should be made along the
middle line from the knee to the toes, and this should be intersected
by cross cuts at the ankle and the root of the toes.

After the flaps of skin are reflected, the cutaneous vessels and Seek the
nerves are to l>e looked for. At the upper and inner part of the nerves^n''
leg are some filaments from the great saphenous nerve ; and at the the leg ;
outer side others, still smaller, from the external popliteal nerve.
Perforating the fascia in the lower third, on the anterior aspect,
the musculo-cutaneoiis nerve will be found, the 1)ranches of which
should be pursued to the toes.

On the dorsum of the foot is a venous arch, which ends laterally on the fo<)t
in the saphenous veins. On the outer side below the malleolus ^d Verv^es^

clean the
fascia.

Cutaneous
veins :

]76 DISSECTION OF THE LEG.

lies the external saphenous nerve ; and about the middle of the
instep the internal saphenous nerve ceases. In the interval between
the great and second toes the cutaneous
part of the anterior tibial nerve appears.
The digital nerves should be traced to
the ends of the toes by removing the
integuments ; and after the several vessels
and nerves are dissected, the fat is to be
taken away, in order that the fascia may
be seen.

The VENOUS ARCH on the dorsum of
the foot has its convexity turned forwards,
and receives digital branches from the
toes ; at its concavity it is joined by
small veins from the instep. Internally
and externally it passes into the saphenous
veins.

internal l^TV ^ IM \ W '^^^ INTERNAL SAPHENOUS VEIN begins

saphenous; B^ \\ 1 KM at the inner side of the great toe, and

in the arch. It ascends in front of the
inner malleolus along the inner side of the
tibia into the thigh. Branches enter it
from the inner border and sole of the
foot.

The EXTERNAL SAPHENOUS VEIN begins
on the outside of the little toe and foot,
as well as in the venous arch ; and it is
continued below the outer ankle to the
back of the leg (p. 187).

Cutaneous Nerves (fig. 66). The
superficial nerves on the front of the leg
and foot are derived mainly from the
musculo - cutaneous and anterior tibial
branches of the external popliteal trunk,
and from the external saphenous nerve
from the two popliteals. Some incon-
siderable off"sets ramify on the front of the
leg from the internal saphenous and
external popliteal.

The musculo-cutaneous nerve (2) ends
on the dorsum of the foot and toes.
Perforating the fascia in the lower third
of the leg with a cutaneous artery, it
divides into two principal branches
(inner and outer), which give dors^il digital nerves to the sides of
all the toes, except the outer part of the little toe and the contiguous
sides of the great toe and the next. The branches may be traced
divides into ^^ ^'^^ integument as ffir as the end of the last phalanx : — '
inner and The inner branch {^) senda one off'set to the inner side of the

foot and great toe, and another to the adjacent sides of the second.

external
saphenous.

Source of
the cutane-
ous nerves.

Musculo-
cutaneous
supplies
most of the
toes;

Fig. 66. — Cutaneous
Nerves op the Front
OP THE Leg and Foot.

1. Anterior tibial.

2. Musculo - cutaneous,
with 3, its inner, and 4,
its outer branch.

5. Internal saphenous.

6. Offsets of external
popliteal, lateral cuta-

CUTANEOUS NERVES ON THE FRONT OF THE LEG. 177

atul third toes : it comimmicates with the internal saphenous and
the anterior tibial nerves.

The outer branch (^) also divides into two nerves ; these lie over outer
the third and fourth interosseous spaces, and bifurcate at the web ™"^ "
of the foot for the contiguous sides of the three toes corresponding
with those spaces : it communicates with the external saphenous
nerve on the outer border of the foot.

The ANTERIOR TIBIAL NERVE (i) becomes cutaneous in the first Anterior
interosseous space, and is distributed to the opposed sides of the founi'/^^^^
great toe and the next. The musculo-cutaneous nerve communi-
cates with it, and sometimes assists in supplying the same toes.

The EXTERNAL SAPHENOUS NERVE (fig. 71, ^ p. 188) COmes from External

the back of the leg below the outer ankle, and is continued along "^^ enous.
the foot to the outside of the little toe ; all the outer margin of the
foot receives nerves from it, and the oifsets towards the sole are
larger than those to the dorsum. Occasionally it supplies both
sides of the little toe and part of the next, joining with the outer
bmnch of the musculo-cutaneous.

Internal saphenous nerve (fig. 66, ^). This nerve is con- internal
tinned along the vein of the same name to the middle of the instep, saphenous,
where it ceases mostly in the integuments, but some branches pass
through the deep fascia to end in the tarsus.

The DEEP FASCIA of the front of the leg is thickest near the Deep fascia
knee-joint, where it gives origin to muscles. On the inner side it is ^^^^^^- ^^s ;
fixed to the anterior border of the tibia ; but externally it is continued intermus-
round to the back of the leg. A strong intermuscular septum is ^^^'^^ ^^^^ >
sent in from the deep surface to the anterior border of the fibula,
separating the anterior and external muscles : and another weaker
process passes liackwards in the upper third of the leg between the
tibialis antic us and extensor longus digitorum. Above, the fascia
is connected to the heads of the leg-bones ; and below, it is
continued to the dorsum of the foot.

Above and below the ankle-joint it is strengthened by some transverse
transverse fibres, and gives rise to the two parts of the anterior ^^^^ ^^ *^®
annular ligament ; and below the end of the fibula it forms
another band, the external annular ligament.

Dissection. The fascia is to be removed from the front of the Take away
leg and the dorsum of the foot, but the thickened bands of the ^ ^^^^j
annular ligament (fig. 67) above and below the end of the tibia
are to be left. In separating the fascia from the subjacent muscles,
let the edge of the scalpel be directed upwards.

In like manner the fascia may be taken from the peronei muscles leave liga-
on the outer side of the filjula, but without destroying the band b^^nd?,'^^
(external annidar ligament) below that bone.

On the dorsum of the foot, the dorsal vessels (fig. 70, p. 183) clean
with their nerve are to be displayed, and the tendons of the short ?essefs.*"
and long extensors of the toes are to be traced to the ends of the
digits. In the leg, the muscles are to be cleaned and separated
from one another, and the anterior tibial nerve and vessels are to
be followed from the dorsum into their intermuscular space, and

178

DISSECTION OF THE LEG.

Anterior
annular
ligament

upper,

horizontal

band,

lower,
Y-shaped
band ;

sheaths
differ in
each.

External

annular

ligament.

Muscles on
the front of
the leg

and foot.

Tibialis
anticus :
origin ;

insertion :

are then to be cleaned as higli as the knee, as they lie deeply
l)etween the muscles.

The ANTERIOR ANNULAR LIGAMENT (fig. 67 and fig. 70, p. 183)

consists of two pieces, upper and lower, which confine the
muscles in their position, the former serving to bind the fleshy
bellies to the bones of the leg, and the latter to keep down the
tendons on the dorsum of the foot.

The wpper part (horizontal hand) is above the level of the ankle-
joint and is attached laterally to the bones of the leg ; it possesses
one sheath with synovial meml)rane for the tibialis anticus.

The lower part is situate in front of the tarsal bones. It is
attached externally by a narrow piece into the upper surface of the
OS calcis, in front of the interosseous ligament ; and internally it is
thin and widened, having a variously defined thickening at its
upper part where it passes to the internal malleolus, and another
below where it blends with the fascia on the inner side of the foot ;
the latter in this place being deep to the tibialis anticus tendon.
In view of its single stem externally and the two diverging thicken-
ings internally, this portion of the anterior annular ligament is
often called the Y-shaped band. Beneath this part of the liga-
ment there are the three sheaths : an inner one for the tibialis
anticus ; an outer for the extensor longus digitorum and peroneus
tertius ; and an intermediate one for the extensor hallucis. Separate
synovial membranes line the sheaths.

The EXTERNAL ANNULAR LIGAMENT is placed below the fibula,
and is attached on the one side to the outer malleolus, and on the
other to the os calcis. Its lower edge is connected by fibrous tissue
to the sheaths of the peronei muscles on the outer side of the os
calcis. It contains the two lateral peronei muscles in one com-
partment ; and this is lined by a synovial membrane, which sends
two offsets below into the separate sheaths of the tendons.

The Muscles on the Front of the Leg (fig. 67 and fig. 69,
p. 181) are four in number. The large muscle next the tibia is
the tibialis anticus ; that next the fibula, the extensor longus
digitorum ; while a small muscle, apparently the lower end of the
last with a separate tendon to the fifth metatarsal bone, is the
peroneus tertius. The muscle between the tibialis and extensor digi-
torum, in the lower part of the leg, is the extensor proprius hallucis.

On the dorsum of the foot only one other muscle appears, the
extensor brevis digitorum.

The tibialis anticus reaches the tarsus : it is thick and fleshy
in the upper, but tendinous in the lower part of the leg. It arises
from the outer tuberosity, and the upper half of the external surface
of the tibia (fig. 68) ; from the contiguous part of the interosseous
membrane ; and from the fascia of the leg, and the intermuscular
septum between it and the extensor longus digitorum. Its tendon
begins below the middle of the leg, and passes beneath both pieces
of the annular ligament, where it is surrounded by a synovial
sheath, to be inserted into the internal cuneiform bone, and the
metatarsal bone of the great toe.

MUSCLES ON THE FRONT OF THE LEG.

179

The muscle is subaponeurotic. It lies at first outside the tibia, parts in
resting on the interosseous membrane ; but it is then placed ^^^^^^ i
successively over the end of the tibia, the ankle-joint, and the inner
tarsal bones. On its outer side are the extensor muscles of the toes,
and the anterior tibial vessels and nerve.

Action. Supposincr the foot not fixed, the tibialis bends the use on the
ankle, and raises the inner border of the toot.

foot, free

Peroneus tertius.

Tendon of peroneus

longus.
Tendon of peroneus

brevis.
Tendons of extensor

longus digitorum.

Extensor expansions.

Extensor longus

digitorum.
Sartorius.
Gracilis.

Semitendinosus.
Tibialis posticus.

Extensor longus
hallucis.

Fig. 67. — Muscles on the
Front op the Leg.

Fig. 68. — The Tibia and Fibula
FROM THE Front.

If the foot is fixed, it can, with the tibialis posticus, lift the inner a"d fi^^d
border and support the foot on the outer edge.

If the tibia is slanting backwards, as when the advanced limb f"4aikbm*
reaches the ground in walking, it can bring forwards and make
steady that bone.

The EXTENSOR PROPRius HALLUCIS is deeply placed at its origin i^^^y'J"'^
between the former muscle and the extensor longus digitorum, but haifucis ;
its tendon becomes superficial on the dorsum of the foot. The
muscle arises from the middle two-fourths of the narrow anterior

N 2

180

DISSECTION OF THE LEG.

origin from
tibula

insertion to
great toe ;

it crosses
the vessels :

use on great
toe:

on tibia.

Extensor

longus

digitorum

from
tibia and
libula ;

insei-ted
into four
outer toes ;
arrange-
ment of the
tendons on
the toes ;

relations of
the muscle :

use on toes
and ankle :

on tibia.

Peroneus
tertius :

origin ;

surface of the fibula (fig. 68), and from the interosseous membrane
for the same distance. At the ankle it ends in a tendon, which
comes to the surface through a sheath in the lower piece of the
annular ligament, and continues over the tarsus to be inserted into
the base of the last phalanx of the great toe.

The anterior tibial vessels lie on the inner side of the muscle at
its origin, but afterwards on the outer side of its tendon, so that
they are crossed by it in the lower third of the leg.

Action. It straightens the great toe ])y extending the phalangeal
joints, and afterwards bends the ankle.

When the foot is fixed on the ground and the tibia slants back-
wards, the muscle can draw forwards that bone.

The EXTENSOR LONGUS DIGITORUM is fleshy in the leg, and tendi-
nous on the foot, like the other muscles. Its oi'igin is from the
head, and upper three-fourths of the anterior surface of the
fibula, from the external tuberosity of the tibia (fig. 68), from
about an inch of the upper part of the interosseous membrane,
and from the fascia of the leg and the intermuscular septum on
each side of it. The tendon enters its sheath in the annular
ligament with the peroneus tertius, and divides into four pieces.
Below the ligament these slips are continued to the four outer
toes, and are inserted into the middle and ungual phalanges in
the following manner. On the first phalanx the tendons of the
long and short extensor join with prolongations from the inter-
ossei and lumbricales to form an aponeurosis ; but there is no
tendon from the short extensor to the expansion on the little toe.
At the distal end of the first phalanx the aponeurosis is divided
into three parts — a central and two lateral ; the central piece is
inserted into the base of the middle phalanx, and the lateral parts
unite at the front of the middle, and are fixed into the last phalanx.

In the leg the muscle is placed between the peronei on the one
side, and the tibialis anticus and extensor proprius hallucis on the
other. It lies on the fibula, the lower end of the tibia, and the
ankle-joint. In the foot the tendons rest on the extensor brevis
digitorum ; and the vessels and nerve are internal to them.

Action. The muscle extends the four outer toes, acting mainly
on the metatarso-phalangeal joints ; it can also bend the ankle-joint.

If the tibia is inclined back, as when the foot reaches the ground
in walking, it will be moved forwards by this and the other muscles
on the front of the leg.

The PERONEUS TERTIUS is situate l:)elow the extensor longus digi-
torum, with. which it is united. It arises from the lower fourth
of the anterior surface of the fibula (fig. 68), from the lower end
of the interosseous membrane, and from the intermuscular septum
between it and the peroneus brevis muscle ; it is inserted into the
base of the metatarsal bone of the little toe on the upper surface
near its inner border.

This muscle has the same relations in the leg as the lower part
of the long extensor, and is contained in the same space in the
annular ligament.

ANTERIOR TIBIAL VESSELS.

Action The mn.cle assists the tibialis anticus in bending the -e^^t^
ankle ; bnt it differs from that muscle in raising the outer border .^^^^^^

181

Anterior tibial
artery

Fig, 69 — Dissection of the Frokt of the Leg (Quain's Arteries).

1. Tibialis anticus muscle.

2. Extensor hallucis and extensor
longus digitomm drawn aside.

3. Part of the anterior annular
ligament.

4. Anterior tibial artery : the
nerve outside it is the anterior tibial.

of the foot, and thus helps the other peronei in producing the move-
ment of eversion.

The ANTERIOR TIBIAL ARTERY (fig. 69) extcnds from the bifuF- Anterior
cation of the popjiteal trunk to the front of the ankle-joint. At artery- :
this spot it becomes the dorsal artery of the foot.

182

DISSECTION OF THE LEG.

course and
extent ;

direction ;

relations to
parts
around ;

position of
veins

and nerve ;

branches : —

Muscular.

Cutaneous.

Recurrent.

Superior
fibular.

Malleolar :

internal and
external.

Dorsal
artery :

extent and
course :

relations ;

The course of the artery is forwards through the aperture in the
upper part of the interosseous membrane, along the front of that
membrane, and over the tibia to the foot. A line drawn along the
front of the leg from a point midway between the projection of the
outer tuberosity of the tibia and the head of the fibula to the centre
of the ankle will mark the position of the vessel.

For a short distance (about two inches) the artery lies between
the tibialis anticus and tlie extensor longus digitorum ; afterwards
it is placed between the tibial muscle and the extensor proprius
hallucis as far as the lower third of the leg, where the last muscle
becomes superficial and crosses over the vessel to its inner side. The
vessel rests on the interosseous membrane in two-thirds of its extent,
being overlapped by the fleshy bellies of the contiguous muscles, so
that it is at some depth from the surface ; but it is placed in front
of the tibia and the ankle-joint in the lower third, and is there
comparatively superficial between the tendons of the muscles.

Venae comites entwine around the artery, covering it very closely
with cross branches in the upper part. The anterior tibial nerve
approaches the tibial vessels from the outer side in tlie upper third
of the leg, and continues with them, lying along their anterior
aspect to their lower end, where it is again on the outer side.

Branches. In its course along the front of the leg the anterior
tibial artery furnishes numerous muscular and cutaneous branches ;
and near the knee and ankle the following named branches take
origin : —

a. The anterior tibial recurrent artery is given off as soon as
the vessel appears through the interosseous membrane, and ascend-
ing through the tibialis anticus, ramifies over the outer tuberosity
of the tibia, where it anastomoses with the other articular arteries.

b. The superior fibular branch runs upwards through the highest
part of the extensor longus digitorum to the superior tibio-fibular
articulation, to which, with the neighbouring parts, it is dis-
tributed.

c. Malleolar branches (internal and external) arise near the ankle-
joint, and are distributed over the ends of the tibia and fibula. The
internal is the smaller, and less constant in origin ; it anastomoses
with twigs of the posterior tibial artery. The external communi-
cates with the anterior peroneal artery (fig. 70), which comes
through from the back between the tibia and fibula just above the
lower tibio-fibular articulation and will be found to be one of the
terminal branches of the peroneal artery (p. 196).

The DORSAL ARTERY OF THE FOOT (fig. 70) is the Continuation of
the anterior tibial, and extends from the front of the ankle-joint to
the upper part of the first interosseous space : at this interval it
passes downwards between the heads of the first dorsal interosseous
muscle, to end in the sole, where it will be subsequently examined
(p. 208).

The artery rests on the inner part of the tarsus, viz., the astra-
galus, the navicular, and middle cuneiform bones ; and it is covered
by the integuments and the deep fascia, and by the inner piece of

DORSAL ARTERY OF THE FOOT.

183

the extensor brevis muscle. The tendon of the extensor halhicis lies
on the inner side, and that of the extensor longiis digitorum on the
outer, but neither is close to the vessel.

The veins have the same position with respect to the artery as in position of

the leg ; and the nerve is external to it.

veins and
nerve.

Peculiarities. On the dorsum of the foot the artery is often external to a Varieties in
line drawn from the centre of the ankle to the back of the first interosseous dorsal

artery.

Anterior peroneal.

Tarsal.

Tendon of peroiieus
tertius.

Metatarsal

Posterior perforating.

2nd, 3rd, and 4th
dorsal interosseous.

Tendons of extensor
longus digitorum.

Tendons of extensor
brevis digitorum

Doi-salis pedis.

Internal tarsal
(occasional).

Extensor longus
hallucis.

Perforating branch.

1st dorsal
interosseous.

Fig. 70. — Arteries on Dorsum of Foot.

space. The dorsal artery may also be reinforced or replaced by a large
anterior peroneal branch.

Branches. Small offsets are given to the integuments, and the Branches:
bones and ligaments of the inner side of the foot. From the outer
side of the vessel proceed two larger branches named tarsal and
metatarsal ; and an interosseous branch is furnished to the first
metatarsal space.

a. The tarsal branch (fig. 70) arises opposite the head of the Tarsal,
astragalus, and runs beneath the extensor brevis digitorum to the

184

DISSECTION OF THE LEG.

Metatarsal,

which gives
interos-

and per-
forating.

First inter-
osseous.

Anterior
tibial veins.

Divide

extensor

longus.

Extensor
brevis
digitorum :

sends ten-
dons to four
inner toes ;

relations ;

Cut through

extensor

brevis

and annular
ligament :

outer border of the foot, where it divides into twigs that inosculate
with the metatarsal, external plantar, and anterior peroneal arteries :
it supplies offsets to the extensor muscle beneath which it lies.

b. The metatarsal branch (fig. 70) takes an arched course to the
outer side of the foot, near the l)ase of the metatarsal bones and
beneath the short extensor muscle, and anastomoses with the
external plantar and tarsal arteries.

From the arch of the metatarsal l)ranch three dorsal interosseous
arteries are furnished to the three outer metatarsal spaces : and the
external of these sends a Ijranch to the outer side of the little toe.
They supply the interosseous muscles, and divide at the cleft of the
toes into two small dorsal digital branches.

At the fore part of the metatarsal space each interosseous branch
is usually connected with the corresponding digital artery in the
sole of the foot by means of the anterior 'perforating tu'ig; and at the
back part of each space a small branch, posterior perforating, comes
from the plantar arch.

c. The first dorsal interosseous artery arises from the main trunk
as this is about to leave the dorsum of the foot ; it extends forwards
in the space between the first two toes, and is distributed like the
other dorsal interosseous offsets.

The ANTERIOR TIBIAL VEINS have the same extent and relations
as the vessel they accompany. They take their usual position
along the artery, one on each side, and form loops around it by
cross branches ; they end in the popliteal vein. The branches
they receive correspond with those of the artery ; and they com-
municate with the internal saphenous vein.

Dissection. To examine the extensor l^revis digitorum on the
dorsum of the foot, cut through the tendons of the extensor longus
and peroneus tertius below the annnlar ligament, and throw them
towards the toes. The hinder attachment of the muscle to the os
calcis is to be defined.

The EXTENSOR BREVIS DIGITORUM arises from the anterior
extremity of the os calcis at its upper and outer part, and from the
lower band of the anterior annular ligament. Over the metatarsal
bones the muscle ends in four tendons, which spring from as many
fleshy bellies, and are inserted into the four inner toes. The tendon
of the great toe has a distinct attachment to the base of the first
phalanx ; but the rest are united to the outer side of the long
extensor tendons, and assist to form the expansion on the first
phalanx (p. 180).

The muscle lies on the tarsus, and is partly concealed by the
tendons of the long extensor. Its inner belly crosses the dorsal
artery of the foot.

Action. Assisting the long extensor, it straightens the four
inner toes, separating them slightly from each other.

Dissection. The branches of artery and nerve which are
beneath the extensor brevis will be laid bare by cutting across that
muscle near its front, and turning it upwards.

By dividing the lower band of the annular ligament over the

NERVES OF FRONT OF LEG. 185

tendon of the extensor hallucis, and throwing outwards the external
half of it, the different sheaths of the ligament, the attachment to
the OS calcis, and the origin of the extensor brevis digitorum from
that bone may be observed.

The anterior tibial and mnsculo-cutaneous nerves are now to be follow up
followed upwards to their origin from the external popliteal ; and ^^ "^"^s-
a small branch to the knee-joint from the same source is to be traced
through the tibialis anticus.

Nerves of the Front of the Leg. Between the fibula and Xerves of
the peroneus longus muscle the external popliteal nerve divides into the i™" ^
the musculo-cutaneous and anterior tibial ; and from the beginning
of the anterior tibial nerve, or the end of the popliteal trvmk, a
small branch called the recurrent articular is given off.

The recurrent articular branch takes the course of the Recurrent,
arterv of the same name through the tibialis anticus muscle, in
which most of its fibres end. A small twig may be followed to the
knee-joint.

The musculo-cutaneous nerve is continued between the extensor Muscuio-
longus digitorum and the peronei muscles to the lower third of the ^" ^'^^ous
leg, where it pierces the fascia, and is distributed to the dorsum of
the foot and the toes (p. 176). Before the nerve becomes cutaneous supplies
it furnishes branches to the two larger peronei muscles. perouei.

The ANTERIOR TIBIAL NERVE (fig. 69, p. 1 8 1 ) is directed beneath Anterior
the extensor longus digitorum, and reaches the tibial artery in the the artery :
lower part of the upper third of the leg. From this spot it takes the
same course as the vessel along the leg and foot to the first interosseous
space (p. 182). In the leg it lies for the most part in front of the
anterior tibial vessels, but on the foot it is generally external to the
dorsal artery and terminates between the first and second toes (p. 1 7 7 ).

Branches. In the leg the nerve supplies the anterior tibial branches to
muscle, the extensors of the toes, and the peroneus tertius. On the ™uscles.
dorsum of the foot it furnishes a considerable branch to the short
extensor ; this becomes enlarged, and gives offsets to the articu-
lations of the foot.

Muscles on the Outer Side of the Leg (fig. 67 and fig. 74, External
}). 192). Two muscles occupy the situation, and are named peroneal muscles of
from their attachment to the fibula ; they are distinguished as long
and short. Intermuscular processes of fascia, which are attached to
the fibula, isolate these muscles from others.

The peroneus longus (fig. 67 and fig. 74, g), the more superficial peroneus
of the two muscles, passes into the sole of the foot round the outer longus :
border. It arises from the outer tuberosity of the tibia by a small origin from
slip, from the head, and the outer surface of the shaft of the fibula *^^ iihuia ;
for two-thirds of the length, gradually tapering downwards (fig. 68,
p. 179), and from the fascia and the intermuscular septa. Inferiorly,
it ends in a tendon which is continued through the external annular
ligament with the peroneus brevis, lying in the groove at the back
of the external malleolus ; and it passes finally in a separate sheath
below the peroneus brevis along the side of the os calcis, and
through the groove in the outer border of the cuboid bone, to the

186

DISSECTION OF THE LEG.

insertion
into bones
of the foot ;

relations in
the leg ;

use on foot,
free,

and fixed ;
on the leg.

Peroneiis
brevis is
attached to

fibula,
and fifth
metatarsal
bone ;

relations :

use on foot,
free,

and fixed ;
on the leg.

sole of the foot. Its position in the foot and its insertion will be
described later on (p. 212).

In the leg the muscle is immediately beneath the fascia, and lies
on the peroneus brevis. Beneath the annular ligament it is placed
over the middle piece of the external lateral ligament of the ankle
with the peroneus brevis, and is surrounded by a single synovial
membrane common to both. The extensor longus digitorum and
the soleus are fixed to the fibula in front of, and behind it respec-
tively.

Action. With the foot free, the muscle extends the ankle ; then
it can depress the inner, and raise the outer border of the foot in
the movement of eversion.

When the foot rests on the ground, it assists to lift the os calcis
and the weight of the body, as in standing on the toes, or in
walking. And in rising from a stooping posture it draws back
the fibula.

The PERONEUS BREVIS (fig. 74, h) reaches the outer side of th
foot, and is smaller and deeper than the preceding muscle. I
arises from the outer surface of the shaft of the fibula for about th
lower two-thirds, extending upwards by a pointed piece in front o!
the peroneus longus (fig. 68), and from the intermuscular septum^
on each side. Its tendon passes with that of the peroneus longus
beneath the external annular ligament, and is placed next the fibula
as it turns below this bone. Escaped from the ligament, the tendon
enters a distinct fibrous sheath, which conducts it along the tarsus
to its insertion into the tuberosity at the base of the metatarsal bone
of the little toe on the outer side.

In the leg the muscle projects in front of the peroneus longus.
On the outer side of the os calcis it is contained in a sheath above
the tendon of the former muscle ; and each sheath is lined by a
prolongation from the common synovial membrane behind the outer
ankle.

Action. If the foot be unsupported, this peroneus extends the
ankle and moves the foot upwards and outwards, everting it.

If the foot be supported it is able to raise the heel, and to
bring back the fibula as the body rises from stooping.

Section Y.

THE BACK OF THE LEG.

Take away
the skin.

Position. For the dissection of the back of the leg, the limb is
to be placed on its front, with the foot over the side of the dissecting
table ; and the muscles of the calf are to be put on the stretch by
fastening the foot.

Dissection. For the removal of the skin, one cut should be
made along the middle of the leg to the sole of the foot, where a
transverse incision is to be carried over the heel. The two resulting

SUPERFICIAL VEINS AND NERVES. 187

flaps of skin may be raised, the outer one as far as the fibula, and
the other as far as the inner margin of the tibia.

In the fat the cutaneous nerves and vessels are to be followed. Seek
On the inner side, close to the tibia, are the internal saphenous nerves^n''
vein and nerve, together with twigs of the internal cutuneoiis nerve the fat.
near the knee. In the centre of the leg lies the external
saphenous vein, with the small sciatic nerve as its companion
above, and the external saphenous nerve below the middle of the
leg. On the outer side cutaneous offsets of the external popliteal
nerve will be met with.

The superficial fascia, or the fatty layer of the back of the leg, is Superficial
least thick over the tibia. Along the line of the superficial vessels
it may be separated into two layers.

Superficial Veins. Two veins appear in the dissection of the Two super-
back of the leg, the inner and outer sai>henous. ^^^^ veins.

The INTERNAL, OR LONG, SAPHENOUS VEIN (fig. 72, fZ, p. 189) Internal

has already been examined in tlie front of the leg (p. 176), and in "^Phenous.
this part it will be seen to receive various superficial tributaries and
deep roots from the til>ial veins.

The EXTERNAL, OR SHORT, SAPHENOUS VEIN (fig. 71, c) haS External

already been examined at its origin (p. 176), and in this part it saphenous,
will be seen to course along the back of the leg to the ham, where
it ends in the popliteal vein. It receives large branches about
the heel, and others on the back of the leg, communicating with
the internal saphenous.

Cutaneous arteries accompany the superficial veins and nerves of Cutaneous

., 1 J. - X arteries.

the leg.

Cutaneous Nerves (fig. 71). The nerves in the fat of the cutaneous
back of the leg are prolongations of branches already met with, "^'^'^s.
viz., the internal and external saphenous, external popliteal, small
sciatic, and internal cutaneous of the thigh.

The INTERNAL SAPHENOUS NERVE (fig. 7I,'^)haS already been internal

examined (pp. 161 and 177), and a few additional twigs will be ^P^«"°''^-
cleaned in this dissection.

The EXTERNAL OR SHORT SAPHENOUS NERVE (fig. 71, 5) is External

formed by the union of the tibial and peroneal communicating ^in"°"^ '

branches of the internal and external popliteal nerves respectively

(pp. 129 and 130) ; the union usually taking place about the middle

of the leg. It runs with the external saphenous vein below the ending ;

outer ankle, and ends on the outer side of the foot and little toe

(p. 177). In this part it furnishes twigs to the skin of the lower branches.

part of the back of the leg, and large branches over the heel.

Cutaneous nerves of the external popliteal. In addition Branches of
to the peroneal communicating (fig. 71, ^), the external popliteal pjp^j[^^\
nerve gives off one or two lateral cutaneous offsets (p. 130) to the
outer side and fore part of the leg.

The small sciatic nerve (fig. 71, ^) perforates the fascia at the Termination
lower end of the popliteal space, and reaches to about the middle g^il^g"
of the leg with the external saphenous vein : it ramifies in the
integuments, and joins the external saphenous nerve.

188

Term illation
of internal
cutaneous.

Take away
the fat.

Deep fascia

continuity

and attach-
ments.

Take away
the fascia.

Muscles in
superticial
group.

DISSECTION OF THE LEG.

Offset of the internal cutaneous (fig. 71, ^). The posterior
branch of the internal cutaneous of the thigh (p. 141) extends to

the middle of the leg, and communi-
cates with the internal saphenous
nerve.

Dissection. The deep fascia will
he exposed by removal of the fat, and
the superficial vessels and nerves ma}
l)e either cut or turned aside.

The deep fascia on the posterior
aspect of the leg covers the muscles,
and sends a thick process l)etween the
deep and superficial groups. Al)ove,
it is continuous with the investing
membrane of the thigh, and receives
offsets from the tendons about the
knee ; and below, it joins the annular
ligaments. Internally, it is fixed to
the edge of the tibia : externally, it is
continued uninterruptedly from the
one aspect of the limb to the other ;
but from its deep surface an inter-
muscular septum is sent inwards
Ijetween the muscles of the back and
those of the outer side of the leg to be
attached to the outer border of the
fibula. Veins are transmitted through
it from the deep to the superficial
vessels.

Dissection. The fascia is to be
divided along the centre of the leg
as far as the heel, and is to be taken
from the surface of the gastrocnemius
muscle. By fixing with a stitch the
cut inner head of tbe gastrocnemius,
the fibres of the muscle will be more
easily cleaned.

Superficial Group of Muscles.
In the calf of the leg there are three

Fig. 71. — First View op the Back of the Leg (Illustrations
OF Dissections).

Muscles :
Gastrocnemius,
Soleus.

Semimembranosus.
Biceps.

Vessels :
Popliteal artery.
Internal saphenous vein.
External saphenous vein.

Nerves :

1. External popliteal.

2. Internal popliteal.

3. Tibial communicating.

4. Peroneal communicating.

5. External, or short, saphenous.

6. Small sciatic.

7. Internal saphenous.

8. Internal cutaneous.

I SUPERFICIAL GROUP OF MUSCLES,

muscles, gastrocnemius, soleus, and plantaiis, which extend the
i, ankle. The first two are large, giving rise to the prominence
on the surface, and end below \>y a
common tendon ; but the last is
inconsiderable in size, and chiefly
tendinous.

The GASTROCNEMIUS (fig.* 71, a),

the most superficial muscle, has two
distinct pieces or heads, which arise
from the lower end of the femur
(fig. 61, p. 158). The inner head of
origin is attached by a large tendon
to an impression at the upper asjject
of the inner condyle, behind the
insertion of the adductor magnus ;
and by short tendinous fibres to the
line above the condyle. The outer
head is attached by tendon to a pit
on the outer surface of the corre-
sponding condyle, above the attach-
ment of the popliteus muscle, and
to the posterior surface of the bone
immediately above the condyle. The
fleshy fibres of the two heads are
united along the middle line by a
narrow thin aponeurosis, and termi-
nate below with the soleus in the
common tendon of insertion.

One surface is covered by the
fascia. The other is in contact with
the soleus and plantaris, and with
the popliteal vessels and the internal
popliteal nerve. The heads, by which
the muscle arises, assist to form the
lateral boundaries of the popliteal
space, and are crossed by the tendons
of the hamstrings. The inner head
is larger, and descends lower than the

189

relations ;

Fig. 72. — Second View of the Back of the Leg (Illustrations
OP Dissections).

Muscles :

A. Grastrocnemius, cut.

B. Soleus.

c. Plantaris.

D. Seinimembranosus.

E. Semitendinosus.

F. Tendo AchiUis.

Vessels :
a. Popliteal artery.

b. Internal lower articular.

c. External lower articular.

d. Internal saphenous vein.

e. External saphenous vein.

Nerves :

1. External popliteal.

2. Internal popliteal.

3. Short saphenous, cut.

190

use with the
foot free,
and fixed ;

acting from
below.

Detach
gastrocne-
mius.

Soleus is
attached to
the hones of
the leg,

and joins
the tendon
below;

parts over

and under
it:

the foot

free,

and fixed ;

acting from
below.

Tendo

Achillis ;

extent.

and inser-
tion.

Plautaris :

origin

position of
the muscle ;

DISSECTION OF THE LEG.

outer. In the outer head a piece of nljro- cartilage or a sesamoid
bone may exist.

Action. When the foot is unsupported, the gastrocnemius extends
the ankle ; and when the toes rest on the ground, it raises the os
calcis and the weight of the body, as in standing on the toes, and
in progression.

Taking its fixed point at the os calcis, the muscle draws down the
femur so as to bend the knee-joint.

Dissection. To see the soleus, the gastrocnemius is to be
reflected by cutting across the remaining head (fig. 72), and the
vessels and nerves it receives. After the muscle has been thrown,
down, the soleus and plantaris must be cleaned.

The SOLEUS (fig. 72, b) is a large flat muscle, which is attached
to both bones of the leg. It arises from the head, and the upper
third of the posterior surface of the shaft of the fibula ; from the
oblique line across the tibia, and from the inner edge of this bon
as low as the middle (fig. 73) ; and between the bones from
aponeurotic arch over the large blood-vessels. Its fibres are directe
downwards to the common tendon.

The superficial surface of the soleus is in contact with the gastr*
cnemius ; and where the two touch they are aponeurotic. Beneat
the soleus lie the bones of the leg, the deep muscles, and the vessels :
and nerves.

Action. In its action on the foot the soleus, like the gastro-
cnemius, extends the ankle and points the toes when the foot is
free to move, and raises the heel if the toes rest on the ground.
By the sudden and powerful contraction of the fibres of both muscles
the common tendon is sometimes broken across.

If it acts from the os calcis, it will draw back the bones of the
leg into a vertical position over the foot, as the body is raised to the
erect posture after stooping.

Tendo Achillis (fig. 72, f). The common tendon of the gastro-
cnemius and soleus is one of the strongest in the body. About three
inches wide above, it commences at the middle of the leg, though
it receives fleshy fibres on its deep surface nearly to the lower
end : below, it is narrowed, and is inserted into the middle impression
on the posterior as^^ect of the tuberosity of the os calcis. A bursa
intervenes between it and the upper part of the tuberosity. The
tendon is close beneath the fascia ; and the external saphenous vein
and nerve are superficial to it at first, but afterwards lie along its
outer border.

The PLANTARIS (fig. 72, c) is remarkable in having the longest
tendon in the body, which takes the appearance of a riband when
it is stretched laterally. About three-quarters of an inch wide, the
muscle arises from the line above the outer condyle of the femur,
and from the posterior ligament of the knee-joint ; and the tendon
is inserted into the os calcis with, or by the side of, the tendo
Achillis, or into the fascia of the leg.

The belly of the muscle, about three inches in length, is concealed
by the gastrocnemius, but the tendon appears on the inner side of

DISSECTION OF THE DEEP MUSCLES. 191

the tendo Achillis about the middle of the leg. This little muscle
crosses the popliteal vessels, and lies on the soleiis.

Actio?!. It assists slightly the gastrocnemius in extending the use like
ankle if the foot is not fixed, and in bending the knee-joint if the f^u^"^"
foot is immovable.

Dissection (fig. 74). The soleus is now to be detached from Detach

soleus,

Semiineni branosus .

Soleus.

Biceps.

' — Peroiieuslongus.

Groove for tibialis posticus tendon.

Fig. 73.— The Tibia and Fibula from Behind.

the bones of the leg, and the vessels and nerves entering it are to be
divided ; but in raising it, the student should take care not to injure
the thin deep fascia and the vessels and nerves beneath. The super-
ficial muscles may l)e next removed by cutting through their tendons
near the os calcis ; and the bursa between the tendo Achillis and
the OS calcis should be opened.

The piece of fascia between the muscles of the superficial and and clean
deep groups is then to be cleaned ; and the integuments between J^cJ^^^^

192

DISSECTION OF THE LEG.

Deep part of 6
the fascia of
the leg.

Clean the
deep
muscles ;

dissect

Ijeroneal

artery.

Fig. 74.

the inner ankle and the heel are to
1)6 taken away to lay bare the annular
ligament, but a cutaneous nerve to
the sole of the foot, which pierces
the ligament, is to be preserved.

Deep part of the fascia. This inter-
muscular piece of the fascia of the
leg is fixed to the tibia and fil)ula,
and binds down the flexor muscles
of the deep group. In the upper
part of the leg it is thin and indis-
tinct ; but lower in the limb it is
much stronger, and is marked by
some transverse fibres near the mal-
leoli, which give it the appearance
and office of an annular ligament in
that situation. Inferiorly it joins
the internal annular ligament be-
tween the heel and the inner ankle.

Dissection. The deep layer of
muscles, the posterior tilnal nerve,
and the trunks and offsets of the pos-
terior tibial vessels will be laid bare
by the removal of the fascia and the
areolar tissue. A muscle between
the bones (tibialis posticus) is partly
concealed by an aponeurosis which
gives origin to the two lateral muscles
(flexor longus digitorum and flexor
hallucis) ; and it will not fully appear
until after its membranous covering
has been divided longitudinally and
reflected to the sides.

To prepare the peroneal artery

-Deep Dissection of the Back of the Leg (Illustrations
OF Dissections).

Muscles :

A. Popliteus.

B. Outer, and c, inner part of
soleus, cut.

T>. Tibialis ijosticus.

e. Flexor longus digitorum.

p. Flexor longus hallucis.

G. Peroneus longus.

H. Peroneus brevis.

I. Tendo Achillis.

Arteries :
a. Popliteal.

6. Inferior internal, and c, inferior
external articular.

d. Anterior tibial.

c. Posterior tibial, and /, a com-
municating branch to peroneal.

g. Peroneal.

h. Continuation of peroneal to
outer side of the foot.

Nerves :

1. Internal popliteal.

2. Muscular branch of posterior
tibial.

3. Posterior tibial.

4. Calcaneo-plantar.

DEEP MUSCLES OF THE BACK OF THE LEG. 193

evert and parti}' divide the flexor hallucis after that muscle has
been examined ; then define the branches from its lower part to
the front of the leg, the outer side of the foot and the one that
joins the posterior tibial artery.

Deep Group of Muscles (fig. 74). The deep muscles at the Four
back of the leg are four in number, viz., popliteus, flexor longus SilfdeeV'^
hallucis, flexor longus digitorum, and tibialis posticus. The first of group :
these is close to the knee-joint ; it crosses the bones, and is covered
by a special aponeurosis. The flexors lie on the bones, the one of position and
the great toe resting on the fibula, and that of the other toes on the
tibia. And the tibialis covers the interosseous membrane. With
the exception of the popliteus, all enter the sole of the foot ; and destination,
they have a fleshy part parallel to the bones of the leg, and a
tendinous part beneath the tarsus.

The POPLITEUS (fig. 74, a) arises by tendon, within the capsule Popliteus
of the knee-joint, from the front of an oblong depression on the ^thfn
outer surface of the external condyle of the femur (fig. 60, p. 157) ^ee-joint;
and within the capsule of the joint ; some fleshy fibres also arise
from the posterior ligament. The muscular fibres spread out, and inserted
are inserted into the tibia above the oblique line on the posterior ^^ * ** *
surface, as well as into the aponeurosis covering them (fig. 73).

The muscle rests on the tibia, and is covered by a fascia derived
in great part from the tendon of the semimembranosus muscle : on it lie
the popliteal vessels and nerve, and the gastrocnemius and plantaris.
Along the upper l)order are the lower internal articular vessels and parts
nerve of the knee; and the lower border corresponds with the *^°^"^ '
attachment of the soleus on the tibia. The tendon of origin will be
seen in the dissection of the ligaments of the knee-joint.

Action. The leg being free, the muscle bends the knee-joint, and use with
then rotates the tibia inwards. The popliteus is used especially in ^ ^* '
beginning the act of flexing the knee, as it produces the rotation special
inwards of the tibia (or outwards of the femur) without which that ^"^*^'^^°"-
movement cannot take place.

The FLEXOR LONGUS HALLUCIS (flexor longus pollicis pedis, fig. Flexor
74, f) arises below the soleus from the lower two-thirds of the pos- haJf^cis is
terior surface of the fibula (fig. 73) ; from the intermuscular septum attached to
between it and the peronei muscles, and from the aponeurosis over
the tibialis. Inferiorly the tendon of the muscle enters a groove in
the astragalus, and crosses the sole of the foot to its insertion into
the great toe.

Above, the muscle is covered by the soleus ; but below it is relations ;
superficial, and is in contact with the fascia. It lies on the fibula
and the lower end of the tibia, and conceals the peroneal vessels.
Along the inner side are the posterior tibial nerve and vessels ;
and contiguous to the outer margin, but separated by fascia, are
the peronei muscles.

Action. The foot being unsupported, the flexor bends the last use, the
phalanx of the great toe, and then extends the ankle. ^^^"^^

The foot resting on the ground, the muscle raises the heel ; and and fixed,
it draws the fibula backwards as the body rises from stooping.

D.A, o

194

DISSECTION OF THE LEG.

Flexor
loiigus
digitorum :

origin ;

enters

annular

ligament

part is
supei-flcial
below
soleus ;

use, with
foot free,

and fixed.

Tibialis
posticus :

origin ;

insertion

muscles and
vessels in
relation
with it ;

use, with
foot free,

and fixed;
in standing,

in rising up.

Aponeurosis
over the
muscle.

The FLEXOR LONGUS DIGITORUM (flexor perforans, fig. 74, e)
arises from the inner division of the posterior surface of the til>ia
(fig. 73), extending from the attachment of the solens to about three
inches from the lower extremity, and from the aponeurosis cover-
ing the til)ialis posticus. Its tendon enters a compartment in the
annular ligament, which is external to the sheath of the tibialis ;
and it divides in the sole of the foot into tendons for the last
phalanges of the four outer toes.

The muscle is narrow and pointed al>ove, where it is placed
beneath the soleus ; but in the lower half it is in contact with the
fascia, and the posterior tibial vessels and nerve lie on it. The
deep surface rests on the tibia and the tibialis posticus.

Action. The muscle bends the farthest phalangeal joints of the
four smaller toes, and then extends the ankle.

If the toes are in contact with the ground, the flexor helps to
raise the heel in walking ; and to move back the tibia in the act of
rising from stooping.

The TIBIALIS POSTICUS (fig. 74, d) occupies the interval between
the bones of the leg, but it crosses over the tibia below to reach the
inner side of the foot. The muscle arises (fig. 73 and fig. 68,
p. 179) from the interosseous membrane, except about one inch
below, from an impression along the outer part of the posterior
surface of the tibia extending from the external tuberosity to the
middle of the bone, from the inner surface of the shaft of the fibula,
and slightly from the aponeurosis covering it. In the lower part
of the leg the muscle is directed beneath the flexor digitorum ; and
its tendon, entering the inner space in the annular ligament, reaches
the inner side of the foot to be inserted into the navicular and
other bones, as will be seen later (p. 212).

The tibialis is concealed by the aponeurosis before mentioned,
and is overlapped by the neighbouring muscles ; but in the lower
part of the leg it is placed between the tibia and the long flexor of
the toes. On the muscle are the posterior tibial vessels and nerve.
The upper end presents two pointed processes of attachment — that
to the tibia being the higher — and between them the anterior tibial
vessels are directed forwards.

Action. Its action on the movable foot is to depress the fore
part and outer side, and carry the toes inwards, producing the
movement in the tarsal joints known as inversion (p. 225), and to
extend the ankle-joint. The toes resting on the ground, it will aid
the muscles of the calf in raising the heel in the progression of the
body.

In standing, the muscle can raise the inner border of the foot
with the tibialis anticus, so as to throw the weight of the body on
the outer edge.

As the body rises from stooping, the tibialis draws back the bones
of the leg, with the soleus.

The aponeurosis covering the tibialis is attached externally to the
inner border of the fibula ; but internally it joins the flexor longus
digitorum without being attached to bone : it may be regarded as

POSTERIOR TIBIAL ARTERY. 195

constituting a fibular origin of that muscle. Fibres of the flexor
longus hallucis arise from one surface of the membrane, and of the
tilualis posticus from the other.

The POSTERIOR TIBIAL ARTERY (fig. 74, e) is one of the vessels Posterior
resulting from the bifurcation of the popliteal trunk (p. 126). It altery:
extends from the lower l)order of the popliteus muscle to the lower extent ;
edge of the internal annular ligament, where it ends in internal and
e:demal jplantar branches for the sole of the foot.

At its origin the artery lies midway between the tibia and fibula course;
l)ut as it approaches the lower part of the leg it gradually inclines
inwards ; and at its termination it is placed behind the tilna, in the
centre of the hollow l)etween the heel and the inner ankle.

For the upper two-thirds of the leg the vessel is concealed by two parts cover-
muscles of the calf, viz., gastrocnemius and soleus ; but in the and^be*owf
lower third, as it lies between the tendo Achillis and the inner
edge of the tibia, it is covered only by the integuments and the
deep fascia. At its termination it is placed beneath the annular
ligament. For its upper half the trunk lies over the tibialis
posticus, Ijut afterwards on the flexor digitorum, and on the lower parts be-
end of the tibia and the ankle-joint. On the outer side is the"^*^'*'
flexor hallucis.

Under the annular ligament, the artery is placed between the between
tendons of the common flexor of the digits and the special flexor of ankle"*^
the great toe.

Yen £6 comites closely surround the vessel. The posterior tibial veins;
nerve is at first internal to the art-ery ; but after the origin of the nerve ;
peroneal artery it crosses to the outer side, and retains that position
throughout.

This artery supplies branches to the muscles and the tibia, and a branches :—
large peroneal trunk to the outer side of the leg.

a. Muscular hranclies enter the deep layer of muscles, and the Muscular,
soleus ; and an ofl'set from the branch to the soleus pierces the
attachment of that muscle to the tibia, and ascends to the knee-joint.

h. The medullary artery of the tibia arises near the beginning of Medullary
the trunk ; penetrating the tibialis, it enters the canal on the posterior
surface of the bone, and ramifies in the interior.

c. Cutaneous offsets appear through the fascia in the lower half Cutaneous,
of the leg.

d. One or two small internal malleolar branches ramify over the internal

11 1 malleolar,

inner malleolus.

e. A communicating branch arises opposite the lower end of the Communi-
tibia, and passes outwards beneath the flexor longus hallucis, to ^^ '"^'
unite in an arch with a corresponding ofl'set of the peroneal artery.
Sometimes there is a second loop between these vessels superficial to

the flexor hallucis (fig. 74,/).

Peculiarities. If the posterior tibial artery is smaller than usual, or size of
absent, its deficiencies in the foot will be supplied by a large communicating tibial may
branch from the peroneal artery, which, in these cases, is directed inwards '^'^^•
at the lower end of the tibia, and either joins the small tibial vessel, or runs
alone to the sole of the foot.

O 2

196

DISSECTION OF THE LEG.

Peroneal
artery :

courses
along fibula,

Dissection. The peroneal artery will now be completely exposed
by cutting away the flexor longus lialliicis as far as may Ije
necessary.

The PERONp]AL ARTERY (fig. 74, (j) is often as large as the pos-
terior tibial, and arises from that vessel about one inch from the
beginning. It takes the fibula as its guide, and lying close to that
bone in a fibrous canal between the origins of the flexor longus
hallucis and tibialis posticus, reaches the lower part of the inter-
osseous membrane. At this spot it sends forwards a branch to the
front of the leg {anterior peroneal) ; and, as the posterior peroneal^ is
directed onwards l)ehind the articulation between the tibia and
fibula to the outer side of the heel (A), where it terminates in
branches, which anastomose with offsets of the tarsal and external
plantar arteries. Two companion veins surround the artery ; and
the nerve to the flexor hallucis lies on it generally.

Branches. Besides the anterior peroneal, it furnishes muscular,
medullary, and communicating offsets.

a. Muscular branches are distributed to the soleus, tibialis
posticus, and flexor hallucis ; and some turn round the fibula to the
long and short peroneal muscles, lying in grooves in the bone.

6. The medullary artery is smaller than that to the tibia, and is
transmitted through the tibialis posticus to an aperture about the
middle of the fibula.

c. The anterior pteroneal branch passes forward through an open-
ing below the interosseous membrane, and is continued to the
dorsum and outer part of the foot (fig. 70, p. 183) ; on the front of
the leg and foot it anastomoses with the external malleolar and tarsal
branches of the anterior tibial artery, and has already been exposed
(p. 182).

d. A communicating offset near the ankle joins in an arch with a
similar branch of the posterior tibial.

Peculiarities. The anterior branch of the peroneal may take the place of
the anterior tibial artery on the dorsum of the foot.

A compensating principle may be observed amongst the arteries of the foot,
as in those of the hand, by which the deficiency in one is supplied by an
enlarged offset of another.

Posterior The POSTERIOR TIBIAL VEINS begin at the inner side of the foot

tibial veins: ],y ^j^g union of the plantar vense comites : they ascend one on each

side of the artery, and unite with the anterior tibial at the lower

border of the popliteus to form the large popliteal vein. They

receive the peroneal veins, and branches corresponding with the

offsets of the artery : branches connect them with the saj)henous

veins.

Posterior The POSTERIOR TIBIAL NERVE (fig. 74, ^), a continuation of the

tibial nerve : jj^^gj.jja^] popliteal (p. 129), reaches like the artery from the lower

border of the popliteus muscle to the interval between the os calcis

extent and the inner malleolus. While Ijeneath the annular ligament, or

somewhat higher than it, the nerve divides into the internal and

external i^lantar branches of the foot.

beneath

flexor

hallucis

termination

veins and
nerve ;

branches :-

Muscular.

Medullary
to fibula.

Anterior
peroneal

to front of
foot.

Communi-
eating.

Substitu-
tions.

and rela-
tions:

Its relations to surrounding muscles are the same as those of the

INTERNAL ANNULAR LIGAMENT. 197

artery ; but its i)ositioii to the vessel changes, for it lies on the
inner side above the origin of the peroneal offset, but thence to the
termination, on the outer side. Its branches are muscular and branches
cutaneous.

3Iuscular branches are furnished to the two long Hexors, the to muscles.
til»ialis posticus, and the soleus. There is an offset for each of the
muscles ; and they may arise either sei>arately along the trunk, or
together from the upper end of the nerve. The branch to the
tibialis is the largest ; and that to the flexor halhicis lies on the
peroneal artery.

A cutanecms nerve of the sole of the foot (calcaneo-plantar, fig. 74, *) and to skin
begins above the ankle, and piercing the internal annular ligament sole.
a.s two or more parts, ends in the integuments of the inner and
under-parts of the heel : this nerve will be followed to its termina-
tion in the dissection of the foot.

The INTERNAL ANNULAR LIGAMENT stretches between the heel and internal
tlie inner ankle, and serves to confine the tendons of the deep layer ^'^^ament •
of muscles of the foot and toes. Attached by a narrow part to the
internal malleolus, the fibres diverge, and are inserted into the os
alcis. The upper border is continuous with the fascia of the attach-
ing ; and the lower gives attachment to the abductor hallucis ™^"*^'*
muscle of the foot.

Beneath it are sheaths for the tendons. The innermost sheath sheaths :
encloses the tibialis posticus, lodged in a groove on the back of the their
malleolus. Immediately outside this is another space for the flexor P^^'^'°"
digitorum. And about three-quarters of an inch nearer the os calcis
is the flexor hallucis, resting in a groove in the astragalus. Each
sheath is lined by a synovial membrane.

Between the tendons of the two flexors of the digits are placed
the posterior tibial vessels and nerve.

Sectiox VI.
SOLE OF THE FOOT.

Position. The foot is to be placed over a block of moderate thick- Position of
ness with the sole towards the dissector ; and the part is to be made ^^ •
tense by fixing the heel with hooks, and l)y separating and fastening
apart the toes.

Dissection. The skin is to be raised in two flaps, inner and outer, ^}^^ tt»e
by means of one incision along the centre of the sole from the heel
to the front and l)y an incision across the foot at the root of the
toes. Afterwards the skin is to l>e removed from each toe, and the
digital vessels and nerves on the sides are to be dissected out at
the same time.

In the fat near the heel the student should follow out the calcaneo- and dissect
plantar nerve (shown at the upper part of fig. 75, p. 200) ; and he nen-er"""
may trace out, at a little distance from each border of the foot,
some small branches of the plantar nerves and arteries.

198

DISSECTION OF THE FOOT.

Subcuta-
neous fat.

Lay bare
the plantar
fascia,

and the
digital ves-
sels and
nerves ;

define the
ligament of
the toes.

Plantar
fascia :

division
into parts.

Central part

divides
into five
pieces :

termination
of the
pieces.

Inner piece
of the fascia.

Outer piece,

Expose the
septa.

Two inter-
muscular
septa.

The suhcataneous fat is very aljimdaiit, and forms a thick cushion
over the parts that press most on the ground in standing, viz., over
the OS calcis, and the metatarso-phalangeal articulations.

Dissection. The fat should now he, removed, and the plantar
fascia laid bare. Beginning the dissection near the heel, follow
forwards the fascia towards the toes, to each of which a process is
to be traced. In the intervals between these processes the digital
nerves and arteries will be detected amongst much fatty and fibrous
tissues ; but the vessels and nerves to the inner side of the great toe
and outer side of the little toe pierce the fascia farther back than
the rest.

The student is next to define a fibrous l^and (superficial transverse
ligament) across the roots of toes, over the digital vessels and nerves ;
and when this has Ijeen displayed, he may remove the superficial
fascia from the toes to see the sheaths of the tendons.

Plantar fascia. The special fascia of the sole of the foot is of a
pearly white colour and great strength, and sends septa between the
muscles. Its thickness varies in different parts of the foot ; and
from this circumstance, and the existence of longitudinal depressions
over the two chief intermuscular septa, the fascia is divided into a
central and two lateral pieces.

The central -part, which, is much the thickest, is pointed at its
attachment to the os calcis, but widens and becomes thinner as it
extends forwards. A slight depression, corresponding with an
intermuscular septum, marks its limit on each side ; and opposite
the heads of the metatarsal Ijones it divides into five processes,
which send fibres to the integuments near the web of the foot, and
are continued onwards to the toes, one to each. Where the pieces
separate from each other, the digital vessels and nerves and the
lumbricales muscles become superficial, and are arched over by
transverse fibres.

If one of the digital processes be divided longitudinally, and
its parts reflected to the sides, it will be seen to join the sheath
of the flexor tendons, and to be fixed laterally into the margins
of the metatarsal bone, and into the transverse metatarsal
ligament.

The lateral -pieces of the fascia are thinner than the central one.
On the inner margin of the foot the fascia has but little strength,
and is continued to the dorsum ; but on the outer side it presents
a strong band, which extends between the outer tubercle of the os
calcis and the base of the fifth metatarsal bone.

Dissection. To examine the septa, a longitudinal incision should
be made along the middle of the foot through the central piece of
the fascia, and a transverse one near the calcaneum. On detaching
the fascia from the subjacent flexor brevis digitorum, by carrying
the scalpel from before backwards, the septal processes will appear
on the sides of that muscle.

The intermuscular septa pass deeply on each side of the flexor
brevis digitorum, and a piece of fascia reaches across the foot from
one septum to the other, beneath that flexor, so as to isolate it.

FIRST LAYER OF MUSCLES. 199

The inner septum separates tlie short flexor from the abductor
hallucis ; and the outer, from the abductor minimi digiti.

The superficial transverse ligament crosses the roots of the toes, Transverse
and is contained in the skin forming the rudimentary web of the ['^e toes* °^
foot. It is attached at the ends to the sheath of the flexor tendons
of the great and little toes, and is coimected with the sheaths of the
others as it lies over them. Beneath it, the digital nerves and
vessels issue.

The sheaths of the flexor tendons (fig. 77, G, p. 203) on the toes Sheaths of
are similar to those of the fingers, though not so distinct, and ^^^^ *'""
serve to confine the tendons against the grooved bones. The sheath
is weak opposite the articulations between the phalanges, but is
strong opposite the centre of both the metatarsal and the next
phalanx. Each is hibricated by a synovial membrane, and contains
the tendons of the long and short flexor muscles.

Dissection (fig. 75). In the sole of the foot the muscles are Dissect first
numerous, and have been arranged in four layei*s. To prepare the muscles,
first layer, all the fascia must be taken away ; but this dissection
must be made with some care, lest the digital nerves and vessels,
which become superficial to the central muscle towards the toes,
should be injured.

The tendons of the short flexor muscle are to be followed to the
toes, and one or more of the sheaths in which they are contained

luld be opened.

First Layer of Muscles. In this layer are three muscles, viz., Muscles iu
tlie flexor brevis digitorum, the abductor hallucis, and abductor laygr.^^
minimi digiti. The short flexor of the toes lies in the centre of the
foot ; and each of the others is in a line with the toe on which
it acts.

The ABDUCTOR HALLUCIS (fig. 75, a), the most internal muscle of Abductor
the superficial layer, takes origin from the inner side of the larger ^^^^'^^^^ •
tubercle on the under-surface of the os calcis (fig. 76), from the°"^'^'
plantar fascia, from the lower border of the internal annular liga-
ment, and from the internal intermuscular septum. In front, the
muscle ends in a tendon, which is joined by fibres of the short
flexor, and is inserted into the inner side of the base of the first insertion ;
phalanx of the great toe.

The cutaneous surface of the muscle is in contact with the relations ;
l)lantar fascia ; and the other touches the tendons of the tibial
muscles, the plantar vessels and nerves, and the tendons of the
long flexors of the toes, with the accessorius muscle.

Action. This abductor acts chiefly as a flexor of the metatarso- use, as
phalangeal joint of the great toe, but it will slightly abduct that abductor,
toe from the others.

The FLEXOR BREVIS DIGITORUM (fleXOr perforatus, fig. 75, b) Flexor

arises posteriorly by a pointed process from the fore part of the torum ^'^'
larger tubercle of the os calcis (fig. 76), from the overlying plantar
fascia for two inches and the septa. About the centre of the foot
the muscle divides into four slips, which become tendinous and are
directed forwards superficial to the tendons of the long flexor to

200

DISSECTION OF THE FOOT.

diAides into enter the sheaths of the four smaller toes, where they are inserted

fnnr tn^/^^ liito the middle phalanges. In the sheath on the toe the tendon lies

at first (in this position of the foot) on the long flexor ; opposite

the centre of the first phalanx it is slit for the passage of the long

fom- toes ;

<<\^^

\l-

Internal plantar nerve,
Internal plantar artery.

Kxt^nial plantar artery.
Ixtcrnal ]ilautar nerve.

Fig. 75.— First View op the Sole op the Foot (Illustrations
OP Dissections).

Muscles :

A. Abductor hallucis.

B. Flexor brevis digitoruni.
c. Abductor minimi digiti.

D. Transverse ligament of tbe toes.

Arteries:

a. External plantar.

b. Internal plantar.

1. Internal plantar, with its four
branches.

2, 3, 4 and 5, for three toes and
a half.

6. External plantar nerve, with two
digital branches.

7 and 8, for one toe and a half.

Insertion

relations ;

and use.

tendon, and it is attached liy two processes to the sides of the middle
phalanx.

The short flexor of the toes is contained in a sheath of the plantar
fascia ; and it conceals the tendon of the long flexor of the toes, the
flexor accessorius, and the external plantar vessels and nerve.

Action. It bends the first and second phalangeal joints of the
four smaller toes, like the flexor sublimis in the upper liml), and
approximates the toes at same time.

ABDUCTOR MINIMI DIGITI.

201

The ABDUCTOR MINIMI DIGITI (fig. 75, c) has a wide onVi^ AMuctor of
behind from the small outer tubercle of the os calcis, from thetol:'
adjacent part of the inner tubercle, extending inwards beneath
the flexor brevis digitorum (fig. 76), from the outer band of the
plantar fascia and from the external intermuscular septum. It ends f^J^j*^*^

Tendo achillis
Flexor brevis digitoi-um

Abductor minimi digiti.

f Imierliead.
Accessorius -

I Outer head.

Tibialis posticus
expansion.

Flexor brevis liallucis.

Peroneus brevis.

Flexor brevis minimi
digit

'lautar int«rossei

Flexor brevis minimi
digiti.

Flexor longns digitorum.

Plantaris.

Abductor hallucis.

Tibialis posticus
(exjmnsions indicated
by lines).

Tibialis anticus.

Peroneus longus.

Adductor obliquus
hallucis (encircled by
ring).

Dorsal interossei.

Adductor transversus

hallucis.
Interossei.

Flexor brevis digitorum.
Fig. 76. — Mcsgular Attachmekts on Plantar Aspect of Foot

anteriorly in a tendon which is inserted into the outer side of the
base of the first phalanx of the little toe.

The muscle lies along the outer border of the foot, and conceals relations ;
the flexor accessoriiLs, and the tendon of the peroneus longiLs. On
its inner side are the external plantar vessels and nerves. Some-
times a part of the muscle is fixed into the projection of the fifth
metatarsal bone.

Action. Though it can abduct the little toe from the others, as "seas^
the name signifies, its chief use is to bend the metatarso-phalangeal

joint.

abductor
and flexor.

202

DISSECTION OF THE FOOT.

Dissect the
next

muscular
layer,

and plantar
vessels and

Two plantar
arteries :

inner and
outer.

Internal
small ;

course and
ending.

Branches to
muscles ;

and super-
ficial digital;

first,
second,
third,
fourth.

External
artery has
a curved
course ;

partly
superficial,

partly deep.

Superficial
part :

relations-

Dissection (fig. 77). To bring into view the second layer of
muscles and the plantar vessels and nerves, the muscles already
examined must be reflected. Cut through the flexor brevis digi-
toruni at the os calcis, and as it is raised, notice a branch of
nerve and artery to it. Divide the abductor minimi digiti near
its origin, and in turning it to the outer side of the foot, seek its
nerve and vessel close to the calcaneum. The abductor hallucis
can be drawn aside if it is necessary, but at present it may remain
uncut.

Next, the internal plantar vessels and nerve are to be followed
forwards to their termination, and backwards to their origin ; and
the external plantar vessels and nerve, the tendons of the long
flexors of the toes, the accessory muscle, and the small lumbricales,
should be freed from fat.

The Plantar Arteries (fig. 77) are the terminal branches of
the posterior tibial trunk, and supply digital offsets to the toes.
They are two in number, and are named external and internal
from their relative position in the sole of the foot : the external is
the larger, and forms the plantar arch.

The INTERNAL PLANTAR ARTERY (a) is inconsiderable in size,
and accompanies the internal plantar nerve, under cover of the
abductor hallucis, as far as the middle of the foot, where it ends
in four superficial digital branches.

Branches. The artery furnishes muscular branches, ' like the
nerve, to the abductor hallucis, flexor brevis digitorum, and the
flexor brevis hallucis. Its digital branches accompany the digital
nerves of the internal plantar (fig. 75), and are thus disposed : —

The first is distributed to the inner side of the foot and great
toe ; the second is directed to the first interdigital space ; the third
to the second space ; and the fourth to the third space. At the
root of the toes the last three join the deeper digital arteries in
those spaces.

The EXTERNAL PLANTAR ARTERY (h) takes an arched course in
the foot, with the concavity of the arch turned inwards. The vessel
first passes outwards across the sole towards the base of the fifth
metatarsal bone, and then turns obliquely inwards towards the root
of the great toe, so that it crosses the foot twice. In the first half
of its extent, viz., as far as the base of the metatarsal bone of the
little toe, the artery is comparatively superficial ; in the other
half, between the little and the great toe, it lies deeply in the
foot, and forms the plantar arch.

Only the first part of the artery is now laid bare ; the remaining
portion, supplying the digital branches, will be noticed after the
examination of the third layer of muscles (p. 207).

As far as the metatarsal bone of the little toe, the vessel is con-
cealed by the abductor hallucis and the flexor l)revis digitorum ;
but for a short distance near its termination it lies in the interval
between the last muscle and the abductor minimi digiti. It rests
on the OS calcis and flexor accessorius ; and it is accompanied by
venae comites and the external plantar nerve.

EXTERNAL PLANTAR ARTERY.

203

Branches. From the superficial part of the artery two or three ^ranches
:nternal calcaneal branches arise. They perforate the origin of the

Fig,

77.__Second View of the Sole op the Foot (Illustrations
OF Dissections).

minimi

Arteries :

a. Internal plantar.
h. External plantar.
c. Branch to abductor
digiti.

(I. Branch to outer side of little toe.

Nerves :

1. internal plantar.

2. External plantar.

3. Branch to abductor minimi

tligiti. . , n .

4. Branch to flexor brevis hallucis.

Miiscles :

A. Accessorius.

B. Tendon of flexor longus digi-
torum. .

c. Tender of flexor longus hallucis.

D. marks the four lumbricales
muscles, but the letters arc put on
the tendons of the flexor perforans.

E. Tendon of flexor brevis digi-
torum.

F. Tendon of flexor longus digi-
torum.

G. Sheath of flexor tendons.
H. Tendon of peroneus longus.

abductor hallucis, and ramify over the heel, anastomosing with the
terminal branches of the peroneal artery. , . -, . ^ ,

Offsets are also furnished to the muscles between which it lies ; tomuscles.
and others turn round the outer border of foot to anastomose with side of foot
the tarsal and metatarsal arteries.

20-t

DISSECTION OF THE FOOT.

Plantar
nerves also
two.

Internal
nerve to
three toes
and a half ;

muscular
branches ;

digital
nerves are
divided, ex-
cept first,

and give

muscular

branches.

cutaneous
and articu-
lar offsets.

External
plantar to
one toe and
a half ;

has super-
ficial and
deep parts ;

branches to
muscles :

two digital
branches,

one single,
one divided.

Distribution
like others.

The Plantar Nerves (fig. 77) are derived from the bifurcatioi
of the posterior tibial trunk behind the inner ankle. They are t\v<
in number, and accompany the plantar arteries ; but the large: I
nerve lies with the smaller l)lood-vessel.

The INTERNAL PLANTAR NERVE (^) courses between the sliori
flexor of the toes and the abductor hallucis, and giving but few
muscular offsets, divides into four digital branches (fig. 75, ^, ^, "*,
for the supply of both sides of the inner three toes, and half tht
fourth ; it resembles thus the median nerve of the hand in the
distribution of its branches.

Muscular offsets are given by the trunk to the flexor bre\'i&
digitorum and the abductor hallucis ; and a few superficial tuiys
perforate the fascia.

The four digital nerves have a numerical designation, and the
first is nearest the inner border of the foot. The branch (') to the
inner side of the great toe is undivided, but the others are bifurcat
at the cleft between the toes.

Muscular branches are furnished by two of these nerves before
they reach the toes ; thus, the first supplies the flexor l)revis
hallucis ; and the second gives a branch to the innermost lumbrical
muscle.

Digital nerves on the toes. Each of the outer three nerves, being
divided at the cleft between the toes, supplies the contiguous sides
of two toes, while the first belongs altogether to the inner side of
the great toe ; all give oftsets to the integuments, and the cutis
beneath the nail, and articular filaments are distributed to the
joints as in the fingers.

The EXTERNAL PLANTAR NERVE (fig. 77,"^) is speiit chiefly in
the deep muscles of the sole of the foot, but it furnishes digital
nerves to both sides of the little toe, and the outer side of the
fourth. It corresponds in its distribution Avith the ulnar nerve in
the hand.

It has the same course as the external plantar artery, and divides
at the outer margin of the flexor brevis digitorum into a superficial
and a deep i)ortion ; — the former gives origin to the two digital
nerves ; but the latter accompanies the arch of the plantar artery
into the foot, and will be dissected afterwards (p. 210).

While the external plantar nerve is concealed by the short flexor
of the toes, it gives muscular hranches to the al)ductor minimi digiti
and the flexor accessorius. '

The digital h'anches of the external plantar nerve (fig. 75) are
two. One (7) is undivided and is distrilnited to the outer side of
the little toe, giving off"sets to the flexor brevis minimi digiti,
and oftentimes to the interosseous muscles of the fourth space.
The other {^) bifurcates at the cleft between the outer two toes,
supplying their collateral surfaces, and communicates in the foot
with the last digital branch of the internal plantar nerve.

On the sides of the toes the digital nerves have the same dis-
triljution as those from the other plantar trunk, and end like them
in a tuft of fine branches at the extremity of the digit.

SECOND LAYER OF MUSCLES. 205

■^ Dissection (fig. 77). To complete the preparation of the second Lay bare
^ aver of muscles, the abductor hallucis should be detached from the i^ye?of
'"i )S calcis and turned inwards. The internal plantar nerve and muscles.

irtery, and the superficial portion of the external i)lantar nerve,

1 ire to be cut across and thrown forwards; but the external plantar

^ irtery and the nerve with it are not to be injured. All the fat,

' ind the loose tissue and fascia, are then to be taken away near the

toes.

Second Layer of Muscles (fig. 77). In this layer are the Muscles of
tendons of the two tlexor muscles at the back of the leg, ^-iz., flexor ^ye^
longus digitorum and flexor longus hallucis, which cross one another.
Connected with the former, soon after it enters the foot, is an
accessory muscle ; and at its division into tendons for the four
outer toes the fleshy Imubricales are added to it.

Tlie tendon of the flexor longus digitorum (fig. 77, b), enters Tendon of
the foot beneath the annular ligament, and there lies on the internal oTto^^^**'
lateral ligament of the ankle-joint. In the foot it is directed
obliquely towards the centre, where it is joined by the accessorius divides into
muscle and a slip from the tendon of the flexor longus hallucis, and ^^^ >
divides into tendons for the four outer toes.

Each tendon enters the sheath of the toe ^\'ith and beneath a these pierce
tendon from the flexor brevis (e). About the centre of the first tend^ous^^
phalanx the tendon of the long flexor (f) passes through the other,
and goes onwards to be inserted into the base of the imgual phalanx.
Uniting the flexor tendons with the two nearest phalanges of the
toes are short s\Tiovial folds, one to each, as in the hand ; and the
description of the sheatlis on p. 75 should be refeiTed to. to tendons;

Action. It flexes the last phalangeal joint, and combines with use.
the short flexor in bending the first and second joints. If it acted
by itself it would tend to bring the toes somewhat inwards, in con-
secjuence of its oblique position in the foot.

The LUMBRICALES (fig. 77, d) are fom- small muscles Ijetween Four lum-
the tendons of the flexor longus digitorum. Each arises from two ^^'^^aies :
tendons with the exception of the most internal, which is connected J^*fonK°^°*
only with the inner side of the tendon to the second toe. Becoming flexor
tendinous, they pass upwards on the tibial side of the four outer and exten-
toes, and are inserted into the expansion of the extensor tendons on ^°^ en ons.
the dorsum of the first phalanx ; but they often end partially in an
attachment to the side of the first phalanx. The muscles decrease
in size from the inner to the outer side of the foot.

Action. These small muscles assist in flexing the metatarso-
phalangeal joints ; and through their union with the long extensor
tendon they may aid that muscle in straightening the two inter-
phalangeal joints.

The ACCESSORIUS muscle (fig. 77, a) has two heads of origin : — Flexor ac-
One is mostly tendinous, and is attached to the outer surface of the ^^^^°"^
OS calcis, and to the long plantar ligament ; the other is large and
fleshy, and springs from the inner concave surface of the lx>ne
(fig. 76, p. 201). The fibres end in aponeurotic bands, which join i^-jjjfl^*^
the tendon of the flexor longus digitorum alK)ut the centre of the longus ;

relations :

Insertion
of tendon
of flexor
hallucis ;

relations ;

use on first

and other
toes.

Dissect
third layer
of muscles.

Muscles of
third layer.

Flexor
brevis
hallucis

origin ;

insertion

DISSECTION OF THE FOOT.

foot, and contribute slips to the pieces of that tendon going to th
second, third and fourth digits.

The muscle may he bifurcated behind, and the heads of origii
separated by the long plantar ligament. On it lie the externa
plantar vessels and nerA'e ; and the muscles of the first layt-
conceal it.

Action. By means of its offsets to the tendons of certain digit
the muscle hel23s to bend the toes ; and from its position on tht
outer side of, and behind the long flexor to which it is united, i1
will oppose the inward pull of that muscle, and enable it to bend
the toes more directly backwards.

The tendon of the flexor loxgus hallucis (fig. 77, c) is
deeper in the sole of the foot than the flexor longus digitorum :
taking a straight course to the root of the great toe, it enters the
digital sheath, to be inserted into the base of the last plialanx.
It is united to the long flexor tendon by a strong tendinous process,
which, joined by l)ands of the accessorius, is continued into the
pieces of that tendon belonging to the second and third toes.

Beneath the internal annular ligament this tendon lies in a groove
on the back of the astragalus : in the foot it first occupies a similar
groove on the under-surface of the sustentaculum tali, and then lies
over the flexor brevis hallucis.

Action. For the action of this muscle on the great toe, see
p. 193. Through the slip that it gives to the tendons of the common
flexor going to the second and third toes, it will help to bend those
digits with the great toe.

Dissection (fig. 78, p. 208). For the dissection of the third
layer of muscles, the accessorius and the tendons of the long flexors
are to be cut through near the calcaneum, and turned towards the
toes. While raising the tendons, the external plantar nerve and
artery are not to be interfered with ; and small nerves and vessels
to the outer three lumbricales are to be looked for. Afterwards the
areolar tissue is to be taken from the muscles now brought into view.

Third Layer of Muscles (fig. 78). Only the short muscles
of the great and little toes enter into this layer. On the metatarsal
bone of the great toe the flexor brevis hallucis lies, and external to
this is the adductor obliquus hallucis ; on the metatarsal bone of
the little toe is placed the flexor brevis minimi digiti. Crossing
the heads of the metatarsal bones is the adductor transversus
hallucis.

The fleshy masses between the adductor obliquus and the short
flexor of the little toe consists of the interosseous muscles of the
next layer.

The flexor brevis hallucis (flexor brevis pollicis pedis,
fig. 78, a) arises behind by two tendinous slips, one of which is
fixed to the inner side of the cuboid bone (fig. 76, p. 201), while
the other is prolonged from the tendon of the tiljialis ^^osticus.
Near the front of the first metatarsal bone the fleshy belly divides
into two heads, which are inserted into the sides of the base of
the metatarsal phalanx.

ADDUCTOK OBLIQUUS HALLUCI8. 207

Resting on the muscle at one part, and in the interval between relations ;
the heads at another, is the tendon of the flexor longus hallucis.
The inner head joins the abductor, and the outer is united with the
^ adductor hallucis. A sesamoid bone is developed in the tendon
connected with each head.

Action. By its attachment to the first phalanx it flexes the use.
metatarso-phalangeal joint of the big toe.

The ADDUCTOR OBLIQCUS HALLUCIS (adductor pollicis pedis, fig. Adductor

78, b), which is larger than the preceding muscle, arises from the halluS
sheath of the tendon of the peroneus longus, from the ridge on the origin ;
cuboid, and from the bases of the third and fourth metatarsal
bones (tig. 76). Anteriorly the muscle is united with the outer insertion ;
head of the short flexor, and is inserted with it into the base of the
first phalanx of the great toe.

To the inner side is the flexor brevis ; and beneath the outer relations;
border the external plantar vessels and nerves are directed inwards.

Action. Its first action will be to adduct the great toe to the use.
othei^s, and it will help afterwards in bending the metatarso-
phalangeal joint of the toe.

The ADDUCTOR TRANSVERSUS HALLUCIS (traUSVerSUS pedis, fig. Adductor

78, d) arises by fleshy bundles from the capsules of the meta- hallucis:
tarso-phalangeal articulations of the three outer toes (fig. 76) origin;
(frequently not from the little toe), and from the transverse meta-
tarsal ligament. Its insertion into the great toe is united with that insertion ;
of the adductor obliquus.

The cutaneous surface is covered by the tendons and the nerves relations;
of the toes ; and the opposite surface is in contact with the inter-
osseous muscles and the digital vessels.

Action. It will adduct the great toe to the others, and then «se on the
approximate the remaining toes.

The FLEXOR BREVIS MIJSIMI DIGITI (fig. 78, C) is a narrow Flexor

muscle resembling one of the interossei. Arising behind from the ^igm I
base of the fifth metatarsal l)one and the sheath of the peroneus origin;
longus, it blends in front with the inferior ligament of the metatarso-
phalangeal articulation, and is inserted into the base of the first insertion ;
phalanx of the toe.

Actio7i. Firstly, it bends the metatarso-phalangeal joint, and use.
next it draws down and adducts the fifth metatarsal bone.

Dissection (fig. 79). In order that the deep vessels and nerves Dissect the

• d.66p VGSS61

may be seen, the flexor brevis and adductor obliquus hallucis are to and nerves,
be cut through behind, and thrown towards the toes ; but the nerve
supplying the latter is to be preserved. Beneath the adductor lie
the plantar arch and the external plantar nerve with their branches ;
and through the first interosseous space the dorsal artery of the foot
enters the sole. All these vessels and nerves, with their branches,
require careful cleaning.

The muscles projecting between the metatarsal bones are the
interossei ; the fascia covering them should be removed.

The PLANTAR ARCH (fig. 79, d) is the portion of the external Arch of the
plantar artery which reaches from the l^ase of the metatarsal bone artery^

relations

with

muscles,

DISSECTION OF THE FOOT.

of the little toe to the upper end of the first interosseous space :
internally the arch is completed by a communicating branch from
the dorsal artery of the foot (p. 182). It is placed across the
tarsal ends of the metatarsal bones, in contact with the interossei, I
but under the flexor tendons and the adductor obliquus hallucis.

Fig. 78. — Third View of the Sole of the Foot (Illustrations
OF Dissections).

Muscles :

A. Flexor brevis hallucis.

B. Adductor obliquus hallucis.
c. Flexor brevis minimi digiti.

D. Adductor transversus hallucis.

Arteries :

a. Internal plantar, cut.
h. External plantar.

c. Its four digital branches.
Nerves :

1. Internal plantar, cut.

2. External plantar.

3. Its superficial part, cut.

4. The deep part, with the plantar
arch.

5. Offsets to the outer lumbrical
muscles.

veins and Venae comites lie on the sides of the artery, and the deep part of

nerve ; ^j^g external plantar nerve accompanies it.

brandies:- From the front or convexity of the arch the digital branches are

supplied, and from the opposite side small nutritive branches arise.

^eifoSdin^ Three small arteries, the posterior perforating, leave the deep

PLANTAR ARCH OF VESSELS.

209

aspect of the vessel : they pass to the dorsum of the foot through
the three outer metatarsal spaces, and join the dorsal interosseous
branches (p. 184).

The digital branches (c) are four in number, and supply both j^^^J ^ ^^

c Internal plantar artery
1. Internal plantar nerve

•2. External plautarnen'e.
/*. External plantar arteiy.

3. Superficial branch
external nerve.

4. Deep branch of the
ex-temal nerve.

Fig. 79. — Fourth View of the Sole of the Foot (Illustratioss

OF DiSSECTIOXS)

Mtiscles :

0. Three plantar interos.sei.

1. Four doi-sal interossei.

Arteries :

a. Internal plantar, cut.

b. External plantar.

c. Its four digital branches.

d. Plantar arch.

R. Dorsal of foot entering the sole.
f. Artery of great toe.

g. Branch to inner side of great
toe.

h. Branch for the supply of gieat
toe and the next.

Nerves :

1. Internal plantar, cut.

2. External plantar.

3. Its superficial part.

4. Its deep part, the latter supply-
ing oflFsets to the interosseous muscles.

sides of the three outer toes and half the next. One to the outer three toes
side of the little toe is single ; the others lie over the interossei in *"'i»^*i^
the outer three metatarsal spaces, but Ijeneath the adductor trans-
versus halhicis (fig. 78), and bifurcate in front to supply the

D.A. P

210

muscular
and

anterior
perforating
offsets ;

lirst,

second,
third,

fourth
digital ;

junction
with inner
plantar ;
distribution
on the toes.

Ending of
the dorsal
artery of
the foot :

its digital
bi-anches,

on the
digits.

External
plantar
nerve ends
in the deep
muscles :

like ulnar
nerve.

Dissection.

Transverse
metatarsal
ligament.

DISSECTION OF THE FOOT.

contiguous sides of two toes. They give fine offsets to the interossei.
to some lumbricales, and the adductor transversus ; and at the point
of division they send small communicating branches — anterioi
perforating, to join the interosseous arteries on the dorsum of th(
foot (p. 184).

The first digital runs on the outer side of the little toe, supplying
the fl.exor brevis minimi digiti, and distributes small arteries to tht»
integuments of the outer border of the foot.

The second belongs to the sides of the fifth and fourth toes, and
furnishes a branch to the outer lumbrical muscle.

The third is distributed to the contiguous sides of the fourth and
third toes, and emits a branch to the third lumbricalis.

The fourth, or most internal, corresponds with the second inter-
osseous space, and ends like the others on the third and second
digits ; it may assist in supplying the third lumbricalis.

The last two are joined by superficial digital branches of the
internal plantar at the root of the toes.

On the sides of the toes the dis^josition of the arteries is like that
of the digital in the hand (p. 72). They extend to the end,
where they unite in an arch, and give ofisets to the sides and ball
of the toe ; and the artery on the second digit anastomoses at the
end of the toe with a branch from the dorsal artery of the foot.
Near the front of the first and second phalanges they form anasto-
motic loops beneath the flexor tendons, from which the phalangeal
articulations are supplied.

The DORSAL ARTERY OF THE FOOT (fig. 79, e) enters the sole at
the posterior part of the first (inner) metatarsal sj^ace, and ends by
inosculating with the plantar arch. By a large digital artery it
furnishes branches to both sides of the great toe and half the next,
in the same manner as the radial artery in the hand is distributed
to one digit and a half {p. 80).

The digital branch (/) extends to the front of the first inter-
osseous space, and divides into collateral branches (h) for the
contiguous sides of the great toe and the next. Near the head
of the metatarsal bone it sends inwards, beneath the flexor
muscles, a digital branch (g) for the inner side of the great toe.

The arteries have the same arrangement along the toes as the
other digital branches ; and that to the second digit anastomoses at
the end with a branch of the plantar arch.

The DEEP PART OF THE EXTERNAL PLANTxVR XERVE (fig. 79, "*)

accompanies the arch of the artery, and ends internally in the
adductor obliquus hallucis. It furnishes branches to all the
interossei, to the transversus adductor, and to the outer three
lumbrical muscles (Brooks). This nerve corresponds with the
deei3 portion of the ulnar nerve in the hand.

Dissection. It will be needful to remove the transverse
adductor muscle to see a ligament across the heads of the
metatarsal bones.

The TRANSVERSE METATARSAL LIGAMENT is a strong fibrous band,
like that in the hand (p. 81), which connects together all the

THE INTEKOSSEOUS MUSCLES. 211

tatarsal bones at their anterior extremity. A thin fascia covering
:.. interosseous muscles is attached to its hinder edge. It is con-
cealed hy the adductor transversus hallucis, and by the tendons,
vessels, and nerv'es of the toes.

Dissection. To complete the dissection of the last layer of Dissect the
muscles, the flexor Ijrevis minimi digiti may be detached and of^mSes.
thrown forwards. Dividing then the metatarsal ligament between
the l)ones, the knife is to be carried directly Imckwards for a short
distance in the centre of each interosseous space, except the first,
in order that the two interosseous muscles may be separated
from each other. All the interossei are visible in the sole of
the foot.

The fascia covering the muscles should be taken away if any
remains, and the branches of the external plantar nerve to them
should be dissected out.

Fourth Layer of Muscles (fig. 79). In the fourth and last Fomtu
layer of the foot are contained the interosseous muscles, and the muscles,
tendons of the tibialis posticus and peroneus longus.

The INTEROSSEOUS MUSCLES (fig. 79) are situate in the intervals interossei.
between the metatarsal bones : they consist of two sets, plantar and
doi-sal, like the interossei in the hand. Seven in number, there are
three plantar and four doi-sal ; and two are found in each space,
except the innermost.

The plantar muscles (o) are slender fleshy slips, belonging to the Three plan-
outer three toes. Each arises from the under and inner surface of outer toes,
the corresponding metatarsal bone (fig. 76, p. 201) ; and is inserted
partly into the til)ial side of the base of the first phalanx of the
same toe, and j^artly by an expansion to the extensor tendons on
the dorsum of the phalanx. These muscles are smaller than the
dorsal, and are placed more in the sole of the foot.

The dorsal muscles (i), one in each space, arise by two heads i-'our doi-sai

. . between the

from the lateral surfaces of the l)ones between which they lie, bones,

(fig. 76), and are inserted like the others into the side, and on the

dorsum of the metatarsal phalanx of certain toes. Thus, the inner

two muscles belong to the second toe, one to each side ; the next

belongs to the outer side of the third toe ; and the remaining one

to the outer side of the fourth toe.

The interossei are crossed by the external plantar vessels and Relations.

ner\e, and their digital branches ; and they lie beneath the

adductor transversus hallucis and the metatarsal ligament. The

posterior perforating arteries pierce the hinder extremities of the

dorsal set.

Action. Like the interossei of the hand (p. 81), thev will Use as

"" flexors

contribute to the bending of the metatarso-phalangeal joints, and ' '

straighten the two interphalangeal joints. extensors;

They can act also as abductors and adductors of the toes. Thus, as adduc-

the plantar set will l)ring the three outer toes towards the second ^°^'

toe ; and the dorsal muscles will abduct from the middle line of the Xor^^ ^^'

second toe, — the two attached to that digit moving it to the right

and left of the said line.

P 2

212

DISSECTION OF THE LEG.

Trace out
the deep
tendons.

Insertion of
tendon of
tibialis
posticus

and meta-
tarsus.

Insertion of
tendon of
peroneus
longus :

Dissection. Follow the tendon of the tibialis posticus muscle
from its positioii l)ehind the inner malleolus to its insertion into the
navicular hone, and trace the numerous processes that it sends for-
wards and outwards (fig. 76). Open also the fibrous sheath of the
tendon of the peroneus longus, which crosses from the outer to the
inner side of the foot.

The tendon of the tibialis posticus is continued forwards over
the internal lateral ligament of the ankle-joint and the internal
calcaneo-navicular ligament, to be inserted into the tuberosity of the
navicular bone. From its insertion processes are continued to many
of the other bones of the foot : — One is directed backwards to the
sustentaculum tali of the os calcis. Two offsets are directed for-
wards ; — one to the internal cuneiform bone, the other, much the
larger, is attached to the middle and outer cuneiform, to the cuboid
bone, and to the bases of the second, third, and fourth metatarsal
bones. In other words, extensions pass into all the tarsal bones
except one (astragalus), and into all the metatarsal l)ones except two
(first and fifth).

Where the tendon is placed over the calc<ineo-navicular ligament,
it contains a fibro-cartilage, or occasionally a sesamoid bone.

The tendon of the peroneus longus muscle winds round the
cuboid bone, and is continued inwards in the groove on the under-
surface to be inserted into the internal cuneiform l)one and the base
of the metatarsal bone of the great toe ; and sometimes by a slip into
the base of the second metatarsal bone.

In the sole of the foot (fig. 79), it is contained in a sheath
which is completed, towards the outer part, by the fibres of the
long plantar ligament prolonged to the tarsal ends of the third
and fourth metatarsal bones ; but it is formed internally only
Ijy areolar tissue. A synovial membrane luljricates the sheath.

Where the tendon turns round the cuboid bone it is thickened,
and contains a fibro-cartilage or a sesamoid bone.

Section VII.

LIGAMENTS OF THE KNEE, ANKLE, AND FOOT.

Examine
first the
knee-joint.

Dissection
to see knee,

capsule,

and
tendons.

Directions. In examining the remaining articulations of the
limb, the student may take first the knee-joint, unless this has
become dry ; in that case the ligaments of the leg, ankle-joint, and
foot may be dissected while the knee is being moistened.

Dissection. For the preparation of each ligament of the knee-
joint, it is sufficient to detach the muscles and tendons from around
it, and to remove the areolar tissue or fibrous structure which may
obscure or conceal the ligamentous band. A kind of aponeurotic
capsule is to be defined on the front of the joint ; and some
tendons, namely, those of the biceps, popliteus, adductor magnus,

EXTERNAL LIGAMENTS OF KNEE.

213

and semimeml )ranosu.s, are to he followed to their insertion, a part
of each being left.

Articclatiox of the Knee. The knee is the largest joint in Bones iu the
the l>ody, and is formed hy the contiguous ends of the tibia and '"^'^ J^'" •
femur, and of the patella. The articular surfaces of the bones are
covered with cartilage, and are maintained in apposition by strong
and numerous ligaments.

The ca2)sule (fig. 80) is an aponeurotic covering on the front of Capsule:
the joint, which closes the wide intervals l)etween the anterior and
the lateral ligaments ; and it is derived from the iiiscia lata united how formed*
with fibrous offsets of the extensor and flexor muscles. It covers

Fig. 80. — External Aspect op the
KxEE- Joint (Boukgery).

1. Anterior ligament.

2. External lateral ligament.

3. Interosseous membrane.

4. Lower extremity of the ilio-
tibial band of the fascia lata, forming
part of the capsule.

Fig. 81. — Internal Aspect of the
Knee-Joint (Bocrgery).

1. Tendon of the extensor muscle,
ending below in the ligament of the
patella, 2.

3. Internal lateral ligament.

4. Inner part of the capsule.

the anterior and the external lateral ligaments, being inserted below
into the heads of the tibia and fibula ; and it Idends on the inner
side with the internal lateral ligament. It is separated from the
synovial membrane by the anterior ligament and by fat.

Dissection. Four additional ligaments, anterior and posterior,
internal and external lateral, are situate at opposite parts of the
articulation. The posterior and the internal lateral ligaments will
appear on the removal of the areolar tissue from their surfaces ; but
the anterior and the external lateral are covered by the aponeurosis
on the front of the joint, and will not be laid bare till this has been
cut through. If there is a second external lateral band present, it
is not concealed by the aponeurosis.

The external lateral ligament (fig. 80, '■^) is round and cord-like.
It is attached to the tuberosity of the outer condyle of the femur,

arrange-
ment.

The external
ligaments.

To define
the liga-
ment.s
how to
proceed.

External
lateral liga-
ment is
small :

214

DISSECTION OF THE LEG.

occasional
band.

Tendon of
the. biceps is
divided.

Tendon of
the popli-
teus.

and of

adductor

magnus.

Internal
lateral
ligament ;

attach-
ments ;

is joined by
semimem-
branosus.

Insertion
of the semi-
membrano-
sus.

Posterior
ligament.

below the tendon of the gastrocnemius, and descends vertically,
partially subdividing the tendon of the biceps, to a depression on
the upper and outer part of the head of the fibula. Beneath the
ligament are the tendon of the |)oj)liteus and the external lower
articular vessels and nerve.

A second fasciculus is sometimes present behind tlie other, but
it is not attached to the femur ; it is connected above with tlie
outer head of the gastrocnemius, and below with the styloid process
of the head of the fibula.

The tendon of the biceps is inserted Ijy two main pieces into the
head of the fibula ; and from both of these fibres are prolonged to
the head of the tibia. The external lateral ligament passes between
these pieces into which the tendon is partially split.

The tendon of the popliteus may be followed l)y dividing the
posterior ligament. It arises from the fore part of the oblong
depression on the outer surface of the external condyle of the
femur. In its course to the outside of the joint, it crosses the
external semilunar fibro-cartilage and the upper tibio-peroneal
articulation. When the joint is bent, the tendon lies in the hollow
on the condyle ; but it slips out of that groove when the limb is
extended.

The tendon of the adductor magnus is inserted into the adductor
tubercle on the internal condyle of the femur, above the attachment
of the internal lateral ligament.

The internal lateral ligament (fig. 81,-^) is attached above to the
condyle of the femur, where it blends with the capsule ; l)ut l)ecom-
ing broadened out and thicker below, and separate from the rest of
the capsule, it is fixed for about an inch into the inner surface of
the tibia, l)elow the level of the ligamentum patellae : some of the
deeper fibres join the internal semilunar fibro-cartilage.

The tendons of the sartorius, gracilis, and semitendinosus muscles
lie over this ligament ; and the tendon of the semimembranosus,
and the internal lower articular vessels and nerve are beneath it.
To the posterior edge some fibres from the tendon of the semimem-
branosus are added.

The te7idon of the semimemhranosus muscle is inserted l)eneath the
internal lateral ligament into the lower part of the groove at the
l)ack of the inner tul)erosity of the til)ia : between it and the upper
edge of the groove is a synovial bursa. The tendon sends a few
fibres into the internal lateral ligament, a prolongation to join the
fascia on the popliteus muscle, and another to the posterior ligament
of the knee-joint (fig. 52, p. 128).

The posterior ligament is wide and membranous, and is formed
in great part by a strong process from the tendon of the semimem-
branosus, which is directed across the joint to the outer side. It is
fixed below to the head of the tibia behind the articular surface ;
and above, it is attached in the centre to the femur at the upi:)er
border of the intercondylar notch, but on each side it joins the
tendinous head of the gastrocnemius. Numerous apertures exist
in it for the passage of vessels and nerves to the interior of the

INTERIOR OF THE KNEE JOINT. 215

irtieiilation ; and the tendon of the popliteiis pierces its outer
part.

The anterior ligament or ligamentum patellcB (fig. 81,^) is the Anterior
infrapatellar part of the tendon of insertion of the extensor muscle ^'S*™*'"*
of the knee. About two inches long, it is atUiched alx)ve is infra-
to the apex and lower liorder of the patella ; and below to the tendon^
tubercle of the tibia. An expansion of the quadriceps extensor
covers it ; and a Inirsa intervenes between it and the front of the
tibia above the tubercle.

Dissection (fig. 82). To see the reflections of the syno\dal mem- Open the
l>rane, mise the knee on blocks, and open the joint in front by an J^front'^*^

Fro. 82. — Interior of the Knee-joint, thk Capsule of the Knee-
joint CUT ACROSS, and THE PaTELLA THROWN DOWN, TO SHOW THE

Named Folds of the Synovial Sac

a. Mucous Hgament.

b. Internal, and c, external alar ligament.

incision on each side above the patella. When the anterior portion
of the capsule with the patella is thrown down, a fold (mucous
ligament) will be seen extending from the intercondylar fossa of the
femur to a mass of fat l)elow the patella. On each side of the
patella is another fold (alar ligament) also over some fat.

The limb may be laid flat on the table, and some of the posterior and behind,
ligament remo^'ed, to show the pouches of the synovial membrane
which project Ijehind over the condyles of the femur ; but the
limb is to be replaced in the former position before the parts
are learnt.

The synovial 'membrane (fig. 82) lines the interior of the joint, syno\-ial
and is continued to the margins of the articular surfaces of the membrane
bones. It invests the interarticular fibro-cartilages after the manner

214

DISSECTION OF THE LEG.

occasional
band.

Tendon of
the. biceps is
divided.

Tendon of
the i)opli-
teus.

and of

adductor

magnns.

Internal
lateral
ligament ;

attach-
ments ;

is joined by
semimem-
branosus.

Insertion
of thesemi-
membrano-

Posterior
ligament.

below the tendon of the gastrocnemius, and descends vertically,
partially subdividing the tendon of the biceps, to a depression on
the upper and outer part of the head of the fibula. Beneath the
ligament are the tendon of the popliteus and the external lower
articular vessels and nerve.

A second fasciculus is sometimes present Ijehiiid the other, but
it is not attached to the femur ; it is connected above with the
outer head of the gastrocnemius, and below with the styloid process
of the head of the fibula.

The tendon of the biceps is inserted by two main pieces into the
head of the fibula ; and from both of these fibres are prolonged to
the head of the tibia. The external lateral ligament passes between
these pieces into which the tendon is partially split.

The tendon of the popliteus may he followed by dividing the
posterior ligament. It arises from the fore part of the oblong
depression on the outer surface of the external condyle of the
femur. In its course to the outside of the joint, it crosses the
external semilunar fibro-cartilage and the upper tibio-peroneal
articulation. "When the joint is bent, the tendon lies in the hollow
on the condyle ; but it slips out of that groove when the limb is
extended.

The tendon of tJie adductor magnus is inserted into the adductor
tubercle on the internal condyle of the femur, above the attachment
of the internal lateral ligament.

The ifiter/ial lateral ligament (fig. 81,-^) is attached above to the
condyle of the femur, where it blends with the capsule ; Ijut l)ecom-
ing broadened out and thicker below, and separate from the rest of
the capsule, it is fixed for about an inch into the inner surface of
the til)ia, below^ the level of the ligamentum patellae : some of the
deeper fibres join the internal semilunar fibro-cartilage.

The tendon of the semimemhi'anosus muscle is inserted lieneath the
internal lateral ligament into the lower part of the groove at the
back of the inner tuberosity of the tibia : between it and the upper
edge of the groove is a synovial bursa. The tendon sends a few
fibres into the internal lateral ligament, a prolongation to join the
fascia on the popliteus muscle, and another to the posterior ligament
of the knee-joint (fig. 52, p. 128).

The posterior ligament is wide and membranous, and is formed
in great part by a strong process from the tendon of the semimem-
branosus, which is directed across the joint to the outer side. It is
fixed below to the head of the tibia l)ehind the articular surface ;
and above, it is attached in the centre to the femur at the upper
border of the intercondylar notch, but on each side it joins the
tendinous head of the gastrocnemius. Numerous apertures exist
in it for the passage of vessels and nerves to the interior of the

INTERIOR OF THE KNEE JOINT. 215

i I Illation ; and the tendon of the poplit«iis pierces its outer

The anterior ligament or ligamenturn patellcB (fig. 81,^) is the Anterior
infrapatellar part of the tendon of insertion of the extensor muscle ^'8*°^*^"^
of the knee. About two inches long, it is attached alx)ve is infra-
to the apex and lower Ixjrder of the patella ; and below to the tendon!
tubercle of the tiljia. An expansion of the quadriceps extensor
covers it ; and a bursa intervenes between it and the front of the
tibia above the tubercle.

Dissection (fig. 82). To see the reflections of the syno^dal mem- Open the
brane, mise the knee on blocks, and open the joint in front by an l^^ont"*

Fig, 82. — Ixterior of the Knee-joint, the Capsule of the Knee-
joint CUT ACROSS, AND THE PaTELLA THROWN DOWN, TO SHOW THE

Named Folds of the Synovial Sac.

a, Mucous ligament.

b. Internal, and c, external alar ligament.

incision on each side above the patella. When the anterior portion
of the capsule with the patella is thrown down, a fold (mucoiLS
ligament) will be seen extending from the intercondylar fossa of the
femur to a mass of fat l)elow the patella. On each side of the
patella is another fold (alar ligament) also over some fat.

The limb may be laid flat on the table, and some of the posterior and behind,
ligament removed, to show the pouches of the synovial membrane
which project l)ehind over the condyles of the femur ; but the
limb is to be replaced in the former position before the parts
are learnt.

The synovial membrane (fig. 82) lines the interior of the joint, syno\-iai
and is continued to the margins of the articular surfaces of the '"embrane
bones. It invests the interarticular fibro-cartilag&s after the manner

216

DISSECTION OF THE LEG.

thrown into
folds named
ligaments, —
mucous,

and alar.

Synovial
pouches ;
two behind

and one
before.

Articular
fat:

below
patella,

above the
patella.

Dissect
internal
ligaments.

Ligaments
within the
capsule.

of serous membranes, and sends a pouch between the tendon of the
popliteus and the external fibro-cartilage and the head of the tibia ;
it is also reflected over the strong crucial ligaments at the back of
the joint.

There are three named folds of the s3^novial membrane. One in
the centre of the joint is the mucous ligament (a), which contains
small vessels and some fat, and extends from the interval betAveen
the condyles to the fat below the i)atella. Below and on each side
of the patella is another fold — alar ligament (b and c), which is
continuous with the former below the patella, and is placed over a
mass of fat : the inner (h) is prolonged farther than the outer by a
semilunar piece of the syno^dal inemljrane.

At the back and front the articulation pouches are prolonged
beneath the tendons of muscles. Behind there are two, one on each
side, between the condyle of the femur and the tendinous head of
the gastrocnemius. On the front, the sac projects under the extensor
muscle one inch above the articular surface ; and if it communicates
with the bursa in that situation, as is usually the case, it will reach
two inches above the joint-surface of the femur. When the joint is
bent there is a still greater length of the serous sac above the patella.

Fat around the joint. Two large masses are placed above and
below the patella, and a smaller quantity of fat surrounds the
crucial ligaments.

The infrapatellar mass, the largest of all, fills the interval between
the patella with its ligament and the head of the tibia, and gives
origin to the ridges of the synovial membrane. From it a piece is
continued round the patella ; but it is larger at the inner margin
than at the outer, and overhangs the inner perpendicular facet of
that bone. This infrapatellar pad adapts itself to the varying shajDe
and extent of the angular interspace between the bones and the liga-
mentum patellae in the movements of the joint.

The suprapatellar pad is interposed between the common extensor
tendon and the femur round the top of the synovial sac, and is
larger on the outer than the inner side.

Dissection (fig. 83). The ligamentous structures within the
capsule will be brought into view, while the limb is still in the
same position, by throwing down the patella and its ligament, and
clearing away the fat behind it. In this step the student must be
careful of a small transverse l:)and which connects anteriorly the
interarticular fibro-cartilages.

The remains of the capsule and other ligaments, and the synovial
membrane, are next to be cleared aAvay from the front and back of
the crucial ligaments, and from the fibro-airtilages. While cleaning
the posterior crucial ligament, the limb is to be placed flat on the
tcible with the i)atella down, and the student is to be careful of a
band in front of the ligament from the external fibro-cartilage, or
of two bands, one before and the other Ijehind it.

Ligaments within the capsule. The ligamentous structures within
the capsule consist of the central crucial ligaments, and of two plates
<^f fibro-cartilage on the head of the tibia.

IXTEKNAL LIGAMENTS OF THE KNEE.

Tlie crucial ligaments (fig. 83) are two strong fibrous cords
betAveen the ends of the tibia and femur, which maintain the bones
in contact. They cross one another like the legs of the letter X,
and have received their name from that circumstance. One is
much anterior to the other at the tibial attachment.

The anterior ligament (/) is very oblique in its direction, and is
longer than the posterior. Inferiorly it is attached in front of the
spine of the tibia, close to the inner articular surface, reaching back
to the inner point of the spine ;
superiorly it is inserted into an
impression on the hinder part of
tlie inner surface of the external
condyle of the femur.

The ijosterior ligament (e), the
thicker of the two, is almost
vertical between the bones at the
back of the joint. By the lower
end it is fixed to the hindmost
impression of the hollow l)ehind
the spine of the tibia, near the
margin of the bone; and above,
it is inserted into an impression
at the lower part of the outer
surface of the internal condyle,
and extending forwards to the
centre of the intercondylar fossa.

The use of these ligaments in
the movements of the joint may
now l)e studied after the external
ligaments have been cut through. j.^^ 83.-Lnxkhakticolar Liga-

MKNTS OF THE KnBE-JOIXT.

Two crucial
ligaments.

Anterior is
oblique ;

its attach-
ments.

ct. Internal, and b, external
semilunar fibro-cartilage ; the latter
rather displaced by the bending of
the joint.

c. Posterior crucial ligament,
with d, the ascending ligamentous
band of the external fibro-cartilage.

/. Anterior crucial ligament.

g. Patellar surface of the femur.

As long as both ligaments are
whole, the bones cannot be sepa-
rated from each other.

Rotation inwards of the tibia
is limited by the anterior crucial.
Rotation out is not checked by
either ligament ; for the bands un-
cross in the execution of the move-
ment, and will permit the tibia
to be turned hind part foremost.

Sui>posing the tibia to move as in straightening the limb, the
anterior prevents that bone being carried too far forwards by the
extensor muscle, or by external force ; and the ligament is brought
into action at the end of extension, because the tibia is being put
in front of the femur. Its use is shown by cutting it across, and
leaving the posterior entire, as then the tibial articulating surfaces
can be placed in front of the femoral in the half-bent state of the
joint.

The posterior crucial prevents displacement backwards of the
tiV)ia by the flexors or by force; and it is stretched in extreme

Their use.

Both unite
the bones.

Rotation
inwards
checked by
anterior.

Special use
of anterior,

and poste-
rior crucial.

218

DISSECTION OF THE LEG.

Semilunar
cartilages
are two.
Common
characters.

Internal
is oval.

External
nearly cir-
cular in
form :

its trans-
verse and

flexion, in which the tibia is being drawn back over the femur.
This use will be exemplified by cutting across the posterior (in
another joint or in another dissection) and leaving entire the ante-
rior ; when this has been done, the articular surfaces of the tibia
can be carried nearly altogether behind the condyles of the femur.

The two mterarticular or semilunar fihro-cartilages (fig. 84) partly
cover on each side the articular surface of the til)ia.

They are thick at the convex margin, where they are united l>y
fibres to the capsule, and are thin, sharp, and free at the concave
edge ; they are hollowed on the upper surface, so as to assist in

giving depth to the fossae for
the reception of the condyles
of the femur, but are flattened
below. Inserted into the tibia
at their extremities, they are
coarsely fibrous at their attach-
ment to the bone, like the
crucial ligaments ; and they
become cartilaginous only
where they lie between the
articular surfaces. The syno-
vial membrane is reflected over
them.

The internal fibro-cartilage {a)
is oval in form, and is less
sharply curved than the ex-
ternal. In front it is attached
l)y a pointed end close to the
anterior margin of the head of
the tibia, in front of the anterior
crucial ligament. At the back,
where it is much wider, it is
fixed to the inner lip of the
hollow beliind the spine of the
til)ia, between the attachment
of the other cartilage and the posterior crucial ligament.

The external fibro-cartilage (h) is nearly circular in form, and is
connected to the bone Avithin the points of attachment of its fellow.
Its anterior part is fixed in front of the spine of the tibia, close to
the outer articular surface, and ojDposite the anterior crucial ligament
which it touches ; and its posterior extremity is inserted behind and
between the two osseous points of the spine. This fibro-cartilage is
less closely united to the capsule than the internal, for the fore part
is in the centre of the joint, and the tendon of the popliteus muscle
separates it behind from that membrane.

The outer fibro-cartilage is provided with two accessory bands,
one in front, the other behind.

The anterior or transverse ligament (c) is a narrow band of fibres
between the semilunar cartilages at the front of the joint. Some-
times it is very small or even absent.

Fig. 84. — The Fibro-caktilages of
THE Knee-Joint. View op the
Head op the Tibia with the
fibro-cartilages attached ; the
Crucial Ligaments have been cut

THROUGH.

a. Inner, and h, outer semilunar
fibro-cartilage.

c. Transverse, and d,
posterior band (cut) of
cartilage.

e. Posterior, and /, anterior crucia]
ligament.

ing or
the external

ARTICULAK SURFACES IN THE KNEE-JOINT. 219

The posterior or ascending hand (d), thicker and stronger than the posterior
other, springs from the back of the outer fibro-cartilage, and is
iiLserted into the femur, either as a single band (fig. 83, fZ), when
it is generally in front of the posterior crucial, or as t^^'o bands
— one being before, and the other behind that ligament.

Use. The fibro-cartilages deepen the sockets of the tibia for the Use of fibre-
reception of the condyles of the femur, and fill the interval between ^»'^*''^t,'es,
the articular surfaces of the bones at the circumference of the joint ;
they distribute the pressure of one bone on the other over a larger
surfjice, and cause the force of shocks to be diminished in transmis-
sion. In flexion and extension they move forwards and backwards in flexion
with the tibia over the femoral condyles. During flexion they fio^^^ "'
recede somewhat from the fore part of the joint, and surround the
narrow parts of the condyles ; but in extension they are flattened
out on the surface of the tibia. Of the two cartilages, the external
moves the most in consequence of its being less attached to the
capsule.

In rotation the fibro-cartilages follow the condyles of the femur, and in rota-
and glide over the til)ial articular surfaces, the external moving *'°" •
more than the internal.

The accessory l)ands in front and behind serve to retain in place use of
the less fixed external fibro-cartilage ; thus the anterior ligament bands.*^^^
^: ops forwards the front of that cartilage in flexion, and the posterior

ures the back of the same from displacement in rotation.

Articular surfaces of the hones. The end of the femur is marked surfaces of
by a patellar and two tibial surfaces. ^"'^•

The patellar is placed in the middle above the others ; it is on femur,
hollowed along the centre, with a slanting surface on each side, the P*^^'*'^
outer being much the larger of the two.

The surfaces for contact with the tibia, two in number, occupy and tibial :
the ends of the condyles, and are separated from the patellar im- characters
pression by an oblique groove on each side. At the lower part of ^^*''^'^^'
each is a somewhat flattened surface, which is in contact with the
tibia in standing ; while behind there is a more convex portion,
which touches the tibia in flexion.

The inner condyle of the femur is curved in its anterior third, peculiarities
the concavity being directed outwards and backwards; this has°^'""^^"
been named the " oblique curvature." Along the concave margin
of the curve is a semilunar facet, Avhich touches the perpendicular
surface of the patella in extreme flexion.

On the head of the tibia are two slight articular hollows, the Articular
inner being the deeper and larger, which rise towards the middle tJbia.^^^ °
of the ])one, on the points of the tibial spine.

The joint-surface of the patella has the following marks. Close Subdivision

to the inner edge is a narrow perpendicular facet, and along the J^^^f^g^of

lower border is a similar transverse mark. Occupying the rest of patella.

the bone is a squarish surface, which is subdivided by a vertical and

1)V two transverse lines into three pairs of facets — upper, middle, and

lower. The transverse lines are fainter than the vertical.

Movements of the joint. The chief movements of the knee are two Kinds of "S.

movement.

222

DISSECTION OF THE LEG.

Interosse-
ous mem-
brane be-
tween the
shafts :

attach-
ments ;

apertures.

IHotion
slight,

in upper,
and lower
articula-
tion.

The INTEROSSEOUS MEMBRANE fills the interval between the
bones of the leg, and serves as an aponeurotic partition between
the muscles on the front and back of the limb. Its fibres are
directed for the most part downwards from the tibia to the fibula ;
but a few cross in the opposite direction.

Internally it is fixed to the outer edge of the tibia ; and externally,
to the prominent interosseous ridge on the inner side of the fibula.
In its ujjper part, close to the neck of the fibula, is an o^'al opening
about an inch in length, which transmits the anterior tibial vessels ;
and at the lower end, between the membrane and the inferior

articulation, is another
small opening for the an-
terior peroneal vessels.

Movement. Very little
movement is allowed in
the tibio-ti])ular articula-
tions, as the chief use of
the fibula is to giAe
strength and elasticity to
the ankle-joint, and attach-
ment to muscles of the
leg.

In the upper joint there
is a slight gliding chiefiy
from within out. In the
lower articulation the liga-
ments permit some yield-
ing of the fibula to the
jiressure of the astragalus,
as when the weight of the
body is thrown on the
inner side of the foot ;
but if the force is violent
the fibula will be fractured
about the junction of the third and lowest fourths sooner than the
ligaments give way.

Fig. 85.— Inner Side op the Ankle
(altered from Bourgery).

1. Posterior, 2, middle, and 3, anterior
fibi-es of the inner lateral ligament.

4. Internal calcaneo- navicular ligament.

Bones in
the ankle-
joint.

Dissection
of the ankle-
joint.

Articulation of the Ankle (figs. 85 and 86).

The ankle is a hinge joint, in whicb the upper part of the
astragalus is received into an arch formed by the lower ends of the
tibia and fibula ; and the four ligaments belonging to this kind of
articulation connect together the bones.

Dissection. To make the dissection required for the ligaments
of the ankle-joint, the muscles and the fibrous tissues and vessels
must be removed from the front and back of the articulation.

For the purpose of defining the lateral ligaments, the liml) must
be placed first on one side and then on the other. The internal
ligament is wide and strong, and lies beneath the tendon of the
tibialis posticus. The external is divided into three separate pieces ;

AETICULATION OF THE ANKLE.

223

and to show these, the peronei muscles, and the remains of the
annular ligament below the outer malleolus, should be taken away.

The anterior ligament is a thin fibrous memljrane, which is
attached to the tibia close to the articular surface, and to the upper
part of the astragalus near the articulation with the navicular bone.
In the ligament are some rounded intervals and apertures for vessels.
On the sides it joins the lateral ligaments.

The posterior ligament is thinner than the anterior, and is attached
to the tibia and astragalus, close to the articular surfaces of the
bones. Towards the outer
side it consists of transverse
fibres, which are fixed into
the hollow on the inner side
of the external malleolus.

The internal lateral or
deltoid ligament (fig. 85)
is attached by its upper,
-mailer end to the inner
malleolus, and by its base
to the tarsal bones, by fibres
which radiate to their inser-
tion in this manner : — The
posterior (^) are directed to
the hinder part of the inner
surface of the astragalus ;
the middle (^) pass verti-
ciilly to the sustentaculum
tali of the os calcis ; and
the anterior (^), which are
thin and oblique, join the
internal calcaneo-navicular

Anterior
ligament
thin and
imperfect.

Posterior
ligament.

Internal or
deltoid :

attach-
ments.

Fig. 86. — Exteenal Lateral Ligament op
THE Ankle (altered from Bourgery).

1. Anterior part, 2, posterior part, and
3, middle part of the outer ligament.
,. 1 , . . -, 4. Interosseous of astragalus and os

ligament and the inner side calcis.

of the navicular bone. The 5. External calcaneo-navicular ligament,
tendons of the tibialis pos-
ticus and fiexor longus digitorum are in contact with this ligament.

The external lateral ligament (fig. 86) consists of three separate
pieces, anterior, middle, and posterior, which are attached to
the astragalus and the os calcis. The anterior piece Q) is a short
fiat band, which is directed from the fore part of the malleolus to
the side of the astragalus in front of the lateral articular surface.
The middle portion (•^) descends from the tip of the malleolus to the middle
outer surface of the os calcis, about the middle. The posterior (*)
is the strongest, and is almost horizontal in direction ; it is fixed
externally to the pit on the inner surface of the malleolus, and is
inserted into the external tubercle and adjoining posterior part
of the external surface of the astragalus behind the lateral articular
facet.

The posterior and middle fasciculi are placed beneath the peronei relations,
muscles. The middle piece is but slightly in contact above with
the synovial membrane of the ankle-joint ; and both it and the

External
has three
pieces :

anterior,

and pos-
terior ;

224

Open the
ankle-joint.

Synovial
sac.

Surfaces of
the bones
in the joint.

Kinds of
motion.

Flexion

xnovin'
bone ;

state of
ligaments.

Extension ;

movmjj
lx)ne ;

state of
ligaments

slight
lateral
motion.

Dissection
for the
joints of
the foot.

Astragalus
with OS
calcis by

DISSECTION OF THE LEG.

posterior part touch the synovial ineinl)rane l)et\veen the astragalas
and the os calcis.

Dissection. Dividing the ligaments of the ankle-joint, separate
the astragalus from the l)ones of the leg, to see the osseous surfaces
entering into the joint.

The synovial memhrane of the joint lines the capsule, and is
simple in its arrangement ; but the cavity is continued upwards
for a short distance l)etween the tibia and fibula.

Articular surfaces. On the tibia there are tAvo articular surfaces,
one of which corresponds with the end of the shaft, and the other
with the malleolus. On the fibula the surface of the malleolus
which is turned to the astragalus is covered with cartilage.

The astragaliLS has an upper articular surface, wider before than
behind and trochlea-shaped, which is in contact with the end of
the tibia ; and on its sides are articular impressions for contact
with the malleoli, of which the outer is the larger.

Movements. Only the movements of flexion and extension
are permitted in the ankle, except slight lateral movement in half
extension ; in the former movement the toes are raised towards the
fore part of the leg ; and in the latter, they are pointed towards
the ground.

Ill flexion the astragalus moves backwards so as to project behind ;
and the motion is arrested l)y the wide anterior part of the astragalus
l)eing wedged in between the malleoli.

The posterior ligament is stretched o\'er the projecting astragalus,
and the posterior and middle pieces of the external lateral, and the
posterior part of the internal lateral ligament, are made tense.

In extension the astragalus moves forwards over the end of the
tibia, and projects anteriorly. A limit to the movement is imposed
by the meeting of the astragalus with the tibia behind.

The lateral ligaments are partly made tight as in flexion, for
instance, the anterior piece of the external, and the fore and middle
portions of the internal.

When the joint is half extended, so that the small hinder part
of the astragalus is brought into the arch of the leg-bones, a slight
movement of the foot inwards and outwards may sometimes be
obtained ; but if the foot is forcibly extended, the portions of the
lateral ligaments attached to the astragalus prevent this lateral
movement by their tightness.

Dissection. The joints of the foot will be demonstrated by
removing from both the dorsum and the sole all the soft parts
which have been examined. Between the diff"erent tarsal bones
bands of ligament extend, which will be defined by removing the
areolar tissue from the intervals between them (fig. 87).

It will be more advantageous for the student to clean all the
ligaments before he proceeds to learn any, than to prepare only the
bands of one articulation at a time.

Articulation of the astragalus and os calcis. These
bones form two joints, and are kept together by a strong interosseous
ligament ; there are also thin bands on each side and behind.

ARTICULATION OF ASTKAdALUS AND OS CALCIS.

22:

The posterior liyarnent (iig. 87, a) consists of a few tibres between posterior,
the bones, where they are gi-ooved by the tendon of the flexor
* ludlucis ; the internal ligament is a small band passing from the internal,
internal tubercle of the astragalus to the sustentacidum ti\li ; and
the external ligament (b) is connected to the sides of the astragalus external,
and OS calcis, near the middle piece of the external lateral ligament
of the ankle-joint.

The interosseous ligament (tig. 87, c) consists of strong vertical and interos-
and oblique fibres, which are attached above and below to the ^nte.*^
lepressions on the opposed surfaces of the two bones. This
baud extends across between the bones, and its depth is greatest
at the outer side.

In a subsequent stage of the dissection (p. 228) the articular Ai-ticuiar

Fro. 87. — View of the Dorsal Lioauents of the Tarsus.

a. Posterior, b, external, and c,
interosseous ligaments between astra-
galus and OS calcis.

d. Astragalo-navicular.

e. External calcaneo- navicular.

/. Internal, and g, upper calcaneo-
cuboid ligaments.

h. Dorsal naviculo-cuboid band.

i, I', I, Dorsal external, middle,
and internal naviculo-cuneiforra longi-
tudinal bands.

/t. Doi-sal transverse bands between
the cuneiform and cuboid bones.

surfaces of the bones will be seen, viz., one behind the interosseous
ligament, and one in front of it, with two siniovial cavities. synovial

cavities

Movements. It is between the astragalus and os calcis that the _, " '

„ , -. , . . , . Movement

important movements of the foot known as inversion and eversion iietween as-

chierty take place. The motion is one of rotation about an oblique oJ^jJe'is:"'*

axis, which is directed from the upper and inner part of the head ^^is of

of the astragalus, backwards, downwards, and outwards to the lower motion.

and outer part of the posterior extremity of the os calcis. Supposing

the astragalus fixed between the malleoli, and the rest of the foot

free to move, then in inversion the outer part of the os calcis moves inversion.

forwards an^lownwards, and the sustentaculum tali in the opposite

direction, wliiT&-4^e anterior end of the bone is carried somewhat

inwards. As a result of this, aided by corresponding movements

of the anterior tarsal bones, the fore part of the foot is depressed,

22<;

E version.

Condition of
foot in
standing ;

effect of
inversion.

Astragalus
with

navicular
bone :

dorsal
ligament.

To lay bare
the cal-
caneo-navi-
cular liga-
ments.

DISSECTION OF THE LEG.

and the outt

is everted to the
if then inversion
from the ground

The head of the

Internal and

and the arch increased ; the toes are moved inwards

border of the foot sinks, turning the sole in.
In eversion the above movements are reversed.
In the ordinary mode of standing the foot

utmost, or nearly so, by the weight of the body :

is practised, the inner side of the foot is raised

and the part is supported on its outer edge.
Astragalus with the navicular bone.

astragalus is received into the hollow of the navicular bone, and is

united to it by a dorsal ligament ; but the place of plantar and

lateral ligaments is supplied by strong
bands between the os calcis and the
navicular bone.

The astragalo - navicular ligament
(fig. 87, d) is attached to the astra-
galus close to the articulation, and to
the dorsal surface of the navicular
bone : its attachments will be better
seen when it is cut through.

Dissection. The external ligament
of the articulation may be seen on the
dorsum of the foot in the hollow
between the os calcis and the navi-
cular bone, and if the tendon of
the tibialis posticus be removed, the
internal ligament will be exposed,
covering the head of the astragalus
on the inner side and l^elow.

The internal or inferior calcaneo-
navicular ligament (fig. 89, c, p. 227)
is attached behind to the inner and
fore parts of the sustentaculum tali of

external
ligament.

Synovial
sac.

Surfaces of
bone.

FiQ. 88. — Plantar Ligaments
OF THE Foot (Bourgery).

1. Long plantar hgament.

2. Inner part of the short
plantar ligament.

3. Tendon of the peroneus
longus muscle.

extremity and lower border of the
navicular bone. This ligament is
partly fibro- cartilaginous ; its inner
side is crossed by the tendon of the
tibialis ]3osticus muscle ; and its deep surface forms part of the
socket for the head of the astragalus.

The eoiternal calcaneo-navicular ligament (fig. 87, e) is placed
outside the head of the astragalus, and is about three-quarters of an
inch deep. Behind, it is fixed to the upper part of the os calcis,
between the articular surfaces for the cuboid bone and astragalus ;
and in front it is inserted into the outer side of the navicular bone.
The synovial cavity of this articulation is continued backwards
into the joint between the front of the os calcis and tlie astragalus.
Articular surfaces. The head of the astragalus has three convex
articular surfaces, a large one in front, elongated transversely and
broader externally than internally, for the navicular bone ; a narrow
oblique surface below for the os calcis ; and a small intermediate

LIGAMENTS OF TARSAL BONES.

triangular facet internally for the internal calcaneo-iiavieular liga-
ment. The surface of the navicular bone is hollowed, and is
widest externally.

Movement. The navicular moves down and in over the head of
the astragalus in inversion, or up and out in evei-sion.

As the bone is forced downwards, the upper and external liga-
ments of the joint are made tight ;
and when the navicular is moved in
the opposite way, the strong internal
ligament is put on the stretch.

The OS calcis with the cuboid
BONE. The ligaments in this articu-
lation are plantar, doi-sal, and
internal .

The dorsal, or supei'ior, calcaneo-
cuboid liyament (fig. 87, g) is a rather
thin fasciculus of tiljres, which is
attached near to the contiguous ends
of the OS calcis and the cuboid bone ;
it is sometimes divided into two
pieces, or it may be situate at the
outer border of the foot.

At the inner side of the cuboid
bone is a variable internal band
(fig. 87,/) from the os calcis ; this
is fixed behind to the upper part of
the OS calcis, outside the band to
the navicular bone, and in front to
the contiguous inner side of the
cuboid.

The inferior calccineo -cuboid liga-
ment is much the strongest, and is
divided into superficial and deep
parts : —

The superficial portion or long
plantar ligament (fig. 88, i) is attached
to the under-surface of the os calcis
between the posterior and the anterior
tubercles ; its fibres pass forwards to

227

Movement :

state of
ligaments.

internal,

be connected with the ridge on the

KiG. 89. — View OF the Inferior
Ligaments of the Tarsal
Bones.

a. Long plantar cut.

b. Short or deep inferior cal-
caneo-cuboid ligament.

c. Internal calcaneo-navicular.

d. Plantar transveree navi-
culo-cuboid ligament.

c. Dorsal inner naviculo-
cuneiform extending into the
sole of the foot.

/. Plantar transverse ligament
between the inner and middle
cuneiform bones.

g. Plantar transverse band
between the cuboid and outer
cuneiform.

and inferior
ligaments.

The last is
strongest,
and divided
into two
parts :

superficial
and

under-surface of the cuboid bone ;

but the most internal are continued

over the tendon of the peroneus longus muscle, assisting to form its

sheath, and are inserted into the bases of the third and fourth

metatarsal bones.

The deep piece or short plantar ligament (fig. 89, 6), seen on deep band,
division of the superficial {a), extends from the tubercle and the
hollow on the fore part of the under-surface of the os calcis to the
cuboid bone internal or posterior to the ridge.

The synovial cavity of the articulation is simple.

Synovial
sac.

228

DISSECTION OF THE LEG.

Surfaces o
bones.

Movement :

state of
ligaments.

Transverse
tarsal arti-
culation

includes
two joints ;

movements

amputation

practised

here.

Dis.section.

Surfaces of
OS calcis

and astia-
galus.

Union of the

navicular

bone

to the cunei-
foi-m;

synovial
sac :

' Articular surfaces. Both bones are flattened towards the outer
part of the articulation ; but at the inner side the os cakis
is hollowed transversely, and the cuboid bone is convex to fit
into it.

Movement. In this joint the cuboid bone may move in two direc-
tions, viz., obliquely down and in with inversion of the foot, and
up and out with eversion.

In the downward movement the internal lateral and the upper
ligament are made tight ; and in the upward, the calcaneo-cuboid
ligaments of tlie sole are stretched.

Transverse tarsal articulation. This name is given to the
line of articulation crossing the foot between the astragalus and os
calcis behind and the navicular and cul)oid bones in front : it will
be noticed, however, that it is not a continuous joint, but is com-
posed of two separate articulations, viz., the astragalo-navicular and
the calcaneo-cuboid.

i These joints participate, as has been already seen, in the move-
ments of inversion and eversion, the anterior l)ones moving over
the hinder one??, downwards and inwards in inversion, and upwards
and outwards in eversion. It is at this line that the foot is
divided in the operation known as Chopart's amputation.

Dissection, Saw through the astragalus in front of the attiich-
ment of the interosseous ligament between it and the os calcis, and
remove the head of the bone in order to see the disposition of the
inner and outer calcaneo-navicuhar ligaments.

Then the interosseous ligament uniting the astragalus and the os
calcis is to be cut through, to demonstrate its attachments, the
articular surfcices of the bones, and the synovial sacs (]). 225).

Articular surfaces of the two hinder tarsal bones. There are two
articular surfaces, anterior and posterior, to both the astragalus and
the OS calcis. The hinder one of the os calcis is convex from before
back, and the anterior is concave ; but sometimes the latter is
subdivided into two. The surface of the astragalus has a form
exactly the reverse of that of the os calcis, viz., the hinder one
concave and the anterior convex ; the anterior is seated on the head
of the astragalus.

Dissection. The calcaneo-cuboid joint may be opened to see the
articular surfaces ; and the student is to keep in mind that all the
other articulations of the foot are to be opened for the like purpose,
even should directions not be given.

Articulation of the navicular bone. The navicular bone
is united in front to the three cuneiform bones, and laterally to the
cuboid.

In the articulation with the cuneiform hones (fig. 87) there are
three longitudinal dorsal ligaments (i, k, I), one to each bone ; but
the innermost is the strongest and widest, and extends round the
inside of the articulation into the sole of the foot (fig. 89, e).

The place of plantar hands is supplied by processes of the tendon
of the tibialis posticus.

The naviculo-cuneiform articulations form one continuous joint,

ARTICULATION OF THE CUNEIFORM BONES. 229

and from their synovial cavity offsets are sent forvrards between the
I'Uiieiform bones.

Bdween the navicular and cuboid hones there is an oblique dorsal totheeu-
band of fibres (fig. 87, h) ; a transverse plantar band (fig. 89, d),
which is concealed by the tendon of the tibialis posticus ; and a
strong interosseous ligamsnt.

When the bones touch, the surfaces are tipped with cartilage, and synovial
a process of the naviculo-cuneiform synovial cavity extends between ^^'
tliem.

Articulation of the cuneiform bones. These bones are Union of the
united to one another by cross bands ; and the external one articu- ^ngs^*'""
lates with the cuboid after a similar manner.

The three cuneiform bones are connected together by short trans- one with
verse dorsal bands (fig. 87, n) l)etween the upper surfaces, and inter- '

osseous ligaments between the rough parts of the contiguous sides of
the bones. Laterally there are articular surfaces between the lx)nes,
^vith oftsets of the common synovial cavity.

Where the external cuneiform touches the cuboid bone, the sur- and with
uivjcs are covered with cartilage. A dorsal ligament (fig. 87, n) bone:
passes transvei-sely between the two ; and a playitar ligament
(fig. 89, g) takes a similar direction. Between the bones there is
also an interosseous ligament.

This joint is furnished either with a distinct synovial sac, or with synovial
a prolongation of the common synovial cavity.

The synovial cavity of the articulations of the cuneiform bones is Common
common to many of the bones of the tarsus. Placed between the Sc.^^**
navicular and the three cuneiforms, it sends one prolongation for-
wards between the inner and middle cuneiform to the joints with
the second and third metatarsal bones, another between the middle
and outer cuneiform bones, a third outwards to the articulation of
the navicular Avith the culjoid bone (when present), and sometimes
a fourth to the joint between the external cuneiform and the cuboid.

Articular surfaces. On the navicular are three articular facets, Surfaces of
the inner being rounded, and the other two flattened. The three "^
cuneiforms unite in a shallow elliptical hollow, which is most
excavated internally.

Movement. The cuneiform bones glide up and out on the navicular Motion in

inversion
ever-

in inversion of the foot, and down and in in eversion ; and the inner and
one moves more than the others in conscc[uence of the shape of the ^^^^ •
articular surfaces, and the attachment to it of the tibialis anticus.

AVhen the bones pass down the dorsal ligaments are made tight : state of the
and as they rise the interosseous bands will keep them united. 'ga^en ,

In standing these bones are separated somewhat from each other and joints in
with diminution of the arch of the foot, and stretching of the trans- ^ ° *"^'
verse ligaments which connect them.

Articulation of the metatarsal bones. The bases of the four Union of
outer metatarsal bones are connected together by dorsal, plantar, tarsus by
and interosseous ligaments ; and where their lateral parts touch,
they are covered with cartilage, and have offsets of a synovial sac.

The dorsal ligaments (fig. 90) are small transverse bands from dorsal,

230

DISSECTION OF THE LEG.

plantar,

and interos-
seous liga-
ments.

Lateral
union :

synovial

Great toe
separate.

Anterior
ends.

Tarsus and
metatarsus

Joint of
great toe

separate
from rest ;

synovial
sac.

Form of
bones.

Motion up
and down,

and lateral
motion.

Joints of
four outer
toes:

dorsal liga-
ments;

the base of one metatarsal lione to the next. The plantar ligaments
(fig. 88) are similar to the dorsal. The interosseous ligaments are
short transA'erse fibres between the contigiions rough lateral surfaces :
they may be afterwards seen by foreil)ly separating the bones.

Lateral union. The four outer bones touch one another late-
rally ; the second metatarsal lies against the internal and external
cuneiforms ; and the fourth is in contact internally with the outei
cuneiform. The articulating surfaces are covered with cartilage :
and their synovial cavities are offsets of those serving for the
articulation of the same four metatarsal
with the tarsal l)Oiies.

Tlie metatarsal bone of the great toe,
like that of the thuml), is not united
to the others at its base by any inter-
A'ening bands.

The distal ends of the five metatarsal
bones are united by the transverse
metatarsal ligament (p. 210).

Tarsal with metatarsal bones.
These articulations reseml)le the like
parts in the liand, as there is a separate
joint for the great toe, and a common
one for the four outer metatarsals.

Articulatio7i of the great toe. The
articular ends of the bones are encased
by a capsule, and are provided with an
uijper and a lower longitudinal hand to
give strength to the joint : the lower
band is placed between the insertions
of the tendons of the tibialis anticus
and peroneus longus.

A simple synovial sac serves for the
articulation.

The articular surfaces are o\^al from
above down, curved inwards, and constricted in the middle ; that
of the metatarsal bone is excavated, and the other is convex.

Movement. There is an oblique movement of the metatarsal bone
down and in and up and out, like that of the internal cuneiform
with the navicular l)one ; and this will contribute a little to inver-
sion and eversion of the foot.

The joint possesses likewise slight abductory and adductory
movement.

Articulation of the four outer toes. The three outer tarsal bones of
the distal row correspond with four metatarsals, — the middle cunei-
form being opposite the second metatarsal bone, the external cunei-
form touching the third, and the cuboid carrying the outer two
bones. The surfaces in contact are tipped with cartilage, and have
longitudinal dorsal, plantar, and lateral ligaments, with some oblique
in the sole.

The dorsal ligaments (fig. 90) are thin bands of fibres, which are

Fig. 90.— Dorsal Ligaments

UNITING THE TaRSUS TO

THE Metatarsus, and the
Metatarsal Bones to
each other behind
(Bourgery).

LIGAMENTS OF METATARSAL BONES. 231

more or less longitudinal as they extend from the tarsal to the
metatarsal bones. The metatarsal bone of the second toe receives
three ligaments, one coming from each cuneiform bone. The third
bone obtains a ligament from the external cuneiform ; and the
fourth and fifth each have a fasciculus from the cuboid.

Plantar ligaments (fig. 88). There is one longitudinal band from plantar
each of the outer two cuneiform to the corresponding metatarsal ^'S^"^®"*-^ 5
bone ; but between the cuboid and its metatarsal bones there are
only some scattered fibres.

The lateral ligaments are longitudinal ; they lie deeply between lateral liga-
the bones, and are connected with the second and third mefeitarsals : ^^^^^'^ '
they will be better seen by cutting the transverse bands joining the
bases of the bones. To the l)one of the second toe there are two
bands, one on each side ; — the inner is strong and is attached to
the internal cuneiform ; and the outer is fixed to the external cunei-
form bone. The metatarsal bone of the third toe is provided with
one lateral slip on its outer side, which is inserted behind into the
external cuneiform bone.

Oblique plantar ligaments. A fasciculus of fibres extends across oblique
from the front of the internal cuneiform to the second and third ^ ^" *^'
metatarsals ; and from the external cuneiform there is another slip
to the metatarsal bone of the little toe.

Line of the articulation. The line of the articulation between the Line of the

, , , . . . e .-I ^ articulation

tarsus and metatarsus is zigzag, m consequence ol the unequal across the
lengths of the cuneiform bones. To open the articulation, the knife ^^°^-
should be carried obliquely forwards from the tuberosity of the
fifth to the outer side of the second metatarsal bone ; then al)out
two lines farther back for the union of the second metatarsal with
the middle cuneiform ; and finally, half an inch in front of the last
articulation, for the joint of the internal cuneiform with the first
metatarsal bone.

Two synovial cavities are present in these tarso-metatarsal articii- Two syno-

1 ^ . " vial sacs.

latioiis.

There is one between the cuboid and the two outer metatarsals,
which serves also for the adjacent lateral articular surfeces of the
latter bones, but this is not always separate from the following one.

The second is placed in the joint between the external and middle
cuneiforms with their metatarsal bones (third and second), and is
an offset of the common synovial cavity belonging to the articulation
of the navicular with the cuneiform bones (p. 229) : prolongations
from it extend between the lateral articular facets of the second,
third, and fourth (inner side) metatarsals.

Articular surfaces. The osseous surfaces are not flat: for the Form of the
metatarsal bones are undulating, and the tarsal are uneven to fit
into the others.

Movenunt. From the wedge-shaped form of the metatarsal bones. Motion froai
only a slight movement from above down is obtainable ; and this ^ "^^^°^^°'
is greatest in the little toe and the next.

In the little toe there ^is an abductory and adductory motion ; ^vithabduc-
and a small degree of the same exists in the fourth toe. adduction.

232

DISSECTION Of^ THE LEG.

Separate the
bones to see
interosseous
ligaments.

Dissection. All the superficial ligaments having been taken
away, the interosseous ligaments of the tarsus and metatarsus may
be seen by separating forcibly the cuneiform bones from one another

Union of
metatarsus
and pha-
langes, by

two lateral
ligaments,
and inferior:
synovial
sac.

Form of
bones.

Kind of
motion.

Bending
and extend-
ing,

state of
ligaments :

lateral
motion

circular
motion
limited.

Union of the
I)halanges,

Synovial
sac.

bases of the metatarsals from one another. The dissector will find
that, in using force, the bones will sometimes tear sooner than the
ligaments.

Metatarsus with phalanges. These are condyloid joints, in
which the head of the metatarsal bone is received into the cavity
of the phalanx.

Each articulation has an infer im- and two lateral ligaments, as in
the hand ; and the joint is further strengthened above by an ex-
pansion derived from the tendons of the extensors of the toes. A
distinct synovial sac exists in each joint.

Tn the articulation of the great toe there are two sesamoid bones,
which are connected with the inferior ligament.

All these structures are better seen in the hand, where they are
more distinct ; and their anatomy has been more fully described
with the dissection of that part. (See pp. 104 and 105.)

Surfaces of hone. The metatarsal bone has a rounded head, which
is longest from above down, and reaches farthest on the plantar
surface. On the end of the phalanx is a cup-shaped cavity.

Movement. In this condyloid joint, as in the hand, there is
angular motion in four different directions, with circumduction.

Flexion and extension. When the joint is bent, the phalanx
passes under the head of the metatarsal bone ; and when it is ex-
tended, the phalanx moves back beyond a straight line with the
metatarsal bone.

A limit to flexion is set by the meeting of the bones, by the
stretching of the upper part of the lateral ligaments, and b}^ the
extensor tendon ; and to extension, by the tightness of the inferior,
and the lower part of each lateral ligament, and by the flexor
tendons.

Lateral movement. The phalanx passes from side to side across
the end of the metatarsal bone. Its motion is checked by the
lateral ligament of the side from which it moved, and by the
contact with the other digits.

Circumduction, or the revolving of the phalanx over the rounded
head of the metatarsal bone, is least impeded in the great toe
joint ; but these movements in the foot are not so free as in the
hand.

Articulations of the phalanges. There are two interpha-
langeal joints to each toe, except the first.

Ligaments similar to those in the metatarso-i)lialangeal joints, viz.,
two lateral and an inferior, are to be recognised in these articulations.
The joint between the last two phalanges is least distinct ; and
oftentimes the small bones are immovably united l>y osseous sub-
stance. These ligaments receive a more particular notice with the
dissection of the hand (p. 105).

A simple synovial membrane exists in each phalangeal articulation.

ARTICULATIONS OF THE PHALANGES. 233

Articular surfaces. In both phalangeal joints, the nearer phalanx Form of
presents a trochlear surface ; and the distal one is marked by two ^°'^**-
lateral hollows or cups with a median ridge.

Movement. Only flexion and extension are permitted in the two Kind of
phalangeal joints of the toes, as in the hand. motion,

In flexion the farther phalanx glides under the nearer : and in movement
extension the two are brought into a straight line. '

The bending is checked by the lateral ligaments and the extensor state of liga-
tendon ; and the straightening is limited by the inferior ligament '"^" "■
and the flexor tendons.

234

ARTERIES OF THE LOWER LIMB.

TABLE OF THE ARTERIES OF THE LOWER LLMB.

/External pu- f Superficial
( die . .1 Deep.

superficial epigastric
I superficial circumflex
iliac

Deep femoral

,„ ^ , /'AsceudinL'

/External cn-cumflex . J transverse
' (^descending.

. , , / Muscular

internal circunitiex . J articular

1 ascending ,
^ ^ [ transverse .

nrst perforating

second perforating

third perforating

fourth perforating

\ muscular.

■ r Terminal branches.

medullary to femur.

Super-
ficial
femoral

anastomotic -j Superficial branch
( deep branch.

/Upper muscular
upper internal articular
upper external articular
lower intei-nal articular
lower external articular
azygos articular
sural.

\ Popliteal

Anterior tibial

' Recurrent
cutaneous
muscular
internal malleolar
external malleolar
tarsal

metatarsal

first interosseou:

communicating

to deep arch

digital

/ Peroneal

f Three interos-
I seous.

! to great toe and
( half the next.

/'Muscular

I medullary to fibula

1 anterior peroneal ) Termi-

l posterior peroneal j" iial .

\ Posterior tibial . J

medullary to

tibia
muscular
communicating to
peroneal
internal malleolar

( Muscular
( superficial digital.
{ Internal calcaneal
J muscular ( Posterior
I anastomotic | perforating
I plantar arch. 1 digital, for
i three toes
and a half.

internal plantar.

.external plantar.

tlArteries^nre'^bd'omen;"'""'' '''"' '''''' '''''''' ^"'^ '" ^'^ '""^ ^'^l ^>«f«""d^n the Table of

NERVES OF THE LOWER LTMR.

235

TABLE OF THE NERVES OF THE LOWER LIMB.
Iliac branch of ilio-hypogastric.
Ilio-inguinal.

Crural branch of genito-cniral.
External cutaneous.

Accessory

! superficial divi
5. Obturator < sion

( To obturator trunk
to pectineus
( to hip-joint.

i Articular

j muscular

i to plexus in the

thigh and artery
« to skin sometimes.

. To hip joint

I To gracilis
. : to adductor longus

( to adductor brevis.

I deep division

t Muscular .

I articular .
/Muscular .

crural

Superficial por-
tion

deep j)ortion

( To obturator extemus
. - to adductor raagnus

Uo adductor brevis.
. To knee-joint.
. ( To sartorius

\ to pectineus

I middle cutaneous

I internal cuta- \ Anterior and posterior branches.

^ neous . . )

( To rectus— articular
I Muscular . - to vastus extemus— articular . .^„. ^

I -^^"scuiai . ^ ^^ ^^^^^^^ interm.s and crureus-articular.

] internal saphe- ( Branch to plexus over patella
I nous . . I to leg and foot.

1 Superior ( To gluteus medius and minimus
gluteal \ to tensor fascia- femoris.

:eus maximus.

Small ' Inferior pudendal

sciatic (cutaneous t^ gluteal region, thigh, and leg.

4. Great
sciatic

/ Muscular

external i>op-
liteal

b. To obtur- V internal iwp-
ator inter- liteal
nus and
sui)erior
gemellus.

»;. To qua-
dratus fe-
moris and
inferior
gemellus.

. Perfo-
rating
cutaneous.

/To hamstrings

\ to adductor magnus.

/Articular

external cutaneous of leg
peroneal communicating
recurrent articular

musculo-cuta- ( To peronei
neons . • '• cutaneous to foot and toes.

i Muscular
\auterior tibial . - anticular .^.^^
[ cutaneous to two toes,

mScular . . To calf-muscles and poplit4>us.

tibial communi- ^^ ^^^^^^^ .^^^^^ ^^^^^^

'^*'"^ .Muscular . - of toes, and tibialis

\^ posticus,
calcaneo-plantar
I /^ Cutaneous

i , , i muscular

J. ■ *i.„i internal plantar - ^ digital
posterior tibial . | communicating branch.

I Muscular

I / Cutaneous

,-tem.l plantar superficial I tw^d^ta,

I [ eating,

deep part. Muscujar.

CHAPTER V.
DISSECTION OF THE PERINEUM.

Skcition I.

PERINEUM OF THE MALE.

Before the
dissection
pass cathe-
ter.

Place the
body in
position.

and fasten
upwards
the legs.

Pass a staff.

Stitch up
the scrotum

The surface
limits.

Directions. The perineum is allotted to the dissector of the
abdomen, and its examination is made dnring the first three days
that the body is in the dissecting-room. Before the body is placed
in the position suited for the dissection, the student should practise
passing the catheter along the urethra.

Position of the body. For the dissection of the perineum the body
is fixed in the following manner : — While it lies on the back it is
drawn down to the end of the dissecting table till the buttocks
project slightly over the edge, and a block is placed l:)eneath the
pelvis to raise the perineum to a convenient height. The knees
having been bent, the thighs are to be raised upon the trunk, and the
limbs fastened with a cord in their bent position. For this purpose
make one or two turns with the cord round one bent knee (say the
right), carry the cord beneath the table, and, encircling the opposite
limb in the same manner, fasten it finally round the right knee.

Further directions. When the position has been arranged, the
student, standing on the left side of the body, should pass a well-oiled
staff into the bladder. This should be done by holding the penis
with the left hand and guiding the staft' with the right. When the
point of the instrument passes below the pubic arch a resistance will
be felt which is caused by the triangular ligament. The staff, with
the head kept square and in the middle line, should then be depressed
and passed on, but without force. If necessary, the student may
guide the point through the urethra under the pubic arch by the left
forefinger passed into the rectum. The staff should now be fixed in
position, with the point in the bladder, by tieing the handle firmly
over the front of the lower part of the abdomen to the cords on either
side of the body. The scrotum should be drawn well up away from
the perineum and fastened to the staft" above the penis by a stitch
passed through its extremity and tied round the staft'. A small
quantity of tow should then be passed into the rectum, but not so as
to distend it, and the anus neatly stitched up.

Superficial limits and marking. The perineal space in the male is

BOUNDARIES OF THE PERINEUM. 237

limited, on the surface of the body, by the scrotum in front, and by
the thighs and buttocks on the sides and behind.

The skin of this region is of a dark colour, and is covered with The anus.
hairs. In the middle line is the aperture of the anus, which is
behind a line extending from the anterior part of the one ischial
tuberosity to the other. In front of the anus the surface is slightly
convex over the urethra, and presents a longitudinal prominent line
or raphe, which divides the space into halves. Between the anus the raphe,
md the tuberosity of the hip-bone the surface is somewhat depressed hollow on
over the hollow of tlie subjacent ischio-rectal fossa, especially j^ ■'*i*^e of anus,
emaciated bodies.

The margin of the anal aperture possesses numerous converging and folds
folds, but these are more or less obliterated by the position of the ^^'^ "^'^'"? ^

. "^ ^ around that

body and tlie distention of the anus ; and projecting oftentimes through opening,
and around the opening are some dilated veins (ha3morrhoids).

Deep boundaries. The deep boundaries of the perineal space will Bounding
be ascertained, in the progress of the dissection, to correspond with ^^fose'of
the inferior aperture or outlet of the pelvis. The limits are to outlet of
be observed, on a dry or prepared i:)elvis, on which the ligaments ^'^ ^^'''
remain entire ; and the student should trace on the body the
corresponding boundaries with his finger. In front is the symphysis
pubis ; and at the back is the tip of the coccyx, with the great gluteal
muscles. On each side in front is the portion of the hip-bone which
bounds the subpubic arch, viz., from the pubic symphysis to the
ischial tuberosity ; and further back is the great sacro- sciatic ligament
extending from the tuberosity to the coccyx. This region sinks
into the outlet of the pelvis as far~ as the recto-vesical fascia, which
forms its floor.

Form and size. The interval included within the boundaries above porm of the
described is rather heart-shaped, owing to the projection of the coccyx ^P^(^^, and
behind ; and it measures over the surface about four inclies from ments.
before backwards, and three and a half inches between the ischial
tuberosities.

Depth. The depth of the perineum from the surface to the floor, Depth of
which will be revealed in dissection, may be said to be generally *^«spa<=«-
about three inches between the anus and the ischial tuberosity,
but this measurement varies greatly in different bodies ; and it
amounts to about an inch at the fore part, between the pubic bones.

Division. A line from the front of the tuberosity of one side to a line be-
the corresponding point on the other will divide the perineal space tuberosities
into two parts. The anterior half {urethral) contains the root of the divides it
penis and the urethra, with their muscles, and vessels and nerves.
The posterior half {rectal) is occupied by the lower end of the large
intestine, with its muscles, &c.

POSTERIOR HALF OF THE SPACE.

This portion of the perineal space contains the lower end of the contents of
rectum, surrounded by its elevator muscles and the muscles acting ^nal half,

into two.

238

and their

general

position.

Dissection

of external

sphincter

muscle.

Diflference
in cleaning
the ischio-
rectal fossae.

Dissection
of left
ischio-rectal

On right
side, seek
vessels and
nerves.

Situatioi! :

DISSECTION OF THE PERINEUM. j

on the aims. The gut does not occupy, however, the whole of the j
interval between the pelvic bones ; for on each side is a space, the i
ischio-rectal fossa, in which is contained much loose fat, with the
vessels and nerves for the supply of the end of the gut.

Dissection (fig. 91, p. 239 and fig. 92, p. 241). The workers on the |
two sides should dissect in conjunction displaying the muscles on the [■
one side and the nerves and vessels on the other. The skin is to be |
raised from this part of the perineum by the following cuts : — One is
to be made across the perineum at the front of the anus, and is to
extend rather beyond the ischial tuberosity on each side. A second
is to be carried across in the same direction a little behind the tip of
the coccyx, and for the same distance. The two transverse cuts are to
be connected by carrying the knife along the mid-line, and around
the anus. The flaps of the skin thus marked out are to be raised
and thrown outwards from the middle line : in detaching the skin
from the margin of the anus, the superficial fibres of the s])hincter
muscle may be injured if care be not taken, for they are close to
the skin without the intervention of fat. The dissector should trace
the external sphincter backwards to the coccyx, and forwards for a
short distance beneath the skin, and define a fleshy slip on each side
in front and behind to the subcutaneous fatty layer.

The next step is to bring into view the ischio-rectal hollow
between the side of the rectum and the tuberosity of the hip-bone.
On the left side the fat is to be cleaned out of it without reference to
the vessels and nerves, but on the opposite side a special dissection is
to be made of them (fig. 92). To take out the fat from the left fossa,
begin at the outer margin of the sphincter ani, and proceed forwards
and backwards. In front the dissection should not extend farther
than a finger's breadth in front of the anus, while behind it should
lay bare the margin of the gluteus niaximus. On the inner side of
the hollow the levator ani (sometimes very pale) is to be exposed by
the removal of a thin layer of areolar tissue (anal fascia). On the
outer boundary the pudic vessels and the accompanying nerves
should be denuded : they lie in a canal formed by fascia, and at some
distance from the surface.

O71 the right side it is not necessary to clean the muscular fibres
when following the vessels and nerves. If the student begins at the
outer border of the sphincter, he will find the inferior htemorrhoidal
vessels and nerve, which he may trace outwards to the pudic trunks ;
some of the branches, which join the superficial perineal and inferior
pudendal nerves, are to be followed forwards. In the posterior angle
of the space seek a small off'set of the fourth sacral nerve , and
external to it, branches of the perforating cutaneous nerve from the
sacral plexus, with small vessels, turning round the border of the
gluteus. Near the front of the fossa is the superficial perineal artery
with a nerve ; and the last, after communicating with the hsemor-
rhoidal nerve, leaves the fossa. A second perineal nerve, with a deeper
position, may be found at the front of the hollow.

The ISCHIO-RECTAL FOSSA (fig. 91) is the interval between the

ISCHIO-RECTAL FOSSA.

239

•ectum and the ischial part of the hip-bone. It is a somewhat
pyramidal hollow, which is larger behind than before, and diminishes form ;
in width as it sinks on the inner side of the hip-bone. Its width is
ibout one inch at the surface ; and its depth about two inches at the dimensions
outer side. It is filled bv a soft granular fat.

The inner or longest side of the space is very oblique, and is boundaries,
formed by the levator ani muscle (d), together with the coccygeus at
the back ; but the outer side is vertical, and is formed by the obturator

Fig. 91. — The Rectal Half of the Perineum (Illustrations of
Dissections).

Muscles :
a. External sphincter.
B. Corrugator cutis, only part left,
c. Internal sphincter.

D. Levator ani.

E. Glutens maximus.

Arteries :
II. Trunk of the pudic artery.

h. Inferior haemorrhoidal, and c,
its gluteal branches.

Nerves :

1. Inferior hsemorrhoidal.

2. Superficial perineal.

3. Perineal branch of the fourth
sacral.

4. Perforating cutaneous.

internus muscle and the fascia covering it. In front it is limited by
the triangular ligament (to be afterwards seen) ; and behind are the
great sacro-sciatic ligament, and the gluteus maximus muscle.
Towards the surface it is covered by the teguments, and is overlain
in part by the gluteus (e) and the sphincter extern us (a).

Vessels and nerves in the space. Along the outer wall, contained Pudic ves-
in a sheath of fascia, lie the pudic vessels (a) and the perineal and outer "alf
dorsal divisions of the pudic nerve ; opposite the ischial tuber-
osity they are situate about an inch and a half below the surface of
the bone, but towards the front of the space they approach to within

240

and nerves
in the space

First cut in
lithotomy
enters this
space.

Mnscles of
rectum.

Con-ugator
cutis ani :
attacli-
ments :

Superficial
sphincter ;

origin ;

insertion

i-elations :

and use.

Deep

sphincter, a
pale band,

is part of
tibres of
intestine ;

Inseilion of
levator ani

DISSECTION OF THE PERINEUM.

half an inch of the margin of the ischial ramus. Crossing the centre
of the hollow are the inferior haemorrhoidal vessels and nerve (h), —
branches of the pudic. At the anterior part, for a shoi-t distance, are
two superficial perineal nerves {-} (of the pudic) ; and at the posterior
part is a small branch of the fourth sacral nerve p), with cutaneous
offsets of the sacral plexus (^) and inferior hsemorrhoidal vessels (c),
bending round the gluteus.

The surgeon sinks his knife into, this space in the first incision
in the operation of lateral lithotomy : and as he carries it from
before backwards, he will divide the superficial haemorrhoidal vessel
and nerve.

Muscles. Connected with the lower end of the rectum are four
muscles, viz., a fine cutaneous muscle, and two sphincters (external
and internal), with the levator ani.

CoRRUGATOR CUTIS ANI (fig. 91, b). This thin subcutaneous
layer of involuntary muscle surrounds the anus with radiating fibres.
Externally it blends with the subdermic tissue outside the interna
sphincter ; and internally it enters the anus and ends in th
submucous tissue within the sphincter.

Action. This muscle draws upwards and inverts the mucous
membrane of the lower end of the gut, after it has been protruded
and everted in the passage of the faeces.

The EXTERNAL SPHINCTER (sphiucter ani externus ; fig. 91 a and
fig. 92) is a flat, orbicular muscle, which surrounds the anal open-
ing. It arises posteriorly by a fibrous band from the back of the
coccyx near the tip, and by fleshy fibres on each side from the sub-
cutaneous fatty layer. Its fibres pass forwards to the anus, where
they separate to encircle that aperture ; and they are inserted in front
into the central point of the perineum, and into the superficial fascia
by a fleshy slip on each side.

The sphincter is close beneath the skin, and partly conceals the
levator ani. The outer border projects over the ischio-rectal fossa ;
and the inner is contiguous to the internal sphincter.

Action. The muscle gathers into a roll the skin around the anus,
and occludes the anal aperture. CJommonly the fibres are in a state
of involuntary slight contraction, but they may be firmly contracted
under the influence of tlie will.

The INTERNAL SPHINCTER (sphiuctcr ani internus ; fig. 91, c)
is situate round the extremity of the intestine, internal to tlie pre-
ceding muscle, and its edge will be seen by removing the corrugator
muscle and the mucous membrane. The fibres of the muscle are
pale, fine in texture, quite separate from the surrounding external
sphincter, and encircle the anus in the form of a ring about half an
inch in depth. The muscle is a thickened band of the involuntary
circular fibres of the large intestine, and is not attached to the bone.

Action. This sphincter assists the external in closing the anus ;
and its contraction is altogether involuntar3^

The LEVATOR ANI (fig. 91, Dand fig. 92) can be seen only in part ;
and the external sphincter may be detached from the coccyx, in

LEVATOR AN I.

241

order that its insertion may be more apparent. The muscle descends
from its origin at tlie inner aspect of the hip-bone, and is inserted into coccyx
along the middle line from the coccyx to the central point of the f"frj^t1)f"
perineum. The hindmost fibres are attached to the side of the ^^ ;
coccyx ; and between that bone and the rectum the muscles of
opposite sides are united in a median tendinous line. The middle

Corpora cavernosa. Corx^us spongiosum urethrse.

;rior haemor'
loidal nerve,

Crura of the

Inferior Perforating Branch of

hsemorrhoidal cutaneous fourth sacral

artery. nerve. nerve.

Levator ani.

Fig. 92. — Diagram op the Muscles, Nerves and Arteries of the
Male Perineum.

fibres are blended with the side of the rectum. And the anterior into rectum,
are joined with the opposite muscle, in front of the rectum, in the Centre of the
central point of the perineum ; except that some of them will be perineum :
found to be prolonged backwards over the plane of the posterior relations ;
fibres to the tip of the coccyx.

This muscle bounds the ischio-rectal fossa on the inner side, and
unites with its fellow to form a fleshy layer (pelvic diaphragm), con-
vex downwards, through which the rectum is transniitted. On the

D.A. B

242

use on
vectuin.

Arteries of
the space.

Pudic
artery:

course ;

posterior
^art in
tossa ;

depth and
relations.

Branches : —

Inferior

hsemorrhoi-

dal.

Muscular
offsets.

Veins.

Nerves of
the space.

Ridic nerve
divides into
three parts :

inferior

haemorrhoi-

dal;

perineal ;

DISSECTION OF THE PERINEUM.

pelvic aspect of the muscle is the recto-vesical fascia. Along the
hinder border is placed the coccygeiis.

Action. It compresses the lower part of the rectum during the
act of defjKcation.

This muscle will be more fully seen and examined in the dissection
of the pelvis (p. 382).

Arteries (fig. 92). The pudic artery, with its inferior liEemor-
rhoidal branch, and other small offsets of it, are now visible.

The INTERNAL PUDIC ARTERY is derived from the internal iliac
in the pelvis, and in its course to the genital organs distributes
offsets to the perineum ; one portion will be laid bare in the
posterior, and the other in the anteri(jr half of the perineum.

As now seen, the vessel enters the hinder part of the ischio-rectal
fossa, and courses forwards along the outer wall at the depth of one
inch and a half at the back, but of only half an inch in front. It is
contained in an aponeurotic sheath formed by the obturator fascia.
The usual companion veins lie by its side ; and two nerves accom-
pany it, viz., the dorsal nerve of the penis, which is above it, and the
perineal branch of the pudic nerve which is nearer the surface. Its
offsets in this part of its course are the following : —

The inferior hcemorrhoidal branch arises as the artery enters the
ischio-rectal fossa, and is directed inwards across the space to the
anus, dividing into branches which supply the skin and fat, the
levator ani and sphincter muscles, and the lower end of the rectum.
On the gut it anastomoses with the other haemorrhoidal arteries. In
a well-injected body cutaneous branches may be seen to run forwards
to the anterior part of the perineum, and to communicate with the
superficial perineal artery. Other offsets turn upwards round the
edge of the gluteus maximus to the integument of the lower and
inner part of the buttock.

Small muscular branches cross the front of the ischio-rectal fossa,
and supply the anterior part of the levator ani muscle.

Veins accompany the arteries, and have a like course and ramifica-
tion : the pudic veins end in the internal iliac.

Nerves (figs. 91 and 92). The nerves seen at this stage of the
dissection are the three divisions of the pudic trunk, a branch of the
fourth sacral nerve, and the perforating cutaneous offset of the sacral
plexus.

The PUDIC nerve is derived from the sacral plexus, and lies over
the small sacro-sciatic ligament with the artery in the buttock.
In the small sacro-sciatic foramen the nerve breaks up into the
three following branches, which enter the perineum : —

The inferior hcemorrhoidal branch crosses the ischio-rectal fossa,
and reaches the margin of the anus, where it terminates in offsets to
the integument and the sphincter muscle. Other cutaneous offsets
of the nerve run forwards over the fossa, and communicate with one
of the superficial perineal nerves, and with the inferior pudendal
(of the small sciatic) on the margin of the thigh.

The perineal branch is the largest of the three divisions, and runs

SUPERFICIAL FASCIA OF ANTERIOR HALF. 243

; wards in a sheath of the obturator fascia, lying below the piidic
-sels. At the fore part of the ischio-rectal fossa it divides into
raneous, muscular, and genital offsets. Its two cutaneous branches
uperficial perineal) may be seen on the right side, where they lie

for a short distance in the fat of the hollow.

The dorsal nerve of the penis accompanies the pudic artery along and dorsal

the outer side of the ischio-rectal fossa to the fore part of the peri- penis.

neum. It is also enclosed in the obturator fascia, but is deeper than

the blood-vessels.

The PERINEAL BRANCH OP THE FOURTH SACRAL NERVE reaches Offset of

the ischio-rectal fossa between the levator ani and coccygeus, or by nerve,
piercing one of these muscles, near the coccyx, and ends by supplying
the external sphincter.

The PERFORATING CUTANEOUS NERVE is au offset froui the lowest Perforating

part of the sacral plexus, and is named from its piercing the great nerve,
sacro-sciatic ligament in its course to the perineum. Turning up-
wards round the lower edge of the glutens maximus, its branches
are distributed to the skin of the inner and lower part of the gluteal
region.

ANTERIOR HALF OF THE PERINEAL SPACE.

In the anterior part of the perineal space are lodged the crura of Urethral
the penis, and the tube of the urethra as it courses from the interior * ,

COTl'tdlLS

of the pelvis to the surface of the body. Placed midway between the and general
bones, the urethra is supported by the triangular ligament of the ^^5'*^" °*^
perineum, and by its union with the penis.

Muscles are collected around the urethra and the crura of the penis :
most of these are superficial to, but one is within the triangular
ligament.

The vessels and nerves lie along the outer side, as in the posterior
half, and send offsets inwards.

Dissection (figs. 92 and 93). To raise the skin from the anterior Incisions to
half of the perineum, a transverse cut is to be made at the back of the skin,
scrotum, and is to be continued for a short distance (two inches) on
each thigb. A second incision along the middle line from the one
already made will allow the flap of skin to be reflected outwards.

After the removal of the skin, the superficial fascia which covers Blow up
the front of the perineal space should be blown up by means of a Sla, and
pipe attached to an ordinary cycle inflating pump or a pair of bellows, reflect it.
introduced beneath it posteriorly. Each side should be gently
inflated separately to demonstrate the fact that there is a partition
along the middle line. It will be seen that the air does not pass
from the perineal space into the thigh, showing that the fascia is
attached to the bony margins of the space.

The student is next to cut through the superficial fascia on the left
side of the scrotum to the ischio-rectal fossa; and after reflecting
it, and removing loose fatty tissue, its line of attachment to the bone
externally, and to the triangular ligament posteriorly, will be brought
into view. The septum along the middle line should be also defined.

R 2

244

Define parti-
tion be-
tween tliigh
and perineal
space.

On right
side seek
inferior
pudendal
nerve.

Superficial
fascia :

subcuta-
neous part

and mem-
branous
layer.

The latter
forms a
pouch, open
in front ;
and divided
by a septum

Course of
air and

effused

Dissection
of nerves
and vessels
on right
side.

Superficial
vessels of
jmdic.

DISSECTION OF THE PERINEUM.

To show more completely the attachment of this layer to the hip.
bone between the perineal space and the thigh, it will be necessary to
take away from the left limb the fat on the fascia lata, external to the
margin of the bone.

In the fat of the thigh on the right side the student should seek
the inferior or long putlendal nerve (fig. 92), which pierces the fascia
lata one inch in front of the ischial tuberosity, and about the same
distance from the margin of the bone ; and he should trace its junc-
tion in the fat with the inferior haemorrhoidal nerve. Afterwards the
nerve is to be followed forwards to where it passes beneath the
superficial fascia nearer the middle line.

The superficial fascia of the anterior half of the perineum is com-
posed of two layers, which differ in their characters and relations.

One is the subcutaneous fatty part, continuous with that of the
adjoining regions : its thickness, and the quantity of fat in it vary
with the condition of the body. Passing in front into the scrotum,
it there loses its fat, and contains involuntary muscular fibres, forming
the layer known as the tunica dartos.

The other layer (fascia of CoUes, and beneath which the air was
injected) is a more membranous stratum of limited extent, and is con-
nected with the firm subjacent structures. Externally it is fixed to the
conjoined rami of the ischium and pubis, outside the line of the crus
penis and its muscle, extending as far back as the ischial tuberosity.
Posteriorly this layer bends upwards to join the triangular liganient
of the urethra ; but in front it is unattached, and is continued to the
scrotum and penis. By means of the connections of the mem-
brane on both sides, a space is enclosed over the anterior half of the
perineum. From its deep surface a septum extends upwards in the
. middle line, and divides posteriorly the subjacent space into two:
but anteriorly this partition is less perfect, or niay disappear.

Air blown beneath the fascia passes forwards to the scrotum ;
which is the only possible direction owing to the deep connections
of the membrane with parts around. Should urine be effused
beneath the superficial fascia, the fluid will be directed forwards,
like the air, through the scrotum to the penis and the front of the
abdomen.

Dissection. The superficial vessels and nerves are to be dissected
on the right side of the perineum, by cutting through the super-
ficial fascia in the same manner as on the left side. The long
slender artery then visible is the superficial perineal, which gives
a transverse branch near its commencement. Two superficial peri-
neal nerves accompany the artery ; and the inferior pudendal nerve
is to be traced forward to the scrotum. Communications are to be
sought between these nerves anteriorly, and between one of the
perineal and the inferior haemorrhoidal posteriorly ; and all the
nerves are to be followed backwards (figs. 92 and 93).

Arteries (figs. 92 and 93). The superficial and transverse perineal
arteries beneath the fascia are bianches of the pndic, and are two or
three in number.

SUPERFICIAL PERINEAL ARTERY.

245

The superficial perineal artery, arising at the fore part Superficial

the ischio-rectal fossa, runs over or under the transverse 1'"''°^
i>cle. and beneath the superficial fascia, to the back of the
lotum, where it ends in flexuous branches. In its course through ends in

the perineum the vessel supplies offsets to the muscles beneath ; ^^^° "*"'

iuid in the scrotum it anastomoses with the external pudic branches muscles.

of the femoral artery. Sometimes there is a second perineal

branch.

The transverse artery of the perineum arises from the Transverse

preceding, and is directed transversely to the middle of the perineal * ^^'

Fig. 93. — The Anterior Half of the Perineum (Illustrations of
Dissections).

Arteries :

a. Transverse perineal.

b. Superficial perineal.

Muscles, d'C. :
Ejaculator urina.
Erector penis.
Transversus perinei.
Levator ani.
Gluteus maximus.
Crus penis.
Urethra.

Xerves :
1. Inferior Laeniorrhoidal.
2 and 3. Superficial perineal.
4. Inferior pudendal.

space, where it is distributed to the integuments and the muscles
between the urethra and the rectum. It anastomoses with the
one of the opposite side.

Branches of veins accompany the arteries, and open into the Veins with
trunk of the pudic vein ; those with the superficial perineal artery
are plexiform at the scrotum.

Nerves (figs. 92 and 93). Three nerves run forwards to the Cutaneous
scrotum on each side, viz., the inferior pudendal of the small sciatic, scrotum,
and two superficial perineal branches of the pudic nerve.

246

DISSECTION OF THE PERINEUM.

iwo suijer-
ficial peri-
neal ;

external

and internal;

distributed
to scrotum
and penis.

Muscular
branches.

Inferior

pudendal

nerve

ends in
scrotum.

Dissection
of muscles
of the

urethra and
penis,

and of their
nerves.

Three
muscles
over tri-
angular
ligament.

Central
point,

where

muscles

join.

Erector
penis :

origin ;

insertion

The superficial perineal nerves, two in number, are named
external and internal : both arise in the ischio-rectal fossa from the
perineal division of the pudic nerve (p. 242).

The external branch is continued forwards, beneath the super-
ficial fascia, with the artery of the same name to the back of the
scrotum. While in the fossa the nerve gives inwards an offset to
the integuments in front of the anus ; and this communicates with
the inferior hsemorrhoidal nerve.

The internal branch passes under the transverse muscle, and
accompanies the other to the scrotum.

The superficial perineal branches communicate with one another,
and the external is joined by the inferior pudendal nerve. At the
scrotum they are distributed by long slender filaments, which reach
as far as the under surface of tlie penis.

Other muscular branches of the perineal nerve will be afterwards
examined (p. 248).

The inferior or long pudendal nerve is a branch of the
small sciatic. It pierces the fascia lata about one inch in front of
the ischial tuberosity, and enters beneath the superficial fascia of the
perineum, to end in the outer and fore parts of the scrotum.
Communications take place between this nerve, the inferior
hsemorrhoidal; and the outer of the two suj)erficial perineal
branches.

Dissection. For the display of the muscles, the superficial fascia,
as well as the vessels and nerves of the left side, must be taken
away from the anterior half of the perineal space. Afterwards a
thin aponeurotic layer is to be removed from the surface of the
muscles. Over the middle line lies the ejaculator urinse, or bulho-
cavernostis ; along the outer edge of the space is the erector penis, or
ischio-cavernosus ; and behind, passing obliquely between the other
two, is the transverse muscle.

On the right side the student should seek the branches of the
perineal nerve to the muscles.

Muscles (figs. 92 and 93). Superficial to the triangular ligament,
in the anterior half of the perineal space, are the three muscles, viz.,
the erector penis, the ejaculator urinse, and the transversus perinei.
Another muscle of the urethra is contained between the layers of
the triangular ligament, and will be subsequently seen.

Central point of the perineum. Between the urethra and the rec-
tum is a small transverse tendinous septum, to the centre of which
this name has been applied. It is j^laced about one inch in
front of the anus, and in it the muscles acting on the rectum
and urethra are united. Its development varies greatly in difi'erent
bodies.

The erector penis (ischio-cavernosus) is the most external of
the three muscles, and is narrower at each end than in the middle. It
covers the crus penis : and its fibres arise from the ischial tuberosity
farther back than the attachment of the penis, and from the bone on
each side of the crus (p. 251). In front, the muscle is inserted into an

SUPERFICIAL MUSCLES OF ANTERIOR HALF. 247

neurosis over the inner and outer surfaces of the crus penis. It
> on the root of the penis and the bone.

Adion. The muscle compresses the crus penis against the sub- use
nt bone, and retards the escape of the blood from the corpus
ernosum by the veins, and in that way it contributes to the

-ction of the organ.

The EJACULATOR URIN^E (bulbo-cavernosus) lies on the urethra, Ejacuiator
The muscles of opposite sides arise from a median tendinous raphe
for 2| inches along the middle line, and from the central point of the
perineum. The fibres are directed outwards, curving round the con- origin at
vexity of the urethra, and give rise to a thin muscle, which has the
following insertion : — The hindmost fibres end on the lower surface of
the triangular ligament. The anterior fibres, which are the longest and
best marked, are inserted into the penis on its outer aspect, in front insertion by
of the erector and send a tendinous expansion over the dorsal vessels « P* ^ ,
of the penis. The intervening fibres, forming the greater part of the
muscle, turn round the urethra, surrounding it for two inches, and
join their fellows in a common tendon (fig. 92, p. 241),

The ejacuiator muscle covers the bulb and the corpus spongiosum surrounds
for nearly three inches below and in front of the triangular liga- ^^^^ '
ment. If the muscle be cut through on the left side and turned
off the urethra, the junction with its fellow above the tube will be
apparent.

Action. The two halves, acting as one muscle, can compress the use,
urethra, and forcibly eject its contents. During the flow of fluid in
micturition the fibres are relaxed, but they come into use at the end voluntary
of the process, when the jiassage has to be cleared. The action is and invoiun-
involuntary in the emission of the semen. ^'^'

The TRANSVERSUS PERIXEI (fig. 93, C) is a small thin muscle, Transyeraus

which lies across the perineum opposite the base of the triangular ^"°^^ "
ligament. Arising irom the inner side of the ischial tuberosity at origin ;
the fore part (fig. 92, p. 241), it is inseiied into the central point of ends in
the perineiun with the muscle of the opposite side, and with the point;
sphincter ani and the ejacuiator urinse. In a well-developed muscle
some of the fibres are partly continuous with the opposite part of the
external sphincter. Behind this muscle the superficial fascia curves
round to join the tinangular ligament.

Action. From the direction of the fibres the muscle will draw "^e.
backwards the central point of the perineum, and help to fix it pre-
paratory to the contraction of the ejacuiator.

Sometimes there is a second small fleshy strip in front, of the Accessory
transversalis, which has been named transversalis alter; this throws ,^sck.
itself into the ejacuiator muscle.

Triangular space. The three muscles above described, when a triangular
separated from each other by dissection, limit a triangular space, tween the
of which the ejacuiator urinse forms the ijiner boundary, the erector mi^cies-
penis the outer side, and the transversus perinei the base. In the
floor of this interval is the triangular ligament of the urethra, with the knife
the superficial perineal vessels and nerves. The knife entering the ""^^ ^"'^*'"

248

DISSECTION OF THE PERINEUM.

in litho-
tomy.

Perineal
nerve has

cutaneous,
muscular,

and genital
branches.

Dissection
of triangular
ligament.

Triangular
ligament
of urethra :

attach-
ments,

and rela-
tions ;

consists of
two strata :

apertures in
it for
urethra,

for arteries
and nerves
of penis ;

parts

between

layers.

posterior part of this space during the deeper incisions in the lateral
operation of lithotomy will divide the transverse muscle and artery,
and probably the superficial perineal vessels and nerves.

The PERINEAL BRANCH OF THE PUDIC NERVE (p. 242) breaks

up in the fore part of the ischio-rectal fossa into superficial and deep
branches. Its two superficial offsets have been followed to the
scrotum (p. 246). The deep branches are muscular to the fore parts
of the external sphincter and levator ani, to the transversus perinei,
erector penis, and ejaculator urinse, and the nerve to the bulb, a long
slender branch, which jDierces the last muscle and, dividing into
filaments, enters the hinder portion of the corj^us spongiosum.

Dissection (fig. 94). For the display of the triangular ligament,
the muscles and the crus penis, which are superficial to it, are to be
detached on the left side in the following way ; — the ejaculator urinse
is to be removed completely from the corpus spongiosum and the
surface of the ligament, and the erector muscle from the crus of the
penis. Next, the crus penis is to be detached from the bone ; but
this must be done with care so as not to cut the triangular ligament
nor to injure the terminal branches of the pudic artery and the dorsal
nerve of the penis near the pubic ramus.

The TRIANGULAR LIGAMENT OF THE URETHRA (deep perineal
aponeurosis ; fig. 94, c) occupies the anterior part of the sub-pubic
arch, and is about one inch and a half in depth in the middle line.

On each side it is fixed to the pubic and ischial rami beneath the
crus penis. Its base is turned towards the rectum, and in the
middle line is united with the central point of the perineum ; wliile
laterally it is free and sloped towards the bone, so that the ligament
is deeper at the sides than in the centre. Superficial to it are the
bulb of the corpus spongiosum and the crura of the penis, with the
muscles of the anterior half of the perineal space ; and the super-
ficial fascia joins it along the hinder border. From its deep surface
some fibres of the levator ani arise ; and the thin anal fascia is con-
tinued backwards from the ligament over that muscle in the ischio-
rectal fossa.

The ligament is composed of two layers of membrane (superior and
inferior) which are united along the base. The superior layer is
derived from the fascia of the pelvis. The infeiior layer (now seen)
is a separate membrane, formed chiefly of transverse fibres ; but it
is so thin as to allow the vessels and the muscular fibres to be seen
through it.

Perforating the inferior layer of the ligament, about one inch from
the symphysis pubis, is the canal of the urethra ; but the margin of
the opening giving passage to that tube is blended with the tissue
of the corpus 8j)ongiosum. Nearer the symphysis, and close to the
bone on each side, the terminal part of the pudic artery and the
dorsal nerve of the penis (b and 3) perforate the ligament by separate
apertures.

Between the layers of the ligament are contained the membranous
part of the urethra, the constrictor urethras muscle, Cowper's glands.

CONSTRICTOR URETHR.E.

the bulb, and the dorsal

249

the pudic vessels with their branches to
nerves of the penis.

Dissection. The muscle between the layers of the ligament will Dissection,
be reached by cutting through with care, on the left side, the
exposed stratum near its attachment to the bone, and raising and
turning it inwards. By a little cautious dissection, and the removal

Fig. 94.-

-Deep Dissection of the Perineum (Illustrations of
Dissections).

Muscles, (L-c. :

A. Erector penis.

B. Ejaculator urinae, cut.

c. Triangular ligament, inferior
layer.

D. External sphincter.

F. Bulb of corpus spongiosum.

6. Levator ani.

H. Superior layer of triangular
ligament.

I. Constrictor urethrse.

K. Crus penis, cut.

Arteries :

a. Pudic, in the triangular
ligament.

b. Dorsal of penis.

c. Cavernous.

(/. Deep muscular branch.

Nerves :

1 and 3. Dorsal of penis.
2. Perineal branch, giving offset
to biilb.

of some veins, the Heshy fibres of tlie constrictor urethrse will be
exposed.

The CONSTRICTOR URETHRA (fig. 94, i) extends transversely across Constrictor
the sub-pubic arch, enclosing the membranous part of the urethra in ""* "^ '
the same way as the sphincter ani externus surrounds the end of the
rectum. The muscle is attached by tendinous bundles on each side attach-
to the rami of the pubis and ischium, and other fibres spring from the ™^" '' '

two layers of the triangular ligament. Between these attachments disposition

of fibres.

the fleshy fibres are directed transversely and obliquely across the
middle line, one set passing in front of, and another behind the

250

DISSECTION OF THE PERINEUM.

Transverse
ligament.

Deep

transverse

muscle.

Use of
constrictor.

Circular
fibres of
urethra,

from the
prostate to
the bulb :

Cowper's
glands :

situation,
size, and
structure

length and
termination
of the duct

they ^'ary
in size.

Dissection
of vessels
and nerve.

Pudic
artery :

course and
ending.

urethra, where they are interrupted in some cases by a small median
tendon. At the anterior border of the muscle there is a short fibrous i
bancl stretching across between the inferior rami of the pubic bones,
and bounding, with the sub-pubic ligament at the lower margin of the
symphysis, an oval opening, through which the dorsal vein of the-
penis enters the pelvis. The hindmost fibres of the constrictor are'
connected with the central point of the perineum, and are sometimes
described separately as the transversus j^erinei profundus.

Action. This muscle acts as a sphincter in narrowing the
membranous part of the urethra, and ejecting the contents of the
tube. It may also aid in producing erection of the penis by com-
pressing the veins of the corpora cavernosa, which are surrounded by '
its fibres.

Involuntary circular fibres within the constrictor muscle surround
the urethra from the bulb to the prostate, and form a layer about
ifh of an inch thick ; they are not fixed to bone, and are con-
tinuous above with the circular fibres of the prostate. This layer is
a portion of the large involuntary muscle, of which the prostate
contains the chief part, surrounding the beginning of the urethra.

Action. This involuntary layer assists in forcing forwards the
urine and the semen.

The glands of Cowper will be found by cutting through some
of the hinder fibres of the constrictor muscle. They are situate
behind the membranous part of the urethra, one on each side of the
middle line, and close above the bulb. Each gland is about the size
of a pea, and is made up of small lobules. They are hard to the feel
and can often be located by grasping a portion of the surrounding
muscle in the forceps before its removal.

Connected with each is a minute duct, an inch or more in length,
which perforates obliquely the wall of the urethra (corpus spongiosum),
and opens into the canal about three-quarters of an inch in liont of
the triangular ligament. Its aperture in the ordinary state does not
admit a bristle.

These bodies are sometimes so small as to escape detection, and
they appear to decrease in size with advancing age.

Dissection. The student should now trace out on the right side
the pudic vessels with their remaining branches, and the dorsal nerve
of the penis. From the point of its division beneath the crus into
two branches (dorsal of the penis, and cavernous), the artery is to be
followed backwards along the bone ; and the nerve will be found by
the side of, but deeper than the artery.

The INTERNAL PUDIC ARTERY has already been dissected in the
posterior half of the perineum (p. 242). At the front of the ischio-
rectal fossa it penetrates the base of the triangular ligament, and then
runs forwards close to the edge of the hip-bone (fig. 94, a), in a canal
formed by the tendinous origin of the constrictor urethroe. About
half an inch behind the symphysis pubis it pierces the inferior layer
of the ligament, and immediately divides into the arteries of the
corpus cavernosum and the dorsum of the penis. It is accompanied by

INTERNAL PUDIC ARTERY. 251

/enae coiuites and the dorstil nerve of the penis. Its offsets in this Branches :—
i Dart of its course are : —

^ a. Deej) muscular hranches (d). As the artery is about to enter Muscular.
^ between the layers of the triangular ligament it furnishes one or
* more branches to the levator ani and sphincter, and fine twigs through

the ligament to the constrictor and the urethra.

b. The artery of the bulb is a branch of considerable size, which Artery of
arises near the base of the triangular ligament. It passes almost ^rian^iiar^
transversely inwards between the filjres of the constrictor muscle, ligament:
about half an inch from the base of the triangular ligament, and
reaches the upper surface of the bulb to enter the spongy struc-
ture. Xear the urethra it furnishes a small branch to Cowper's

gland.

The distance of this branch from the base of the ligament will its situation
influenced by its origin being nearer the front or back of the ^*"®^-
neal space. If it arises earlier than usual it may be altogether
hind the ligament and cross the front of the ischio-rectal fossa,
fio as to be liable to be cut in the operation of lithotomy.

c. The artery of the corpus cavernosum (c) is one of the terminal Artery of
branches of the internal pudic. At first this vessel lies between ^j^.*^^
the crus penis and the bone, but it soon enters the crus, and ramifies

in the cavernous structure of the penis.

d. The dorsal artery of the penis (Ji) is in direction the continuation Artery of
of the internal pudic ; it runs upwards between the crus and the pg^^^"" °^
bone, and reaches the dorsum of the penis by passing through its
suspensory ligament. Its distribution with the accompanying nerve

will be noticed directly.

Accessory pudic artery. In some cases the pudic artery is not large Accessory
enough to supply the branches above described to the penis and the urethra, pudic
One or more oftsets will then be contributed by an accessory vessel, which ^"*^>' •
leaves the pelvis in front by piercing the triangular ligament. The source of source,
this accessory artery is the internal iliac (p. 399).

The pudic veins, two in number, have frequent communications Pudic
together, so as to form a plexus round the artery ; they receive ^®^"^'
similar branches, except that the dorsal vein of the penis does not
join them.

The DORSAL XERVE OF THE PENIS haS been seen in the ischio- Dorsal ner\'e

rectal fossa (p. 243). In the anterior half of the perineum it takes a °^ * ^^ ^^^'^'
similar course to the pudic artery, but at a deeper level and in a
distinct sheath within the triangular ligament, and then pierces the
superficial layer of that structure close to the inferior ramus of the
pubis, to be continued with the dorsal artery to the penis. On its
way the nerve supplies filaments to the constrictor urethrse muscle.

Dissection. The ejaculator urinse muscle will now be carefully
cleared away from the subjacent bulbous and spongy part of the
urethra, and the erector penis muscles will be similarly removed to
fully expose the crura.

The CRURA OF THE PENIS are attached on each side to the conjoined crura of
rami of the pubis and ischium for about an inch, and it will be seen l'^"*^-

is thin, and
without fat,

252 DISSECTION OF THE PEEINEUM.

that they are the pointed posterior extremities of two dense cylindrical
tabes of fibrous tissue (the corpora cavernosa) containing erectile
tissue, which blend about an inch and a half from their posteriori
extremities to form the body of the penis. A slight enlargement
will be noticed on each crus, which has been called the bulb of thai
corpus cavernosum (Kobelt). The structure of the corpora cavernosa!
will be seen at a later stage.
Bulb of The BULB OF THE URETHRA is an enlargement of the vascular and

lire nu. erectile tissue {the coiyus spongiosum) which surrounds the urethral
from the triangular ligament onwards. The bulb is firmly united to i
the under surface of the triangular ligament and usually presents a
slight central depression, with a bulging on each side forming two
lateral lobes.

Tegumeu- CUTANEOUS COVERINGS OF THE PENIS AND SCROTUM. The peuis

i^n^^of p^e^ifs ^^ attached to the front of the pelvis by a suspensory ligament, and
is provided with a tegumentary covering continuous with that of the
abdomen, but devoid of fat.

Around the end of the penis it forms the loose sheath of the
prepuce in the following way : — When the skin has reached the
extremity, it is reflected backw^ards as far as the base of the glans,
forms constituting thus a sheath with two layers — the prepuce ; it is after-

prepuce, wards continued over the glans, and joins the mucous membrane of
the urethra at the orifice on the surface. At the under part of the
glans and behind the aperture of the urethra, the integument forms
andfiwnum. a small triangular fold, frcenum prcepiitii.

Sebaceous Where the skin covers the glans, it is inseparably united with
glands. ^jjg^^ pg^j.^.^ |g ^gj.y ^YiirL and sensitive, being provided with papilla},
and assumes in some cases the characters of a mucous membrane.
Behind the glans are some sebaceous follicles — glandnlce odoriferce.
Teguments In the scrotum the two layers of the superficial fascia of the groin
become united in a thin membrane of a reddish colour. The pro-
longation around the testicle on one side is separate from that on the
other side ; and the two pouches, coming in contact in the middle
line, form the septum scroti.
Muscular The subcutaneous layer in the scrotum, penis, and front of the

fascir "^ perineum contains involuntary muscular fibres, to which the corru-
gation of the skin is owing. This contractile structure is named
the dartoid tissue.
Dissection Dlssectloil. The scrotum should now be accurately divided into
and^nerves. ^"^^ halves by an incision in the middle line and each half containing
its testis is to be held aside. The incision should be continued
along the under surface of the penis to the fr^enum and the skin of
the organ dissected off as a sheath. The staff is to be removed from
the urethra and the fatty tissue from the root of the penis and the
front of the symphysis pubis should be removed so as to define the
suspensory ligament. The dorsal arteries and nerves, with the
dorsal vein of the penis, which will be laid bare, are to be
followed forwards to the glans.
Suspensory The suspeusory ligament of ilte penis is a band of fibrous tissue

THE PENIS. 253

of a triangular form, which is attached by its apex to the front of ligament of
tlie symphysis pubis. Widening below, it is fixed to the upper P^"'^'
surface of tlie body of the penis, and is prolonged for some distance ments ;
on the organ. Perforating the ligament at its junction with the contains
penis are the dorsal vessels and nerves. uenS *°^

The DORSAL ARTERY, ou each side, pierces the suspensory liga- Dorsal
nient, and extends forwards to the glans, where it ends in many arte.ry of
branches for that structure : in its course the vessel supplies the
integuments and branches to the body of the penis.

The DORSAL VEIN is a single trunk, and commences by numerous Dorsal vein
branches from the glans penis and the prepuce. It runs backwards, prostatic
between the two arteries, through the suspensory ligament, and then plexus,
through a special opening below the sub-pubic ligament, to join the
prostatic plexus of veins. The vein receives branches from the
erectile structure and from the integuments of the penis.

Each DORSAL NERVE takes the same course as the artery, and ends Dorsal nerve
like it in numerous branches to the glans penis. It furnishes twigs ^^ ^" ^^'
to the corpus cavernosum penis, and other offsets to the integuments
of the dorsum, sides, and prepuce of the penis.

In the female these vessels and nerves are much smaller than in Vessels on
the male, and occupy the upper surface of the clitoris — the organ *^^'*^"^-
that represents the penis.

The BODY OF THE PENIS is rather prismatic in shape. The upper forms and
surface is slightly grooved along the middle line ; and the lower ^
rounded border is formed by the corpus spongiosum, which is
received into a groove between the corpora cavernosa.

The carpus spongiosum urethrce encloses the urethral canal beyond Corpus
the triangular ligament, and forms the head of the penis. It is a ^P°°siosi"n.
vascular and erectile texture, like the corpora cavernosa, but is
much less strong. Commencing posteriorly in the bulb, it extends J^ethri*^and
forwards around the urethra to the extremity of the penis, where it swells into
swells into the conical glans penis. and the '

The qlans penis is somewhat conical in form, and covers the trun- conical

-, I f 1 T t ■ t glans penis.

cated ends of the corpora cavernosa. Its base is directed backwards,
and is marked by a slightly prominent border — the corona glandis;
it is sloped obliquely along the under aspect, from the apex to the
urinarius base. In the apex is the vertical slit (meatus) in which
the urethral canal terminates, and below that aperture is an excava-
tion which holds the fold of skin named the frcenum prceputii.

Direct ion. The student should be careful not to damage the
urethra, as it will be examined at a later stage.

Parts cut in the lateral operation of lithotomy. This Parts cut in
operation for stone in the bladder may be divided into three stages, ^^ ° ^''
viz., cutting down to the urethra, opening the canal, and slitting
the tube and the neck of the bladder. In the external incision the in cutting
knife is entered near the middle line of the perineum, one inch in Sethra^
front of the anus, and is drawn backwards on the left side as far
as midway between the ischial tuberosity and the anus. The skin
and fat, the transverse perineal muscle and artery, the inferior

254

in reaching
the staff,

and in run-
ning knife
along staff.

Parts to be
avoided are
rectum,

pudic
vessels.

artery of
bulb,

recto-

vesical

fascia,

and acces-
sory pudic
artery.
Directions.

DISSECTION OF THE PERINUEM.

hsemorrhoidal vessels and nerve lying across the ischio-rectal fossa,
and possibly the superficial perineal vessels and nerves, will be ciitj
in this first stage of the operation.

In the subsequent attempt to reach the staff, when the knife is
introduced into the front of the wound, the hinder part of the
triangular ligament and constrictor urethron, and the fore part of
the levator ani will be divided ; when the knife is placed within
the groove of the staff, the membranous part of the urethra will be
cut with the muscular fibre about it.

Lastly, as the knife is pushed along the staff into the bladder, it
incises in its progress the membranous portion of the urethra, part
of the prostate with large veins around it, and the neck of the
bladder. When the last two parts are being cut, the handle of the
knife is to be raised, and the blade depressed ; and the incision is
to be made downwards and outwards, in the direction of a line from
the urethra through the left lateral lobe of the prostate, above the
level of the ejaculatory duct.

Parts to be avoided. In the first incision in the ischio-rectal fossa,
the rectum may be cut if the knife is turned inwards across the
intestine, instead of being kept parallel with it ; and if the gut is
not held out of the way with the forefinger of the left hand. The
pudic vessels on the outer wall of the ischio-rectal fossa may be
wounded near the anterior part of the hollow, where they approach
the margin of the triangular ligament ; but, posteriorly, they are
securely lodged inside the projection of the ischial tuberosity.

While making the deeper incisions to reach the staff, the artery
of the bulb lies immediately in front of the knife, and will be
wounded if the incisions are made too far forwards ; but the vessel
must almost necessarily be cut, when it arises farther back than
usual, and crosses the front of the ischio-rectal fossa in its course to
the bulb of the urethra.

In the last stage of the operation the neck of the bladder should
not be incised to a greater extent than is necessary for the extraction
of the stone, lest the recto-vesical fascia separating the perineum
from the pelvis should be divided, and the abdominal cavity opened.
Too large an incision through the prostate may wound also an
nnusual accessory pudic artery on the side of that body.

Directions. When the dissection of the perineum is completed,
the flaps of skin along the under surface of the penis and the two
halves of the scrotum are to be stitched together ; all the parts are
to be carefully wrapped in tow containing preservative, and the body
will be turned on its face for dissection of the back. On the third
day of this dissection the worker on the abdomen will examine the
different layers of the lumbar fascia, and the posterior aponeurosis of
the transversalis made in conjunction with the dissector of the head
and neck.

PERINEUM OF THE FEMALE. 255

Section II.

PERINEUM OF THE FEMALE.

The perineum in tlie female differs from that in the male more Perineum
in the external form than the internal anatomy. On the surface it has^spedal
has special parts distinguishing it, viz., the aperture of the vagina pa^s.
and the surrounding vulva, which occupy the position of the
scrotum in the male.

Surface-marking. — External organs of generation. In the middle ^jP^,j'^"'^'^-^^
line there are the aperture of the anus and the cleft of the vulva, vuiva.
which are separated from one another by an interval of about an
inch. The anus is situate a little further back than in the male.

The cleft or rinia of the vulva is bounded at the sides by the External

labia majora, two prominent folds, thick and rounded in front but ^^*^'*-

becoming thinner as they pass backwards, which correspond to the

scrotum of the male. The labia are formed externally by skin,

which is provided with scattered hairs, and internally by mucous

membrane. They are united in front and behind in the anterior and and com-
•^ missures.

yostenm' commissures.

Within the rima, at the fore part, is the clitoris, from which two Clitoris,
folds of mucous membrane, the labia minora or mjmphce, extend internal
backwards, one on each side of the aperture of the vagina. At its
anterior end each nympha divides into two smaller folds, the outer
of which unites with the one of the opposite side so as to form a
kind of hood over the front of the clitoris — the prceputium clitoridis, Prepuce and
while the inner one, much shorter and thinner, is attached to the cmoris! °
back of the clitoris in contact with its fellow, the two constituting
the fj'ienulurn clitoridis.

Enclosed by the labia minora, and between the clitoris and the Vestibule,
orifice of the vagina, is a median recess about an inch and a half
deep, which is called the vestibule. At the hinder part of the Opening of
vestibule is the orifice of the urethra (meatiis urinarius), surrounded '^^^^^™-
by a slight eminence, about an inch behind the clitoris, and near
the aperture of the vagina.

The orifice of the vagiiui varies much in size ; and in the child Aperture of
and virgin it is often partly closed behind by a thin semilunar fold ^'^s^a.
of the mucous membrane — the hymen. After the destruction of Hymen and
the hymen, small, irregularly shaped projections, the caruncidce ^^'i^^^®^-
'myrtiformes, are found in its place.

At the back of the rima, within the posterior commissure of the Fourchette
labia, is a narrow transverse fold of the integument called the navicuiaris.
fourchette or frcenulum pudendi ; and to the interval between the
frsenulum and the commissure the name fossa navicuiaris is given.

Deep boundaries. The deep boundaries of the perineum are alike Boundaries
in both sexes; but in the female the outlet of the pelvis is larger both sexes,
than in the male.

256

DISSECTION OF THE PERINEUM.

Dissection.

Take first

ischio-rectal

fossa.

Then
examine
anterior
half ot
perineum.

Superficial
fascia.

Dartoid

tissue.

Superficial
vessels and
nerves.

Dissection
of the
muscles.

Sphincter

origin

Dissection. The steps of the dissection are much the same in
both sexes, and the same description will serve, generally, for the
male and female perineum.

First, the dissection of the ischio-rectal fossa is to be made.
Afterwards the muscles, vessels and nerves of the posterior half of
the perineal space are to be examined. (See description of the
male perineum, pp. 237 to 243.)

Next, the skin is to be taken from the anterior half of the perineal
space, as in the male ; and the transverse incision in front is to be
made at the anterior part of the vulva. The attachments of the

superficial fascia are
then to be looked to,
and the cutaneous ves-
sels and nerves are to
be traced beneath it
(p. 244 et seq.).

S u]) e rji cial fascia.
The description of this
i'ascia in the male will
serve for the like part
in the female, with
these modifications : —
that in the female it
is interrupted in the
middle line, and is of
less extent, in conse-
quence of the aperture
of the vulva ; and that
it is continued for-
wards through the
labia majora to the
inguinal region. Tn
the labia the super-
ficial fascia contains involuntary muscular fibres, like the dartos tunic
of the scrotum, as well as fat.

The SUPERFICIAL PERINEAL VESSELS and NERVES, and the
INFERIOR PUDENDAL NERVE have the Same arrangement as in the
male (p. 245) ; but they are distributed to the labia instead of to
the scrotum.

Dissection. The labia and the superficial fascia are then to be
removed, to follow the sphincter muscle around the opening of the
vagina. Two other muscles are exposed at the same time, viz., the
erector clitoridis lying along the ramus of the ischium, and the
transversus perinei passing across the perineum to the central point.
The SPHINCTER VAGINA (bulbo-cavernosus ; fig. 95, a) is a partially
orbicular muscle around the orifice of the vagina, and corresponds to
the ejaculator urime in the male. Posteriorly it is attached to the
central point of the perineum, where it blends with the sphincter
ani and transversus muscles ; and its fibres are directed forwards on

Fig. 95. — Venous Plexuses op the Genital
Organs, and Opening of the Vagina (Kobblt).

A. Sphincter vaginae muscle.

B. Clitoris,
c. Nyrapha.

a. Bulb of the vestibule.

h. Venous plexus continuous with veins

of the clitoris,
c. Dorsal vein of the clitoris.

THE CLITORIS. 257

each side of the vagina, to be inserted into the body of the clitoris, insertion ;
The muscle covers the bulb of the vestibule and the gland of relations ;
Bartliolin by the side of the entrance to the vagina.

Action. Like the other orbicular muscles, the sphincter diminishes and use.
that part of the vagina which it encircles ; and it assists in fixing
the central point of the perineum.

The ERECTOR CLiTORiDis (ischio-cavemosus) resembles the erector Erector
of the penis in the male, though it is much smaller (see p. 246). ^ " ^ *

The TRANS VERSUS PERiNEi is similar to the muscle of the same Superficial
name in the male. The one description will suffice for the muscle ^gcK^^
in both sexes (see p. 247).

Dissection. The sphincter vaginae should now be carefully
removed from the subjacent bulb of the vestibule, and the erector
muscles from the crura of the clitoris.

The BULB OF THE VESTIBULE (semi-bulb, Taylor, fig. 95, a) is an Bulbs of ^
elongated and flattened mass of cavernous or erectile tissue, which is ^^^ ^ '^
enclosed in a thin fibrous coat. It lies by the side of the vestibule
and the entrance to the vagina, above (deeper than) the nympha, situation ;
resting against the lower surface of the triangular ligament, and relations ;
being covered by the sphincter vaginae muscle (a). Each is about an
inch and a half long, and is larger at its hinder end, where it size ;
measures about half an inch in depth. By their narrow anterior
ends the two bulbs are united in front of the urethra by a small con-
necting venous plexus — the jm^s inteTniediaj and they are joined by connected
a venous plexus to the small glans of the clitoris. These bodies ^ *^^*°"^ »
answer to the divided bulb of the corpus spongiosum urethrtB in
the male.

The CLITORIS (fig. 96, h. p. 258) is a small erectile body, and is the is like the
representative of the penis. It has the same composition as the ^^^^^ '
penis, except that the urethra is not continued along it. Its anterior
extremity is terminated by a rounded part or glans (c), and is covered
by a fold of the mucous membrane corresponding to the prepuce of has a glans
the male. ^J^^'

In its structure this organ resembles the penis in the following composi-
particulars : —It consists of corpora cavernosa, which are attached by *^°"'
crura (one on each side, a) to the ischio-pubic rami, and are blended corpoi-a
in the body. A small suspensory ligament descends to it from the
superficial fascia of the mons Veneris ; and along the middle is an
imperfect pectiniform septum. Moreover, it possesses a portion of
corpus spongiosum, but this structure is limited to the glans corpus
clitoridis (c). (The penis is described on p. 253.) sum ^*^*

Structure. The outer fibrous casing and the septum are alike in and erectile
both penis and clitoris ; and in the interior of the clitoris is an
erectile tissue, like that in the male organ.

The hlood-vessels of the clitoris are like those of the penis, and
the glans receives the dorsal artery (p. 253).

Dissection. To see the triangular ligament of the urethra, the To expose
erector and the crus clitoridis are to be detached from the bone on iJ^an^t.
the left side.

D.A. S

258

DISSECTION OF THE PERINEUM.

Triangular
ligament.

To see deep
muscle.

Deep

transverse

muscle.

The TRIANGULAR LIGAMENT transmits the urethra, but is not so
strongly marked as in the male (see p. 248) ; it is interrupted to a
large extent in the middle line by the aperture of the vagina.

Dissection. By cutting through the superficial layer of the liga-
ment in the same way as in the male (p. 249), the deep muscle, with
the pudic vessels and their branches, and the dorsal nerve of the
clitoris, will be arrived at.

The TRANSVERSUS PERiNEi PROFUNDUS is the representative of the
constrictor urethrae of the male (p. 249). It arises on each side from
the pubic and ischial rami ; and the fibres are directed inwards to be
inserted mainly into the side of the vagina. The hindmost ones join

Fm. 96.— The Clitoris.

a. Crus, and b, body of the corpus cavernosum.
c. Glans clitoridis.

The lower figure shows the structure on a vertical section
letters refer to like parts.

the same

Glands of
Bartholin :

shape and
size ;

duct.

the central point of the perineum ; and anteriorly some are con-
tinued across from side to side in front of the urethra. Beneath the
last is a circular layer of involuntary fibres, as in the other sex.

Glands of Bartholin. At the hinder part of the entrance to the
vagina on each side is a yellowish glandular body, which corresponds
to Cowper's gland in the male (p. 250). It has the shape and size
generally of a small bean, its greatest length, wliich is directed from
before backwards, measuring about half an inch. It lies close to the
hinder end of the bulb of the vestibule, and is covered by the fibres
of the sphincter vagina). The duct is directed forwards and down-
wards for about three-quarters of an inch, to open on the inner
aspect of the nympha of the same side, immediately below the hymen
or its remains.

PUDIC ARTERY. 259

The description of the internal pudic artery (p. 249) will serve Pudic
for both sexes, except that the branch to the bulb is small, and is ^'^ssels.
furnished to the bulb of the vestibule. The terminal branches are
the artery of the corpus cavemosum and the dorsal artery of the
clitoris, and are also much smaller than the corresponding vessels in
the male.

The PUDIC NERVE has the same arrangement as in the male. Pudic nerve.
From its perineal division proceed the two superficial nerves,
branches to the superficial muscles, and an off'set to the bulb. The
dorsal nerve of the clitoris is of small size.

Note. — See the "Directions" at the bottom of page 254.

CHAPTER YI.
DISSECTION OF THE ABDOMEN.

Section I.

WALL OF THE ABDOMEN.

Position of Position. The body will be sufficiently raised by blocks beneath
the body. ^j^g thorax and head for the dissection of the upper limbs and
neck, but the dissector should see that the chest is higher than
the pelvis. If the abdomen is flaccid, it may be inflated through an
aperture in the umbilicus, but if it is firm, proceed with the dissection
without blowing it up.
Appear. Swface-marking. On its anterior aspect the abdomen is fairly

Burface o/^^ uniforndy convex, especially in fat bodies ; but at the side there is
the abdo- a slight hollow below the ribs, and a groove marks the position of
^^^' the iliac crest. Along the middle line is a groove over the linea

alba, which begins above in a depression over the ensiform process
Pit of the (epigastric or infrasteriial fossa), and becoming gradually shallower
stomach. below ends a little beyond the umbilicus. The latter is a round,
*^^ ■ depressed cicatrix, situate nearer to the pubic bones than to the

lower end of the body of the sternum, and opposite, as a rule, the
disc between the third and fourth lumbar vertebrae. On each side
of the median groove is the elevation of the rectus muscle, which
is intersected in adult well-formed bodies by two or three transverse
furrows.
Eminence of Over the lower ends of the recti and the adjacent parts of the
pubes. pubic bones the surface is somewhat elevated, owing to an

accumulation of fat ; and the name puhes has been given to this
part from its thick covering of hair. This projection is especially
marked in front of the bones in the female, where it is distinguished
Mons as the mons Veneris. Beneath the eminence of the pubes the student

will be able to recognise with his finger the symphysis pubis, and
to trace outwards from it the osseous pubic crest, which leads to the
Inguinal prominent pubic spine. From this to the anterior superior iliac
furrow. spine the curved inguinal furrow extends, separating the abdomen
Poupart's from the thigh. If the finger be carried along the furrow it will
ligament. detect the firm band of Poupart's ligament, and sometimes one or

two inguinal glands.
Abdominal Immediately above and to the outer side of the pubic spine the
outer opening of the external abdominal ring may usually be felt ; and in

Veneris.

WALL OF THE ABDOMEN. 261

the male, the prominence of the spermatic cord descending through

it to the testicle. The internal abdominal ring is farther out than and inner.

the external, and cannot be recognised on the surface with the

finger ; its position may be ascertained by taking a point midway

between the symphysis pubis and the anterior superior iliac spine,

and a finger's breadth above Poupart's ligament.

Dissection. The requisite incisions for raising the skin from the Raise the
sides and front of the belly are the following : — One cut is to extend the^front!
outwards over the side of the chest from the ensiform process to
about midway between the sternum and the spine (fig. 1, B.'',
p. 3). A second incision begins at the symphysis pubis, and is
carried outwards along Poupart's ligament and the iliac crest till it
ends opposite the first cut (8). Lastly, the anterior extremities of
the two incisions are to be connected along the middle line of the
belly (3), The jiiece of skin thus marked out is to be raised out-
wards, but is not to be taken away ; and the cutaneous vessels and
nerves are to be sought in the fat at the side and front of the
abdomen.

Along the side of the abdomen look for the lateral cutaneous Position of
nerves (fig. 97, p. 263), five or six in number, which issue in a line nerves^^
with the corresponding nerves of the thorax. At first they lie
beneath the fat, and divide into two ; one offset is to be traced
forwards and the other backwards, with small cutaneous arteries.
On the iliac crest, near the front, is a large branch from the last on the side
dorsal nerve ; and usually farther back on the crest, and deeper, is a
smaller branch of the ilio-hypogastric nerve. Near the middle line and in front,
the small anterior cutaneous nerves wUl be recognised with com-
panion arteries : they are uncertain in number and size, and are
to be followed outwards in the fat.

In the inguinal region the cutaneous vessels and nerves are to be Seek vessels
dissected on the right side, and the superficial fascia on the left.
For this purpose, all the fascia superficial to the vessels is to be
removed from the right groin. The vessels which will then appear
are the superficial external piidic internally, the superficial epigastric
in the centre, and an offset of the superficial circumflex iliac artery-
ex ternally. Some inguinal glands lie along the line of Poupart's
ligament. Two cutaneous nerves are to be sought : — one, the ilio- and nerves
inguinal, comes through the external abdominal ring, and descends aroTn.^*
to the thigh and scrotum (fig. 97, I — i) ; the other, ilio-hypogastric,
appears in the superficial fascia above, and rather outside the
abdominal ring (i-h).

In the examination of the superficial fascia on the left side two Separate
strata are to be made out, one over and one beneath the vessels, left groin
The layer that is superficial to the vessels is to be reflected by means into super-
of a transverse cut directed inwards from the front of the iliac crest,
and by a vertical one near the middle line to the pubic bone. The
subjacent vessels mark the depth of this layer; and when these
are reached, a triangular flap of the fascia is to be thrown towards
the thigh. To define the thinner deep stratum, cut it across in the fa^^^^^

DISSECTION OF THE ABDOMEN.

Superficial
fascia

is divided
into two
layers.

The subcu-
taneous
layer con-
tains fat.

except in
the penis
and scro-
tum.

Deeper
layer is thin
and mem-
branous ;

special cha-
racters and
disposition ;

and ends on
fascia lata.

Attach-
ments deter
mine course
of effused
urine.

Fascia in
the female.

Cutaneous
nerves

are derived
from two
sources.

Lateral
cutaneous of
intercostal,

same manner as the other layer, and detach it carefully with the
vessels from the underlying aponeurosis of the external oblique
muscle. This stratum, like the preceding, is to be traced around
the cord to the scrotum ; and as the student follows it downwards
he will find it connected with Poupart's ligament, and blended with
the fascia lata close below that structure.

• The SUPERFICIAL FASCIA is a single layer over the greater part of
the abdomen ; but in the groin it is divided into a subcutaneous and
a deeper stratum by the vessels and the glands.

The subcutaneous hyer contains the fat, and varies therefore in
appearance and thickness in different bodies ; for it is sometimes
divisible into strata, while in other cases it is very thin, and some-
what membranous near the thigh. It is continuous with the fatty
covering of the thigh and abdomen, and, when traced to the limb,
is separated from Poupart's ligament beneath by the superficial
vessels and glands. Internally it is continued to the penis and
scrotum, where it changes its adipose tissue for involuntary mus-
cular fibre ; and after investing the testicle it is prolonged to the
perineum.

The deeper layer (fascia of Scarpa) is thinner and more mem-
branous than the other, and is closely united to the tendon of the
external oblique by fibrous bands along the linea alba. Like tlie
subcutaneous part, this layer is continued upwards on the abdomen,
and inwards to the penis and the scrotum, through which it is pro-
longed to the perineum, where it has attachments to the subjacent
parts, as before specified (p. 244). Towards the limb, it ends a little
below Poupart's ligament by joining the fascia lata across the front
of the thigh.

Urine effused in the perineum from rupture of the urethra will
be directed through the scrotum and along the spermatic cord to
the abdomen. From the attachment of the deej^er layer to the
fascia across the thigh, it is evident that the fluid cannot pass down
the limb, though its progress over the front of the abdomen is
uninterrupted.

In the female the superficial fascia of the groin is separable into
two layers, and the disposition of each is nearly the same as in the
male ; but tlie part that is continued to the scrotum in the one sex
enters the labium in the other. In the female the round ligament of
the uterus is lost in it.

Cutaneous Nerves. The skin of the abdomen is supplied mainly
by the lower intercostal nerves ; thus, the cutaneous branches along
the side of the belly are offsets from five or six of those nerves ; and
the cutaneous branches along the front are the terminal parts of the
same trunks. Two other cutaneous offsets from the lumbar plexus,
viz., ilio-hypogastric and ilio-inguinal, appear at the lower part of
the abdomen.

The LATERAL CUTANEOUS NERVES (fig. 97) of the abdomen emerge
between the digitations of the external oblique muscle, in a line with
the same set of nerves on the thorax ; and the lowest are the most

CUTANEOUS NERVES.

263

posterior. As soon as they reacli the surface they divide, with the
exception of the last, into an anterior and a posterior branch : —

The posterior branches are small, and are directed back to the
integuments over the latissimus dorsi muscle.

The anterior branches are continued forwards nearly to the edge of
the rectus muscle, and increasing in size from above downwards,
supply the integuments on the side of the belly ; they furnish offsets
to the digitatious of the external oblique muscle.

The lateral cutaneous branch of the last dorsal nerve is larger than
the others and does not divide like them. After piercing the fibres of

which
divide into

posterior
and

anterior
branches.

Last dorsal
nerve.

Anterior cutaneous
nerves coming
through the sheath of
the rectus abdominis.

Lateral cutaneous nerves

Inner pillar of ex-
ternal abdominal ring.

Outer pillar of ex-
ternal abdominal ring-

External oblique.

Linea semilunaris.

Linea alba.

Anterior superior
iliac spine.

Poupart's ligament.

Deep crural arch.
Gimbemat's liga-
ment.
Triangular fascia.

Fig. 97. — Diagram op the Cutaneous Nerves op the Abdomen and op
THE External Oblique Muscle.

the external oblique muscle, it is directed over the iliac crest to the
surface of the gluteal region (p. 110).

The ANTERIOR CUTANEOUS NERVES of the abdomcn pierce the
sheath of the rectus ; in the integuments they bend outwards tow*ards
the lateral cutaneous nerves. The number and the situation of
these small nerves are very uncertain.

The iLio-HTPOGASTRic NERVE is distributed in two branches : one
passes over the crest of the ilium (iliac branch) ; the other ramifies
on the lower part of the abdomen (hypogastric branch) : —

(a) The iliac branch lies close to the crest of the hip-bone near the
last dorsal nerve, and enters the fat of the gluteal region (p. 110).

Anterior
cutaneous
nerv'es of
intercostal.

Ilio-hypo-
gastric of
lumbar
plexus :

iliac branch,

264 DISSECTION OF THE ABDOMEN.

hypogastric (b) The hypogastric branch pierces the aponeurosis of the external
branch. oblique muscle above the abdominal ring in one or two pieces, and is

distributed to the skin of the lower part of the abdomen.
Ilio-inguinal The ILIO-INGDINAL NERVE beconies cutaneous through the exteinal

plexus. abdominal ring, and descends to the teguments of the scrotum and

of the upper and inner part of the thigh.

Vessels with CuTANEOUS VESSELS. Cutaneous vessels run with both sets of
nerves on the abdomen. With the lateral cutaneous nerves are
branches from the intercostal arteries ; and with the anterior
cutaneous are offsets from the internal mammary and epigastric
vessels. In the groin are three small superficial branches of the
femoral artery, viz., pudic, epigastric, and circumflex iliac.

both lateral The LATERAL CUTANEOUS ARTERIES have the same distribution as
the nerves they accompany. The anterior or chief offsets are directed
towards the front of the abdomen, and end about the outer edge of
the rectus muscle.

and anterior The ANTERIOR CUTANEOUS ARTERIES are irregular in number and
in position, like the nerves. After piercing the sheath of the rectus,
they run outwards with tlie nerves towards the other set of branches.

From Branches of the common femoral artery. Three cutaneous

artery three ofFsets ascend from the thigh between the layers of the superficial

branches : fascia, and ramify in the integuments of the genital organs and lower
part of the abdomen. The beginning of these vessels appears in the
dissection of the thigh (p. 138).

external The superficial external pudic branch crosses the spermatic cord, to

pudic, which it gives offsets, and ends in the integuments of the under-part

of the penis.

superficial The superficial epigastric branch ascends over Poupart's ligament

epigas no, ^^^ ^^^^ Centre, and is distributed in the fat nearly as high as the
umbilicus.

circumflex The superficial circumfiex iliac branch lies below the level of
Poupart's ligament, and sends only a few offsets to the abdomen.

Veins. The companion veins to these arteries join the internal saj)henous

vein of the thigh.

Inguinal The LYMPHATIC GLANDS OF THE GROIN are three or four in number,

^^" ^* and lie along the line of Poupart's ligament. They are placed
between the strata of the superficial fascia, and receive lymphatics
from the abdominal wall, from the gluteal region and perineum, from
the upper and outer portion of the thigh and from the superficial

ducts enter parts of the genital organs. Their efferent ducts pass downwards to
the saphenous opening in the thigh to enter the abdomen.

To expose Disscctioil of the Muscles. The surface of the external muscle

oblique of the abdominal wall (figs. 97 and 98) is now to be freed from fiiscia

muscle. oj-^ i3oth sides of the body.

Precautions. It is not advisable to begin cleaning this muscle in front, because
there it has a thin aponeurosis, which may be taken away
with the fat. Beginning the dissection at the posterior part, the
student is to carry the knife obliquely upwards and downwards in
the direction of the fibres. The thin aponeurosis before referred to

EXTERNAL OBLIQUE MUSCLE.

265

is in front of a line extended upwards from the anterior end of the
iliac crest, and as the dissector approaches that part he must be
careful not to injure the tendon, more particularly above, where it
lies on the margin of the ribs, and is very indistinct.

On the left side the external abdominal ring (c) may be defined,
to show the spermatic cord passing througli it ; but on the right side
a thin fascia (intercolumnar), v/hich is connected with the margin
of that opening, is to be preserved. Lastly, the free border of the
external oblique should be made
evident between the last rib and the
iliac crest.

Muscles of the Abdominal
Wall. On the side of the abdomen
are three large flat muscles, which
are named from their position to
one another, and from the direc-
tion of their fibres : the external
oblique; the internal oblique; and
the deepest, the transversalis.

Near the middle line are placed
other muscles which have a vertical
direction ; namely, the rectus and
the pyramidalis ; and behind is the
quadratus lumborum : these all are
encased by sheatlis derived from
the aponeuroses of the lateral
muscles, and will be subsequently
seen.

The EXTERNAL OBLIQUE MUSOLE

(fig. 98, A, and fig. 97) is fleshy on

the side, and aponeurotic on the

fore part of the abdomen. It arises

by fleshy processes from the eight

lower ribs, the five highest pieces

alternating with similar parts of

the serratus magnus, and the lowest

three with slips of the latissimus

dorsi muscle. From the attachment

to the ribs the fibres are directed

over the side of the abdomen to end in the following manner : — the

lower ones descend almost vertically to be inserted into the anterior

half or more of the outer margin of the iliac crest (fig. 47, p. 113) ; and

the upper and middle fibres are continued forwards obliquely to the

tendon or aponeurosis on the front of the belly.

The ajmneurosis occupies the front of the abdomen, internal to
a line drawn from the prominence of the ninth rib-cartilage to
a point about an inch and a half in front of the anterior superior
iliac spine ; and it is broader below than above. Along the middle
line it ends in the tinea alba — the common place of union in the

To define

abdominal

ring.

the aponeu-
roses of
which en-
case three
vertical.

External
oblique
muscle :

origin from
ribs;

Fig. 98.

A. The external obhque muscle.

B. Poupart's ligament.

c. External abdominal ring.
D. Gimbernat's ligament.

insertion
intd pelvis
and linea
alba.

Aponeurosis
covers front
of the belly ;

DISSECTION OF THE ABDOMEN.

disposition
above and
below.

Relations.

Lines on
the aponeu-
rosis ;

apertures
in it:

abdominal
ring.

Use of both
muscles,
acting from
pelvis,

and thorax ;

one muscle
acting ;

influence on

abdominal

cavity.

In the linea
alba the
aponeuroses
are united.

External

abdominal

ring:

form and
situation ;

size :

middle line of the aponeuroses of opposite sides. Above, it is thin,
and is continued over the thorax to the pectoralis major muscle.
Below, its fibres are stronger and more distinct than above, and are
directed obliquely downwards and inwards to the pelvis ; — some of
them are fixed to the front of the pelvis ; and the rest are collected
into a firm band, Poupart's ligament, between the pubic spine and
the iliac crest (p. 267).

Relations. The muscle is subcutaneous. Its posterior border is
unattached between the last rib and the iliac crest, but it is usually
overlapped by the edge of the latissimus dorsi, except for a short
distance below. At the outer part of the aponeurosis in the front of
the abdomen is a curved white line, the linea semilunaris, marking
the outer edge of the rectus muscle (fig. 97) ; and crossing between
this and the linea alba are three or four somewhat irregular lines —
the linece transversce. Numerous small apertures in the aponeurosis
transmit cutaneous vessels and nerves ; and near the pubis is the
large opening of the external abdominal ring (fig. 97), which gives
passage to the spermatic cord in the male, and to the round ligament
in the female.

Action. Both muscles, taking their fixed point at the pelvis, will
bend the trunk forwards ; but "svith the spine fixed, they will draw
down the ribs. If they act from the thorax they will elevate the pelvis.

Should one muscle contract, it will incline the trunk to the same
side, or raise the pelvis, according as the upper or the lower attach-
ment may be movable ; or if the trunk is prevented from being
bent, it will turn the thorax to the opposite side.

The external oblique also acts powerfully with the other broad
muscles in flattening the wall and diminishing the cavity of the
abdomen, and in forcing up the diaphragm during expiration by
means of pressure transmitted through the abdominal viscera.

Direction. Besides the general arrangement of the aponeurosis
over the front of the abdomen, the student is to examine more
minutely the linea alba in the middle line, the external abdominal
ring with the fascia prolonged from its margin, and the thickened
border named Poupart's ligament.

Linea alba. This white band on the front of the abdomen marks
the place of meeting of the aponeuroses of the opposite sides. It
extends from the eiisiform process to the pubic symphysis, and is
wider above than below. It is perforated here and there by small
apertures, which allow pellets of fat to protrude sometimes. A
little below the centre is the umbilicus, which now projects beyond
the surface, though before the skin was removed a hollow indicated
its position.

External abdominal ring (fig. 97 and fig. 98, c). This opening is
situate near the pubes, between the diverging fibres of the aponeu-
rosis. It is somewhat triangular in form, with the base at the pubic
crest, and the apex directed upwards and outwards. The long
measurement of the aperture is about an inch, and the transverse
about half an inch.

APONEUROSIS OF THE EXTERNAL OBLIQUE. 267

Its margins are named pillars, and differ in form and strength, inner side or
The inner one, thin and straight, is attached below to the front of ^^ ^'
the symphysis jiiibis, where it decussates with the corresponding
piece of the opposite side. The outer pillar is stronger, and is
curved, so as to form a kind of groove for the support of the outer pillar ;
spermatic cord ; it is continuous with Poupart's ligament and is
attached below to the pubic spine. A thin membrane (intercolumnar fascia pro-
fascia), derived from some fibres on the surface of the aponeurosis, m^n ;™™
covers the opening.

The external ring gives passage in the male to tlie spermatic cord, objects
and in the female to the round ligament ; and in each sex the trans- S^U^h.
niitted part lies on the outer pilhxr as it passes through, and obtains
a covering from the intercolumnar fascia. Through this aperture an
inguinal hernia protrudes from the wall of the abdomen.

The intercolumnar fibres (tig. 97) run transversely on the surface of Intercolum-
the aponeurosis, and bind together its parallel fibres, so as to con-
struct a firm membrane. Interiorly, where they are strongest, some attachment

11 111 11 1 • , 1 1-1 /.v. 1 infenorly ;

well-marked bundles are connected with the outer third oi roupart s

ligament, and the anterior end of the iliac crest. At the external

abdominal ring the fibres stretch from side to side, and close the

upper end of that opening ; and as they are prolonged on to the cord they pro-

from the margin of the ring, they give rise to a membrane named columnar

the intercolumnar or spermatic fascia. On the left side, where the f^^ia.

fascia is entire, this thin covering will be manifest on the surface of

the cord, or on the round ligament in the female.

Dissection. To see the attachments and connections of Poupart's To see
ligament, it will be necessary to reflect, on both sides of the body, poupart's
the lower part of the external oblique aponeurosis towards the iiga«ient,
thigh. For this purpose an incision is to be carried inwards,
through the aponeurosis, from the front of the iliac crest to a spot
about three inches from the linea alba ; and the tendon is to be throw down
detached from the subjacent parts with the handle of the scalpel, external
When the aponeurosis cannot be separated farther from the tendons oblique,^
beneath, near the linea alba, it is to be cut in the direction of a line
descending to the symphysis pubis.

After the triangular piece of the aponeurosis has been thrown and show
towards the thigh, the spermatic cord is to be dislodged from the fascia,
surface of Poupart's ligament, to see the insertion of the ligament
into the pubis, and to lay bare the fibres (triangular fascia) which
ascend therefrom to the linea alba.

PoujMrfs ligament (fig. 97) is the lower border of the aponeurosis Poupart's
of the external oblique, which is thickened and folded backwards, so '^^
as to form a slight groove with the concavity upwards. In the hollow
of the ligament the lowest fibres of the internal oblique and trans-
versalis muscles and the cremaster take their origin. Externally it outer and
appears round and cord -like, and is attached to the anterior superior inner attach-
iliac spine. Internally it widens as it approaches the pubis, and is ™^° *
inserted into the pubic spine and the pectineal line of the hip-bone forms
for about three-quarters of an inch, forming a triaugulai- piece with ijgamerS^;

DISSECTION OF THE ABDOMEN.

its direction,

and parts in
contact with
it.

Triangular
fascia.

Dissection
to expose
internal
oblique.

Clean the
cremaster.

its base directed outwards, which is named Gimhernafs ligament
(fig. 97 and 98).

By its lower border Poupart's ligament joins the fascia lata of the
thigh ; and so long as this membrane remains uncut, the band is
curved with its convexity downwards, especially when the limb is
extended on the trunk. The outer half of the ligament is oblique,
and is firmly united with the subjacent iliac fascia; its inner
half is placed over the vessels passing from the abdomen to the
thigh.

Triangular fascia. From the insertion of Gimbernat's ligament into

the pectineal line, some
fibres are directed upwards
and inwards to the linea
alba, where they blend with
the other tendons. As the
fibres ascend, they diverge
and form a thin sheet, to
which the above name has
been given (fig. 97).

Dissection. The upper
part of the external oblique
is now to be taken away, on
both sides of the body, to
see the parts beneath. It
may be detached by carry-
ing the scalpel through the
digitations on the ribs back
to the free border, and then
through the insertion into
the iliac crest. The muscle
is to be thrown forwards as
far as practicable, after the
nerves crossing the iliac
crest are dissected out ; but
in raising it care must be
taken not to detach the
rectus muscle from the ribs
above, nor to cut through
the tendon of the internal
oblique at the upper part.
By the removal of the fatty
tissue the underlying internal oblique muscle, with some nerves
issuing through it below, will be exposed.

At the lower border of the internal oblique, where it springs from
the deep surface of Poupart's ligament, it will be seen that the fibres
are prolonged down upon the spermatic cord. These fibres consti-
tute the cremaster muscle, and should be defined. They consist of
fleshy loops which descend through the external abdominal ring.
Internal to the cord they become tendinous, and are easily taken away.

Fm. 99. — The Parts beneath the
External Oblique Muscle.

A. Internal oblique muscle.

B. Latissinius dorsi, cut.

0. Part of the hinder tendon of the
transversalis muscle.

D. Poupart's ligament.

E. External, f, internal intercostals.

INTERNAL OBLIQUE MUSCLE. 269

Parts covered by the external oblique (fig. 99). Beneath the external Parts
muscle are the internal oblique, with parts of the ribs and intercostal external ''^
muscles. At the lower part of the abdomen the muscle conceals oblique,
the spermatic cord and the branches of the lumbar plexus in the
abdominal wall.

The INTERNAL OBLIQUE MUSCLE (fig. 99, a) is fleshy at the side internal

and aponeurotic in front, like the preceding ; but its fibres (except muscle :

the lowest) ascend across those of the external oblique. The muscle

ames from the outer half of Pou part's ligament, from the anterior origin from

two-thirds of the crest of the ilium (fig. 47, p. 113), and from the ^^^""'^ '

tendon of the transversalis muscle (fascia lumborum, c) in the

interval between that bone and the last rib. The fibres diverge

on the abdomen to their destination : — The upper ones ascend, and insertion

have a fleshy insertion into the cartilages of the last three ribs, J?^ ^^

where they join the internal intercostal muscles of the lowest two lineaaiba.

spaces. The remaining fibres pass forwards, with varying degrees of

obliquity, to end in an aponeurosis.

The aponeurosis of the muscle extends from the thorax to the Aponeurosis
pelvis, and is broader above than below. For the most part it is enclose
split to encase the rectus (as will be seen when that muscle is rectus,

^ ^ except

exposed) ; but in the lower half of the space between the umbilicus below ;

and pubis it is undivided, and lies altogether in front of that muscle.

Along the middle line the two layers are united together, as well as

with those of the opposite side, in the linea alba. Superiorly the

aponeurosis is arranged in the following manner : — for a short attachments

distance before it divides, it is fixed to the ninth costal cartilage ; ^° ^ ^^^'

and the posterior of the layers into which it divides continues this

attachment along the eighth and seventh cartilages to the ensiform

process ; while the anterior is prolonged over the chest, blending

with the aponeurosis of the external oblique. Inferiorly its fibres

become more distinct and are inserted into the front of the pubis, and and pehis.

into the pectineal line for half an inch behind the attachment of

Gimbernat's ligament. This lowest part of the aponeurosis is

blended with that of the underlying transversalis to form what

will be described as the conjoined tendon of the two muscles.

Relations. The muscle is covered by the external oblique muscle. Parts in

It is attached on all sides, except between Poupart's ligament and fntenSi^^^^

the pubis, where it arches over the spermatic cord, and has the oblique.

cremaster muscle continuous with it. The parts covered by the

internal oblique will be seen when the muscle is reflected.

Action. Both muscles depress the ribs, and assist in forcing back Use of both

inu.scl6s
the viscera of the. belly after they have been protruded by the "'

descent of the diaphragm.

One muscle may incline the body laterally ; and contracting with of one.

the opposite external oblique (the fibres of the two having the same

direction), it will rotate the trunk to the same side.

The CREMASTER MUSCLE (fig. 100, d) is a muscular slip which lies Cremaster
along the lower border of the internal oblique, and is named from its ^^^^
suspending the testicle. The muscle is attached both at the inner and

270

DISSECTION OF THE ABDOMEN.

attach-
ments ;
external
fleshy,

internal
tendinous ;

forms loops
over the
cord,

giving rise
to cremas-
teric fascia

In left groin
replace the
jMirts.

On right
side reflect
cremaster

outer sides, like the lowest fibres of the internal oblique, of which it
is essentially a part. Externally it is fleshy, and arises from Poupart's
ligament, below and in part beneath the internal oblique, with which
some of its fibres are connected. Internally it is narrow, and is
inserted by tendon into the front of the pubis, joining the tendon of
the internal oblique.

Between the two points of attachment the fibres descend on the
front and sides of the cord, forming loops with the convexity down-
wards as far as, and over,
the testis. The bundles
of fibres are united by
areolar tissue so as to give
rise to a covering on the
front of the cord, which
is named the cremasteric
fascia. Occasionally the
fibres may be behind as
well as on the sides and
front of the cord.

Action. It elevates the
testicle towards the ab-
domen, and in some cases
is under the influence of
the will ; but it may be
excited to contract involun-
tarily by cold, fear, &c.

It will be remembered
that the fascia (tunica
dartos) of the scrotum is
reinforced by a number of
unstriped muscle fibres, and,
moreover, that it is con-
nected with the overlying
skin. Under the influence
of various stimuli (heat,
cold, &c.) the unstriped
muscle fibres contract, and
the scrotal tissues, as well
as the coverings of the
spermatic cord by the con-
traction of the cremaster,
are puckered up to form a protecting pad in front of the testis, as it
lies at the back of the scrotum.

Dissection. On the left side of the body the student is not now
to make any further dissection of the abdominal wall ; and the layers
that have been reflected in the groin should be replaced until the
examination of that region is resumed in connection with hernia.

On the right side the dissection is to be earned deeper by the
removal of the internal oblique and the cremaster. The last

Fig, 100. — The Cremaster. The Lower
Part of the Internal Oblique, with
THE Cremaster Muscle and thr
Testicle.

A. External oblique, reflected.

B. Internal oblique,
c. Rectus abdominis.

D. Cremaster, with its loops over the
spermatic cord and the testicle.

TRANSVERSALIS MUSCLE.

271

muscle may be reflected from the cord by means of a longitudinal

To raise the internal ohlique^ it will be necessary to cut it through
firstly near the ribs, secondly along the crest of the ilium and
Poupart's ligament, and lastly at the hinder part, so as to connect
the first two incisions. Its depth will be indicated by a fatty layer
between it and the transversalis, and by a branch of artery between
the two muscles near the anterior superior iliac spine (fig. 106, 6,
p. 287). In raising the
muscle towards the edge
of the rectus, let the student
separate with great care
the lower fibres from those
of the transversalis with
which they are often con-

ined, and dissect out,
ctween the two, the inter-
costal nerves and arteries,
and the two branches of
the lumbar plexus (ilio-
hypogastric and ilio-ingui-
nal) near the fore part of
the ilium. The offsets en-
tering the muscle must be
cut.

Parts covered by the in-
ternal oblique (fig. 101).
The internal oblique con-
ceals the transversalis
muscle and the vessels and
nerves between the two.
Near Poupart's ligament it
lies on the spermatic cord
and the transversalis fascia.
The rectus muscle is
covered below by the
aponeurosis.

The TRANSVERSALIS

MUSCLE (fig. 101, a) forms
the third stratum in the
wall of the abdomen, and differs from the two oblique muscles
in having a posterior as well as an anterior aponeurosis. Like the
internal oblique, it is attached on all sides, except where the sper-
matic cord lies. At the pelvis it arises from the outer third of
Poupart's ligament and from the anterior two-thirds of the iliac crest
along the inner border (fig. 139. p. 369) ; at the chest it takes origin by
fleshy slips from the inner surface of the lower six costal carti-
lages ; and between the chest and the pelvis it is connected with
the lumbar vertebrae by means of its posterior aponeurosis, or the

and internal
oblique.

Fig. 101.

A. The Transversalis muscle, with b, its
anterior, and c, its posterior tendon (fascia
lumborum).

D. Poupart's ligament.

1. Last dorsal nerve with its accom-
panying artery.

2. Ilio-hypogastric nerve with its artery,
ft Intercostal nerves and arteries.

Transversa-
lis muscle :

origin from
chest, loins,
and pehis ;

fibres end in
aponeurosis.

272 DISSECTION OF THE ABDOMEN.

fascia lumboriim. All the fibres are directed to the anterior

aponeurosis.

The aponeu- Its anterior ajwneurosis is widest in the centre, and narrowest at

behind^^^^^ the upper end. Internally it is continued to the linea alba, passing

rectus, ex- beneath the rectus as low as midway between the umbilicus and the

lower part, pubis, and in front of the mussle below that spot. Its attachment

below to the pelvis is nearly the same as the internal oblique ; for

it is fixed to the front of the pubis, and to the pectineal line for

Fibres to about an inch. Some of the fiibres end on the transversalis fascia,

fasda^^^^^^^*^ and are connected beneath Poupart's ligament with a thickened band

of that fascia which is called the deep crural arch (fig. 97, p. 263).

Use. Action. The transversalis muscle draws downwards the lower

ribs, and diminishes the abdominal cavity, compressing the viscera

and forcing upwards the diaphragm.

At pelvis Conjoined tendon. The aponeuroses of the internal oblique and

conjoined transversalis muscles are united near their attachment to the pubis,

tendon. and give rise to the conjoined tendon. The aponeurosis of the

internal oblique extends about half an inch along the pectineal line,

while that of the transversalis reaches an inch along the bony ridge

and forms the greater part of the conjoined tendon (fig. 102 and fig.

105, p. 286).

Posterior The posterior aponeurosis of the transversalis, or the fascia lum-

aponeurosis. i^Qp^^ ^g^^ js described in the deep dissection of the back, and it is

sufficient here to state that it consists of three layers : an anterior,

attached to the front of the roots of the lumbar transverse process ; a

middle, attached to their tips ; and a posterior, attached to the spineS

of the same vertebrae. The transversalis is chiefly continuous with

the middle of these layers and only slightly with the others.

Relations of Relations. Superficial to the transversalis are the two muscles

^j^^^[g^^^^'^ before examined; and beneath it is the thin transversalis fascia.

Its fleshy attachments to the ribs alternate with like processes of

the diaphragm ; and the highest slip joins the lower edge of the

triangularis sterni muscle. The lower border of the transversalis is

fleshy in the outer, but tendinous in the inner half, and is arched

above the internal abdominal ring.

Expose Dissection. Eemove the aponeurotic layer from the rectus muscle

pyramidalis °^ *^^ right side, make a longitudinal incision through the tendinous

sheath, and turn it to each side. As the sheath is reflected, its

union with three or more tendinous bands across the rectus will

have to be cut through ; and near the pubis a small muscle, the

pyramidalis, will be exposed. The dissector should leave the nerves

entering the outer border of the rectus.

Leave the ^^^ ^^® ^^^^ ^i^® of the body the rectus should not be laid bare

left side. below the umbilicus, in order that the special dissection of the parts

concerned in inguinal hernia may be made on this side.
Rectus The RECTUS MUSCLE (fig. 102, a) extends along the front of the

muscle : abdomen from the pelvis to the chest. It is narrowest below, where
origin from it arises from the pelvis by two tendinous processes : — one, the
^^ ^^ ' internal and smaller, is attached to the front of the symphysis pubis

SHEATH OF RECTUS.

273

in common with that of the opposite side ; and the external process
springs from the pubic crest. Becoming wider towards the thorax,
tlie rectus is inserted by three hirge fleshy and tendinous slips into
the cartihiges of the fifth, sixth and seventh ribs, the outermost slip
usually extending to tlie bone of the fifth rib. Some of the inner fibres
are often attached to the
ensiform process.

The muscle is con-
tained in an aponeu-
rotic sheath, except
above and below; and
its fibres are interrupted
at intervals by tendi-
nous lines — the iriscrip-
tiones tendinece.

Action. It will draw
down the thorax and
the ribs, or raise the
pelvis, according as its
fixed point may be below
or above. Besides im-
parting movement to
the trunk, it will
diminish the cavity of
the abdomen, and com-
press the viscera.

Sheath of the rectus (d).
This sheath is derived
from the splitting of
the aponeurosis of the
internal oblique at the
outer edge of tlie rectus.
One piece passes before,
and the other behind
the muscle ; and the
two unite at the inner
border so as to com-
plete the sheath. In-
separably blended with
the stratum in front of
the rectus is the aponeu-
rosis of the external oblique ; and joined in a similar manner
with that behind is the aponeurosis of the transversalis. The
anterior layer of the sheath adheres closely to the tendinous inter-
sections of the muscle.

The sheath is deficient behind, both at the upper and lower end
of the muscle. Above, the muscle rests on the ribs, without the
intervention of the sheath, which is fixed to the margin of the
thorax. Below, at, or somewhat above, a point midway between the

D.A. T

insertion
into rib-
cartilages ;

has cross
tendons :

use on
tiunk,

on abdomen.

Its sheath :

Conjoined tendon.

Fig.

102. — The Rectus Muscle
Abdomen.

0^ THE how formed

The muscle is dissected on the right side, and
left in its sheath on the left. Close above the
pubes the pyiumidaUs is exposed.

A. Rectus.

B. Interna] oblique.

c. Poupart's ligament.

D. Anterior layer of the sheath of the rectiiSL

deficient
above and
below.

274

DISSECTION OF THE ABDOMEN,

Fold of
Douglas.

Lineae
trans vers je

are three or
more ;

situation.

Linea semi-
lunaris is at
edge of
rectus.

Pyramidalis
muscle :

attach-

Nerves in
wall of
abdomen.

Intercostal
nerves

are between
oblique and
trausver-
salis :

offsets.

Last dorsal
nerve.

umbilicus and pubis, the aponeurosis of the internal oblique ceases
to split, and then passes altogether in front of the rectus, with the
other aponeuroses. When the rectus is raised, the termination of
the hinder layer of the sheath is seen to be marked by a more or less
distinct white line, concave towards the pubis, which is termed the
semilunar fold of Douglas {fig. 105, p. 286) : below this the rectus is
in contact with the transversalis fascia.

The linem transversce (fig. 102) on the front of the sheath are
caused by the tendinous intersections of the rectus. The most
constant are three in number, and have the following position ; one
is opposite the umbilicus, another at the lower end of the ensiform
process, and the third is midway between the two. If there is a
fourth it will be placed below the umbilicus. These markings
seldom extend the whole depth or breadth of the muscular fibres,
more particularly the highest and lowest.

Linea semilunaris (fig. 97, p. 263). This line corresponds with the
outer edge of the rectus, and reaches from the cartilage of the ninth
rib to the pubic spine of the hip-bone : it marks the line of division
of the aponeurosis of the internal oblique muscle.

The PYRAMIDALIS MUSCLE (fig. 102) is triangular in form, and is
placed in front of the lower end of the rectus. It arises by its base
from the front of the pubis, and is inserted into the linea alba below
the mid-point between the umbilicus and the pelvis. This small
muscle is often absent.

Action. The muscle renders tense the linea alba ; and when large
it may slightly assist the rectus in compressing the viscera.

Nerves op the Abdominal Wall (fig. 101, p. 271, and fig. 97,
p. 263). Between the internal oblique and transversalis muscles
are situate the intercostal nerves ; and near the pelvis are two
branches of the lumbar plexus, viz., the ilio-hypogastric and ilio-
inguinal nerves. Some arteries accompany the nerves, but they
will be referred to with the vessels of the abdominal wall
(p. 283).

The LOWER FIVE intercostal nerves enter the wall of the
abdomen from the intercostal spaces. Placed between the two
deepest lateral muscles, the nerves are directed forwards to the
edge of the rectus, and through this muscle to the surface of the
abdomen near the middle line. About midway between the spine
and the linea alba, the nerves furnish cutaneous branches to the side
of the abdomen (lateral cutaneous, p. 262) ; and while between the
abdominal muscles they supply branches to them and ofi"sets of
communication with one another. A greater part of the lower than
of the upper nerves is visible, owing to the shortness of the inferior
spaces.

The last dorsal nerve (fig. 101') is placed below the twelfth rib,
and therefore is not in an intercostal space, but it has a similar course
and distribution to the foregoing. As it extends forwards to the rectus
it communicates sometimes with the ilio-hypogastric nerve ; and its
lateral cutaneous branch perforates the two oblique muscles (p. 263).

THE TRANSVERSALIS FASCIA. 275

The iLio-HYPOGASTRic NERVE (2) perforates the back of the iiio-hypo-
transversalis muscle near the iliac crest, and divides into iliac and ^ry"^
hypogastric branches.

The iliac branch pierces both oblique muscles close to the crest of iliac part
the ilium, to reach the gluteal region (p. 263).

The hypogastric branch is directed forwards above the hip-bone, and hypo-
giving twigs to the transverse and internal oblique muscles, and °^^ "^ ^^ *
communicating with the ilio-inguinal nerve. It perforates the
fleshy part of the internal oblique near the front of the iliac crest,
and the aponeurosis of the external oblique near the linea alba and
finally becomes cutaneous in the hypogastric region (p. 264).

The ILIO-INGUINAL NERVE perforates the transversalis muscle near iiio-iugulnal
the front of the iliac crest. It afterwards pierces the internal "®'^^®-
oblique, and reaches the surface through the external abdominal
ring (p. 264) : on its way it furnishes offsets to the internal oblique,
the transversalis, and tlie pyramidalis.

Dissection. To see the transversalis fascia on the right side, it Dissection
will be necessary to raise the lower part of the transversalis muscle ^iirfascia'
by two incisions : — one of these is to be carried through the fibres
attached to Poupart's ligament ; the other, across the muscle from
the front of the iliac crest to the margin of the rectus. With a little
care the muscle may be separated easily from the thin fascia beneath.

The TRANSVERSALIS FASCIA is a thin fibrous layer between the Transver-
transversalis muscle and the peritoneum. In the inguinal region, ''^^'^ fascia
where it is unsupported by muscles, the fascia is considerably
stronger than elsewhere, and is joined by some tendinous fibres of is best
the transversalis muscle ; but farther from the pelvis it gradually tJ^'^groiu^-
decreases in strength, until at the thorax it becomes very thin.

In the part of the fascia now laid bare is the internal abdominal pierced by
ring, which gives passage to the spermatic cord, or the round liga- abdominal
ment of the uterus, according to the sex ; it resembles the hole into "ug.
the finger of a glove in being visible from within, but not externally,
owing to the fascia being prolonged from its margin on to the cord.
On the inner side of the ring the fascia is thinner than on the outer,
and is fixed to the body of the })ubis and to the ilio-pectineal line
behind the conjoined tendon, with which it is united.

Along the outer half of Poupart's ligament the fascia ends by Ending of
joining the posterior margin of that band, and it will be afterwards ^^^^^^^ ^^^o"^-
seen to unite with the iliac fascia for the same extent, but beneath
the inner half of the ligament it is continued downwards to the
thigh, in front of the blood-vessels, to form the anterior part of the
crural sheath around them.

Internal abdonmial ring (fig. 105, p. 286, and fig. 106, p. 287). Situation
This opening is situate midway between the symphysis pubis and abdominal
the anterior superior iliac spine, and half an inch above Poupart's ring,
ligament. From its margin a thin tubular prolongation of the
transversalis fascia (infundibuliform fascia) is continued around
the cord as before said.

Dissection. The tubular prolongation on the cord may be traced Dissection

T 2 process on

cord.

276

DISSECTION OF TFIE ABDOMEN.

Subperi-
toneal tissue
in groin.

Trace re-
mains of
peritoneum.

Peritoneum
of the groin
is prolonged
on the cord :

piece may-
be imper-
vious,

or saccu'
lated.

or open.

In female
may be
partly open.

Spermatic
cord

is oblique in
the abdomi-
nal wall,

and vertical
beyond ;

relations ;

coverings.

by cutting the transversalis fascia liorizontally above the opening of
the ring, and then longitudinally over the cord. With the handle
of the scalpel the thin membrane may be reflected to each side, so
as to lay bare the subperitoneal fat.

The suhjjeritoneal fat forms a layer between the transversalis
fascia and the peritoneum. Its thickness varies much in different
bodies, but is greater at the lower than at the upper part of the
abdomen. This structure will be more specially noticed in the
examination of the wall of the abdomen from the inside.

Dissection. After the subperitoneal fat has been seen, let it be
reflected to look for the remains of a piece of peritoneum which
extends along the cord in the form of a fibrous thread.

The peritoneum, or the serous sac of the abdominal cavity, projects
forwards slightly opposite the internal abdominal ring. Connected
with it at that s]3ot is a fibrous thread (the remains of a prolongation
to the testis in the foetus) which extends a variable distance along
the front of the cord. It is generally impervious, and can be followed
only a very short way ; but it may sometimes be traced as a fine
band to the tunica vaginalis of the testis.

In some bodies the process may be partly open, being sacculated
at intervals ; or it may form occasionally a single large bag in front
of the cord. Lastly, as a rare state, it may remain unclosed as in
the foetus, so that a coil of intestine could descend in it from the
abdomen.

In the female the foetal tube of peritoneum sometimes remains
pervious for a short distance in front of the round ligament ; the
unobliterated portion being called the canal of Nuck.

The SPERMATIC CORD (fig. 105, p. 286, and fig. 106, f, p. 287) extends
from the internal abdominal ring to the testis, and consists mainly
of the vessels and efferent duct of the gland, united together by
coverings from the structures by or through which they pass.

In the wall of the abdomen the cord lies obliquely, since its aperture
of entrance amongst the muscles is not opposite its aperture of
exit from them ; but, escaped from the abdomen, it descends almost
vertically to its destination. In the oblique part of its course it is
contained in the passage named the inguinal canal ; it is placed at
first beneath the internal oblique, and rests against the transversalis
fascia; but beyond the lower border of the oblique muscle, it lies on
the upper surface of Poupart's ligament, with the aponeurosis of the
external oblique between it and the surface of the body, and the con-
joined tendon behind it.

Its several coverings are derived from the strata in the wall of the
abdomen. Thus, from within outw^ards are

(1) the subperitoneal fat,

(2) the infundibuliform process of the transversalis fascia,

(3) the cremaster muscle continuous with the internal oblique,

(4) the intercolumnar or spermatic fascia from the external
oblique muscle,

and, lastly, the superficial fascia and the skin.

SPERMATIC CORD. 277

The round ligament, or the suspensory cord of the uterus, occupies in female
the inguinal canal in the female, and ends in the integuments of the JJent is?n
groin. Its coverings are similar to those of the spermatic cord pi^^e of
of the male except that it wants the cremaster.

THE SPERMATIC CORD AND THE TESTIS.

Dissection. The constituents of the cord will now be displayed by Dissection,
cutting them through longitudinally, as far as the scrotum, and turn-
ing aside the different surrounding layers, and removing the areolar
tissue. The dissector shouLl trace branches of the genito-crural
nerve and deep epigastric artery into the cremasteric covering, and
note the passage of the spermatic vessels between the abdomen
and the cord at the internal abdominal ring, and define the vas
deferens.

Vessels and nerves of the cord. In the cord are collected together Constitu-

the spermatic artery and veins, which convey the blood to and from cord.°^*^^

the testicle, the nerves and lymphatics of the testicle, and the vas

deferens or the efferent duct.

In the female a branch from the ovarian artery enters the round Vessel in
1 • , female,

ligament.

The vas deferens reaches from the testicle to the urethra, and is Vas defe-
placed behind the other constituents of the cord ; it will be recog- ^^^^ '
nised by its resemblance in feel to a piece of whipcord, when it is
taken between the finger and the thumb. As it enters the abdomen situation
through the opening in the transversalis fascia (internal ring), it lies and course,
on the inner side of the vessels of the testicle, and, at the same place,
winds behind the epigastric artery. A small artery {the artery of
the vas) will be seen running along it. It is derived either from the
superior or inferior vesical arteries.

Cremasteric artery and nerve. The cremasteric covering of the cord Artery and
has a separate artery and nerve. The artery is derived from the coverings o^f
deep epigastric, and is distributed to the coverings of the cord. The ^^^ cord ;
genital branch of the genito-crural nerve enters the cord by the internal
abdominal ring, and ends in the cremaster muscle.

Cutaneous vessels and nerves are supplied to the integuments »°^ <^"^-
covering the cord from the superficial external pudic artery and
the ilio-inguinal nerve.

Dissection. The spermatic cord and all its coverings should now
be cut through at the external abdominal ring and, with the right
half of the scrotum and the enclosed testis, removed for examina-
tion. The parts should be pinned out on a leaded piece of cork and
dissected under water; the different layers being divided by a
longitudinal incision and pinned out laterally as they are reflected.

In the meantime the anterior abdominal wall should be carefully
covered with cloths soaked in preservative.

The TESTICLES (testes) are the glandular organs for the secretion of Testes
the semen. Each is suspended in the scrotum by the spermatic cord scrotum,
and its coverings, but the left is usually lower than the right ; and

278

DISSECTION OF THE ABDOMEN.

To see the
serous sac.

Tunica
A'aginalis

partly
covers the
testicle,

and lines
scrotum :

visceral
part,

and parietal.

Testicle
oval ;

margins.
Epididymis.

Hydatid of
Morgagni.

Suspended
obliquely.

Dimensions.

and weight.

A dense
tunic en-
closes small
secreting

each is provided with an excretory duct named the vas deferens. A
serous sac partly surrounds each organ.

Dissection. For the purpose of examining the serous covering of
the testicle (tunica vaginalis) make a small aperture into the upper part
of the sac when the skin of the scrotum and the superficial coverings
have been reflected and inflate it. The sac and the spermatic
cord are then to be cleaned ; and the vessels of the latter are to be
followed to their entrance into the testicle. Finally the tunica
vaginalis is to be opened from the front to expose the testis.

The tunica vaginalis (fig. 103, d) is a serous bag, which is con-
tinuous in the foetus with the peritoneal lining of the abdomen, but
becomes subsequently a distinct sac through the obliteration of the
intermediate part.

It invests the testicle after the manner of other serous mem-
branes ; for the testicle is placed behind it, so as to be partly
enveloped by it. The sac, however, is larger than is necessary for
covering the testicle, and projects some distance above it. Like
other serous membranes, it has an external rough, and an internal
smooth surface ; and like them, it has a visceral and a parietal part.
The visceral layer (tunica vaginalis testis) covers the testicle, except
posteriorly where the vessels lie. On the outer side it extends
farther back than on the inner, and invests the greater part of the
epididymis, forming a pouch (digital fossa) between that body and
the testicle.

The parietal part of the sac (tunica vaginalis scroti) is more
extensive than the piece covering the testicle, and lines the con-
tiguous layer of the scrotum.

Form and position of the testis (fig 103). The testicle is oval in
shape, with a smooth surface, and is somewhat compressed from side
to side. The anterior margin is convex and free ; the posterior,
is flattened, and is pierced by the spermatic vessels and nerves.
Stretching like an arch along the outer side is the epididymis (6).
Attached to the upper end of the testis is a small body (c), the
hydatid of Morgagni, which is the remains of the upper end of the
foetal duct of Miiller ; and occasionally other smaller projections of
the tunica vaginalis are connected with the top of the epididymis.

The testis is suspended obliquely, so that the upper part is directed
forwards and somewhat outv/ards, and the lower end backwards and
rather inwards.

Size and v^eight. The length of the testis is an inch and a half
or two inches ; from before backwards it measures rather more
than an inch, and from side to side rather less than an inch. Its
weight is nearly an ounce, and the left is frequently larger than the
other.

Structure. The substance of the testicle is composed of minute
secreting tubes, around which the blood-vessels are disposed in
plexuses. Surrounding and supporting the delicate seminiferous
tubes is a dense covering — the tunica albuginea. The excretory, or
efferent, duct is the vas deferens.

SEMINAL TUBES OF TESTICLE.

279

Dissection. With the view of examining the investing fibrous
coat, let the testis be placed on its outer side, viz., that on which the
epididymis lies, and let it be fixed firmly in that position with pins.
The fibrous coat is to be cut through along the anterior part, and
thrown backwards as far as the entrance
of the blood-vessels. While raising this
membrane a number of fine bands will
be seen traversing the substance of the
testicle, and a short septal piece (medias-
tinum) may be perceived at the back of
the viscus, where the vessels enter ; but
it will be expedient to remove part of
the mass of tubes from the interior
(fig. 104), to bring more fully into view
the mediastinum, and to trace back some
of the finer septa to it.

The tunica albiiginea, or the fibrous
coat of the testicle, is of a bluish-white
colour, and resembles in appearance the
sclerotic coat of the eyeball. This mem-
brane protects the secreting part of the
testicle, and maintains the shape of the
organ by its dense and unyielding struc-
ture : it also sends inwards processes to
support and separate the seminal tubes.
These offsets of the membrane appear in
the dissection ; and one of them at the
back of the testicle, which is larger than
the rest, is the mediastinum.

The mediastinum testis (corpus High-
morianum, fig. 104, r,) projects into the
gland for a third of an inch with the
blood-vessels. It is situate at the back
of the testis, extending from the upper
nearly to the lower end, and is rather
larger and deeper above than below. It
is formed of two pieces, which are united
in front at an acute angle. To its front
and sides the finer septal processes are
connected ; and in its interior are con-
tained the blood-vessels behind, and a net-
work of seminal ducts (rete testis) in front.

Of the finer processes of the tunica albuginea (fig. 104, h) which
enter the testis, there are two kinds. One set, round and cord-like,
but of different lengths, is attached posteriorly to the mediastinum,
and serves to maintain the shape of the testis. The other set forms
delicate membranous septa, which divide the mass of seminal tubes
into lobes, and join the mediastinum, like the rest.

Within the tunica albuginea is a thin vascular layer, the tuyiica

How to see
the struc-
ture of the
testis.

Fig. 1 03.— The Testis, with
THE Tunica Vaginalis

LAID OPEN.

a. Testicle.

b. Globus major of the
epididymis.

c. Corpus Morgagni.

d. Parietal paii; of the
tunica vaginalis.

e. Vessels of the spermatic
cord.

/. Vas deferens.

and

finer septa ;

a vascular
layer lines

280

DISSECTION OF THE ABDOMEN.

it (tunica
vasculosa).

Secreting
tubules :

appearance
and

length ;

communi-
cations ;

and size.

Tubes
change their

They form
the lobes :

number ;
shape ;

tubes in
tliem, and
arrange-
ment.

Tubes next

become

straight

(tubuli

recti),

afterwards
join toge-
ther (rete
testis),

and leave
the gland
as vasa
efferentia.

vasculosa, which lines the fibrous coat, and covers the different septa
in the interior of the gland. It is formed of the ramifications of
the blood-vessels, united by areolar tissue, like the pia mater of
the brain : in it the arteries are subdivided before they are dis-
tributed on the secreting tubes and the small veins are collected
into larger trunks.

The seminal tubes (tubuli seminiferi) are very convoluted, and
are but slightly held together by fine areolar tissue and surrounding
blood-vessels, so that they may be readily drawn out of the testis
for some distance : their length is about two feet and a quarter
(Lauth). Within the lobes of the testis some tubes end in distinct
closed extremities ; but the rest communicate, forming loops or
arches. Their diameter varies from x^iyth to j^^th of an inch.
The wall of the tube is formed of a thin translucent membrane, but
it has considerable strength.

Names of the different parts of the tubes. To different parts of the
seminal tubes, the following names have been applied. Where the
tubules are collected into masses, they form the lobes of the testis.
As they enter the fibrous mediastinum they become straight, and
are named tubuli recti. Communicating in the mediastinum they
produce the rete testis. And, lastly, as they leave the upper end
of the gland they are convoluted, and are called vasa efferentia, or
coni vasculosi.

The lobes of the testis (fig. 104, a) are formed by bundles of the
seminiferous tubes, and are situate in the intervals between the
processes of the tunica albuginea. From 100 to 200 in number
(Krause), they are conical in form, with the base of each at the
circumference, and the apex at the mediastinum testis ; and those
in the centre of the testicle are the largest.

Each is made up of two or more tortuous seminal tubules ; and
the minute tnbes in one lobe are united with those in the neighbour-
ing lobes. Towards the apex of each lobe the tubules become less
bent, and are united together ; and the tubuli of the several lobes
are farther joined at the same spot into the tubuli recti.

Tubuli recti (fig. 104, c). The seminal tubes uniting together
become narrower and straighter in direction, and are named tubuli
recti or vasa recta : they pierce the fibrous mediastinum and enter
the rete testis.

Eete testis (fig. 104, e). In the mediastinum the seminal tubes have
no proper walls (beyond epithelium), and are situate in the anterior
part, in front of the blood-vessels ; they communicate freely so as to
form a network.

Vasa efferentia (fig. 104, /). From twelve to twenty tubes leave
the top of the rete, and issue from the upper end of the testicle
as the vasa efferentia : these are larger than the tubes with which
they are continuous, and end in the canal of the epididymis (part of
the common excretory duct). Though straight at first, they soon
become convoluted, and form the coni vasculosi. In the natural state
the coni are about half an inch in length, but when unravelled the

THE EPIDIDYMIS.

tubes measure six inches ; and they join the excretory duct at
intervals of about three inches.

The EXCRETORY DUCT receives the vasa efferentia from the
upper part of the gland, and extends thence to the urethra. Its
first part is in contact with the testis, is very flexuous, and forms
the epididymis ; the re-
mainder is comparatively
straight, and is the vas
deferens.

The EPIDIDYMIS (figs. 103,
6, and 104, h) extends in the
form of an arch along the
outer side of the testis, at
the back from the upper to
the lower end, and receives
its name from its situation.
Opposite the upper part of
the testicle it presents an
enlarged portion or head,
the globus major [g) ; and at
the lower end of that organ
it becomes more pointed or
tail-like — globus minor (i),
before ending in the vas
deferens. The intervening
narrow part of the epidi-
dymis is called the body {h).
The epididymis is attached
to the testis, most closely at
each end, by fibrous tissue
and by the reflection of the
tunica vaginalis, the globus
major also being attached
by the vasa efferentia.

The epididymis is formed
of a single tube, bent in a
zigzag way, the coils of
which are united into a

solid mass by fibrous tissue. After the removal of the serous mem-
brane and some fibrous tissue this part of the tube may be uncoiled ;
it then measures twenty feet or more in length. The diameter of its
canal is about yUh of an inch, though there is a slight diminution in
size towards the globus minor ; but it increases again as it approaches
the vas deferens.

The VAS DEFERENS (fig. 104, k) begins opposite the lower end of
the testis, at the termination of the globus minor of the epididymis.
At first the duct is slightly wavy, but afterwards it becomes for the
most part a firm, round, and direct tube ; near its termination it is
enlarged again and sacculated, as will be seen later.

281

Excretory
duct ill
two parts.

Epididymis
consisting

of head,

Fig. 104. — Vertical Section of the Testis
TO SHOW the Arrangement op the
Septa and Seminal Tubes.

a. Lobes of the testis.

b. Septa between the lobes.

c. Tubuli recti.

d. Mediastinum testis.

e. Rete testis.

/. Vasa efferentia.
g. Globus major.

h. Body, and i, globus minor of the
epididymis.

k. Vas deferens.
I. Vas aberrans.

Horizontal Section.

taU,

and body;
how fixed

Rete testis, in section.

P-
r.

Finer septa.
Epididymis, cut across.
Mediastinum, cut across.

formed of
coiled tube

length and
size.

Vas
deferens :

282

DISSECTION OF THE ABDOMEN.

course to
urethra :

length and
size.

Vas aberrans
frequently
present :

situation,

and size.

Three coats
form the
duct : a
fibrous,

a muscular,

In its course to the urethra it ascends over the hinder part of the
testicle, on the inner side of the epididymis, and then along the
blood-vessels of the spermatic cord, with which it enters the internal
abdominal ring ; here it bends downwards round the epigastric
artery, as has already been seen, and is then continued behind the
bladder (p. 389), and through the prostate to open into the urethra.
The length of this part of the excretory duct is about two feet, and
the width of its canal about ^ th of an inch.

Opening into the vas deferens, at the angle of union with the
epididymis, there is frequently a small, narrow, csecal appendage, the
vas aherrans of Haller (fig. 104, I). It is convoluted, and projects
upwards for one or two inches amongst the vessels of the cord.
Like the epididymis, it is longer when it is uncoiled. Its capacity
is greatest at the free end.

Structure. The vas deferens has a thick muscular coat, which is
covered externally by fibrous tissue, and lined internally by mucous
membrane. To the feel the duct is firm and wiry, like whip-cord.
On a section its wall is dense and of a rather yellow colour.

The muscular coat is composed of longitudinal and circular fibres
arranged in strata. Both extenially and internally is a longitudinal
layer, the latter being very thin ; and between them is the layer of
circular fibres.

The mucous membrane is marked by longitudinal folds in the
straight part of the canal, and by irregular ridges in the sacculated
portion.

Organ of Giraldes. In the spermatic cortl of the fcetus and child, and some-
times in the adult, a small whitish, granular-looking body may be recognised,
which is named the organ of Giraldes, or the paradidymis. It consists of
several small masses of convoluted tubules which appear to be remnants of
the lower part of the Wolffian body.

Blood-vessels and nerves of the testicle. The branches
of the spermatic artery supply offBets to the epididymis, and enter
the posterior part of the mediastinum. The vessels are finely
divided in the vascular structure lining the interior of the tunica
albuginea, before being distributed to the lobes of the testis.

The spermatic vein results from the union of branches issuing
from the back of the testicle and the epididymis. As it ascends
along the cord its branches form the spermatic or pavijnniform plexus.
On the right side it joins the vena cava, and on the left the renal
vein.
Lymphatics The lymphatics of the testicle ascend on the blood-vessels, and join
the lumbar glands.

The nerves are derived from the sympathetic, and accompany the
artery to the testis.

Vessels of the vas deferens. A special artery is furnished to the
vas from the upper or lower vesical, and reaches as far as the testis,
where it anastomoses with the spermatic artery. Veins from the
epididymis enter the spermatic vein. The nerves are derived from the
hypogastric plexus.

and a
mucous.

Organ of
Giraldds :

remains of

Wolffian

body.

Spermatic
artery.

Spermatic
vein.

and nerves.

Ves,<iels of
the duct.

VESSELS OF THE ANTERIOR ABDOMINAL WALL, 283

Dissection of the abdominal wall renewed. The dissection of Dissection
the anterior abdominal wall will now be resumed. By raising tlie ^ ^^P*^^ >
stump of the spermatic cord from over the pubis towards the internal
abdominal ring, a fibrous band below Poupart's ligament, the deep
crural arch, will appear : it passes inwards to the pubis, and is to
be defined with some care.

The remaining vessels of the abdominal wall, viz., the deep epi- and of the
gastric and circumflex iliac, and the ending of the internal mammary thrwall°f
artery, are to be next dissected. The epigastric and mammary abdomen,
arteries will be found on raising the outer edge of the rectus, (me
at the upper end, and the other at the lower.

The epigastric, with its earliest branches, may be traced by
removing the transversalis fascia from it near Poupart's ligament.
The circumflex iliac artery lies behind the outer half of Poupart's
ligament, and should be pursued along the iliac crest to its ending. ^

Deep crural arch (fig. 97, p. 263). Below the level of Poupart's Deep crural
ligament is a thin band of transverse fibres over the femoral vessels, ^^^
which has received the name deep crural arch from its position and
resemblance to the superficial crural arch (Poupart's ligament), attach-
This fasciculus of fibres, beginning about the centre of the ligament, ™^"*^^-
is prolonged inwards to the pubis, where it is widened, and is
inserted into the pectineal line at the deep aspect of the conjoined
tendon of the broad muscles of the abdomen. It is closely connected
with the front of the crural sheath.*

Vessels in the Wall of the Abdomen. On the side of the Vessels in
abdomen are some of the intercostal and lumbar arteries with the waU.
nerves. In the sheath of the rectus lie the deep epigastric and
internal mammary vessels. And running along the crest of the ilium
is the circumflex iliac branch.

The intercostal arteries of the lowest two spaces issue intercostal
between the corresponding ribs, and enter the abdominal wall
betw-een the transversalis and internal oljlique muscles : they extend
forwards with the nerves, supplying the contiguous muscles, and
forming anastomoses with the internal mammary, epigastric and
lumbar arteries.

Lumbar arteries. The anterior branches of the lumbar arteries Lumbar
supply the muscles in the hinder part of the abdominal wall, and
anastomose with the foregoing arteries above, with the circumflex
iliac and ilio-lumbar arteries below. The highest artery accom-
panies the last dorsal nerve below the twelfth rib, and is distributed
with the nerve. From the lowest lumbar artery a branch passes to
the integuments with the iliac part of the ilio-hypogastric nerve.

Internal mammary artery. The abdominal branch of this Superior
vessel is called the superior epigastric, and enters the wall of aSen^!^"*'

* Sometimes this structure is a firm distinct band, which is joined by some
of the lower fibres of the aponeurosis of the external oblique. At other times,
and this is the most common arrangement, it is only a thickening of the
transversalis fascia, with fibres added from the tendon of the transversalis
muscle.

Inferior
or deep
epigastric
artery :

relations
in wall of
abdomen.

Branches :

pubic joins
obturator ;

284 DISSECTION OF THE ABDOMEN.

the abdomen beneath the cartilage of the seventh rib. Descend-
ing in the sheath of the rectus, it soon enters the substance of
the muscle, and anastomoses in it with the epigastric artery.
Branches are given to the neighbouring muscles and the overlying
integument.

The DEEP EPIGASTRIC ARTERY (fig. 106, CI, p. 287) arises from the
external iliac about a quarter of an inch above Poupart's ligament ;
it ascends in the sheath of the rectus, and above the umbilicus
divides into branches which enter that muscle, and anastomose with
the superior epigastric.

As the artery courses to the rectus it passes beneath the spermatic
cord (or round ligament of the uterus), and on the inner side of the
internal abdominal ring ; and it is directed obliquely inwards across
the lower part of the abdomen, so as to form the outer boundary of
a triangular space along the edge of the rectus. It lies at first
beneath the transversalis fascia ; but it soon perforates that mem-
brane, and enters the sheath of the rectus over the semilunar fold
of Douglas.

The branches of the artery are numerous, but small in
size : —

a. The pubic branch is a small artery, which runs transversely
behind Poupart's ligament to the back of the pubis, where it anasto-
moses with the similar branch of the opposite side, and with an
offset from the obturator artery (fig. 107,/, p. 294). The size of the
anastomosis with the obturator artery varies very much, but it is
often so large that the obturator artery is derived wholly or in part
from the deep epigastric through the enlargement of its pubic
branch, giving rise to the commonest form of an abnormal obturator
artery.

b. A cremasteric branch is furnished to the muscular covering of
the cord.

c. Muscular branches are given from the outer side of the artery
to the abdominal wall, and anastomose with the intercostal and
lumbar arteries ; others enter the rectus.

d. Cutaneous offsets pierce the muscle, and ramify in the integu-
ments with the anterior cutaneous nerves.

Two epigastric veins lie with the artery ; they join finally into
one, which opens into the external iliac vein.

The DEEP CIRCUMFLEX ILIAC ARTERY arises from the outer j side of
the external iliac, opposite, or a little below the deep epigastric. It
runs at first over the iliacus, close behind Poupart's ligament, in a
fibrous sheath at the junction of the iliac and transversalis fasciae,
and then along the inner margin of the iliac crest to about the middle,
where it ends by anastomosing with the iliac branch of the ilio-
lumbar artery.

offsets, Branches. Near the front of the iliac crest a branch (fig. 106,

6, p. 287) ascends between the internal oblique and transversalis

muscular, muscles, supplying them, and anastomosing with the epigastric and
lumbar arteries.

cremas-
teric :

muscular

cutaneous.

Epigastric
veins.

Circumflex
iliac artery

DISSECTION OF THE INGUINAL REG ION. 285

As the vessel extends backwards it gives lateral offsets, which and anasto-
supply the neighbouring muscles, and communicate on the one side ™°^^*''
with the ilio-lumbar, and on the other with the gluteal artery.

The deep circumjlex ilmc vein is formed by the junction of two Circumflex
collateral branches, and crosses the external iliac artery nearly an ^^^^ ^^'""
inch above Poupart's ligament, to open into the external iliac vein.

Section II.

HERNIA OF THE ABDOMEN.

The lower part of the abdominal wall, which has been reserved inguinal
on the left side of the body, should now be dissected for inguinal
hernia.

Dissection. The integuments and the aponeurosis of the external The dissec-
oblique having already been reflected, the necessary dissection of lefTgroin.^
the inguinal region will be completed by raising the internal oblique
muscle as in fig, 106.

To raise the internal oblique muscle, let one incision be made across Reflect
the fleshy fibres from the iliac crest towards the linea alba ; and oblique,
after tlie depth of the muscle has been ascertained by the layer of
areolar and fatty tissue beneath it, let the lowest fibres be carefully
cut through at their attachment to Poupart's ligament. By lifting
up the muscle cautiously, the student will be able to separate it
from the subjacent transversalis so that it may be turned inwards
on the abdomen. The separation of the two muscles just mentioned
is often diflficult in consequence of their lowest fibres being blended
together, but a branch of the deep circumflex iliac artery serves as a
guide to the intermuscular interval.

The cremaster muscle is next to be divided along the cord, and Cut the
to be reflected to the sides. Let the dissector then clean the surface ^^^^^ ^^•
of the transversalis muscle, without displacing its lower arched H^,^nt parts,
border, and define with care the conjoined tendon of it and the
internal oblique to show its exact extent. The transversalis fascia
and the spermatic cord should also be nicely cleaned.

Crossing the interval below the border of the transversalis muscle show the
are the deep epigastric vessels, which lie close to the inner side of the ^Sis"*^
internal abdominal ring, but beneath the transversalis fascia. A
small piece of the fascia may be cut out to show the vessels.

Inguinal Hernia. A protrusion of intestine or other organ situation
through the lower portion of the abdominal wall near Poupart's hemS!^^
ligament (answering to the inguinal region) is named an inguinal
hernia. The escape of the intestine in this region is favoured by Predis-
the deficiencies in the muscular strata, by the passage of the sper- nat^Uy.
matic cord through the abdominal parietes and by the existence of
fossae on the inner surface of the wall.

The gut in leaving the abdomen either passes through the internal Course it
abdominal ring with the cord, or is projected through the part of ^°^^°^^-

286

DISSECTION OF THE ABDOMEN.

Two kinds

external or
oblique ;

the abdominal wall between the epigastric artery and the edge o
the rectus muscle. These two kinds of hernia are distinguished b}
the names external and internal, from their position to the dee}
ej^igastric artery ; or they are called oblique and direct, from th(
direction they take through the abdominal wall. Thus, the hernia
protruding through the internal abdominal ring with the cord is
called external from being outside the artery, and oblique from its
slanting course ; while the hernia between the edge of the rectus

Posterior layer
of sheath of
rectus.

Transversalis.
Cut edge of
anterior layer
of sheath of
rectus.

Semilunar fold
of Douglas.
Transversalis
fascia.

Spermatic
cord.

Conjoined
tendon.

Fig. 105. — Diagram of the Internal Oblique and Transversalis
Muscles, with the Sheath of the Rectus.

internal or
direct.

External or
oblique.

Anatomy of
parts con-
cerned.

Inguinal
canal :

and the deep epigastric artery is named internal from being inside
the artery, and direct from its straight course.

External or Oblique Inguinal Hernia leaves the cavity of
the abdomen with the spermatic cord, and traversing the inguinal
canal, makes its exit from that passage by the external abdominal
ring.

Anatomy of external hernia. To understand the anatomy of
this form of hernia, it will be necessary to study the passage which
it occupies in its course through the abdominal wall (inguinal canal),
the apertures by which it enters and leaves the wall (abdominal
rings), and the coverings it receives in its progress.

The INGUINAL CANAL (figs. 105 and 106) is the interval between
the fiat muscles of the abdominal wall, which contains the spermatic
cord in the male, and the round ligament of the uterus in the female.

THE INGUINAL CANAL.

287

It extends from the internal to the external abdominal ring, and extent,
measures about one inch and a half in length. From its beginning length and
I the internal ring, it is directed obliquely downwards and inwards, direction;
ing placed above, and nearly parallel to, the inner half of
Poll part's ligament.

Its antenor wall is formed by (1) the integuments and (2) by walls in
the aponeurosis of the external oblique muscle (fig. 106) for ^^ '

Fig. 106. — Dissection for Inguinal Hernia (iLLrsxRATiONS op Dissections).

Muscles, d-c. :

A. External oblique tendon, thrown
down.

B. Internal oblique, the lower
part raised.

c. Cremaster muscle iu its natural
position.

D. Transversalis muscle with a
free border.

p. Spermatic cord, surrounded by
the infundibuliform fascia.
G. Transversalis fascia.
H. Conjoined tendon.

Arteries :

a. Epigastric.

b. Offset of the circumflex iliac

its whole extent, and (3) by the internal oblique in its outer and behind ;
third.

Its posterior wall is formed by (I), the peritoneum, sub-peritoneal
tissue and transversalis fascia (g) throughout its whole length,
(2) by the conjoined tendon (h) of the internal oblique and trans-
veKalis muscles in its inner two-thirds, and (3) by the triangular

288

floor,
and roof.

Canal in the
female.

Internal

abdominal

ring:

situation,

form and
margin ;

relations';

parts trans-
mitted
through it.

External

abdominal

ring:

situation.

The intes-
tine, follow-
ing the
course of
the cord,

has cover-
ings of the
peritoneum
and fat,
transver-
salis fascia,

cremaster,

spermatic
fascia,
superficial
fascia and
skin;

DISSECTION OF THE ABDOMEN.

fascia derived from the external oblique behind the external
abdominal ring (fig. 97, p. 263).

Its floor is formed (1) by the meeting of the transversalis fascia
with Poupart's ligament, and (2) by the fibres of Poupart's ligament
inserted into the pectineal line (Gimbernat's ligament). Its roof is
formed (1) by the meeting of its anterior and posterior walls, and (2)
by the lower arched borders of the internal oblique and transversalis.

In the female, the canal has the same boundaries, but is usually
somewhat longer and narrower. In that sex it lodges the round
ligament.

The internal abdominal ring (fig. 106) is an aperture in the
transversalis fascia, which is situate midway between the symphysis
pubis and the anterior superior iliac spine, and half an inch above
Poupart's ligament. It is oval in form ; and its longest diameter,
which is directed vertically, measures about half an inch ; the
fascia at its outer and lower parts is stronger than at the opposite
sides.

Arching above and on the inner side of the aperture is the lower
border of the transversalis muscle (d), which is fleshy in the outer
but tendinous in the inner half. Beloio is Poupart's ligament,
which separates the aperture from the external iliac artery. On the
inner side its limit is best marked, being formed by the deep
epigastric vessels.

This opening in the transversalis fascia is the inlet to the inguinal
canal, and through it the cord, or the round ligament, passes into
the wall of the abdomen. An external hernia enters the canal at
the same spot, and all the protruding parts receive as a covering
the prolongation (infundibuliform fascia) from the fascial margin
of the opening.

The external abdominal ring (fig. 97) is the outlet of the inguinal
canal, and through it the spermatic cord reaches the surface
of the body. This aperture is placed in the aponeurosis of the
external oblique muscle, near the crest of the pubis ; and from the
margin a prolongation (spermatic fascia) is sent on the parts passing
through it (p. 267).

Course and coverings op an external, or oblique hernia.
A piece of intestine leaving the abdomen with the cord, and passing
through the inguinal canal to the surface of the body, will obtain a
covering from every stratum of the wall of the abdomen in the groin,
except from the transversalis muscle.

It therefore receives its investments in this order : — As the intestine
is thrust forwards, it carries before it first the peritoneum and the
subperitoneal fat, and enters the tube of the infundibuliform fascia
around the cord. Still increasing in size, it is forced downwards to
the lower border of the internal oblique muscle, where it has
the cremasteric fascia applied to it. The intestine is next directed
along the front of the cord to the external abdominal ring, and in
passing through that opening receives the investment of the inter-
columnar or spermatic fascia. Lastly, as the hernia descends towards

EXTERNAL OR OBLIQUE HERNIA. 289

the scrotiim, it has the additional coverings of the superficial fascia
and the skin.

In a hernia which has passed the external abdominal ring, the seven in
coverings from without inwards are therefore the following : — the
skin and superficial fa.scia, the spermatic and cremasteric fasciae
the infundibuliform fascia, the subjjeritoneal tissue, and the peri-
toneum or hernial sac. Two of the coverings, vdz., the peritoneal ^J^^^^''*'-
and subperitoneal, originate as the gut protrudes ; but the rest are
ready formed round the cord, and the intestine slips inside them.
The different layers become much thickened in a hernia that has
existed for some time.

Diaqnosis. If the hernia is .^mall. and is confined to the wall of Howtodis-
the belly, it gives rise to an elongated swellmg along the mgumal
canal. If it has proceeded farther, and entered the scrotum, it
forms a flask-shaped tumour with the large end below, and the
narrow neck occupying the inguinal passage.

Should a hernia of this kind l>ecome strangulated, the seat of stricture :
stricture is placed usually at the internal abdominal ring, and may where
be produced either by a constricting fibrous band outside the narrowed ^' ^
neck of the tumour, or by a thickening and contraction of the
peritoneum itself at the inner surface of the neck.

Dwisian of stricture. In division of the stricture, with the view of To relieve,
avoiding the surrounding vessels, the cut is directed upwards on the
front and mid-part of the hernia.

Varieties of external liemia. There are two varieties of oblique Two
inguinal hernia that may be mentioned (congenital and infantile), in ^*"® ^^^'
addition to the ordinary acquired type above described ; they are
distinguished by the condition of the peritoneal covering.

Congenital hernia. This kind is found for the most part in the Congenital
infant and the child, though it may occur in the adult male. In it
the tube of peritoneum (processus vaginalis), which receives the
testicle in the foetus, remains unclosed and the intestine descends into how eon-
a sac already formed for its reception.

Infantile or encysted hernia is much rarer than congenital, and infantile
cannot be distinguished from the common external hernia during ^^^^'^ •
life. It was first recognised in the young child, and received its
name of infantile from that circumstance ; but it may be met with
at any period of life.

This form of hernia occurs when the fcetal processus vaginalis of how con-
the peritoneum is closed only in the neighbourhood of the internal
abdominal ring, instead of being obliterated from that point down
to the testicle, so that a large serous sac will be situate in front of
the spermatic cord, and may occupy the inguinal canal. "With this
state of the peritoneum, should an external hernia with its coverings
descend along the cord in the usual way, it will pass behind the
unobliterated sac, like a viscus in a serous membrane. In this way
there will be two sacs, an anterior (the tunica vaginalis) containing
serum, and a posterior enclosing the intestine.

An infantile hernia is first recognised during an operation by

D.A. U

290 DISSECTION OF THE ABDOMEN.

the knife opening the tunica vaginalis before the sac of the
hernia.

iiitenial INTERNAL or DiRECT INGUINAL Hernia escapes on the inner

leruia. ^^^^ ^^ ^^^q deep epigastric artery, and has a straight course through

the abdominal parietes. Its situation and coverings, and the seat of
stricture, will be understood after the examination of the part of the
abdominal wall through which it passes.
Triangle of An ATOMY OF INTERNAL HERNIA. In the abdominal Wall near the
botmdaries ;" pubis is a triangular space to which the name of Hesselbach's triangle
has been given. This is bounded by the deep epigastric artery ex-
ternally, the outer edge of the rectus muscle internally, and the inner
size; part of Poupart's ligament below ; it measures about two inches

from above down, and one inch and a half across at the base,
constituents The constituents of the abdominal wall in this area are — the
* integuments, the muscular strata, and the layers lining the interior
of the abdomen, viz., transversalis fascia, subperitoneal tissue, and
peritoneum. The muscles have the following arrangement : — The
anddisposi- aponeurosis of the external oblique is pierced by the external
muscles. abdominal ring, towards the lower and inner angle of the space.
The internal oblique and transversalis, which come next, are united
together in the conjoined tendon ; and as this descends to its inser-
tion into the pectineal line it covers the inner two-thirds (about an
inch) of the space, and leaves uncovered about half an inch between
its outer edge and the epigastric vessels, where the transversalis
fascia appears.
Hernia in Any intestine protruding in this spot must make a new path for
two mS."*^ itself, and elongate the different structures, since there is not any
passage by which it can descend, like an external hernia. Further,
the coverings of the hernia, and its extent and direction in the
abdominal wall, must vary according as the gut projects through the
portion of the space covered by the conjoined tendon, or through
the part external to that tendon.
Coverings Course and coverings of the hernia. The commoner kind of in-

common^^^ ternal hernia passes through the part of the triangular space which
kind are is covered by the conjoined tendon.

peritoneum The intestine in protruding carries before it the peritoneum, the
centSsue subperitoneal fatty membrane, and the transversalis fascia ; next it
transver- ' elongates the conjoined tendon, or, in the case of a sudden rupture,
conjoined ' separates the fibres and escapes between them. It then advances
tendon, Jjj^q ^-j^^ lower part of the inguinal canal, opposite the external
spermatic abdominal ring, and passes through that opening on the inner side
superficial ^^ *^^^ cord, receiving at the same time the covering of the spermatic
fascia, and fascia. Lastly, it is invested by the superficial fascia and the skin.
In number the coverings of an internal hernia are the same as
those of an external ; and in kind the only differences are that the
covering of transversalis fascia is not furnished by the infundibuli-
form process, and the conjoined tendon is substituted for the cremas-
teric fascia.

The position of the oj^enings in the abdominal wall, and the

INTERNAL OR DIRECT HERNIA. 291

straightness of its course, should be kept in mind during attempts to
reduce this kind oi' hernia.

Diagnosis. This rupture will be distinguished from external How known
hernia by its straight course through the abdominal wall, and by the Jiai™ ^^^^^'
neck being placed close to the pubis, but when an inguinal hernia impossible
has attained a large size, it is impossible to tell by an external *^ *^ ^'^ ^*^8*^-
examination whether it began originally in the triangular space, or
at the internal abdominal ring ; for as an external hernia increases,
its weight drags the internal ring inwards into a line with the
external, and in this way the swelling acquires the appearance of a
direct rujiture.

^ieat of stricture. The stiicture in this form of hernia occurs most Stricture :
frequently outside the neck of the tumour, at the opening that has
been formed in the conjoined tendon, though it may be inside from
thickening of the peritoneum ; and it may occasionally be found at situation ;
the external abdominal ring.

In dividing the stricture of a large rupture which appears to be in large
direct, the cut should be made directly upwards in the middle of the ^'"™^-
front of the tumour, so as to avoid the deep epigastric vessels, the
position of which cannot be ascertained.

Variety of internal hernia. Another kind of internal hernia Rarer kintl

(superior) occurs through that part of the area of the triangular hernia"**

space which is external to the conjoined tendon. The intestine is oblique in

protrudes through the wall of the abdomen close to the deep epigastric ^vm^ the

artery, and descends along nearly the whole of the inguinal canal conl.

to reach the external abdominal ring ; so that the term " direct "

would not apply strictly to this form of internal hernia.

Coverings. As the gut traverses nearly the whole of the inguinal Coverings
1 . , i' . 1 • i. 1 1 • are same as

canal, it has the same coverings as an external hernia. in extenial

Division of the stricture. From an inability to decide always in l^^^mia-
the living body whether a small hernia is internal or external, the SSure^^
rule observed in dividing the stricture of the neck of the sac is, to
cut down upon the mid-part of the tumour ; and if it is necessary
to open the peritoneum, to cut directly upwards, as in the other
kinds of inguinal hernia.

Umbilical Hernia, or exomphalos, is a protrusion of the intestine Umbilical

throns;h or by the side of the umbilicus. It is very variable in size,

course *

and its course is straight through the abdominal wall.

Coverings. The coverings of the intestine are — the skin and super- coverings
tieial fascia, a prolongation from the tendinous margin of the aperture
in the linea alba, together with coverings of the trans versalis fascia,
the subperitoneal fat, and the peritoneum. Over the end of the become
tumour the superlicial fascia blends with the other contiguous struc- the^tumour
tures, and its fat disappears.

If the hernia is suddenly produced, it may want the investment changes in ;
otherwise derived from the edge of the umbilicus.

Seat of stricture. The stricture on the intestine is generally at the stricture,
margin of the tendinous opening in the abdominal wall ; and it may Jo„n^^^
be either outside, or in the neck of the sac, as in the other kinds of

U 2

292 DISSECTION OF THE ABDOMEN.

hernia. It should be remembered that the narrowed neck is at the
upper end and not in the centre of the swelling,
other Other Forms of HER^'IA. At each of the other apertures in the

herniS"are parietes of the abdomen, a piece of intestine may be protruded, so
femoral, as to form a hernia. For instance, there may be femoral hernia below
obturator, Poupart's ligament, with the femoral vessels ; obturator hernia
sciatic. through the thyroid foramen, with the artery of the same name ; and

sciatic hernia through the sciatic notch.

The femoral hernia, as the most important, will be noticed
presently ; but the student will refer to special treatises for detailed
information respecting the heruite.
Dissection Dissectloil. The abdomen is now to be opened to see the cords
abdomen ^^^ depressions on the posterior surface of the wall. A transverse
cut may be made through the umbilicus across the front of the
abdomen ; and on holding up the lower half of the wall, three
prominent fibrous cords, the urachus and the obliterated hypogastric
arteries, will be seen ascending to the umbilicus from the pelvis.
Cords on Cords ou the abdominal wall. In the middle line is the urachus,

nai wafh "" which readies from the summit of the bladder to the umbilicus ; on
each side is the obliterated hypogastric artery, extending from the
side of the pelvis to the umbilicus ; and a little external to the last,
near Poupart's ligament, is a less marked prominence of the perito-
neum caused by the deep epigastric artery.
Three FosscB. With this disposition of the cords, three hollows {inguinal

foS"^ fossce) are seen near Poupart's ligament, one internal to the obliterated
hypogastric artery, another outside the deep epigastric artery, and
external, the third between the two. The external fossa corresponds by its
lower and inner part to the internal abdominal ring, opposite which
there is often a slight depression or dimple of the peritoneum, and is
the place where an external inguinal hernia begins to protrude. The
internal, internal fossa is between the olditerated hypogastric artery and the
urachus ; its outer part is opposite the external abdominal ring, and
is the seat of the commoner (inferior) variety of internal hernia,
and middle. The middle fossa is the smallest, and is placed behind the inguinal
canal ; in it the superior variety of internal hernia leaves the abdo-
minal cavity.

In some bodies the obliterated hypogastric artery is close to, or

l)ehind, the epigastric artery ; and in that case the middle fossa will

be wanting.

Situation of Femoral Hernia. In this hernia the intestine leaves the

femoral abdomen below Poupart's ligament, and descends in the membranous

sheath around the femoral vessels. Only so much of the structures

will be described here as can be now seen ; the rest have been

noticed fully in the dissection of the thigh (pp. 143 et seq).

Dissection Dissectioil. The dissection for femoral hernia is to be made on

of the parts the left side of the bodv.
coiic6rn6u. ^

Divide wall ^^^ lower portion of the abdominal wall is to be divided from the
umbilicus to the pubis, the cut being made on the left side of the
urachus, and care being taken not to injure the bladder, which may

FEMORAL HERNIA, 293

project above the pubic bones. The peritoneum is to be detached detach
from the inner surface of the flap, and from the iliac fossa. The Peritoneum
layer of subperitoneal fatty tissue is to be separated in the same and fat,
way, and in doing this the spermatic vessels and vas deferens will
come into view as they meet at the internal abdominal ring to form
the spermatic cord. Beneath these the external iliac vessels are to and clean
be cleaned, with some lymphatic glands lying along them, and the ^^'^^^ ^ ^^^eis.
genito -crural nerve on the artery. (In the female the round liga-
ment of the uterus is seen entering the internal abdominal ring
round the epigastric artery ; while the ovarian vessels cross the external
iliac trunks above this dissection.) Any loose tissue remaining is
to be taken away to show the beginning of the crural sheath around
the femoral vessels, and the interval (crural ring) on their inner side
(fig. 107).

Afterwards the transversalis and iliac fasciae are to be traced to
Poupart's ligament, to see the part that each takes in the formation
of the crural sheath.

Anatomy of femoral hernia. The membranes concerned in Anatomy
femoral hernia are the peritoneum, the suljperitoneal fatty layer, the stra^tures
transverealis and iliac fasciae lining the interior of the abdominal
cavity, with the sheath on the femoral vessels to which they give
origin at Poupart's ligament.

The ijeritoneum lines the inner surface of the abdominal wall, Peritoneal
whence it is prolonged wdthout interruption into the iliac fossa and ^^^^^^'
the pelvis ; and its thinness and weakness are apparent now it is
detached.

The subperitoneal fat extends as a continuous layer beneath the Subperi-
peritoneum, but is thickest and most fibrous at the lower part of '

the abdomen, where the iliac vessels pass under Poupart's ligament.
At that spot it extends over the upper opening of the membranous
sheath around the vessels, and covers the space of the crural ring
internal to the vein.

The part of this layer which stretches over the crural ring is forms sep-
named the septum crurale ; and a lymphatic gland is generally "™ ^'^"'^ *'
attached to its under-surface.

The transversalis fascia has l)een before noticed (p. 275). At Transver-
Poupart's ligament it joins the iliac fascia outside the situation of ^ *"
the external iliac artery ; but internal to that spot it is continued
downwards to the thigh in front of the femoral vessels, and forms
the anterior part of the crural sheath.

The iliac fascia covers the ilio-psoas muscle, and lies beneath the HJac fascia,
iliac vessels. At Poupart's ligament it joins the transversalis fascia
external to the iliac vessels ; but behind the vessels it is prolonged
into the posterior part of the crural sheath.

The crural sheath is a loose membranous tube, which encloses the Sheath on
femoral vessels as they enter the thigh, and is obtained from the vessels,
fasciae lining the abdomen. Its anterior half is continuous with the
transversalis fascia, and its posterior is derived from the iliac fascia
and the pubic fascia of the thigh. The sheath is not entirely filled

294

i)Issp:ction of the abdomen.

Crui-al rini:

size ami
boundaries

by the vessels, for a space (crural canal) exists on the inner side of
the vein, through which the intestine descends in femoral hernia.
The aperture leading into the crural canal is called the crural ring.

The cniral rimj (fig. 107) is an interval at the base of the
sheath, to the inner side of the fenioral vein, and is about half an
inch wide, being filled by a lymphatic gland. Bounding it
internally are Gimbernat's ligament and the conjoined tendon ;
and limiting it externally is the femoral vein (6). In front is
Poupart's ligament, with the deep crural arch ; and behind is the
pubis, covered by the pectineus muscle and the pubic portion of
the fascia lata. Crossing the front of the space, but at some little
distance from it, is the spermatic cord in the male, and the round

Gimbernat's lii-'ament.

Crnral rinf,'.

Fig.

107. — Innkr Surface of the Os Innominatum, showikg a View of
THE Parts concerned in Femoral Hernia (R. Quain).

Muscles, dx.

iliac

A. Iliacu.s covered by the
fascia.

B. Rectus.

c. Transversalis, covered by the
transversalis fascia.

D. Crural ring.

E. Gimbernat's ligament.

Vessels :

a. External iliac artery.

b. Iliac vein.

c. Deep epigastric artery.

d. Deep circumflex iliac.

e. Obturator artery, with its nerve.
/. Anastomosis between the pubic

branches of the obturator and epi-
gastric arteries.

The opening is larger in the female than

ligament in the female,
in the male.
Constricting Two of the boundaries, anterior and inner, are firm and sharp-
edged, though their condition ^-aries with the position of the limb ;
for if the thigh is raised and approximated to its fellow, those
bounding parts will be relaxed.

Position of vessels around the ring (fig. 107). On the outer side is
the femoral vein (6) ; and above this are the deep epigastric vessels (c).
In front is a small branch (pubic) from the epigastric artery to the
back of the pubis ; and the vessels of the spermatic cord may be
said to be placed along the anterior aspect of the ring.

Unusual But in some bodies the obturator artery takes origin from the

state of J . ^ . - - '^ ^ , ,

vessels, deep epigastric by an enlargement of its communication (/) with the

boundaries,

how re-
laxed.

Usual ves-
sels around
ring.

FEMOKAL HERNIA. 295

jjubic branch of that vessel, and lies along the ring as it passes to
the pelvis. It may have two positions with respect to the crural
ring : either it is placed close to the iliac vein, so as to leave the inner
side of that space free from vessels ; or it arches over the aperture,
descending on the inner side at the base of Gimbernat's ligament ;
in this last condition the ring will be encircled by vessels except
behind.

Course of femoral hernia. The intestine leaves the abdomen by Femoral
the opening of the crural ring ; and it descends internal to the vein ^™^'
in the crural sheath, as far as the saphenous opening in. the thigh,
where it projects to the surface.

Coverings. In its progress the intestine will push before it the Coverings,
peritoneum and subperitoneal fat (septum crurale) ; and it will nmnber.
displace the gland which fills the crural ring. Having reached the
level of the saphenous opening, the intestine carries before it the
inner side of the crural sheath, and a layer called the cribriform
fascia ; and, lastly, it is invested by the superficial fascia and skin of
the thigh. The dissection of the thigh may be referred to for fuller
details (pp. 143—146).

Seat of stricture. The stricture of a femoral hernia is placed stricture
opposite the base of Gimbernat's ligament, or lower down at the neck^or at
margin of the saphenous opening in the thigh. And the constric- saphenous
tion may be caused either by a fibrous band outside the upper "'

narrow end of the tumour, or by the thickening of the peritoneum
inside the neck, as in inguinal hernia.

Division of the stricture. To free the intestine from the constricting incision to
fibrous band arching over it, an incision is to be made down to the ^rnal^'^
neck of the Siic at the inner and upper part.

And to relieve the deep stricture within the neck of the sac, and internal
the peritoneal bag is to be opened and a director introduced, and the
knife is to be carried horizontally inwards, or upwards and inwards,
through the thickened sac and a lew fibres of the edge of Gimbernat's
ligament.

Danger to vessels. When the incision is made upwards and inwards Risk of
to loosen the constricting band in the neck of the tumour, there ve^sseis^n
will not be any vessel injured unless the cut should be made so long regular
as to reach the spermatic cord in the male, or the small pubic branch
of the epigastric artery.

And when the incision is made directly inwards with the same f^^ ^^^S}}-

1 • 11 1-1 f 1 1 -I- -r. lar condition

View, there is not usually any vessel m the way ot the knire. i3ut of them,
in some few instances (once in about eighty operations, Lawrence)
the obturator artery takes its unusual course in front, and on the
inner side of the neck of the hernia, and will be before the knife in
the division of the stricture. As this condition of the vessel cannot
be recognised beforehand, the surgeon will best avoid the danger of
wounding the artery by a cautious and sparing use of the knife.

29fi

DISSECTION OF THE ABDOMEN.

Section III.

CAVITY OF THE ABDOMEN.

Definition,

and con-
tents.

Dissection
to open
abdomen.

Is largest
cavity in
the body.

Boundaries
above and
below.

in front and
on sides,

and behind.

Depth is
altered by
action of
diaphragm
and
levatores

wdth by
muscles in
wall of
abdomen.

How excreta
expelled.

Division of
space.

Abdomen
proper.

Pelvis.

Abdomen
proper here
described.

The abdominal cavity comprises the oMomen proper and the pelvis,
and is the space included between the spinal column behind and
the muscles stretching from the thorax to the pelvis in front. It is
lined by a serous membrane (peritoneum), and contains the digestive,
urinary, and generative organs, with, vessels and nerves.

Dissection. To prepare the cavity for examination, the remainder
of the abdominal wall above the umbilicus is to be divided, along the
left side of the linea alba, as far as the ensiform process. The
resulting flaps may be thrown to the sides.

Size and form. This cavity is the largest in the body. It is
ovoidal in form, with the ends upwards and downwards, so that it
measures more in the vertical than the transverse direction ; and it
is much wider above than below.

Boimdaries. Above it is limited by the diaphragm, below by the
recto-vesical fascia, the levatores ani muscles and by the other
structures closing the outlet of the pelvis. Both these boundaries are
concave towards the cavity, and are in part fleshy, so that the space
will be diminished by their contraction and flattening.

In front and on the sides the parietes are partly osseous and
partly muscular ; — thus, tow^ards the upper and lower limits is the
bony framework of the skeleton, viz., the ribs in one direction and
the pelvis in the other ; but between these the wall is formed by
the broad muscles which have been examined already.

Behind is placed the spinal column with the muscles contiguous
to it, viz., the psoas and the quadratus lumborum.

Alterations in size. The dimensions of the cavity are influenced
by the varying conditions of the boundaries. Its depth is diminished
by the contraction and descent of the diaphragm, and the contrac-
tion and ascent of the levatores ani ; and the cavity is restored to
its former dimensions by the relaxation of those muscles.

The width is lessened by the contraction of the abdominal muscles ;
but it is increased, during their relaxation, by the action of the
diaphragm forcing outwards the viscera. The greatest diminution
of the space is effected by the simultaneous contraction of all the
muscular boundaries, as in the expulsion of the excreta.

Division of the space. As already intimated a division of the space
has been made into the abdomen proper and the pelvis.

The Abdomen Proper reaches from the diaphragm to the brim
of the pelvis, and lodges nearly the whole of the alimentary tube
and its appendages, together with the kidneys.

The Pelvis is situate below the brim of the pelvis, and contains
chiefly the generative and urinary organs.

The following description concerns the part of the cavity between
the diaphragm and the brim of the pelvis. After it has been

REGIONS OF THE ABDOMEN,

297

dissected the pelvic portion will receive a separate notice (pp. 376
et seq).

Eegions of the abdomen (fig. 108). For the surface-marking
of the viscera and for the purposes of description the abdomen is

Transi

.nspuionc

The disc beCween
bhe 1^ and a™
Lximbar Vertebrae

InCer-tuberculoW
plane

Fig. 108. — Diagram showing the Regions of the Abdomen (O.A.).

R.K. Right epigastric region.
L.E. Left epigastric region.
R.H. Right hypochondriac,
L.H. Left hypochondriac.
R.xr. Right umbilical.
L.v. Left umbilical.

R.L. Right lumbar.
L.L. Left lumbar.
R.Hp. Right hypogastric.
L.Hp. Left hypogastric.
R.i. Right iliac.
L.I. Left iliac.

divided into regions by various planes. Two of the planes are
horizontal, and three vertical.

The upper horizontal plane is taken through a point half-way Tran.spy-
between the upper border of the symphysis pubis and the upper ^**"*^ V^^^-
border of the sternum. Its level may be determined with conveni-
ence and sufficient accuracy by taking a point on the surface of the
front of the bodv half-wav between the umbilicus and the notch at

298

DISSECTION OF THE ABDOMEN.

Intertuber-
cular plane.

Vertical
planes.

Names of
regions.

Other sub-
divisions.

Viscera seen
without
displace-
ment.

General
division of
alimentary
tube ;

position of
several
parts ;

and of
solid organs.

the lower border of the body of the sternum. This plane, from it.^
traversing the pyloric end of the stomach, is called the transpyloric.

The lower horizontal ylane is half-way between the transpyloric
and the upper border of the symphysis pubis, and it fairly corre-
sponds to the plane between the tubercles on the outer lips of the
iliac crest (Cunningham), and is therefore called the intertuhercular.

The vertical planes are represented by (1) the middle line of the
body, and (2 and 3) by the light and left lateral lines. These
lateral lines are drawn vertically on each side through a point mid-
way between the middle line and the anterior superior iliac spine.

The regions of the abdomen thus delimited are named respectively,
from above downwards, on either side of the middle line, the right
and left epigastric, umhilical, and Imjpogastric regions, and at the sides
of the body the right and left hypochondriac^ liimhar, and iliac regions.

In addition, the middle and lower part of the hypogastric space is
named pubic region, while the contiguous portions of the hypogastric
and iliac constitute the inguinal region.

The various bony and other surface points already referred to on
tlie superficial examination of the abdomen (p. 260) are useful in vary-
ing degrees as guides to the subjacent parts, but the arch formed
by the costal cartilages (costal margin, fig. 108) is very variable in
its position, and cannot be relied on as a surface guide except near
the sternum. Moreover, the different costal cartilages often cannot
be located in fat persons.

Superficial view. On first opening the abdomen the following
viscera appear (fig. 109, and fig. Ill, p. 303) : — Above and to
the right is the liver, which is in great part concealed by the ribs.
Lower down, and more to the left, a piece of the stomach is visible ;
but this viscus lies mostly beneath the ribs and the liver. Descend-
ing from the stomach is a loose fold of peritoneum (the great
omentum), which may reach to the pelvis, and conceal the small
intestine, but in some bodies is raised into the left hypochondriac
region, and leaves the intestine uncovered. The caecum is usually
to be seen in the right iliac region ; and sometimes a part of the
pelvic colon (sigmoid flexure) comes to the surface in the corresponding
situation on the left side.

Close behind the pubic symj^hysis is the apex of the bladder (bl),
with the urachus {ur) continued upwards from it ; and if the organ
is distended, it rises above the symphysis.

The alimentary tube presents difl:erences in form, and is divided
into stomach, small intestine, and large intestine ; and the two last
are further subdivided, as will afterwards appear. The several
viscera have the following general position : — The small intestine
is much coiled, and occupies the greater part of the cavity ; while
the great intestine arches round it. Both are held in position by
portions of the serous lining. Above the arch of the great intestine
are situate the stomach, the liver, and the spleen ; behind is the
pancreas ; and below it is the convoluted small gut. Behind the
intestine, on each side, is the kidney with its excretory tube.

RELATIONS OF STOMACH.

299

Before the natural position of the A'iscera is disturbed, their Relations of
situation in the different regions of the abdomen, and their relations ^i be seen,
to surrounding parts, should be examined.

Fig

109, — Diagram showing the PosrnoN of the Superficial
Abdominal Viscera.

The liver is shaded with horizontal, and the stomach with vertical lines.

Obliterated hypoga.stric

g b. Gall-bladder.

tr c. Tians verse colon.

1 1. Ligamentum teres of the liver.

cce. C?ecum.

o h a.
artery.

ur. Urachus.

bl. Urinary bladder.

300

DISSECTION OF THE ABDOMEN.

Position
and rela-
tions of the
stomach :

cardiac
orifice,

surface
marking
fundus :

small
curvature ;

pyloric end.

Surface
marking.

upper

and lower
surfaces ;

great curva-
ture is least
fixed part.

Changes in
form and
position ;

empty
and full
stomach.

RELATIONS OF THE VISCERA.

The STOMACH (figs. 110 and 111, j). 303) intervenes between the
gullet and the small intestine, and is partly retained in position by
folds of the serous membrane. It is somewhat pyriform in shape,
with the larger end on the left side ; and it is placed in the left
hypochondriac and epigastric regions, and reaches to the upper part
of the umbilical.

At its large end the stomach is joined by the oesophagus, whicli
fixes it to the diaphragm. The opening of the oesophagus into the
stomach, because of its nearness to the heart (from which it is only
separated by the diaphragm and pericardium), is named the cardiac
orifice, and lies behind the seventh costal cartilage of the left side,
about an inch from its junction with the sternum, being on a level
with the tenth dorsal vertebra. To the left of the orifice, the stomach
bulges upwards to its summit in the left vault of the diaphragm, and
lies behind the fifth rib in the left lateral line (fig. 111). The con-
cave border of the stomach to the right of the oesophagus is the
lesser curvature, and is attached to the liver by a fold of peritoneum
— the small omentum.

The right extremity leads into the small intestine (duodenum)
by the ^pyloric orifice, the situation of which is indicated externally
by a slight constriction of the tube, and a thickened band in the
wall that may be felt with the finger. The pyloric end of the stomach
is placed beneath the liver, a little to the right of the middle line in
the transpyloric plane, at the level usually of the disc between the
first and second lumbar vertebrae.

The upper surface (which looks also somewhat forwards) of the
stomach is in contact above and to the right with the liver, on the
left with the diaphragm, and between these with the abdominal
wall. The loiver surface (compare fig. HI and fig, 112, ^. 305) lies
over the spleen, to which it is connected by a fold of peritoneum
(gastro-splenic omentum), the lelt kidney and suprarenal caj^sule, the
pancreas, and the transverse meso-colon. This surface looks also
backwards.

The convex border or greater curvature is directed to the left
forwards and downwards, and has the great omentum attached to
it ; along it lies the transverse colon.

The form and position of the stomach vary with its degree of
distension. When the organ is empty, it is flattened, and the
pyloric end reaches but little to the right of the middle line. But
when full, the stomach becomes rounded, and its upper surface is
directed somewhat upwards and forwards, filling particularly the
left hypochondriac and epigastric regions ; the fundus pushes upwards
the diaphragm, pressing on the heart and left lung ; the great curva-
ture moves somewhat to the left and downwards, as well as forwards ;
and the pyloric extremity is carried an inch or so to the right. As
will, however, be pointed out later on, the full stomach is accommo-
dated to a great extent in a deep hollow to the left of the vertebral

SMALL INTESTINE.

301

Small
intestine:

extent and
divisions.

Duodenum ;

beginning,

to be fully
seen later.

column, which the late Professor Birmingham aptly called "the
stomach bed."

The SMALL INTESTINE reaclies from the stomach to the right iliac
region, where it ends in the large intestine. It is arbitrarily divided
into three parts, — duodeniun, jejunum, and ileum.

The duodenum comprises the tirst nine or ten inches of the small
intestine (fig. 112, i to ^, p. 305). By raising the liver it may be traced
from the pyloric end of the stomach, at first backwards and then
downwards, until it disappears beneath the transverse colon. If the
great omentum, with the attached transvei-se colon, be turned up over and ending :
the margin of the thorax, and the mass of small intestine be drawn
to the right, the lower end of the duodenum will be seen on the
left of the spine. It here ascends for a short distance, and at the
level of the second lumbar vertebra passes into the jejunum, forming
a sharp bend forwards and downwards ; — the duodeno- jejunal flexure.
The relations of the duodenum cannot, however, be satisfactorily
seen at present, and
will be examined later
(p. 327).

The jejunum and
ileuvi include the re-
mainder of the small
intestine, two-fifths be-
longing to the jejunum
and three-fifths to the
ileum, but there is no
natural division be-
tween them. This part
of the intestinal tube
forms many convolu-
tions in the umbilical,
hypogastric, left lum-
bar, and iliac regions

of the abdomen ; and it descends commonly, but more extensively in
the female, into the cavity of the pelvis. In front of the convolu-
tions is the great omentum; behind, they are fixed to the spine by a relations;
large fold of peritoneum containing the-vessels and nerves, and named
the mesentery. The termination of the ileum is more fixed than the
rest ; it ascends slightly from the pelvis to the right iliac fossa,
crossing the external iliac vessels and the psoas muscle, to open into
the large intestine just below the intersection of the intertubercular
and right lateral lines, as marked on the surfiice of the. body.

The LARGE INTESTINE or COLON (fig. Ill) is more fixed than
the jejunum and ileum, from which it is to be distinguished by

situation ;

Fig. 110. — The Stomach of a Child.

end of
ileum.

Surface
marking.

Large
intestine :
how dis-
its sacculated appearance, and by its being furnished with small tiuguished

processes of peritoneum containing fat — the appendices epiplokce.

It begins in the right iliac region in a rounded part or head course

(caecum), and ascends to the liver through the right iliac and lumbar

regions. Then crossing the abdomen below the stomach, it reaches

"R.

L Q- \:3.^^^

30^

DISSECTION OF THE ABDOMEN.

and extent.

Divisions.

Csecuiii :
position ;
relations ;

peritoneum
around it.

Junction of
ileum.

Vermiform
process.

Surface
marking.

Ascending
colon :

parts
around.

Transverse
colon :

extent and
course ;

splenic
flexure ;

arch of
colon ;

relations of
aicli :

the' left hypochondriac region ; and it lies in this transverse part of its
course in the upper part of the umbilical regions. Finally, it
descends, on the left side, through the regions corresponding with
those it occupied on the right, and forms a remarkable bend in the
pelvis on the left side ; then becoming straight (rectum), it passes
through the pelvis to end on the surface of the body.

It is divided into seven parts, viz., caecum, ascending colon, trans-
verse colon, descending colon, iliac colon, pelvic colon, and rectum.

The ccecum is placed in the right iliac fossa, above the outer half
of Poupart's ligament, descending below the level of the anterior
superior iliac spine in the right lateral line. When empty it may
be entirely covered by the convolutions of the small intestine ; but
frequently, more or less distended, it rests against the anterior
abdominal wall. The caecum is as a rule entirely surrounded by
peritoneum, which sometimes forms a small fold behind it ; but
occasionally it is closely bound down by the peritoneum being
reflected off each side, so as to leave the hinder surface uncovered,
and connected to the iliac fascia by areolar tissue.

This j)art of the large intestine is joined at its inner and posterior
aspect by the termination of the ileum, which marks the division
between the caecum and ascending colon. Attached to the inner part of
the posterior surface of the crecum is a slender worm-like process — the
vermiform appendix. This process is usually directed downwards and
to the lelt under cover of the caecum, to which it is connected l)y a
fold of peritoneum. The root of the appendix (where it joins the
caecum) is marked on the surface of the body by a point an inch below
the centre of a line drawn from the anterior superior iliac spine to
the umbilicus.

The ascending colon reaches from the caecum to the under-surface
of the liver, where the intestine makes a l>end known as the hepatic
flexure. It lies against the iliacus and quadratus lumborum muscles,
and in its upper part along the outer border of the kidney. In front
and to its inner side are the convolutions of the small intestine. The
peritoneum fixes the ascending colon to the wall of the abdomen,
and surrounds commonly about two-thirds of its circumference ;
but it may encircle the tube and form a fold behind it (ascending
meso-colon).

The transverse colon begins at the hepatic flexure, forming a loop
downwards in the right lateral plane as far as the level of the
umbilicus, and then passes across to the left and upwards, along
the great curvature of the stomach, as far as the spleen. Here
a bend, directed mainly backwards, is formed in the lower part of
the left hypochondriac region at the junction with the descending
colon, sharper than that on the right side, and named the splenic
flexure.

In this course the transverse colon is deeper at each end than in
the middle, and thus forms the arch of the colon, which has its
convexity directed forwards. Above the arch are placed the liver
and gall-bladder, the stomach, and the spleen ; and below, the

RELATIONS OF INTESTINE.

303

convolutions of the small intestine. In passing from right to left,

as will be seen by comparing figs. Ill and 112, the transverse colon

first lies over the right kidney and the second part of the duodenum,

and is fixed to these organs by its peritoneum, which is arranged like dispositioD

that of the ascending colon. Beyond the duodenum however, it is only toiimun.

loosely attached to the l)ack of the abdomen liy a long fold of

LJj. Liver.

Trdmapuloric

Inter-Cubercular ,

Fig. 111. — Diagram showing the Disposition of the Liver, the Stomach,
THE Large Intestine, and the Lines of Peritoneal Attachment,
IN the Regions of the Abdomen (C. A.).

M.L. Middle line. l.l. Lateral lines.

Disc line represents the disc between the first and second lumbar

vertebrae.

peritoneum, the transverse meso-colon (fig. 114, mc^ p. 309) ; wbile
the great omentum (^f om\ which passes between it and the stomach,
covers it in front.

The descending colon extends from the spleen to the iliac crest,
and is longer than the ascending part. At first it is placed deeply Descending
in the left hypochondriac region, resting against the diaphragm, and
partly concealed by the stomach. Lower down, it has the small situation ;
intestine in front and the quadratus hmiborum behind. Along the
inner side, it is closely applied to the outer part of the left kidney.

304

DISSECTION OF THE ABDOMEN.

and peri
toneum.

Iliac colon.

Rectum.

Position of

This part of the colon is smaller than either the ascending or the
transverse portion, and is commonly less surrounded by the perito-
neum ; its upper end is attached to the diaphragm by a special fold
(phrenico-colic) of that membrane.

The iliac colon begins at the iliac crest, and descends in the left iliac
fossa, over the ilio-psoas muscle and the external iliac vessels, being
fixed in this position by the peritoneum, until it reaches the
brim of the pelvis. Here the intestine forms a large loop, which
is provided with a long process of peritoneum, and becomes the
Pelvic colon, freely movable pelvic colon. The pelvic colon commonly hangs
down as a loop in the cavity of the pelvis ; but it often projects
forwards and reaches the anterior wall of the al)domen. Below the
brim of the pelvis, opposite the third sacral vertebra, it ends in the
rectum.

The rectum, or the termination of the large intestine, is contained
in the pelvis, and will be examined in the dissection of that cavity.

The LIVER (figs. 109 and 111) is situate in the right hypochondriac
and lumbar and the epigastric regions, and often reaches slightly into
the left hypochondriac, the left extremity being usually behind the
junction of the left sixth rib with its cartilage. It is covered in front
by the ribs with their cartilages, except over a small area in the sub-
costal angle. Folds of peritoneum, called ligaments, attach it to the
abdominal parietes.

The wpyer surface fits against the diaphragm, and is convex on
each side, but slightly hollowed in the centre below the heart. It
extends higher up on the right side than on the left, and reaches
the level of the fifth rib in the right lateral plane.

The anterior surface is most seen at present, and passes in-
sensibly into the upper surface above, and terminates at the
well-marked lower border below. This surfece is in contact with the
diaphragm under cover ol the ribs and costal cartilages, and, between
the costal arches, with the anterior abdominal wall. It is divided
into two parts, corresponding to the right and left lobes of the organ,
by the falciform ligament.

The superior and anterior surfaces pass insensibly into the right
surface where the liver lies against the diaphragm on the right side
and sometimes projects below the ribs at their lower part against the
abdominal wall,
and inferior. The inferior surface looks downwards, to the left, and somewhat
backwards ; it is in contact with the stomach, the first and second parts
of the duodenum, the small omentum, the gall-bladder, the right
kidney, and the l:)eginning of the transverse colon. To this surface
the small omentum, containing the hepatic vessels, is attached.

The lower border is thin and directed downwards. On the right
side it is concealed by the ribs ; but in the epigastric region it is
exposed, running obliquely from the ninth right to the eighth left
costal cartilage : it crosses the middle line of the body a little above
the transpyloric plane. The fundus of the gall-bladder projects
beyond this edge, close to the costal margin in the right lateral plane.

surfaces
upper,

right,

lower
border.

EELATIONS OF LIVER.

305

The remaining surface of the liver, the posterior, cannot be seen at
present. The left lobe lies in front of the oesophagus, and is attached
to the diaphragm by a triangular fold of peritoneum — the left lateral
ligament. The two layers of peritoneum fixing the right lobe are for Peritoneal
the most part widely separated, and constitute the coronary ligament ; ments
but at the right end they come together, and give rise to a small
triangular fold wbich is distinguished as the right lateral ligament

Tran spuloric

The disc bebw^rT
Che 1^ cLnd z."9
Liv rn bar VerCeb ras .

I nCer-bubercu I au-
plane.

Fig. 112.-

-DlAGRAM SHOWING THE DISPOSITION OF THE DeEP OrGANS IN

THE Regions op the Abdomen (C.A.).
1, 2, 3 and 4 denote the four parts of the duodenum.

The portion of the surface between the layers of the coronary ligament
is adherent directly to the diaphragm by means of areolar tissue : in
this space also the right suprarenal capsule touches the liver ; and
the inferior vena cava is embedded in a deep groove in its substance.

The liver changes its situation with the ascent and descent of the Position is
diaphragm in respiration ; for in inspiration it descends, and in dia^phragm^
expiration it regains its former level, undergoing a sort of tilting a»<i i>y
downwards as it rests on the posterior body-wall. In the upright body,
and sitting postures also, it descends lower than in the horizontal

D.A. X

306

DISSECTION OF THE ABDOMEN.

ypleen :
position ;

relations of
surfaces,
phrenic,
gastric,

and renal.

position of the body ; so that when the trunk is erect the anterior
border may be felt below the edge of the ribs, but when the body is
reclined, it is withdrawn within the margin of the thorax.

The SPLEEN (figs. 112 and 113 ; also 122, p. 329) is deeply placed
behind the stomach, at the back of the left hypochondriuni and
the adjoining part of the epigastric region. It lies very obliquely,
the upper end being near the spine, while the lower end reaches
about half-way round the side of the body.

Its outer or phrenic surface is convex and free and rests against the
diaphragm opposite the ninth, tenth, and eleventh ribs. The anterior
or gastric surface is concave and applied to the stomach, to which it
is attached by the gastro-splenic omentum (fig. 115, gs om, p. 310) ;
the tail of the pancreas also touches the lower end of this surface.
A third narrow surface, the internal or renal, lies against the outer
border of the left kid^ey in its upper half ; and a fold of peritoneum,

OR BORDe»<

Fig. 113. — The Spleen, seen from the Right.

Examine

renal

surface.

Kidneys :
situation ;

surface
markinc

called the lieno-renal ligament (fig. 115,. Zr), which contains the
splenic vessels, passes between the two. The way to find this surface
in the present stage of dissection is to pass the hand backwards
within the concavity of the diaphragm on the left side, the back of
the hand outwards, past the phrenic surface of the spleen, so that the
fingers will hook round its posterior border and enter the recess
between the spleen and the kidney. The upper end of the spleen is
close to the suprarenal capsule ; the lower end rests on the splenic
flexure of the colon and the phrenico-colic ligament.

The KIDNEYS (fig. 112) cannot be seen much at present. The
lower part of the left kidney will be exposed by drawing the small
intestines inwards from the descending colon, and the lower part of
the right kidney can be felt below the liver behind the hepatic
flexure of the colon. They may be marked on the surface of the
front of the body in the following manner, renieml)ering that they
are each about four inches in length and two and a half inches in
width (fig. 112). The lateral planes traverse them longitudinally

REFLECTIONS OF PERITONEUM. 307

somewhat nearer their inner than their outer borders, and the
transpyloric plane crosses them transversely, a third of the right
kidney being above this plane and two-thirds below, whilst two-fifths
of the left kidney lie above tiie plane and three- fifths below.

They are situated at the back of the abdomen, opposite the last Position :
dorsal and upper two or three lumbar vertebrae, and occupy parts
of the epigastric, hj^iochondriac, umbilical, and lumbar regions.
Their position is somewhat oblique, the upper end being nearer to
the spine than the lower ; and the surface which is called anterior
looks much outwards.

They lie behind the peritoneum, and are surrounded with fat. relations
They rest upon the diaphragm, the psoas and quadratus lumborum JI^J},™ "
muscles. The upper end supports the suprarenal body ; and at the
inner border the vessels enter, and the duct (ureter) leaves the organ.

The differences on the two sides will be pointed out later on
(pp. 353 et seq).

The relations of the pancreas must be omitted for the present, but Pancreas
they will be found on pp. 329 and 330. ^**^''-

THE PERITONEUM.

This is the largest serous membrane in the body. In the male it Perito-
is a closed sac, like other serous membranes ; but in the female there "^"
is an aperture of communication with the Fallopian tube, and the arrange-
mucous lining of the latter becomes continuous with the serous '"®"*'
membrane. It lines the wall of the abdomen (parietal peritoneum),
and is reflected over the several viscei-a (visceral peritoneum), some
of which it invests completely, except where the vessels enter. The *'""»<^®S'
inner surface is free and smooth ; but the outer is rough, when it is
detached from the parts to which it is naturally adherent. The
membrane as it passes from viscus to viscus, or from the abdominal
wall to viscera, forms processes or folds, to which different names are folds,
given, and which for the most part consist of two layers enclosing
vessels.

The continuity of the sac may be traced both horizontally and
vertically.

Horizontal circuit round the lower part of the abdomen. From the Circle of the
umbilicus the peritoneum may be followed along the abdominal wall opposite
on the left side to the hinder part of the lumbar region, where it "^ ^ '^"***
partly surrounds the descending colon, and thence over the kidney
to the front of the spine. Here it is reflected forwards, covering the
superior mesenteric vessels, passes round the small intestine, and
returns to the spine along the same vessels, thus forming the mesen-
tery. From the spine it is continued in the same way on the right
side, over the kidney, round the colon, and along the wall of the
abdomen to the umbilicus again.

Vertical circuit (fig. 114). Starting at the under-surface of the Circle from
liver, the small omentum (s oni) is found descending: to the small ^

Oin6Ilti£ll

curv'ature of the stomach, where the two layers of which it consists layers,
separate to enclose that organ, one passing in front and the other

X 2

308

DISSECTION OF THE ABDOMEN.

transvei'se
meso-colon

its ascend-
ing layer ;

descending
layer and
mesentery

in pelvis ;

along front
of abdomen,

Small and
large bags

behind. At the great curvature they meet again, and give rise to
the great omentum or epiploon {g om). After descending to the
lower part of the ahdomen, they bend, backwards and ascend to the
transverse colon, which they enclose in the same way as the stomach ;
and they are then continued to the posterior abdominal wall, forming
the transverse meso-colon {mc). (It should at once be pointed out,
lest the student be misled, that the layers of the great omentum in
front of the transverse colon are usually adherent to one another,
and not separated by intervals, as represented in fig. 114, for the
j)urpose of clearness.) Opposite the anterior border of the pancreas
these two layers, which have been followed over the transverse
colon, part company, — the one passing upwards, and the other
downwards.*

The ascending layer is continued upw^ards in front of the pancreas
and diaphragm, and is then reflected on to the posterior surface of the
liver, where it covers the part called the Spigelian lobe, and passes
into the hinder layer of the small omentum. This layer, however,
cannot be traced in the present stage of dissection.

The descending layer immediately passes off along the superior
mesenteric vessels to the small intestine (jejunum and ileum), forming
the mesentery (m).

From the root of the mesentery, this layer descends over the lower
end of the aorta and the promontory of the sacrum to the pelvis,
where it j)artly invests the viscera of that cavity. Thus, it covers
the upper part of the rectum and is reflected forwards therefrom
to the bladder in the male, or the uterus in the female, forming
a pouch between the two ; and after covering the upper part of
the bladder, it passes off at the front and sides to the abdominal
wall, forming the fossae before noticed in the inguinal region
(p. 292).

Lastly, having left the bladder, the membrane is continued
upwards, lining the anterior wall of the abdomen and the under-
surface of the diaphragm, nearly as far as the spine ; there it is
reflected over the upper surface of the liver, and then, turning
round the lower border to the under-surface, it joins the anterior
layer of the small omentum.

In the foregoing account it will be seen that two vertical circles
have been traced, which surround distinct cavities in figure 114.
The portion of the membrane which forms the circle behind the
liver and stomach is known as the small sac of the peritoneum ;
while the part in front of those organs, which is much more extensive,

* In the foetus at an early period the reflected portion of the great omentum
is continued up to the spine ; and while the ascending layer passes upwards
over the pancreas as explained in the text, the posterior or descending layer
surrounds the transverse colon before passing into the mesentery, thus forming
a transverse meso-colon distinct from the great omentum. The front of the
transverse meso-colon then becomes adherent to the opposed part of the
great omentum, so that the two are united in a single process, and the colon
appears to be enclosed between the omental layers. Occasionally traces of
the foetal condition are met with in the adult.

REFLECTIONS OF PERITONEUM.

309

and reaches into the pelvis, constitutes the large sac. The two sacs

are however continuous, and their cavities communicate through

the ajierture termed the foramen of "Winslow, as will be

apparent by tracing the

horizontal circle at a

higher level than before,

viz., immediately above

the pyloric end of the

stomach.

Horizontal circuit at the
level of the foramen of
Winslow (fig. 115, p. 310).
Beginning in front at the
falciform ligament of the
liver (/), the peritoneum
may be followed on the
left side along the ab-
dominal wall and the
diaphragm to the outer
part of the left kidney,
where it is reflected along
the back of the splenic
vessels to the spleen, form-
ing one layer of the lieno-
renal ligament (Zr). Hav-
ing furnished the invest-
ment of the spleen, the
meml>rane passes as the
outer layer of the gastro-
splenic omentum {gs om)
to the stomach, and over
the front of the latter into
the anterior layer of the
small omentum (.§ (/m).
At the right edge of this
it turns round the hepatic
vessels (which are felt as
thick cord-like structures
within the peritoneal fold)
to the back of the small
omentum ; and at the
spot where it passes be-
hind the vessels it bounds
the foramen of Winslow
(?f), the entrance from the greater into the lesser sac. It then forms
in succession the posterior covering of the stomach, the inner layer
of the gastro-splenic omentum and lieno-renal ligament, and, turning
to the right, is continued over the left kidney and the diaphragm to
the inferior vena cava, where it forms the posterior boundary of the

their con-
tinuity.

Fig

IIJ. — Diagram showing the Arrange-
ment OF THE PkRITONEUM IN A MEDIAN

Section of the Abdomen.

omentum ;

I. Liver.
St. Stomach.
c. Transverse colon.
p. Pancreas.

Duodenum, third

part.
i, i. Coils of small

intestine.
Rectum.

hi. Bladder.

s om. Small omentum.

g om. Great omentum.

nic. Transverse meso-
colon.

m. Mesentery.

rv p. Recto - vesical
pouch.

foi-amen of
Winslow
and small

310

DISSECTION OF THE ABDOMEN.

Chief folds
of the
peritoneum.

foramen of Window. Here becoming great sac again, it can l>e
followed over the right kidney to the liver, and round the latter to
the falciform ligament. On the right side of the falciform ligament
the peritoneum simply passes over the liver and diaphragm.

Special Parts of the Peritoneum. A fter tracing the continuity
of the serous sac over the wall and the viscera, the dissector is to
study the chief processes or folds of the membrane in connection
with the alimentary tube and its appendages. The pieces of peri-

FiG. 115. — Diagram of a Horizontal Section op the Abdomen through
THE Twelfth Dorsal Vertebra, to show the Arrangement of the
Peritoneum at the Foramen of Winslow and round the Spleen.

I. Liver.

St. Stomach.

spl. Spleen.

k, k. Kidneys.

ao. Aorta ; farther forwards the
coronary artery is seen, cut twice.

V c. Inferior vena cava.

w. Foramen of Winslow.

s mn. Small omentum, at the right
end of which are, from left to right.

Note.— The portions of the kidneys are represented too large in this
diagram.

the hepatic artery, portal vein, and
bile-duct.

gs om. Gastro-splenic omentum.

Ir. Lieno-renal ligament.

/. Falciform ligament. In front
of the left kidney is the splenic
artery, sending its branches to the
stomach between the layers of the
gastro-splenic omentum.

Gastric
folds :

Gastro-
hepatic

attach-
ments ;

toneum in connection with the viscera of the pelvis will be seen in
the dissection of that cavity.

Folds connected with the stomach. The processes uniting
the stomach to other viscera are named omenta, and are three in
number, viz., the small or gastro-hepatic omentum, the large or
gastro-colic omentum, and the gastro-splenic omentum.

The small omentum (figs. 114 and 115, s om) stretches between the
liver and stomach, and ends towards the right in a free border,
behind which the foramen of Winslow leads into the cavity of the
small sac. It is attached above to the liver along the transverse

THE OMENTA. 311

fissure and the posterior half of tlie longitudinal fissure (fig. 131, so,

p. 346) ; below to the small curvature of the stomach and the first

part of the duodenum. At its left or posterior end it is fixed to the

diaphragm for a short distance, between the liver and the termination

of the oesophagus. The part between the longitudinal fissure of the

liver and the small curvature of the stomach is very thin, and can

be separated into two layers only in the immediate neighbourhood

of the viscera ; but that extending from the transverse fissure to contents.

the duodenum is much thicker, and encloses the hepatic artery,

portal vein, common bile-duct, and nerves and lymphatics of the

liver.

The great omentum (fig. 114, g om) is the largest fold of the peri- Gastro-coiic
toneum, and results from the meeting of the two layei-s which leave o™^"*"™ =
the great curvature of the stomach and the first part of the duodenum, formation ;
The sheet thus formed descends in front of the intestine, extending
farther on the left side than the right, and at the lower part of the
abdomen is doubled backwards to join the transverse colon. The
fold therefore encloses the lower part of a space (cavity of the small cavity ;
sac), which originally extended to its lower border ; but in the adult
the anterior and posterior portions of the omentum are usually
closely adherent, and the small sac seldom exists below the transverse
colon.

Between the layers of the great omentum, especially near the
stomach, are some branches of vessels, minute nerves, and a variable
quantity of fat ; but over the greater pait of their extent the layers fusion of
are inseparably united, and the resulting membrane is very thin, layers-
and in places cribriform.

Dissection. Divide the part of the great omentum below the Cavity of
stomach, and the cavity of the small sac of the omentum will be ^"^^^^ ^^ *
opened, and the hand may be introduced to ascertain its extent. In
front it is bounded by the anterior part of the great omentum, the boundaries
stomach, the small omentum, and the Spigelian lobe (fig. 131, SI) of
the liver. Behind it are the posterior part of the great omentum, the
transverse colon and meso-colon, the pancreas, the left kidney and
suprarenal capsule, and the diaphragm. To the right it extends as and extent,
far as the inner border of the duodenum (second pait), and to the
left as far as the spleen. Between the duodenum and the liver
it opens into the general cavity or large sac by the foramen of
Winslow.

The foramen of JVindoiv is bounded in front by the right portion Boundaries
of the small omentum, containing the hepatic vessels ; below are the of w^™o"-.
same vessels and the first part of the duodenum ; above is the caudate
lobe of the liver ; and behind, the inferior vena cava.

The gastro-splenic omentum (fig. 115, gs om) reaches from the Gastro-
stomach on the left side to the spleen, and is continued below into omentum,
the great omentum. Between its layers are the gastric branches of
the splenic vessels.

Folds on the large intestine. The disposition of the peritoneum Peritoneal
round the several portions of the colon has been explained in giving

312 DISSECTION OF THE ABDOMEN,

large their relations (yjp. 301 et sec/.). The following processes pass between

intestine: .. . - ^ ^ i ^u v. i • i n

the large intestine and the abdominal wall : —

transveree ^ The transverse meso-colon (fig. 114, m c) extends from the anterior

' or lower border of the pancreas to the transverse colon, to the left of

the sjDot where the latter crosses the duodenum, and contains the

middle colic vessels. In the adult it is formed by a continuation of

the layers of the great omentum, but in the foetus it was a separate

mesentery for the bowel,
phrenico- The upper end of the left colon has a distinct fold — phrenico-colic

' or costo-colic, fixing it to the wall of the abdomen. Attached by a

wide end to the diaphragm opposite the tenth and eleventh ribs, it

passes transversely inwards to the colon, and forms the lower boundary

of a hollow in which the spleen rests,
pelvic The pelvic meso-colon is a long process of the serous membrane,

meso-co on , ^jjj,.jj attaches the loop of the intestine to the wall of the pelvis :

it contains the sigmoid and superior hsemorrhoidal vessels,
sometimes In Some bodies the ascending and descending colon are surrounded
iiig^or^^^ ' by peritoneum, which meets behind the gut and forms a fold —
niSo-coion *^^ ascending or descending meso-colon, between the bowel and the
or meso- ' abdominal wall. The caecum may also be provided with a similar

fold (meso-ccecum) attaching it to the right iliac fossa.
Meso- The meso-appendix will be seen by lifting up the ca3cum, and is a

fold attached on the one hand to the vermiform appendix, and on

the other to the adjacent part of the caecum and the lower surface of

the mesentery near the termination of the ileum.
Appendices Small processes of the peritoneum are attached along the tube of

the great intestine, chiefly to the transverse and pelvic colon ; they

are the appendices epiploicce, and contain fat.
Peritoneal FoLDS TO THE SMALL INTESTINE. The small intestine is not
smauTntes- enveloped by the peritoneum after the same manner throughout,
tine. YoT while the jejunum and ileum are attached to the abdominal wall

by one process (mesentery), the duodenum has special relations with

the serous membrane.
Peritoneum Serous covering of the duodenum. The first part of the duodenum

onduode- . , , . t, i n ^ i i •

num. has peritoneal relations like those oi the stomach, but its posterior

or left surface is only covered for a short distance by the serous
membrane. The second part is concealed in front by the converging
layers of the transverse meso-colon. The third part, which crosses
the aorta, is separated from the peritoneum in the middle line
by the superior mesenteric vessels, but is covered in front by the
serous membrane on each side of them. The root of the mesentery
comes off from the front of the fourth part, which is closely invested
by peritoneum on the left side and partly in front.

Mesentery : Fold of the jejunum and ileum. The mesentery supports the rest of
the small intestine, and is stronger than any other piece of the

form serous membrane. Its hinder end is narrow, and is attached along

the front of the spine and great vessels from the left side of the
second lumbar vertebra to the right sacro-iliac articulation (fig. Ill,

attach- p. 303 ; the attachment being shown by a line interrupted with short

ments.

LIGAMENTS OF THE LIVER. 313

cross lines). The other end of the fold is wide, and is connected
with the intestine.

Ligaments of the liver. On the upper surface of the liver is Pentoueai
the suspensory ligament; and along the back there is a wide the liverl^
process which is divided into coronary, and right and left lateral
ligaments.

The suspensoi-y ot falciform ligament extends from before backwards falciform
between the upper convex surface of the liver and the parietes of the ^^sament ;
abdomen. Its lower border is concave, and fixed to the liver ; while
the upper border is convex, and is connected to the abdominal wall
on the right of the linea alba, and to the under-surface of the
diaphragm. In its free anterior border or base is the remains of the
umbilical vein, which is named tlie round ligament of the liver.

The coronary ligament is placed at the back of the right lobe of coi-ouai-y
the liver, and is composed of two layers which are separated l)y an '0^°^*"^ »
interval (fig. 114). The superior layer passes from the liver to the
diaphragm; but the inferior layer (fig. 131, id, p. 346) is reflected
over the front of the kidney and inferior vena cava. This layer
becomes continuous round the Spigelian lobe with the posterior
layer of the small omentum.

The right lateral ligament (fig. 131, rll) is a small fold at the right right lateral
end of the coronary ligament, formed by the meeting of the two '^amen ,
layers for a short distance.

The left lateral ligaraeiit, larger than the foregoing, is a triangular left lateral
fold of peritoneum, with a free edge turned to the left. It is ^'sament ;
attached by its anterior border to the liver above the margin of the
left lobe, and by its posterior border to the diaphragm in front of
the oesophageal opening. At its right end the upper layer is con-
tinued into the left side of the falciform ligament, and the lower
layer into the front of the small omentum.

Folds of the spleen (fig. 115). These are the gastro-splenic Splenic
omentum and the lieno-renal ligament, the formation of which has ^^^^^'
already been explained.

Accessory peritoneal folds and rossiE. Minor peritoneal folds
and fossse should be looked for in the neighbourhood of the duodeno-
jejunal flexure and about the caecum ; also the lower surface of the
pelvic meso-colon should be examined for the mouth of a small pouch
{intersigmoid) that sometimes exists there. Two pouches are often Duodeuai
found in the neighbourhood of the duodeno-jejunal flexure. One, to
the left of the upper part of the flexure, looking downwards, is called
the superior duodenal fossa, and another, along the lelt side of the Superior,
last (fourth) part of the duodenum looking upwards, is called the
inferior duodenal fossa. A para-duodenal fossa is occasionally found inferior,
to the left of the last part of the duodenum on the posterior para,
abdominal wall, being produced by a fold raised by the inferior
mesenteric vein.

E mining up behind the csecum or the beginning of the ascending Retro-colic
colon there is often a retro-colic fold, producing a pouch on one or ^°^^'
both sides of it, more commonly on the inner side. A very constant

314

DISSECTION OF THE ABDOMEN.

Ileo-c*cal
fold and
pouch.

Ileo-colic
fold and
pouch.

fold (ileo-ccecal), mostly containing fat, passes from the lower border
of the last three inches or so of the ileum on to the caecum and
appendix, often producing a deep pouch looking downwards and to
the left.

A small ileo-colic fold, produced by a branch of the ileo-colic artery,
is sometimes seen immediately above the ileo-colic junction, producing
a pouch looking upwards.

Examine
first vessels
to intestine.

Mesenteric
vessels.

Dissection
of superior
mesenteric
vessels,

and nerves.

Superior

mesenteric

artery

coui-ses in
the me-
sentery ;

relations,

and
branches

MESENTERIC VESSELS AND SYMPATHETIC NERVES.

Directions. The mesenteric vessels and nerves, which supply tlie
greater part of the alimentary tube, may be first dissected. After
these have been examined and the relations of the aorta and vena
cava have been learnt, most of the intestine will be taken out for
examination and to give room for the display of the viscera and
vessels in the upper part of the abdomen.

Mesenteric Vessels. The superior and inferior mesenteric
arteries are two large branches of the aorta, which supply the
intestine, except a part of the duodenum and some of the rectum.
Each is accompanied by a vein, and by a plexus of the sympathetic
nerve.

Dissection (fig. 116). For the dissection of the superior
mesenteric vessels and nerves, the transverse colon and the great
omentum are to be lifted up and placed over the margin of the
ribs. The small intestines should be drawn over to the left, and spread
out fanwise, so that the anterior or right layer of the mesentery can
be removed. While tracing the branches of the artery to the small
intestine, corresponding veins and slender offsets of the sympathetic
nerve on the arteries will be met with. Mesenteric glands and
lacteal vessels also come into view at the same time.

The branches from the right side of the vessel to the large intes-
tine are to be next followed under the peritoneum ; and after all
the branches have been cleaned, the trunk of the artery should be
traced back beneath the pancreas. The surrounding plexus of
nerves should also be defined.

The superior mesenteric artery (fig. 116, a) supplies all the
small intestine beyond the duodenum and half the large intestine,
viz., as far as the end of the transverse colon.

Arising from the aorta near the diaphragm, it is directed down-
wards between the layers of the mesentery, forming an arch with
the convexity to the left side, and terminates in offsets to the
end of the small intestine. At first the artery lies beneath the
pancreas and the splenic vein ; and as it descends to the mesentery
it is placed in front of the left renal vein and the duodenum. It is
surrounded by a plexus of nerves, and accompanied by the vein of
the same name.

Branches. The artery furnishes a small offset to the pancreas
and duodenum, intestinal branches to the jejunum and ileum, and
colic branches to the large intestine.

SUPERIOK MESENTERIC ARTERY. 315

a. The inferior pancreatico-duodenal artery [h) is small, and Pancreatico-
iisiially arises in common with the first intestinal branch. It is " ^"* '
directed to the right between the pancreas and duodenum, to both
of which it supplies branches, and anastomoses with the superior
pancreatico- duodenal artery from the hepatic.

h. The intestinal branches [ovih^ jejunum and ileum (/) are twelve Branches k)
or more in number, and pass from the left side of the artery between thle : '"

Fig. 116, — Superior Mesenteric Artery axd its Branches (Tiedemann).

<i. Superior mesenteric. e. Ileo-colic.

h. Inferior pancreatico-duodenal. /. Intestinal branches to the jeju-

e. iliddle colic. num and ileum.

(/. Right, colic.

the layers of the mesentery. About two inches from their origin branches

the branches bifurcate, and the resulting pieces unite with similar ^*'"" *''^^®'''

offsets from the collateral arteries, so as to form a series of arches.

From the convexity of the arches other branches take origin, which

divide and unite as before. This process is repeated three or four

times between the origin and the distribution, but at each branching

the size of the vessels diminishes. From the last set of arches twigs distribution

are sent to the intestine on both aspects of the tube, and anastomose °" ^^® ^**

round it.

316

ArtericH of
large gut.

Ileo-colic
branch runs
to ctecum.

DISSECTION OF THE ABDOMEN.

Right colic
branch sup-
plies ascend-
ing colon.

Middle colic
branch
passes to
transverse
colon ;

number and
arrange-
ment in
arches.

Superior

mesenteric

A'ein.

Mesenteric
glands ;

lymphatics

entering

them.

Meso-colic
glands.

Dissection
of inferior
me.senteric
artery,

and vein :

The branches to the large intestine are three in number, ileo-colic,
right colic, and middle colic arteries. !

c. The ileo-colic artery (e) arises from the right side of the trunk. ^
and divides opposite the caecum into ascending and descending ^
branches. The ascending branch supplies the csecum and the
beginning of the ascending colon, and anastomoses with the right
colic artery ; while the descending branch joins in a loop with the
termination of the mesenteric trunk, and distributes offsets to the
lower end of the ileum. The ascending branch sends an artery
{appendicular) behind the termination of the ileum, which enters
the meso-appendix, and is distributed to the appendix.

d. The right colic artery (d) is frequently conjoined at its origin
with the preceding. Near the ascending colon it divides into
ascending and descending branches, which anastomose with the
ileo-colic artery on the one side, and with the middle colic on the
other.

e. The middle colic branch (c) springs from the upper part of the
artery, and entering between the layers of the transverse meso-
colon, divides into two branches ; the right one anastomoses with the
artery to the ascending colon, and the left with the left colic branch
of the inferior mesenteric artery (fig. 117, c). The intestinal twigs
are united in arches before entering the gut, like those to the small
intestine.

The superior mesenteric vein (fig. 125, i, p. 334) is formed l)y the
union of branches from the intestine corresponding to the offsets of the
artery. The trunk passes beneath the pancreas on the right side of
the artery, and there joins the splenic vein to form the vena portae.
At the lower border of the pancreas it receives the right gastro-
epiploic branch from the stomach.

The MESENTERIC LYMPHATIC GLANDS are numerous between the
layers of the mesentery. An npper group lies by the side of the
artery, and contains the largest glands ; and a lower group, near the
intestine, is lodged in the intervascular spaces. The chyliferous
vessels of the small intestine, and the absorbents of the part of
the large intestine supplied by the superior mesenteric artery, pass
through the mesenteric glands in their course to the thoracic duct.

Along the side of the ascending and the transverse colon are a few
other small lymphatic glands, meso-colic, which receive some absorb-
ents of the large intestine.

Dissection (fig. 117). By drawing the small intestine over to the
right side, the dissector will observe the inferior mesenteric artery
on the front of the aorta, a little above the bifurcation. The peri-
toneum should be removed from its surface, and the branches
should be traced outwards to the remaining half of the large intes-
tine ; a part of the artery enters the pelvis, but this will be dis-
sected afterwards. On the arter}' and its branches the inferior
mesenteric plexus of nerves ramifies, and should be preserved,
especially near the origin of the vessel.

The inferior mesenteric vein also is to be followed upwards

INFERIOR MESENTERIO ARTERY.

beneath the pancreas to its junction with the superior mesenteric or
the splenic vein.

On the aorta tlie dissector will meet with a plexus of nerves, aortic
which is to be left uninjured. plexus.

The INFERIOR MESENTERIC ARTERY (fig. 117, 6) SUpplles branches Inferior

to the large intestine beyond the transverse colon, and communi- ^J^^^"*^

Fig. 117.~Thk Inferior Mesenteric Artery, and the Aorta, as seen

BY TURNING ASIDE THE UpPER MESENTERIC ArTERY AND THE SmALL

Intestine (Tiedemann).

/. Superior mesenteric.

g. Renal.

h. Spermatic of the left side.

a. Aorta.

h. Inferior mesenteric artery.
c. Left colic, d. Sigmoid, and e.
Superior hsemorrhoidal branches.

eating with the superior mesenteric, continues the chain of anasto-
moses along the intestinal tube.

This vessel is of smaller size than the superior mesenteric, and
arises from the aorta from one to two inches above the bifurcation.
It descends, lying at first on, and then close to the left side of the
aorta, and, after giving oft' branches to the descending, iliac and
pelvic colon, terminates as the superior hsemorrhoidal artery to the
rectum.

a. The left colic artery (c) passes out in front of the left kidney,
and divides into an ascending and a descending branch for the

origm,

and
branches.

Left colic
branch to
descending
colon.

318

Sigmoid
branch
to sigmoid
flexure.

Branch to
rectum.

Inferior
mesenteric
vein :

origin,
course, and

termination.

No valves
in veins.

Lymphatic
glands.

Plexuses of
the sympa-
thetic to the
viscera.

Dissection
of

aortic
plexus, and

hypogastric
plexus.

Superior

mesenteric

plexus

is on artery
of same
name:

secondary
plexuses.

DISSECTION OF THP] ABDOMEN.

supply of the descending colon : by the ascending offset it anasto- '
moses with the middle colic branch of the superior mesenteric.

b. The sigmoid artery (or commonly arteries) (d) is distributed to
the iliac and pelvic colon (sigmoid flexure), and divides into offsets
which anastomose above with the preceding colic, and below with the
haemorrhoidal branch. Here, as in the rest of the intestinal tube,
arches are formed by the arteries before they reach the intestine.

c. The sui^erior hemorrhoidal artery {e) crosses over the left
common iliac vessels, and enters between the layers of the pelvic
meso-colon, to be distributed to the lower end of the large intestine,
its branches reaching in the mucous membrane of the rectum as far
as the anus : it will be described in the dissection of the pelvis.

The inferior mesenteric vein (tig. 125, d, p. 334) begins in the part of
the large intestine to which its companion artery is distributed, and
ascends over the psoas muscle higher than the origin of the artery.
Passing beneath the pancreas, the vein inclines to the right, and
opens into the superior mesenteric trunk at its junction with the
splenic, or sometimes into the splenic vein.

Both mesenteric veins are without valves, and may be injected
from the trunk to the branches, like an artery.

Lymphatic glands are ranged along the descending colon and the
sigmoid flexure. The absorbents of the intestine, after passing
through these glands, enter the left lumbar lymphatic glands.

Sympathetic Nerve. The following plexuses of the sympathetic
on the vessels, viz., superior mesenteric, aortic, spermatic, and in-
ferior mesenteric, are derived from the solar plexus beneath the
stomach, and can now be exposed. The remaining portion of the
sympathetic nerve in the abdomen will be subsequently referred
to (pp. 336 et seq.).

Dissection. On the two mesenteric arteries the dissector will have
already made out the plexuses of nerves distributed to the intes-
tinal tube beyond the duodenum.

He has now to trace on the aorta the connecting nerves between
the mesenteric plexuses, by taking away the peritoneum from the
front of the aorta below the pancreas. From the upper part of the
aortic plexus an offset is to be followed along the spermatic artery ; this
may be done on the left side, where that vessel is partly laid bare.

By detaching the peritoneum below the bifurcation of the aorta,
and following downwards over the iliac arteries the nerves from the
aortic plexus and the lumbar ganglia, the dissector will arrive at the
hypogastric plexus, above the promontory of the sacrum.

The superior mesenteric plexus is a large bundle of nerves, and is
distributed to the same extent of the intestinal tube as the mesenteric
artery. The nerves surround closely the trunk and larger branches
of the artery ; but near thi intestine some of them leave the vessels,
and divide and communicate before entering the gut. The offsets
of the main plexus are named after the arteries which they accom-
pany, viz., intestinal nerves to the small intestine, and ileo-colic,
right colic, and middle colic plexuses to the large intestine.

VISCERAL PLEXUSES OF SYMPATHETIC. 319

The aortic plexiis is an open network of nerves covering the aorta Aortic
below the superior mesenteric artery ; it is stronger on the sides ^ ^^^^'
than on the front of the aorta, in consequence of its receiving acces-
sor}- branches from the lumbar ganglia, especially the left. Above,
the plexus derives an offset, on each side of the aorta, from the solar
and renal plexuses. It ends below, on each side, in branches which offsets,
cross the common iliac artery, and enter the hypogastric plexus.
From it offsets are furnished to the spermatic and inferior mesenteric
arteries.

The spermatic plexus^ formed by roots from both the aortic and the Spermatic
renal plexus, runs on the spermatic artery to the testicle ; in the cord ^^ ^^^^^'
it joins other filaments on the vas deferens.

In the female, the nerves on the ovarian (spermatic) artery are in female,
furnished to the ovary and the uterus.

The inferior mesenteric plexus supplies the part of the intestinal inferior
tube to which its artery is distributed. This plexus is furnished pi^^ust"*'
from the left side of the aortic plexus ; and the nerves composing
it are whiter and larger than in either of the preceding plexuses of
the sympathetic. Near the colon the branching of the nerves and nerves join
the union of contiguous twigs are well marked. Its offsets (plexuses) yes^seis^-
are left colic, sigmoid, and superior hsemorrhoidal : they ramify on secondary

.,,,., 1. ., . plexuses.

those arteries, and have a like distribution.

The hypogastric plexus, or the large prevertebral centre for the Hypogastric
upply of sympathetic nerves to the viscera of the pelvis, is situate P^^""-
in front (-f the last lumbar vertebra. It is formed by the union of situation ;
the prolongations of the aortic plexus ; and the nerves composing it formation ;
are of large size, and interlace in a dense flattened mass, without any
interspersed ganglia. Below, the plexus divides into two portions, and ending,
right and left, which are continued downwards on the inner side of
internal iliac vessels to the pelvic plexuses.

RELATIONS OF AORTA AND VENA CAVA.

Before any of the viscera are removed from the body, the relations
of the abdominal aorta and vena cava may be learnt.

Dissection. To see the aorta above the origin of the superior Dissection
mesenteric artery, it will be necessary to detach the great omentum ° ^° '
from the stomach, without injuring the gastro-epiploic arteries along
the great curvature ; and after raising the stomach, to remove the
peritoneum from the gastric surface of the pancreas, A short arterial
trunk (cadiac axis) above the pancreas is not to be quite cleaned now,
otherwise the nerves about it would be destroyed.

The vena cava on the right side of the aorta may be followed up and a ena
as far as the liver, where it disappears, by separating the transverse
colon from the duodenum and by carefully lifting up the outer part
of the duodenum ; where the latter lies over the inner part of the
right kidney, the confluence of the renal vein and the inferior vena
cava will be exposed. Care must be taken however not to injure the
duodenum and the adjacent head of the pancreas. The relations of

320

Aorta lies
on fi'ont of
spine :

parts
around.

Vena cava
inferior :

extent ;

relations;

is by the
side of the
aorta.

except
above.

Arteries
crossing it,

and vein.

DISSECTION OF TRK ABDOMEN.

its upper end of the vein can be better observed after tlie dissection
of the vessels of the liver.

The AORTA (tig. 138, p. 363) enters the abdomen between the
pillars of the diaphragm, and finally divides into the common iliac
arteries opposite the fourth lumbar vertebra. At its beginning
the vessel lies somewhat to the left of the middle line ; and it
commonly inclines slightly inwards as it descends.

In the abdomen the aorta is covered at first by the pancreas, then
by the third part of the duodenum, and for a short distance below
that by the peritoneum. Beneath the pancreas it is crossed by the
splenic vein above the superior mesenteric artery, and by the left
renal vein below that vessel ; and the solar and aortic plexuses of
the sympathetic lie along its anterior surface throughout. It rests
on the lumbar vertebrae, with the pillars of the diaphragm embracing
it at the beginning. To its right side is the vena cava. Its relation
to other deep parts cannot be examined at present.

The INFERIOR VENA CAVA begins opposite the fifth lumbar
vertebrae by the union of the common iliac veins, and reaches thence
to the heart.

The venous trunk is placed on the front of the vertebral column,
to the right of the aorta (fig. 138). It lies close to the aorta, and is
concealed by the duodenum and pancreas as high as the crus of the
diaphragm ; but above that spot it is inclined away from the artery,
and ascending in front of the diaphragm, is embedded in the back of
the liver for about an inch and a half. Lastly, it leaves the abdomen
by an aperture in the tendinous centre of the diaphragm, on the
right of, and higher than the aortic opening.

Its relations with vessels are not the same as those of the aorta.
Beneath it are the right lumbar, renal, capsular, and diaphragmatic
arteries ; and crossing over it below the kidney is the right spermatic
artery. Superficial to it beneath the pancreas is the beginning of the
portal vein.

REMOVAL OF THE INTESTINES,

Dissection. The jejunum, the ileum, and the whole of the large
intestine, as far as the lower part of the pelvic colon, are now to
be removed. Place two ligatures on the jejunum, one at the duodeno-
jejunal flexure and another an inch further on, and divide the
bowel between them. In the same way divide the lower part of the
pelvic colon between a double ligature. The whole of the intestine
between these points is then removed by cutting through its
peritoneal attachment close to the bowel wall. Care should be
taken not to cut into the bowel, and in removing the transverse
colon the arteries of the stomach must be avoided.

After removal, ligature the ileum about six inches from the ileo-
colic junction and divide it above the ligature. Proceed then in the
following manner : —

1. Cut oft" the upper four inches of the jejunum and the lower four
inches of the ileum above the cut, and put them aside in a tray in water.

REMOVAL OF THE INTESTINES. 321

2. Cut off the next twelve inches of the jejunum ; wash it through
with running water from the tap, inflate it with air, and hang it up
to dry.

3. Cut through the ascending colon about six inches above the
ileo-colic junction. Wash through the detached portion, consisting
of the lower part of the ileum, the caecum, and a piece of the
ascending colon, inflate it, and hang it up to dry.

4. Remove the pieces of mesentery left on the remaining long piece
of the small intestine. Wash the intestine through from end to end
by putting one end on the tap and allowing the water to run
through freely ; and, finally, treat the remainder of the large intestine
in the same way.

SMALL INTESTINE.

The JEJUNUM and the ileum together mea.sure about twenty feet Jejunum
in length, and are connected with the mesentery. There is not any
perceptible difference between the termination of the one and the
beginning of the other, but two-fifths of the length are assigned to
the jejunum, and three-fifths to the ileum. Between the upper and
lower extremities, however, a marked difference may be perceived.
The upper part of the jejunum^is thicker and more vascular than Characters,
the lower end of the ileum ; it is spongy to the feel, owing to its
voluminous mucous membrane, and markedly differs from the thin-
walled ileum ; the width of the upper part of the jejunum is also
greater.

Structure. In the small intestine the wall is formed by the structure
same number of layers as in the stomach, viz., serous, muscular,
fibrous, and mucous.

Dissection. Open the small pieces of jejunum and ileum by
cutting along the mesenteric attachment ; pin them out on cork with
the mucous membrane uppermost. Wash them gently with water,
and remove all contained matter and adhering mucus, and examine
the villi with a hand lens.

Villi. The mucous membrane will be seen to be thickly studded The \dUi.
with small projections, like those on velvet. These bodies exist Their shape,
along the whole of the small intestine, and are irregular in form ^^^^'
(fig. 118), some being triangular, others conical or cylindrical with a
large end. Their length is from ^^th to ^j^th of an inch ; and they
are best marked where the valvulse conniventes are largest. In the
duodenum their number is estimated at 50 to 90 in a square line, and number,
but in the lower end of the ileum at only 40 to 70 on the same
surface (Krause).

Dissection. Now turn the pieces of intestine and pin them out
on the cork with the serous coat outermost.

The serous covering is to be torn off for a short distance, to show
the muscular coat, but in doing this the external longitudinal fibres
will be taken away unless great care is observed.

The seroits coat is closely connected with the subjacent muscular Serous coat
layer. To the jejunum and ileum it furnishes a covering, except

D.A. Y

322

DISSECTION OF THE ABDOMEN.

at the attached side where the vessels enter : at this spot the peri-
toneum is reflected off to form the mesentery, and a space exists
between the serous layers like that at the borders of the stomach.

The muscular coat is constructed of two sets of fibres, a superficial,
longitudinal, and a deep, circular. The fibres are pale in colour, and
are not striated.

longitudinal The longitudinal fibres form a thin covering, which is most marked
at the free border of the gut.

The circular fibres are much more distinct than the others, and
cive the chief strength to the muscular coat. These circular fibres
are best exposed by again turning the specimen and stripping off the
mucous membrane and the subjacent submucous tissue in one piece.

Dissection. The long length of small intestine should now be
opened to show the mucous coat, but the gut should be cut along the

nearly-
complete

Muscular
coat is
formed by a

and a cir-
cular layer.

Show mu-
cous coat.

Fig. 118. — A. A Piece op Mucous
Membrane enlarged, with its Villi
AND Tubules. Part of a Peyer's
Patch is also represented with
THE Follicles (a), each having a
Ring op Tubes at the Circum-
ference.

B. A "Solitary Gland "
OF the Small Intes-
tine, also enlarged,

COVERED BY YlLLI

(Boehm).

Mucous
coat :

thickness ;

folds ;

villous
surface,

and glands.

Valvulae
conni-
ventes ;

form :

size and
depth ;

how formed;

line of attachment of the mesentery, so as to avoid Peyer's glands on
the opposite side.

Mucous coat. The lining membrane is thicker and more vascular
at the beginning than at the ending of the small intestine. It is
marked by numerous prominent folds (valvulae conniventes) ; and
the surface of the membrane is covered with small processes (villi)
like the pile of velvet. Occupying the substance of the mucous
coat are numerous glands.

The valvuke conniventes are permanent ridges of the mucous
membrane, which are arranged circularly in the intestine and
project into the cavity of the tube. Crescentic in form, they
extend round the intestine for half or two-thirds of its circum-
ference, and some end in bifurcated extremities. Larger and
smaller folds are met with, sometimes alternating ; and the larger
are about two inches long, and one-third of an inch in depth
towards the centre. Each is formed of a doubling of the mucous
membrane, which encloses a prolongation of the submucous coat,
with vessels between the layers.

STRUCTURE OF SMALL INTESTINE.

323

Simple

They begin, as will be seen, in the duodenum, about one or two extent on
inches beyond the pylorus, and are continued in regular succession ^\^^ ^^^"
to the middle of the jejunum ; but beyond that point they become
smaller and more distant from one another, and finally disappear
about the middle of the ileum, having previously become irregular
and rudimentary. The folds are largest and most uniform beyond, and
not far from the opening of the bile-duct. By inspection of the dried
portion of the jejunum the disposition of these folds is readily seen.
Glands. In the glandular apparatus of the small intestine are
included the crypts of Lieberkiihn, solitary glands, and Peyer's
and Brunner's glands, the last-named
occurring only in the duodenum.

The cnjpts of Lieherkuhn are minute
simple tubes, which exist throughout the
small intestine. They open on the sur-
face of the mucous membrane by small
orifices between the villi, and around
the larger glands ; but they are not to
be recognised with the naked eye.

The so-called solitary glands (fig. 118, b)
are roundish white eminences, about the
size of mustard-seed if distended, which
are scattered along the small intestine,
but in greatest number in the ileum.
Placed on all parts of the intestine, and
even on or between the valvulae conni-
ventes, they are covered by the \illi of
the mucous membrane, and are sur-
rounded at their circumference by aper-
tures of the crypts of Lieberkiihn. These
small bodies are nodules of lymphoid
tissue.

The agminated glands or glands of
Peyer (fig. 119) exist chiefly in the
ileum, and, beginning at the lower end, they should be looked
for by holding the bowel up against the light. They form oval
patches, measuring from half an inch to two inches or more in size ;
length, and about half an inch in width. They are situate on the situation
part of the intestine opposite to the attachment of the mesentery,
and their direction is longitudinal in the gut : usuallv thev are from
twenty to thirty in number. In the lower part of the ileum they number ;
are largest and most numerous ; but they decrease in number and pecuiian-
size upwards from that spot, till at the lower end of the jejunum ^^^'
they become irregular in form, and may consist only of small
roundish masses. The patches are most distinct in young persons,
and generally disappear in old age.

The mucous membrane over the glands is hollowed into pits
(fig. 119, 6), and is generally destitute of villi (fig. 118, a) ; but
between the pits it has the same characters as in other parts.

y 2

Fig. 119. — Peykr's Patch,
four times enlarged
(Kolliker).

a. Surface of mucous mem- ti(mf^^'
brane covered with villi.

b. Pits over the follicles

where villi are absent. Patches of

Peyer :

324

DISSECTION OF THE ABDOMEN.

composi-
tion.

Arteries of
the intes-
tine ;

These patches are simply collections of lymphoid nodules of the
same nature as the " solitary glands."

Vessels of the intestine. The arteries are derived from the intestinal
branches of the superior mesenteric trunk, and enter the wall of the
intestine at the attached border. They run at first beneath the
serous coat, round the side of the bowel, and give off numerous
ramifications, which anastomose freely together, and perforate the
muscular coat, supplying branches to its substance. Finally, they
break up into very minute twigs in the submucous layer, before
entering the mucous coat. The vei7is have their usual resemblance
to the companion arteries.

The absorbents (lacteals) leave the intestine with the vessels and
pass to the mesenteric glands,
and nerves. Nerves of the Small intestine come from the upper mesenteric
plexus, and entering the coats by the side of the arteries, form
plexuses with interspersed ganglia.

absorbents

Extent of
the gut ;

length ;
size.

Compared
with small
gut, larger,

more fixed,

not coiled,

sacculated
with bands.

Append-

Definition of
caecum ;

length and
width ;

receives
ileum and
appendix.

Vermiform
appendix :

attach-
ment ;

dimensions
it is hollow.

LARGE INTESTINE.

The large intestine is the part of the alimentary canal between the
termination of the ileum and the anus.

In length it measures about five or six feet, — one-fifth of the length
of the intestinal tube. The diameter of the colon is largest at the
commencement of the csecum, and gradually decreases as far as the
upper part of the rectum : in the lower part of the rectum there is a
dilatation above the anal canal.

When compared with the small intestine, the colon is distinguished
by the following characters : — It is generally of greater capacity,
being in some places as large again, and is more fixed in its position.
Instead of being a smooth cylindrical tube, the colon is sacculated,
and is marked by three longitudinal muscular bands, which alternate
with as many rows of dilatations. Its wall is thicker and attached to
the surface, especially along the transverse and pelvic colon, are small
processes of peritoneum containing fat — the appendices epiploicse.

The inflated portion of the large intestine, containing the ileo-colic
junction, will now be examined.

The c^cuM, or the head of the colon (fig. 120, a), is the rounded
end of the large intestine, which projects, in the form of a pouch,
below the entrance of the ileum. It measures about two inches
and a half in length, and rather more in width, though gradually
narrowing below : it is the widest part of the colon. At its inner
side it is joined by the small intestine (6) ; and still lower there is a
small worm-like projection (c) — the vermiform appendix.

Appendix vermiformis (fig- 120, c). This little convoluted tube is
attached to the lower and hinder part of the caecum, of which it was
a continuation at one period in the embryo. From three to six
inches in length, the appendix is rather larger than a goose-quill,
and is connected to the inner side of the caecum and to the lower face
of the mesentery of the ileum by the meso-appendix. Its interior

THE ILEO-COLIC JUNCTION.

325

has an aperture of communication with the intestine (d). In struc-
ture it resembles the rest of the colon, except that the longitudinal
muscular bands coalesce upon it. Its mucous membrane contains a
great amount of adenoid tissue.

Dissection. To examine the interior of the dried specimen of
the caecum, and the valve between it and the small intestine, the
following cuts should be made in
it : — One oval piece is to be taken
from the upper aspect of the ileum
near its termination ; and another
from the side of the caecum, opposite
the entrance of the small intestine.

Ileo-colic valve {^g. 120). This valve
is situate at the entrance of the ileum
into the large bowel. It is composed
of two pieces, which project into the
interior of the colon and bound a
narrow, nearly transverse, aperture of
communication between the two parts
of the intestinal canal.

The upper piece of the valve, ileo-
colic (e), projects horizontally into the
large intestine, opposite the junction
of the ileum with the colon. And
the lower piece, ileo-ccecal {f), which
is the larger of the two, has a nearly
vertical direction between the ileum
and the caicum. At each extremity
of the opening the pieces of the valve
are blended together ; and the re-
sulting prominence {g) extends trans-
versely on the front and back of the
intestine, forming the frcena or reti-
nacida of the valve.

The size of the opening is altered
by the distension of the intestine ;
for when the retinacula of the valve
are stretched the folds bounding the
aperture are approximated, and may
be made to touch.

Each piece of the valve is formed
by circular muscular fibres of the

intestinal tube, covered by mucous membrane and submucous tissue ;
and the ileum projects into the interior of the caecum as if it
were thrust obliquely through the wall of the caecum, after being
deprived of its peritoneal coat and the layer of longitudinal fibres.
This construction is easily seen on a fresh specimen by dividing the
peritoneum and the longitudinal fibres, and gently drawing out the
ileum from the caecum.

the other
leo-csecal :

these are
joined at
the ends.

120. — Interior of the
c^cum, dried and laid

OPEN.

a. Caecum.

b. Small intestine.

c. Vermiform appendix, and
d, its aperture.

e. Ileo-colic piece of the valve
at the junction of the small
intestine.

/. lleo-csecal piece of the
valve.

g. Retinaculum of the valve
on each side.

and form
frsena.

Opening in
the valve.

The valve a
prolonga-
tion of the
wall of the
gut.

326 DISSECTION OF THE ABDOMEN.

Appendix The opening of the appendix into the csecum {d) is placed below
c£cum"*° that of the ileum. The mucous membrane partly closes the aperture

and acts as a valve.
Ridges in Folds or ridges are directed transversely in the interior of the gut,

the caecum; ^^^ correspond with depressions on the outer surface: these folds
how formed, result from the doubling of the wall of the intestine, and the
largest enclose vessels.

Dissection. Portions of the transverse colon and the pelvic colon

should be examined to show the disposition of their coats, in the same

way as the pieces of small intestine, after the whole piece of large

intestine has been slit oj^en and washed clean.

Four strata STRUCTURE OF THE COLON. The coats of the large are similar

of the S^ to those of the small intestine, viz., serous, muscular, fibrous, and

mucous.
Serous coat Serous coat. The peritoneum does not clothe the large intestine,
th?intS"^ throughout, in the same degree. It usually surrounds the csecura,
ti"e- but covers only the front and sides of the ascending and descending

colon (p. 302). The transverse colon is encased like the stomach,
and has intervals along the borders, where the transverse meso-colon
and the great omentum are attached.
Two layers The muscular coat is formed of longitudinal and circular fibres,
fibmff ^ as in the small intestine.

longitudinal The longitudirial fibres may be traced as a thin layer over the

bands^^ Surface, but most are collected into three longitudinal bands, about

posterior, a third of an inch in width. One of these bands is placed along

internal'; tihe posterior or attached margin of the bowel, the other two are on

the anterior and inner sides respectively. On the vermiform

appendix the fibres form a uniform layer, but they are continued

thence into the bands on the caecum and colon, and on the rectum

the anterior and internal bands become united. When the bands

are divided the intestine elongates, — the sacculi and the ridges in the

interior of the gut disappearing at the same time.

and circular. The circular fibres are spread over the whole surface, but are most

marked in the folds projecting into the intestine. At the end of

the rectum (to be afterwards seen) they form the band of the internal

sphincter muscle.

Submucous The flbrous or submucous coat resembles that of the small intestine.

coat asm t -ii i i i • i • i i i

small gut. it Will be exposed by removing the peritoneal and muscular

coverings.
Mucous coat The mucous coat, which may be examined on opening the intestine,

IS without . - 1 ,. , n, , , .^ . ^ ^ .

folds IS smooth, and oi a pale yellow colour ; and it is not thrown into

and villi. special folds. The surface is free from villi ; and by this circum-
stance the mucous membrane of the large can be distinguished from
that of the small intestine. This difference in the two portions of
the alimentary tube is well marked on the ileo-colic valve ; for the
surface looking to the ileum is studded with villi, while the surface
continuous with the mucous lining of the large intestine is free from
those eminences,
glands, Glands. The mucous membrane is thickly beset with very small

THE DUODENUM. 327

tubular glands or crypts of Lieberkhiln, like those of the small intes-
tine ; and lymphoid nodules (solitary glands) are scattered over the and
whole of the large intestine, but are most abundant in the caecum iJSaies!
and vermiform appendix.

Vessels and nerves. The distribution of the vessels and nerves in Vessels,
the wall of the large intestine is the same as in the small. and lym-

The absoi'hent vessels, after leaving the gut, join the lymphatic P^^'^s.
glands along the side of the colon.

RELATIONS OF THE DUODENUM AND PANCREAS.

Dissection. The student should moderately inflate the stomach Remove
and duodenum from the cut extremity of the latter, and remove the |^ see "he
loose peritoneum and the fat: while cleaning them, he should lay duodenum,
bare the larger vessels and nerves. ,

The stomach should be turned upwards, and the pancreas traced and pan-
from the spleen on the one side to the duodenum on the other .^ ', ^

wiLn QllCii

(fig. 122, p. 329), and the parts behind the stomach cleaned of their
fat and peritoneum, care being taken not to injure the vessels and
nerves. By pulling forwards the duodenum, the common bile-duct
may be found behind, between the intestine and the head of the
pancreas ; and some of the pancreas will afterwards be removed, to
show its duct entering the duodenum.

Duodenum (figs. 121 and 122). The first part of the small intes- Duodenum:
tine, or the duodenum, begins at the pyloric end of the stomach, and extent;
crossing the spinal column, ends at the duodeno-jejunal flexure on
the left side of the second lumbar vertebra. It makes a curve round course and
the head of the pancreas, and is placed mainly in the right epigastric
and umbilical regions of the abdomen. From its winding course
round the pancreas it is divided into four portions (tig. 121, i, 2, ^, division,
and **). It may be roughly marked on the surface of the body by a Surface
parallelogram formed by the middle line internally, the right °^ai"ki"g
lateral line externally, the transpyloric line above and a line mid-
way between the transpyloric and intertubercular lines below ; it
being remembered, of course, that the duodenum begins to the right
of the middle line.

The first portion is directed backwards and a little upwards, and First part is
is free and movable like the stomach. It measures about two inches and^^?^'
in length, and is directed backwards from the pylorus to near the "lovable.
upper end of the right kidney. Above and in front are the liver
and gall-bladder ; below is the head of the pancreas ; and behind it
are the common bile-duct, the portal vein, and the gastro-duodenal
artery with a portion of the head of the pancreas (fig. 123, p. 331).

The second or descending portion, about three inches in length, second part
descends in a groove along the right border of the head of the and^gxed^
pancreas to the level of the third lumbar vertebra, and is fixed
almost immovably by the peritoneum and the pancreas. In front of
it are the liver and transverse colon ; behind it are the inner border
of the kidney, the ureter, and the renal vessels ; and on its inner side

328

DISSECTION OF THE ABDOMEN.

the head, of the pancreas, with the common bile-duct. The ducts
of the liver and pancreas open into this f)art of the duodenum.
Third part is The third portion is nearly horizontal ; it crosses from right to left
a°so fixecL^ opposite the third lumbar vertebra, in front of the vena cava and
aorta. Its anterior surface is crossed from above downwards l)y the
superior mesenteric vessels, and above it is the pancreas.

T\\& fourth portion ascends on the surface of the left psoas muscle

Mid line

I nCer-bubercul ar
plane. ^

Fig. 121. — Diagram showing the Disposition of the Deep Organs in
THE Regions of the Abdomen (C.A.).

1, 2, 3 and 4 denote the four parts of the duodenum.

Fourth part along the left side of the aorta to the inferior surface of the pancreas,
where it becomes free at the duodeno-jejunal flexure.

The DUODENO-JEJUNAL FLEXURE reaches up to the transpyloric
plane a little to the left of the middle line. It is firmly held up to
the inferior surface of the pancreas by a strong band of fibres — the
susjjensory ligament (Lockwood) — which passes upwards behind the
pancreas. In the child this band consists largely of unstriped
muscle fibres, and is readily defined. It passes upwards to the
left of the coeliac axis, and blends with the diaphragm to the
right of the oesophageal opening.

ascends.

Suspensory
ligament.

THE PANCREAS.

329

The peritoneal relations of the duodenum have been noticed at
p. 301.

Pancreas (fi^^. 122 and fig. 123, p. 331). The pancreas is situate Pancreas:
behind tlie stomach, extending from the duodenum to the spleen, ^ndfom ;
and occupying parts of the right umbilical, the epigastric, and the
left hypochondriac regions. In form it is elongated, with its right
portion much expanded from above down, constituting the head ;
this part lies in front of the first and second lumbar vertebrae, the
great vessels and muscles intervening.

The gland has a massive head embraced by the duodenum, a neck or head,

Anterior border of pancreas.
Spleen.

Ascending colon. Superior mesenteric vessels.

Descending
colon.

Lower part of the splenic
flexure of the colon.

FiG. 122. — Deep Viscera of the Abdomen of a Child.
(From a si)ecimen in the Charing Cross Hospital Museum.)

slight constriction near the middle line, usually above the conver-
gence of the mesenteric vessels, and a hodij extending across to the body
left as far as the spleen. The left extremity of the body is commonly
spoken of as the tail, but the gland is often not at all tapering in tail.
this part.

The BODY has usually somewhat of a twist upon it as it passes to Surfaces:
the left (fig. 123) ; and it presents an anterior or gastric surface, an
inferior or jejunal surface, and a posterior. These surfaces are
separated by upper, anterior, and lower borders.

The transverse meso-colon springs from its anterior border ; the
upper layer of the peritoneum passes upwards over the gastric
surface, and the lower layer is directed backwards across the inferior
surface.

330 DISSECTION OF THE ABDOMEN.

anterior Its anterior surface is for the most part concave, corresponding to

surface, ^j-^^ stomach ; but at its upper border, in front of the vertebral
column, it forms a projection (omental tiiherosity, His) opposite the
small curvature and lesser omentum.

inferior, Its inferior surface is in contact with the duodeno-jejunal flexure

and coils of the jejunum, as well as sometimes at its left extremity
with the splenic flexure of the colon.

posterior. Its posterior surface rests on the vena cava, the termination of the

right renal vein, the aorta, the solar plexus, the jjillars of the
diaphragm, the left kidney, and the lower part of the left suprarenal
body with the renal and suprarenal vessels. The splenic vein and
the beginning of the vena portae lie also behind it, and are often
somewhat embedded in its substance.

Relations to Projecting above the pancreas, where it crosses the aorta, is the
coeliac axis, from which the splenic artery runs to the left along the
upper border (fig. 123) ; while on the right side the hepatic artery
and the first part of the duodenum lie above it. At the lower border
is the third part of the duodenum ; and the superior mesenteric
vessels emerge between the two, usually passing in front of a portion
of pancreatic substance {lesser -pancreas) (fig. 122) which extends more
or less over the front of the fourth part of the duodenum, occasionally
even reaching into the root of the niesentery.

The common bile-duct lies between the duodenum and the head of
the pancreas for a short distance l)ehind, and will be traced out later.

THE STOMACH BED (fIG. 122).

With the stomach lifted well up and the parts behind it exposed,

the student will realise the character of the hollow in which it lies

Stomach to the left of the vertebral column. The floor of the stomach bed
bed

(Birmingham) is formed (1) internally by the diaphragm covering the

vertebral column and (2), further outwards and above, by the gastric
surface of the sj)leen. Below this is (3) a portion of the left supra-
renal body resting against the crus of the diaphragm, and, it may be,
(4) a small part of the left kidney above the pancreas (fig. 121).
Below these is (5) the gastric surface of the pancreas, which, in
passing to its prominent anterior border, forms the commencement of
a shelf supporting the stomach below ; and the shelf is completed by
(6) the transverse meso-colon j)assing forwards and downwards from
the anterior border of the pancreas to (7) the transverse colon. This
shelf is itself supported by the small intestines below the transverse
meso-colon.
hf th^^°h*' "^^^^ shape of the body of the pancreas is much determined by the
and position pressure of the stomach above and that of the small intestines below,
pancreas. When the stomach is low and distended the pancreas becomes
flattened out and pushed down on the left kidney. On the contrary,
when the stomach is high up and the small intestines distended,
the pancreas becomes pushed up and its anterior border more
prominent.

CCELIAC ARTERY AND BRANCHES.

331

CCELIAC AXIS AND PORTAL VEIN.

A short branch of the aorta — the coeliac axis — furnishes arteries Arteries of
to the stomach and duodenum, the liver, pancreas, and spleen : it sub- ^^*^®™-
divides into ihiee primary branches— coronary, hepatic, and splenic.

The veins corresponding to the arteries (except the hepatic) are Veins,
collected into one trunk — the vena portse.

Dissection. The vessels have been in part laid bare by the How to dis-
previuus dissection, and in tracing them out fully the student ^s'^^ ^
should spare the nerve-plexuses around them. Supposing the liver and
well raised, he may first follow to the left side the small coronary branches,
artery, and show its branches to the cesophagus and the stomach, coronary,

Portal vein.

Common bile-duct

Hepatic artery.

Coronary artery. Splenic artery.

Gastro-duodenal «
artery.

Anterior border of pancreas.
Inferior mesenteric vein.
Colica media artery.
Superior mesenteric artery.

Superior mesenteric vein.
Colica dextra artery

Fig. 123. — The Pakcreas and the Blood-vessels in Relation with it.
(From a specimen in the Charing Cross Hospital Museum.)

Next, the hepatic artery, with the portal vein and the bile-duct, may hepatic,
be traced to the liver and the gall-bladder ; and a considerable
branch of the artery should be pursued beneath the pylorus to the
stomach, duodenum, and pancreas. Lastly, the splenic artery, which and splenic,
lies along the ujjper border of the pancreas, is to be cleaned ; and its
branches to the pancreas, stomach, and spleen should be defined. In
doing this one student should hold aside the stomach and spleen
whilst the other does the dissection.

The veins will be dissected for the most part with the arteries ; Veins.
but the origin of the portal trunk is to be made out beneath the
pancreas, and in front of the vena cava.

The Coeliac Axis (fig. 124, p. 333) is the first visceral branch Cceiiac axis
of the abdominal aorta, and arises close to the upper margin of the threVfoi-
opening in the diaphragm. It is a short thick trunk, about half an lo^Qg '-—
inch long, which projects above the upper border of the pancreas,

332

DISSECTION OF THE ABDOMEN.

Coronary,
which gives

offsets to
the oeso-
phagus

and the
stomach.

Splenic
artery

supplies the
spleen,

the pancreas
by large and
twigs,

and the
stomach

by vasa
brevia,

and left
gastro-
epiploic.

Hepatic
artery

courses to
the liver,

in which it
ends,

and supplies

offsets to

and is surrounded by the solar plexus of the sympathetic. Its
branches — coronary, hej)atic, and splenic— radiate from the trunk
(whence the name axis) to their distribution to the surrounding
viscera (see also fig. 123).

The CORONARY ARTERY (fig. 124 (I) is the smallest of the three, and
runs upwards between the peritoneum and diaphragm to the cardiac
orifice of the stomach. Having furnished some oesophageal branches,
it bends downwards, and passes between the layers of the small
omentum, along the small curvature of the stomach, to anastomose
with the pyloric branch (o) of the hepatic artery. Its offsets are thus
distributed : —

a. (Esophageal branches ascend on the gullet through the opening
in the diaphragm, and anastomose with branches of the descending
thoracic aorta.

6. Gastric branches a^Te given to both sides of the stomach, and those
on the left end communicate with twigs (vasa brevia) of the splenic
artery.

The SPLENIC ARTERY (e) is the largest branch of the coeliac axis in
the adult. It is a tortuous vessel, and runs almost horizontally to
the spleen along the upper border of the pancreas (fig. 123). Near
the spleen it divider into terminal branches, about seven in number
(from four to ten), which enter that viscus by the surface tow-ards the
stomach. It is accompanied by the splenic vein, which is below it ;
and it distributes branches to the pancreas and the stomach.

a. Pancreatic branches. Numerous siiiall branches are supplied to
the pancreas ; and one of these [arteria pancreatica magna) sometimes
arises near the left end and runs to the right in the gland with the
duct ; but this artery is usually not larger than some others.

b. Gastric branches arise from the artery or its divisions near the
spleen, and pass to the stomach between the layers of the gastro-
splenic omentum. Most of these {vasa brevia) are small, and ramify
over the left end of the organ ; but one larger branch, the left gastro-
epiploic artery (/), turns to the right between the layers of the great
omentum, along the great curvature of the stomach, and inosculates
with the right gastro-t piploic branch of the hepatic artery. This
artery distributes twigs to both surfaces of the stomach, and between
the pieces cf peritoneum forming the great omentum.

The HEPATIC ARTERY {g) is intermediate in size between the other
two, and is encircled by the largest plexus of nerves. In its course
to the liver, the vessel is directed at first to the right and forwards to
the pyloric end of the stomach, where it supplies its gastric branches.
It then ascends between the layers of the small omentum, on the left
side of the bile-duct and portal vein, and divides near the transverse
fissure of the liver into two — the right and left hepatic. Branches
are distributed not only to the liver, but also to the stomach, the
duodenum, and the pancreas, as below : —

a. The gastro-duodenal artery (figs. 123 and 124) is a short vessel
which descends beneath the duodenum near the pylorus, and divides
into the two following branches ; —

CCELIAC ARTERY AND BRANCHES.

333

The right gastro-epiploi'c artery (fig. 124 h) is the continuation of the stomach,
gastro-dnodenal trunk, and runs from right to left along the great
curvature of the stomach. It gives offsets upwards to the surface
of the stomach, and downwards to the great omentum, and ends by
inosculating with the left gastro-epiploic artery.

The siijperior pancreatico-duodenal artery {i) is of small size, and duodenum
descends between the duodenum and pancreas to join the inferior ^ncreas.
pancreatico-duodenal branch of the superior mesenteric. Offsets are
given to both the viscera ; and on their posterior aspect is another

Fig. 124. — A'iew of the Cceliac Axis, and of the Viscera to
WHICH ITS Branches are supplied (Tiedkmann).

A. Liver.

B. Gali-bladder.

C. Stomach.

D. Duodenum.

E. Pancreas.

F. Spleen.

Arteines :
o. Aorta.

b. Upper mesenteric.

c. Cceliac axis.

d. Coronary.
€. Splenic.

/. Left gastro-epiploic.
g. Hepatic.

k. Right gastroepiploic.
i. Superior, and k, inferior
pancreatico-duodenal.
I. Phrenic.
n. Cystic.
0. Pyloric.

small artery of the pancreatico-duodenal, with a similar position and
distribution.

b. The pyloric branch (o) descends to the small cun^ature of the
stomach, and, running from right to left, anastomoses with the
coronary artery ; it distributes small twigs on both surfaces of the
stomach.

The hepatic branches sink into the liver at the transverse fissure,
and ramify in its substance : —

c. The right branch is divided when about to enter the organ, and
supplies the following small artery to the gall-bladder.

The cystic artery (n) bifurcates on reaching the neck of the gall-
bladder, and its two twigs ramify on the upper and lower surfaces.

d. The left branch is smaller than the other, and enters the liver

Branches to
the liver,

one for the
right lobe
and gall-
bladder,

and one for
the left lobe.

334

DISSECTION OF THE ABDOMEN.

Portal
system of
veins.

Coronary
vein.

at the left end of the transverse fissure ; a branch to the Spigelian 1
lobe of the liver arises from this piece of the artery. j

Dissection. The veins forming the portal will now be exposed
by raising up the pancreas from the left, as may be required.

Fig. 125. — Portal Vein and Tributaries (Henle).
a. Trunk of the portal vein. e. Left gastro-epiplo'ic.

h. Upper mesenteric. /. Pyloric (in this case of large

c. Right gastro-epiploic. size).

d. Inferior mesenteric. g. Venae breves.

The splenic vein is not indicated by a letter.

Portal Vein. The veins of the stomach and intestine, and of
the spleen and pancreas, pour their blood into the vena portse.
The two mesenteric veins and their branches have been referred to
(pp. 316 and 318) ; and the three following, with the trunk of the
portal vein, remain to be noticed.

The coronary vein accompanies the artery of the same name along
the small curvature of the stomach, and bending downwards at the
cardia, passes to the lower end of the portal vein or the adjacent
part of the splenic vein.

PORTAL VEIX. 335

The pyloric vein (tig. 125,/) lies with the pyloric branch of the Pyloric
hepatic artery along the lower part of the small curvature of the ^®^°"
stomach, and opens into the portal vein opposite the duodenum.

The splenic vein (tig, 125) is of large size, and is formed by the Splenic
union of branches from the spleen. It runs below the artery, and ^'^*"'
under cover of the pancreas, to the front of the vena cava, where it
joins the superior mesenteric vein (6) to form the vena portae.

Between its origin and termination it receives branches corre- tributaries,
spending with the following arteries, — vasa brevia (^r), left gastro-
epiploic (g), and pancreatic. The inferior mesenteric and coronary
veins {d) sometimes open into it.

The PORTAL VEIN (vena portae, fig. 125, a, also fig. 123) is formed Portal vein :
by the union of the splenic and superior mesenteric veins. Its origin origin ;
is placed behind the head of the pancreas, and in front of the inferior
vena cava. The vessel is about three inches long, and ascends
beneath the first part of the duodenum, and then between the layers course and
of tlie small omentum, to the transverse fissure of the liver, where j^ ^^ * ^ ^^ •
divides into a right and a left branch. While in the small omentum
it lies behind the hepatic artery and bile-duct.

The right branch is shorter and larger than the left, and ramifies branches ;
in the right lobe of the liver.

The left branch gives an offset to the Spigelian lobe, and enters
the left half of the liver.

In its course the portal trunk is joined by the coronary and pyloric and tribu-
veins from the stomach ; and the cystic vein from the gall-bladder *^"®^-
enters the right branch.

This vein commences by tributaries from the viscera of the abdomen. Peculiarities
like any other vein ; but it has no valves, and it ramifies through vein?
the structure of the liver in the same manner as an artery. Its
radicles communicate with the systemic veins on some parts of the
intestinal tube, but more particularly on the rectum.

Dissection. The common bile-duct will now be traced upwards
and downwards, the duodenum being raised up from the right and
thence to the left as required.

Bile-ducts. Tvfo hepatic ducts issue at the transverse fissure of Right and
the liver (fig. 131, p, 346), one from the right and the other from the duct^T*'*^
left lobe, and unite to form the following : —

The common hepatic duct is an inch and a half long, and receives Common
at its termination the duct of the gall-bladder, the union of the two duct,
giving origin to the common bile-duct.

The common bile-duct (fig. 131, bd) is about three inches long. Common
It descends almost vertically beneath the upper portion of the ^^^^'^"^^ -
duodenum ; then passing between the pancreas and the second couree f"
piece of the duodenum, it opens into this portion of the intestine termina-
at the inner side, and about the middle. While in the small ^^°" '
omentum the duct lies to the right of the hepatic artery, and
somewhat before the portal vein.

As it pierces the wall of the intestine it is joined commonly by the joined by
pancreatic duct, but the two may enter the duodenum separately.

336

DISSECTION OF THE ABDOMEN.

SYMPATHETIC AND VAGUS NERVES.

General dis-
position of
nerves.

Two large
centres,

epigastric

and hypo-
gastric.

How to lay

bare solar
plexus,

and the

semilunar

ganglia.

Follow the
ending of
the vagus
nerves.

Solar
plexus :

appearance

and extent :

Sympathetic Nerve. In the abdomen, as in the thorax, the
sympathetic nerve consists of a gangliated cord on each side of the
vertebral column, and of prevertebral centres or plexuses, M^hich
furnish branches to the viscera.

The chief prevertebral plexuses in the abdomen are the epigastric
or solar and the hypogastric. The epigastric plexus is placed
behind the stomach, and supplies nerves to all the viscera above the
cavity of the pelvis : it is continued downwards to the hypogastric
plexus by the aortic plexus (p. 319). The hypogastric plexus dis-
tributes nerves to the pelvic viscera, and has already been noticed
at its commencement (p. 319).

The knotted or gangliated cord will be met with in a subsequent
stage of the dissection ; and only the great solar plexus with its
offsets is to be now examined.

Dissection. To denude the epigastric plexus, the following
dissection is to be made : The air should be let out of the stomach
and duodenum ; the portal vein, the common bile-duct, and the
gastro-duodenal artery are to be cut through near the pylorus ; and
the stomach, duodenum, and pancreas are to be drawn over to the
left side. On raising the liver, the vena cava appears ; this is to
be cut across above the junction of the renal veins with it, and the
lower end is to be drawn down with hooks.

Beneath the vein the dissector will find the large reddish semi-
lunar ganglion of the right side ; and mixed up with the nerves of
the plexus are numerous lymphatic glands (coeliac glands), with a
dense tissue, which require to be removed with care. From its
inner part he can trace the numerous nerves and ganglia around the
coeliac and superior mesenteric arteries, and the secondary plexuses
on the branches of those arteries. From the outer part of the ganglion
offsets are to be followed to the kidney, the suprarenal body, and
the diaphragmatic arteries. At its upper end the junction with the
large splanchnic nerve may be seen ; and deeper than the last, one
or two smaller splanchnic nerves may be found as they issue through
a fissure of the diaphragm, and enter the cceliac, renal and supra-
renal plexuses.

The student should then trace the ending of the pneumo-gastric
nerves on the stomach. The left nerve will be found at the small
curvature in front, near the oesophagus ; and the right nerve will
be seen at a corresponding spot on the opposite aspect. Branches
from the right nerve are to be followed to the plexus of the sympa-
thetic by the side of the coeliac axis ; and from the left, to the
hepatic plexus.

The EPIGASTRIC or solar plexus is a large network of nerves
and ganglia, which lies in front of the aorta and pillars of the
diaphragm, and behind the pancreas and inferior cava : it fills the
space between the suprarenal capsules of opposite sides, and sur-
rounds the coeliac axis and the superior mesenteric artery. The

SYMPATHETIC PLEXUSES. 337

plexus is connected on each side with the lai^e and small splanchnic
nerves ; and it is joined also by a great part of the right pneumo-
gastiic nerve. Large branches are furnished to the different viscera gives offsets

1 , ■■ , on blood-

along the vessels. vessels.

The semilunar ganglia., one in each half of the plexus, are the Semilunar
largest in the body, and are placed close to the suprarenal capsules, "

resting on the diaphragm, the ganglion of the right side being beneath
the vena cava. At the upper end each is joined by the great
splanchnic nerve. Each ganglion is irregular in shape, and is often
divided into smaller ganglia ; from its outer side nerves are directed form,
to the kidney and the suprarenal capsule.

Offsets of the plexus. The nerves supplied to the viscera form Several
plexuses round the vessels ; thus, there are cceliac, mesenteric, renal, the plexus,
spermatic, diaphragmatic plexuses, &c.

The diaphragmatic or phrenic plexus comes from the upper end of Piextis to
the semilunar ganglion, but it soon leaves the phrenic artery to enter phragm
the substance of the diaphragm : a communication takes place
between the phrenic nerve from, the cervical plexus and these
branches of the sympathetic. On the right side is a small ganglion has a
where the plexus is joined by the spinal nerve ; and from it filaments ^i^ side,
are supplied to the vena cava and the suprarenal body : this ganglion
is absent on the left side (Swan).

The suprarenal nerves are very large and numerous, in comparison Suprarenal
with the size of the viscus supplied, and are directed outwards to the
suprarenal body. The lesser splanchnic nerve directly communicates
^vith this plexus.

The renal plexus is derived from the semilunar ganglion and outer Renal
side of the solar plexus, and is joined by the smallest splanchnic ^ ^^"^
nerve. The nerves surround the renal artery, having small ganglia
on them, and enter the kidney with the vessels. An offset is given
from the renal to the spermatic plexus (p. 319).

The cceliac plexus is a direct continuation of the plexus around its Cceliac
artery : it is joined by the small splanchnic nerve on each side, and ^ ^^™^
by a branch from the right pneumo-gastric nerve. The plexus
divides like the artery into three offsets — coronary, splenic, and ^^'^^^ ^*®
hepatic.

a. The coronary plexus accompanies the vessel of the same name into core-
to the stomach : it communicates with the left vagus nerve. ^^^'

h. The splenic plexus furnishes nerves to the pancreas, and to the splenic,
stomach along the left gastro-epiploic artery ; and it is joined by an
offset from the right pneumo-gastric nerve.

c. The hepatic plexus is continued on the vena portae, the hepatic and hepatic;
artery, and the bile-duct into the liver, and ramifies on those vessels :
in the small omentum the plexus is joined by oftsets from the left
vagus. The following secondary plexuses are furnished around the the last has
branches of the hepatic artery, and have the same name and distribu- pie^SsSJ
tion as the vessels : ^z.,

A pyloric plexus courses along the small curvature of the pyloric,
stomach.

DJL. 9

338

DISSECTION OF THE ABDOMEN.

gastro-
epiploic,
duodenal,
and cystic.

Ending
of large
splanchnic

small,

and

Ending of
left vagus

and right.

Two other plexuses — right gastro-epiplok and pancreatico-duodenal,
correspond in distribution with the branches of each artery.

A cystic 'plexus passes to the gall-bladder with the artery.

The remaining offsets of the plexus, viz., superior and inferior
mesenteric, aortic, and spermatic, have been already noticed (p. 319) ;
but the derivation of the superior mesenteric and aortic plexuses
from the epigastric centre can now be seen.

Ending of the splanchnic nerves. The large nerve perforates the
crus of the diaphragm, and generally ends altogether in the semi-
lunar ganglion.

The small nerve comes through the same opening in the diaphragm
as the preceding, and joins the coeliac plexus.

The smallest nerve, which is often absent, passes into the supra-
renal and renal plexuses.

Ending of the vagus nerve. The pneumo-gastric nerves pass
on to the stomach : —

The left nerve divides into branches, which extend along the small
curvature, and over the front of the stomach and sends offsets to
the hepatic plexus.

The right nerve is distributed to the posterior surface of the stomach
near the upper border ; it communicates with its fellow, and gives
branches to the cceliac and splenic plexuses.

REMOVAL OP THE STOMACH AND OTHER VISCERiE.

Dissection. The oesophagus should be cut through as it pierces
the diaphragm and the stomach, duodenum, pancreas and spleen are
to be removed by cutting through the vessels and nerves left passing
to them.

THE STOMACH.

Definition.

Separate
and blow
up the
stomach.

Form,

size, and
divisions.

Left end,
and right.

The stomach is the dilated part of the alimentary tube between
the oesophagus and the small intestine, into which the masticated
food is received.

Dissection. The stomach and duodenum must be blown up
moderately with air, and the surfaces cleaned ; but, previously, let
the student detach the spleen and put it aside.

Form and divisions. The stomach is rather pyriform in shape,
and in its natural condition strongly curved with its surfaces looking,
one upwards and forwards, and the other downwards and backwards.
Its size varies much in different bodies, and is sometimes much
diminished by a constriction to the right of the centre : when it
is moderately distended, it is about twelve inches long and four
wide. There are two ends, two orifices, two surfaces, and two
borders or curvatures to be examined.

The left end is called the fundus, and projects upwards to the
summit to the left of the end of the asophagus (fig. 110, p. 301).
The right or pyloric end is much smaller, and tapers to the
duodenum. The stomach is usually narrow and cylindrical a

STRUCTURE OF STOMACH. 339

short distance before the pylorus, and the constricted part is styled
the pyloric canal (Jonnesco).

The cardiac opening, which communicates with the oesophagus, is Cardiac
placed two or three inches from the most prominent part of the openmgs?*'
fundus, and is funnel shaped towards the cavity of the organ. The
pyloric oHfice opens into the duodenum, and is guarded internally
by a muscular band (pylorus), at this spot the stomach is slightly
constricted externally, and a firm circular thickening can be felt.

The anterior, or upper, and the posterior, or lower, surfaces are Surfaces,
somewhat flattened when the viscus is empty, but round when it is
distended, and the parts in contact with them have been referred
to (p. 300).

The upper border or lesser curvature is concave, except for a short SmaU
distance at the pyloric end. The lower border or greater curvature is '

Fig. 126. — Diagram op the ML!.tLLAK Fibres of the Stomach.
The external and middle layers are partly removed.

a. External or longitudinal fibres. e. Oblique fibres, more numerous,

6. Middle or circular. on the left of the cardiac orifice,

c. Sphincter of the pylorus. and covering the great end of the

d. Oblique fibres on the right of stomach,
the cardiac opening.

much longer, convex, and when the organ is distended forms at the and large,
pyloric end a slight projection to the right, which has been named
the antrum pylori or small cul-de-sac.

Structure. In the wall of the stomach are four coats, viz. serous, Four strata
muscular, fibrous, and mucous ; and belonging to these there are
vessels, nerves, and lymphatics.

Serous coat. The peritoneum gives a covering to the stomach, and The serous
is adherent to the surface except at each margin, w^here an interval and adhe-^*^
exists corresponding with the attachment of the small and large '^^'^^•
omentum : in these spaces are contained the vessels, nerves, and
lymphatics. During distension of the stomach the spaces above
mentioned are much diminished.

z 2

3iO

The muscu-
lar coat is
made up of

longi-
tudinal,

circular,

and oblique
fibres.

The fibrous
coat is thin
but firm.

Mucous
coat:

feel and
colour ;

folds ;

thickness ;

disposition
at pylorus.

DISSECTION OF THE ABDOMEN.

The muscular coat will be laid bare by the removal of the serous
covering. Its fibres are unstriated or involuntary, and arranged in
three sets, viz., longitudinal, circular, and oblique, in the order
mentioned from without inwards.

The longitudinal fibres (fig. 126, a) are derived from the oesophagus ;
they spread over the surface, and are continued to the pylorus and
the small intestine. The fibres are most marked along the borders,
particularly at the smaller one ; and at the pylorus they are stronger
than in the centre of the stomach.

The circular fibres (fig. 126, b) form the middle stratum, and will
be best seen by removing the longitudinal fibres near the pylorus.
They reach from the left to the right end of the stomach, but do not
encircle the fundus. At the pylorus they are most numerous and
strongest, and form a ring or sphincter (c) round the opening.

The oblique fibres (fig. 126, e) are continuous with the circular or deep
layer of fibres of the oesophagus. On the left and right of the cardiac

orifice they are so arranged as to form
a kind of sphincter {d and e) (Henle) ;
those on the left (e), the strongest, arch
over the great end of the stomach, and
spread out on the anterior and pos-
terior surfaces, gradually disappearing
on them.

Dissection. Eemove the muscular
layers over a small space and iha fibrous
or submucous coat will appear as a white
shining stratum of areolar tissue. This
coat gives strength to the stomach, and
serves as a bed in which the larger
vessels and nerves ramify before their
distribution to the mucous layer. If a small opening be made
in this submucous coat, the mucous coat will project through it.
Finally the stomach should be opened along the lesser curvature to
near the pylorus. The finger should be passed through the pylorus
to feel its sphincter, and then the incision should be continued
through the pylorus and along the convexity of the duodenum
to its termination.

The mucous coat will come into view, but the appearances now
described can be recognised only in a recent specimen, or in one
well preserved by formalin injection.

This coat is a softish layer, of a pale rose colour soon after death,
in the healthy condition. In the empty state of the stomach the
membrane is less vascular than during digestion ; and in infancy the
natural redness is greater than in childhood or old age. When the
stomach is contracted the membrane is thrown into numerous wavy
ridges or rugce, Avhich become longitudinal along the great curvature,
towards the pylorus.

The thickness of the mucous membrane is greatest near the
pylorus ; and at that spot it forms a fold, opposite the muscular

Fig. 127. — Alveolar Depres-
sions OF THE Mucous MEM-
BRANE OF THE Stomach,

MAGNIFIED 32 DiAMETERS,

WITH THE Minute Tubes
opening into them. (sprott
Boyd).

DUODENUM AND PANCREAS DISSECTED. 341

ring, which assists in closing the opening. If this membrane and
the submucous layer are removed from the pyloric part of the
stomach, the ring of muscular fibres (sphincter of the pylorus) will
be more perfectly seen.

With the aid of a lens, the surface of the mucous membrane, when On the sur-
well washed, may be seen to be covered by shallow depressions or o^^aiveoi?*;
alveoli (fig. 127), which measure from ^^th to x^th of an inch their size,
across. Generally hexagonal or polygonal in outline, the hollows shape,
become larger and more elongated towards the small end of the ^^^ appear-
stomach ; and near the jDylorus the margins of the alveoli project,
and become irregular. In the bottom of each depression are the
apertures of minute tubular glands.

Blood-vessels. The arteries of the stomach are derived from the Arteries ;
branches of the coeliac axis, and have been seen to form an arch along
each curvature (pp. 332 et seq.). From these arches branches pass to
both surfaces of the stomach, and after supplying the muscular coats
divide in the submucous layer into minute vessels which enter the
substance of the mucous membrane. The veins have a corresponding veins ;
arrangement, and pass to the portal system (p. 334).

Lymphatics. The lymphatic vessels proceeding from the stomach ijinphatics ;
run with the blood-vessels, and have a few small glands connected
with them along the two curvatures.

Nerves. The nerves are derived from the pneumo-gastric and and nerves,
sympathetic, and can be followed to the fibrous coat : small ganglia
have been observed on them.

THE DUODENUM AND PANCREAS DISSECTED.

Dissection. The duodenum will now be washed and its mucous
surface examined. The commencement of the valvulae conniventes
one or two inches from the pylorus will be noticed, and the opening
of the biliary and pancreatic ducts examined.

The aperture of the common hile and pancreatic ducts (Gg. 128, e) Opening of
is a narrow orifice, from three to four inches below the pylorus, and ' ®' "*^ »
situate in a small prominence of the mucous membrane, at the where
inner and posterior part of the duodenum. A probe passed into the ^' ^
bile-duct will show its oblique course (half an inch or more) under
the mucous coat. Occasionally the pancreatic duct opens by a
distinct orifice.

Structure of the common bile-duct. The bile-duct consists of an Two coats
external, strong fibrous layer, and of an internal mucous coat. On ^uct^ ^^
the surface of the inner membrane are the openings of numerous
branched mucous glands, which are embedded in the fibrous coat ; glands,
some of them are aggregated together, and are visible with a lens.

The coats of the duodenum are like those of the rest of the small
intestine (pp. 321 et seq.), but Brunner's glands should be noticed.

The Glands of Brunner are small compound bodies, similar to the Glands of
buccal and labial glands of the mouth, which exist in the duodenum. ^""°^'^-
Thev are most numerous for a distance of one or two inches near

342

DISSECTION OF THE ABDOMEN.

Trace out
the duct.

It is a

compound

gland,

wichout a

distinct

capsule.

the pylorus, and there they are visible without a lens, being nearly
as large as hemp-seed and appear lost after removal of the muscular
coat.

Dissection. The pancreas should now be placed on its anterior
surface, and the excretory duct traced from the head to the tail by
cutting away the substance of the gland. The duct will be recognised
by its whiteness.

Structure. The pancreas resembles the parotid gland in struc-
ture, consisting of separate lobules, each of which is provided with a
special duct. It is destitute of a distinct capsule ; but it is surrounded
by areolar tissue, which projects into the interior, and connects
together its smaller pieces. The lobules are soft and loose, and of a

Fig. 128. — A Small Piece of the Duodenum opened, with a part of
THE Pancreas, showing the Termination of the Bile and
Pancreatic Ducts (Henle).

a. Duodenum.

h. Pancreas.

c. Common bile-duct.

d. Pancreatic duct.

e. Common opening of the ducts

in the intestine.

The duct of
the gland :

extent ;

branches ;

size and
structure.

greyish white colour, and are united into larger masses by areolar
tissue, vessels, and ducts.

The duct of the pancreas (canal of Wirsung ; fig. 128, d) extends
the whole length of the gland, and is somewhat nearer the lower
than the upper border. It begins in the tail of the pancreas, where
it presents a bifurcated extremity ; and as it continues onwards to
the head, it receives many branches. It is readily recognised from
its whiteness on dividing the gland longitudinally. Of the tributary
branches, the largest is derived from the lower part of the head of
the pancreas.

An accessory duct is often found a short distance above the
main one.

The duct measures from ^ih. to '^th of an inch in diameter near
the duodenum. It is formed of a fibrous coat with a very smooth
mucous lining.

OBVIOUS STRUCTURE OF SPLEEN.

343

Vessels J hjmphatics, and nerves. The arteries and veins have been Vessels and
described (pp. 332 et seq.) ; and the lymphatics pass to the coeliac ^^^^'^^•
glands. The nerves are furnished by the solar plexus.

THE SPLEEN.

The spleen is a vascular spongy organ of a bluish or purple Consistence
colour, sometimes approaching to grey. Its texture is friable, and ^" coio^ir-
easily broken under pressure.

The viscus is somewhat elliptical in shape, and is placed obliquely Form and
behind the great end of the stomach. Its size varies much. In the position,
adult it measures commonly about five inches in length, three orgi2eaud
four inches in breadth, and one inch to one inch and a half in thick-
ness. Its weight lies between four and ten ounces, and is rather weight.

g^ m O R BOR O E H

Fig. 129. — The Spleen, seen from the Right.

less in the female than the male. Its relations are described
on p. 306.

At the outer or phrenic aspect it is convex towards the ribs. On
the opposite side a longitudinal ridge separates an anterior or gastric
surface from a narrow internal or renal surface, both of which are
concave. Just in front of the ridge is a groove, or more commonly
a series of small depressions, where the branches of the vessels
enter : this part is called the hilum of the spleen.

The anterior border is thinner than the posterior, and is often
notched. Of the two extremities, the lower is more pointed than
the upper.

Small masses of splenic substance, or accessory spleens (spleniculi),
varying in size from a bean to a moderate-sized plum, are found
occasionally, near the hilum of the spleen, in the gastro-splenic
omentum, or in the great omentum.

Structure. Enveloping the spleen are two coverings, a serous
and a fibrous, and the spleen itself is formed of a network of fibrous
or trabecular tissue, which contains in its meshes the splenic pulp.
Throughout the mass the blood-vessels and the nerves ramify. It
has no duct.

Surfaces are
phrenic,
gastric,
and renal.

Borders and
extremities.

Sometimes

accessory

spleens.

Two coats
and special
material.

344

DISSECTION OF THE ABDOMEN.

Serous coat

nearly

complete.

Fibrous coat
sends in-
wards pro-

structure.

Interior of

disposition
of fibrous
tissue

to form an

areolar

structure.

Pulp of
spleen.

Malpighian
bodies.

Splenic
artery :

ending ;

Vein begins
by open

branches
anastomose.

Lymphatics

Nen'es.

The serous or peritoneal coat encases tlie spleen, covering the
surface except at the hilum and the ridge behind. It is closely
connected to the subjacent fibrous coat.

The fibrous coat (tunica propria) gives strength to the spleen,
and forms a complete case for it. At the hilum this investment
passes into the interior with the vessels, to which it furnishes
sheaths ; and if an attempt is made to detach this coat, numerous
fibrous processes will be seen to be connected with its deep surface.
Its colour is whitish; and it is made up of areolar and elastic
tissues.

Dissection. The spongy or trabecular structure will best appear
by washing and squeezing a piece of fresh bullock's spleen under
water, so as to remove the inner grumous-looking material.

The trabecular tissue (fig. 130) forms a
network through the whole interior of the
spleen, similar to that of a sponge, which
is joined to the external casing, and forms
sheaths around the vessels. Its processes or
threads are white, flattened or cylindrical,
and consist of fibrous and elastic tissues,
with a few muscular fibres. The interstices
communicate freely together, and contain the
pulp of the spleen.

The splenic pulp is a soft red-brown mass,
which is lodged in the areolae of the trabe-
cular structure, and consists in great part of
blood. In a fresh section small whitish spots
(eVth of an inch in diameter) may be seen
scattered amongst the dark pulp : these are
the Malpighian corpuscles of the spleen —
lymphoid nodules attached to the small
branches of the artery.

Blood-vessels. The larger branches of the
splenic artery are surrounded by sheaths of
fibrous tissue in the trabeculoe ; but the
smallest branches leave the sheathing, and break up into tufts of
capillaries, which are said to open into the fine meshes of the
spleen substance. There are few or no anastomoses between the
arterial branches in the organ.

The splenic vein is supposed to begin in the meshes of the splenic
pulp by open channels. The small branches resulting from the
union of these radicles anastomose freely together, and unite into
trunks larger than the accompanying arteries, which issue by the
hilum of the spleen.

Lymphatics and nerves. The lymphatics are superficial and deep,
and, leaving the organ at the hilum, traverse small glands lying
along the splenic vessels on their way to the cceliac glands. The
nerves come from the solar plexus, and surround the artery and its
branches.

Fia. 130. — Trabecular
Structure op the
Spleen of the Ox.

REMOVAL OF THE LIVER. 345

REMOVAL OF THE LIVER

Dissection. The liver should now be removed from the abdo-
men, iu order that it may be more particularly examined. Begin in
front by cutting through the round and falciform ligaments. Then,
drawing the liver downwards, cut through the long left lateral liga-
ment and the short right one, and the upper layer of the coronary-
ligament, taking care not to cut the diaphragm. Beyond the upper
layer of the coronarj' ligament there is an area over which the
posterior surface of the liver is not covered by peritoneum, but is
simply bound to the diaphragm by areolar tissue, and from which it
can be separated by the handle of the scalpel. The inferior vena
cava, as it leaves the liver to pierce the diaphragm, will now be
exposed, and it must be cut across. Finally, the lower layer of the
coronary ligament will be divided, and the liver will come away with
a portion of the inferior cava embedded in it, as that vessel had been
divided already before its entry into the liver.

THE LIVER.

The liver secretes the bile, and is the largest gland in the body. Office of the
Its duct opens into the duodenum with that of the pancreas.

Dissection. Preparatory to examining the liver, the vessels at the Clean
under surface should be' dissected out (fig. 131, p. 346). ThiSunde?°°
proceeding will be facilitated by distending the vena cava and vena surface ;
portae with tow or cotton- wool, and the gall-bladder with air through
its duct. The several vessels and the ducts are then to be defined,
and the gall-bladder is to be cleaned.

On following outwards the left branch of the portal vein to the follow left
longitudinal or antero-posterior fissure, it will be found united vena portse.
anteriorly with the round ligament (c) or the remains of the
umbiHcal vein, and posteriorly with the thin fibrous remnant of the
ductus veuosus [d).

The LIVER is of a red-brown colour and firm consistence, and Colour and

COIISISl^IICC *

weighs commonly in the adult from three to four pounds. Trans- ^.^^ ^^,
versely the gland measures from ten to twelve inches ; from front to measiu^-
back between six and seven inches ; and in thickness, at the right ments.
end, about three inches, but this last measurement varies much with
the spot examined.

The natural shape of the liver when within the body is very Form
different from the form it assumes when removed and placed on a removed ;
flat surface, unless it has been previously hardened in situ. As
already described (pp. 304 et seq.) the liver has five surfaces, of ^^^^^loos-
which the anterior, superior and right have already been examined,
while the posterior and inferior can now be fully seen. The inferior
and posterior surfaces are farther subdivided into lobes by fissures
which contain vessels, and marked by fossae and impressions.

The peritoneal ligaments are described at p. 313.

The Inferior Surface (fig. 131) is rendered irregular by fissures g^^acg^
and fossae ; and a longitudinal sulcus separates it into a large right

346

DISSECTION OF THE ABDOMEN.

Posterior
surface.

and a small left lobe. It embraces the li ver substance as far as the
upper part of the renal impression on the right side, as far as the
Spigelian lobe in the middle, and it includes the whole of the left
lobe except a small part to the left of the Spigelian lobe which lies
upon the oesophagus.

The Posterior Surface, which is also divided into two by a con-

FiG. 131. — The Liver, viewed from
(After
Subdivisions and markings :

On the left lobe—
ce g. (Esophageal groove.
g i. Gastric impression.
o t. Omental tuberosity.

On the right lobe —
aS'^. Spigelian lobe,
c I. Caudate lobe.
q I. Quadrate lobe.
sri. Suprarenal impression.
di. Duodenal impression.
ri. Renal impression,
c i. Colic impression.

Vessels, dr. :
V c. Inferior vena cava.

Below and slightly from Behind
His.)

p V. Portal vein.

h a. Hepatic artery.

b d. Common bile-duct : the last
three occupy the portal fissure.

Z t. Ligamentum teres, lying in the
fore part of the longitudinal fissure.

g b. Gall-bladder.

Cut edges of peritoneum :

so. The two layers of the small
omentum.

i c I. The inferior layer of the
coronary ligament.

rll. Right lateral ligament.

* Surface uncovered by peritonenm.

tinuation of the longitudinal fissure, is broad over the right lobe, but
narrow on the left. In the centre is a hollow for the spine, upon
which the Spigelian lobe lies, to the left of this is the depression for
the oesophagus, and to the right the inferior vena cava is partly
embedded in the liver. On the right of the cava, the surface is
rough between the layers of the coronary ligament where it was
adherent to the diaphragm ; and close to the vein is a small hollow

LOBES OF THE LIVER. 347

{suprarenal impression ; sr i) into wliicli the right suprarenal body is
received.

Border. The anterior border is thin, and is marked by two notches ; Anterior
one is opposite the longitudinal fissure on the under surface before ^ ^^'
alluded to, and the other is over the large end of the gall-bladder.

Extremities. The right extremity is thick and rounded ; and the Extremities,
left is thin and flattened.

Lobes. On the inferior and posterior surfaces the liver is divided Lobes are
primarily into two lobes, a right and a left, by the antero-posterior two large,
or longitudinal fissure ; and occupying part of the right lobe are ^Jj^J^™®
three others, viz., the quadrate. Spigelian, and caudate lobes.

The left lobe is smaller and thinner than the right ; on its posterior Left lobe
aspect is a groove {oesophageal groove ; fig. 131, oe g) which lodges the by^sopha-
lower end of the oesophagus, and widens out below into a hollow for ^"^ *"^

1 . . .. . , stomach.

the stomach {gastric impression; g i), occupy mg the greater part of
the under surface of the lobe ; but next to the longitudinal fissure
is a considerable elevation {omental tuberosity ; o t), which lies against
the small omentum and the lesser curvature of the stomach.

The right lobe forms the greater part of the liver, and is separated Right lobe
from the left by the longitudinal fissure below and behind, and by P^®^®" ^
the suspensory ligament above. The under surface has a fossa for fossa for
the gall-bladder, and is marked to the right of this by three impres- ga^i-Wadder
sions ; — the one next to the gall-bladder is the duodenal impression impressions,
(fig. 131, d i), and corresponds to the second part of the duodenum ; ^T^^^ "
more externally is the renal impression (r i) for the right kidney ; kidneyi
and farther forwards is the colic impression {c i) where the liver rests colon,
on the transverse colon. On the posterior surface is the suprarenal and supra-
impression (sr i) already referred to. The three following so-called '^^"^ ^'
lobes also are portions of the surface of the right lobe : —

The quadrate lobe {q I) is situate between the gall-bladder and the and three
longitudinal fissure. It reaches anteriorly to the margin of the ^f^^^ ^°^^^'
liver, and posteriorly to the fissure (transverse) by which the vessels quadrate,
enter the viscus. It is impressed by the pyloric end of the stomach
and the first part of the duodenum.

The Spigelian lobe {S I) is the part between the longitudinal fissure Spigelian,
and the inferior vena cava, and belongs to the posterior surface of
the liver. It forms the bottom of the hollow for the spine, from
which it is separated by the diaphragm and the aorta ; and it appears
on the under aspect of the organ as a slight projection behind the
transverse fissure.

The caudate lobe {c I) is a narrow, elongated eminence, which is and caudate,
directed from the Spigelian lobe behind the transverse fissure, so as
to form the posterior boundary of that sulcus. Where the fissure
terminates this projection subsides in the right lobe.

Fissures. Extending nearly halfway across the right part of the Three
liver, between the Spigelian and caudate lobes on the one hand, and viz., '
the quadrate lobe on the other, is the transverse or portal fissure. It
is situate much nearer the back than the front, and contains the |^j ^^
portal vein, hepatic artery, and the nerves, ducts, and lymphatics of transverse,

348

DISSECTION OP THE ABDOMEN.

longitudi-
nal

(sub-divided
into two
parts),

and one for
vena cava.

Vessels in
the trans-
verse
Assure.

Hepatic
duct.

Hepatic
artery.

Vena portse.

Umbilical
vein in tlie
foetus ;

condition
after birth.

the liver. At the left end it is united at a right angle with the
longitudinal fissure.

The longitudinal fissure extends from the front to the back of the
liver, between the right and left lobes ; that i?, between the left lobe
and the quadrate in front and the Spigelian behind. In it, anterior
to the transverse fissure, lies the remnant of the umbilical vein {I t\
which is called the round ligament, and is oftentimes arched over
by a piece of the hepatic substance (pons hepatis) ; and behind that
fissure is a small fibrous cord, the remains of the vessel named the
ductus venosus in the foetus, which will be found running deeply in
the fissure between the Spigelian and the left lobe. In reference
to these structures the fore part of the longitudinal fissure is often
spoken of as the fissure for the round ligament, and the back part as the
fissure for the ductus venosus.

The groove, ot fissure for the vena cava is placed on the right side of
the Spigelian lobe, and is frequently bridged over by an extension
of the Spigelian to the right. If the cava {v c) be opened, two or
three large and some smaller hepatic veins will be observed
entering it.

The groove which lodges the gall bladder is often inappropriately
called the fissure for the gall bladder.

Vessels in the Transverse Fissure. The vessels in the
transverse fissure, viz., portal vein, hepatic artery and duct have
the following position : the duct in anterior, tlie portal vein
posterior, and the artery between the other two.

The hepatic duct is formed by two branches, — one from the right,
and one from the left lobe, which soon blend in a common tube.
After a distance of one inch and a half it is joined by the duct of the
gall-bladder ; and the union of the two gives rise to the common
bile-duct (6 d).

The hepatic artery {h a) is divided into two for the chief lobes, and
its branches are surrounded by nerves.

The portal vein [p v) divides, like the artery, into two trunks for
the right and left lobes, and gives an offset to the Spigelian lobe ;
its left branch is the longer.

Foetal condition of the umbilical vein. Before birth the umbilical
vein occupies the longitudinal fissure, and opens posteriorly into the
vena cava ; the portion of the vessel behind the transverse fissure
receives the name ductiis venosus. Branches are supplied from it to
both lobes of the liver ; and a large one, directed to the right lobe,
is joined by the portal vein. Placental or purified blood courses
through the vessel at that period.

Adult state. After birth the part of the umbilical vein in front of
the transverse fissure is closed, and becomes eventually the round
ligament or ligamentum teres. The ductus venosus is also obliterated,
only a thin cord remaining in its place. But the lateral branches
remain open, and subsequently form some of the divisions of the
portal vein. Occasionally the ductus venosus is found pervious for
some distance.

OBVIOUS STRUCTUEE OF THE LIVER. 349

Obvious structure of the liver. The substance of the liver Lobular

consists of small masses called lobules, together with vessels which * ^^^ ^'®'

are concerned both in the production of the secretion, and in the

nutrition of the orf^an. The whole is surrounded by a fibrous and encased by

two coats,
a serous coat.

Serous coat. The peritoneum invests the liver almost completely, Serous coat,
and adheres closely to the fibrous coat. At certain spots intervals
exist between the two, viz., in the fissures occupied by vessels, along where
the line of attachment of the ligaments, and at the surface touching
the gall-bladder.

The fibrous covering is very thin, but it is rather stronger where Fibrous
the peritoneum is not in contact with it. It invests the liver, and

• f • -, 1 n^ 1 1 prolonged

IS continuous at the transverse fissure with the fibrous sheath into the
(capsule of Glisson) surrounding the vessels in the interior. When ^°^"°^-
the membrane is torn from the surface, it will be found connected
with fine shreds entering into the liver.

Size and form of the lobules. The lobules (fig. 132, I) constitute Lobules of
the proper secreting substance, and can be seen either on the
exterior of the liver, on a cut surface, or by means of a rent in
the mass. As thus observed, these bodies are about the size of a size and
pin's head, and measure from ^th to ^^th of an inch in diameter. ^PP^*^'^^® «
Closely massed together, they possess a dark central point ; and form ;
there are indications of lines of separation between them, though
they are to some extent united together. By means of transverse
and vertical sections of the lobules, their form appears flattened on
the exterior, but they are many-sided in the interior of the liver, position to

vpins

They are clustered around the smallest divisions of the hepatic
vein, to which each is connected by a small twig issuing from the
centre, something like the union of the stalk with the body of a
small fruit.

Vessels of the liver. Two sets of blood-vessels ramify in the Vessels in
liver : — One enters the transverse fissure, and the branches are ^ ^^^'
directed transversely in spaces (portal canals) where they are
enveloped by areolar tissue. The other set (hepatic veins) runs from
the anterior to the posterior border of the liver for the most part
without a sheath. The ramifications of these different vessels are to
be followed in the liver.

The capsule of Glisson is a layer of areolar tissue, which envelops Capsule of
the vessels and the ducts in the transverse fissure, and is continued ^^^°^-
on their branches in the portal canals. In this sheath the vessels
ramify, and become minutely divided before their termination in
the lobules. If a transverse section is made of a portal canal, the
vessels will retract somewhat into the loose surrounding tissue.

The portal vein ramifies in the liver like an artery ; and the Portal vein
blood circulates through it in the same manner, viz., from trunk
to branches. . After entering the transverse fissure the vein divides occupies
into large branches ; these lie in the portal canals or spaces, with ^^^^g
offsets of the hepatic artery, the hepatic duct, and the nerves and
lymphatics (fig. 132, p). The division is repeated again and again

850

DISSECTION OF THE ABDOMEN.

and supplies
branches ;

receives
vaginal
branches.

Hepatic
artery
nourishes
the vessels
and capsule :

ending in
lobules.

Hepatic
veins with-
out a
sheath,

begin in the
lobules,

and end in
the vena
cava.

Biliary
ducts form

right, left,
and common
hepatic
ducts.

Structure
of medium-
sized ducts.

until the last branches of the vein (interlobular) penetrate between,
the lobules, where they communicate together, and supply the
hepatic substance.

In the portal canals the offsets of the vena portae are joined by
small vaginal and capsular veins, which convey blood from branches
of the hepatic artery.

The hepatic artery (fig, 132, c), while surrounded by the capsule,
furnishes vaginal branches, which ramify in the sheath, giving it a
red appearance in a well-injected liver, and supply twigs to the
coats of the portal vein and biliary ducts, and to the areolar tissue :
from the vaginal branches a few offsets {capsular) are given to the

coat of the liver. Finally, the
artery ends in fine interlobular
brandies, from which offsets
enter the lobules.

The hepatic veins (vense cavse
hepaticse) begin by small intra-
lobular veins from the centre of
the lobules ; these are received
into the sublobular branches,
which anastomose together, and
unite into larger vessels. Fin-
ally, uniting with neighbouring
branches to produce larger
trunks, the hepatic veins are
directed from before backwards
to the vena cava inferior, into
which they open by large ori-
fices. The hepatic veins may be
said to be without a sheath,
except in the larger trunks ; so
that when they are cut across
the ends remain patent, in con-
sequence of their close connec-
tion with the liver structure.

Hepatic duct. The biliary
ducts follow the portal vein in
their mode of branching, and run with the other vessels in the portal
canals (fig. 132, d). They issue from the liver at the transverse
fissure in right and left trunks, which by their union form the
common hepatic duct."^

Structure. The moderately-sized hepatic ducts consist of a fibrous
coat, lined by a mucous layer ; and penetrating the wall is a longi-
tudinal row of openings, on each side, leading into sacs, and into
branched tubes which sometimes communicate.

Fia. 132. — Vessels in a Portal
Caxal, and the Lobules of
THE Liver (Kiernan).

I. Lobules of the liver.

p. Branch of the portal vein, with
a, a. small branches which supply
interlobular offsets.

c. Hepatic artery,

d. Hepatic duct.

^, i. Openings of interlobular
branches of the portal vein.

* Aberrant ducts exist between the pieces of the peritoneum in the left
lateral ligament of the liver, and in the bands bridging over the round ligament
and vena cava ; they anastomose together, and are accompanied by branches
of the vessels of the liver, viz., portal vein, hepatic artery, and hepatic vein.

THE GALL-BLADDER.

351

Lymphatics of the liver are superficial and deep. The superficial Lympha-
of the upper surface in part join the lymphatics of the thorax by superficial,
piercing the diaphragm, and enter the anterior mediastinal glands ;
those of the under surface mainly join the deep lymphatics issuing
at the portal fissure.

The deep lymphatics accompany both sets of vessels in the liver ; and deep,
those with the portal vein descend through some small glands in
the lesser omentum and end in the coeliac glands ; while those
accompanying the hepatic veins pass through the diaphragm, and
enter the glands of the posterior mediastinum.

Nerves come from the sympathetic and Nerves,

the pneumo-gastric, and ramify with the
hepatic artery.

THE GALL-BLADDER.

The gall bladder (fig. 131, g b, p. 346) is
the receptacle of the bile. It is situate in
a depression on the under surface of the
right lobe of the liver, and to the right of
the quadrate lobe. It is pear-shaped, and
its larger end (fundus) is directed forwards
beyond the margin of the liver ; while
the smaller end (neck) is turned in the
opposite direction, and bends downwards
to terminate in the cystic duct by a
zigzag part.

In length the gall-bladder measures three
or four inches, and in breadth rather more
than an inch at the widest part. It holds
from an ounce to an ounce and a half.

By one surface it is in contact with the
liver, and on the opposite it is covered by
peritoneum. The larger end touches the
abdominal wall opposite the cartilage of
the ninth rib (fig. Ill, p. 303), where it
is contiguous to the transverse colon.
The neck is in contact \vith the duodenum.

Structure. The gall-bladder possesses a
peritoneal, a fibrous and muscular, and a
mucous coat.

The serous coat is stretched over the under or free surface of the
gall-bladder, and surrounds the fundus.

The fibrous coat is strong, and forms the framework of the sac ;
intermixed with it are some involuntary muscular fibres^ the chief
being longitudinal, but others circular.

Dissection. The gall-bladder should now be slit open and washed
out to show its lining.

The mucous coat is marked internally by numerous ridges and
intervening depressions, which give an alveolar or honeycomb

Gall
Bladder:

situation ;
form;

size ;

relations.

133. — Gall-bladder
AND ITS Duct.

a. Gall-bladder.

b. Cystic duct.

c. Ridges in the interior.

d. Common bile-duct.

e. Common hepatic duct.

Structure
of wall.

Serous coat.

Fibrous and

muscular

stratum.

Mucous
layer is
alveolai- on
surface;

352

DISSECTION OF THE ABDOMEN.

appearance to the surface. This condition will be seen, with the
aid of a lens, to be most developed about the centre of the sac, and to
diminish towards each extremity. In the bottom of the larger pits
are depressions leading to recesses.

Where the gall-bladder ends in the cystic duct (fig. 133) its coats
project into the interior, and give rise to ridges resembling those in
the sacculated large intestine.
Duct of gall- The cystic duct (b) joins the hepatic duct at an acute angle, to
form the common bile-duct. It is about an inch and a half long,
and is distended and somewhat sacculated near the gall-bladder.

Anterior border of pancreas,
leen.

projections
of the wall.

bladder ;

Ascending colon. Superior mesenteric vessels.

Lower part of the splenic
flexure of the colon.

Fig. 134. — Deep Viscera of the Abdomen op a Child.
(From a specimen in the Charing Cross Hospital Museum.)

structure. Structure. The coats of the duct are formed like those of the sac
from which it leads, but the muscular fibres are very few. The
mucous lining is provided with glands, as in the hepatic and common
bile-ducts.

Mucous coat On opening the duct the mucous membrane may be observed to
form about twelve semi-lunar projections (6g. 133, c), which are
arranged obliquely around the tube, and increase in size towards
the gall-bladder. This structure is best seen on a gall-bladder
which has been inflated and dried, as in this state the parts of the
duct between the ridges are most stretched.

Blood-vessels and nerves. The vessels of the gall-bladder are named
cystic. The artery is a branch of the hepatic ; and the cystic vein
opens into the right branch of the vena portse. The nerves are

like a screw.

Artery and
vein :

nerves and

THE ANATOMY OF THE^ KIDNEY. 353

derived from the hepatic plexus, and entwine around the vessels.

The lymphatics follow the cystic duct, and join the lymphatics on lymphatics.

the under surface of the liver.

THE KIDNEYS AND THE URETERS.

Dissection. The student will now return to the abdomen, and
thoroughly clean up the kidneys and the suprarenal bodies and their
vessels, removing the fat and enveloping areolar tissue, which is yjarti-
cularly strong at the upper part of each kidney where it passes on to
the diaphragm. Care should be taken not to injure the suprarenal
bodies, which somewhat resemble the fat. After the anterior surface
of the left kidney has been examined, its vessels will be cut through
about an inch from the hilum, and the kidney, with the upper
four inches of the ureter, removed for separate examination. The
parts behind the kidney will then be cleaned, taking care of the
anterior divisions of the last dorsal and first lumbar nerves as they
cross outwards over the quadratus lumborum muscle.

The KIDNEYS have a characteristic form (fig. 134 and fig. 135, Kidney:
p. 354), resembling an oval with one side (the inner) somewhat ^"" '
hollowed out, and they are compressed from before backwards.

With the special form above mentioned, each kidney is of a deep Colour;
red colour, and has an even surface. Its average length is about four size ;
inches ; its breadth two and a half inches ; and its thickness rather
more than one inch ; but the left is commonly longer and more
slender than the right kidney. Its usual weight is about four ounces and weight,
and a half in the male, and rather less in the female. The left
kidney is slightly heavier than the right.

The upper extremity or pole, of the kidney is broader than the Extremi-
lower, and is in contact with a suprarenal body. The lower pole is ^ ^'
more pointed.

The outer border is convex ; but the inner is excavated, and is borders.
marked by a longitudinal fissure — the hilum. In the fissure the Contents of
vessels are usually placed so that the divisions of the renal vein are ^'

in front, the ureter behind, and the branches of the artery between position,
the two. On the vessels, the nerves and lymphatics ramify; and
areolar tissue and fat surround the whole. The fissure leads into
a hollow named the sinus, in which the vessels and the duct are Sinus,
contained before they pierce the renal substance.

For the purpose of distinguishing between the right and the left To distin.
kidneys, let the excavated margin be turned inwards, with the ureter ^om left.
or excretory tube behind the other vessels ; and let that end of the
viscus be directed downwards, towards which the ureter is naturally
inclined.

The surface marking of the kidneys has been described on p. 306.
They lie opposite the last dorsal and the upper two or three
lumbar vertebrae ; the right kidney being somewhat lower than
the left. Both overlie the twelfth rib in their upper part ; the Position,
upper pole of the right kidney reaches above that rib and the
upper pole of the left commonly overlies the eleventh rib.

D.A. A A

354

Surfaces.

of right
kidney,

DISSECTION OF THE ABDOMEN.

Their anterior surfaces look somewhat outwards, and are more
convex than the posterior, which, latter, look partly inwards and are
moulded on the posterior abdominal wall.

In well-preserved specimens the anterior surfaces are distinctly-
facetted by the pressure of the overlying viscera ; the distinctness
of the ridges indicating the extent of the moulding that the kidney
has undergone.

The position of the overlying parts has already been studied, and
the extent of the contact with the subjacent kidneys is diagramraati-
cally shown in the accompanying figure (135).

A large part of the anterior surface of the right kidney is in
contact with the liver, and its limit below and internally is usually
defined by a well-marked ridge. The whole of this surface is
covered by peritoneum except at the upper and inner angle, where
the suprarenal body overlaps the kidney. The lower end of the
kidney usually presents a well-defined surface looking downwards

of left
kidney.

Posterior
surfaces.

Right Kidney. Left Kidney.

Fia. 135. — Diagram of the Relations op the Anterior and Outer
Aspects of the Kidneys.

i.v.c. marks the surface in contact with the vena cava.

The

and forwards, where it is impressed by the ascending colon,
duodenum lies, to a variable extent, over the inner part.

The spleen above and the descending colon below usually give
rise to distinct impressions on the outer margin of the left kidney ;
the suprarenal body, along the inner border above, reaches down as
far as the hilum ; the pancreas extends across in front of the hilum
as far as the splenic impression, and a small part of the anterior
surface of the kidney above this is usually in contact with the
stomach. The lower half of the anterior surface below the pancreas
presents a large surface, upon which lie coils of the jejunum.

The POSTERIOR SURFACE of each kidney presents an inner area,
where it lies against the psoas muscle and the crus of the diaphragm
as these parts clothe the sides of the bodies of the vertebrae, and an

THE STRUCTURE OF THE KIDNEY.

outer area which looks backwards and overlies the twelfth rib and the
diaphragm tor about its upjjer third, and below this the quadratus
luraborum. Crossing outwards and downwards behind this part of
the kidney the anterior divisions of the last dorsal and first lumbar
nerves will be seen upon the quadratus lumborum (fig. 138, p. 363).
When the kidney has been hardened in situ, particularly in thin
subjects, an indentation produced by the first two lumbar transverse
processes may be present near the hilum.

Dissection. The left kidney should now be cut through from
the inuer to the outer border, and to remove the loose tissue from

the vessels and the divisions of
the excretory duct. The sinus
containing the blood-vessels now
comes completely into view.

The interior of the kidney (fig.
136) is seen on section to con-
sist of an external granular or
cortical portion, and of an inter-
nal part made of darker coloured
pyramidal masses converging
towards the centre.

The "pyramidal masses (pyra-
mids of Malpighi ; d) are from
eight to eighteen in number, but
generally more than twelve. The
apex of each mass which is free
from cortical covering, is directed
to the sinus, and ends in a
smooth, rounded part, named
mamilla or 'papilla. In it are
the openings of the urine tubes,
which are about twenty in num-
ber in each papilla, some being
situate in a central depression,
and others on the surface ; and
it is surrounded by one of the
divisions (calyx, c.) of the excre-
tory tube. Occasionally two of the masses are united in one papillary
termination. The base is embedded in the cortical substance, and
from it slender processes are continued into the cortical covering.
The cut surface of the pyramid has a striated appearance, owing to
the arrangement of the uriniferous tubules composing it, and the
bloo<l-vessels. If the mass is compressed in a fresh kidney, urine
will exude from the tubes through the apertures in the apex.

The cortical 'part (fig. 136, e) forms about three-fourths of the
kidney ; it covers the pyramidal masses with a layer nearly a quarter
of an inch in thickness, and sends prolongations between them nearly
to their apices. Its colour is of a light red, unless the kidney is
blanched ; and its consistence is so slight that the mass gives way

A A 2

355

Open the
kidney, and
clean the
vessels.

Renal
substance
divided into
cortical and
pyramidal.

Pyramids :
number ;

Fig 136. — Section through a Piece
OP THE Kidney, showing the
Medullary and Cortical Por-
tions AND THE Beginning op
the Ureter.

a,. Ureter.
h. Pelvis.

c. Calyx.

d. Pyramids.

e. Cortical portion of the kidney.

apex

ends in
papilla ;

Structure

base.

Extent of
cortical
substance :

colour ;
consistence.

356 DISSECTION OF THE ABDOMEN.

beneath the pressure of the finger. In the injected kidney red points

(Malpighian bodies) are scattered through the cortex, giving it a

granuh\r appearance.
Fibrous The kidney has a fibrous tunic or capsule, which is connected to

^°*^ the glandular substance by fine processes and vessels, and is readily

detached from it by slight force. At the inner margin of the

sends in kidney it sinks into the sinus, where it sends processes on the enter-
offsets

ing vessels, and becomes continuous with the outer coat of the

excretory duct.

Blood- Blood-vessels. The artery and vein distributed to the kidney

yesse s. ^^^^ ^,^^^ large in proportion to the size of the organ they supply.

Branching Renal artery. Before reaching tlie kidney the renal artery divides

artery.*^^"*^ into four or five pieces ; and these in the sinus break up into

smaller branches, which enter the organ between the papilla?.

They run in the processes of cortical substance that separate the

pyramids, being surrounded by sheaths from the fibrous capsule,

and undergoing farther subdivision, until they reach the bases of

the pyramids. Here the branches form arches, from which the

minute offsets to the secreting structures are given off. Some twigs

are supplied to the capsule of the kidney ; and these anastomose

with the subperitoneal branches of the lumbar arteries.

Vein agrees Renal vein. The larger branches of the vein spring from arches

with artery, jjj^g those of the artery, and take a similar course through the

cortical septa to the sinus. In the neighbourhood of the hilum all

are commonly united into one trunk, which joins the inferior

cava.

Nerves. Nerves. The ramifications of the sympathetic nerve may be traced

to the smaller branches of the artery.

Lymphatics. The absorbents are superficial and deep. Both unite at the hilum

of the kidney, and join the lumbar glands.

Ureter: The URETER is the tube by which the fluid excreted in the kidnej''

office; is conveyed to the bladder. Between its origin and termination

length; the canal measures from fourteen to sixteen inches in length. Its

size varies; size corresponds commonly with that of a large quill. Near the

kidney it is dilated into a funnel-shaped part, named pelvis ; and

near the bladder it is again somewhat enlarged, though the lower

aperture by which it terminates is the narrowest part of the tube ;

but this part of it will be studied later.

course In its course from the kidney to the bladder the ureter is close

beneath the peritoneum, and is directed obliquely downwards and

inwards along the posterior wall of the abdomen to the pelvis. At

ai^d first the ureter is placed over the psoas, inclining on the right side

towards the inferior vena cava ; and about the middle of the muscle

it is crossed by the spermatic vessels. Lower down it lies over the

common or external iliac artery, being beneath the pelvic colon

on the left side, and the end of the ileum on the right side. Lastly,

it inclines forwards below the level of the obliterated hypogastric

artery to reach the base of the bladder.

Occasion- Sometimes the ureter is divided into two for a certain distance,
ally double.

THE SUPRARENAL BODIES. 357

Part in the kidney (fig. 136, h). Near the kidney the ureter is Ureter
dilated into a fimnel-shaped part called the pelvis. It begins in the the^kidney^
sinus of the kidney by a set of cup-shaped tubes, named calices or has calices,
infundihula (c), which vary in number from seven to thirteen. Each which
cup-shaped process embraces the rounded end of a pyramidal ma-'S, p^iuae?
and receives the urine from the apertures in that projection : some-
times a calyx surrounds two or more papillae. The several calices
are united together to form two or three larger tubes ; and these
are finally blended in the pelvis.

Structure. The chief part of the wall of the ureter is composed of Three coats
a muscular coat, in which there is an outer layer of circular, and an ^° ^^ter:
inner layer of longitudinal Hbres. This has an external investment fibrous,
of fibrous tissue, and is lined by mucous membrane. andmucous.

The calices resembles the rest of the duct in having a fibrous, a The calices
muscular, and a mucous coat. Around the base of the papilla the ^(^"g^^^
outer coat of the calyx is continuous with the enveloping tunic of
the kidney ; and at the apex the mucous lining is prolonged into
the uriniferous tubes through the small openings.

Vessels. The arteries are numerous but small, and are furnished Vessels,
by the renal, spermatic, internal iliac, and inferior vesical. The
veins correspond with the arteries.

The lymphatics are received into those of the kidneys. Lymphatics.

THE SUPRARENAL BODIES.

These small bodies (tigs. 134 and 135) have received their name Suprarenal
frou) their position in regard to the kidney. Their vessels and nerves *^*P'''" ®*
are numerous, but they are not provided with any excretory duct.

One body is situate on the upper end of each kidney, with an no duct,
inclination to the inner side, and, without care, may be removed Situation ;
with the surrounding fat, which it resembles. Its colour is a
brownish-yellow. Both bodies are rather triangular in shape, and colour ;
flattened, but with the upper angle rounded oft", and the base or *° ^"^™'
lower part hollowed where they touch the kidney. The right
suprarenal is more definitely triangular than the left, and is often
spoken of as cocked-hat shaped, while the left is larger from above
downwards, and is somewhat pyramidal. They are each somewhat
flattened, and their two surfaces look outwards and forwards, and
backwards and inwards respectively. On the anterior surface of
each is a fissure, termed the hilum, where the vein issues. Hilum.

In the adult they measure about one inch an a half in depth, and Size and
rather less in width ; and the weight of each is between one and two ^^^'^
drachms, but the lelt is commonly larger than the right

Areolar tissue attaches the suprarenal body to the kidney ; and Relations,
the vessels and nerves retain it in place. The relations to surround-
ing parts are much the same as those of the upper end of the kidney.
Thus each rests on the diaphragm, as it clothes the vertebrae on both
sides ; while in front of the right suprarenal is the liver externally, and
the inferior vena cava internally ; and in front of the left the pancreas,
stomach and spleen, from below upwards. On the inner side of the

358

Consists of
two parts,

with a

fibrous

capsule.

Cortical

and

medullary
parts.

Arteries.

Veins.

Nerves.
Lymphatics

DISSECTION OF THE ABDOMEN.

right capsule, beside the vena cava is the solar plexus ; and internal
to the left are the aorta, with the coeliac axis, and the solar plexus.

Obvious structure. A vertical section of a fresh suprarenal body
shows it to be formed of an external or cortical layer, and an
internal or medullary substance. The whole is surrounded by a
thin fibrous capsule, which sends processes into the interior, and
along the blood-vessels.

The cortical part is of a deep yellow colour, and firm. It forms
about two-thirds of the thickness of the whole body, and in the
section appears striated perpendicularly to the free surface of the
organ. The medullary part is dark brown or nearly black, and very
soft and pulpy. If the specimen is not fresh, it may look as if the
cortical part enclosed a cavity.

Blood-vessels. Numerous arteries are furnished to the suprarenal
bodies. Generally there are three vessels, one directly from the
aorta, and one each from the diaphragmatic and renal arteries.
Their small branches penetrate the organ at many spots of its circum-
ference. The veins are for the most part collected into one long
trunk, which issues by the hilum, and opens on the right side into
the vena cava, on the left into the renal vein. Other smaller veins
pass out through the cortex to the renal vein and the vena cava.

Nerves. The nerves are very numerous and large, and come from
the solar plexus.

Lymphatics are superficial and deep ; both join those of the
kidney.

To see the
diaphragm.

Define
arches.

Diaphragm

situation
and form ;

origin at
the circum-
ference :

THE DIAPHRAGM WITH AORTA AND VENA CAVA.

Dissection. The student will now clean, first the diaphragm,
then the large vessels and their branches, and afterwards the deep
muscles of the abdomen. For the dissection of the diaphragm it will
be necessary to remove the peritoneum, defining especially the
central tendinous part, and the strong processes or pillars which are
fixed to the lumbar vertebrae. While cleaning the muscle the
student should be careful of the vessels and nerves on its surface,
and of others in and near the pillars. The right kidney and
suprarenal will be drawn downwards or thrown over to the left in
cleaning the diaphragm, but their vessels should be preserved.

On the right side two aponeurotic bands or arches near the spine,
which give attachment to the muscular fibres, should be dissected ;
one curves over the internal muscle (psoas) ; the other extends over
the external muscle (quadratus lumborum), and will be made more
evident by separating it from the fascia covering the muscle.

The DIAPHRAGM or midrift" (fig. 137, a p. 360) forms the vaulted
movable partition between the thorax and the abdomen. It is
fleshy externally, where it is attached to the surrounding ribs and
the spinal column, and tendinous in the centre.

The origin of the muscle is at the circumference, and is alike on
both sides. Thus, it arises on each side by fleshy slips from tlie inner
surface of the ensiform process and the six lower rib cartilages ; from

THE DIAPHRAGM. 359

two aponeurotic arclies between the last rib and the spinal column, —

one being jDlaced over the quadratus lumborum, and the other over

the psoas muscle ; and, lastly, from the lumbar vertebrae by a thick

muscular piece or pillar. From this extensive origin tbe fibres are

directed inwards, with different degrees of obliquity and length, to insertion of

the central tendon ; but some have a peculiar disposition in the central

pillars which will be afterwards noted. tendon.

The abdominal surface is concave, and is covered for the most Parts in
part by the peritoneum. In contact with it on the right side are the the under
liver, kidney and supra renal ; and on the opposite side, the stomach, surface,
spleen, kidney and supra renal ; in contact also with the pillars are
the pancreas and the solar plexus with the semilunar ganglia. The
thoracic surface is covered by the pleura of each side and the peri- and with
cardium. At the circuuiference the fleshy processes of origin alternate Attachment
with like parts of the transversalis muscle ; but a slight interval of border,
separates the slip arising from the ensiform process from that attached intervals in
to the seventh cartilage, and a second space comes between the fibres ^ ^^^^ ^'
from the last rib and the arch over the quadratus lumborum muscle.
These apertures mark the situation between the three parts of which Apertures,
the diaphragm is essentially formed, viz., sternal, from the ensiform
cartilage, costal, from the costal cartilages, and vertebral, from the
vertebrae and the tendinous arch over the psoas muscle. The
interval between the vertebral and costal parts near the last rib is
occasionally large, and through it a communication between the
abdominal and thoracic cavities may take place and abdominal
viscera be found in the thorax.

Structure. The muscle is convex towards the chest, and concave Vault :
to the abdomen. Its vault reaches higher on the right than the left
side, and is constantly varying during life in respiration. In the
condition of rest, as met with after death (state of expiration), the extent up-
central portion is about opposite the xiphi-sternal articulation ; on ^* ^*
the right side it rises to the level of the fifth, and on the left side to
the sixth chondro- sternal articulation.

Special parts of the diaphragm. The following named parts are Special
now to be noticed more fully, ^dz., the central tendon, the pillars, examined,
the arches, and the apertures.

The central tendon (cordiform tendon) occupies the middle of the Central
diaphragm (fig. 137), and is surrounded by muscular fibres : the " °°'
large vena cava pierces it. It is of a pearly white colour, and its
tendinous fibres cross in difterent directions. In form it is compared
to a trefoil leaf ; of its three lobes or segments the right (c) is the like a trefoil
largest, and the left (a) the smallest. ^ "

The pillars (crura) are two large muscular and tendinous processes Two pillars,
{d and e), one on each side of the abdominal aorta. They are narrow
and tendinous below, where they are attached to the upper lumbar with arch
vertebrae, but large and fleshy above ; and between them is a tendinous ^^^^
arch over the aorta.

In each pillar the fleshy fibres pass upwards and forwards, diverging arrangement
from each other ; the greater number join the central tendon without each

360

DISSECTION OF THE ABDOMEN.

as they
ascend to
tendon :

differences
in the
pillars.

intermixing, but the inner fibres of the two crura cross one another
in the following manner : — Those of the right (e) ascend by the side
of the aorta, and pass to the left of the middle line, decussating with
the fibres of the opposite crus between that vessel and the opening of
the oesophagus. The fibres of the other crus {d) may be traced in
the same way, to form the right half of the oesophageal opening. In
the decussation the fasciculus of fibres from the right crus is generally
larger than, and in front of, that from the left.

The pillars differ somewhat on opposite sides. The rigbt (e) is
the larger of the two, and is fixed by tendinous processes to the
bodies of the first three lumbar vertebrae, and their intervertebral
substances, reaching down to the disc between the third and fourth
vertebrae. The left pillar {d) is situate more on the side of the spine,

Fig. 137. — Under Surface of the DiAtHRAGM.

A. Diaphragm.

B. Psoas magnus.

c. Quadratus lumborum.

a. Left piece of the tendon of the
diaphragm.

b. Middle, and c, right piece.

d. Left, and e. right crus.

/. Inner, and g, outer arched
ligament.

h. Opening for vena cava, i, for
oesophagus, k, for aorta, J, for
splanchnic nerves.

Two arched
ligaments,

internal

and
external.

is partly concealed by the aorta, and does not reach so far as the right
by the depth of a vertebra, and it is even occasionally wanting.

The arches (ligamenta arcuata) are two fibrous bands on each side
over the quadratus lumborum and psoas muscles, which give origin
to fleshy fibres.

The arch over the psoas (lig. arcuat. internum; f) is the stronger,
and is connected by the one end to the tendinous part of the jjillar
of the diaphragm, and by the other to the transverse process of the
first or second lumbar vertebra.

The arch over the quadratas lumborum {lig. arcuat. externum ; g)

ACTION OF THE DIAt^HRAGM. 361

is only a thickened piece of the fascia covering that muscle, and
extends from the first lumbar transverse process to the last rib.

Apertures. There are three large openings ; one each for the aorta, Apertures
the vena cava, and the oesophagus ; with some smaller fissures for
nerves and vessels.

The opening for the aorta (k) is rather behind than in the diaphragm, For the

for it is situate between the pillars of the muscle and the spinal ^^ '

11 -1 1.11 its contents,

column : it transmits the aorta, the thoracic duct, and the large

azygos vein.

The opening for the oesophagus and the pneumo-gastric nerves (i) For gullet
is above and slightly to the left of the aortic aperture : it is placed ^^^ nerves,
in the muscular part of the diaphragm, and is bounded by the fibres
of the pillars as above explained.

The opening for the vena cava (foramen quadratum ; h) is situate For the

between the middle and right divisions of the central tendon ; and

its margins are attached to the vein by tendinous fibres.

There is a fissure ( j) in each pillar for the three splanchnic nerves ; Fissures in
11 1 "^ 1 • 1 1 <• 1 11 • 1 the pillars,

and through that in the left cms the small azygos vein also passes.

Action of the diaphraqm. By the contraction of the muscular fibres Use in

. . 11 • 1 1 . 1 1 • 1 respiration,

in inspiration the tendon, particularly its lateral parts, is moved

downwards, and the arch of the diaphragm lessened. During relaxa-
tion in expiration, the centre of the muscle is elevated, and the
height of the vault increased owing to the elasticity of the lungs, and
the pressure of the viscera below, which are forced upwards by the

action of the abdominal muscles. In forced expiration the muscle Height in

I ore 6(1

reaches as high as the fourth rib on the right side, and the fifth on expiration,
the left, close to the sternum.

In the descent of the diaphragm, the parts of the tendon move Central part
unequally, in consequence of differences in their relations, and in least ;
the length and direction of the fleshy fibres connected with them.
Thus, the central lobe, above which the heart is placed, moves least ;
while the lateral lobes, which are below the lungs descend more
freely. It is estimated that the central lobe of the tendon moves left part
downwards in full inspiration about two-fifths of an inch, the right Average
lobe twice as much, and the left lobe one inch. (Hasse). descent in

,, . , . p . . ' . full inspira-

Iveith IS of opinion that an important part of the action of the tion.
crura, the fibres of which pass into the central part of the tendon,
is to render tense, and depress the attached fibrous pericardium,
and to exercise a pull upon the aorta of the lungs, w^hich are held to
the upper surface of the tendon of the diaphragm by the broad
ligament of the lung.

With the movement of the diaphragm the size of the cavities of Effect on
the abdomen and thorax are altered. By its descent the thorax abdomeT,
is enlarged and the abdomen diminished ; and the viscera in the on viscera,
upper part of the latter canity, viz., liver, stomach and spleen, are
partly moved from beneath the ribs. By its ascent the cavity of
the thorax is lessened, and that of the abdomen is restored to its
former size ; and the displaced viscera return to their usual place. ^^^ ^^
By the contraction of the fibres the aperture for the oesophagus will apertures.

362

Action in-
voluntary.

Take away
greater part
of the
diaphragm.

Clean aorta,
vena cava,
and
branches ;

also iliac

Dissect

muscles ;

psoas and
nerves of
lumbar
plexus,

quadratus
lumborum,

and iliacua.

Bxtent of
abdominal
aorta.

surface
marking.

Relations

DISSECTION OF THE ABDOMEN.

be rendered smaller, and that tube compressed ; but the other
openings for the vena cava and aorta, having tendinous surroundings,
are not materially changed. The possible sphincter action of the
fibres around the a^sophageal opening is most likely to secure
closure of that part against the gastric contents when the
descending diaphragm, in its contraction, presses upon the stomach.

The action of the diaphragm is commonly involuntary, but it is
perfectly under the control of the will.

Dissection. After the diaphragm has been learnt the ribs that
support it on each side may be cut through if tlie thorax has been
sufficiently dissected, and the loose pieces of bone with the fore part
of the diaphragm may be taken away, to facilitate the dissection of
the deeper vessels and muscles. But the posterior third of the
diaphragm, with its pillars and arches, should be left ; and the
vessels ramifying on it should be foUowetl back to their origin.

The large vessels of the abdomen, viz., the aorta and the veua
cava, are to be cleaned by removing the fat, the remains of the
sympathetic plexuses, and the lymphatic glands ; and their branches
are to be followed to the diaphragm, to the right kidney and supra-
renal body, and to the ovary, or to the inguinal canal for the testicle,
as the case may be. In like manner the large iliac branches of the
aorta and cava are to be laid bare as far as Poupart's ligament. The
ureter and the spermatic vessels are to be cleaned as they cross the
iliac artery ; and on the same vessel, near the thigh, branches of a
small nerve (genito-crural) are to be sought.

The muscles are to be laid bare on the left side, but on the right
side the fascia covering them is to be shown.

The psorts muscle, the most internal, lies on the side of the spine,
with the small psoas (if present) superficial to it. On its surface,
and in the fat external to it, the following l)ranches of the lumbar
plexus will be found : — The genito-crural nerve lies on the front.
Four nerves issue at the outer border, — the ilio -hypogastric and
ilio-inguinal near the top, the external cutaneous about the centre,
and the large anterior crural at the lower part (fig. 138 and fig. 140,
p. 373). Along the inner border of the psoas the gangliated cord of
the sympathetic is to be sought, with a chain of lumbar lymphatic
glands ; and lower down the obturator nerve may be recognised
entering the cavity of the pelvis. External to the psoas is the
quadratus lumborum, and crossing the latter near the last rib is the
last dorsal nerve, with an artery. In the hollow of the hip-bone is
the iliacus muscle, which unites below with the large psoas.

The ABDOMINAL AORTA (fig. 138, {b) extends from the lower part
of the last dorsal vertebra to about the middle of the body of the
fourth lumbar vertebra, where it divides into the common iliac
arteries. Its commencement is between the pillars of the diaphragm ;
and its termination is placed opposite a spot below and slightly to
the left of the umbilicus, and nearly on a level with the highest
point of the iliac crest.

The chief relations of the vessel to surrounding parts have been

ABDOMINAL AORTA AND BRANCHES.

Fig. 138. — Deep View of the Muscles, Vessels, and Nerves op the
Abdominal Caa'itt (Illustrations of Dissections).

Muscles and viscera :
A. Diaphragm, with b, internal,
and c, external arched ligament.

D. End of the oesophagus, cut.

E. Small psoas.

F. Large psoas.

G. Quadratus lumborum.
H. Iliacus.

Kidney.
Rectum.

K. Bladder.

Vessels :

a. Diaphragmatic artery.

b. Aorta.

c. Renal.

d. Spermatic.

e. Upper mesenteric, cut.
/. Lower mesenteric.
g. Common iliac, and k, external

k. Deep epigastric artery, cut ; by
its side is the vas deferens, bending
into the pelvis.

I. Deep circumflex iliac.
m. Vena cava.

II. Renal vein.

0. Right spermatic vein.

p. Common iliac vein, and r, ex-
ternal iliac (this letter is put on the
left artery instead of on the vein just
below it).

s. Ureter.

Nerves :

1. Phrenic.

2. II io -hypogastric.

3. Ilio-inguinal.

4. External cutaneous of the thigh.
5 and 6. Geni to-crural.

7. Anterior crural.

iliac artery.

364 DISSECTION OF THE ABDOMEN.

with deep before referred to (p. 320), but some deep vessels in connection
vesse s. with it novv come into view. As the aorta rests on the spine it lies
on the left lumbar veins, which end in the inferior cava. And
between it and the right crus of the diaphragm are the large azygos
vein and the thoracic duct. Along the sides of the vessel are the
lumbar lymphatic glands, from which large vessels run beneath it to
end in the beginning of the thoracic duct.
Place of The BRANCHES of the aorta are numerous, and arise in the following

branches; ^ order : — First, are the diaphragmatic arteries, two in number, which
leave the front of the vessel immediately it appears in the abdomen.
Close to the tendinous ring of the diaphragm, the single trunk of
the coeliac axis arises from the front ; and about a quarter of an
inch lower down, also on the front, the trunk of the superior mesen-
teric artery begins. Half an inch lower, the renal arteries, right and
left, take origin from the sides of the aorta. On the lateral part of
the vessel, close above each renal, is the small suprarenal branch ; and
below the renal is the slender spermatic artery. From the front of
the trunk, one or two inches above the bifurcation, springs the
inferior mesenteric artery. And from the back of the vessel arise
five lumbar arteries on each side, and the middle sacral close above
the bifurcation,
their ciassi- The branches may be classified in two sets, — one to the viscera
fication. ^^ ^YiQ abdomen (visceral), and another to the abdominal wall

(parietal).
Some _ The visceral branches are cceliac axis, superior and inferior mesenteric,

biShes. renal, capsular, and spermatic. Of these, the first three have already

been examined.
Renal artery The reiial arteries (fig. 138, c) leave the aorta nearly at a right
angle, and are directed outwards, one on each side. Near the kidney
each divides into four or five branches, which enter the hilum of
is beneath the organ between the vein and the ureter. Each artery lies
vein , ijeneath its companion vein, being surrounded by a plexus of nerves,
gives off- and supplies small twigs to the suprarenal body {inferior capsular),
■^^^^' to the ureter, and to the fatty layer about the kidney,

difference The arteries of opposite sides have some differences. The left is

leVajfd the shorter, owing to the position of the aorta : the right crosses the
right. spine, and passes beneath the vena cava.

Capsular The middle capsular or suprareneal artery is a small branch which

runs almost transversely outwards to the suprareneal body from

the renal and diaphragmatic arteries. It is of large size in the foetus.

Spermatic The spermatic artery of the testicle (fig. 138, d) is remarkable for

remarkable ; if^ small size in proportion to its length, and for its leaving the

cavity of the abdomen. The part in the abdomen is straight, but

that in the cord is tortuous.

course to From its origin below the renal, the vessel jDasses downwards

*^* *®^^'^^^ ' along the posterior wall of the abdomen to the internal abdominal

ring, where it enters the spermatic cord. In its course beneath the

peritoneum the vessel runs along the front of the psoas, crossing over

the ureter ; and on the right side it passes over the vena cava. It is

BRANCHES OF THE ABDOMINAL AORTA. 365

accorapauied by the spermatic vein, and the spermatic plexus of

nerves. In the foetus before the testicle leaves the abdomen the condition in

spermatic artery is very short, but the vessel elongates as the testis ^ <* "^^ ,

is removed from its original position.

In the female the cor respond in fj artery (ovarian) descends into the in the
1 • . 1 • xi J ^u ^ female,

pelvis to end m the ovary and the uterus.

The parietal branches of the aorta are the diaphragmatic, lumbar, Branches

J . , J, , to wall of

and middle sacral. abdomen.

The diaphragmatic arteries (inferior phrenic ; fig. 138, a) are Inferior
frequently united together at their origin, or with the coeliac ^' ^'^^"^^^ '
axis. They course upwards along the posterior part of the under course of
surface of the diaphragm, the left artery passing behind the nght ;
oesophageal o])ening, and the right behind the vena cava. Each
ends in two branches : — One (internal) passes, onwards towards the distribu-
front of the diaphragm, and anastomoses with its fellow, and with
the superior phrenic and musculo-phrenic branches of the internal
mammary. The other (external) is larger, and is directed outwards to
the side of the muscle, where it communicates with the intercostal
arteries.

Branches. Small oflFsets to the suprarenal body from the external small
division of this artery are named superior capsular. Some twigs are ° "^ *
given by the left artery to the oesophagus, and by the right to the
vena cava.

On the under-surface of the diaphragm are two branches of other
the internal mammary artery of the thorax, one, superior phrenic, diaphragm,
accompanies the phrenic nerve, and ramifies over the middle
of the muscle ; the other, musculo-phrenic, appears opposite the
ninth" cartilage, and supplies the upper costal slips of the
diaphragm.

The other parietal branches of the aorta, viz., lumbar and middle
sacral, are not learnt in this stage : the former will be examined
after the lumbar plexus (}). 374), and the latter in the pelvis (p. 400).

The COMMON ILIAC ARTERY (fig. 138, g) is directed downwards Common
and outwards from the bifurcation of the aorta, and divides into '^'^^ ^'^^'"^ '
two large trunks opposite the fibro-cartilage between the last lumbar extent and
vertebra and the sacrum ; — one of these {external ilia-c) supplies the
lower limb, and the other {internal iliac) enters the pelvis. Placed relations ;
obliquely on the vertebral column, the vessel measures about two
inches in length. It is covered by the peritoneum, and is crossed
by branches of the sympathetic nerve, and sometimes by the ureter.
It is accompanied by a vein of the same name. Usually it does usually no
not furnish any named branch, but it may give origin to the ^""c^®^-
ilio-lumbar artery. On opposite sides the vessels have some
differences.

The right artery has the vena cava to its outer side above, and Differences
near its termination touches the psoas muscle. The companion vein right^*^'^
ijp) is at first beneath, but becomes external to the artery at the
upper part ; and beneath the right artery also is the left common
iliac vein. The left ariery is crossed by the superior haemorrhoidal vessel.

366

DISSECTION OF THE ABDOMEN.

Variations
in length.

External
iliac leads to
lower limb ;

extent and
direction ;

surface
marking.

relations
with parts
around,

with other

vessels,

with nerve,
and veins.

Two named
branches :

unnamed
offsets.

Origin of
branches

occasional
branches.

Veins of the
abdomen,
except vena
portae.

Anatomy of
external
iliac vein :

vessels ; and its companion vein is situate to its inner side. It lies
close to the psoas muscle throughout.

The length of the comraon iliac artery ranges from less than half an inch to
four inches and a half ; but in the majority of instances it varies between one
inch and a half and three inches (R. Quain).

The EXTERNAL ILIAC ARTERY (fig. 138, li) is the first part of the
vessel leading to the lower limb, and is contained in the cavity of
the abdomen. Its extent is from the bifurcation of the common
iliac to the lower border of Poupart's ligament, where it becomes the
common femoral. And its direction would be indicated, on the
surface of the abdomen, by a line from the left of the umbilicus to a
point midway between the symphysis pubis and the anterior superior
iliac spine.

The vessel lies above the brim of the pelvis in its course to
Poupart's ligament, and is covered closely by the peritoneum and
the subperitoneal fat. The right artery is crossed by the lower end
of the ileum, and the left by the pelvic colon. To its outer side
is the psoas, except at its termination under Poupart's ligament,
where it lies over the muscle. A chain of lymphatic glands is
placed along the front and the inner side of the artery.

Close to its origin the artery is often crossed by the ureter ; and
near Poupart's ligament the vas deferens bends down along its
inner side ; while the spermatic vessels, and the genital branch of
the genito-crural nerve lie on it for a short distance.

The external iliac vein (r) is behind the artery above, but
gradually comes forwards and gains its inner side over the pubis.
The circumflex iliac vein crosses it nearly an inch above Poupart's
ligament.

Branches. Two considerable branches, deep epigastric and deep
circumflex iliac, arise about a quarter of an inch from the end of
the artery, and are distributed to the wall of the abdomen (p. 284),

Some small unnamed twigs are given to the psoas muscle and the
lymphatic glands.

Peculiaritiets in branches. The epigastric and circumflex iliac branches may
wander over the lower inch and a half or two inches of the artery. The
obturator artery is often derived from the external iliac, in which case it
generally arises in common with the deep epigastric artery (p. 294.) In
rare cases the internal circumflex artery of the thigh is given off from the
epigastric or the lower part of the external iliac trunk.

Iliac Veins and Vena Cava (fig. 138). The larger veins of the
abdomen correspond so closely with the arteries, both in number,
extent, and relations, as to render unnecessary much detail in their
description. As the veins increase in size from the circumference
towards the centre of the body, those most distant from the heart
will be first referred to.

The external iliac vein (r) is a continuation of the common
femoral vein beneath Poupart's ligament. It has an extent like the
artery of the same name, and ends by uniting with the vein from the
pelvis (internal iliac), to form the common iliac vein. On the pubis

TRIBUTARIES OF INFERIOR VENA CAVA. 367

it is internal to its companion artery, and lies between the psoas and position to
pectineus muscles ; but as it ascends it gradually passes behind the ^^^^'
artery.

The veins opening into it are the epigastric and circumflex iliac tributaries,
and a pubic branch from the obturator vein.

The COMMON ILIAC VEIN {p) ascends by the side of its accompany- Common
ing artery, the right almost vertically, and the left obliquely, to the form «iva:
front of the body of the fifth lumbar vertebra (the right half), where
it blends with its fellow in one trunk — the "\ ena cava.

The right vein is the shorter, and lies at first behind, but after- difference jin
wards outside the artery of the same name. The left is internal to reSons"^
and below the artery of its own side, and crosses beneath the right
common iliac artery to the commencement of the vena cava.

Each vein receives the ilio-lumbar branch ; and the common iliac tributaries,
of the left side is joined by the middle sacral vein.

The INFERIOR or ascending vena cava (m) collects and conveys Vena cava
to the heart the blood of the lower half of the body. Taking origin ^" ^^^^^'
opposite the fifth lumbar vertebra, lower than the bifurcation of the
aorta, this large vein ascends on the right side of the arterial trunk, extent;
and reaches the heart by perforating the diaphragm. Its relations relations;
to surrounding parts have been already noticed (p. 320), but the
description may be again referred to, as the position of the branches
of the aorta to it can be better seen now.

Tributaries. The cava receives parietal branches (lumbar and receives
diaphragmatic) from the wall of the abdomen and the diaphragm ; ™"*^ ®*
and visceral branches from the testicle, the kidney, the suprarenal from
body, and the liver. *^°°*'"'

The veins belonging to the stomach, the intestinal canal, the except those
spleen, and the pancreas, are united to form the vena portse (p. 334) ; apparatus,
and the blood contained in those vessels reaches the cava by the
hepatic veins, after it has circulated through the liver.

The spermatic vein (o) enters the abdomen by the internal Spermatic
abdominal ring, after forming the spermatic plexus in the cord.
At first there are two branches in the abdomen, which lie
on the sides of the spermatic artery ; but these soon join into
one trunk. On the left side it opens into the renal vein at a ends differ-
right angle, and there is generally a small valve over the aperture ; i"ftinT
on the right side it enters the inferior cava below the renal vein. "8^* ^^^^^ >
As the vein a-^cends to its destination, it receives one or more
branches from the wall of the abdomen, and the fat about the branches:
kidney.

In the female the corresponding vein (ovarian) has the same ending vein in the
as in the male, and it forms a plexus in the broad ligament of the * ^"
uterus. Valves are absent from the vein and its branches, but
commonly there is one at its union with the renal.

The renal or emulgent vein (n) is of large size, and joins the vena Renal vein;
cava at a right angle. It commences by many branches in the
kidney ; and the trunk resulting from their union is superficial to position to
the renal arterv. ^^ '

368

DISSECTION OF THE ABDOMEN.

difference on
two sides.

Suprarenal
ends diffe-
rently on
each side.

Hepatic
veins; before
noticed.
Lumbar
veins.

Phrenic
veins.

The right vein is the shorter, and usually joins the cava a little
lower than the other. The left vein crosses the aorta close to the
origin of the superior mesenteric artery ; it receives the left spermatic
and suprarenal veins.

The suprarenal vein is of considerable size when it is compared
with the body from which it comes. The right opens into the cava,
and the left into the renal vein.

The hepatic veins enter the vena cava where it is contact with
the liver. They are described on pp. 348 and 350.

The lunibar veins correspond in number and course with the
arteries of the same name. They will be dissected later.

The diaphragmatic veins (inferior), two with each artery, spring
from the upper surface of the diaphragm. They join the cava either
as one trunk or two.

DEEP MUSCLES OF THE ABDOMEN.

Psoas
magnus :
situation ;
origin from
lumbar
vertebrae :

msertion
into femur ;

relations in
front,

behind,

of outer
border,

of inner
border ;

lumbar

nerves in its
substance ;
use to bend
iip-joint

The deep muscles in the interior of the abdomen are the psoas,
iliacus, and quadratus lumborum.

The PSOAS MAGNUS (fig. 138, F.) reaches from the lumbar vertebrae
to the femur, and is situated in the abdomen and in the thigh.

The muscle arises from the front of the transverse processes of
the lumbar vertebrae, from the bodies and intervertebral discs of
the last dorsal and all the lumbar vertebrae by five fleshy pieces —
each piece being connected with the intervertebral substance and
the borders of two contiguous vertebrae, and from tendinous bands
over the blood-vessels opposite the middle of the vertebrae. The
fibres give rise to a roundish belly, which gradually diminishes
towards Poupart's ligament, and ends below in a tendon on the
outer aspect, which receives also most of the fibres of the iliacus,
and passes beneath Poupart's ligament to be inserted into the small
trochanter of the femur.

The abdominal part of the muscle has the following relations : —
In front are the internal arched ligament of the diaphragm, the
kidney with its vessels and duct, the spermatic vessels and the
genito-crural nerve, and, near Poupart's ligament, the ending of the
external iliac artery : beneath these, the muscle is covered by the
inner part of the iliac fascia. Behind, the muscle is in contact with
the transverse processes of the vertebrae, with the quadratus lum-
borum, and with the hip-bone.

The outer border touches the quadratus and iliacus ; and branches
of the lumbar plexus issue from beneath it. The inner border is
partly connected to the vertebrae, and is partly free along the margin
of the pelvis ; — along the attached part of this border lies the
sympathetic nerve, with the cava on the right, and the aorta on the
left side ; along the free or pelvic part are tlie external iliac vessels.
The nerves of the lumbar plexus lie between the slips of origin from
the transverse processes.

Action. If the femur is free to move it is raised towards the

PSOAS AND ILIAC as MUSCLES.

369

with iliacus,

or to bend
trunk on
the limb.

belly ; and in flexing the hip-joint the psoas is always combined
with the iliacus.

When the lower limbs are tixed the two muscles will draw forwards
the lumbar part of the spine, and bend the hip-joints, as in stooping
to the ground. One muscle under the same circumstances can
incline the spine laterally.

The PSOAS PARVUS (fig. 138, e) is a small inconstant muscle, with
a long tendon, which is placed on the front of the large psoas. Its
fibres arise from the bodies of the last dorsal and first lumbar
vertebrae, with the intervening fibro-cartilage. Its tendon becomes
broader below, and is inserted into the ilio- pectineal eminence and insertion
the brim of the pelvis, joining the iliac fascia.

parvus :
origin ;

OjALf

Rectus femoris

Obliquus abdominis

internus.
Quadratus Inmborum.

Multifidus
spinae.

Coceygeus.
Levator ani.

Erector penis.

Transversus perinei.
Fig. 139.— Os Innominatcm— Inner and Anterior View.

Action. This muscle aids in flexing the lumbar portion of the
spine, either drawing forwards the upper part of the trunk, or raising
the front of the pelvis, according to which end is fixed.

The ILIACUS MUSCLE (fig. 138, h) occupies the iliac fossa on the
inner aspect of the hip-bone, and is blended inferiorly with the
psoas. It is triangular in form, and has a fleshy origin Irom the iliac
fossa (fig. 139), and slightly from the ala of the sacrum and the^^'^'"'
anterior sacro-iliac ligament The fibres pass obliquely inwards to
the tendon of the psoas, uniting with it down to its insertion into the insertion ;

D,A. B B

Iliacus has
the form of
the iliac
fossa :

370

DISSECTION OF THE ABDOMEN.

parts cover-
ing it on
two sides,

beneath it ;

use to bend
hip-joint.

Quadratus
lumborum ;

origin ;

insertion

is contained
in a sheath ;

use of both
muscles,

of one.

Fascia of the
quadratus.

Iliac fascia
covers
ilio-psoas ;

attachments
below,

and above.

femur ; and a few have a separate attachment to the femur below
the small trochanter (fig. 61, p. 158).

Above Poupart's ligament the muscle is covered by the iliac fascia ;
and over the right iliacus are placed the caecum and ascending colon,
over the left, the sigmoid flexure : beneath it is the hip-bone. The
inner margin is overlapped by the psoas ; and the anterior crural
nerve lies between the two. The relations of the united psoas and
iliacus below Poupart's ligament are given with the dissection of the
thigh (p. 167).

Action. The iliacus raises the femur with the psoas when the
limb is moveable, and bends forwards the pelvis when the limb is
fixed.

The psoas and iliacus may be regarded as two heads of one muscle
— the ILIO-PSOAS.

The QUADRATUS LUMBORUM (fig. 138, g) is a short, flattened
muscle between the pelvis and the last rib. About two inches wide
below, it arises from the ilio-lumbar ligament, and from the iliac
crest behind, and for an inch outside that band (fig. 139) ; it generally
receives in addition two or three slips from the transverse processes
of the lower lumbar vertebrae. The fibres ascend to be inserted by
distinct fleshy and tendinous slips into the apices of the transverse
processes of the upper four lumbar vertebrae, and into the lower
border of the last rib for a variable distance.

This muscle is encased in a sheath derived from the fascia
lumborum. Crossing the surface are branches of the lumbar plexus,
together with the last dorsal nerve and its vessels. Behind the
quadratus is the erector spinse muscle.

Action. Both muscles keep straight the spine (one muscle
antagonising the other) ; and by fixing the last rib they aid in the
more complete contraction of the diaphragm.

One muscle will incline laterally the lumbar region of the spine
to the same side, and depress the last rib.

Fascia of the quadratus. Covering the surface of the quadratus is
a thin membrane, derived from the hinder aponeurosis of the trans-
versalis abdominis (anterior layer of the fascia lumborum), which
passes in front of the quadratus to be fixed to the tips and borders
of the lumbar transverse processes, to the ilio-lumbar ligament below,
and to the last rib above. A thickened band of this fascia forms the
external arched ligament, to which the diaphragm is connected.

Iliac fascia. This fascia covers the double flexor of the hip-
joint, and is fixed to the Iwne on each side of the muscle. The
membrane is strongest opposite the pelvis, where it is attached
to the iliac crest on the outer side, and to the brim of the cavity on
the inner side : it receives a strong accession from the tendon of the
psoas parvus when that muscle is present. Over the upper part of
the psoas it becomes thin, and is fixed on the one side to the lumbar
vertebrae ; while on the other it is blended with the fascia over the
quadratus ; and above, it joins the internal arched ligament of the
diaphragm. Its disposition at Poupart's ligament, and the part

SPINAL AND SYMPATHETIC NERVES. 371

that it takes in the formation of the crural sheath, have been before
explained (p. 293).

Dissection. The student is now to remove the right kidney and Trace the
to clean the lymphatic glands lying along the vertebrse, and to trace ^ ^ ^^^'
upwards some lymphatic vessels to the thoracic duct.

To show the origin of the duct, the diaphragm is to be divided
over the aorta, and its pillars are to be thrown to the sides : a piece
may be cut out of the aorta opposite the first lumbar vertebra. The
beginning of the duct (receptaculum chyli), and the lower end of and the
the large azygos vein may be well seen : and the two are to becuS.'and
followed upwards into the thorax.

On the left side the student may trace the splanchnic nerves and splanchnic
the small azygos vein through the pillar of the diaphragm, and
may show the knotted cord of the sympathetic nerve entering the
abdomen beneath the arch over the psoas muscle.

Lymphatic Glands. A chain of glands is placed along the side i^umbar
of the external iliac artery, and along the front and sides of the glands:
lumbar vertebrae ; they are connected by short tubes, which increase
in size and diminish in number, and opposite the first lumbar ducts end in
vertebra form one principal trunk which enters the thoracic duct.
Into the glands the lymphatics of the lower limbs, and those of
some of the viscera and of the wall of the abdomen are received.

Another cluster of large glands surrounds the coeliac axis, and Coeiiac
covers the upper end of the abdominal aorta. They are distinguished ^ ^'^ * •
as the cosliac glands^ and receive the lymphatics of the stomach,
spleen, pancreas, and great part of the liver. Their ducts unite ducts join
with those of the mesenteric glands, and give rise to one or more inte^sUne.™
large trunks, which pass to the common thoracic duct.

Receptaculu3I chyli. The thoracic duct begins in the abdomen Beginningof
by the union of three or four large lymphatic trunks. Its commence- duct,
ment is marked by a dilatation, which is placed on the right side of
the aorta, opposite the first or second lumbar vertebra. The duct
enters the thorax by passing through the diaphragm with the aorta.

THE spinal and SYMPATHETIC NERVES.

The spinal nerves of the loins enter into a plexus, and supply the
limb and the contiguous portions of the trunk.

Dissection (fig. 140, p. 373). The lumbar nerves and their plexus Dissection
are to be learnt on the left side, although the woodcut shows them bar p^iexus'
on the right side ; and to bring them into view, the dissector should on left side,
cut through the external iliac vessel, and afterwards scrape away
the psoas. For the most part the fleshy fibres may be removed
freely ; but a small branch (accessory of the obturator) should be
first looked for at the inner border of the muscle. On, or in the
substance of, the quadratus lumborum a communication' may be
sometimes found between the last dorsal and the first lumbar nerve.

The cord of the sympathetic nerve lies along the edge of the ^ith sym-
psoas, and oftsets of it join the spinal nerves ; these are to be followed
back along the lumbar arteries.

B B 2

372

DISSECTION OF THE ABDOMEN.

Four lumbar
nerves enter
plexus

and supply
muscles :

fifth to the

sacral

plexus.

Plexus how
formed :

situation ;

connections
with nerves.

Six

branches,
viz. :—

Two

cutaneous

branches.

Ilio-hypo-
gastric :

course m
abdomen.

Ilio-inguinal
arises with
preceding,

and accom-
panies it.

Genito-
crural

pierces

and divides
into

genital and

On the right side the psoas is to be left untouched, in order that
the place of emergence from it of the different offsets of the plexus
may he noticed.

Lumbar Spinal Nerves. The anterior primary branches of the
lumbar nerves, five in number, increase in size from above down,
and are joined by filaments of the sympathetic near the interverte-
bral foramina. With the e.xception of the la&t, they enter the
lumbar plexus, having previously given off branches for the supply
of the quadratus lumborum and psoas muscles.

The fifth nerve receives a communicating branch from the
fourth, and is to be followed into the pelvis to its junction with
the sacral plexus. After the two are united, the name lumho-sacral
cord is applied to the common trunk.

The LUMBAR PLEXUS (fig. 140) is formed by the intercommunica-
tion of the first four lumbar nerves. Contained in the substance of
the psoas, near the posterior surface it consists of loops between the
several nerves, and increases in size from above downwards, like the
individual nerves. Superiorly it is sometimes united by a small
branch with the last dorsal nerve ; and inferiorly it joins the sacral
plexus through the large lumbo-sacral cord.

The branches of the plexus are six in number, and supply the lower
part of the abdominal wall and the muscular covering of the sper-
matic cord, the fore and inner parts of the thigh, and the inner side
of the leg.

The first two branches (ilio-hypogastric and ilio-inguinal) end as
cutaneous nerves of the hip, the lower part of the abdomen, the
scrotum, and the thigh.

1. The ilio-hypogastric branch (fig. 140,/) is derived from the first
nerve, and appears at the outer border of the psoas muscle, near the
upper end. It is directed over the quadratus lumborum to the iliac
crest, and enters the wall of the abdomen by piercing the transversalis
muscle. Its termination in the integuments of the buttock and
abdomen, by means of an iliac and a hypogastric branch has been
already mentioned (j^p. 110, 263 and 275).

2. The ilio-inguinal branch (g) arises with the preceding from the
first nerve, and issues from the psoas nearly at the same sjDot. Of
smaller size than the ilio-hypogastric, this branch courses outwards
over the quadratus and iliacus muscles towards the front of the iliac
crest, where it pierces the transversalis. The farther course of the
nerve in the abdominal wall, and its distribution to the scrotum and
the thigh, are before noticed (pp. 264 and 275).

3. The genito-crural nerve (h) is distributed to the cremaster muscle
and the limb. It arises from the second lumbar nerve, and from the
connecting loop between the first two ; issuing from the front of the
psoas, it descends on the surface of the muscle, and divides into
genital and crural branches. Sometimes the nerve is divided in the
psoas, and the branches perforate the muscle separately.

The genital branch descends on the external iliac artery, and
furnishes offsets around it : it passes from the abdomen with the

LUMBAR PLEXUS.

373

spermatic vessels, and is distributed in the cremaster muscle. In
the female the nerve is lost in the round ligament.

The crural branch issues beneath Poupart's ligament to supply the
integument of the thigh
(p. 140).

4, The exteiiial cutaneous
nerve of the thigh (i) arises
from the loop between the
second and third nerves,
and appears about the
middle of the outer border
of the psoas. The nerve
then crosses the iliacus to
the interv'al between the
anterior iliac spinous
processes, and leaves the
abdomen beneath
Poupart's ligament, to
be distributed on the
outer aspect of the limb
(p. 140).

5. The anterior crural
nerve [k) is the largest
offset of the plexus, and
supplies branches mainly
to the extensor muscles
of the knee-joint, and to
the integuments of the
front of the thigh and
inner side of the leg.
Taking origin from the
second, third, and fourth
nerves, this large trunk
appears towards the lower
part of the psoas, where
it lies between that muscle
and the iliacus. It passes
from the abdomen beneath
Poupart's ligament ; but
before the final branching
in the thigh (p. 160), the
nerve sends off the follow-
ing twigs: —

Some small branches to
the iliacus are furnished
from the outer side of the
nerve.

A branch to the femoral
artery, the place of origin

crural
branch.

Course of

external

cutaneous

to the thigh.

Origin of

crural;

Fig. 140. — Dissection of the Lumbar
Plexus and its Branches (Illustra-
tions OF Dissections).

a. External iliac artery, cut across.

b. Thoracic duct.

c. Azygos veins.

Nei'ves :

The figures 1 to 5 mark the trunks of the
five lumbar nerves.
(/. Splanchnic nerves.
e. Last dorsal.
/. Ilio-liypogastric.
g. Ilio- inguinal.
h. Grenito-crural.
i. External cutaneous.
k. Anterior crural.
I. Accessory to obturator.
n. Obturator.
0. Gangliated cord of the sympathetic.

position
in the
abdomen :

its branches

to iliacus,

to femoral
artery.

374

DISSECTION OF THE ABDOMEN.

Obturator
in the
abdomen ;

ends in the
thigh ;

occasionally
an accessory
branch.

Sympathe-
tic cord in
the abdo-
men

joins that
in thorax ;

has four or
five ganglia ;

branches to
the spinal
nerves,

and to the
viscera.

Last dorsal
nerve :

course to
wall of the
abdomen ;

branch to
muscle.

Lumbar
arteries five
in number
on each
side:

of which varies much, is distributed around the upper part of that
vessel.

6. The obturator nerve (n) is distributed chiefly to the abductor
muscles of the thigh (p. 164). Arising in front of the anterior crural
from the second, third, and fourth nerves in the plexus (sometimes
not from the second), it makes its appearance at the inner border of
the psoas near the sacro-iliac articulation. Escaped from beneath the
muscle, the nerve crosses the side of the pelvis below the external
iliac, but above the obturator vessels, and enters the thigh through
the aperture at the top of the thyroid foramen. Occasionally the
the obturator gives origin to the following branch : —

The accesnonj obturator nerve (l) arises from the trunk of the
obturator, or from the third and fourth nerves of the plexus. Its
course is along the inner border of the psoas, beneath the investing
fascia, and over the hip-bone to the thigh, where it ends by joining
the obturator nerve, and supplying the hip-joint (p. 163).

Gangliated cord of the sympathetic (fig. 140, a). The
lumbar part of the gangliated cord of the sympathetic is continuous
with the thoracic part beneath the internal arched ligament of the
diaphragm. It lies on the front of the spinal column, along the
inner border of the psoas muscle, and is somewhat concealed on the
right side by the vena cava, on the left by the aorta. The cord has
four or five oval ganglia, which supply connecting and visceral
branches.

Connecting branches. From each ganglion two small branches are
directed backwards along the centre of the body of the vertebra,
with the lumbar artery ; these unite with one or two spinal nerves
near the intervertebral foramen. The connecting branches are long
in the lumbar region, in consequence of the gangliated cord being
carried forward by the psoas muscle.

Branches of Distribution. Most of the internal branches throw
themselves into the aortic and hypogastric plexuses, and so reach
the viscera indirectly. Some filaments enter the vertebrae and their
connecting ligaments.

Last dorsal nerve (fig. 138, p. 363, and fig. 140, e). The
anterior primary branch of the last dorsal resembles the intercostal
nerves in its distribution, but differs from them in not being con-
tained in an intercostal space. Lying below the last rib, the nerve
is directed outwards across the upper part of the quadratus lumborum,
but beneath the external arched ligament and the fascia of the
quadratus. At the outer border of that muscle it perforates the
middle layer of the fascia lumborum, and enters the wall of the
abdomen, where it ends in an abdominal and a lateral cutaneous
branch (pp. 110 and 274). The first lumbar artery accompanies it.

Near the spine it furnishes a small branch to the quadratus muscle ;
and it may communicate by means of this with the first lumbar
nerve.

The lumbar arteries of the aorta are furnished to the back,
the spinal canal, and the wall of the abdomen : they resemble

THE LUMBAR ARTERIES AND VEINS. 375

the aortic intercostals in their course and distribution. Commonly
five in number on each side, they arise from the back of the aorta,
and the vessels of opposite sides are sometimes joined in a common
trunk. They pass backwards over the hollowed surface of the course ;
bodies of the last dorsal and upper four lumbar vertebrae, and
beneath the pillar of the diaphragm and the psoas, to reach the and termi-
interval between the transverse processes, where each ends in an "^ ^°^ "^
abdominal and a dorsal branch. The arteries of the right side lie
beneath the vena cava.

The po.<iterior or dorsal branches continue to the back between the a branch to
transverse processes, and supply offsets to the muscles and to spinal ^^^ ^^^^'
canal.

The anterior or abdominal branches are directed outwards, and enter and a
the posterior part of the abdominal wall, where they are distributed the'walf°
(p. 283). The first lies with the last dorsal nerve across the front of the
of the quadratus lumborum, but the others usually pass behind that
muscle. Oftsets are furnished to the psoas and quadratus muscles,
and to the subperitoneal fat, and they anastomose with branches of
the renal, capsular, spermatic, right and left colic, and some other
visceral arteries.

The LUMBAR VEINS are the same in number, and have the same The veins
course as the arteries. Commencing by the union of a dorsal and an thef arteries
abdominal branch at the root of the transverse process, each trunk is ^nd open
directed forwards to the vena cava. They open into the back of the into the
cava, either singly, or conjointly with those of the opposite side. On , ~ , '
the left side the veins are longer than on the right, and pass beneath
the aorta.

Around the transverse processes, and beneath the psoas muscles, A plexus
the lumbar veins communicate freely with one another, with the tSn"veie^
ilio-lumbar, and with the common iliac, so as to form a plexus of processes.
veins. Issuing above from the plexus is a branch, the ascending
lumbar vein, which joins the azygos vein of the corresponding side of
the body.

Beginning of the azygos veins. The azygos vein begins on origin of
each side above the first lumbar vertebra by the above-mentioned y^^s*^
ascending lumbar vein ; and it is often joined by a branch of com-
munication with the inferior cava or the renal vein. The right vein entrance
enters the thorax usually with the thoracic duct and the aorta, to the ^" ° ^^^'
right of which it lies. The left vein passes through the pillar of the
diaphragm, or sometimes through the aortic opening.

The anatomy of these veins in the thorax is given at p. 483.

CHAPTER VII.
DISSECTION OF THE PELVIS.

Definition
and situa-
tion.

Boundaries

behind and
before :

below.

Contents.

Section I.

THE CAVITY OF THE PELVIS.

Dissection. For the convenience of examination the pelvis
should now be detached from the rest of the trunk by cutting
through the disc between the third and fourth lumbar vertebral
and severing the soft parts and ligamentous tissues as required.
The lower limbs will already have been removed.

The cavity of the pelvis is the part of the general abdominal
space situate below the brim of the true pelvis.

Boundaries. The space is surrounded b}' the firm ring of the pelvic
bones : it is bounded behind by the sacrum and coccyx, with the pyri-
formes muscles and the sacro-sciatic ligaments ; and laterally and in
front by the hip-bones covered by the internal obturator muscles.

Inferiorly, or towards the perineum, the cavity is limited by the
fascia passing from the wall to the viscera, and by the levatores ani
and coccygei muscles : it is only in this direction, where the
bounding structures are to some extent moveable, that the size of
the space can be appreciably altered.

Contents. In the pelvis are contained the urinary bladder with
the beginning of the urethra, the lower end of the large intestine or
the rectum, and some of the generative organs, according to the
sex. The viscera are supplied with vessels, nerves, and lymphatics ;
and the serous membrane is reflected over them.

The peri-
toneum.

THE PERITONEUM, THE PELVIC FASCIA AND MUSCLES OF THE OUTLET.

Directions. The student will now in a good light make a detailed
examination of the cavity of the pelvis and of its lining peritoneum.

*FosSiE OF THE PELVIS (fig. 141). The pelvic colon terminates
in the rectum at the back of the pelvis opposite the third sacral
verteljra, and at that point the bowel ceases to have a mesentery.
The peritoneum invests the sides and front of the rectum in its
upper third, and then, leaving its sides, continues down the front of
the middle third of the bowel, when leaving it altogether, it is
reflected on to the upper part of the seminal vesicles and thence on
to the upper surface of the bladder in the male, or on to the upper

* For the subjoined description the Editor is much indebted to work of
Dixon and Birmingham.

THE PELVIC PERITONEUM.

377

part of the vagina where it adjoins the uterus and thence along the
back of the uterus in the female.

There is thus produced a deep hollow at the back of the pelvis
wliich is called the recto-genital pouch, or the recto-resical in the male Recto-
and recto-uterine {Douglas's Pouch) in the female. |^uS.

When the bladder and rectum are distended the floor of this

I 1

Q CO
S5 .

a o

2 »

pouch rises and, in moderate distension of both, the reflection of
peritoneum from the rectum on to the seminal vesicles is about
an inch al)ove the prostate and three inches above the anus.

On either side of the rectum is a hollow, occupied in varying Para-rectal

fossa.

378

DISSECTION OF THE PELVIS.

Sacro-
genital fold,

Contains
iinstriped

Middle
fossa.

Para-vesical
fossa.

Transverse
vesical fold.

Distended
bladder.

Bladder in
the child.

False liga.
ments of the
bladder.

Outline of
the fascia of
the pelvis.

Steps to
define the
pelvic
fascia :

in the
pelvis,

degrees by the bowel when distended, which is styled the para-rectal
fossa.

The para-rectal fossa is limited in front by a fold (the sacro-
genital fold) which passes from the front of the sacrum on either side
on to the seminal vesicles or cervix uteri, as the case may be. It is
a strong fold containing fibrous and some unstriped muscular tissue.

In front of and above the sacro-genital fold along the wall
of the f)elvis will be seen a fold produced by the ureter as it passes
downwards to the lateral angles of the bladder. The slight hollow
between the sacro-genital fold and the ureter is spoken of as the
middle fossa of the pelvis.

In front of the ureter is a hollow on either side of the empty
bladder which is appropriately named the para-vesical fossa. In the
male the vas deferens will be seen passing downwards along the side
of the pelvis towards the back of this fossa.

Passing outwards from the upper part of the bladder when empty,
across the pelvic floor on to the side of the pelvis at the fore part of
the para-vesical fossa, is a fold (the transverse vesical fold) which
passes over the brim of the pelvis towards the internal abdominal
ring and often corresponds to the course of the superior vesical artery.

From the summit and upper surface of the bladder the peritoneum
is reflected on to the wall of the pelvis and abdomen leaving the
front and lower part of that organ entirely uncovered by peritoneum.
When the bladder is distended and rises into the abdomen a part
of this uncovered surface is in contact with the anterior abdominal
wall above the pubic bones, and the bladder may be opened through
it without injury to the peritoneum.

It should be pointed out that in the child the bladder is only
accommodated to a small extent in the pelvis and its anterior surface
is in contact with the anterior abdominal wall above the pubis,
having no peritoneal investment in front.

The reflectives of the peritoneum on to the walls of the pelvis
are commonly described as the false ligaments of the bladder, but it
is not a satisfactory terminology. The superior false ligament is the
peritoneum covering the uraches which extends from the summit
of the bladder to the anterior abdominal wall. The lateral false
ligaments are the peritoneal reflections on each side from the bladder
to the pelvic wall ; and the posterior false ligaments are simply the
peritoneal coverings of the sacro-genital folds.

The pelvic fascia. Lining the wall of the pelvis is a thin
fascia (pelvic), which covers the obturator internus and pyriformis
muscles, and sends a process inwards to support the viscera.

Dissection. To bring into view the pelvic fascia, the external
iliac vessels, and the psoas (if this has not been removed in the
dissection of the lumbar plexus), are to be taken away on the left
side of the body. The obturator vessels and nerve are to be cut
through on the same side ; and the peritoneum being detached from
the wall of the pelvis, the fascia will be seen on scraping away with
the handle of the scalpel a quantity of fat. The fascia is strong in
part but is thin towards the back and in this part the student

THE PELVIC FASCIA.

379

should proceed cautiously. By this proceeding the membrane is
dissected in its upper half, or as low as the situation of the portion
(reeto-vesical) which is directed inwards to the viscera.

To display the lower half, the student must raise the outlet of
the pelvis ; and, should the perineum be undissected, the fat must and the
be tixken from the ischio-rectal fossa. The lower part of the pehic i^""^®^"" •

Fig. 142. — Dissection of the Pelvic Fascia (drawn by C. F. Beadles).

uc. Acetabulum.

0 c. Aperture of canal for obturator
vessels aud nerves, bounded below by
0 m. the upper end of the obturator
membrane, the greater part of which
has been taken away. Below these,
the fascia of the obturator intemus
is exposed by the removal of a por-
tion of the bone and the muscle.

** Line along which the recto-
vesical fascia is given off from the
inner side of the obturator fascia.

1 a. Tendinous fibres of origin of

fascia will now appear on the outer side of that fossa, as it covers
the obturator muscle.

To see the outer surface of the fascia (fig. 142), the obturator from outer
externus muscle and the obturator membrane should now be ^* ® '
removed, with the exception of a small portion of the latter at the

the levator ani, showing through the
obturator fascia.

fjn/. Fascia of the pyriformis.

s g n. Superior gluteal nerve.

g a. Gluteal artery.

py. Pyriformis muscle.

f/ s 11. Great sciatic nerve.

s a. Sciatic artery.

p V n. Pudic vessels and nerve,
entering the sheath in the obturator
fascia.

gssl. Great sacro-sciatic ligament.

380

and over
pyriformis.

Pelvic fascia
divided into
three parts,
viz. :—

Obturator
fascia :

attach-
ments ;

relations.

Fascia of
pyriformis.

Recto-
vesical
fascia later.

DISSECTION OF THE PELVIS.

upper end of the thyroid foramen, where it bounds the aperture
through which the vessels and nerve issue. A portion of the bone
is then to be cut out behind the foramen, and extending into the
small sciatic notch, as in the figure ; and the obturator internus
muscle is to be carefully separated from the fascia and taken away.

Lastly, by turning back the pyriformis muscle and the great
sciatic nerve, a thin piece of the fascia covering those structures will
be exposed in the great sacro-sciatic foramen (fj^y)-

The PELVIC FASCIA is a thin membrane which covers the deep
surface of the muscles bounding tlie cavity, and may be described
in three parts. Two of these are parietal and line the wall of the
pelvis, — one covering the obturator internus muscle is named the
obturator fascia, and the other extending over the pyriformis muscle
is the fascia of the pyriformis. The third portion of the fascia is
reflected inwards from the wall of the pelvis on the upper surface
of the levator ani and enters into the formation of the floor of the
pelvis, and supports the rectum and bladder, whence it is known
as the recto-vesical fascia.

The ohturator fascia (fig. 142) invests closely the pelvic portion
of the obturator internus muscle, and is fixed to the bone around
the attachment of the fleshy fibres. Thus, it is attached alcove to
the ilio-pectineal line of the hip-bone between the sacro-iliac articu-
lation and the upper end of the obturator foramen ; at the latter spot
it joins the ol)turator membrane over the edge of the muscle, so as
to form the floor of the canal transmitting the oljturator vessels and
nerve ; and in front it is fixed to the body of the pubis, following
the border of the muscle. Below, it is inserted into the inner side
of the inferior ramus of the pubis, and the ramus and tuberosity of
the ischium in conjunction with the falciform process of the great
sacro-sciatic ligament. Behind, it is fixed to the hip-bone along
the anterior margin of the great sciatic notch ; and between
the ischial spine and the tuberosity, it is united with the great
sacro-sciatic ligament, where the obturator internus issues from the
pelvis.

From the inner surface of this membrane the recto-vesical fascia
is given off, along a curved line extending from the ischial spine to
the upper and inner part of the obturator foramen (fig. 142, * *).
Above this line the obturator fascia bounds the cavity of the pelvis
at the side, and is in contact with the peritoneum ; while below, it
looks into the ischio-rectal fossa, except over a small space in
front, where it is closely united with the pubic origin of the levator
ani {I a).

The fascia of the 'pyriformis (J py) is very thin, and is continued
backwards from the hinder part of the obturator fascia to the sacrum,
passing over the front of the sacral plexus and the pyriformis
muscle, but beneath the internal iliac vessels, by whose gluteal,
sciatic and pudic branches it is perforated.

The recto-vesical fascia may now be seen in part by looking into
the pelvis ; and the student may notice a whitish line extending
from the lower part of the pubis, close to the symphysis, to the

SIDE VIEW OF THE PELVIS. 381

ischial spine. This line corresponds in its hinder part to the origin
of the recto- vesical fascia from the obturator fascia ; but in front,
the levator ani extends upwards between the two laminae of fascia.
The disposition of this part of the fascia will be better seen after
the hip-bone has been taken away.

Dissection. To obtain a side view of the pelvis (fig. 143, p. 382), To remove
it will now be necessary to remove the left hip-bone. The obturator ,' ,
fascia and great sacro-sciatic ligament are first to be detached, and fascia,
then the bone is to be sawn through, about three-quarters of an saw bone,
inch outside the symphysis pubis in front, and at the articulation
with the sacrum behind. After the bone has Ijeen pulled somewhat
away from the rest of the pelvis, the ischial spine, with the recto-
vesical fascia attached to it, may be cut oft" with a bone-forceps ; and
the loose piece of the hip-bone may then be removed by cutting and divide
through the fibres of the iliacus and pyriformis muscles, and any ^^ ^
other structure that may retain it.

A block is afterwards to be placed beneath the pelvis. The Then blow
bladder is to be moderately distended with air through the ureter, "J^ disteiid
and the urethra is to be tied. Some tow is to be introduced into other parts,
the rectimi, also into the vagina if it is a female pelvis ; and a
small piece is to be placed in the pouch of peritoneum between the
bladder and the rectiuu. After the viscera are thus made prominent
without distension, the ischial spine and the recto-vesical fascia
should be raised with hooks, while the levator ani (d) and coccygeus
(c) muscles below it are cleaned.

Parts closing the pelvis below. In addition to the recto- Outlet of

T)6iVlS IS

vesical fascia, the following parts close the pelvic cavity on each closed by
side, between the sacrum and the pubic symphysis.

Behind, the student will meet with the pyriformis passing through pyriformis,
the great sacro-sciatic foramen, with the gluteal vessels and nerve gjus^nd
(fig. 142, g a and sg w) above it. Next comes the coccygeus muscle sacro sciatic
(fig. 143, c) on the small sacro-sciatic ligament, between the ischial
spine and the coccyx ; one border of this muscle is contiguous to the with vessel
pyriformis, the other to the levator ani : and between its upper ^^'^ nenes,
border and the pyriformis lie the great sciatic and pudic nerves,
with some other branches of the sacral plexus, and the sciatic and
pudic vessels. The greater part of the pelvic outlet is closed by by levator
the levator ani (d), which extends forwards from the coccygeus to ^"''
the symphysis pubis. It meets its fellow behind, but the muscles and by
of opposite sides are separated in front by the urethra, with the u^^men^
vagina in the female ; and the interval between them in front is
closed by the triangular ligament of the perineum (h).

The coccYGEDS muscle (fig. 143, c) is flat and triangular, and Coccygeus:

has much tendinous substance mixed with its fibres. It arises from origin ;

the upper part of the inner surface of the iscliial spine (fig. 139,

p. 369), and some fibres are attached to the adjoining part of' the

obturator fascia. Widening as it passes inwards, the muscle is insertion ;

inserted into the side, and the contiguous anterior surface of the

coccyx, and into the side of the lowest piece of the sacrum.

The inner surface looks to the pelvis, and is in contact with the relations of

^ surfaces

382

DISSBCnON OF THE PELVIS.

rectum : the opposite surface is in great part covered by the small

sacro-sciatic ligament, to which it is closely united. The upper
and borders; border is contiguous to the pyriformis muscle, vessels and nerves

intervening ; and the lower meets the levator ani.
use. Action. This muscle helps the levator ani in supporting and

raising the floor of the pelvis : it may also draw the coccyx slightly

forwards.

The LEVATOR ANI (fig. 143, D, also fig. 92, p. 241) is a thin

flat muscle, which is attached above to the side of the pelvis, and

descends into the outlet of the cavity, where it joins its fellow and

supports the viscera.

Levator
ani :

situation

-Side View op the Muscles in the Outlet of the Pelvis
(Illustrations of Dissections).

Muscles :

A. Gluteus maximus, cut.

B. Ilio-psoas, cut.
c. Coccygeus.

D. Levator ani.

E. External sphincter.

F. Ejaculator urinse.

G. Ischial spine, cut off.
H. Triangular ligament.

Arteries :
a. Externa] iliac artery, cut.

h. External iliac vein, cut.

c. Obliterated hypogastric.

d. Upper, and e, lower vesical.
/. Internal pudic.

Nerves :

1. Great sciatic.

2. Inferior hgemorrhoidal and peri-
neal of pudic.

3. Dorsal nerve of penis.

origin from
pubis,

triangular
ligament,

ischial
spine,

and pelvic
fascia ;

insertion
into central
point of
perineum,

It arises anteriorly by tendinous fasciculi from the back of the
pubis along an oblique line in front of the obturator internus (fig. 139);
and below this some fleshy fibres often spring from the upper surface of
the triangular ligament. Posteriorly it is attached to the lower and
inner part of the ischial spine (fig. 139) ; and between these osseous
attachments the muscle takes origin in the angle between the obtura-
tor and recto- vesical portions of the pelvic fascia (along the curved
line -^ * in fig. 142). From this wide origin the fibres converge,
the anterior being directed backwards, and the posterior downwards
and inwards, to be inserted in the following manner : — The most

RECTO-VESICAL FASCIA. 383

anterior fibres, few in number, join with the muscle of the opposite

side in the central point of the perineum ; the succeeding fibres,

which arise from the pubis, are the longest, and pass backwards

over the prostate to the side of the rectum, where they mix to a rectum,

small extent witli the fibres of the sphincter muscles, but most of

them are continued to the tip of the coccyx (jmbo-coccygeus) ; and

the posterior fibres meet the opposite muscle in a narrow aponeurosis a median

behind the gut, and are attached in part to the side of the coccyx •^1^°'^^^°*^*''
, . , . '^^ \ ^ and coccyx ;

{ischio- coccyyeus) .

The anterior fibres of the levator are in contact with the trian- relations of
gular ligament ; and there is an interval between the two muscles ^ ^^'''
which allows the urethra, with the vagina in the female, to pass
from the pelvis. The posterior border is adjacent to the coccygeus
muscle. The upper surface is in contact with the recto-vesical a'^d
fascia ; and the under surface looks to the ischio-rectal fossa, and is "
covered by the thin anal fascia.

Action. The levatores ani acting together support and raise the use,
floor of the pelvis, and compress the pelvic viscera. They are used ^^ "^
in expelling the contents of the organs, and, in forcible expiratory on cavity of
efforts, they act in conjunction with the muscles of the abdominal ^Wo"^*'"'
wall. At the end of defsecation, they empty the lower part of the °" ^^^ ""'
rectum, compressing it from behind forwards ; and the lower fibres
assist in closing the anal passage. The levatores ani and coccygei
muscles form a fleshy layer or pelvic diaphragm across the outlet of Pelvic
the pelvis, similar to that which separates the abdomen from the '^^ ^s^-
chest : this partition is convex below and concave above, and gives
passage to the rectum.

Dissection. The recto-vesical fascia will now be seen by Dissection
detaching the fibres of the levator ani and the coccygeus at their ^°siS^°*
origin, and throwing both downwards. The thin membrane fascia,
descends above the levator ani to the side of the bladder and the
rectum, and sends downwards sheaths round the prostate and the
gut. To demonstrate those sheaths, one incision is to be made
along the prostate, and another along the lower end of the rectum,
below the attachment of the fascia ; and the sheaths are to be
separated from the viscera.

The RECTO-VESICAL FASCIA supports and partly invests the viscera Recto-vesi-

of the pelvis. Covering the pelvic surface of the levator ani, it is ^^ ^*^^^* *

fixed above, like that muscle, to the pubis in front, and to the ^^^'

obturator fascia at the side ; while behind, it is continued over the

coccygeus muscle into the fascia of the pyriformis. Below, it meets

the fascia of the opposite side in the centre of the pelvis, and forms forms the

a partition across the cavity, like that of the levator ani, which is the peUis ;

perforated by the bladder and the rectum. The partition is

strengthened on each side by a thicker band (the so-called white line

of the pelvic fascia) stretching from the pubis to the ischial spine.

It is concave above and convex below, and divides the cavity supports

of the pelvis from the perineal space. This septum is attached to '

the viscera which pierce it, forming ligaments for them : and from the

under surface sheaths are prolonged on the rectiun and the prostate, proionga-

° tions are,

H84

DISSECTION OF THE PELVIS.

sheath on
the rectum.

and on
prostate.

The pros-
tate ijlexus.

Fascia in
the female.

Ligaments
of the fascia;

anterior
ligaments,

The sheath on the rectum encloses the lower three inches of the
intestine, and gradually becomes very thin towards the anus ; it is
separated from the intestine by a layer of fat.

On the prostate the sheath is thinner than on the rectum, and
very closely adherent ; it is continued downwards to the apex of
that body, where it passes into the upper layer of the triangular
ligament of the urethra : between it and the proper investing
capsule of the prostate are the p'ostate 'plexus of veins and some
small arteries.

In the female the fascia has much the same arrangement as in
the male ; but the vagina perforates the membrane, and receives a
tube from it, like the prostate.

The true ligaments of the bladder are two on each side, anterior
and lateral, and are portions of the recto-vesical fascia.

The anterior (or pubo-prostatic) reaches from the back of the pubis
to the fore part of the prostate and the neck of the bladder ; it is a

and lateral
of the
bladder :

ligament of
rectum.

The lateral ligament is the side piece of the fascia, which is fixed
to the upper border of the prostate gland, and to the side of the
bladder close above the vesicula seminalis ; from it an offset is
continued inwards behind the vesicula seminalis, so as to join a like
piece from the other side, and form a sheath for those bodies.

On each side of the rectum is a strong wide piece of the recto-
vesical fascia, which is attached externally to the ischial spine of
the hip-bone, and supports that viscus like the bladder.

Contents of
the pelvis,

and outline
of their
position.

Take away
fascia, and
clean
vessels.

RELATIONS OF THE VISCERA IN THE MALE.

Directions. If the student dissects a female pelvis, he will pass
on to page 390 referring to this section for the description of the
rectum, bladder and other parts.

Contents and position (figs. 144 and 145). The viscera of the male
pelvis are — the rectum, the bladder with the prostate and first part
of the urethra, the lower ends of the ureters, parts of the vasa
deferentia, and the vesiculse semi n ales.

The rectum (fig. 145, k) lies at the back of the pelvis, and takes a
curved course in the hollow of the sacrum and coccyx, round the end
of which it bends backwards as the anal canal (Symington). The
bladder (a) is placed in the concavity of the rectum, its neck being
surrounded by the prostate gland (6) ; and the urethra, after per-
forating the prostate, curves forwards to the penis. The ureter Qi)
descends by the side of the rectum to the lateral angle at the
hinder part of the bladder on each side ; and the vas deferens (/)
and vesicula seminalis (g) are between the bladder and rectum on
each side. Some of these organs are partly invested by peritoneum,
as already described.

Dissection, All the recto-vesical fascia, except the anterior true
ligament of the bladder, may be taken from the prostate and rectum.
The obliterated hypogastric cord from the internal iliac artery
should be followed forwards along the bladder from the back of the
pelvis ; and the branches of the same artery to the bladder should

MALE PELVIS.

385

be cleaned. "Wlien the fat lias been cleared from the rectuni, with-
out injuring its arteries, the pouch of the peritoneum, in which tow

Fig. 144. — ^Vertical Section op a Male Pelvis (Dixon and Birmingham).

(From the Journal op Anatomy and Physiology, Vol.
Vesical arteries. e. Gluteal artery.

Obturator artery.
Inferior vesical artery.
Mid. haemorrhoidal artery.

/. Int. pudic artery.
g. Sciatic artery.

has been placed, will be brought into view, with the ureter
pa.ssing to the bladder across its side.

The bladder below the peritoneum is to be cleaned ; and the vas The several
deferens is to be followed down to the seminal sac. Take away to be

D.A.

cleaned.

386

DISSECTION OF THE PELVIS.

Rectum ;
extent and
length ;

course and
supports ;

Covered by
peritoneum ;

with care the remains of the sheath of the vesicula seminalis,
defining at the same time the vas deferens internal to the latter.

The KECTUM, or last ytSivt of the great intestine (figs. 144 and
145, k), extends from the third piece of the sacrum at the termina-
tion of the pelvic colon to a little more than an inch in front of
the tip of the coccyx where it Lends downwards and backwards as
the anal canal. It is about five inches in length. The bowel
follows the curve of the sacrum and the coccyx, and is supported
mainly by the peritoneum, the recto-vesical fascia, and the perineal
muscles.

It lies behind the bladder, and is covered by peritoneum in front

Fig. 145. — Side View of thk Dissected Male Pelvis.

a. Urinary bladder partly filled.

b. Prostate.

c. Membranous part of the ui-ethra.

d. Spongy part of the urethra.

e. Crus penis, divided.

f. Vas deferens.

g. Vesicula seminalis.

h. Ureter.

i. Recto-vesical fascia.

k. Rectum.

I. Levator ani, cut.

relations.

Part not
covered by

for about the upper two-thirds of its extent, and on the sides for
its upper third only (p. 376). Immediately below this it i3ierces
the recto-vesical fascia, and receives its sheath from that membrane.
Eesting on it is the triangular base of the bladder, with the vesiculae
seminales and vasa deferentia ; and beneath it are the sacrum and
coccyx. On each side is the coccygeus muscle.

After the iDeritoneum leaves it, the rectum is directed down-

peritoneum ; wards and forwards from the end of the coccyx, through the hinder
part of the perineum, for a distance of about one inch and a half.

URINARY BLADDER. 387

to the anal passage. This part of the bowel is supported by the
triangular ligament of the urethra, and by the levatores ani and
external sphincter muscles.

In front of this part are the prostate, the membranous part of the relations
urethra, and the bulb of the corpus spongiosum urethrse. The aroundh^
levatores ani muscles descend on its sides, and unite beneath it,
supporting it as in a sling. Sometimes the lower half of the rectum sometime.s
is very much enlarged, especially in women and old men ; and in dilated,
that condition in the male it rises up on each side of the prostate.

The anal passage or canal (Symington) leads downwards and Anal canal,
backwards from the lower end of the rectum to the anal opening.
Its length varies from half an inch to one inch, being shorter when
the bowel is distended. It is suiTounded by the internal and
external sphincter muscles, and is compressed laterally in the
intervals between defsecation, so that its side-walls are in contact,
and the lumen has the form of a median slit.

The URINARY BLADDER (vesica urinaria; figs. 144 and 145, a) Bladder is
is the receptacle for the urine, and is situate in the fore part of the '^heiiemptv
pelvis.

When the bladder is contracted it is flattened, and of a triangular
form, and lies against the anterior wall of the pelvis ; but when
distended it becomes rather egg-shaped, with the larger part and projects
towards the rectum, and the apex to the abdominal wall. In^]®^^^"
distension during life it is slightly curved forwards over the pubic
bones, and projects above them ; and if its axis were prolonged Axis,
forwards and backwards, it would touch the abdominal wall a variable
distance (according to the distension) above the pubic symphysis
in front, and the lower end of the sacrum behind.

The position and form of the bladder are not the same in Position in
early life as in the adult. In the new-born child it rises much ^^^ ci"id,
above the brim of the pelvis into the hypogastric region of the
abdomen, and has little or no basal surface, simply tapering down
to the urethral orifice which is the lowest part and is opposite the
upper border of the symphysis pubic (Symington). During early
years the bladder rapidly sinks, but it is only after puberty that
its final position is attained. At all times its anterior surface is
uncovered by peritoneum.

In the adult the bladder is for the most part contained within in the adult,
the space enclosed by the pelvic bones, and the base projects
backwards.

Form. In the empty condition the bladder is somewhat flattened Form,
from above downwards, and triangular in outline, presenting an
wpper surface with a posterior border and two lateral borders
converging in front at the apex or summit, a basal surface
opposed to the rectum, and an anterior surface opposed to the pul)ic
symphysis.

The organ is maintained in position by the recto-vesical fascia

and the peritoneum, as already described (pp. 378 and 384).

The relations of the moderately full bladder are as follows : —

The summit or apex is rounded, and from it three ligamentous Apex has
^ three cords

C C 2 from it.

388

DISSECTION OF THE PELVIS.

Basal
surface.

superior

and lateral.

Neck,

Condition
of empty
bladder.

Ureter in
pelvis,

enters
bladder.

Prostate :
position ;
form :

relations of

surface,

I^osterior
surface,

and side ;

apex and
base;

cords are prolonged to the umbilicus ; the central one of these is
the urachus ; and the two lateral are the obliterated hypogastric
arteries (fig. 109, p. 299). All the surface behind the obliterated
vessels is covered by peritoneum.

Surfaces. The base or basal surface rests against the middle part
of the rectum. Connected with it are the vesiculae seminales
and the vasa deferentia ; and between these is a triangular s;pace,
from which the peritoneum is mostly absent.

The anterior or jpuhic surface of the body is in contact with the
pubic bones and anterior true ligament?, as well as with the
abdominal wall if the bladder is very full. It is altogether free
from peritoneum.

The superior or abdominal surface is entirely covered by the
serous membrane, and has the small intestine and the pelvic colon
resting on it ; the ureter enters its postero-lateral angle at either
side, and the vas deferens courses over the hinder part of this
surface beneath the peritoneum.

Extending along the upper part of each lateral region is the
obliterated hypogastric artery, which marks the extent of the
peritoneal covering at the side. The surface below this is connected
with the pelvic fascia by very loose areolar tissue.

The neck (cervix) is the part of the bladder near the urethra, and
is surrounded by the prostate gland. This is the lowest part of the
organ.

When the bladder is empty, the upper wall falls upon the
lower ; the apex lies at the upper end of the pubic symphysis ;
and the base is of very small extent and looks downwards. In a
median section the cavity then appears as a slit, which is continued
backwards for a short distance beyond the beginning of the urethra.

The URETER (figs. 144 and 145, h) crosses the common or the
external iliac artery, and inclines forwards below the level of the
obliterated hypogastric artery, being covered by the peritoneum
above the sacro-genital fold. It enters the bladder at the upper
and outer part of the base, at the distance of one inch and a half or
two inches from the prostate gland.

The PROSTATE GLAND (figs. 144 and 145, b) surrounds the neck
of the bladder. Its shape is conical with the base turned upwards,
and its size about equals that of a large chestnut. In the
recumbent position, a line from the apex through the middle of
the gland would be directed obliquely backwards and slightly
downwards towards the sacrum ; but in the erect state of the body
the axis is nearly vertical.

The anterior surface is about three-quarters of an inch from the
symphysis pubis, to which it is attached by the anterior true
ligaments of the bladder. On this surface the dorsal vein of the
penis divides to enter the prostatic plexus. The posterior surface
has the greatest extent, and is close to the rectum ; this is the part
that is felt by the finger introduced into the bowel through the
anus. On each side the prostate is covered by the levator ani.

The apex rests on the upper surface of the triangidar ligament ;

THE URETHRA. 389

and the ba~^ siirrounrls the neck of the bladder and the common
seminal ducts.

The prostate is enveloped by a sheath obtained from the recto- itiscou-
vesical fascia (p. 349), and the prostatic plexus of veins surrounds sheath^*
it. Through the gland the urethra takes its course to the perineum ;
and the common seminal ducts pierce it obliquely to open into the
urethra, as will be seen in the examination of the organ after its
removal from the body. The size of the prostate varies much ; size may
and in old men it may acquire a considerable magnitude. increase.

The VESICUL.B SEMiNALES (fig. 145, g) are two small sacculated Seminal
bodies, each about two inches long, between the base of the bladder '^®'^^<^1®® *
and the rectum. Each is pyramidal in form, and has the larger their
end turned upwards towards the ureter, while the smaller touches relations,
the prostate. Along the inner side is the vas deferens. At the
prostate gland the vesicidas approach one another, only the vasa
deferentia intervening ; but higher up they diverge, and enclose a
triangular space at the base of the bladder. The vesicnlae are and sheath,
contained in a membranous sheath, which is derived from the
recto-vesical fascia, and is lined 1)y involuntary muscular fibres.

The VAS DEFERENS, or the excretory duct of the testis (figs. 144 Vas
and 145,/), in its course to the urethra enters the abdomen by the ^®'^'*^'
internal abdominal ring, and crossing the obliterated hypogastric
artery, is directed downwards along the hinder part of the bladder
to the base of the prostate, where it forms the common seminal or course ;
ejaculatory duct by joining with the duct from the vesicula unites with
seniinalis. The position of this tube to the external iliac artery vesicula.™
has been noticed ; on the bladder it passes internal to the ureter
and the vesicula of the same side. By the side of the vesicula the
duct is much enlarged, and is sacculated.

Dissection. The prostate being cleaned the membranous and
spongy parts of the urethra will now be cleanly laid bare on the
left side but not opened.

The URETHRA is the excretory passage for the urine and semen Urethra:
(fig. 144), and reaches from the bladder to the end of the penis.
In length it measures about eight inches, and presents one or two length ;
curves according to the state of the penis. At first the canal is curves ;
directed doMTiwards and forwards through the triangular ligament
of the perineum to the root of the penis, forming a large curve with
the concavity to the pubis. Thence to its termination the urethra
is contained in the penis ; and while this body remains pendent
the canal forms a second bend with the concavity downwards ; but
if the penis is raised the tube makes but one curve. The canal is division,
divided into three parts — prostatic, membranous, and spongy.

The prostatic part (b) is contained in the prostate gland. Its Prostatic,
length is about one inch and a quarter, and in the erect posture of
the body it descends nearly vertically to the triangular ligament.

The memhranous part (c), about three-quarters of an inch long, Mem-
intervenes between the apex of the prostate and the lower surface ^"^""^-^ •
of the triangular ligament. It slants forwards in the erect posture
to the lower part of the triangidar ligament ; and as the l)ulb of

390 DISSECTION OF THE PELVIS.

the next portion of tlie urethral tube is directed backwards below
it, its under surface measures only half an inch.

relations. This portion of the urethra is the weakest ; but it is supported

by the triangular ligament {n). Surrounding it are the muscular
fibres of the constrictor urethrse ; and close behind it are Cowper's
glands and the rectum.

Spongy. The spongy part (d) is so named from its being surrounded by a

cellulo-vascular structure. It is applied to and assists to form the
body of the penis, and the canal terminates anteriorly in the orifice
named the meatus urinarius at the end of the glans. It is the longest
part of the urethra, and measures about six inches. At its com-
mencement this division of the excretory canal is covered by the
ejaculator urinse muscle.

The fixed curve of the urethra is the l)end at the hinder part of
the canal as it lies behind the pubis. It extends from the bladder
to an inch and a half in front of the aperture in the triangular
ligament, and comprises the prostatic and membranous portions,
with a fourth of the spongy part. Its convexity, which is turned
downwards and backwards, is greatest immediately below the
triangular ligament in the erect posture of the body ; and from this
point it ascends to the bladder, but is directed nearly horizontally
forwards to the penis.

It is surrounded by voluntary and involuntary muscular fibres ;
thus, above the ligament, by the involuntary muscular tissue of the
prostate ; within the ligament by the voluntary constrictor urethrse,
with a thin involuntary layer inside that muscle ; and below the
ligament by the voluntary ejaculator urinae.

Size. The size of the canal is least where the tube lies between the layers

of the ligament, except at the external urinary meatus ; and it is
largest in the middle of the prostate.

Fixed curve
of urethra :

extent :

where
greatest.

Voluntary
and invo-
luntary
muscles
surround it.

Contents of
the female
pelvis,

and their
situation.

The peri-
toneum on
the uterus ;

RELATIONS OF THE VISCERA IN THE FEMALE.

In the pelvis of the female are contained the rectum and the
bladder, with the ureters and urethra, as in the male ; but there
art in addition the uterus with its accessories, and the vagina.

Position. The rectum is posterior to the rest as in the male pelvis,
and forms a like curve. In the concavity of the bent intestine lie
the uterus with its appendages, and the tube of the vagina. And
in front of all are the bladder and the urethra. There are thus
three tubes connected with the viscera in this sex, viz., the urethra,
the vagina, and the rectum ; and all are directed downwards to the
surface.

The Peritoneum. The student should first master the descrij)-
tion of the peritoneum of the pelvic cavity contained on pages
376 to 378.

In addition to what has already been described it will be noticed
that whilst the peritoneum covers the whole of the l)ack of the
uterus it only passes some two-thirds of the way down its anterior
surface and is then reflected on to the upper surface of the bladder
without again touching the vagina.

THE BROAD LIGAMENT.

On each side of the uterus it forms a broad fold {broad ligament)
which attaches that organ to the wall of the pelvis.

The bladder in distension rises and occupies the shallow utero-
resical pouch in front of the uterus ; and the deep recto-uterim or

391

Recto-genital fossa. Sacro-genital fold.
Fig. 146. — Vesical Section through the Female Pelvis (Dixon and
Birmingham). (From the Journal of Anatomy and Physiology, Vol. 36.)

Douglas's pouch behind is variously occupied by the pelvic colon
and coils of the small intestine.

The BROAD LIGAMENT of the uterus passing from the side of the the broad
uterus to the pelvic wall completes the division of the pelvic cavity 'S*™®" •
of the female into these two main parts, Along the upper border
of the ligament the Fallopian tube will be noticed, and at the
back, against the side wall of the pelvis, the ovary will be
found.. The part of the ligament below the Fallopian tube

392

DISSECTION OF THE PELVIS.

salpenic.

Meso-
ovarium ;

ligament of
the ovary ;

ovario-
pelvic
ligament ;

round liga-
ment.

Use descrip-
tion of male
pelvis for
muscles and
fasciae.

Then clean
the viscera
of the
female
pelvis.

Relations
of the rec-
tum,

and anal
canal.

Uterus :

form and
situation ;

and above the ovary is called the mesosalpinx and the short fold
attaching the ovary is the meso-ovarium. Passing from the lower
and inner end of the ovary to the upper part of the uterus behind
is a well-marked band — the ligament of the ovary ; and a fold con-
taining the ovarian vessels will be seen connecting the ovary to the
pelvic wall over the external iliac artery ; this is the ovario -pelvic
ligament^ or the suspensory ligament of the ovary.

Finally in front of the broad ligament a fibrous cord — the round
ligament of the nterus — can be traced from the uterus over the pelvic
brim to the internal abdominal ring.

The false ligaments of the bladder are substantially the same as in
the male (p. 378). The so-called posterior false ligament is
identical with the utero-vesical fold of peritoneum and contains
the superior vesical vessels.

Directions. The instructions for the removal of the hip-bone,
and for the distension of the viscera, as well as for the dissection of
the fascia and muscles of the pelvis given on page 378 should now
be followed, and after the student has learnt the muscles and the
fascia, which are nearly alike in both sexes, as described on pages
380 to 384, he will make the following special dissection of the
viscera of the female pelvis.

Dissection. On taking away the recto- vesical fascia and much
fat the viscera will come into view. To maintain the position of
the uterus, fasten it up with a piece of string passed through the
upper end. The reflections of the peritoneum on the viscera are to
be preserved ; and a piece of cotton- wool is to be placed between the
rectum and the uterus.

The obliterated cord of the hypogastric artery is to be followed
on the bladder ; and the ureter is to be traced forwards by the side
of the uterus to the bladder. Afterwards the urethra, the vagina,
and the rectum are to be cleaned and separated a little from one
another at the lower part of the pelvis ; but the arteries on the
rectum are to be preserved.

The RECTUM is not so curved in the female as in the male, and
is generally larger. Descending along the front of the sacrum and
coccyx to the anus, its relations are similar to those of the rectum
in the male (p. 386).

It reaches an inch and a half in front of the tip of the coccyx,
and has the vagina in front, and in contact with it ; the connection
between the two being considerably stronger below than above.

Inferiorly it ends in the anal canal, which inclines backwards,
away from the vagina so as to leave between the two a space which
corresponds, on the surface of the body, with the perineum between
the anus and the vulva. The levatores ani are on the sides, and
unite behind the rectum in front of the coccyx, and the sphincter
muscles surround the anal passage as in the male.

The UTERUS (fig. 146 and fig. 147, o) is rather pyriformin shape,
and flattened from 1:)efore backwards. Unless enlarged, it lies
below the brim of the pelvis, between the bladder and the rectum ;
and it is supported by its ligaments. Its wider end is free and

THE UTERUS;

393

placed upwards ; and the lower end communicates with the
vagina.

The axis of the uterus may be said to correspond generally with position and
that of the inlet of the pelvis ; but the position of the organ is sub- v^y j'°"
ject to considerable variation, and is especially influenced by the
stat« of the 1>ladder. The fundus is commonly directed forwards,
and the anterior surface rests against the bladder ; but sometimes
the organ is more upright, or even inclined backwards, and then
the small intestine descends into the vesico-uterine pouch.

Fig. 147.— Side View of

.i^i.

. ..MALK Pelvis (Illustrations of

Dissections).

Muscles and Viscera:

N. Round ligament.

A. Pyriformis muscle, cut.

0. Uterus.

B. Large psoas, cut.

c. Gluteus maximus, cut.

Arteries:

D. Coccygeus, aud e, levator

ani,

a. External iliac.

thrown down.

b. Internal iliac.

F. Sphincter vaginae.

c. Ovarian.

G. Urethra.

d. Uterine.

H. Urinary bladder.

e. Vaginal.

I. Vagina.

/. Upper haemorrhoidal.

K. Rectum.

ff. Gluteal, cut.

L. Ovary and its ligament.

h. Obliterated hypogastric.

M. Fallopian tube.

i. Vesical.

The anterior surface, somewhat flattened, is covered by jDeritoneum, relations of
except in the lower third where it is in contact with the bladder, ^'^^'faces,
The posterior surface is rounded and is invested altogether by the
serous membrane.

The upper end or fundus is the largest part of the organ and is in extremities
contact with the small intestine. The lower end or neck (cervix) is
received into the vagina.

394

DISSECTION OF THE PELVIS.

and side.

Round
ligament.

Fallopian
tube.

Ovary,

and its
ligament.

Vagina :
extent and
form ;

length ;
axis;

relations.

Bladder

resembles
that of the
male;

differences
in the two
sexes.

To each side are attached the broad ligament with the Fallopian
tube, the round ligament, and the ovary.

The round or suspensory ligament (n) is a fibrous cord al)Out five
inches long which is directed forwards and outwards to the internal
abdominal ring, and then through the inguinal canal to end in the
groin (see p. 277). This cord lies over the obliterated hypogastric,
and the external iliac artery ; and it is surrounded by the
peritoneum, which accompanies it a short way into the canal.

The Fallopian tube (m),. about four inches long, is contained in
the upper or free border of the broad ligament. One end is con-
nected to the uterus close to the fundus, while the other is folded
round the ovary. At the uterine end the tube is of small size, but
at the op]5osite extremity it is dilated like a trumpet, and fringed
(fig. 146), forming the corpus fimbriatuin : one of the fimbriae is
attached to the upper part of the ovary.

The OVARY (l) is oval in form, but rather flattened, and very
variable in size. It forms a projection at the back of the broad
ligament, and is invested by the peritoneum except along one (the
attached) border. In the natural condition it lies nearly vertically
against the side wall of the pelvis, and is embraced by the outer
part of the Fallopian tube : the direction of its free border varies.
Its lower end, which is directed somewhat forwards, is attached to
the uterus by the special fibrous band already noticed, about one
inch and a half in length, the ligament of the ovary.

The VAGINA (fig. 146 and fig. 147, i) is the tube by which the
uterus communicates with the exterior of the body. It is com-
pressed from before backwards, being slit-like in section from vside
to side ; and its length is about three inches. As it follows the
bend of the rectum, it is slightly curved ; and its axis corresponds
below with that of the outlet, but higher up with that of the cavity
of the pelvis.

In front of the vagina are the base of the bladder, and the
urethra ; and behind it is the rectum, but the peritoneum inter-
venes between the two for a short distance at the upper end. It is
transmitted through an opening in the recto-vesical fascia, which
sends a sheath along the lower half of the tube ; and the levator ani
lies along the side external to this. The upper end receives the
neck of the uterus by an aperture in the anterior wall ; and the
lower end, the narrowest part of the canal, is encircled by the
sphincter vaginae muscle. A large plexus of veins surrounds the
vagina within its sheath. In children, and in the virgin, the
external aperture is partly closed by the hymen (p. 255).

The BLADDER (fig. 146 and fig. 147, h) is placed at the fore
part of the pelvis, in front of the vagina, and in contact with the
back of the pubic bones. Its positions and relations so closely
resemble those of the bladder in the male body, as to render
unnecessary a separate description of them (p. 387). The chief
difterences in the bladder of tlie two sexes are the following : —

In the female the bladder is more globular than in the male,
and the transverse often exceeds the longitudinal measurement.

VESSELS AND NERVES OF THE PELVIS. 395

The base is of less extent, and is in contact with the vagina and the
neck of the uterus. The vasa deferentia, vesiculae seminales and
prostate are absent.

The URETER has a longer course in the female than in the male Course of
pelvis before it reaches the bladder. After crossing the internal
iliac vessels, it passes by the neck of the uterus to its destination.

The URETHRA (fig. 146 and fig. 147, g) is about one inch and a Urethra:
half long, and by its position corresponds to the i>rostatic and length ;
membranous portions of the male passage, although it represents
only the upper half of the prostatic urethra. It is situate in front position and
of the vagina, and describes a slight curve, with the concavity *^^"^® '
forwards, below the symphysis pubis. Its external opening
(meatm urinarius) is placed within the vulva (p. 255).

In its course to the surface it is embedded in the tissue of the relations,
vagina wall, and perforates the triangular ligament of the perineum,
where it is surrounded by fibres of the deep transverse muscle, and
a layer of circular involuntary fibres (p. 258). A plexus of veins
surrounds the urethra as well as the vagina.

VESSELS AND NERVES OF THE PELVIS.

In the pelvis are contained the internal iliac vessels and their Vessels and
branches to the viscera, the sacral plexus of nerves, and the sym- J^I^i^L
pathetic nerve. This section is to be used by the dissectors of both
the male and female pelvis.

Directions. The internal iliac vessels are to be dissected on the
right side. The air should be previously let out of the bladder ;
and this viscus and the rectum, with the uterus and the vagina in
the female, should be drawn aside from their situation in the centre
of the pelvis (fig. 148).

Dissection. The loose tissue and fat are to be removed from to dissect

the trunk of the vessels, as well as from the branches of the arteries ^5+J^t^^-
' of the penis,

that leave the pelvis, or supply the viscera ; and the cord of the
oblit€rated hypogastric artery is to be traced on the bladder to the
umbilicus.

With the vessels are offsets of the hypogastric plexus of nerves, nerves,
though these will probably not be seen ; but in dissecting the
vessels to the bladder and rectum, visceral branches of the sacral
spinal nerves will now come into view. The veins may be removed veins,
in a general dissection.

^\'hen the vessels have been prepared the bladder may again
lie distended, and the viscera replaced.

The INTERNAL ILIAC ARTERY (fig. 148, gr, p. 397) is OUe of Internal

the trunks resulting from the division of the common iliac artery, ' '^^* ^•
and furnishes branches to the viscera and wall of the pelvis, to the
organs of generation, and to the limb.

In the adult the vessel is a short trunk of large capacity, which size and
measures from an inch to an inch and a half in length. Directed ^"° '
downwards towards the great sacro-sciatic foramen, the artery termi- tennination;
nates generally in two divisions (anterior and posterior), from which

396

DISSECTION OF THE PELVIS.

relations ;

position of
vein ;

branches.

the several offsets are furnished. From the extremity a partly-
obliterated vessel (hypogastric) extends forwards on the bladder.

The artery is covered by the peritoneum, and the ureter crosses
its upper end obliquely on the inner side. It lies on the sacrum
and the lumbo-sacral cord. It is accompanied by the internal iliac
vein, which is posterior to it, and somewhat to its inner side.

The branches of the artery are numerous, and arise usually in the
following manner :

From the posterior division

1. Ilio-lumbar.

2. Upper lateral sacral.

3. Lower lateral sacral.

4. Gluteal.

Artery in
the foetus.

on the
bladder,

From the anterior division:

1. SujDerior vesical.

2. Inferior vesical (vaginal
in the female).

3. Obturator.

4. Middle haemorrhoidal.

5. Uterine (in the female).

6. Sciatic.

7. Internal pudic.

Artery in the foetus. In the fcetus the hyporjastric artery takes
the place of the internal iliac, and leaves the abdomen by the
umbilicus. At that time it is larger than the external iliac artery ;
and, entering but slightly into the cavity of the pelvis, it is directed
forwards to the bladder, and along the side of that viscus to its
apex.

and beyond ; Beyond the bladder the artery ascends along the posterior aspect
of the abdominal wall with the urachus, converging to its fellow.
Finally, at the umbilicus, the vessels of opposite sides come in con-
tact with the umbilical vein, and, passing from the abdomen
through the aperture at that spot, enter into the placental cord,
where they receive the name umbilical.

In the foetus, branches similar to those in the adult are furnished
by the artery, though their relative size at the two periods is very
different.

Change to adult state. When uterine life has ceased, the hypo-
gastric artery shrinks in consequence of the arrest of the current
of blood through it, and finally becomes obliterated, more or less
completely, to within an inch or so of its commencement. The
fart of the trunk which is unobliterated becomes the internal iliac ;
and commonly a portion of the vessel remains pervious as far as the
bladder, forming the early part of the superior vesical artery.

branches.

Transfoiina
tion into
that of the
adult.

Trunk often Peculiarities. The length of the internal iliac artery varies from half an
varies in inch to three inches, its extreme measurements ; but in two-thirds of a large

number of bodies it ranged from an inch to an inch and a half (R. Quain).
Size. In the rare cases where the fenioial trunk is derived from the

internal iliac, and is placed at the back of the thigh, this vessel is larger than

the external iliac.

length,

rarely in
size.

Branches of A. The BRANCHES arising from the posterior division of the
^heposterior internal iliac may be first examined.

The ilio-lumbar artery (fig. 148, h) passes outwards beneath the

part,
Ilio-lumbar

has an

THE INTERNAL ILIAC ARTERY.

39/

and

psoas muscle and tlie obturator nerve, but in front of the lumbo-
sacral cord, and divides into an ascending and a transverse branch : —

The ascending or lumbar branch runs beneath the psoas ; it ascending
supplies that muscle and the quadratus lumborum, anastomoses
with the last lumbar artery, and sends a small spinal branch through
the foramen between the sacrum and the last lumbar vertebra.

The transverse or Uiac branch divides into offsets that ramify in a transverse

branch.

Gluteal artery.
Sciatic artery.
Internal pudic
artery.

Fig. 148. — The Internal Iliac Artery (Tiedemann).

Bladder.

d. External iliac.

Lower end of the rectum.

e. Deep epigastric.

Levator ani.

/. Deep circumflex iliac.

Psoas magnus.

g. Internal iliac, continued by an

Psoas parvus.

impervious cord along the bladder.

Iliacus.

h. Ilio-lumbar.

Yas deferens.

i. Lateral sacral.

Vesicula seminalis.
Arteries:

k. Obturator.

I. Middle hsemorrhoidal.

a.
iliac

Aorta splitting into the common

Nerves :
1. Lnmbo-sacral cord.

Middle sacral.

2, 3, 4. Upper three sacral nerves.

Common iliac.

5. Obtui-ator.

the iliacus muscle, some ruimmg over and some beneath it. At
the iliac crest these branches anastomose with the lumbar and deep
circumflex iliac arteries ; some deep twigs communicate with the
obturator artery, and enter the hip-bone.

The ilio-lumbar vein opens into the common iliac trunk.

Lateral

The lateral sacral arteries (fig. 148, i) are usually two in number, sacral

arteries

398

DISSECTION OF THE PELVIS.

supply-
spinal
branches.

superior and inferior : they correspond in situation Math the
lumbar arteries, and form a chain of anastomoses by the side of
the apertures in the sacrum. These arteries supply the pyriformis
and coccygeus muscles, and anastomose with each other, as well as
with the middle sacral. A spinal branch enters each aperture in the

Gluteal
artery :

small
offsets.

Branches
of anterior
part.

Upper
vesical.

Lower
vesical

or vaginal.

Middle
haemor-
rhoidal.

Hypogastric
trunk.

Obturator
artery
courses
across
pelvis :

offsets in
pelvis ;
iliac branch.

pubic
branch.

The gluteal artery {Hg. 148, m) is the continuation of the posterior
division of the internal iliac, and is destined for the gluteal muscles
on the outer surface of the hip-bone. It is a short, thick trunk
which leaves the pelvis through the great sacro-sciatic fcramen
above the pyriformis muscle, with its accompanying vein and the
superior gluteal nerve, passing between the lumbo-sacral cord and
the anterior division of the first sacral nerve, or sometimes between
the anterior divisions of the first and second sacral nerves, as in
fig. 148. In the pelvis the artery gives small branches to the con-
tiguous muscles, viz., iliacus, pyriformis, and obturator, and a twig
to the hip-bone.

B. The BRANCHES of the anterior division of the internal iliac
artery are the following : —

The superior vesical artery is the imperfectly obliterated portion
of the foetal hypogastric artery. It divides into three or four
branches, which ramify over the apex and body of the Ijladder : the
lowest of these is sometimes called the middle vesical branch.

The inferior vesical artery often arises in common with the biancli
to the rectum. It is distributed to the base of the bladder, the
vesiculse seminales, and the prostate. A small offset from this
artery, or from the upper vesical, is furnished to the vas deferens,
and is known as the artery of the vas deferens.

The vaginal artery (fig. 147, e) of the female takes the place of
the inferior vesical of the male. It descends on the vagina, and
ramifies in its wall as low as the outer orifice ; while, superiorly, it
communicates with the lower branches of the uterine artery. This
branch is often given off by the uterine artery.

The middle hcemorrhoidal artery (fig. 148, I) commonly arises from
the inferior vesical (or vaginal), or from the pudic trunk. It is
spent on the anterior and lower part of the rectum, and anastomoses
with the other heemorrhoidal arteries.

The preceding arteries sometimes arise in common with the
superior vesical, and the trunk of origin is termed the hypogastric
trunk.

The obturator artery (fig. 148, k) is directed forwards below the
brim of the pelvis to the aperture at the toj) of the thyroid foramen ;
passing through that opening it ends in two branches, which
ramify on the membrane closing the thyroid foramen, beneath the
obturator externus muscle. In the pelvis the artery has its com-
panion nerve above, and vein below it ; and it there gives rise to : —

An iliac branch which enters the iliac fossa to supply the bone
and the iliacus muscle, and anastomoses with the ilio-lumbar artery.

A pubic branch (fig. 107, /, x^- 294) ascends on the posterior
aspect of the pubis, and communicates with the corresponding

BEANCHES OF THE INTERNAL ILIAC ARTERY. 399

branch of the opposite side, and with an offset from the epigastric
artery.

Sometimes the obturator takes origin from the deep epigastric,
as explained on p. 284, or from the external iliac artery.

The sciatic artery (fig. 148, n) is the largest branch of the anterior Sciatic
division of the internal iliac, and is continued over the pyriformis ^^^^''^
muscle and the sacral plexus to the lower part of the great sacro- in the pelvis,
sciatic foramen, where it issues between the pyriformis and the
coccygeus muscles. Outside the pelvis it divides into branches and outside
beneath the gluteus maximus, and is distributed to the buttock : in * *
the pelvis it supplies the pyriformis and coccygeus muscles.

The internal pudic artery (fig. 148, o) supplies the perineum and Pudic artery
the genital organs, and has nearly the same relations in the pelvis p^ivis :
as the sciatic. It accompanies the sciatic artery, though external
to it, and leaves the pelvis between the pyriformis and coccygeus.
At the back of the pelvis it winds over the ischial spine of the
hip-bone, and enters the perineal space, where it has already
been examined. The artery gives some unimportant offsets in
the pelvis, and frequently the middle hsemorrhoidal branch arises some small

t -. offsets.

irom it.

Accessory pudic (R. Quain). The pudic artery is sometimes smaller than An acces-
usual, and fails to supply some of its ordinary perineal branches, especially ^^^^ pudic
the terminal one to the penis. In those cases the deficient branches are
derived from an accessory aitery, which takes origin from the internal iliac
(mostly from the trunk of the pudic), and courses forwards on the side of
the bladder and the prostate gland, to perforate the triangular ligament.
It furnishes branches to the penis to supply the place of those that are
wanting.

The uterine artery (fig. 147, d) passes inwards between the layers uterine
of the broad ligament to the neck of the uterus, where the vessel ^ *^ '
changes its direction, and ascends in a tortuous manner along the
side of the uterus up to the fundus. Numerous branches enter the
substance of the uterus, and ramifying in it, are remarkable for
their tortuous condition. At the neok of the uterus some small offsets to
twigs are supplied to the upper part of the vagina and to the "
bladder, conmiunicating with branches of the vaginal artery. At joins
the fundus of the uterus some branches proceed outward along the °^*"^"'
Fallopian tube and anastomose with the ovarian artery from the
aorta. A branch also proceeds from the upper part of the uterus
along the round ligament.

The INTERNAL ILIAC VEIN receives the blood from the wall of internal

the pelvis, and the pelvic viscera, by branches corresponding for positionto

the most part with those of the artery. The vein is a short thick its artery ;

trunk, which is situate at the posterior and inner aspect of the

artery ; and it ends by uniting with the external iliac to form the ending ;

common iliac vein.

Tributaries. Most of the vessels entering the trunk of the its branches

that are
internal iliac vein have the same anatomy as the arteries ; but the peculiar are

following branches, — the pudic and the dorsal vein of the penis,

the vesical and haemorrhoidal, the uterine and vaginal, have some

peculiarities.

400

DISSECTION OF TFIE PELVIS.

pudic,

dorsal vein
of penis,

haemor-
rhoidal.

vesical,
uterine, and

vaginal
veins.

Other
arteries in
the pelvis.

Ovarian
artery :
offsets.

Superior

hfemor-

rhoidal

ends in
loops.

Middle
sacral,
which has

lateral
offsets.

Dissection
of the nerves
of the pelvis

The pudic veins receive roots corresponding with the branches of
the pudic artery in the perineum, but not those corresponding
with the offsets of the artery on the dorsum of the penis.

The dorsal vein of the penis receives veins from the corpora
cavernosa and corpus spongiosum of the penis, and entering the
pelvis below the symphysis pubis, divides into two, a right and
a left branch, which join a large plexus round the prostate (prostatic
plexus).

The middle hcemorrhoidal vein communicates with a large plexus
(hsemorrhoidal) around the lower end of the rectum l^eneath the
mucous membrane.

The vesical veins begin in a plexus about the fundus of the
bladder, and anastomose with the prostatic and hsemorrhoidal veins.

The uterine veins are numerous, and form a plexus in and by the
side of the uterus : this plexus inosculates above with the ovarian
plexus, and below with one on the vagina.

The vaginal veins surround their tube with a large vascular
plexus communicating with the veins of the bulb of the vestibule
below and with the uterine plexus above.

The arteries in the pelvis, which are not derived from the
internal iliac, are the ovarian, superior heemorrhoidal, and middle
sacral.

The OVARIAN ARTERY (p. 365), after passing the brim of the
pelvis in the ovario-pelvic ligament, becomes tortuous, and enters
the broad ligament to be distributed to the ovary : it supplies an
offset to the Fallopian tube, and another to the round ligament ;
and a large branch anastomoses internally with the uterine artery.

The SUPERIOR HEMORRHOIDAL ARTERY, the continuation behind
the rectum of the inferior mesenteric (p. 318), divides into two
branches near the middle of the sacrum. From the point of division
the l»ranches are continued along the rectum, one on each side, and
each ends in about three branches, which pierce the muscular layer
of the gut three inches from the anus ; they terminate opposite the
internal sphincter in anastomotic loops beneath the mucous mem-
brane, and anastomose with the middle and inferior hsemorrhoidal
arteries.

The MIDDLE SACRAL ARTERY arises from the back of the aorta
just before its bifurcation (fig. 148, h) and descends along the middle
of the last lumbar vertebra, the sacrum, and the coccyx. The
artery gives small branches laterally, opposite each piece of the
sacrum, to anastomose with the lateral sacral arteries, and to supply
the nerves, and the bones with the periosteum. Sometimes a
small branch is furnished by it to the lower end of the rectum,
to take the place of the middle hsemorrhoidal artery.

The middle sacral veins end in the left common iliac.

Dissection (fig. 149, p. 401). To dissect the nerves of the
pelvis, on the right side, it will be necessary to detach the
triangular ligament with the urethra from the bone ; and to cut
through, on the right side, the fore part of the recto- vesical fascia
and levator ani, together with the visceral arteries, in order that

THE SACRAL NERVES.

401

the viscera may be drawn from the side of the pelvis. If the
Ijladder is still distended, let the air escape from it.

By means of the foregoing dissection the sacral nerves may be
found as they issue from the sacral foramina. The dissector should
follow the first four into
the sacral plexus, and some
branches from the third
and fourth to the viscera.
The last sacral and the
coccygeal nerve are of
small size, and will be
detected coming through
the coccygeus muscle, close
to the coccyx : these are
to be dissected with care ;
and the student will suc-
ceed best by tracing the
connecting filaments which
pass from one to another,
beginning above with the
offset from the fourth
nerve.

Opposite the lower part
of the rectum, bladder,
and vagina is a large plexus
of _ the sympathetic (pelvic
plexus), which sends
branches to the viscera
along the arteries. This
plexus is generally de-
stroyed in the previous
dissection ; but if any of
it remains, the student
may trace the offsets dis-
tributed from it, and its
communicating branches
with the spinal nerves.

Sacral spinal nerves
(figs. 149; 150, p. 403).
The anterior primary
branches of the sacral
nerves are five in number,
and decrease rapidly in
size from above down-

fii-st four
sacral,

sympa-
thetic.

Fig. 149. — The Sacral Nerves and
Plexus (altered from Henle).

a. Urinary bladder.
h. Rectum.

c. Levator aui.

d. Coccygeus.
Nerves :

4 1 and 5 1. Fourth and fifth lumbar
nerves, giving rise to the lumbo-sacral cord.
1 S to ^ S. Five sacral nerves.
1 c. Coccygeal nerve.

1. Upper gluteal nerve.

2. Branch to levator ani.

3. Branch to tbe bladder.

4. Branch to coccygeus.

5. Branch to the perineum.

6. Common branch of 4 <S, 5 aS', and 1 c,
for the back of the coccyx.

The sympathetic chain lies on the front of
the sacrum, just outside the plane of section.

Sacral
nerves are
five:

wards. Issuing by the
apertures on the front of the sacrum (the fifth nerve excepted),
they receive short filaments of communication from the gangliated
cord of the sympathetic. The first three nerves and part of the
fourth enter the sacral plexus, but the fifth ends on the back of
the coccyx.

D.A. D D

most enter
plexus.

402

DISSECTION OF THE PELVIS.

Fourth,
which gives
visceral,

and muscu-
lar offsets.

Fifth is be-
low aper-
tures in
sacrum :

ends on
coccyx.

Coccygeal

Sacral

plexus ;

situation

how formed ;
ending :

and
branches :

Great
sciatic.

The coccygeal nerve and the peculiarities of the fourth and fifth
sacral will be noticed before the plexus is described.

The FOURTH NERVE (fig. 149, 4 S) sends one branch upwards
to the sacral plexus, another downwards to join the fifth nerve,
and distributes the following offsets to the viscera and the muscles
of the floor of the pelvis : —

The visceral branches (^) supply the bladder and the vagina, and
communicate with the sympathetic nerve to form the pelvic
plexus. Offsets are added to them from the third sacral nerve
(fig. 150, v).

The muscular brandies are three in number. One rather long
branch (tig. 149, 2) enters the levator ani on the visceral aspect ;
another ("*) supplies the coccygeus ; and the third (perineal) or
hsemorrhoidal branch (5) reaches the .perineum by piercing
the levator ani or coccygeus muscle, and supplies the external
sphincter.

The FIFTH NERVE (5 S) comes forwards between the sacrum and
coccyx, and receives the commimicating branch from the fourth
nerve ; it is then directed downwards in front of the coccygeus,
where it is joined by the coccygeal nerve, and perforates that
muscle, the sacro-sciatic ligament, and the gluteus maximus, to
end on the posterior surface of the coccyx.

The COCCYGEAL NERVE (1 c), after issuing by the lower aperture
of the spinal canal, appears through the coccygeus muscle, and joins
the fifth sacral nerve as above stated.

Sacral plexus. This plexus is formed by the lumbo-sacral
cord, the first three sacral nerves, and part of the fourth sacral. It
is situate on the pyriformis muscle, beneath the sciatic and pudic
branches of the internal iliac artery ; and the nerves entering it
converge towards the large sacro-sciatic foramen. Here they are
united for the most part in a broad flat band, which, becoming
gradually narrower as it leaves the pelvis below the pyriformis,
forms the great sciatic nerve. A part of the third nerve, however,
and the branch of the fourth entering the plexus unite to form a
lower smaller trunk — the pudic nerve ; and other branches are
given off by the several nerves before their union.

Branches. Most of the offsets of the plexus are distributed out-
side the pelvis, and are met with in the dissection of the buttock
(pp. 109 et seq.) ; of these only the origin is to be seen now. The
branches of the plexus are : —

1. The great sciatic nerve.

2. The small sciatic nerve.

3. The superior gluteal nerve.

4. Inferior gluteal nerve.

5. The pudic nerve.

6. Nerve to the obturator internus and superior gemellus.

7. Nerve to the quadratus femoris and inferior gemellus.

8. Nerve to the pyriformis.

9. Perforating cutaneous nerve.

a. The great sciatic nerve (fig. 150, gs) is the principal nerve of

THE SACRAL PLEXUS.

403

the lower liiiib, and is formed by the union of four large roots from
the lumbo-sacral cord and the first three sacral ner^'es.

b. The superior gluteal Twrve (fig. 150, sg) arises by two roots Superior
from the back of the lumbo-sacral cord and the first sacral siuteaL
nerve, and leaves the pelvis with the gluteal artery above the

Fig. 150. — Diagram of the Sacral Plbxus, prom Behind.

LSC. Lumbo-sacral cord, formed by
the fifth him bar nerve and a small
branch from the fourth.

SI to SV. First to fifth sacral
nerves.

Co. Coccygeal nerve.

gs. Great sciatic nerve.

ss. Small sciatic.

p. Pudic.

sg. Superior gluteal.

ig. Inferior gluteal.

py. Branch to pyriformis.

oi. Nerve to obturator internus.

q. Nerve to quadratus.

V. Viscei-al branches of third and
fourth sacral nerves.

la. Branch to levator ani.

CO. Branch to coccygeus.

h. Haemorrhoidal or perineal
branch of fourth sacral.

pc. Perforating cutaneous.

pyriformis for the supply of the muscles on the outer surface of
the ilium.

c. The inferior gluteal (ig) is the nerve of the gluteus maximus. inferior
It springs from the back of the lumbo-sacral cord and first two 8'"^**^
sacral nerves, and passes out below the pyriformis.

d. The small sciatic (ss) is the cutaneous nerve of the back of the Sn>aU

DD 2

sciatic.

404

DISSECTION OF THE PELVIS.

Pudic.

Perforating
cutaneous.

Branch to
pyriformis.

Branch to
obturator
internus.

Branch to
quadratus.

Symi)athetic
in the pelvis.

The gan-
gliated cord

joins that
of opposite
side below
in a loop ;

offsets of
the

to the spinal
nerves,

to the pelvic
plexus and
the viscera.
Pelvic
plexuses ;

situation ;

how formed :

offsets to
the viscera
of the male,
viz.,

to the

rectum ;

thigh, and arises befoie the foregoing (with which it is often con-
nected) from the second and third sacral nerves.

e. The 'pudic nerve (p) supplies the perineum and the genital
organs. It arises from the third and fourth sacral nerves, and
courses over the small sacro-sciatic ligament, in company with its
artery, to the small sacro-sciatic foramen.

/. The perforating cutaneous nerve (pc) arises from the fourth, or
the third and fourth, sacral nerves, and passes backwards through
the great sacro-sciatic ligament to the skin of the buttock (p. 112).

g. The branch to the pyriformis (py) is usually given off from the
second sacral nerve, and enters the anterior surface of its muscle.

h. The nerve to the obturator internus (oi) springs from the front
of the part of the plexus formed by the union of the lumbo- sacral
cord with the first sacral nerve. It leaves the pelvis Avith the pudic
artery, and winding over the ischial spine and through the small
sacro-sciatic foramen, enters the perineal surface of the muscle : it
gives a branch to the superior gemellus.

i. The nerve to the quadratus femoris and inferior gemellus (q)
arises from the front of the plexus below the preceding.

Sympathetic Nerve. In the pelvis the sympathetic nerve con-
sists of a gangliated cord, and of a plexus on each side.

The Gangliated cord (fig. 149) lies on the front of the sacrum,
internal to the series of apertures in that bone. Inferiorly it con-
verges to its fellow, and is united with it by a loop in front of the
coccyx, on which there is often a median ganglion {gang, impar).
Each cord is marked by ganglia at intervals, the number varying
from three to five : from them branches of communication pass
outwards to the spinal nerves, and some filaments are directed
inwards in front of the sacrum.

The connecting branches are usually two to each ganglion, grey
and white, and are very short.

The internal branches are small, and communicate around the
middle sacral artery with the branches of the opposite side. From
the first, or first two ganglia, some filaments are furnished to the pelvic
plexus ; and from the terminal loop oftsets descend over the coccyx.

The Pelvic plexuses (lateral inferior hypogastric) are two in
number, right and left, and are continuous with the lateral pro-
longations of the hypogastric plexus (p. 319). Each is situate by
the side of the bladder and rectum, in the male, and by the side of
the uterus and vagina in the female, and is joined by off'sets of the
third and fourth sacral nerves. Numerous ganglia are found in
the plexus, especially at the points of union of the spinal and
sympathetic nerves.

Offsets. From each plexus off'sets are furnished along the
branches of the internal iliac artery to the viscera of the pelvis,
and the genital organs : these form secondary plexuses, and have
the same name as the vessels on which they are placed.

The inferior hemorrhoidal plexus is an offset from the back of
the plexus to the rectum, and joins the sympathetic on the superior
haemorrhoidal artery.

SYMPATHETIC NERVE. 405

The vesical plexus contains large offsets, witli many white-fibred to the
or spinal nerves, and passes forwards to the side and neck of the ^^*
bladder. It gives one plexus to the vesicula seminalis, and another
to the vas deferens.

The prostatic pk-fu^ leaves the front of the pelvic plexus, and to the pro-
supplies the substance of the prostate. At the front of the prostate '^^^°*^
an offset (cavernous) is continued onwards to the dorsum of the
penis, to supply the cavernous structure. On the penis the
cavernous nerves join the pudic nerve.

In the female there are the following additional plexuses for the offsets in
supply of the viscera peculiar to that sex : — * ^ ^^^ ®'

Ovarian plexus. The chief nerves to the ovary are derived from to the
the renal and aortic plexuses, and accompany the ovarian artery ; °^*^ »
but the uterine nerves supply some filaments to it.

Vaginal nerves. The nerves of the vagina are large, and are not to the
plexiform, but consist in greater part of spinal nerve-fibres ; they ^*^°*'
end in the lower part of the tube.

The uterine nei-ves are furnished to the uterus with, only a small and to the
admixture of the spinal nerves ; they ascend along the side of the "*®'^^-
uterus, and consist of long slender filaments without ganglia or
communications. The Fallopian tube receives its branches from
the uterine nerves.

Some few nerves surrounding the arteries of the uterus are
plexiform and ganglionic.

The LYMPHATIC GLANDS OF THE PELVIS form one chain in front Chain of pel-
of the sacrum, and another along the internal iliac vessels : their ^^^ glands;
efferent ducts join the lumbar glands. Into these glands run the
deep lymphatics of the penis, of the genital organs in the female, lymphatics
and the lymphatics of the viscera and wall of the pelvis. entering

Section II.

ANATOMY OF THE VISCERA OF THE MALE PELVIS.

Directions. The rectimi with the bladder and the bodies at
its base, viz., the vesiculao seminales, and the prostate gland, are
now to be taken bodily away for examination.

Dissection. In order to remove them from the pelvis the Take ont
student should carry the scalpel round the pelvic outlet, close to ^^^ ^^cera,
the osseous boundary, so as to detach the crus of the penis from separate
the bone, and the end of the rectum from the parts around. When ^^^^^™J
the viscera are removed, the rectum is to be separated from the
other organs ; but the bladder, the penis, and the urethra are to
remain united.

After the bladder has been distended with air, the areolar tissue clean the
is to l>e removed from its muscular fibres. The prostate gland ^^*^^®'"'
and the vesiculee seminales are then to be cleaned ; and the duct of
the latter, with the vas deferens, is to be followed to the gland.

Any integument left on the penis is to be removed. and penis.

406

DISSECTION OF THE PELVIS.

THE PROSTATE GLAND AND SEMINAL VESICLES.

Prostate
gland :

situation ;

form ;
dimensions ;

and weight.
Surfaces :

base;
and apex.

Tliree lobes,
two lateral,

and a cen-
tral.

often
enlarged.

Gland con-
tains three
tubes.

Structure.

Muscular
fibres are
plain-
circular,

radiating,

Prostate Gland (fig. 151, p. 408). This is a firm muscular
body containing glands, which surrounds the neck of the bladder
and the beginning of the urethra. Its relations have already been
enumerated at p. 388.

The prostate is conical in form, like a chestnut, with the base
directed upwards. Its dimensions are the following : — Trans-
versely at the base it measures about an inch and a half ; from
apex to base an inch and a quarter ; and from before backwards about
three-quarters of an inch or an inch : so that an incision directed
obliquely outwards and backwards will be the longest that can be
practised in the half of this body. Its weight is about an ounce,
but in this respect it varies greatly.

The anterior surface of the prostate is narrow and rounded. The
posterior surface, larger and flatter, is marked by a median hollow
which indicates the division into lateral lobes.

The base is thick, and at its posterior part has a median notch,
which receives the common seminal ducts. The apex is pierced by
the urethra.

Three lobes are described in the prostate, viz., a middle and two
lateral, though there is no fissure in the firm mass. The lateral
lobes (fig. 151, 6, c) are similar on the two sides, and are separated
only by the hollow on the under surface ; they form the chief part
of the prostate, and are prolonged back, on each side, beyond the
notch in the base. The middle lobe (d) will be brought into view
by separating the vesiculee seminales and the vasa deferentia from
the bladder : it is the piece of the gland between the neck of the
bladder and the seminal ducts, which extends across between the
lateral lobes. Oftentimes the middle lobe is enlarged in old
people, and projects upwards into the bladder, so as to interfere
with the flow of the urine from that viscus, or the passage of a
catheter into it.

The urethra and the two common seminal ducts are contained
in the substance of the prostate as will be seen immediately. The
former is transmitted through the gland from base to apex ; and
the latter perforate it obliquely to terminate in the urethral canal.

Structure. On section the prostate appears reddish grey in colour,
is very firm to the feel, and is scarcely lacerable. It is made up
of a mass of muscular and fibrous tissues, with interspersed glandu-
lar substance ; and the whole is enveloped by strong proper capsule
and is surrounded by a fibrous sheath derived from the recto-vesical
fascia, which is sometimes styled the false capsule.

Muscular tissue. The firm mass of this body consists mainly of
involuntary muscular fibres, intermixed with elastic and fibrous
tissues. One set of muscular fibres is arranged circularly round
the urethral canal, — these are continuous above with the annular
fibres of the bladder, and below with a thin layer of circular fibres
surrounding the membranous portion of the urethra ; others run
transversely behind the urethra, and radiate in each lateral lobe

STRUCTURE OF THE PROSTATE. 407

through the glandular substance. Over the greater part of the and super,
surface is an external stratum, forming a kind of capsule, which 1 1 • ^
adheres to the fibrous sheath. Along the front and towards the "^

apex, the superficial part of the organ is composed of striated mus-
cular fibres, also disposed transversely, which are continued into
the constrictor urethras muscle between the layers of the triangular
ligament.

Glandular substance. This is composed of a number of small Glands in
branched glands, Avhich are embedded in the muscular stroma, masses:
There are three chief collections, — a small one in the central lobe,
and a larger one in each lateral lobe. The ducts of the glands ducts open
vary in number from twelve to twenty, and open into the prostatic irethra!
part of the urethra (p. 413).

Blood-vessels. The arteries are small, and are furnished by the Arteries,
inferior vesical and middle hsemorrhoidal. The veins form a plexus ^'^i"^ ^^"^
round the gland, which receives in front the dorsal vein of the
penis, and is continued behind into the plexus at the base of the
bladder. The plexus is situated between the fascial investment
and the proper capsule of the gland, and the vessels of the plexus
are specially large at the back of the pubis at the entry of the
dorsal vein of the penis. In old men these vessels may give rise
to considerable haemorrhage in the operation of lithotomy.

The nerves are supplied from the pelvic plexus. The lymphatics Nerves,
of this body and of the vesiculse seminales are received into the Lymphatics,
glands by the side of the internal iliac artery.

Vesicdl^ Semixales (fig. 151, e). These vesicles are two mem- seminal
branous sacs, which serve as receptacles for, and probably secrete a ^^^^^^^^^ '
special fluid to mix with, the semen. They are placed at the base definition ;
of the bladder above the prostate, and diverge from one another so situation ;
as to limit laterally a triangular space in that situation : their form
and relations have been already described (p. 389). Though form;
sacculated and bulged above, the vesicula becomes straight and
narrowed below (duct) ; and at the base of the prostate it blends
Avith the vas deferens to form the common seminal or ejaculatory
duct (^f).

The vesicula seminalis consists of a tube bent into a convoluted consist of a
form, so as to produce lateral sacs or pouches, the bends of which are ° ^ ^ »
bound together by fibrous tissue ; this cellular structure will be
shown by means of a cut into it. When the bends of the vesicle
are undone, as may be done by carefully dissecting away the
investing tissue, its formative tube, which is about the size of a
quill, measures from four to six inches in length, and ends above in
a closed extremity : connected with the tube at intervals, are lateral length and
blind caecal appendages (fig. 151). ^^^®-

Structure. The wall of the seminal vesicle like the vas deferens Vesicle has
has an outer and inner layer of longitudinal muscle fibres with an ^^ ^^ '
intermediate circular layer, but the tubal muscular coat is thinner.

Within the casing of the recto-vesical fascia, the vesiculae and a covering
vas deferentia are covered by a layer of transverse and longitudinal fibres •*'"^*'^
plain muscular fibres. The transverse are the more superficial

408

DISSECTION OF THE PELVIS.

and a rau-
cous coat.

(the base of the l^ladder being upwards), and are strongest near the
prostate, acting most on the vas'a deferentia. The longitudinal
fibres, placed chiefly on the sides of the vesiculoe, are continued
forwards with the common seminal ducts to the urethra. (Roy.
Med. Chir. Trans. 1856.)

The mucous membrane is thrown into ridges by the bending of
the tube, and presents an alveolar or honeycomb ajjpearanee ; it is
provided with tubular glands, as in the vas deferens.

Fig. 151. — The Posterior Surface of the Bladder, with the Vesicul^
Seminales and Vasa Deferentia (slightly altered from Haller).

/. Vas deferens.

g. Common seminal duct, formed
by the union of the vas deferens with
the duct of the vesicula.

h. Ureter.

a. Bladder.

b and c. Right and left lateral
lobes of the prostate.

d. Middle lobe.

e. Vesicula seminalis, the right one
unravelled.

End of vas
deferens.

Seminal
ducts, how
formed :

extent ;
course ;

End of vas deferens (fig. 151). Opposite the vesicula the vas
deferens is enlarged, and is rather sacculated like the contiguous
vesicle ; but before it joins the tube of that body to form the
common seminal duct, it diminishes in size, and becomes straight.
In the mucous lining are numerous tubular glands (Henle).

Common ejaculatory ducts (fig. 151, g, and fig. 153, /, p. 412).
These tubes (right and left) are formed l)y the junction of the
narrowed part or duct of the vesicula seminalis with the vas deferens
of the same side. They begin opposite the base of the prostate, and
are directed downwards and forwards through an aperture in the
transverse prostatic fibres, and along the sides of the uterus masculinus

STRUCTURE OF THE URINARY BLADDER. 409

(p. 412), to open into the urethral tube. Their length is rather length;
less than an inch, and their course is convergent to their termination termination;
close to each other in the floor of the urethra.

Structure. The wall of the common duct is thinner than that of structure,
the vesicula seminalis ; but it possesses similar coats. It is sur-
rounded by longitudinal involuntary muscular fibres, which blend
in the urethra with the submucous stratum.

THE BLADDER.

While the bladder is in the body, it is ovoidal in shape, and rather Form ;
flattened from above do^vn (pp. 387 and 388) ; but out of the body it
is rounder than when in its natural position, and it loses the arched
form by which it adapts itself in distension to the curve of the pelvis.

If this \iscus is moderately dilated, it measures about five inches dimensions,
in length, and three inches across. Its capacity is greatly influenced
liy the age and habits of the indi\idual. Ordinarily the bladder
holds about a pint without inconvenience during life, though it can
contain much more when distended.

Structure. A muscular and a mucous coat, with an intervening Coats of the
fibrous layer, exist in the wall of the bladder : at certain parts °^******''"-
the peritoneum may be also enumerated as a constituent of the wall.
The vessels and nerves are large.

The imperfect covering of peritoneum has been described (p. 378). PeritoneaL

The muscular coat is formed of three thin layers of unstriated Muscular
muscular fibres, viz., an external or longitudinal, a middle or strata,
circular, and an internal or submucous.

The longitudinal fibres (fig. 152, ^) form a continuous covering. External or
with the usual plexiform disposition of the muscular bundles, and J^f ^'**^'
extends from apex to l^ase. Above, some are connected with the attach-
urachus and the subperitoneal fibrous tissue. Below, the posterior ments ;
and lateral fibres enter the prostate ; while the anterior are attached
to the fascia covering the prostate, but a fasciculus on each side is
united to the Imck of the pubis through the anterior true ligament
of the bladder. On the front and back of the bladder the muscular
layer is stronger, and its fibres more vertical than on the sides, forms
Sometimes this outer layer of fibres is called detrusor urince from its uri^°^
action in the expulsion of the urine.

The circular fibres (fig. 152, 2) are thin and scattered on the body Middle
of the bladder ; but around the cervix they are collected into a ^+^'°"*']^
thick bimdle, the sphincter vesicce, and are continuous below with the state.
fibres of the prostate. When these fibres are hypertrophied, they
project into the interior of the organ, forming the fasciculated
bladder ; and in some bodies the mucous coat may be forced out-
wards here and there between them, in the form of sacs, producing
the sacculated bladder.

The submucous stratum (fig. 152, ^) forms a continuous layer over Submucoas
the lower half of the bladder, but its fibres are scattered above. In ^*y®^-
the lower third of the viscus the fibres are longitudinal, and are ^^_" '
continued aroimd the urethra ; but they become oblique above that

410

DISSECTION OF THE PELVIS.

addition
to it.

Strata are
joined.

Fibrous
coat.

Open the
bladder.

Mucous coat

has folds
except at
one part.

Interior of
the bladder.

Opening of
urethra,

point. At the back of the bladder the layer is increased in strength
by the longitudinal fibres of the ureters blending with it.

The muscular strata communicate freely, so that one cannot be

separated from another with-
out division of the connecting
bundles of fibres. In both
sexes the disposition of the
fibres is similar (Roy. Med.
Chir. Trans. 1856).

Fibrous or submucous coat.
A fibrous layer is placed
between the muscular and
mucous strata, and is enume-
rated as one of the coats of
the bladder ; it is composed,
as in other hollow viscera, of
areolar and elastic tissues, in
which the vessels and nerves
ramify.

Dissection. The bladder
is now to be opened by an
incision along the part of the
upper and along the anterior
surface ; and the cut is to be
carefully continued down the
front of the j)rostate gland in
the middle line, so as to open
the prostatic portion of the
urethra.

The mucous membrane of
the bladder is of a pale rose
colour in the healthy state
soon after death. It is con-
tinuous above with the lining
of the ureters, and below with
that of the urethra. It is
very slightly united to the
muscular layer ; and it is
thrown into numerous folds
in the flaccid state of the
viscus, except over a small
triangular space behind the
urethral opening.

Objects inside the bladder.
Within the bladder are the
following special parts, viz., the orifices of the ureters and urethra,
with the triangular surface (fig. 154, p. 414).

Orifices. At the lower part of the bladder is the orifice of the
urethra, surrounded by the prostate gland. The mucous membrane
presents here some longitudinal folds ; and the aperture is partly

Fm. 152. — Mgscular Fibres of the
Bladder, Prostate, and Urethra.

1. External or longitudinal fibres of
the bladder.

2. Circular fibres of the middle coat.

3. Submucous layer.

4. Muscular layer around the urethra.
.5. Circular fibres of the prostate and

urethra continuous with the circular of
the bladder.

6, 7. Septum of the corpus spon-
giosum.

8. Corpus spongiosum.

9. Corpus cavernosum.

10. Ureter.

INTERIOR OF THE BLADDER. 411

closed by a small elongated prominence behind, uvula vesicce, occa- ^ith the
sioned by a thickening of the submucous muscular and fibrous "^ *'
layers. This eminence is placed over the middle lobe of the pro-
state ; and from its anterior end a slight ridge is continued on the
floor of the urethra.

About an inch and a half from the orifice of the urethra, and Openings of
rather more than that distance apart, are the two narrow openings *^® i^reters.
of the ureters (fig. 154). The tubes perforate the wall of the
bladder obliquely, lying in it for the distance of three-quarters
of an inch, so that the reflux of fluid through them towards the
kidney is prevented as the bladder is distended. Each terminates
by a slit-like opening in a prominence of the subjacent muscular
fibres.

Trigone.

Triangular surface. Immediately behind the orifice of the Trigone of
urethra is a smooth triangular surface, which is named trigone. ^ ^ * ®^ "
(trigonum vesicae; fig. 154, a). Its apex reaches the prostate, and
its base the ureters. Its boundaries may be marked out by a line how
on each side from the urethra to the ureter, and by a transverse '^
one, behind, between the openings of the ureters. This surface part c^rre-
corresponds with the triangular space externally at the base of the extemaify.
bladder, betAveen the vesiculee seminales and vasa deferentia. Over
it the mucous coat is more closely united to the nmscular, so as to
prevent the accidental folds occurring as in the other parts of the
empty bladder.

Dissection. The arrangement of the fleshy fibres of the ureters To expose
will come into view on the removal of the mucous membrane from S^tere! °
the lower third of the bladder.

Ending of the fibres of the ureter. As soon as the ureter pierces Muscular
the outer and middle coats of the bladder, its longitudinal fibres are ureters,
thus disposed : — the more internal and strongest are directed trans-
versely, and join the corresponding fibres of the other urine tube ;
while the remainder are continued down over the triangular surface,
and blend with the submucous layer of the bladder fibres.

Blood-vessels a7id 7ierves. The source of the vesical arteries, and -Ajteries;
the termination of the veifi^s, have been detailed. The vessels are veins ;
disposed in greatest number about the base and neck of the bladder. .
Most of the nerves distributed to the bladder, though supplied from nerves of
the pelvic plexus of the sympathetic, are derived directly from the
spinal nerves. The lymphatics enter the glands by the side of the Lymphatics,
internal iliac vessels.

THE URETHRA AND PENIS.

Urethra (fig. 154). The tube of the urethra extends Urethra:
from the neck of the bladder to the end of the penis, and has length;*"
an average length of about eight inches ; but it is shorter by one
inch during life. It is supported by the prostate, the triangular
ligament, and the spongy structure of the penis. The tube is fjJJJ^J^Jtg,

412

DISSECTION OF THE PELVIS.

divided, as already stated (pp. 389 and 390) into prostatic
membranous and spongy parts.
How to open Dissectloil. To open the urethra, let the incision through the
prostate be continued onwards to the extremity of the penis along
the dorsal surface, passing as accurately as possible in the septum
between the two corpus cavernosum.

The prostatic part (figs. 153 and 154) is nearer the anterior
than the posterior surface of the mass surrounding it. It is one
inch and a quarter in length, and is the widest portion of the
urethral canal. Its form is spindle-shaped, for it is larger in the
middle than at either end. Its transverse measurement at the neck
of the bladder is nearly a third of an inch ; at its centre a line or
two more ; and at the lower end rather less than at the beginning.

the urethra.

Prostatic
part:

dimensions
and

shape ;
diameter.

Fig. 153. — Section through the Bladder, Prostate, and Urethra, to

SHOW THE VeSICULA PrOSTATICA AND THE CoMMON SeMINAL DuCT.

a. Bladder.

b. Prostate.

c. Prostatic part of urethra.

d. Vesicula seminalis.

e. Vas deferens.
/. Common ejaculatory duct.
g. Uterus masculinus ; above this
is the middle lobe of the prostate.

On the floor Separating the prostatic portion of the urethra from the bladder

IS a crest : j^g ^^le eminence known as the uvula vesicae. Beginning half an

inch below this is a central longitudinal eminence of the mucous

lining of the prostatic urethra (fig. 154, d), about three-quarters of

an inch in length, and larger above than below, which is prolonged

towards the membranous part of the canal, and is named crest of the

urethra (verumontanum, caj)ut gallinaginis) : it is formed of erectile

substance, with a framework of elastic and muscular tissues. In

the crest of the mucous membrane, near its posterior extremity, is

in the crest the opening of the uterus masculinus or utriculus (sinus pocularis

is a pouch, ^j, vesicula prostatica).

Vesicula The uterus masculinus (fig. 153, ^) is a blind passage directed

the prostate^ backwards in the prostate, from a quarter to half an inch, passing

beneath the middle and between the lateral lobes. The student

INTERIOR OF THE URETHRA. 413

can readily measure its length by passing a probe into it, and on
opening it, it will be found that its blind extremity is somewhat
dilated. Along its wall, on each side, is placed the common seminal and by its
duct (/), which terminates on or within the margin of the mouth ejaculatoiy
of the sac ; and if bristles are introduced into the common seminal ducts,
duct behind the prostate, they will render the apertures evident.
Small glands open on the surface of the mucous membrane lining
the utricle, which is the remains of the united lower ends of the
foetal ducts of Muller, and represents the uterus and vagina in the
female.

On each side of the central crest is an excavation, which is named Prostatic
the prostatic sinus (fig. 154, /). Into this hollow the greater num- in floor,
ber of the ducts of the prostatic glands open ; but the apertures of
some are seen at the back of the central eminence.

The MEMBRANOUS PART OF THE URETHRA (fig. 154, g) is three- Membran-

quarters of an inch in length, and intervenes between the apex yf o^^spart:
the prostate gland and the bulb (k) of the corpus spongiosum
urethrse. In its interior are slight longitudinal folds. This is the dimensions ;
narrowest piece of the whole tube, with the exception of the outer
orifice, and measures rather less than a quarter of an inch across.
It is the weakest of the three portions of the canal, and is supported parts
by a thin stratum of erectile tissue, by a thin layer of unstriated ^^°^^ •
circular fibres, and outside all by the constrictor urethrae muscle.

The SPONGY PART (fig. 154, i) reaches to the end of the penis. Spongy
It is about six inches in length, and its strength depends upon a ^^^ '
surrounding material named the corpus spongiosum urethrse.

The average size of the canal is about a quarter of an inch in dimensions ;
diameter, though at the vertical slit (meatus urinarius), by which
it terminates on the gians penis, the tube is smaller than elsewhere.
On a cross section it appears star-shaped, but in the glans as a
vertical slit. Two dilatations exist in the spongy portion ; — one is two dilata-
along the floor close to the triangular ligament, being contained in on?in~buib
the bulb or bulbous part of the urethra, and is named the sinus q/" one in glans;
the bulb ; the other is an elongated hollow, situate in the glans
penis, and is called the fossa navicularis (n).

There are many small pouches or lacunae (o) in the canal as far lacunae,
back as the membranous part, which have their apertures turned
towards the outer orifice of the urethra. One of these, larger than one larger
the rest, lacuna magna, is found generally immediately within the relit!
meatus, in the roof of the fossa navicularis.

The ducts of Conner's glands (fig. 154, h) are two in number. Ducts of
and terminate, one on each side, on the floor of the urethra near the cowper?
bulb ; but their openings are generally too small to be recognised.

Mucous lining of the urethra. The mucous membrane of the Mucous
urethra is continued into the bladder, as well as into the ducts ^^^^^^^Q^J
opening into the canal, and joins in front the tegumentary covering
of the glans penis. It is of a reddish colour in the spongy and colour;
membranous portions, but in the prostate it becomes whiter. In
the spongy and membranous parts it is thrown into longitudinal folds;
folds during the contracted state of the penis.

414

DISSECTION OF THE PELVIS.

Fig, 154. — The Lower Part of the Bladder and the Urethra
laid open.

a. Trigone of the bladder.
h. Openings of the ureters.

c. Prostate, cut.

d. Crest of urethra.

e. Uterus masculinus and utri-
culus.

/. Prostatic sinus, with openings
of the glands of the prostate.

g. Membranous part of the urethra.

Ti. Cowper's glands, a duct from
each opening into the urethra.

i. Spongy part of the urethra.

k. Bulb of the corpus spongiosum.

L Grlans penis.

n. Fossa navicularis.

o. Openings of the lacunae and
glands.

r. Corpus cavernosum of the penis.

STRUCTURE OF THE PENIS. 415

Its surface is studded throughout with the apertures of minute glands,
glands, which are lodged in the sul)mucous tissue, and the ducts of
which are inclined obliquely forwards.

Submucous tissue. Beneath the mucous lining of the urethra is Submucous
a stratum of longitudinal unstriated muscular fibres, mixed with ^^^^^^ '•
elastic and fibrous tissues. It is continuous behind wdth the sub-
mucous fibres of the bladder, and is joined in the prostate by the nature;
muscular fibres accompanying the common seminal ducts. The
stratum differs at spots : — it is most developed in the prostate ; in arrangement
the membranous portion the muscular structure is less abundant ; ^^ ^u'ethra.
and in the spongy part fibrous tissue forms most of the submucous
layer.

Around the membranous and prostatic di\asions of the urethra Erectile
there is, in addition, inmiediately beneath the mucous membrane, a throughout
thin layer of vascular or erectile tissue, which is continued back-
wards from the corpus spongiosum to the neck of the bladder.

Structure of the penis. The form and the relations of the Penis
penis having been described (pp. 2bl et seq.) the bodies of which it is two^vascuiar
composed remain to be noticed. If a section is made along one ^^^^^
side of the penis, it will show this organ to be composed of two
masses of spongy and vascular tissue (corpora cavernosa) encased
in a fibrous covering, with an imperfect septum between them, and
having the corpus spongiosum attached along their under surface.

Corpora cavernosa (fig. 154, /•). These bodies form the bulk Corpora
of the penis, and are two dense cylindrical tubes of fibrous tissue, SSS*
containing erectile structure. Each is fixed behind by a pointed behind
process, crv^ penis, to the conjoined rami of the ischium and pubis blend
for about an inch, and blends with its fellow in the body of the [n^ftint^-
penis, about an inch and a half from its posterior extremity. There
is a slight swelling on the crus, called the bulb of the corpus caver- bulb,
nosum (Kobelt).

Each corpus cavemosum is composed of a fibrous case containing structure :
a cavernous or trabecular structure, with blood-spaces between the
trabeculae of the spongy mass. An incomplete median septum
exists along the body of the penis.

The fibrous case is a white, strong, elastic covering which, along a case
the middle of the penis, sends inwards a septal process between the that sends
two corpora cavernosa as well as numerous other finer threads, ^^^ Processes;
which are connected with the trabeciilas of the spongy structure,
of which the corpus cavernosum is composed.

It is formed of white shining fibres which are disposed in two fibres form
layers, outer and inner. The outer stratum is formed of longi-
tudinal fibres with close meshes. The inner stratum consists of
circular fibres, with a like plexiform disposition ; and the circular
fibres of each cavernous body meeting in the middle line give rise
to the septum penis. Both strata are inseparably united by
communicating bundles.

The septal process (fig. 155) is placed vertically along the body a septal
of the penis, and is thicker and more perfect behind than in front. ^^^^^'
Near the junction of the crura this partition divides the enclosed

416

which is
imperfect ;

how
formed ;

and nume-
rous bands
and cords to
form a net-
work.

Source of
the arteries ;

termination
in venous
spaces.

Veins in
two sets.

Spongy
material of
the penis :

its structure
like caver-
nous.

The fibrous
case.

DISSECTION OF THE PELVIS.

cavity into two ; but as it reaches forwards it becomes less strong,
and is pierced by elongated apertures, which give it the appearance
of a comb, from which its name, septum jpectiniforme, is derived.
Through the intervals in the septum the vessels in the corpora
cavernosa communicate. It is formed by the circular fibres of ihi^
fibrous case.

The cavernous or trabecular structure is a network of fine threads,
which fills the interior of the corpora cavernosa. Its processes are
thinner towards the centre than at the
circumference ; and the areolar spaces are
larger in the middle and at the fore part
of the contained cavity, than at the cir-
cumference or in the crura of the penis.
The spongy structure may be demonstrated
by sections of the penis, after it has been
distended with air and dried.

Blood-vessels. The blood-vessels of the
penis are of large size, and serve to nourish
as well as to minister to the functions of
the organ. Having entered the cavernous
mass, they ramify in the trabecular structure.
The arteries of the corpora cavernosa are
offsets of the pudic ; the chief branch {artery
of the corpus cavernosum ; p. 251) enters at
the crus, and runs forwards through the
middle of the cavernous structure, distri-
buting offsets ; and the rest, coming from
the dorsal artery (p. 251), pierce the fibrous
case along the dorsum of the penis.

In the interior they divide into branches,
which ramify in the trabeculae, becoming
finer, until they terminate in very minute
branches, which open into the intertrabe-
cular venous spaces. By the distension of
these spaces the erection of the corpora
cavernosa is produced.

The veins spring from the intertrabecular
spaces, and some issue along the upper and
under aspects of the penis to join the
dorsal vein ; but the principal trunks escape at the crus penis and
pass to the pudic veins.

Corpus spongiosum URETHRiE. This constituent part of the
penis surrounds the urethra, but not equally on all sides ; for at
the bulb only a thin stratum is above the canal, while at the glans
penis (fig. 154, I) the chief mass is placed above the urethral tube.
Structure. The tissue of the corpus spongiosum is similar to
that of the corpus cavernosum ; thus it consists of a fibrous tunic
enclosing a trabecular structure with blood-spaces.

The fibrous covering is less dense and strong than in the corpora
cavernosa, and consists only of circular fibres. A

Fia. 155. — Pectiniform
Septdm of the Penis.

a. Apertures in the
partition.

h. Separate fibrous
processes hke the teeth
of a comb, which are
formed by the circular
fibres.

THR RECTUM. 417

projects inwards from it in the middle line, opposite the tube of the imperfect
urethra ; this is best marked for a short distance in front of the septum;
bulb, and assists in dividing that part into two lobes. The trahe-
cuiar bands are much finer, and more uniform in size than in the trabeculae.
corpora cavernosa.

Blood-vessels. The arrangement of the blood-vessels in the Blood-
erectile structure of the corpus spongiosum is similar in the bulb ^'®^^®^^ •
to that in the corpora cavernosa ; but in the rest of the spongy-
substance the arteries are said to end in capillaries in the usual way.

The arteries are derived from the pudic on each side ; a large source of
one behind, the artery of the hulb (p. 251), enters the upper surface *'^"^^'
of the Ijulb ; and several in front, offsets of the dorsal artery of the
penis, penetrate the glans. Kobelt describes another branch to the
fore part of the bulb.

Most of the vei7is, including those of the glans, end in the large termination
dorsal veins of the penis, some communicating with veins of the °^ *^® veins,
cavernous body ; others issue from the bulb, and terminate in the
pudic vein.

Nerves and lymphatics. The nerves of the penis are large, and Nerves,
are supplied, as previously described, by both the spinal and
sympathetic nerves. The superficial lymphatics of the integuments. Lymphatics,
and those beneath the mucous membrane of the urethra, join the
inguinal glands ; the deep accompany the veins beneath the
subpudic arch, to end in the lymphatic glands in the pelvis.

THE RECTUM.

Dissection. The rectum is to be washed out and then distended To prepare
with tow, and the peritoneum and the loose fat are to be removed ^ ^^ '
from it.

This portion of the intestine is about five inches in length. Its Rectum:
lower half is commonly dilated, especially in old people, and the length;
anal canal in which it terminates is the narrowest part of the large dimensions ;
bowel. It is sacculated, although not so distinctly as the colon ; the saccuii.
pouches are arranged in two rows, right and left, and they become
larger and less numerous towards the lower end.

Structure. The rectum contains in its wall a peritoneal, a same coats
muscular, a submucous, and a mucous stratum ; and the muscular ^^ 1" ^\l
and mucous coats have certain characters which distinguish this intestine :—
part of the intestinal tube.

The peritoneum forms but an incomplete covering, and its Peritoneum,
arrangement is referred to in the description of the relations of the
pelvic viscera (p. 386).

The muscular coat consists of two layers of pale or unstriated Muscular
fibres, viz., a superficial or longitudinal, and a deep or circular.
The longitudinal fibres are mainly collected into anterior andhaslongi-
posterior bands, which spread out and increase in thickness below : ^^^^^^^
the anterior band is the broader, and is formed by the union of two
of the bands of the colon, while the posterior is the continuation of
the band lying along the attached border of the colon. These

D.A. E E

418 DISSECTION OF THE PELVIS.

bands are shorter than the other strata of the wall, and thns give
and circular rise to the sacculations. The circular fibres describe arches around
^^^' the intestine, and become thicker and stronger towards the anus,

where they are collected along the anal canal into the Imnd of the
internal sphincter muscle (p. 240).
Mucous The mucous coat is more moveable than in the colon, and resemliles

tv V^ d "^ ^^^^^ respect the lining of the oesophagus ; it is also thicker and
vascular; more vascular than in the rest of the large intestine,
folds in it. When the bowel is contracted the mucous lining is thrown into
numerous accidental folds, for the most part transverse or oblique ;
but in the anal canal they are longitudinal, enclosing submucous
Permanent muscular fibres, and form the columns of Morgagni. There are also
o?reVtum^^^ permanent transverse folds of the intestinal wall {Rectal valves)
corresponding to the depressions between the sacculi externally. The
" Rectal largest and most regular of these are in the lower portion of the gut,
va ves. ^^^ being on the right side and front about three inches from the

anus, and corresponding approximately to the spot where the recto-
vesical pouch of peritoneum ends, another on the left side about
one inch higher, and a third, which is less constant, on the left side
posteriorly, below the first. These folds will be seen by laying
open the gut along the front, provided it is tolerably fresh,
structure of The mucous membrane has the same general structure as in the

colon, but towards the anus the secretory apparatus disappears.

Arteries: Blood-vessels. The arteries are supplied from three diflferent

sources, viz., superior haemorrhoidal of the inferior mesenteric,

middle heemorrhoidal of the internal iliac, and inferior hasmorrhoidal

of the internal pudic. All three sets anastomose on the lower end

of the gut ; but only the upper hsemorrhoidal, which is the largest,

an-angement requires notice here. The final branches of this artery, about six in

hLrnor"°'^ number, pierce the muscular layer three inches from the anus, and

rhoidai. descend between the mucous and muscular coats as far as the

internal sphincter, where they unite in loops just within the anus.
Veins are The vei7is have no valves, and communicate freely in a large

valves! plexus (hcemorrhoidal) between the muscular and mucous coats,
round the lower end of the gut. Above they join the inferior
mesenteric vein, and through it reach the vena portae ; and below
they pour some blood into the internal iliac vein by the middle and
inferior haemorrhoidal branches.
Nerves. Nerves and lymphatics. The nerves of the intestine are obtained

from the sympathetic ; but those of the external sphincter come
Lymphatics, from the spinal nerves. The lymphatics terminate in the chain of
glands on the sacrum.

Section III.

ANATOMY OF THE FEMALE PELVIC VISCERA.

To remove Dlssectloil. In the case of the female pelvis, the bladder, urethra,
e viscera, ^-^^ genital organs and the rectum are to be removed together for

THE VAGIXA. 419

separate examination. For this purpose the student should keep the
scalpel close to the osseous boundary of the pelvic outlet, so as to
avoid injuring the end of the rectum ; and he should also detach the
crus of the clitoris from the bone.

After the parts are taken from the body, the rectum is to be and prepare
separated from the uterus and the vagina, but the rest of the viscera *^®™-
may remain united until after the genital organs are examined.
The bladder and rectum may be moderately distended ; and the fat
and areolar tissue are to be removed from the viscera.

GENITAL ORGANS.

The genital organs, or external organs of generation, consist of External
the following parts : — the mons Veneris and external labia, the gyration
clitoris and internal labia, and the vestibule with the meatus
urinarius ; they have been seen in the dissection of the perineum
(p. 255 et seq.). "Within the internal labia is the aperture of the
vagina, with the hymen. The name vulva or 'pudendum is applied
to these parts as a whole.

GENERATIVE ORGANS.

The generative organs, or internal organs of generation, are the Separate
uterus and vagina, and the ovaries with the Fallopian tubes. utlrus -^"^

Dissection. The viscera are now to be separated, so that the
bladder and the urethra may be together, and the vagina and the
uterus remain united. The bladder is to be set aside for subsequent
examination. The surface of the vagina and the lower part of the clean
uterus should be cleaned ; but the peritoneal investment of the ^'*g'°*-
latter is to be left untouched for ihe present.

THE VAGINA.

The general relations of the vagina have been described on Vagina :
page 394. The tube of the vagina (fig. 146, p. 391), is con- ®''*^"*
nected with the uterus at one end, and with the vulva at the other, and curved
It has a slightly curved course between the two points mentioned ; ^*^*"^^ •
and the anterior and posterior walls are not equal in length, for the
former measures about two inches, and the latter three.

In the body the vagina is flattened from before backwards, so form
that the opposite surfaces are in contact ; and the upper part of the
posterior wall is applied to the lower end of the uterus. Its size and size,
varies at different spots ; — thus the external orifice, which is sur-
rounded by the constrictor vaginae muscle, is the narrowest part ;
the middle portion is the largest; and the upper end is intermediate
in dimensions between the other two.

After the vagina has been laid open by an incision along the side, interior,
the position of the uterus in the anterior wall, instead of at the
extremity of the passage, may be remarked ; and the tube may be
seen to extend farther on the posterior than on the anterior lip of the

EE 2

420

DISSECTION OF THE PELVIS.

has columns
and rugae.

Thickness,

Three coats :

mucous,
muscular,
and fibrous ;

also erectile
tissue.

Mucous
membrane.

Arteries.

Veins are
plexiform.

Nerves.
Lymphatics,

OS uteri. On the inner surface, towards the lower part, is a longi-
tudinal ridge both in front and behind, named columns of the vagina.
Before the tissue of the vagina has been distended, other transverse
ridges or rugse pass between the columns. The wall of the vagina
is thicker in front round the urethra than at any other part of the
canal.

Structure. The vaginal wall has a muscular coat, composed of un-
striped fibres both longitudinal and circular, which is thin above,
and increases in thickness below. It is lined internally by mucous
membrane, and covered externally by a layer of connective tissue
containing a dense network of veins. The prominence of the
columns is mainly due to a collection of vascular cavernous tissue
between the mucous and muscular layers.

The mucous membrane is continued through the lower aperture to
join the integument on the labia majora, and through the os uteri,
at the opposite end, to the interior of the uterus. Many mucous
glands open on the surface, especially at the upper part.

Blood-vessels and nerves. The arteries are derived from the vaginal
and uterine branches of the internal iliac. The veins form a plexus
around the vagina, as well as in the genital organs, and open into
the internal iliac vein. The nerves are derived from the pelvic
plexuses, as described on page 404.

The lymphatics accompany the blood-vessels to the glands by the
side of the internal iliac artery.

Uterus;

form;

dimensions ;

upper end ;

the lower
end is
small, and
has an
opening ;

neck;

THE UTERUS.

The uterus or womb is formed chiefly of unstriated muscular
fibres. Its office is to receive the ovum, and to contain the
developing foetus.

This viscus in the virgin state is somewhat pear-shaped, the body
being flattened (fig. 146 and fig. 156, p. 422), and the narrow end
below.

Before impregnation the uterus measures about three inches in
length, two in breadth at the upper part, and an inch in greatest
thickness. Its weight varies from an ounce to an ounce and a half.
But after gestation its size and volume always exceed the measure-
ments here given.

The upper end is convex, and is covered by peritoneum : the
name fundus is given to the part of the organ aliove the attachment
of the Fallopian tubes.

The lower end is small and rounded, and in it is a transverse
aperture of communication between the uterus and the vagina,
named os uteri externum: its margins or lips (labia) are smooth,
and anterior and posterior in situation, but the hinder one is the
longer and thinner. Towards the lower part the uterus is con-
stricted ; and the smaller portion is called the neck (cervix uteri ; h) ; it
is nearly an inch in length, and gradually tapers towards the extremity,
where it projects into the vagina, being enclosed by this tube to a
greater extent behind than in front.

ANATOMY OF THE UTERUS. 421

The body (a) of the iitenis is more convex posteriorly than ante- body;
riorly, and decreases in size down to the neck. It is covered on
both aspects by the peritoneum, except at the lower part in front
(about half an inch), where it is connected to the ' bladder. To parts
each side the parts contained in the broad fold of the peritoneum gldt^^^ ^
are attached (p. 391), viz., the Fallopian tube at the top, the
round ligament rather below and before the last, and the ovary
and its ligament below and behind the others.

Dissection. To examine the interior of the uterus, a cut is to Open the
be made along the front from the fundus to the external os uteri ; "^enis.
and then some of the thick wall is to be removed on each side of
the middle line to show the contained cavity (fig. 156).

The thickness of the uterine wall is greatest opposite the middle its thick-
of the body. It is greater at the centre than at the extremities of "^^*
the fundus, the wall becoming thinner towards the attachment of the
Fallopian tubes.

Interior of the uterus. Within the uterus is a small space, in the
v.hich is divided artificially into two — that of the body, and that
of the neck.

The space occupving the body of the viscus (c) is triangular in is a trian-
form, and compressed from before backwards. Its base is at the in the body,
fundus, where it is convex towards the cavity, and the angles are
prolonged into the FaUopian tubes. The apex is directed down- which is
wards, and joins the cavity in the neck by a narrowed circular below ;
part, or isthmus {os uteri internum) which may be narrower than
the opening of the uterus into the vagina.

The space within the neck (d) terminates below at the external os and a
uteri, and is continuous above with the cavity within the body. It is shaped'
larger at tlie middle than at either end, being spindle-shaped, and jpace in
is somewhat flattened like the cavity of the body. Along both the
anterior and the posterior wall is a longitudinal ridge ; and other
ridges (rugce) are directed obliquely from these on each side : this
appearance has been named arbor vitce uterinus. In the intervals in the neck
between the rugae are mucous follicles, which sometimes become ^bo"vfto.°
distended with fluid, and give rise to rounded clear sacs.

Structure. The dense wall of the uterus is composed of layers uterus is a
of unstriated muscular fibre, intermixed with areolar and elastic ^1^*! ^
tissues and large blood-vessels. On the exterior is the peritoneum ;
and lining the interior is a thin mucous membrane.

The muscular fibres can be demonstrated at the full period <^f JJf '^ t'^®!^
gestation to form three strata in the wall of the uterus, viz.,
external, internal, and middle : —

The external layer contains fibres which are mostly transverse ; external,
but at the fimdus and sides they are oblique, and are more marked
than along the middle of the organ. At the sides the fibres con-
verge towards the broad ligament ; some are inserted into the
subperitoneal fibrous tissue ; and others are continued into the
Fallopian tube, the round ligament, and the ligament of the ovary.

The internal fibres describe circles round the openings of the internal.
Fallopian tubes, and spread from these apertures till they meet at

422

DISSECTION OF THE PELVIS.

and middle.

Mucous
membrane.

Vessels are
large.

Arteries.
Veins.

the middle line. At the neck of the uterus they are arranged in a
transverse direction.

The middle or intervening set of fibres are more indistinct than
the others, and have a less determinate direction.

The mucous lining of the uterus is continued into the vagina at
one end, and into the Fallopian tubes at the other. In the body it
is thin and soft, of a reddish-white colour, smooth, and closely
adherent. In the cervix it is stronger, and presents the folds before
referred to.

The blood-vessels of the uterus are large and tortuous, and occupy
canals in the uterine substance in which they communicate freely
together. The arteries are furnished from the uterine, vaginal and
ovarian vessels (p. 398 et seq.) and the veins correspond with the

FiQ. 156. — Interior op the Uterus, with a Posterior View of the
Broad Ligament and the Uterine Appendages.

a. Body, and b, neck of the uterus.

c. Cavity of the body, and d, of
the neck.

e. Fallopian tube, and /, its
trumpet-shaped end.

g. The fimbria attached to the
ovary.

h. Ovary.

i. Ligament of the ovary.

k. Parovarium.

Nerves.

Lympha-
tics ;
two sets.

Round liga-
ment ends
in groin ;

attachment
to uterus,

arteries ; they are of large size, and form ^^lexuses in the uterus,
which communicate with the vaginal plexus on the one hand and
the ovarian on the other.

The nerves are derived from the sympathetic (p. 405), and are
very small in proportion to the size of the uterus.

Lymphatics. One set accompanies the uterine vessels to the glands
on the iliac artery. Another set issues from the fundus, enters the
broad ligament, and accompanies the ovarian artery to the glands
on the aorta : the last are joined by lymphatics of the ovary and
Fallopian tube.

Round ligament of the uterus (p. 394). This firm cord supports
the uterus, and is contained partly in the broad ligament, and
partly in the inguinal canal. It is about five inches in length,
and is attached to the upper end of the uterus close below and in
front of the Fallopian tube. A process of the peritoneum

STRUCTURE OF OVARY. 423

accompanies it in the inguinal canal, and remains pervious sometimes
for a short distance.

The ligament is composed of unstriated muscular fibres, derived how formed,
from the uterus, together with vessels and areolar tissue.

OVARIES AND FALLOPIAX TUBES.

Ovary (fig. 156, h). The ovaries are two bodies, corresponding Ovary:
with the testes of the male. They are contained in the broad liga- P^^*^^^'^'
ments of the uterus, one in each.

Each ovary is of an oval form, and somewhat compressed in one form and
direction. It is of a whitish colour, with either a smooth or a
scarred surface. Its volume is variable ; but in the virgin state it
is about one inch and a half in length, half as much in width, and dimensions
a third of an inch in thickness. and weight.

Its weight varies from one to two
drachms.

The ovary is placed at the back of
the broad ligament, and is attached
to that membrane by one margin,
where the vessels enter the organ at
the hilum. The other margin and
both surfaces are free. One end
(the upper in the natural position)
is rounded, and is connected with
one of the fimbriae (g) at the mouth
of the Fallopian tube. The opposite P^«; 1o7.-Uvary during the
.^ . 1 T • n 1 Child-bearing Period Laid

extremity is narrowed, and is nxed Open (Farre)

to the side of the uterus bv a fibrous ^ . • i • ,.«f

, ^, 1 . ^ c ^\. " / '\ *• Grraanan vesicles in different

cord,— the ligament of the ovary (i), ^^gg^, ^^ ^^^^^

below the level of the Fallopian tube b. Plicated body remaining
and round ligament. after the escape of the ovum.

Structure. The ovary consists of Structure

a stroma enclosing small sacs named Graafian vesicles, which con-
tain the ova, and the whole is surroimded by a fibrous tunic.
The peritoneum invests it except at the attached margin.

The fbrous coat is continuous with the contained stroma. Some- a fibrous
times a yellow spot (corpus luteum), or some cicatrices, may be seen ^ '
in this covering.

Stroma (fig. 157). The substance of the ovary is spongy, vascu- stroma;
lar, and fibrous. At the centre the fibres radiate from the hilum
towards the circumference. But at the exterior is a granular
material (cortical layer) which contains very many small follicles,
about y^th of an inch in size — the nascent Graafian vesicles.

The Graafian vesicles or ovisacs (fig. 157) are round and transparent Graafian
sacs, containing fluid, and scattered through the stroma of the ovary * ^'
below the cortical layer. During the child-bearing period some
are larger than the rest (a) ; and of this larger set ten to thirty, number
or more, may be counted at the same time, which vary in size
from a pin's head to a small pea. The largest are situate at the

424

DISSECTION OF THE PELVIS.

Shedding of
an ovum :

corpus
luteum.

Artery ;

circumference of the organ, and sometimes they may he seen
projecting through the fibrous coat.

When the Graafian vesicle is matured it bursts on the surface of
the ovary, and the contained ovum escapes into the Fallopian tube.
After the shedding of the ovum the ruptured vesicle gives origin
to a yellow substance, corpus luteum, which finally changes into a
cicatrix (&).

Blood-vessels and nerves. The ovarian artery pierces the ovary at
the attached border, and its branches run in zigzag lines through
the stroma, to which and the Graafian vesicles they are distributed.
The veins begin in the texture of the ovary, and after escaping
from its substance, forms a plexus {'pampiniform) within the fold of
the broad ligament. The nerves are derived from the sympathetic
on the ovarian and uterine vessels.

Appendage
to ovary :

situation :
form;

structure.

Parovarium or organ of Rosenmuller {epoophoron of Waldeyer ; fig. 156 h).
On holding up the broad ligament of the uterus to the light, a collection of
small tortuous tubules will be seen between the ovary and the Fallopian tube.
These are the remains of the upper part of the Wolffian body of the foetus, and
correspond to the vasa efferentia of the testicle in the male. The mass is
about one inch broad, with its base to the Fallopian tube and its apex towards
the attached border of the ovary. The small tubes are from twelve to twenty
in number ; at the wider end they are joined more or less perfectly by a tube
crossing the rest (the remnant of the Wolffian duct), which is prolonged some-
times a short way into the broad lignment.

Fallopian
tube :

length ;

and form ;

it is dilated
externally,

and fimbri-
ated;

size of the
canal is
least at the
ends.

A muscular
structure ;

fibres pro-
longed from
litems.

Mucous
coat

Fallopian tubes (fig. 156, e). Two in number, one on each
side, they convey the ova from the ovaries to the uterus.

Each is about four inches in length ; cord-like at the inner end,
where it is attached to the upper part of the uterus, it increases in
size towards the outer end, and terminates in a wide extremity (/),
like the mouth of a trumpet. This dilated end is fringed, and the
pieces are called fimhrice. When the fimbriated end is floated out
in water, one of the processes (the ovarian fimbria ; g) may be
seen to be fixed to the distal end of the ovary. In the centre of
the fimbria is a groove leading to the orifice of the Fallopian
tube.

On opening the tube with care, the size of the contained space
and its small aperture into the uterus can be observed. Its canal
varies in size at diff'erent spots ; the narrowest part is at the orifice
into the uterus (ostium uterinum), where it scarcely gives passage
to a fine bristle ; towards the outer end it increases a little, but it
is rather diminished in diameter at the outer aperture (ostium
abdominale).

Structure. This tube has the same structure as the iiterus with
which it is connected, viz., a muscular layer covered externally by
peritoneum, and lined by mucous membrane.

The muscular coat is formed of an external or longitudinal, and
an internal or circular layer ; both these are continuous with similar
strata in the wall of the uterus.

The mucous membrane forms longitudinal folds, particularly at the
outer end. At the inner extremity of the canal it is continued

BLADDER AMD URETHRA IN FEMALE. 425

into the mucous lininff of the uterus, but at the outer end it joins »s continu-
, . ° ' *" ous with

the peritoneum. peritoneum.

The blood-vessels and nerves are furnished from those supplied to Vessels,
the ovary and uterus.

THE BLADDER, URETHRA, AND RECTUM,

Bladder, The peculiarities in the form of the female bladder Anatomy of
have been detailed in the description of the relations of the viscera *<^"®'^-
of the female pelvis (p. 394). For a notice of its structure, the
anatomy of the male bladder is to be referred to (p. 409).

Dissection. To prepare the bladder, distend it with air, and Preparation
remove the peritoneal covering and the loose tissue from the ° ' '
muscular fibres.

After the external anatomy of the bladder and urethra has Ijeen open it.
learnt, they are to be slit open along the fore part, as described in
the dissection of the male parts.

Urethra. The length and the relations of the urethra are Urethi-a:
given at p. 395. ^'°sth;

The average diameter of the urethra is rather more than a quarter size ;
of an inch, and the canal is enlarged and funnel-shaped towards
the neck of the bladder ; near the external aperture is a hollow in
the floor. In consequence of its not being surrounded by resistant it can be
structures, the female urethra is much more dilatable than the dilated,
corresponding passage in the male.

Structure. Like the urethra of the male, it consists of a mucous Tube like
coat, which is enveloped by a plexus of blood-vessels, and by maie.^'^
muscular fibre.

The muscular layer extends the whole length of the urethra. Its Muscular
fibres are circular, corresponding with those in the prostatic enlarge- cSiar*tibres.
ment of the other sex, and continuous above with the middle layer
of the bladder. In the perineal ligament this stratum is covered
by the fibres of the deep iTansverse muscle.

The mucous coat is pale except near the outer orifice. It is Mucous
marked by longitudinal folds ; and one of these, in the floor of the ^^ '
canal, resembles the median crest in the male urethra (p. 412). the floor;
Around the outer orifice are some mucous follicles ; and towards the fouicies and
inner end are tubular mucous glands, the apertures of which are glands,
arranged in lines between the folds of the membrane.

A submucous stratum of longitudinal elastic and muscular tissues Submucous
lies close beneath the mucous membrane, as in the male. tissue.

Dissection. The rectum may be prepared for examination by Preparation
distending it with tow, and by removing the peritoneal covering ° ^^ "™"

and the areolar tissue from its surface. Its structure is similar in Rectum like
the two sexes ; and the student may use tKe description in the niaie.°
Section on the viscera of the male pelvis (p. 417 et seq.).

INTERNAL MUSCLES AND LIGAMENTS OP THE PELVIS.

Two muscle*, the pyriformis and obturator intemus, have theu- Two
origin within the cavity of the pelvis.

426

DISSECTION OF THE PELVIS.

Define the
muscles

and the
levator ani.

Pyriformis

origin in
the pelvis ;

relations
with parts
around ;

use as an
external
rotator of
hip-joint.

Obturator
Internus

is bent over
ischium ;

origin in
the pelvis ;

arching of
its tendons
over the
hip-bone;

insertion ;

relations of
part in
pelvic
cavity ;

Coccygeus
muscle.

Dissection. Take away any fascia or areolar tissue which may
remain on the muscles ; and define their exit from the pelvis, — the
pyriformis passing through the great, and the obturator through the
small sacro-sciatic foramen. On the right side the dissector may
look to the attachment of the levator ani muscle to the pubic part
of the hip-hone.

The PYRIFORMIS MUSCLE is directed outwards through the great
sacro-sciatic foramen to the great trochanter of the femur. The
muscle has received its name from its form.

In the pelvis the pyriformis arises by three slips from the second,
third, and fourth pieces of the sacrum, between and external to the
anterior sacral foramina ; as it passes from the pelvis, it takes origin
also from the surface of the hip-bone forming the upper boundary
of the large sciatic notch, and from the great sacro-sciatic ligament.
From this origin the fibres converge to the tendon of insertion into
the great trochanter of the femur.

The anterior surface is in contact with the sacral plexus, with the
sciatic and pudic branches of the internal iliac vessels, and with
the rectum on the left side. The opposite surface rests on the
sacrum, and is covered by the great gluteal muscle outside the
pelvis. The upper border is near the hip-bone, the gluteal vessels
and the superior gluteal nerve being between ; and the lower border
is contiguous to the coccygeus muscle, the sciatic and pudic vessels
and nerves intervening.

Action. The pyriformis belongs to the group of external rotators
of the hip-joint ; and its use has been given with the description of
the rest of the muscle in the dissection of the buttock (p. 1 1 7).

The OBTURATOR INTERNUS MUSCLE has its Origin in the pelvis, and
insertion at the great trochanter of the femur, like the preceding ;
but the part outside forms an acute angle w4th that inside the pelvis.

The muscle arises by a broad fleshy attachment from the obturator
membrane, except from a small part below, from the pelvic fascia
covering its surface, slightly from the bone anterior to the thyroid
hole and from all the smooth inclined surface of the pelvis (fig. 139,
p. 369) behind and above that aperture except opposite the small
sacro-sciatic foramen where a thin layer of fat separates the fleshy
fibres from the bone. The fibres are directed backwards and down-
wards, and end in four or five tendinous pieces, which turn over
the edge of the hip-bone corresponding with the small sciatic notch.
Outside the pelvis the tendons blend into one, which receives the
fibres of the gemelli and is inserted into the upper border of the
great trochanter of the femur.

The muscle is in contact by one surface with the wall of the
pelvis and the obturator membrane ; by the other surface with the
obturator part of the pelvic fascia, and towards its lower border
with the pudic vessels and nerve.

Action. The muscle is chiefly an external rotator of the femur
(p. 123).

Coccygeus muscle. The position and the relations of this muscle
may now be studied from within : it is described on p. 381.

ARTICULATIONS OF THE SACRUM. 427

Section IY.

LIGAMENTS OF THE PELVIS.

The sacrum is joined at its base to the last lumbar vertebra, at Outline of
its apex to the coccyx, aud laterally to the two hip-bones. And the fatlons!^'^'
hip-bones are connected together at the symphysis pubis in front.

UXIOX OF PIECES OF THE SACRUM ASD COCCYX. So long aS Ligaments

the pieces of the sacrum and coccyx remain moveable they are ^^^^
articulated as in the other vertebrse by an anterior and a posterior
common ligament, with an intervertebral disc for the bodies, and •
by ligaments for the neural arch and processes.

After the sacral vertebrae have coalesced, only rudiments of the and joined.
ligaments of the bodies are to be recognised ; and when the pieces
of the coccyx unite by bone, their ligaments disappear.

LUMBO-SACRAL ARTICULATION. The base of the sacrum is Sacmm

articulated with the last lumbar vertebra by ligaments similar to i^bar^^
those uniting one vertebra to another (pp. 492 et seq.) ; and by one vertebra,
special ligament — the lateral lumbo-sacral.

Dissection. For the best manner of bringing these different Dissection,
ligaments into view, the dissector may consult the directions given
for the dissection of the ligaments of the vertebrse (pp. 492 et seq.).

The common ligaments for the bodies of the two bones are an By liga-
anterior and a posterior, with an intervening fibrocartilaginous sub- ™^other^
stance. Between the neural arches lie the ligamenta subflava, and vertebne,
between the spines the supra- and int^rspinous bands. The articular
processes are united by capsular ligaments with synovial membranes.

The lateral lumbosacral ligament is a variable bundle of fibres, and by a
which reaches from the under surface of the tip of the transverse li^^^i
process of the last lumbar vertebra to the lateral mass at the base ^'^^'l-
of the sacrum. Widening as it descends, the ligament joins the
fibres in front of the sacro-iliac articulation.

Sacro- COCCYGEAL ARTICULATION. The sacrum and coccyx are Union of
united at the centre by a fibro-cartilage, and by an anterior and S^cyx.
a posterior ligament. There are also lateral and interarticular
ligaments on each side.

Dissection. Little dissection is needed for these ligaments. Dissection.
"When the areolar tissue has been removed altogether from the
bones, the ligaments will be apparent.

The anterior ligament (sacro-coccygeal) consists of a few fibres that An anterior
pass between the bones in front of the fibro-cartilage.

The 'posterior ligament is wide at its attachment to the margin of a posterior
the lower opening of the sacral canal, but narrows as it descends ^*^™®°*'
to be inserted in the coccyx.

The jihro-cartilage resembles that between the bodies of the other with a fibro-
vertebne, and is attached to the surfaces of the bones. cartUage.

Interarticular ligaments. The cornua of the sacrum and coccyx A band
do not usually form joints, but are united by a ligamentous band ^^S,
on each side.

428

DISSECTION OF THE PELVIS.

and trans-
verse pro-
cesses.

Motion.

Sacro-sciatic
ligaments
are two :

great,

and small ;

apertures
formed by
them;

Iliolumbar
ligament :

The lateral ligament j)asses on each side between the projections
representing the transverse processes of the last sacral and first
coccygeal vertebrse.

Movement. While the coccyx remains unossified to the sacrum,
a slight antero-posterior movement will take place between them.

Two SACRO-SCIATIC LIGAMENTS pass from the side of the sacrum
and coccyx to the hinder border of the hip-bone, across the space
between those bones at the back of the j^elvis : they are named
great and small.

The great or 'posterior ligament (fig. 158, a) is attached above to
the posterior infeiior iliac spine, and to the side of the sacrum and
coccyx ; and below to the inner margin of the ischial tuberosity,
sending forwards a prolongation {falciform process) along the ramus

of the ischium. It is wide at
the sacrum, and gets narrower
towards the lower end ; but
it is somewhat expanded again
at the tuberosity.

The small or anterior liga-
ment (fig. 158, 6) is attached in-
ternally by a wide piece to
the border of the sacrum and
coccyx, where it is united with
the origin of the preceding
band. The fibres are directed
outwards, and are inserted as
a narrow band into the ischial
spine of the hip-bone. Its
deep surface is blended with
the coccygeus ; and it may be
looked upon as being a fibrous
portion of that muscle. Above
it is the large sacro-sciatic
foramen ; and below it is the
small foramen of the same
name, which is bounded by the two ligaments.

By their position these ligaments convert into two foramina
(sacro-sciatic) the large sacro-sciatic excavation in the dried bones :
the openings, and the structures they give passage to, have been
described with the buttock (p. 124).

Use. The sacro-sciatic ligaments, by holding down the lower
part of the sacrum, serve to jirevent that bone from rotating at the
ptcro-iliac articulation, under the influence of the weight pressing
on its upper end in the erect position.

The iLio-LDMBAR LIGAMENT is a strong triangular liand, which
springs by its narrow end from the extremity of the transverse
process of the fifth lumbar vertebra. Directed outwards and some-
what backwards, it spreads out to be inserted into the iliac crest for
ab^out an inch, opposite the back part of the iliac fossa. To the
upper border of the ligament the anterior layer of the fascia

Fig. 158. — Sacro-sciatic Ligaments.
a. Large, and i, small.

THE 8ACR0-ILIAC LIGAMENTS. 429

lumborum is attached ; and its posterior surface is covered by the
quiidratus lumborum.

Use. This ligament supports the upright moveal)le portion of use.
the spinal column, and resists the tendency of the last lumbar
vertebra to slip forwards over the inclined base of the sacrum.

Sacro-iliac articclatiox. The irregular surfaces by which union of
the sacrum and the hip-bone articulate are co\*ered with cartilage, ^^'bone'^*^
and are maintained in contact by anterior and posterior sacro-iliac
ligaments. Inferiorly the bones are further connected, without
being in contact, by the strong sacro-sciatic ligaments.

Dissection. To see the posterior ligaments, the mass of muscle To dissect
at the back of the sacrum is to be removed on the side on which ^entf^
the hip bone remains. The thin anterior bands will \)e visible on
the removal of some areolar tissue. The small sacro-sciatic ligament
will be brought into view by ^emo^'ing the fleshy fibres of the
coccygeus ; and the large ligament has been dissected with the
lower limb.

The anterior saci'o-iliac ligament consists of a few thin scattered Anterior
fibres between the bones, near their articular surfaces. ligament.

The posterior sacro-iliuc ligament is very strong, and consists of Posterior
bundles of fibres which pass obliquely from the rough part of the ligament:
inner side of the ilium above the auricular surface to the depressions
on the back of the first and second pieces of the sacrum. A distinct
band, longer and more superficial than the rest, runs from the a special
posterior superior iliac spine to the third and fourth pieces of the ^°°^ ^^^'
sacrum ; it is named the long posterior ligament.

Articular cartilage. This maybe seen after the sacro-sciatic and A layer of
ilio-lumbar ligaments have been examined, by opening the articula- 2ch bone?'^
tion and separating the bones. It covers the articular surfaces of
both sacrum and iliimi, but is much thicker on the sacriun. Its
surface is generally uneven ; and the intermediate cleft is some-
times partly interrupted by transverse fibres uniting the two layers.

Mechanism. There is scarcely any appreciable movement in this Use of joint
articulation, owing to the tightness with which the two bones are ^^
bound together by ligaments, and the irregular form of the articular
surfaces, which are consequently unable to glide over one another.
In the erect posture the sacrum is suspended between the two hip- to render
bones by the thick posterior sacro-iliac ligaments, and the upper ^astfc.
arch of the pelvis is thereby rendered less rigid than would be the
case if it were formed of continuous bone. The sacro-iliac articula-
tion thus serves to give elasticity to the pelvis, and to diminish the
effect of shocks passing to the spine.

Pubic articulation (symphysis pubis ; fig. 159, a). The two Symphysis
pubic bones are united by an interpubic disc, by ligamentous fibres ^^ ^^'
in front and above, and iDy a strong subpubic ligament.

The anterior piihic ligament is composed of interlacing fibres Anterior
which are mixed with fibres of the tendon of the external oblique ^'^*™®" "
muscle.

There is not any definite posterior band ; but the periosteum is Few fibres
thickened by a few scattered fibres.

430

and above.

Subpubic
ligament.

How to
show disc.

DISSECTION OF THE PELVIS.

The superior ligamentous fibres fill the interval between the bones
above the disc.

The subpubic ligament (ligamentum arcuatum ; fig. 159, d) is a
strong triangular band occupying the angular interval between
the pubic rami at the lower part of the symphysis. Its apex is
continuous with the fibrous portion of the interpubic disc ; its
base is free and concave, and forms the summit of the subpubic
arch.

Dissection. The disc will be best seen by making a transverse

Fig. 159. — Ligaments op the Symphysis Pubis, Thyroid Foramen,
AND Acetabulum.

a. Anterior ligament of the sym-
physis.

b. Obturator membrane.

c. Interpubic disc, with a slit in
the middle.

d. Subpubic Hgament.

e. Surface of the acetabulum
covered with cartilage.

/. Fatty substance in the aceta-
bulum ( " gland of Havers ")•

g. Cotyloid ligament, which is cut
where it forms part of the transverse
band over the notch.

h. Deep part of the ligament over
the cotyloid notch.

Interpubic
disc:

cleft in it.

section of the bones, which will show the disposition of the anterior
ligament of the articulation, and the thickness of the plate, with its
toothed mode of attachment to the bone ; and when another
opportunity offers, a vertical section may be made.

The interpubic disc consists of a layer of cartilage on each side,
which is firmly adherent to the ridged surface of the bone, and a
fibrous portion in the middle. The fibrous part is thickest in
front ; and at the upper and back portion of the symphysis there
is generally a fissure, produced by the absorption of the fibrous

INTERPUBIC DISC. 431

substance. In some bodies tbe fissure extends through the whole
of the disc, so as to divide it completely into two.

The thin obturator membrane (fig. 159, 6) almost closes Obturator
the thyroid foramen, and is composed of fibres crossing in "oses^^
different directions. It is attached to the bony margin of the fP^"J®
foramen, except above where the obturator vessels pass through ;
and at the lower and inner part of the aperture it is connected to
the pelvic aspect of the hip-bone. The surfaces of the ligament
give attachment to the obturator muscles. Branches of the obturator
vessels perforate it.

432

THE ARTERIES OF THE ABDOMEN.

TABLE OP THE ARTERIES OF THE ABDOMEJ^.
^1. Phrenic. . Superior capsular.

2. coeliac axis*

3. superior

mesenteric.

4. middle cap-

sular

5. renal

6. spermatic

7. inferior

mesenteric*

8. lumbar

9. middle sa-

cral*

^Coronary . / Oesophageal

■ (gastric.

I Gastro-duodenal .
hepatic . i pyloric

left hepatic branch
fright hepatic branch

(pancreatic
vasa brevia
left gastro-epiploi'c
splenic.

/ Inferior pancreatico-duodenal

intestinal
■I ileo-colic

right colic
imidde colic.

Inferior capsular.

( Left colic

j sigmoid

I superior liseraoiThoidaL

f Right gastro-epiploTc
■ I superior pancreatico-duodenal.

Cystic.

/ External iliac

10. common
^ iliac .

/ Pubic

{Deep epigastric . J cremasteric
1 muscular
deep circumflex \ cutaneous.
iliac.

f Ilio-lumbar
lateral sacral

/Parietal
' branches.

gluteal . . f Superficial
1 deep.

internal iliac

sciatic

internal pudic

/'Coccygeal
I comes nervi ischia-
.-l dici
I musculari
^anastomotic.

{Inferior hsemor-
rhoidal
superficial perineal
transverse perineal
artery of the bulb
artery of corpus
cavernosum
dorsal artery of penis.

V visceral
branches

^ obturator . , J Iliac
1 pubic.

superior vesical.

inferior vesical.

middle hsemor-
) rhoidal

vaginal
^ uterine.

* The branches marked with an asterisk are single.

VEINS OF THE ABDOMEN.

433

TABLE OF THE VEINS OF THE ABDOMEN.

Visceral
Immches

' Intexnal iliac .\

( 1. Common iliac

eztonal iliac

ilio-lombar
middle sacral
into the left.

parietal
branches.

(Epigastric
, \ circumflex
^ iliac.

2. lorabor

3. right spermatic

4. renal.

h. right capsular

6. diaphragmatic

7. hepatic veins,

which bring
blood from the
s. vena porta.

< Right
\ left .

fCapAolar
t spermatic

Hemorrhoidal
plexus

vesico-prostatic .^^^^
plexus . . I ^^^g^ Qf ^.^jg pg,ji3

uterine

vaginal.

"obturator

pudic .

sciatic

Veins of corpus cavemo-

snm
of the bulb
transverse perineal
superficial perineal
infen(»' haemorrfaoidaL

/coccygeal
. j comes nervi
j muscular
\ anastomotic.

^lateral sacraL

Vena

PORT.*:

Splenic

(Splenic
branches
\-asa brevia
pancreatic
left gastro-
epiploic.

rLeft colic
/Inferior me- I sigmoid
senteric .-. superior
I haemor-
V rhoidal.

intestinal

superior mesenteric -N ileo-colic
right colic
middle colic
right gastro-
epiploic
pancreatico-
\ duodenal.

coronary

pyloric

.cystic.

D. ^.

434

SPINAL NERVES OF THE ABDOMEN.

TABLE OF THE SPINAL NERVES IN THE ABDOMEN.

/Posterior branches .

( Internal

Lumbar

SPINAL
NERVES

divide
into

external

f Muscular
( spinal.

f Muscular
I cutaneous.

'^Ilio-hypogastric. f Iliac branch

1 hypogastric branch.

Anterior branches: of
these the four first/
end in the lumbar'
PLEXUS, which
supplies

ilio-inguinal

genito-crural

external
neous

cuta-

anterior crural

Vobturator .

. J To integuments of
( the groin.

f Genital branch
I crural branch.

j To integuments of
( the thigh.

r Branches inside the f To the iliacus muscle
\ pelvis . . . ( to the femoral artery.

Branches outside the { are noticed in the
I pelvis . . .1 thigh.

Accessory

I Other offsets are
i described in the
^ thigh.

Sacral
spinal

NERVES

divide (
into

/ Posterior branches / Muscular
unite together and and
give off. . ,i cutaneous
[ filaments.

/Terminal
branches

Th e anterior branches
of the four superior
unite with the
lumbo-sacralinthe'

SACRAL PLEXUS,*

and furnish .

Great sciatic . described in the lower limb.

pudic .

f Inferior

haemorrhoidal

perineal

dorsal of penis.

/Superficial,
internal
and

external
muscular

^ to the bulb.

Superior gluteal i

imXcfSf' j"<>t'-<im the lower Itab.

perforating cutaneous
to pyriformis

collateral /
branches .\ ^ obturator internus and superior
\ gemellus
to qiiadratus fenioris and inferior
gemellus ....

visceral
to levator ani
to coccygeus
\to external sphincter.

The other sacral nerves are described at p. 402.

noticed

in the

buttock.

NERVES OF THE ABDOMEN.

435

TABLE OF THE SYMPATHETIC NERVES IN THE ABDOMEN.

^Diaphragmatic

( Pyloric

J right gastro-epiploic
1 pancreatico-duodenal
cceliac . _ . . .-< (cystic.

f Left gastro-epiploic
t pancreatic.
SoLAK Plexus* fiir- 1
nishes the following/ superior mesenteric . Offsets to small and large intestine.

/Coronary plexus
I hepatic .

splenic

plexuses

suprarenal
renal .
aortic .
spermatic
^.inferior mesenteric

* This receives

Spermatic plexus, filaments to the.
Hypogastric.

. f Offsets to the large intestine
t superior haemorrhoidal.

( Great splanchnic nerves
,-! small splanchnic nerves
V offsets of right pneumo-gastric.

Hypogastric Plexus!
ends in the pelvic I vesical
plexus on each side,-/
which gives the fol-
lowing plexuses . . uterine
Vvagiual.

Inferior haemorrhoidal

Gangliated cord of the I
sympathetic in the ab- J

[^ internal

External branches

domen supplies

1 Prostatic
cavernous
deferential
to vesiculfe seminales.

To the lumbar and sacral spinal nerves.

To aortic plexus
to hypogastric plexus
to join round middle sacral artery
between the cords on the coccyx, in the
ganglion impar.

This is joined above by . { Jt°'SZm the lumbar ganglia.

PNEUMO-GASTRIC NERVE IN THE ABDOMEN,

f Right

Pneumo-gastric

left

Coronary branches to the back of the stomach
filaments to join the coeliac and splenic plexuses.

Coronary branches to the front of the stomach,
branches to the hepatic plexus.

P F 2

CHAPTER VIII.
DISSECTION OF THE THORAX.

Section I.

Clean walls
of muscles.

Presence
nerves,

Termination
of the

costal
cartilages.

Form in
general ;

on a cross
section.

THE WALLS OF THE THOEAX.

Dissection. The dissection of the thorax will be commenced
on the fourteenth day of the dissection of the body, after the removal
of the upper limbs.

In the first place the sternum, ribs and costal cartilages with the
intervening structures, will be carefully cleaned, so that the walls of
the chest may be examined, but the lateral and anterior branches
of the intercostal nerves issuing between the ribs and cartilages
should be carefully preserved. The portions of the pectoralis
major and minor, serratus magnus, rectus abdominus, and the ex-
ternal and internal oblique muscles of the abdomen, will be taken
away, at the same time noting again the extent of their attachments ;
the insertion of the scalenus posticus will also be cleaned off the
second rib. The origin of the sub-clavicus from the first costal
cartilage need not be removed. Finally, by arrangement with
the dissectors of the abdomen and head and neck, the body will be
turned on to either side for a few minutes to complete the cleaning
of the ribs and intercostal muscles as far back as the transverse
processes of the vertebrae.

The chest wall. The costal cartilages will now be clearly
seen ; the upper seven ribs join the sternum, the sixth and
seventh being close together at the lower end of the gladiolus, and
the eighth, ninth and tenth cartilages terminate by articulation
with the lower border of the cartilage above. Some distance from
their anterior ends, the seventh, eighth, ninth and tenth cartilages
will be observed to send up a short process to articulate with
a similar one passing downwards from the cartilage above. The
extremity of the eleventh rib cartilage is free, and commonly
forms the lowest point of the chest wall. The twelfth rib is often
not more than two inches or so in length.

Form. The form of the chest is irregularly conical, with the
apex above and the base below ; and it may appear afterwards,
should the student find the lungs collapsed, that it is only partly
filled by the contained viscera, but during life the whole of the space
is occupied by the expanded lungs. It is flattened on the sides, and on

BOUNDARIES AND SIZE. 437

section, the cavity is seen to be diminished in the middle line by the
prominent spinal column, on each side of which it projects backwards.

Boundaries. On the sides are the ribs with the intercostal muscles ; Boundaries,
in front is the sternum ; and behind is the spine.

The base is constructed at the circumference by the last dorsal The
vertebra behind, by the end of the sternum in front, and by the ribs "i*P^rag™>
with their cartilages on each side ; while the space included by the
bones is closed by the diaphragm.

The base is wider transversely than from before backwards, and form of
the diaphragm is convex upwards towards the chest ; though at *" ^^^'
certain spots it projects more than at others. Thus in the centre
it is slightly lower than on each side, and is on a level with the
base of the ensiform process. On the right side, forming a dome
over the liver, it rises to a level with the upper border of the fifth and height:
rib near its junction with the cartilage ; and on the left it arches
over the stomach to the corresponding part of the upper border of
the sixth rib. From the lateral projections, the diaphragm slopes
suddenly towards its attachment to the ribs, but more behind than
before, so as to leave an angular interval between it and the wall of
the chest. The level of the attachment of the diaphragm will be its side
marked by an oblique line, over the side of the chest, from the base
of the ensiform process to the eleventh dorsal spine ; but it diflfers
slightly on the two sides, being rather lower on the left.

The apex of the thoracic cavity is continued higher than the Apex
osseous boundary, and reaches into the root of the neck. Its highest n^^^^ ^°
point is not in the middle line, for there the windpipe, oeso-
phagus, blood-vessels and other structures lie, but it is prolonged on
each side for one or two inches above the anterior end of the first
rib, 80 that the apex may be said to be bifid. Each point projects is bifid:
between the scaleni muscles, and under the subclavian blood-vessels ; how
and in the interval between them lie the several objects passing ^" ® '
between the neck and the thorax.

Dimensions. The extent of the thoracic cavity does not correspond Exterior size
with the apparent size externally ; for a part of the space included cavity? °
by the ribs below is occui^ied by the abdominal viscera ; and the
cavity reaches upwards, as just stated, into the neck.

In consequence of the arched condition of the diaphragm, the Depth
depth of the space varies greatly at difterent parts. At the centre, ^'*"®^ "
where the depth is least, it measures generally from six to seven ^^o''^!
inches, but at the back about half as much again ; and the other \" '
vertical measurements may be estimated by means of the data given ^^ ^^ ®^'
as to the level of the attachment of the diaphragm on the wall of
the thorax.

Alterations in capacity. The size of the thoracic cavity is con- Size is
stantly varying during life with the condition of the ribs and dia- f/fg®. ^°
phragm in breathing.

The horizontal measurements are increased in inspiration, when transversely
the ribs are raised and separated from one another, and are diminished ments of
in expiration as the ribs approach and the sternum sinks. "'^ •

An alteration in depth is due to the condition of the diaphragm JR depth by

438

DISSECTION OF THE THOKAX.

but un-
equally.

Thorax

lesse:

how.

Intercostal
muscles.

Outer layer
is deficient
in front.

Dissection
of deeper
muscle.

Inner layer

deficient

behind.

Use of

outer
muscles;

in respiration ; for the muscle descends when air is taken into the
lungs, thus increasing the cavity ; and it ascends when the air is
expelled from those organs, so as to restore the previous size of the
space, or to diminish it in violent efforts. But the movement of the
diaphragm is not e']^ual throughout, and some parts of the cavity
will be increased more than others. For instance, the central ten-
dinous piece, which is joined to the heart-case, moves but slightly ;
but the lateral, bulging parts descend freely, and increase greatly
the capacity of each half of the chest below by their separation
from the thoracic parietes.

The thoracic cavity may be diminished by the diaphragm being
pushed upwards by enlargement, either temporary or permanent, of
the viscera in the abdomen ; or by the existence of fluid in the
latter cavity.

Dissection. The external intercostal muscle should now he
carefully cleaned, care being taken to preserve the nerves and a thin
aponeurosis (anterim' intercostal membrane) which passes forwards
from the muscle to the sternum at the front of the chest.

The INTERCOSTAL MUSCLES fomi two layers in each space, but
neither occupies the whole length of the interval. The direction
of the fibres is different in the two, those of the external muscle
running very obliquely downwards and forwards, while those of the
internal pass, although less obliquely, downwards and back%vards.

The external muscle consists of fleshy and tendinous fibres, and is
attached to the margins of the ribs bounding the intercostal space.
It extends from the tubercle of the upper rib behind to the end of
the bone in front, except in the last two spaces, where the muscle
is continued forwards between the cartilages. The thin anterior
intercostal membrane takes the place of the muscle between the
rib-cartilages.

Dissection. The internal intercostal muscle will be seen by
cutting through and removing the external intercostal and the mem-
brane in one of the widest spaces, say the third.

The internal intercostal muscle passes from the inner surface of the
rib above to the upper border of the one below internal to the
attachment of the external intercostal muscle. It begins near
the angles of the ribs behind, the upper muscles approaching more
closely to the spine than the lower ones, and reaches to the
extremity of the intercostal space at the sternum in front. The fibres
of the lowest two muscles are continuous anteriorly with those of
the internal oblique of the abdomen. One surface is in contact
with the external muscle, and the intercostal vessels and nerves ;
and the other is lined by the pleura.

The hinder part of the muscles will be seen again in the dissection
of the back and thorax.

Action. By the action of the intercostal muscles the ribs are
moved in respiration.

The external intercostals elevate the ribs and evert the lower edges,
so as to enlarge the thorax in the antero-posterior and transverse
directions : they come into play during inspiration.

INTERCOSTAL NERVES AND VESSELS. 439

The intern<il intercostals act in a diflFerent way at the side and fore of inner
part of the chest. ^'^^i^'

Between the osseous part of the ribs they depress and turn in interosseous
those bones, diminishing the size of the thorax ; and they are ^ '
brougbt into use in expiration.

Between the rib cartilages they raise the ribs, and are muscles intercarti-
of inspiration, like the outer layer. St°°"^

Dissection. The intercostal vessels and nerves at the sides and
front of the chest are now to be examined. The intercostal arteries
which run from behind forwards are small and are not easily
dissected out except in a well-injected subject. The best guide to Expose
the intercostal nerve is the lateral cutaneous branch, and this should n^rv'Js^ami
be gently pidled on and traced back to the parent trunk. The third vessels.
and fourth spaces may be devoted to the particular examination
of the nerves, and the fourth rib should be cut through at its junction
with its cartilage in front and as far back at the side as possible,
and the severed portion of rib shelled out from its internal peri- Remove a
ostium, great care being taken not to injure the subjacent pleura, ^rib!^
The nerve and its accompanying vessel should first be sought for
far back between the intercostal muscles close to the rib above.

The INTERCOSTAL NERVES uow seeu only in the anterior half of intercostal
their extent, are the anterior primary branches of the dorsal nerves, °®"'^^'
and supply the wall of the thorax. Placed at first between the course,
layers of the intercostal muscles below the corresponding artery,
each gives ott' the lateral cutaneous nerve of the thorax about mid'
way between the spine and the sternum. Then, much diminished termination,
in size, the nerve is continued onwards, at first in the substance of
the internal intercostal muscle, and afterwards between that muscle
and the pleura as far as the side of the sternum, where it ends as
the anterior cutaneous nerve of the thorax. Branches supply the branches,
intercostal muscles, and the triangularis stemi.

The INTERCOSTAL ARTERIES which ruu from behind forwards intercostal
between the ribs are derived from the thoracic aorta in the case of ^ifuJ^J^te :
the nine lower intercostal spaces (these being known as the aortic
intercostal arteries), and from the superior intercostal branch of the sub-
clavian in the case of the upper two spaces. They lie with the nerves
Ijetween the strata of intercostal muscles, and close to the upper
rib bounding the space. Near the angle of the rib the artery gives
off a collateral bi-anch which is continued forwards along the edge
of the rib below ; and both it and the parent vessel anastomose in
front with the anterior intercostal offsets of the internal mammary
artery which run outwards.

A small cutaneous offset is distributed with the lateral cutaneous offsets,
nerve of the thorax, and other branches are furnished to the
thoracic wall.

Dissection. Make three saw cuts through the sternum, two Division of
transversely across, one opposite the middle of the first intercostal ^^^ stemum.
space, and the other between the junction of the sixth costal
cartilages, and with a third cut divide the piece of sternum between
the first two cuts longitudinally into two, taking care not to open

440

DISSECTION OF THE THOKAX.

Dissection
of inl ernal
mammary
A'essels.

Triangularis
sterni :

origin ;

insertion

relations ;

Internal

mammary

artery

courses
through
thorax to
abdomen.

the pleural sacs. To bring into view the triangularis sterni muscle
and the internal mammary vessels, the left half of the sternum
with the cartilages of the true ribs, except the first and
seventh, are to be taken away with the intervening muscles ; but
the two ribs mentioned are to be left untouched for the benefit of
the dissectors of the abdomen and of the head and neck. Small
arteries to each intercostal space and the surface of the thorax, and
the intercostal nerves are to be preserved. If the piece of sternum
and the costal cartilages are divided and removed carefully these
can be shelled oflf the subjacent structures without injury to them.
The surface of the triangularis sterni will be apparent when the loose
tissue and fat are removed.

The TRIANGULARIS STERNI (fig. 160) Is a thin muscle beneath the
costal cartilages. It arises internally from the side of the ensiform
process, from the back of the sternum as high as the third costal

cartilage, and, usually,
from the inner ends
of the cartilages of the
lower two or three
true ribs. Its fibres
are directed outwards,
the upper ones also
ascending consider-
ably, and are inserted
by fleshy slips into
the true ribs except
the first and last, at
the junction of the
bone and cartilage :
some of the fibres
frequently end in an
aponeurosis in the in-
tercostal spaces.

In front of the
muscle are the rib-
cartilages and the internal intercostals, with the internal mammary
vessels and intercostal nerves. Behind, it lies on the pleura. Its
lower part is continuous with the transversalis muscle of the
abdomen (fig. 160, b). The size of this muscle varies greatly, and
one or more of the upper slips are frequently wanting.

Action. The triangularis sterni assists in depressing the anterior
ends of the ribs, and acts with the interosseous part of the internal
intercostals in expiration.

The INTERNAL MAMMARY ARTERY is a branch of the subclavian,
and enters the thorax- beneath the cartilage of the first rib. It is
continued through the thorax, lying behind the costal cartilages and
about half an inch from the sternum, as far as the sixth intercostal
space ; here it gives externally a large muscular branch {musculo-
phrenic), and then passing beneath the seventh cartilage, enters
the sheath of the rectus muscle in the wall of the abdomen. In

Fig. 160. — View from Behind of, a,
Triangularis Sterni Muscle.

THE PLEUKAL CAVITY. 441

the chest the artery lies on the pleura and the triangularis sterni,

and is crossed by the intercostal nerves. It is accompanied by

two veins, and by the chain of sternal lymphatic glands. Its Branches:

thoracic branches are numerous but small : —

a. A long, slender branch (comes nervi phrenici) arises as the superior
artery enters the chest, and descends to the diaphragm with the ^ ^ ' •
phrenic nerve : this branch is seen in the dissection of the thorax.

h. Small sternal branches supply the triangularis sterni, and small pos-
ramify over the back of the sternum. From these, mediastinal ^^^^^ °
twigs pass backwards to be distributed to the remains of the
thymus gland and the pericardium.

c. Two anterior intercostal branches run outwards in each space, intercostal,
lying along the borders of the costal cartilages, and terminate by
anastomosing with the aortic and superior intercostal branches.

d. Perforating branches, one or two opposite each space, pierce perforating,
the internal intercostal and large pectoral muscles, and are dis-
tributed on the surface of the thorax with the anterior cutaneous

nerves : the lower branches supply the mamma in the female.

e. The muscido-phrenic branch courses outwards beneath the muscuio-
cartilages of the seventh and eighth ribs, and enters the diaphragm : P^*°^^-
it supplies anterior branches to the lower intercostal spaces. Its
termination has been seen in the dissection of the abdomen.

Two veins accompany the artery ; these join into one trunk, Veins,
which opens into the innominate vein.

Section IT.

THE CAVITY OF THE THORAX.

The cavity of the thorax is the space included by the spinal Definition,
column, the sternum, and ribs, and by certain muscles in the
intervals of the bony framework. In it the organs of respiration, Contents of
and the heart with its great vessels are lodged ; and through it the ^^'*^y-
gullet, and some vessels and nerves are transmitted.

Dissection. The soft parts should now be cleared away from Dissection
between the ribs and cartilages on both sides, and the parietal {Jq^x"
layer of the pleura will then be seen adherent to their inner
surfaces. Care should be taken, however, below the ninth rib not
to remove portions of the diaphragm, as it lies here close to the
chest wall, and the cavity of the thorax is there very narrow. The Remove
second, third, fourth, fifth and sixth ribs on the left side should J'j^g"" ^^"
then be divided as far back as possible, and taken away without
opening the pleura beneath.

A longitudinal incision will then be made down the whole
length of the exposed pleura, about midw^ay between the vertebrae Open
and the sternum, and small cross cuts will be made above and ^ ^"'^*

442

DISSECTION OF THE THORAX.

Open right
side.

Sac of the
pleura :

fonn:

outer
surface ;
inner
surface ;

disposition.

Difference in
sac of right,

and of left
side.

The con-
tinuity is
here traced

from wall of
chest to
lung

below, so as to freely admit the hand into the pleural cavity.
When the general cavity has been examined, the anterior
mediastinum, or the space between the two pleural sacs behind
the sternum and in front of the pericardium, will be cleared. "With
one hand in the pleural sac as a guide to its anterior limit, it will
be found easy to mark the limits of the mediastinum, and the
pleurae can be readily separated in the middle line, and from the
pericardium, which they overlap. The portion of sternum with
the ribs and cartilages of the right side have been left on for the
preservation of the anterior mediastinum, but after it has been
examined the ribs should be removed on the right side as on the
left, and the pleural sac opened and its limits defined. Finally
the right half of the sternum with the attached costal cartilages
will be removed and kept aside with the left portion for future
examination. It, unfortunately, often happens in subjects for
dissection, that the pleura is thickened and adherent to the lung.
Should the dissector find it is so on the left side, he should
at once open the right in case the membrane may be healthy on
that side.

The pleura are two serous membranes, or closed sacs, which are
reflected around the lungs in the cavity of the thorax. One occu-
pies the right, and the other the left half of the cavity ; they
approach each other along the middle of the chest, forming a
thoracic partition or mediastinum.

Each pleura is conical in shape ; its apex projects into the neck
above the first rib (fig. 162, p. 447) ; and its base is in contact with
the diaphragm. The outer surface is rough, and is connected to the
lung and the wall of the thorax by areolar tissue ; luit the inner
surface is smooth and free. Surrounding the lung, and lining the
interior of one half of the chest, the serous membrane consists of a
parietal part, which is variously called —

1. Costal pleura, where it lines the chest- wall ;

2. Phrenic pleura, where it covers the diaphragm ;

3. Pericardial pleura, where it covers the pericardium ; and

4. Cervical pleura, where it passes into the neck.
The visceral pleura is the pulmonary pleura.

There are some diff'erences in the shape and extent of the two
pleural bags. On the right side the bag is wider and shorter than
on the left ; and on the latter it is narrowed Ijy the projection of
the heart to that side.

The continuity of the bag of the pleura may be traced horizontally
from any given point, over the lung and chest wall, back to the same
spot in the following manner : — Supposing the membrane to be
followed outwards from the sternum, it lines the wall of the chest
as far as the spinal column ; here it is directed forwards to the root
of the lung, and is then reflected over the viscus, as the visceral or
pulmonary pleura, covering its surface, and extending into the
fissures between the lol)es. From the front of the root of the lung
the pleura may be followed over the side of the pericardium back
again to the sternum.

PLEURAL REFLECTION. 443

Below the root of the lung it forms a thin fold, the ligamentum
latum pulmonis^ which unites the inner surface of the lung to
the side of the pericardium, and may be seen by enlarging
tbe hole in the pleura and drawing the lower part of the lung
out. The ligament then appears as a fold passing from the broad liga-
inner part of the lung to the pericardium and presenting a free fj^"^ °^ ^^®
lower border. At the upper part of the chest the pleura forms a
dome over the apex of the lung, which may be revealed by drawing
that part of the lung downwards. At this part the membrane is
strengthened by the strong fascia of the neck {Sibson's fascia), which Sibson's
is attached to the inner border of the first rib and closely invests *^^"*'
the vessels at the upper opening of the thorax.

Line of pleural reflection. Surface marking. The pleural Surface
ca^ity extends upwards on each side in the neck, two inches above ™^^ '°^'
the anterior part of the first rib, or an inch above the middle of the
clavicle, where the shoulder is depressed. From this point the
anterior limit of the sac extends downwards and outwards, reaching
the middle line at the lower part of the manubrium sterni, and
continues down in that line, or a little to the left thereof.

On the left side, opposite the fourth costal cartilage, it passes left side,
outwards until clear of the sternum, and then passes downwards
along its left side to the back of the sixth costal cartilage, thus
presenting a notch, in which the pericardium comes into contact
Avith the lower part of the sternum ; but the notch is much less praecordial
than that formed by the corresponding part of the lung (fig. 162). '

The pleura is connected by fascial bands to the upper surface of
the diaphragm, and the line of its reflection passes in succession
behind the sixth and seventh costal cartilages, reaching the junction
of the eighth rili, with its cartilage in the lateral line. From this
point it extends round the body, crossing the lower border of the
tenth rib in a line midway behind the vertebrae behind and the
middle line in front. This is usually the lowest part of the pleural
cavity, and from here it extends backwards to the inner surface of
the twelfth rib, and, quite commonly, it projects below the twelfth projection
rib under the external arched ligament of the diaphragm. It is twelfth rib
most important to bear this fact in mind in operations on the
posterior abdominal wall, so as to avoid opening the pleural sac.

On the right side the line of the pleural reflection is the same as on right*
on the left, except that it does not present ^ notch behind the '
sternum, where it overlaps the pericardium, Init continues directly
downwards on the middle line until it reaches the seventh costal
cartilage, behind which its line of reflection passes outwards and
downwards as on the left side.

The mediastinum. The median thoracic partition, or medias- Along
tinum, is formed by the inner portion of the parietal pleura on sacs form a
each side, and the structures interposed between the two mem- septum,
branes. It extends the whole depth of the thomx, and reaches
mesially from the spine to the sternum, thus separating the right
and left pleural cavities. In the centre the two layers of serous
membrane are widely sciparated by the heart ; but in front and

444 DISSECTION OF THE THORAX.

behind they come nearer together. The partition is artificially
divided into four parts, which are distinguished as the superior,
anterior, middle, and posterior mediastina.

CO oe

<D ?<

(3
1

cation betw
•jugular veil

ve.

ugular vein.

1
i

C
Is

S-i

(3
0

-2

c
\

J2
\

1
c

1 =

/ /

'S
2

. \

/ /

/ ,

e£

\ ^

V ^

V >

^ \ •

* y / / /

^ /

/ J

rAi^

LJUil/

1 /

' /

w)^

i\,

tV^Hm/ /

'^ /

Mr%

l^^

^ilSlK/

Groove formed by
subclavian artery.

Superior inter-
costal vein.
V Left innominate

vein.
Groove formed
by left innomi-
nate vein.

Superior
medias-
tinum :
boundaries,

Right coronary artery.

Fig. 161. — The Contents of the Thorax seen from the Fhont. The
Lungs were Filled with Melted Wax and were held Apart in
Front until the Wax had set. (From a Specimen in Charing
Cross Hospital Museum.)

The superior mediastinum is the part of the thoracic chamber
above the pericardium, and may be defined as bounded below

THE MEDIASTINA. 445

by a plane extending from the lower border of tbe body of the

fourth dorsal vertebra to the junction of the manubrium with the

body of the sternum. It is limited in front by the manubrium

with the origins of the sterno-hyoid and sterno-thyroid muscles,

and behind by the upper four dorsal vertebrae and the lower ends

of the longi colli muscles. Between the pleurae in this part there

are found, proceeding from before backwards, the following objects : and

— the remains of the thymus gland, several lymphatic glands, the

innominate veins (fig. 162), and the upper half of the superior

cava, the phrenic and pneumo-gastric nerves, the arch of the aorta

with its three large branches, innominate, left carotid and left

subclavian, the trachea, oesophagus and thoracic duct, and the left

recurrent laryngeal nerve.

The anterior mediastinum is the space in front of the pericardium -^terior
1 11 -I • • • -1 1 c • 1 mediasti-

between the pleurae, and is very narrow m its upper half, since the num is the

two pleurae meet behind the sternum from the level of the second ^™*^^^^ •

to the fourth costal cartilages. Below the latter spot the left pleura

inclines away from the middle line, and is separated from its fellow

by an interval in which the pericardium comes into contact

with the sternum and the left triangularis sterni muscle. This coi^tents.

mediastinum contains only some areolar tissue, with a few small

lymphatic glands. In some bodies the left pleura is continued

behind the sternum nearly as far as the diaphragm.

The middle mediastinum is the largest part of the central space, and Middle me-
includes the pericardium with the contained heart and great vessels, contents.
A*iz., the ascending aorta, the trunk of the pulmonary artery, and
the lower half of the superior vena cava ; also the phrenic nerves,
the roots of the lungs with the bronchial lymphatic glands, and, on
the right side, the arch of the azygos vein.

The posterior mediastinum is the portion between the pericardium Posterior
and the spine ; and the interpleural space is here larger than in tinum^:
front of the heart. Its extent and contents will be shown later,
but it may be here said that enclosed between the serous layers boundaries,
of the posterior mediastinum (fig. 174, p. 481) are the descending and con-
thoracic aorta, the azygos veins, the oesophagus with the pneumo- ^*"^
gastric nerves, and the thoracic duct, as well as a set of lymphatic
glands.

Dissection. The pleurae and the fat are now to be cleaned from Clean peri-
the sides of the pericardium. ^"^"^ ^""^

The root of the lung is to l>e dissected oat by taking away the the root of
pleura and the areolar tissue from the front and back without ® ""^*
injuring its component vessels. To clean the back of the root, the
lung should be thrown forwards to the opposite side of the chest.
In this dissection the phrenic nerve and artery will be found in Trace the
front of the root, together with a few small anterior pulmonary °^^^^*-
nerves ; the last are best seen on the left side. Behind the root of
the lung is the vagus nerve, dividing into branches ; and arching
above the right one is the large azygos vein. and azj-gos

For the present, the arch of the aorta and the small nerves on it ^^"^
may be left untouched.

446

DISSECTION OF THE TFTORAX.

Thymus
body in
foetus :

The THYMUS GLAND is ail organ which is most developed in the
infant, and the use of which is not understood. It is placed mainly
in the upper part of the thorax ; and it may be best examined in a
full-grown foetus.

size At birth it is about two inches in length, and of a greyish

colour. It consists of two lobes of a conical form, which touch each

and extent, other. Its ujDper end is pointed, and extends on the trachea as high
as the thyroid body ; and the lower, wider, part reaches as far as
the fourth rib. In the thorax it rests on the aortic arch and its
large branches, on the left innominate vein and on the pericardium.
In the young adult all that remains of the thymus is a brownish
rather firm material in the interpleural space behind the upper end
of the sternum ; and after middle life it has generally disappeared
altogether.

Remains in
adult.

RELATIONS OF THE LUNGS.

Number
and use.

Form

and parts.

Base

touches

diaphragm

shape and
level.

Apex is in
the neck.

Anterior
edge is thin

position on
right,
and left
side.

The lungs are two in number, and are contained in the cavity of
the thorax, one on each side of the spinal column. In these organs
the blood is changed in respiration.

Each lung is of a somewhat conical form, and takes its shape from
the space in which it is lodged. It is unattached, except at the
inner side where the vessels enter forming the root ; and it is
covered by the bag of the pleura. It has a base and apex, two .
borders and two surfaces. Two fissures on the right and one on
the left divide it into lobes.

The base of the lung is hollowed in the centre and thin at the
circumference, fitting the convexity of the diaphragm. Following
the shape of that muscle, it is sloped obliquely from before back-
wards, and reaches in consequence much lower behind than in front.

Surface marking (fig. 162). The position of the lower border with
respect to the wall of the thorax may be roughly indicated by a line
drawn from the sixth chondro-sternal articulation with a slight
convexity downwards to the tenth dorsal spine ; but it will be
slightly lower in front on the left, than on the right side. The a^ex
is rounded, and projects from one to two inches above the anterior
end of the first rib, where it lies beneath the clavicle, the anterior
scalenus muscle, and the subclavian artery.

The anterior border is thin, and overlies in part the pericardium.
On the right side it lies along the middle of the sternum as low as
the sixth costal cartilage. On the left side, however, it reaches, like
the pleura, along the middle line only as low as the fourth costal
cartilage. Below that spot it presents a V-shaped notch the apex
of which is opposite the outer part of the cartilage of the fifth rib.
Below the notch the lung extends inwards behind the outer part of
the sixth costal cartilage, and the lower border passes round the
chest, on the left as well as on the right sides, crossing the seventh
rib in the lateral line and the ninth rib when it is half way round
the body, and it is roughly at that part a rib and an intercostal space
above the line of pleural reflection.

RELATIONS OF LUNGS.

447

The posterior border is half as long again as the anterior, and
projects inferiorly between the lower ribs and the diaphragm ; it is
thick and vertical, and is received into the hollow by the side of
the spinal column.

The outer surface of the lung is convex, and is in contact with
the wall of the thorax : a large cleft, known as the great fissure,
divides it into two parts, and on the right side there is an additional
smaller fissure. The inner surface is flat when compared with the
outer : at the fore part is a large hollow which lodges the heart and
great vessels, and is most marked on the left lung ; and behind
this is a depression about three inches long, hilum pulmonis, which

Posterior
edge is
thick.

External
surface.

Internal
surface

gives attach-
ment to the
root.

Fig. 162. — Diagram to show the Difference in the Anterior Border
OF THE Right and Left Lung, the Edge being indicated by the
Dark Line; and to mark the different Level of the Base on
the two sides.

receives the vessels of the root of the lung. In the hardened
specimen well-marked grooves are seen upon the lung for the
reception of the great vessels with which it is in contact, and on
the left lung is a specially deep groove in its inner surface formed
by the arch of the aorta, and by the descending thoracic aorta
(fig. 163, p. 448).

Each lung (fig. 161) is divided into two lobes by the great fissure, Division
w^hich, running obliquely downwards and forwards, begins at the ^^
posterior border near the apex, and ends at the fore part of the base, ^^^^ *^
and the lower lobe of the lung is larger than the upper. In the and the
right lung a second horizontal fissure is directed forwards from the "joht
middle of the oblique one to the anterior border, and cuts oS a small

448

DISSECTION OF THE THORAX.

Surface
marking of
the fissures.

triangular piece from the upper lobe, which is called the middle
lobe. Occasionally there may be a trace of the third lobe in the
left lung.

The surface marking for the great fissure of the lung is a line
taken downwards and forwards round the chest from the middle
line of the back behind opposite the root of the spine of the scapula,
to the junction of the sixth rib with its cartilage in front and
below. The horizontal fissure of the right lung is marked by a line

Fig. 163. — The Roots op the Lungs from the Front. The Lungs were

SEPARATED FROM ONE ANOTHER, THE GREATER PART OF THE ArCH OP

THE Aorta cut away, and the Heart drawn down.

Difference
in form and
size of the
lungs.

Root of the
lung :

situation ;

drawn outwards from the middle of the sternum opposite the fourth
costal cartilage until it meets the line of the great fissure.

Besides the difference in the number of the lobes, the right lung
is larger and heavier, and is wider and more hollowed out at the
base, as well as being somewhat shorter than the left. The increased
length and the narrowness of the left lung are due to the absence of
a large projecting body like the liver below it, and to the direction
of the heart to the left side.

The ROOT OF THE LUNG (fig. 163) cousists of the vessels entering the
fissure on the inner surface ; and as these are bound together by
the pleura and some areolar tissue they form a stalk, which
attaches the lung to the heart and windpipe. The root is situate

THE ROOT OF THE LUNG. 449

at the inner surface, a1x)ut midway between the Ijase and apex,
and about a third of the way from the posterior to the anterior
border of the lung.

In front of the root on both sides are the phrenic and the relations,
anterior pulmonary plexus of nerves, the phrenic nerve being some
little distance from it upon the side of the pericardium. Anterior
to the i-oot of the right lung also is the superior vena cava.
Behind on both sides is the posterior pulmonary plexus ; and on
the left side there is, in addition, the descending aorta. Ahove^
on the right side, is the great azygos vein ; and on the left side, the
arch of the aorta. Beloiv each root is the fold of pleura called the
ligamentum latum pulmonis.

In the root of the lung arejcollected a branch of the pulmonary consti-
artery, two pulmonary veins, and a division of the air tube the'root^-
(bronchus), as well as small nutritive bronchial arteries and veins,
and some nerves and lymphatics. The lai*ge vessels and the air
tul>e have the follo^Wng positions to one another : —

On both sides the bronchus is on a posterior plane, and the their rela-
pulmonary veins are lowest down on the most anterior plane, and tlons^*^'
the pulmonary artery is intermediate. On the right side the
uppermost branch of the bronchus occupies the highest place"
and the remainder of the bronchus is directed do%vnwards and
outwards behind the blood vessels, the pulmonary artery is next
highest and the veins are lowest down. On the left side the differences
pulmonary artery occupies the highest place with the veins below g^^j^f ^^°
it, within its conca\dty, and being anterior to the artery at their
emergence from the lung ; the bronchus is directed downwards and
outwards behind the vessels, and is intermediate in level. This
difference in the two sides is accounted for by the fact that the
bronchus of the right side gives off its branch to the upper lobe of
the lung before it is crossed by the artery ; while on the left side
there is no corresponding branch of the airtube, and the artery
crosses the undivided bronchial stem.

THE PERICARDIUM.

The bag containing the heart is named the pericardium. It is Pencar.
situate in the middle of the thorax, in the interval l:)etweeu the ^"™*
two pleuree.

Dissection. The surface of the pericardium should now be Clean ves-
cleaned, and the student should dissect out the large vessels above ^^^^ ofheart
the heart, and trace the nerves (fig. 161, p. 444).

In cleaning the fibrous pericardium it will be noticed that Ijands
connect it with the back of the upper and lower portions of the
sternum still remaining — the superior and inferior stemo-pericardial
ligaments.

The large artery curving to the left above the pericardiimi is the First aorta,
aorta, which furnishes three trunks to the head and the upper
limbs, viz., from right to left, the innominate, the left common

D.A. G o

450

DISSECTION OF THE THORAX.

minate veins

and
tributaries,

and upper
cava.

carotid, and left subclavian. On its left side of the aorta, and
within the concavity of its arch, is the pulmonary artery.
theninno- Above the arch of the aorta a large venous trunk, left
innominate, crosses over the three arteries mentioned above, and
ends by uniting on the right side with the right innominate vein
in the upper cava. Several small veins, which may be mistaken
for nerves, ascend over the aorta, and enter the left innominate.
Define the tributaries of this vein, and especially one crossing
the aortic arch towards the left side, which is the left superior
intercostal vein. The inferior thyroid vein, which descends in
front of the trachea to open into the left innominate vein or into
the junction of the two innominate veins, should also be dissected
out.

The large vein by the side of the aorta is the superior vena cava ;
and the azygos major vein will be found opening into it behind, above
the aorta of the right lung.

The phrenic nerves should be cleared on l)oth sides from their
entry into the thorax behind the subclavian veins above, along the
side of the pericardium to the diaphragm below, as well as the left
vagus nerve, which lies deeply upon the aortic arch, and will be
found coming downwards in front of that vessel from between the
origin of the left common carotid and subclavian arteries. Between
the left phrenic and vagus nerves and close to the aorta are the left
superficial cardie nerve of the sympathetic, and the lower cervical
cardiac branch of the left vagus ; of the two, the last is the smaller,
and in front of the other.

The cardiac nerves from the left vagus and sympathetic are to ho.
followed to a small plexus (superficial cardiac) in the concavity of
the aorta. An offset of the plexus is to be traced downwards
between the pulmcnary artery and the aorta towards the right
coronary artery of the heart ; and another prolongation is to be
found coming forwards from the deep cardiac to the superficial
plexus ; this dissection is difficult, and requires care.

When the pericardium is afterwards opened the nerves will be
followed on the heart.

The PERICARDIUM is somewhat conical in form, the w^ider part
being turned towards the diaphragm, and the narrower part

Nerves.

Dissect
superficial
plexus in
arch of
aorta.

Pericar-
dium :
size and
form ;

position

extending upwards beyond the heart on the large vessels. It is
placed behind the sternum, and projects on each side of that bone,
but much more towards the left than the right side. Laterally the
pericardium is covered by the i)leura, and the phrenic nerve and
vessels lie between the two. Its anterior surface is separated from
the chest-wall by the pleurae and lungs, except over the small area
on the left side corresponding to the lower part of the anterior
mediastinum ; and behind, in the interval between the pleurae, it
is in contact with the oesophagus and aorta.

The heart-case consists of a fibrous structure, which is lined
internally by a serous membrane.
Fibrous part The flbrous part surrounds the heart, and is pierced by the large
sheaths to vessels joining that organ ; and, with the exception of the inferior

relations.

Composi-
tion.

THE PERICARDIUM. 451

cava, it gives prolongations along the vessels, the strongest of which
is on the aorta.

Below the pericardium is united to the central tendon of the Attach-
diaphragm, and extends a little over the muscular tiss^ue, especially diaphragm ;
on the left side. For the most part it can be readily separated
from the diaphragm, but in the median part of the central tendon
it is tirndy adherent, and the intimate association of the diaphi-agm,
the back part of the pericardium and the roots of the lungs through
the ligamentum latum pulmonis should be noticed.* The inferior
^•ena cava pierces the pericardial attachment below, and, imme-
diately entering the lower part of the right auricle, does not
receive a sheath from the pericardium. In front, the pericardium
is loosely connected to the back of the sternum in the superior to sternum ;
mediastinum through the sterno- pericardial ligaments already
noticed. The extent of its investments of the vessels entering or
leaving the heart will be better seen when it is opened. It can
now be seen that it is thickest at the upper part, and is formed
of fibres crossing in different directions, many being longitudinal, to fascia of
and it can be traced up on to the large vessels at the opening of ^ °^^ *
the thorax, and by pulling upon it, it will be seen that it is
connected with the fascia at the root of the neck.

Dissection. The pericardium should now be opened by a
longitudinal incision running its whole length from the front of the
aorta, and by a cross cut passing from the front of the root of one
lung to that of the other.

The serous sac consists of parietal and visceral parts, which are Serous
continuous with one another along the great vessels. The parietal ffbrous','^^^
part lines the fibrous membrane, with which it is insepambly
united, and the included portion of the diaphragm ; while the
visceral part covers the heart. It is reflected around the and covers
pulmonary artery and aorta, enclosing them in one sheath, but '

not passing between them. The passage, through which the finger disposition
shoidd be passed from side to side behind the aorta and pulmonary vessels ;
artery within the sac, is called the transverse sinus of the pericardium, transverse
The superior vena cava and the four pulmonary veins are only covered *^""^ '
by the serous membrane on the front and sides, and are in contact with
the fibrous layer behind. If the apex of the heart be lifted upwards to
the right, at the back of the left auricle the serous membrane will be
seen to form a blind pouch between the pulmonary veins of the two
sides. This pouch is known as the oblique sinus of the pericardium, oblique

In front of the root of the lelt lung the serous layer forms a *'°"^ '
small triangular fold, the vestigial fold of the pericardium (Marshall), vestigial
between the pulmonary artery and the upper pulmonary vein. ^°^*^*
This includes the remains of a left superior cava which existed in
the fcetus, and, like the oblique sinus, can be seen by lifting the
heart over to the right side.

The vessels of the pericardium are derived from the aorta, the internal Vessels.
mammary, the bronchial, the oesophageal and the phrenic arteries.

* See a paper by Keith on " The Nature of the Mammalian Diaphiagm and
Pleural Cavities." — Journal of Anat. and Phys., vol. xxxix., 1905.

G G 2

452

DISSECTION OF THE THORAX.

Nerves. Nerves. According to Luschka the pericardium receives nerves

from the phrenic, sympathetic, and right vagus.

Tlie heart
is hollow.

Form:
anterior
surface ;

THE HEART AND ITS LARGE VESSELS.

The heart is a hollow muscular organ by which the blood is
propelled through the body. Into it, as the centre of the vascular
system, veins enter ; and from it the arteries issue.

Form (figs. 164 and 165). The heart is conical in form, but
somewhat compressed from before backwards. The anterior surface,
formed by the right ventricle and portions of the right auricle and

inferior
surface

posterior
surface ;

right
border.

Size and
weight.

Fig. 164. — The Heart sken from the Front and the Left Side. The
Ductus Arteriosus is cut Across and the Aorta Lifted up to
SHOW the Right Branch of the Pulmonary Artery.

(From a specimen in Charing Cross Hospital Museum).

the left ventricle, is convex ; the inferior surface, where it rests on
the diaphrag m, is formed by a great part of the left and a portion
of the right ventricle, and is nearly flat ; the posterior surface,
formed by the left auricle and portions of the left ventricle and
right auricle, is nearly flat and somewhat quadrilateral in outline,
left border; The left border, formed by the left ventricle, is thick and rounded ;
while the right, formed by the right auricle and a jjortion of the
ventricle, is thin and less firm.

Size. The size of the heart varies greatly ; and it is usually
smaller in the woman than in the man. Its average measurements
may be said to be about five inches in length, three inches and

POSITION OF HEART.

4o3

a half in width, and two and a half in thickness. Its weight is
generally from ten to twelve ounces in the male, and from eight to
ten in the female.

Position and direction. The heart lies behind the body of the Situation in
sternum, and projects on each side of that lx)ne, but more to the *^^ '^^^^
left than the right. Its axis is directed very obliquely, from
behind forwards and to the left, as well as somewhat downwards.
The base, or posterior surface, is towards the spine, being opposite Base ;
the sixth, seventh and eighth dorsal vertebrae, and looks backwards
and upwards. The apex strikes the wall of the chest during life in apex ;
the fifth intercostal space of the left side, opposite the junction of the
ribs with their cartilages. The anterior surface looks forwards and surfaces ;

Ductus arteriosus.

Branches of the pulmonary
artery.

Pulmonary veiu.
Pulmonar}- vein. _

Coronary sinus.

Left subclavian.
Left common carotid.
Innominate artery.

Aorta.

Superior vena cava.
Pulmonary vein.

Pulmonary vein.

Inferior vena caval
entrance to right
auricle.

Right auriculo-
ventricular groove.

Posterior inter-ventricular groove.

Fig. 165. — The Heart seen prom Behind and Below.
(From a specimen in Charing Cross Hospital Museum).

somewhat upwards ; while the inferior surface is nearly horizontal,
resting on the diaphragm. The right margin is turned to the borders;
front ; and the left is placed farther back.

In consequence of the oblique position of the heart, the right ri^ht and
half and the apex are directed towards the thoracic wall, though
mostly with lung intervening ; while the left half is undermost
and deep in the cavity.

Surface marking (fig. 166). The extent of the heart in relation Extent of
to the front of the chest may be indicated as follows : — The upper upwards,
limit is marked by a line across the sternum from the lower edge
of the second costal cartilage of the left side to the upper edge of
the third cartilage of the right side ; and the lower limit by a line,

454

DISSECTION OF THE THOIiAX.

downwards, slightly eonvex downwards, from the seventh chondro-sternal
articulation of the right side to the apex in the tifth left interspace
just below the costo- chondral junction, the latter point being usually
about one inch and a half below, and three-quarters of an inch to
the sternal side of the nipj^le in the male and, before child-bearing,
in the female. On the right side the heart projects about one inch
and a half from the middle line of the sternum ; and on the left,
the apex is distant from three to three and a half inches from the
centre of the breast-bone.

The portion of the heart which is uncovered l)y lung {the area of

to right

and left.

Superficial
portion of
heart.

Fig. 166. — Diagram showing the Position of the Heart to the Ribs
AND Sternum, the Soft Parts being removed from the Exterior
of the Thorax. The Edge of each Lung is shown by a Dotted
Line. The Left Auricle extends somewhat higher than tkb
Area indicated in thr Figure, Projecting into the Second
Intercostal Space.

suiierficial cardiac duhiess) is included between the middle line of
the sternum, in its lower third, and a line drawn from the centre
of the breast-bone between the fourth costal cartilages to the apex
of the heart (fig. 166).
Chambers of Coni'ponent parts. The heart is a double organ ; and in each half
^^ ■ there are two chambers, an auricle and a ventricle, which com-

municate together, and are provided with vessels for the entrance
Grooves: and exit of the blood. The surface is marked by grooves indicating
auricuio- this division. Thus, passing circularly round the heart, nearer the
' base than the apex, is a groove which cuts off the thin auricular

POSITION OF THE HEART. 455

from the fleshy ventricular part ; and on each surface there is a and inter-
longitudinal sulcus, usually occupied by whitish fat along the line ^*^" "cu ar.
of the coronary blood vessels, over the partition between the
ventricles. The interventricular groove is nearer the left border of
the heart in front, and nearer the right border behind.

The auricles are two, right and left, and their wall is much Auricles :
thinner than that of the ventricles. They are placed deeply at the position,
base of the heart ; and each is prolonged forwards into a small
tapering part knowTi as the auricular appendix or auricle propeTy and append-
so called from its resemblance to a dog's ear. *^^^'

The ventricles reach unequal distances on the two aspects of the Ventricles:
heart : — thus the right one forms the lower part of the thin right right,
border, most of the anterior and a part of the inferior surfaces ; but and left
the left enters alone into the apex, and constructs the left border,
and the greater part of the inferior surface of the heart.

Dissection. Before opening the heart, the coronary arteries Dissect
(right and left) are to be dissected on the surface, with the veins ^.g^g^/^^^^
and small nerves that accompany them. The two arteries will be nerves,
found surrounded by fat on the sides of the pulmonary arteTy, and
run in the grooves on the surface of the heart, the right one being
directed between the pulmonary artery and the right auricular
appendix into the right auriculo-ventricular groove, and the left
one between the pulmonary artery and the left auricular appendix
into the left auriculo-ventricular groove. With each artery is a
plexus of nerves, and that of the right side is to be followed upwards
to the superficial cardiac plexus.

In the groove between the left auricle and ventricle the student and coro-
will find the large coronary vein, which passes to the back of the ^^^^ ''in«s.
heart to empty into the dilated coronary sinus ; and the last should
be defined and followed to its ending in the right auricle (fig. 167).

The COROXARY ARTERIES are the first branches of the aorta, and Two arteries
supply the heart, one being distributed mainly on the right side, ^.[^^^^ ^^^^'
and the other on the left.

The right artery appears on the right side of the pulmonary right coi-o-
trunk, and is directed backwards in the groove between the right "^'^^'
auricle and ventricle, giving branches upwards and downwards to
the walls of those chambers. Two of these are larger than the
rest ; one (right marginal) runs on the anterior surface of the right
ventricle near the free margin ; and the other (posterior inter-
ventricular) descends in the posterior interventricular furrow to the
apex of the heart. A small branch is continued to the left side of
the heart, lying in the hinder part of the left auriculo-ventricular
groove.

The /(?/)f a7-ferj/ passes outwards behind the pulmonary trunk to and left
the left side of that vessel, where it divides into two branches. Of ^^
these, the anterior is the larger (the anterior interventricular), and
descends on the front of the heart in the groove between the two
ventricles to the apex ; while the posterior turns backwards between
the Jeft auricle and ventricle, giving left marginal and posterior
ventricular branches. The branches of the two coronary arteries anasto-

456

DISSECTION OF THE THORAX.

Cardiac
veins.

Coronary
sinus :

extent :

Veins join-
ing it ;

Valves.

Large coro-
nary vein.

Small coro-
nary vein.

Posterior

cardiac

veins.

cardiac

veins.

communicate on tlie surface of the heart, but their anastomoses

are very fine.

The VEINS OF THE HEART (fig. 167) differ in their arrangement

from the arteries, and are for the most part collected into one large

trunk — the coronary sinus.

The coronary sinus (') will be seen on raising the heart to be

placed in the sulcus between the left auricle and ventricle. About

an inch in length, it is joined at the left end by the great cardiac

vein (*) ; and at the right
end it opens into the right
auricle. It is crossed by
the muscular fibres of the
left auricle. Inferiorly and
at its right end it receives
posterior cardiac branches
from the back of the ven-
tricles (1), and at its left
extremity another small
vein (2), the oblique vein
(Marshall), which descends
to it along the back of the
left auricle.

On slitting up the sinus
with the scissors the
openings of its different
veins will be seen to be
guarded by valves, with
the exception of the oblique
vein ; and at its right end
is the Thebesian valve of
the right auricle which will
be seen later when the
auricle is opened.

The left coronary or great
cardiac vein {*) begins in
front near the apex of the
heart, ascends in the inter-
ventricular groove, and
then turns to the back in
the sulcus between the left

auricle and ventricle, to open into the coronary sinus Q). It receives

branches, mainly from the left side of the heart, in its course ; and

its ending in the sinus is marked by a double valve.

The right coronary vein (^) is of small size, and runs in the hinder

part of the right auriculo-ventricular groove to the right end of the

coronary sinus.

The 'posterior cardiac veins (H) ascend on the back of the left

ventricle to the coronary sinus '; and one larger vessel, the middle

cardiac vein^ lies in the posterior interventricular furrow.

The anterior cardiac veins are three or four in nimiber, and run

Fig, 167. — Back of the Heart with its
Veins and the Coronary Sinus.
(Marshall).

A, Right auricle.

B. Left auricle, with the appendix, a.

1. Coronary sinus.

2. Oblique vein.

3. Right coronary vein.

4. Left or great coronary vein.

ft Posterior cardiac veins ; the larger
one on the right is the middle cardiac vein.

THE HEART. 4o7

upwards on the front of the right ventricle to open separately into
the lower part of the right auricle.

Smallest cardiac veins. Other small veins lie in the substance of Smallest
the heart, and are noticed in the description of the right auricle.

Cardiac nerves. The nerves for the supply of the heart are Nerves of
derived from a large plexus (cardiac) beneath the arch of the aorta,
from which offsets proceed to accompany the coronary arteries.
The greater part of this plexus is deeply placed, and will be
dissected at a later stage, but a superficial prolongation may now
be seen.

The superficial cardiac plexus is placed below the arch of the aorta, Superecial
to the right of the ductus arteriosus (fig. 164). The nerves joining ^ ^^"^
it are the left superficial cardiac of the sympathetic, the lower
cervical cardiac of the left vagus, and a considerable bundle from
the deep cardiac plexus. A small ganglion is sometimes seen in
the plexus. Inferiorly it sends off nerves along the right coronary ends in
artery to the heart. A few filaments also run on the left division nary.^°
of the pulmonary artery to the left lung.

The 7'ight coronary nerves pass from the superficial plexus to the Coronary
right coronary artery, and receive near the heart a communicating J^ght ^^^'
ofiset from the deep cardiac plexus.

The left coronary nerves are derived, as will be subsequently seen, and left ;
from the deep cardiac plexus, and follow the left coronary artery.

At first the nerves surround the arteries, but they soon leave the ending in
vessels, and ])ecoming smaller by subdivision, are lost in the muscular ^ ^ *
substance of the ventricles. On and in the substance of the heart
the nerves are marked by small ganglia.

The CAVITIES OF THE HEART may be examined in the order in Four cavi-
which the current of the blood passes through them, viz., right ^^eaiif*^^
auricle and ventricle, and left auricle and ventricle.

Dissection. In the examination of its cavities the heart is not to Dissection
be removed from the body. To open the right auricle, an incision auricle "
should be made in it near the right or free border, extending from
the superior cava nearly to the inferior cava ; and from the centre
of this cut the knife is to be carried across the anterior wall to the
appendix. By this means an opening will be made of sufficient
size ; and on removing the coagulated blood, and raising the flaps
with hooks or pieces of string, the cavity may be examined.

The CAVITY OF THE RIGHT AURICLE (fig. 168) is of an irregular Form of
form,* though when seen from the right side, with the flaps held "m-ide.
up, it has somewhat the appearance of a cone, with the base to the
right and the apex to the left.

The widened part or base of the cavity is turned towards the right Its base
side, and at its extremities are the openings of the superior and
inferior cavse. Between those vessels the wall projects a little, and
in some bodies presents a slight elevation (tubercle of Lower). The

* The term cavity of the auricle is sometimes confined to the part in the
appendix, and the name atrium or sinus vcnosus is then given to the rest of
the space here named am-icle.

458

DISSECTION OF THI^: THORAX.

and apex.

Interior of
appendix.

Crista
terminalis.

apex is prolonged downwards towards the junction of the auricle
with the ventricle, and in it is the opening into the right ventricular
cavity.

The anterior ivall is thin and loose. Near the top is an opening
leading into the pouch of the appendix, which will admit the tip
of the little finger. Near, and in the interior of the appendix,
are prominent fleshy bands, named miisculi pectinati, which run
mostly in a transverse direction, and form a network that contrasts
with the general smoothness of the auricle. The musculi pectinati,
end uj)on a common ridge, the crista terminalis.

The posterior {and inner) wall corresponds mostly with the septum

Thebesian valve.
Opening of coronary sinus
Eustachian valve.

Fossa oval is.

Annulus ovalis.

Fig. 168. — The Interior op the Right Auricle (prom the Front and
Right) ; the Curved Arrow points to the Auriculo- Ventricular
Opening.

between the auricles. On it, opposite the opening of the inferior
vena cava below, is a large oval depression, the fossa ovalis, which
is the remains of an opening between the auricles in the foetus.
A thin semitransparent structure forms the bottom of the fossa ;
and there is oftentimes a small oblique aperture into the left
auricle at its upper part. Around the upper three-fourths of the
fossa is an elevated band of muscular fibres, called annulus ovalis,
which is most prominent above and on the left side, and gradually
subsides below.
Apertures of At the lower end of the posterior wall, between the inferior
cavdl and the auriculo-ventricular orifices, is the aperture of the

Fossa
ovalis

Annulus
ovalis.

sinus

THE RIGHT AURICLE. 459

coronary siiuis. Other small apertures, named foramina of TJisbesius,
are scattered over this surface ; some lead only into depressions ;
but others are the mouths of veins of the substance of the heart
(smallest cardiac veins). vehif™*"^^

The chief aperUires in the auricle are those of the two cavse, Situation of
coronary sinus, and ventricle. The opening of the superior cava ^*^*'
is at the upper end of the auricle, and looks slightly forwards.
The inferior cava enters the lowest part of the cavity at the back,
close to the septum, and is directed inwards to the fossa ovalis.
The auriculo-ventricular opening is the largest of all, and is situate of aurieulo-
at the lower and fore part of the cavity. Between this and the ope\*iing|^*^
septum is placed the opening of the coronary sinus. of coronary-

All the large vessels, except the superior cava, have some kind of sinus,
valve. In front of the inferior cava is a thin fold of the lining Y-l^^** ^^
membrane of the cavity, the Eustachian valve, which is only a tures :
remnant of a much larger structure in the foetus. This fold is inferior
semilunar in form, with its convex margin attached to the anterior Eustadiian
wall of the vein, and the other free in the cavity of the auricle, '^aive;
The valve is wider than the vein opening ; and its surfaces are
directed forwards and backwards : it is often cribriform. The
aperture of the coronary sinus is covered by a thin fold of the one to core-
lining membrane, which is prolonged internally on to the Eustachian "^^ smus,
fold, and is known as the valve of Thebesim. The auriculo-ventri-
cular opening will be seen, in examining the right ventricle, to be and one to
provided with a tri-cuspid valve, which prevents the blood flowing ventricular
back into the auricle. opening.

In the adult there is but one current of blood in the right auricle Course of
towards the ventricle. But in the foetus there are two streams in ai^iJ"n.
the cavity ; one of pure, and the other of impure blood, which adult,
cross one another in early life. The placental or pure blood, and in the
entering by the inferior cava, is directed by the Eustachian valve
into the left auricle, through the foramen ovale in the septum ;
while the current of systemic or impure blood, coming in by the
superior cava, flows downwards in front of the other to the right
ventricle.

Dissection. To see the cavity of the right ventricle, the student To open
should raise outwards a Y-shaped flap of the anterior wall of the "e^iJiricie.
ventricle, as in fig. 169, the blunted apex of the V being below the
root of the pulmonary artery, its upper border being parallel with,
but about half an inch below, the auriculo-ventricular groove and
the lower border being well to the right of the inter- ventricular
furrow, so as to avoid injury of the inter-ventricular septum. In the
examination of the cavity of the right ventricle, both the flap and
the apex of the heart should be raised with hooks or string, so
that the space may be looked into from below.

The CAVITY OF THE RIGHT VENTRICLE (fig. 169) is triangular in Cavity of

form, with the base turned towards the auricle of the same side, "g^jllricie.
On a cross section it would appear semilunar in shape, the septum
between the ventricles being convex towards the cavity.

The apex of the cavity reaches the right border of the heart at Apex.

460

DISSECTION OF THE THORAX.

Base and its a sliort distance from the tip. The base of the ventricle is sloped,

openings. g^^^ jg perforated by two apertures ; one of these, to the right and
below, leading into the auricle, is the right auriculo-ventricular
opening ; the other, on the left and much higher, is the mouth
of the pulmonary artery. The part of the cavity leading up to the
pulmonary artery is funnel-shaped, and is named the infundibulum
or the conus arteriosus.

Anterior and The anterior wall, or the loose part of the ventricle, is compara-
tively thin, and forms most of the anterior surface of the ventricular

posterior portion of the heart. The ^posterior wall corresponds with the
septum between the ventricles, and is much thicker.

wall.

Probe in the
infundibn-
lum passing
out of the
pulmonary
artery.

Septal cusp.

Fig. 169. — The Interior of the Right Ventricle (from the Front ;
THE Heart being held so that the Apex is Lowest Down).

Interior of Over the greater part of the cavity the surface is marked by pro-
is uneve/: j^^^ting muscular bands, the columm^ carneoe ; but near the aperture
on it there of the pulmonary artery the wall becomes smooth. The fleshy
sets^of fleshy columns are of various sizes, and of three different kinds. Some
columns. form merely a prominence in the ventricle, especially on the septum.
Others are attached at each end, but free in the middle {traheculce
carnece). And a third set, which are fewer in number and much
the largest project into the cavity, and form rounded bundles.

THE RIGHT VENTRICLE. 461

named musculi papillares, which give attachment to the little
tendinous cords of the valve of the auriculo- ventricular opening.

The auriculo-ventricular orifice is situate in the base of the Opening
ventricle, and Ijehind the right half of the sternum, on a level auricle :
with the fourth intercostal space. It is oval in shape, and position,
measures about four inches in circumference, being slightly larger g^™.*"*^'
than the corresponding aperture of the left side.

Fixed around the opening is a large membranous valve, which is guarded
projects into the cavity of the ventricle. At its attached margin the cuspid
valve is undivided : but its lower part is notched, so as to form ^'^^^'«'
three pendent cusps or tongues, whence the name tricuspid is given
to it. Into the cusps are inserted small fibrous bands — the chordae Cusps :
tendinse, which unite them to the muscular wall of the ventricle.
The three cusps are thus placed ; one {marginal) is against the marginal ;
anterior wall of the ventricle ; posteriorly, another (septal) touches septal ;
the septum ; and the third {infu7uUbular), the largest and most iufundi-
moveable, is placed to the left, between the auriculo-ventricular ^^'
opening and the infundiljulum.

The tricuspid xalxe consists of a duplicature of the lining mem- Structure of
brane of the heart, enclosing fibrous tissue. The central part of
each tongue is strong, while the edges are thin and notched ; and
between the main pieces there are often thinner intermediate points.

The chordcB tendince, which keep the valve in place, ascend from attachment
the musculi papillares in the intervals between the cusps, and are nous^cords ;
connected in each space with the two pieces of the valve bounding
it. They end on the surface of the cusps turned away from
the opening, a few reaching the attached upper margin ; but the
greater number join the central thickened part, and the thin edge
and point of the cusp.

The papillary muscles are collected into two principal groups, papillary
an anterior sending its tendons to the marginal and infundibular
cusps, and a posterior^ to the marginal and septal cusps. In the
interval between the infundibular and septal segments of the valve
the tendinous cords are small, and spring from the septum.

As the blood enters the cavity the valve is raised so as to close
the opening into the auricle ; and its protrusion into the latter cavity
during the contraction of the ventricle is arrested by the small
tendinous cords. The closure of this valve assists in producing the
first sound of the heart.

The mouth of the pulmonary artery will be seen when the Pulmonary
incision in the anterior wall of the ventricle is prolonged into it. °"^^® •
The opening is circular, with a diameter of about an inch. It sizeand
occupies the summit of the funnel-shaped portion of the ventricle, ^"^ ^^^ '
and is placed opposite the upper edge of the third costal cartilage
of the left side, close to its junction with the sternum.

Pulmonary valve. Guarding the orifice of the pulmonary artery its valve of
is a valve consisting of three semilunar or sigmoid flaps ; a right ^^"^^ ^^P** '
and left anterior, and a posterior. Each flap is attached to the side
of the vessel by its convex border, and is free at the opposite edge,
in the centre of which there is a slightly thickened nodule — the

462 DISSECTION OF THE THORAX.

dilatation of corpus ArantU. In the wall of the artery opposite each Hap is a
ar ery. slight hollow — the sinus of Valsalva.

Structure of The valves are formed of fibrous tissue with a covering of the

^^ ^^ ' lining membrane. In each flap the fibres have tlie following

arrangement : there is one band along the margin of attachment ; a

second runs along the free edge and is connected with the projecting

nodule ; and a third set of fibres is directed from the nodule

across the flap, so as to leave a semilunar interval named lunula on

each side near the free edge.

and use. The use of the valve is obvious, viz., to give free passage to fluid

in one direction, and to prevent its return. While the blood is

entering the artery the flaps are separated ; but when the elasticity

of the vessel acts on the contained Idood they are thrown together

in the centre of the vessel, and arrest the flow of the fluid into the

ventricle. They are concerned in giving rise to the second sound

of the heart.

To open left Disscctioil. To open the cavity of the left auricle, the apex of

auricle. ^.j^^ heart is to be raised, and a cut is to be made across the posterior

surface of the auricle from the right to the left pulmonary veins

(see fig. 165, p. 453). Another short incision should be made

downwards at right angles to the first. The heart must necessarily

be held up during the examination of the cavity.

Form of The CAVITY OF THE LEFT AURICLE is smaller than that of the

Mt'audcie. ^'igl^t side, and is rather quadrilateral in shape, with its longest

diameter directed transversely. It is joined at each side by the two

pulmonary veins of that side : and at the lower and fore part it

opens into the left ventricle.

Appendix In the front wall, at the left extremity, is the opening of the

pecti^ath" ' appendix, which is longer and narrower than the corresponding

part on the right side. Musculi pectinati are also present, but on

this side they are usually confined to the appendix.

On septum To the right of the opening into the appendix, on the part of the

foramen ° "^"^'sll formed by the septum, is a superficial fossa, the remains of the

ovale. oval aperture through that partition ; this is bounded below by a

projecting margin, concave upwards, which is the edge of the valve

that closed the opening in the foetus. This impression in the left

auricle is above the fossa ovalis of the right cavity, because the

aperture between the two in the foetus was an oblique canal through

the septum.

Openings: The apertures in this auricle are those of the four pulmonary

four pulmo- veiiis, and the opening into the left ventricle. The mouths of each

nary vems, ^^^^^ ^^ pulmonary veins are close togetlier ; those from the right

and to lung open into the extreme right of the auricle against the septum,

and those from the left lung enter the opposite side of the cavity,

near the appendix.

Valves. The pulmonary veins have no valves. The aperture into the

ventricle will be subsequently seen to have a large and complicated

valve to guard it, as on the right side.

Current of In the adult the blood enters this cavity from the lungs by the

adult '^^ pulmonary veins, and flows into the left ventricle by the large

THE LEFT VENTRICLE. 463

opening between the two. In the foetus only a very small quantity in foetus,
of blood pajfses through the lungs ; and the left auricle receives its
pure blood from the inferior vena cava through the right auricle by
the aperture in the septum (foramen ovale).

Dissection. The left ventricle may be opened by an incision How to
along both the anterior and the posterior surfaces, near the septum ; ventricle,
these are to be joined at the apex, but are not to be extended
upwards so as to reach the auricle. On raising the triangular flap
the interior of the cavity will be visible.

The CAVITY OF THE LEFT VENTRICLE is longer and more conical Fonn of left
in shape than that of the opposite ventricle ; and it is oval, or almost ^^° "'^ ^'
circular, on a transverse section.

The ajpex of the cavity reaches the apex of the heart. The base Apex,
is turned towards the auricle ; and in it are the openings into the Base with
aorta and the left auricle. openings.

The waU of this ventricle is much thicker than that of the right. Wall,
and the anterior boundary is formed for the most part by the inter-
ventricular septum.

Its surface is irregular, like that of the right ventricle, in con- inner sur-
sequence of the projection of the columnae carnese ; but near the «^^gl^*^
aorta the surface is smoother. There are three kinds of fleshy columns columns,
in this as in the right ventricle. The large musculi papillares give and some
attachment to the tendinous cords of the auriculo-ventricular valve, ^'^^ ^*'^®-
and are more strongly marked than on the right side : they are
arranged in two great bundles, which spring from the rigid and left
sides of the cavity.

The left auriculo-ventricular opening is placed beneath the orifice Left auri-

of the aorta, but close to it, onlv a thin fibrous band interveningr ^"|° ventn-
' . ' ' o cnlar aper-

between the two. It is rather smaller than the corresponding ture :

aperture of the right side, being about three inches and a half in form and

circumference, and it is longest in the transverse direction. It is ^^^^ '■>

furnished with a membranous valve (mitral) which projects into

the ventricle.

The mitral valve is stronger and of greater length than the tri- Mitral
cuspid, and has also firmer and more tendinous cords ; it takes its ^'^^^'® '•
name from a fancied resemblance to a mitre. Attached to a fibrous
ring round the aperture, it is divided below by a notch on each
side into two pieces. Its segments lie one before the other, with
their edges directed to the sides, and their surfaces towards the
front and back of the cavity. The anterior, or aortic cus}!, of the aortic cusp;
valve intervenes between the auricular and aortic openings, and is
larger and looser than the posterior or marginal cusp. cu^^"*^

The mitral resembles the tricuspid valve in its structure and structure;
oflice. Its segments consist of thicker and thinner parts ; and in
the notches at the sides there are also thinner pieces between the
two primary segments. The chordae tendinse ascend to be attachment
attached to the valve in the notches between the tongues; and ° ^^^^'
they end on the segments in the same way as in the tricuspid valve.
Each of the large papillary muscles acts on both portions of the
valve.

464

DISSECTION OF THE THOKAX.

Position of
apertures

ofarteries,

pulmonary,
aortic ;

sounds
heard best

auriculo-
ventricular
openings :
left;

right.

Vessels
joining the
heart.

The pulmo-
nary artery

divides into
two for the
lungs.

Right
branch.

While the blood is entering the cavity, the cusps of the valve are
separated ; and when the ventricle contracts, they meet to close the
passage into the left auricle. In combination with the tricuspid it
assists in producing the first sound of the heart. The examination
of the aortic opening will be deferred until the large vessels at the
base of the heart have been studied ; it is described on page 473.

Surface marking of the valvular apertures. Two openings
have been seen in each ventricle, — one of the auricle of its own side
of the heart, and one of an artery.

The apertures of the arteries (aorta and pulmonary) are nearest
the interventricular septum ; and as the two vessels were originally
formed from one tube, they are close together ; but of the two, the
pulmonary artery is anterior and more to the left, as well as some-
what higher. As regards the surface the pulmonary valve is behind
the junction of the third left costal cartilage with the sternum near
the upper border of the cartilage and the aortic is just under cover
of the sternum opposite the lower part of the same cartilage.

The sound produced at the pulmonary orifice is heard l)est in the
second left intercostal space, and that produced at the aortic orifice
in the second right intercostal space.

The auriculo-ventricular openings are nearer the circumference
of the heart, and each is posterior to the artery issuing from the fore
part of its ventricle. The left auriculo-ventricular opening is
nearest of all to the back of the heart, and is marked on the surface
by a line extending inwards and a little downwards to the middle
of the sternum from the upper part of the fourth left costal cartilage
at its junction with the sternum.

Tlie right auriculo-ventricular opening is situated behind the
right half of the sternum opposite the fourth intercostal sj^ace in a
line passing downwards and a little to the right.

Dissection. The large vessels between the base of the heart
and the upper opening of the thorax will now be made ready
for examination and the parts upon which they lie carefully
cleaned.

Great Vessels. The arteries which take origin from the heart
are the aorta and the pulmonary trunk. The large veins entering
the heart, besides the coronary sinus, are the superior and inferior
cavse, and the pulmonary.

The pulmonary artery (fig. 163, p. 448, and fig. 164, p. 452),
is a short thick trunk, which conveys the dark blood from the right
side of the heart to the lungs. From its commencement in the
right ventricle the vessel is directed upwards and backwards on the
left of the aorta ; and at a distance of an inch and a half or two
inches, it divides into two branches for the lungs. The trunk of
the pulmonary artery is contained in the pericardium ; and beneath
its lower end is the beginning of the aorta. On each side are the
coronary artery and the auricular appendix.

The right branch is longer and somewhat larger than the left.
In its course to the lung it passes outwards above the right auricle
of the heart, and behind the aorta and superior vena cava.

THE PULMO]SARY ARTERY AND THE AORTA. 465

Behind it is the right bronchus. At the lung the artery divides
into three primary branches, one for each lobe.

The left branch is directed in front of the descending aorta and Left branch,
the left bronchus to the fissure of the lung, where it ends in two
branches for the two lobes.

As the right and left branches of the pulmonary artery pass Space at the
outwards, they cross the two bronchi diverging from the end of the ' "^^^tion.
trachea, and enclose with them a lozenge-shaped space which
contains some bronchial glands (fig. 163).

Ductus arteriosus (fig. 164). Near the bifurcation of the Ligament of
pulmonary artery a fibrous cord, about the size of a crow-quill, ^l]^^
passes from the left branch of the vessel to the arch of the aorta.
This is the remnant of the ductus arteriosus of the foetus, and is
named the ligament of the arterial duct.

In the foetus the right and left branches of the pulmonary artery Ai-teriai
are small, and the trunk is continued by the ductus arteriosus, fJ^^^J?
which opens into the aorta beyond the origin of the last great
branch (left subclavian) of the arch. The impure blood from the course of
superior venae cavse passes into the right ventricle and thence Diood.
proceeds by the pulmonary artery, whereby most of it reaches the
aorta through the arterial duct, below the attachment of the vessels
of the head and neck, in order that it may be transmitted to the
placenta to be purified. After birth, when the function of the
lungs is established, the great current of blood is directed along the
branches of the pulmonary artery to the lungs, instead of through
the arterial duct ; and this tube, becoming gradually smaller, is
occluded l)y the eighth or tenth day, and forms finally the ligament
of the arterial duct.

The AORTA (fig. 170, p. 466 ; and fig. 171, p. 467) is the great The aorta
systemic vessel which conveys the arterial blood from the heart to
the difterent parts of the body. It first ascends for a short distance,
and then arches backwards to reach the spinal column, along which through
it is continued downwards through the chest and abdomen. In the a^ufeli!
thorax the vessel is divided into three parts — the ascending aorta,
the arch of the aorta, and the descending thoracic aorta.

The ASCENDING AORTA springs from the left ventricle of the Ascending
heart behind the left half of the sternum, on a level with the *^^ "
lower border of the third costal cartilage. About two inches, or length,
a little more, in length, it is directed upwards, with a slight
inclination to the right and forwards, and reaches to the inner end extent,
of the cartilage of the second rib on the right side. It is contained and
nearly altogether in the pericardium, being surrounded by the '■^'*^*^'*''-
same sheath of the serous membrane as the pulmonary trunk,
which is at first superficial to it, but afterwards lies on its left
side. Between the ascending aorta and the sternum are the
anterior edge of the right lung, with the pleura, and some fatty '
tissue. Behind it are the left auricle of the heart and the right
branch of the pulmonary artery. On the right side is the
descending cava. Near the heart the vessel bulges opposite the
flaps of the valve (sinuses of Valsalva ; tig. 170). There is

D.A. H H

465

Arch of
aorta

forms two
curves :

relations.

Objects con-
tained in the
arch.

Three

branches of
the arch.

DISSECTION OF THE THORAX.

sometimes another dilatation along the right side, ^vhich is named
the great si7ius of the aorta.

Branches. From the lower end of the ascending aorta arise the
two coronary arteries of the heart (fig. 170, o), which have already
been noticed (p. 455).

The ARCH OF THE AORTA extends from the second right costal
cartilage to the lower border of the body of the fourth dorsal
vertebra, on the left side. The convexity of the arch is upwards,
and from it the three large arteries for the supply of the upper

part of the body arise,
f . ^ The vessel recedes from

the sternum, being at
first inclined to the
left across the front of
the trachea, and then
directed backwards to
the left side of the
fourth dorsal vertebra,
where it turns down-
wards to join the de-
scending aorta. It thus
forms a second curve
with the convexity to
the left side.

The arch rests upon
the trachea, the ceso-
phagLis, the thoracic
duct, and the fourth
dorsal vertebra. In
front of it are the
remains of the thymus
gland, and some fat.
On the left side are the
left pleura and lung,
and the left ])hrenic,
superficial cardiac, and
vagus nerves, the last
sending inwards its
recurrent branch beneath the vessel. Along the upper border, in
front of the great branches, is the left innominate vein (fig. 171),
to which the left upper intercostal vein is directed over the hinder
part of the arch ; and to the lower border, near its termination,
the remnant of the arterial duct is attached.

Below the concavity of the arch of the aorta are the root of the
left lung, the branching of the jjulmonary artery with its arterial
duct, and the left recurrent laryngeal nerve.

The three large branches of the arch supply the neck, the head,
and the upper limbs. First on the right is the trunk of the
innominate artery ; close to it is the left common carotid ; and last
of all comes the left subclavian.

170. — Arch of the Aorta and
Great Branches.

Aortic arch.

vein.

Innominate artery.

Right innominate

Left common caro-

vein.

tid.

Left upper inter-

Left subclavian.

costal vein.

Ligament of arterial

Large azygos vein.

duct.

Left subclavian vein.

Vena cava superior.

Thoracic duct.

Left innominate

Coronary artery.

THE INNOMINATE ARTEKY.

467

The INNOMINATE ARTERY (brachio-cephalic), the first and largest innominate
of the three branches, measures from one inch and a half to two ^n^^^JoJJS^'*

Groove formed by
subclavian arterj-,

Superior inter-
costal vein.

.Left innominate
vein.

Groove formed
by left innomi-
nate vein.

Right coronary artery.

Fig. 171. — The Contents of thr Thorax seen from the Front. The
Lungs were Filled with Melted Wax and were held Apart in
Front until the Wax had set. (From a Specimen in Charing
Cross Hospital Museum.)

inches in length. Ascending to the right beneath the sternum, and sub-
it divides opposite the sterno-clavicular articulation into the right '^^^^i*" •
common carotid and subclavian arteries.

H H 2

4G8

DISSECTION OF THE THORAX.

relations

Left com-
mon caro-
tid:

relations in
the thorax.

Left snb-
clavian
artery :

course and
relations in
the chest.

The great
veins are :—

Vena cava
superior :

formed by
innominate
veins ;

course ;

relations ;

branches.

The artery is crossed by the left innominate vein, and lies
behind the upper piece of the sternum, and the origins of the
sterno-hyoid and sterno-thyroid muscles. At first it rests on the
trachea, but as it ascends it is placed on the right side of the air-
tube. To its right is the innominate vein of the same side. Usually
no lateral branch arises from this artery.

Left common carotid artery. The common carotid artery
of the left side of the neck is longer than the right by the distance
between the arch and the top of the sternum.

In the thorax the artery ascends obli(.j[uely to the left sterno-
clavicular articulation, but not so close as the innominate to the
first piece of the sternum and the origin of the depressor muscles
of the hyoid bone and larynx. In this course it passes beneath
the left innominate vein, and the remains of the thymus gland.
At first it lies on the trachea, but afterwards inclines to the left
of that tube, so as to be placed over the esophagus and the thoracic
duct. To its outer side is the left vagus, with one or more cardiac
branches of the sympathetic nerve.

The LEFT SUBCLAVIAN ARTERY ascends to the neck through the
upper aperture of the thorax, and then curves outwards between the
scaleni, where it has the same relations as the vessel of the right side.

The trunk is directed almost vertically from the arch of the
aorta to the level of the first rib. In the thorax it is deeply placed,
near the spine. To its inner side is at first the trachea, and after-
wards the oesophagus with the thoracic duct. On its outer side it
is invested by the left pleura, and in the hardened specimen its
position is represented by a shallow groove in the lung, in which
it rests. The left innominate vein crosses in front of the vessel as
it enters the neck. Somewhat anterior to the artery, though
running in the same direction, are some of the cardiac nerves.

Veins. In addition to the cardiac veins, there are the superior
and inferior cavae, and the pulmonary veins ; — the former are the
great systemic vessels which return impure blood to the right auricle
of the heart ; and the latter convey pure blood from the lungs to
the left auricle.

The superior or descending vena cava (fig. 170, /, and
fig. 171) results from the union of the right and left innominate
veins, and brings to the heart the blood of the head and neck, upper
limbs, and thorax.

Its origin is placed behind the junction of the first costal cartilage
of the right side with the sternum. From that sjjot the large vein
descends to the pericardium, perforates the fibrous layer of that bag
about one inch and a half above the heart, and ends in the right
auricle. On its outer surface the vein is covered by the pleura, and
the phrenic nerve is in contact with it. To the inner side are the
innominate artery and the ascending aorta. Behind the vein is the
root of the right lung.

When the cava is about to perforate the pericardium it is joined
posteriorly by the large azygos vein ; and higher up it receives
small veins from the pericardium, and the parts in the mediastinum.

tributaries.

THE INNOMINATE VEINS. 469

The INNOMINATE VEINS are two in number, right and left ; and innominate
each is formed near the inner end of the clavicle by the junction of ^^^"^•
the subclavian and internal jugular veins. Below, they are united
in the superior cava. The trunks differ in length and direction,
and in their relations tc surrounding parts (fig. 171).

The right vein is about one inch long, and descends almost right,
vertically, on the right side of the innominate artery, to its junction
with the opposite vein. On the outer surface the pleura covers it,
and along it the phrenic nerve is placed.

The left vein is nearly three inches in length, and is directed and left ;
obliquely to the right, along the upper border of the arch of the
aorta. It crosses behind the sternum, and the remains of the
thymus gland ; and it lies on the three large branches of the aortic
arch, as well as on the nerves descending over the arch.

The tributaries of the veins are nearly alike on the two sides, their
Each receives the vertebral and the internal mammary of its own
side, and occasionally the inferior thyroid, though these veins more
often l)lend into one trunk below, which opens into the junction
of the two innominate veins or into the left. The left vein also
is joined in addition by the superior intercostal, and some small
thymic and pericardial veins.

Occasionally the innominate veins are not united in the vena cava, but Sometimes
descend separately to the heart, where each has a distinct opening in the ^^^y op^'i
right auricle. When such a condition exists, the right vein takes the course j'nto ttie
of the upper cava in front of the root of the right lung ; but the left vein heart,
descends in front of the root of the left lung, and turning to the back of the
heart, receives the cardiac veins, before it opens into the right auricle. A
cross branch generally connects the two above the arch of the aorta.

This occasional condition in the adult is a regular one at a very early period
of the growth of the foetus ; and the two vessels are also persistent in some
mammalia.

Change of the two veins into one. The changes taking place in the veins How two
during fcetal growth, to produce the usual arrangement in the adult, concern are changed
the trunk on the left side. The following is an outline of them. First a *"^^ ^^^'
cross branch is formed between the two trunks, and this enlarging gives rise
to the left innominate vein. Then the left trunk below the cross branch dis-
appears at its middle, and undergoes transformation at each end : — At the
upper end it becomes convei-ted into a part of the superior intercostal vein, and coro-
At the lower end it remains pervious for a short distance as the coronary sinus ; °^P' sinus
and the small oblique vein opening into the end of that sinus in the adult is a ^^^ '
remnant of the trunk as it lay beneath the heart.

In the adult there is a trace of the occluded vessel in the form of a small
fibrous band in the vestigial fold of the pericardium (p. 451).

The INFERIOR OR ASCENDING VENA CAVA enters the right Vena cava
auricle as soon as it has pierced the diaphragm. No branches join ^" ^"°'^'
the vein in the thorax.

The PULMONARY VEINS are two on each side, upper and lower. Fourpui-
They issue from the hilum of the lung, and end in the left auricle : "e^ns.'^^
their position in regard to the other vessels of the root has been
noticed at p. 449.

The right veins are longer than the left, and lie beneath the Right veins
right auricle of the heart. The superior receives its roots from ^ o"ser.

470

DISSECTION OF THE THORAX.

Left veins.

the upper and middle lobes of the hmg ; and the inferior vein is
formed by branches from the lower lobe.

The left veins cross in front of the descending aorta ; and one
springs from each lobe of the lung.

NERVES OF THE THORAX.

Nerves of
the thorax.

To trace
vagus.

Plircnic
nerve from
the cervical
jjlexus,

passe.s to
diaphragm.

Right nerve
above root
of lung.

Left nerve
above root.

Some off-
sets.

Internal

mammary

artery

gives

phrenic

branch.

The pneumo-gastric and the sympathetic nerves supply the viscera
of the thorax ; and the phrenic nerve courses through the cavity to
the diaphragm.

Dissection. The phrenic nerves have already been fully
displayed ; but the pneumo-gastric nerves are now to be prepared.

The vagus is to be followed, on each side, behind the root of the
lung, and its large plexus in that position is to be dissected out,
the lung being thrown well over to the opposite side : some fine
l>ranches from the gangliated cord of the sympathetic coining for-
wards over the sjjinal column to the plexus, must also be looked for.
The vagus also supplies a few filaments to the front of the root.
Beyond the root, the nerve is to be pursued along the oesophagus
by raising the lung and removing the pleura.

The PHRENIC NERVE is derived from the anterior division of the
cervical plexus ; from the fourth and fifth cervical nerves, mainly
from the fourth. In its course through the thorax it lies along the
side of the pericardium, and at a little distance in front of the root
of the lung, with a small companion artery. When near the dia-
phragm it divides into branches, which perforate the muscle, and
are distributed on the under service. The nerves of opposite sides
differ in length, and in their relations above the root of the lung.

The right nerve is shorter and straighter than the left. On enter-
ing the chest it crosses behind the subclavian vein, ])ut in front of
the internal mammary artery ; and it lies afterwards along the
right side of the innominate vein and superior cava till it reaches
the pericardium.

The left nerve crosses the subclavian artery, and has the same
position as the right to the mammary vessels when entering the
cavity. In the thorax it is directed over the arch of the aorta to
the root of the lung, and makes a curve lower down around the
projecting heart. Before reaching the aorta the nerve is placed
external to the left common carotid artery ; and it inclines
gradually from without inwards, so as to be in front of the left
vagus over the aortic arch.

Branches. Some small filaments are said to be furnished from
the nerve to the pleura and pericardium.

Internal mammary artery. A small part of this artery,
which lies beneath the first rib, and winds round the phrenic
nerve and the innominate vein to reach the side of the sternum, is
now to be seen. It gives the following off"set : —

The superior phrenic branch (comes nervi phrenici) is a very
slender artery, which accompanies the phrenic nerve to the dia-
phragm, and is distributed to that muscle, anastomising therein

THE PNEUMO-GASTRIC NERVE. 471

Avitli the phrenic artery from the aorta, and with the musculo-
phrenic branch of the internal mammary.

The PNEUMO-GASTRIC or VAGUS NERVE passes through the thorax Vagus
to the abdomen. In the lower part of the thorax the right and left "®''^®-
nerves have a similar position, for they pass behind the root of the
lung, each on its own side, and along the cesophagus to the stomach.
But above the root of the lung, the two nerves have different rela-
tions. Each supplies branches to the viscera, viz., to the heart, the
windpipe and lungs, and the gullet.

The right vagus enters the thorax between the subclavian artery Right vagxis
and the innominate vein, and is directed obliquely backwards, 0^^^™°*
by the side of the trachea, to the posterior aspect of the root of the
lung, where it gives rise to the posterior pulmonary plexus. From and on
the plexus two large offsets are continued to the back of the gullet, ^^opWus
and unite below into one trunk, which reaches the posterior surface
of the stomach.

The left nerve appears in the thorax on the outer side of the left Left nerve
common carotid artery, and courses over the arch of the aorta, and of lung^^
beneath the root of the lung, forming there a larger plexus than on
the right side. From the pulmonary plexus one or two branches and on
pass to the front of the oesophagus, and join with offsets of the ^gopjj'ao-us
right nerve in a plexus ; but the pieces are collected finally into
one trunk, which is continued on the front of the gullet to the
anterior part of the stomach.

The branches of the pneumo-gastric nerve seen in the thorax are Branches
the following : — are:—

a. The recurrent or inferior laryngeal nerve, arising on the right Recurrent
side below the subclavian artery, and on the left at the lower ^*''y"g^*i-
border of the arch of the aorta immediately external to the ductus
artenosus, bends inwards to the trachea, along which it ascends to
the larynx. On each side this branch is freely connected with the
cervical cardiac branches of the sympathetic nerve, especially on
the left side beneath the arch of the aorta.

6. Cardiac branches {thoracic). Besides the cardiac branches fur- Cardiac
nished by the vagus in the neck, other offsets pass in front of ^'"^"^^^^ •
the trachea to the cardiac plexus. On the right side they come
from the trunk of the vagus and the recurrent branch, but they
are supplied by the recurrent nerve alone on the left side.

The termination of the lower cervical cardiac branch of each lower cervi-
vagus nerve may now be seen. The branch of the right nerve branch.'**^
lies by the side of the innom.inate artery, and joins a cardiac offset
of the sympathetic of the same side ; and the branch of the left
vagus crosses over the arch of the aorta, to end in the superficial
cardiac plexus (p. 457).

c. Pulmonary branches. There are two sets of nerves for the Pulmonary
lung, one on the anterior and the other on the posterior aspect
of the root.

The anterior branches, two or three in number, are small, and small
communicate with filaments of the sympathetic on the pulmonary ^^ ®"<*^»
artery : these nerves are best seen on the left side.

472 DISSECTION OF THE THORAX.

large pos- The posterior branches are larger and much more numerous.

tenor form forming a plexiform arrangement (posterior pulmonary plexus)

behind the root of the lung by the flattening and splitting of the

trunk of the nerve, they are joined by filaments from the third and

fourth ganglia of the knotted cord of the sympathetic, and are

conveyed into the lung on the divisions of the airtube.

CEsophageal d. (Esophageal branches are furnished to the gullet, but in

foirm^a^^ greatest abundance in the lower half. Below the root of the lung

plexus. the liranches of the pneumo-gastric nerves surround the oesophagus

with a network [jplexus gulce).
Sympathetic SYMPATHETIC Nerve. In the thorax the sympathetic nerve con-
conSs'of ®^®^^ °^ ^ knotted cord along each side of the spinal column, which
communicates with the spinal nerves ; and of a large prevertebral
or cardiac plexus, which distributes branches to the heart and the
luDgs.
a gangiiated The gangUated cord will be seen in a future stage of the dissec-
cord, tion, after the heart and the lungs have been removed,

and a cen- The CARDIAC PLEXUS lies over the lower end of the trachea, and

trai cardiac above the bifurcation of the pulmonary artery. A part of this
network, the superficial cardiac plexus, has been already described
on page 457. The remaining part, or the deep cardiac plexus, is
placed l)eneath the arch of the aorta.
Dissection Directions. The cardiac plexus has been injured by the previous
iiiexus- examination of the heart, so that it should be dissected in a body
in which the heart and the large vessels are entire, but the student
should make them out in his part as well as he can.
to expose Dissectloil. The ascending aorta is to be cut across near the

part,'^^^ heart, and is to be drawn over to the left side, after the manner of
fig. 163, p. 448 : next, the upper cava is to be divided above the
entrance of the azygos vein, and its lower part is to be thrown
down. By the removal of some fibrous and fatty tissues and
lymphatic glands, the right part of the plexus will be seen in front
of the trachea, above the right branch of the pulmonary artery.
The off'sets to the heart should be followed downwards on the trunk
of the pulmonary artery ; and those to the lung should be traced
along the right branch of that vessel.

To lay bare the part of the plexus into which the nerves of the

and the left, left side enter, the aorta is to be cut through a second time, between

the subclavian artery and the attachment of the ligament of the

ductus arteriosus ; and the arch is to be turned upwards with the

great vessels attached. The lymphatic glands and the areolar and

fatty tissue being cleared away from the plexus as on the opposite

side, the off'sets to the left coronary plexus of the heart will be visible.

Deep cardiac The deep cardiac plexus is situate between the trachea and the arch

plexus. Qf ^Yie aorta, and consists of right and left halves, which are joined

by cross branches. In it are united the cardiac nerves of the

sympathetic and vagus, with the exception of two branches of the

left side ; and from it nerves are furnished to the heart and lungs.

Right part, The right part of the plexus is placed above the right branch of

ow orme ; ^^^ pulmonary artery, and receives the nerves of the right side,

THE CARDIAC NERVES. 473

viz., the cardiac nerves of the sympathetic in the neck, the cardiac
branches of the trunk of the vagus in both the neck and chest, and
the cardiac offsets of the recurrent branch.

The branches of this half of the plexus are distributed mostly to branches to
the right side of the heart, and pass downwards before and behind "fiy^pie^Js;
the right branch of the pulmonary artery ; those in front run on the
trunk of the pulmonary artery to end in the right coronary plexus
(p. 457) ; and the nerves behind supply the right auricle of the
heart. Offsets are sent laterally on the branch of the artery to the
root of the lung. rooTonung.

The left half of the 'plexus lies close to the ligament of the arterial Left part :
duct, and rather on the left of the trachea. In it are collected the entering it;
cardiac nerves of the sympathetic ganglia of the left side of the
neck, except the highest, and numerous and large branches of
the left recurrent nerve of the vagus.

Nerves descend from it to the heart around the left branch and offsets end
the trunk of the pulmonary artery, and after supplying branches to n"ary^piexus,
the left auricle, terminate in the left coronary plexus (p. 457).
A considerable offset is directed forwards by the side of the ligament
to the superficial cardiac plexus ; and some nerves reach the left and in root
anterior pulmonary plexus by coursing along the branch of the ^^^""g-
pulmonary artery.

Termination of the three cardiac branches of the sympathetic nerve other car-
of the neck (upper, middle, and lower). diac nerves.

On the right side there may be only two cardiac nerves entering The right
the thorax, for the highest nerve is often blended with one of pi^u.J^^^
the others. These nerves pass beneath the subclavian artery to the
right half of the deep plexus ; and they communicate with the
branches of the recurrent laryngeal nerve of the vagus.

On the left side the highest cardiac nerve lies over the arch of the One left
aorta, and ends in the superficial cardiac plexus ; it may give a superticial ;
branch beneath the arch to the deep plexus. Only one other nerve, ^n others
the middle cardiac, is usually seen entering the left side of the deep plexus,
plexus, as the lower one generally blends with it.

OPENING OF THE AORTA AND STRUCTURE OF THE HEART.

Dissection. The aorta having been cut across, the student will
examine its interior as it springs from the heart.

The opening of the aorta is anterior to that of the auricle, and Aortic open-
close to the septum. This aperture is round, and rather smaller *°^ '
than that of the pulmonary artery, measuring slightly less than an size and
inch in diameter. position;

In its interior is a valve of three semilunar or sigmoid flaps, valve,
which are thicker and stronger than the corresponding parts in the
pulmonary artery, but have a like structure and attachment (p. 461),
The projection in the centre of each valve, the corpus Arantii, is
better marked. Opposite each valve the coat of the aorta is bulged
as in the pulmonary artery, though in a greater degree, and forms

474 DISSECTION OF THE THORAX.

Sinuses of a hollow on the inner side, named sinus of Valsalva, The
Valsalva. cusps of the valve are an anterior and a right and left posterior in
relative position, and the right coronary artery arises in the anterior
sinus of Valsalva, and the left in the left posterior sinus.
Use. Like the valves in the pulmonary artery, these meet in the middle

to prevent the blood passing back into the ventricle, and combine
with them in causing the second sound of the heart.
Structure of STRUCTURE. The heart is composed chiefly of muscular fibres,
the heart, together with certain fibrous rings and a fibro-cartilage.

Dissection. The auricles should now be snipped round at their
junction with the ventricles, and the pulmonary artery and aorta
similarly cut round close to the attachments of the cusps of the
valves. The ventricular portion of the heart can then be cut
away and a view of the four valvular orifices obtained, and sections
should be made through them to demonstrate the fibrous rings
around the orifices.
Fibrous The fibvous structure forms rings around the auriculo-ventricular

bands ^^-^^ arterial orifices, and is prolonged into the valves connected

with these openings,
form rings The auriculo-ventricular rings give attachment to the framework

around auri- of fibrous tissue in the tricuspid and mitral valves ; and the band

culo-ventn- ^ -, n . -, • ^ ■• ^ ■,-,', •

cuiar surroundmg the left auriculo-ventricular opening is Idended m

front with the aortic ring,
and arterial The arterial rings surround the aortic and pulmonary orifices ;
openings. ^^^ ^^^ margin of each towards the artery forms three notches
with intervening projections. The notches are occupied by
thinner parts of the arterial wall bounding the sinuses of
Valsalva ; and to the concave edges the sigmoid flaps of the
valve are attached.
Fibro-carti- Behind the aortic opening, between it and the auriculo-
lage. ventricular apertures, is a piece of fibro-cartilage, with which the

fibrous rings are united.

Dissection. The inter- ventricular septum should now be cut
through from below upwards.
The inter- ^he interventricular septum appears as a stout pyramidal

ventricular muscular mass, between the two ventricles, but it will be seen that
sep um. ^^^ muscular tissue ceases close to the aortic orifice, and that, for a
short distance at the upper part, the ventricles are only separated by
a fibrous septum (pars membramacea septi). Sometimes a communi-
cation between the two ventricles occurs at this place, occasioning
one of the forms of congenital malformation of the heart.
Special The STRUCTURE OF THE HEART beyond the stage already described

needed*^'""" cannot be followed in the ordinary dissecting-room preparation, and
the further details can only lie followed in a heart that has been
specially prepared. For this purpose a fresh heart is obtained
(commonly of a sheep or an ox), which, having been washed out, is
filled with a mixture of flour and water, and boiled for a quarter of
an hour, so as to destroy the connective tissue, and to allow the
stretched and hardened muscular fasciculi to be separated from
one another.

THE MUSCULAR FIBRES OF HEART.

475

Until such a specimen is obtained, the student may omit the
following description.

The muscular fibres of the heart, although involuntary, are striped ; but
they differ in their character from those of the voluntary muscles. The
fibres of the auricles are distinct from those of the ventricles.

In the wall of the auricles the fibres are mostly transverse (fig. 172. a, b),
and are best marked near the ventricles, though they form there but a thin
layer ; and some of the fibres dip into the septum between the auricular
cavities. Besides this set, tlieie are annular fibres surrounding the Jfppen-
dat^es of the auricles and the endings of the different veins ; and lastly,
a few looped fibres (c, d) pass
obliquely over the auricle from
front to back.

Dissection. The auricles having
been learnt, separate them from
the ventricles by dividing the
fibrous auriciUo- ventricular rings.
Kext clean the fleshy fibres of the
ventricles by removing all the fat
from the base of the heart around
the two arteries (aorta and pul-
monary), and from the anterior
and posterior surfaces.

Before cutting into the heart,
let the student note that the
anterior surface is to be recog-
nised by the fibres turning in at
the septum, with the exception of
a small band at the base and
another at the apex ; while on the
posterior aspect the fibres are
continued from the left to the
right ventricle across the septum.

To show the direction of the
muscular bundles in the left ven-
tricle, divide the superficial fibres
in front longitudinally near the
septum, and transversely about
half an inch below the left auri-
culo- ventricular opening ; and re-
flect a thin layer of the fibres
carefully towards the left side.
In the same way a second layer
is to be reflected ; then a third,
and so on, each layer that is
raised being about as thick as

the thin end of the scalpel. It will not be difllicult to demonstrate thus six or
seven layers in the wall ; and as each is raised, the fleshy fibres will be seen
to change their direction (fig. 173).

On the right side a similar dissection may be made, and a like number of
layers may be displayed, but greater care will be necessary owing to the
thinness of the wall. Make a vertical cut along the anterior aspect from the
root of the pulmonary artery to the apex of the ventricle ; and reflect the
several layers inwards and outwards. As the superficial ones are raised,
their fibres may be followed into the septum in front, and across the middle
line into the wall of the left ventricle at the back.

Thickness of the ventricular walls. The wall of the left ventricle is in
general nearly three times as thick as that of the right. Its thickest part is about
one-fourth of its length from the base ; and at the apex it is very thin. The
free wall of the right ventricle is of more uniform thickness than the left.
The septum is about as thick as the wall of the left ventricle, except at the

Muscular
substance of
heart.

Fibres of
the auricles

are trans-
verse,

annular,

and looped.

Fig.

-McscuLAR Fibres
Auricles.

a. Transverse fibres of the right, and
b, of the left auricle.

c. Looped fibres of the left, and d, of
the right auricle.

e. Superior cava.

/. Inferior cava.

g. Right, and h, left pulmonary veins.
Annular fibres surround the veins.

and of
right.

Thickness
of left ven-
tricle,

of right,

and of
septum :

476

DISSECTION OF THE THORAX.

membra-
nous part of
septum.

Fibres can
be separated
into layers
by dissec-
tion.

Direction of
flbres :

external,
middle,

and internal.

Course of
fibres is
obscure.

Chief sets

external
oblique

and internal
longitudinal
are one ;

annular;

looped of
left,

upper end, in a small area close below the aortic orifice, where there is a
very thin part from which muscular fibres are absent {pa7's mcmhranacea
septi.

Arrangement of fibres. It has been shown by the foregoing dissection
that the direction of the muscular fasciculi composing the ventricular wall
varies at different depths from the surface, and that at a given spot a number
of layers may be separated, which are characterised by the difference in
direction of their fibres. Such a division into distinct layers is, however, in
great measure artificial, for the change in direction is gradual, and many
fibi-es pass across from one layer to another, and have to be cut to effect the
separation .

Over both ventricles the most superficial fibres ai-e directed very obliquely
from base to apex, and from right to left on the anterior surface, from

left to right on the posterior sur-
face. Proceeding inwards, the
obliquity gradually diminishes ;
and in the centre of the wall the
fibres are transverse. Within the
last, as the cavity of the ventricle
is approached, the fibres become
oblique again, but in the opposite
direction to the external ones ;
and the innermost fibres of all
are nearly longitudinal.

The attempt to trace the whole
course of the bundles is, except
in the case of the superficial
fibres, attended with great diffi-
culty, owing to the interlacement,
branching, and joining of the
fasciculi. The principal groups
of fibres that have been dis-
tinguished may be arranged as
follows ; but it must be under-
stood that they are to a great
extent intermixed, and that
bundles frequently pass from one
set into another.

a. The external oblique fibres
(fig. 173) begin at the base of the
ventricles, where most of them
spring from the auriculo-ventri-
cular and arterial fibrous rings,
and descend with the spiral
course above described to the
apex of the heart. On the pos-
teinor surface they pass vi^ithout
inteiTuption from the left to the
right ventricle ; but in front the
fibres crossing the right ventricle in part dip in at the interventricular groove
to the septum, while those continued to the left ventricle are joined by others
which issue from the septum along the furrow. At the apex of the heart
they form a sharp twist, known as the vortex or whorl, and sink in it to
become deep and ascend towards the base as the innennost layer of the left
ventricle. Some of them are continued to the base and join the auriculo-
ventricular and aortic rings ; but others enter the papillary muscles, which
are thus formed.

b. The transverse or annular fibres (fig. 173) are partly special to the
left ventricle, and partly common to the two ventricles. Some of them
apjjear to form simple rings round the cavities, but a great many pass from
this into the oblique sysfem of fibres.

c. The looped fibres of the left ventricle spring from the fibrous rings

Fig. 173.— a Diagram of the Arrange-
ment OF THE Fibres in Layers in the
Lekt Ventricle. The Dissection is
carried through about two-thirds
of the thickness of the wall.

1, 2, 3. Outer layers, the fibres of which
gradually become less oblique.

4. Middle layer of transverse fibres.

5, Inner set of oblique fibres. The
deepest fibres, corresponding to 1 and 2 of
the exterior, are not shown.

THE TRACHEA AND BRONCHI. 477

at the base, and passing downwards in the ventricular wall, enter the lower
part of the septum, in which they ascend to the central fibro-cartilage.

d. Similar looped fibres pass from the outer wall of the right ventricle and of right
through the septum to the fibro-cartilage. ventricle;

e. The figure-of-8 fibres pass from the front of the right ventricle through figure-of-8
the septum to the back of the left, and from the front of the left to the back fibres.

of the right, the two sets decussating in the septum.

Endocardium. Lining the interior of the cavities of the heart is a thin Lining
membrane, which is named endocardium. Ic is continuous on the one hand "l^^*^^"tu.
with the lining of the veins, and on the other with that of the arteries. ° e ea .
Where the membrane passes from an auricle to a ventricle, or from a
ventricle to an artery, it forms duplicatures in which fibrous tissue is
enclosed, thus giving rise to the valves ; and in the ventricles it covers the
tendinous cords, and the projecting muscular bundles. The thickness of the
membrane is greater in the auricles than in the ventricles, and in the left
than in the right half of the heart.

THE TRACHEA AND LUNGS.

Dissection. To see fully the pieces of the air-tube in the root
of the lung, it will be necessary to divide the branches of the
pulmonary artery and the pulmonary veins. And when the upper
part of the arch of the aorta is turned to one side, the dissector will
be able to clear away the bronchial glands, the nerves, and the
connective tissue from the part of the trachea in the thorax, and
from the branches into which it bifurcates.

The TRACHEA, or windpipe, reaches from the larynx to the Trachea
lungs, and lies on the front of the spinal column. The tube begins
opposite the sixth cervical vertebra ; and it ends commonly at the ends in
lower border of the fourth dorsal vertebra by dividing iuto two
pieces (bronchi), one for each lung.

In the thorax (fig. 163, p. 448) the trachea is situate with the its relations
great vessels in the superior mediastinum ; and its lower end is thorax,
usually inclined somewhat to the right side. Here it is covered by
the left innominate vein, by the arch of the aorta, with the origins
of the innominate and left common carotid arteries, and by the
cardiac plexus of nerves. Behind the airtube is the oesophagus,
which projects to the left above the arch of the aorta. On the
right side are the pleura, the vagus, and the innominate artery for
a short distance, after this has passed over the trachea ; and on the
left side lie the left subclavian artery, and the recurrent branch of
the vagus.

The BRONCHI, or the branches of the airtube, are contained in the Bronchi lie
roots of the lungs, and are surrounded by vessels, glands and nerves, of the lungs;
Near the lung each is divided into as many primary pieces as there
are lobes. In their structure and form the bronchi resemble the are like the
windpipe, for they are round and cartilaginous in front, but flat, {qJiu!^* '"
and muscular and membranous behind. Their position behind the
other pulmonary vessels has been described at p. 449.

The right hr&nchus is about an inch in length, and is larger than The right
the left ; it also forms a more direct continuation of the trachea, tie^'^ ^
from which circumstance a foreign body in the airtube is more
likely to enter this bronchus. It passes obliquely outwards, on a

478

DISSECTION OF THE THORAX.

left in size
and rela-
tions.

Remove the
lungs.

Take away
heart and
pericardium.

Surface of
lung is
smooth ;
is marked
by lobules
and small
cells.

Colour
varies with
age.

Accidental
colour.

Consistence.

Crepitation,

and elasti-
city.

Specific
gravity,

and weight
of the lung.

Lung con-
sists of
lobules, and
these of air-
cells.

level with the fifth dorsal vertebra, behind the upper cava and the
right pulmonary artery ; and the azygos vein arches above it.

The left biwichus is about two inches long, and reaches to the
level of the sixth dorsal vertebra. It is directed obliquely down-
wards below the arch of the aorta, and crosses behind the corre-
sponding pulmonary artery. It lies in front of the oesophagus and
descending thoracic aorta.

Dissection. The lungs are now to be removed from the body
by cutting through the bronchi and the small vessels of the root.

The remains of the heart and pericardium are then to be taken
away ; the inferior cava is to be divided, and the pericardium is to
be detached from the surface of the diaphragm : in removing the
pericardium, the dissector should be careful not to injure the
structures contained in the interpleural space in front of the spine.

Physical characters of the lung. The surface of the lung
is smooth and shining, and is invested by the pleura. Through the
serous covering the mass of the lung may be seen to be divided
into small irregularly shaped pieces or lobules. On looking closely
at it, when a piece of pulmonary pleura is pulled away from its
substance, minute cells will be perceived in it.

The tint of the lung varies with age. In infancy the colour is a
pale red ; but in the adult the texture becomes greyish, and presents
here and there dark grey s]3ots or lines of pigment, the shade of
which deepens with increasing age, and becomes even black in old
people. After death, the colour of the posterior border may be
bluish-black from the accumulation of blood.

To the touch the lung is soft and yielding, and on a section the
pulmonary substance appears like a sponge ; but the lung which
is deprived of air by pressure has a tough leathery feel. Slight
pressure with the thumb and finger drives the air from the con-
taining spaces through the pulmonary structure, and produces the
noise known as crepitation. If the lung contains serum or mucus,
a frothy red fluid will run out when it is cut.

The texture of the lung is very elastic, this elasticity causing the
organ to contract when the thorax is opened, and to expel air that
may be blown into it.

The specific gravity of the lung varies with the conditions of
dilatation and collapse, or of infiltration with fluid. When the
pulmonary substance is free from fluid, and filled with air, it floats
in water ; but when it is quite deprived of air it is slightly heavier
than water, and therefore sinks. The weight of the lung is
influenced greatly by the quantity of foreign material contained in
its texture ; ordinarily it ranges from sixteen to twenty -four ounces,
the right lung being about two ounces heavier than the left. In
the male the lungs are larger, and, together, they are about twelve
ounces heavier than in the female.

Obvious structure of the lung. The substance of the lung
is composed of small polyhedral masses or lobules, which are hollow,
and again subdivided into minute vesicles called the air-cells. The
lobules are visil^le as little polygonal areas, marked by the lines of

ANATOMY OF THE LUNGS. 479

pigment, upon the surface of the lung ; and by inflating a portion
of the organ, the cellular structure may be seen. The several
lobules are united together by connective tissue without fat ; and
each is attached to a terminal branch of the airtube, and receives
oflsets of the pulmonary vessels.

The lung is invested by the pulmonary pleura, except at the Serous
hilum, where the vessels enter. The serous membrane is thin and ^^venng
transparent, and is closely attached to. the lung-substance by means
of a fine layer of subserous areolar tissue, which is continuous with
the interlobular tissue. Both the pleura and the subserous tissue and sub-
are very elastic, so that in the collapsed state the surface of the '
lung is still smooth.

Airangement of the airtube and pulmonary artery entering the lung. Relation of
It has already been seen that in the root of the lung the pulmonary bronchus,
artery lies at first in front of the bronchus ; but before entering the
organ the artery crosses over, and gains the posterior surface of the
airtube. On the left side the artery passes backwards above the on left side,
undivided bronchus ; but on the right side the bronchus gives off and on right,
the branch {epiarterial bronchus) to the upper lobe of the lung before
it is crossed by the arterial trunk, which therefore runs between the
upper and middle divisions of the airtube. From this arrangement
it would appear that the lower half of the left bronchus and the
two lobes of the left lung are represented on the right side by the
continuation of the bronchus below the artery and by the middle
and lower lobes of the lung ; and that the upper lobe of the right
lung with its division of the airtube have no representatives on the
left side.

Bronchial branches in the lung. If the primary divisions of the Airtubes in
bronchi be followed into the lung, they will be found to give off ""^ "
secondary branches ; and these, together with the smaller offsets of
the air-passages, divide for the most part dichotoniously, that is mode of
evenly into two. The branches of the airtube within the lung are '^*"*^ '"^ '
known as the bronchia or bronchial tubes, and differ from the bronchi
in being circular in section. Their structure resembles that of the structure ;
bronchi ; but the pieces of cartilage are irregular in shape and occur
on all sides of the tube, and the muscular tissue is proportionately
greater in amount and completely surrounds the canal. The
ultimate bronchial tubes are about half a line in diameter ; and and ending,
each leads to a group of somewhat funnel-shaped dilatations
{infundihula\ w^hich are beset with air-cells and form -the lobules
of the lung.

Vessels of the lung. Two sets of vessels are furnished to the Vessels are
lung, viz., the pulmonary, which bring blood to the lung to be ^° ^'~
aerated, and then return it to the heart and the smaller bronchial,
which convey the blood destined for the nutrition of the lung.

The pulmonary artery divides like the bronchus, and within the Pulmonary
lung its branches run usually on the posterior surface of the * ^^^'
bronchial tubes, which they accompany to the lobules. The arterial
branches do not anastomose together ; and they end in the capillary
network of the air-cells.

480

DISSECTION OF THE THORAX.

and veins.

Bronchial
arteries,

and veins.

Lympha-
tics,

Pulmonary
nerves.

The pulmonary veins are not so regular in their arrangement as
the arteries. They arise from the network of the air-cells ; and the
branches from adjoining lobules communicate freely together. The
larger branches for the most part lie in front of the airtubes which
they accompany. The pulmonary veins have no valves.

The bronchial arteries are derived directly or indirectly from the
aorta, two for the left lung and one for the right (p. 481), and
enter the lung on the airtube, which they also follow in its ramifi-
cations. They distribute branches to the bronchial lymphatic
glands, to the walls of the larger blood-vessels and bronchial tubes,
and to the interlobular connective tissue. Other small offsets ramify
on the surface of the lung beneath the pleura. On the smallest
bronchial tubes minute branches anastomose with oflfsets of the
pulmonary arteries.

The bronchial veins begin by twigs corresponding with the super-
ficial and deep branches of the artery, and leave the root of the
lung to end in the azygos veins. Many of these veins, however, open
into the pulmonary veins, both within the lung and in the root.

The lymphatics of the lung are superficial and deep ; the latter
accompany both the bronchia and the branches of the pulmonary
vessels. All pass to the bronchial glands at the root of the lung.

The nerves of the lung are derived through the pulmonary
plexuses from the vagus and sympathetic, and follow the branches
of the airtube. They have minute ganglia connected with their
filaments.

PARTS OP THE SPINE AND THE SYMPATHETIC CORD.

Dissection
of thoracic
duct,

of other
objects,

and of sym-
pathetic.

Descending
thoracic
aorta ;

In front of the spinal column are the objects in the interpleural
space of the posterior mediastinum, viz., the aorta, azygos veins,
thoracic duct, and oesophagus ; and beneath the pleura on each side
of the spine is the sympathetic nerve.

Dissection (fig. 174). The thoracic duct should be found first
near the diaphragm by removing the pleura ; there it is about as
large as a crow-quill, and rests against the right side of the aorta.

The areolar tissue and the pleura are to be cleared away from the
different structures before mentioned ; and the azygos veins, one
on the right and two on the left of the aorta, should be dissected.
Next follow the thoracic duct upwards beneath the arch of the
aorta, and along the oesophagus beneath the pleura, till it leaves
the upper aperture of the thorax.

After raising the pleura from the inner surface of the vertebrae
and ribs, the gangliated cord of the sympathetic nerve will be seen
lying over the heads of the ribs. Branches are to be followed out-
wards from the ganglia to the intercostal nerves ; and others inwards
over the bodies of the vertebrae, — the lowest and largest of these
forming the three trunks of the splanchnic nerves.

The DESCENDING THORACIC AORTA is the part of the great systemic
vessel between the termination of the arch and the diaphragm. Its

DESCENDING THORACIC AORTA.

481

extent is from the lower border of the fourth dorsal vertebra, on extent;
the left side to the front of the last dorsal vertebra.

Contained in the posterior mediastinum, the vessel is rather course ;
curved, lying at its upper end on the left, and below on the front
of the spinal column. Beneath it are the vertebrae and the smaller and rela-
azygos veins. In front of the vessel are the root of the left lung
and the pericardium. On its left side it is covered throughout by

SjTnpathetic ganglion
(a part of the chain).
Superior intercostal vein.

Aortic intercostal artery.

Vena azygos major.

Right vagus on the
oesophagus.

Left lower azygos vein.
Left vagus.
Thoracic duct.

Great splanchnic nerve.

Rami to the lesser
splanchnic nerve.

Fig. 174. — Diagram op Structures in the Posterior Mediastinum.

the pleura ; and on its right side are the cesophagus, the thoracic
duct, and the large azygos vein, though near the diaphragm the
gullet is placed over the aorta (fig. 174).

The BRANCHES of the vessels are distributed to the surrounding Branches,
parts, and are named from their destination bronchial, pericardial,
cjesophageal, mediastinal, and intercostal,

a. The bronchial arteries supply the structure of the lungs, and Arteries of
adhere to the posterior part of the bronchial tubes, on which they ^^ ""° '
ramify ; they give some twigs to the bronchial glands and the tion.
obsophagus.

D,A. I I

482

DISSECTION OF THE THORAX.

two left

one right.

Pericardial
branches.

(Esophageal
branches.

Mediastinal
branches.

Intercostal
arteries :

number ;

course to
intercostal
sfjaces ;

right
longer.

The anterior
branch

occupies

intercostal

space

with vein
and nerve.

Offsets.

Anasto-

Posterior
branch
turns to
the back.

There are two arteries for the left lung (suj^erior and inferior),
which arise from the front of the aorta at a short distance from
each other.

The artery of the right lung arises in common with one of tlie
left bronchial arteries (superior), or from the first intercostal artery
of the right side.

h. The 'pericardial branches are some irregular twigs, which are
furnished to the posterior part of the pericardial bag.

c. The cesophageal branches are four or five in number, and ramify
in the gullet, forming anastomoses with one another ; above, they
conmiunicate with branches of the inferior thyroid artery ; and
below, with tw^igs of the coronary artery of the stomach.

d. Small mediastinal branches (posterior) supply the areolar tissue
and the glands in the interpleural sj)ace.

e. The intercostal arteries are nine on each side, and pass to
the same number of lower intercostal spaces. Branches are supplied
to the upper two spaces from the intercostal artery of the subclavian
trunk.

These vessels arise from the posterior part of the aorta, and run
outwards on the bodies of the vertebrae, beneath the cord of the
sympathetic nerve, to the intercostal spaces, where each divides into
an anterior and a posterior branch. In this course the upper arteries
have a somewhat oblique direction ; and as the aorta lies on the
left of the spine, the right vessels are the longer, and run also
beneath the oesophagus, the thoracic duct, and the large azygos
vein. Many twigs are supplied to the bodies of the vertebrae.

In the intercostal space, the anterior branch, the larger of the tw^o,
continues onw^ards between the muscular strata to the front of the
chest, where it ends by anastomosing with an intercostal branch of
the internal mammary artery (p. 441). At first the artery
lies in the middle of the space, beneath the pleura, and resting
on the external intercostal muscle ; but near the angle of the
rib it ascends to the upper boundary. Accompanying the artery
are the intercostal vein and nerve, — the vein being commonly
above, and the nerve below it ; but in the upper spaces the nerve
is, at first, higher than the artery.

Branches are furnished to the intercostal muscles, and to the ribs.
Near the angle of the rib a larger (collateral) branch is given off,
which runs forwards along the lower border of the space, and joins
in front a branch of the internal mammary ; and about the middle
(from front to back) of the intercostal space a superficial twig arises,
to accompany the lateral cutaneous nerve.

The highest artery of the aortic set of intercostals anastomoses
with the superior intercostal branch of the subclavian artery. The
lowest two are continued in front into the abdominal wall, where
they lie between the internal oblique and transversalis muscles, and
anastomose with the epigastric and lumbar arteries.

The posterior branch turns backwards between the vertebra and
the superior costo-transverse ligament, and is distributed in the
back. As it passes the intervertebral foramen it furnishes a small

AZYGOS VEINS. 483

spinal branch to the vertehra and the spinal cord. See vessels

OF THE SPINAL CANAL (p. 549).

The intercostal vein closely resembles the artery in its course and intercostal
branching. Xear the head of the rib it receives a contributing ^^^°'
dorsal branch, and then joins an azygos vein.

Bronchial veins. A vein issues from the root of each lung, and Vein of the
ends on the right side in the large azygos vein, and on the left in ^"°^'
the superior azygos vein of its own side.

The SUPERIOR INTERCOSTAL ARTERY of the Subclavian trunk Superior

descends over the neck of the first rib, external to the cord of
the sympathetic, and supplies a branch to the first intercostal supplies two
space : continuing to the second space, which it supplies in like ^P*^*^^
manner, it ends by anastomosing with the upper aortic intercostal.

Its intercostal offsets divide into anterior and posterior branches,
which are distributed like the intercostal branches of the aorta.

The AZYGOS VEINS are two in number on the left side and one on Tliree azygos
the right, and receive branches corresponding to the oflFsets furnished ^■^"^^•
l)y the descending thoracic aorta.

The right or large azygos (fig. 174, p. 481, and fig. 175, ^, p. 486) Large
begins in the right ascending lumbar vein on the right side of the ri^gift'side,^'^
spine in the abdomen. It enters the thorax through the aortic
opening of the diaphragm, and ascends on the right side of the
aorta and thoracic duct, over the intercostal arteries and the bodies
of the vertebrae. Opposite the fifth rib the vein arches forwards
above the root of the right lung, and enters the superior cava as and joins
this vessel pierces the pericardium. Its valves are few and very ^va?""^
incomplete, and the intraspinal and intercostal veins may be
injected through it.

Branches. In this vein are received : — bmnches

1. Eight lower intercostal veins of the right side. ing»-

2. Right superior intercostal vein bringing blood from the second
and third spaces.

3. Left lower azygos vein, bringing blood from the lower three
or four spaces of the left side.

4. Left upper azygos vein bringing blood from the fourth, fifth,
sixth, and seventh spaces of the left side.

5. Right bronchial vein.

6. Small oesophageal, mediastinal, and vertebral veins.

By means of the right azygos vein the inferior vena cava
communicates with the superior, so that blood can reach the heart
from the lower half of the body if the inferior cava were obstructed.

The left lower azygos vein (fig. 175,"') begins in the abdomen in Left lower
the ascending lumbar vein of the left side of the vertebral column. ^^'8°^
Entering the thorax along the aorta, or through the crus of the begins in
diaphragm, the vein ascends on the left of the aorta as high as the abdomen,
ninth or eighth dorsal vertebra, where it crosses beneath that vessel ends in
and the thoracic duct to end in the right azygos. It receives the azj^^os :
three or four lower intercostal veins of the left side, and some branches,
oesophageal and mediastinal branches.

The left upj^er azygos vein (fig. 175, °) is formed by offsets from Left upper

vein.
112

484

DISSECTION OF THE THOEAX.

Superior
intercostal

ending of
right,

and of left.

Vein from
first space.

CEsophagiis

tbe spaces between the superior intercostal above, and the left
lower azygos below. It usually receives branches from the fourth
to seventh spaces inclusive, and the trunk either joins the lower
azygos of its own side, or crosses the spine to open into the right
vein.

in the
thorax,

through
diaphragm.

Parts

covering it,

beneath it.

and on sides,

Three coats

are in it.

A muscular
coat of

external
longitudinal

The superior intercostal vein is a short trunk which is formed by
the union of the veins from the second, third, and, occasionally,
from the fourth spaces. On the right side it descends to join the
beginning of the arch of the large azygos vein ; but on the left
side (tig. 170, t, p. 466) it is directed forwards across the arcih of
the aorta, and then turns upwards to enter the left innominate vein.

The highest intercostal vein ascends from the tirst intercostal space,
in conq^any with the superior intercostal artery, and joins the lower
end of the vertebral vein.

The CESOPHAGUS or gullet (figs. 174 and 175) is a hollow
muscular tube, which extends from the pharynx to the stomach,
and the thoracic part is now to be examined.

Appearing in the thorax to the left of the middle line, it is
directed beneath the arch of the aorta, and reaches the middle of
the spine about the fifth dorsal vertebra. From that spot it is
continued through the interpleural space on the right of the aorta,
till near the diaphragm, where it takes a position over the aorta, to
gain the oesophageal opening.

As far as the aortic arch the oesophagus lies beneath the trachea,
though it projects to the left of the airtube ; beyond the arch it
is crossed by the left bronchus, and is thence in contact with the
pericardium as far as the diaphragm. At the upper part of the
thorax it rests on the longi colli muscles and the vertebrae; but
below the arch of the aorta it is separated from the spine by the
large azygos vein, the thoracic duct, and the right intercostal arteries,
as well as by the aorta near the diaphragm. Laterally it touches
the left pleura above the arch, and both pleurae below, but the
right much more extensively than the left. Below the bronchus
the pneumo -gastric nerves surround the oesophagus with their
branches ; and above the same spot the thoracic duct is in contact
with it on the left.

Structure. If a piece of the oesophagus be removed and distended
with tow, it will be easy to show a muscular, an areolar, and a
mucous coat from without inwards.

The muscular coat is thick and strong, and consists of two layers
of fibres, of which the external is longitudinal, and the internal
circular in direction, like the muscular tunic of the other parts of
the alimentary tube. In the upper third of the oesophagus the
muscular coat is red, and composed of striped fibres ; but below
this it becomes gradually paler, and the striped fibres give way to
involuntary muscular tissue.

The external layer is formed of parallel longitudinal fibres, which
form a continuous covering, and end Ijelow on the stomach. The
fibres begin in the neck opposite to the cricoid cartilage ; and at
intervals varying from half an inch to an inch and a half, they are

LYMPKATICS AND THORACIC DUCTS. 485

interrupted by small tendons (-^^ to -^^ of an inch long) like the
fibres of the rectus abdominis muscle.

The internal layer of circular fibres is continuous above with the and internal
fibres of the pharynx ; they are more oblique at the middle than abres.^'^
at either end of the oesophagus.

The areolar or submucous layer is situate between the muscular Fibrous
and mucous coats, and attaches the one to the other loosely. ^*y®^-

The mucous coat will be seen on cutting open the tube : it is Mucous
reddish in colour above but pale below, and is very loosely con- ^°**'
nected with the muscular coat, so that it is thrown into longitudinal
folds when the oesophagus is contracted. The surface is studded Papillae and
with minute papillse, which are, however, concealed by the thick, ^^' ^^ "™'
laminated, scaly epithelium.

Some compound glands (oesophageal) are scattered along the tube. Some
and are most numerous at the lower end of the gullet. ^ *" ^'

Lymphatics of the thorax. In the thorax are lymphatic Lymphatics
vessels of the w^all and the viscera, which enter collections of J.^^^®^
glands, and end in one or other of the lymphatic ducts. Besides
these, the large thoracic duct traverses the thorax in its course from
the abdomen to the neck.

Lymphatic glands. Along the course of the internal mammary stemai
artery lies a chain of sternal glands, which receive lymphatics from ^ ^" ^"
the upper part of the abdominal wall, the front of the chest, the
mamma, and the fore part of the diaphragm.

On each side of the spine, near the heads of the ribs, as well as intercostal,
between the intercostal muscles, is placed a group of intercostal
glands for the reception of the lymphatics of the posterior wall of
the thorax.

Three or four aiiterior mediastinal glands lie in the fore part of Anterior
the interpleural space, and receive lymphatics from the upper sur-
face of the liver and the diaphragm.

Numerous bronchial glands are situate at the division of the Bronchial,
trachea, and along the bronchi ; through them the lymphatics of
the lung pass.

Along the side of the aorta and oesophagus is a chain of posterior Posterior
mediastinal glands, which are joined by the lymphatics of the oeso-
phagus, and hinder parts of the pericardium and diaphi-agm.

Along the front and lower border of the arch of the aorta are the Superior
superior mediastinal or cardiac glands, which receive the lymphatics ™^ ^^^ '°* *
of the heart, the pericardium, and the thymus.

The thoracic duct (fig. 174 and fig. 175,^) is the main channel by Thoracic
which the lymph of the lower half of the body, and of the left side
of the upper half of the body, as well as the chyle from the intestines,
is conveyed into the blood. The duct begins in the abdomen in an begins in
enlargement (receptaculum chyli ; p. 371), and ends in the veins of men\nd'
the left side of the neck. It is from fifteen to eighteen inches in ends in
length, and is contained in the thorax, except at its origin and
termination. It has the following course and relations : —

Entering the cavity through the same opening as the aorta, the Relations
duct ascends on the right side of that vessel as high as the arch, thora^x.

486

DISSECTION OF THE THORAX.

It may be
divided ;

is furnished
with vah'es ;

receives
most lym-
phatics.

Right duct

is in the
neck :

receives
lymphatics
of one-
fourth of
body.

Thoracic
cord of
sympathetic

has twelve
ganglia.

Opposite the fourth dorsal vertebra it j^asses beneath the aortic
arch, and is then applied to the left side of the oesophagus, on
which it is conducted to the neck under the left subclavian
artery. At the lower part of the neck it
arches outwards, external to the common
carotid artery and above or over the
subclavian artery, to open into the left
subclavian vein at its junction with the
internal jugular.

In this course the tube is oftentimes
divided in two, which unite again ; or its
divif^ions may even form a plexus. Near
its termination it is frequently branched.
It is provided with valves at intervals,
like a vein : and these are in greatest
number at the upper part.

Branches. In the thorax the duct re-
ceives the lymphatics of the left half of the
cavity, viz., from the sternal and inter-
costal glands ; also the lymphatics of the
left lung, the left side of the heart, and
the trachea and oesophagus.

The RIGHT LYMPHATIC DUCT receives
large branches from the viscera of the
thorax, and is a short trunk in the neck,
about half an inch in length, which
opens into the angle of union of the sub-
clavian and jugular veins of the same side :
its opening is guarded by valves.

Branches. Into this trunk the lym-
pliatics of the right upper limb and right
side of the head and neck pour their
contents. In addition, the lymphatics of
the right side of the chest, right lung and
right half of the heart, and some from the
right lobe of the liver, after passing through
their respective glands, unite into a few
large trunks, which ascend beneath the in-
nominate vein to reach the duct in the neck.
Cord of the sympathetic nerve
(fig. 174, p. 481). The thoracic part of
the gangliated cord of the sympathetic
nerve is covered by the pleura, and is
placed over the heads of the ribs and the
intercostal vessels. The ganglia on it are
usually twelve, one being opposite each
dorsal nerve, but this number is frequently reduced by the fusion
of two adjoining ones. The first ganglion is the largest ; and the
last two are rather anterior to the line of the others, being situate
on the side of the bodies of the corresponding vertebrae.

Fig. 175. — The Thoracic
Duct, and the Azygos
Veins.

1. Thoracic duct.

2. Ending of the duct
in the left subclavian vein.

3. Large azygos vein.

4. Left lower azygos
vein.

5. Left upper azygos
vein.

6. Vena cava superior.

7. Left internal jugular
vein, cut through.

SYMPATHETIC NERVE.

487

Each ganglion furnislies external branches to communicate with
the spinal nerves, and internal for the supply of the viscera.

External or connecting branches (fig. 176), Two ofi'sets pass out-
wards from each ganglion to join a spinal nerve (intercostal). In the
branches of communica-
tion both spinal and sym-
pathetic nerve-fibres are
combined ; but one {vjhite
ramus commimicans) (h)
consists almost entirely of
spinal, and the other {grey
ramus communicans) (i)
mainly of sympathetic
fibres.

The internal or visceral
bi-anches differ in size and
distribution, according as
they are derived from the
upper or lower ganglia.

The offsets of the upper
Jive ganglia are very small,
and are distributed to the
aorta, and to the vertebrae
with the ligaments. From
the third and fourth
ganglia also, offsets are
sent to the posterior
pulmonary plexus.

The branches of the Imcer
seven ganglia are larger and
much whiter than the
others, and are united to
form visceral or splanchnic
nerves of the abdomen :
these are three in number
(large, small, and smallest)
and pierce the diaphragm
to end in the solar and
renal plexuses.

The great splanchnic
nerve is a large white
cord, which receives roots

apparently from only four or five ganglia (sixth to the tenth), but
its fibres may be traced upwards on the knotted cord as high as
the third ganglion. Descending on the bodies of the vertebrae, it
pierces the fibres of the crus of the diaphragm, and ends in the
semilunar ganglion of the abdomen. At the lower part of the
thorax the nerve may present a ganglion.

The small splanchnic nerve begins in the tenth and eleventh
ganglia, or in the intervening cord. It is transmitted inferiorly

Branches :

to join
spinal
nerves ;

to supply
viscera.

OflFsets of
upper five
ganglia are
small ;

Fig. 176. — Scheme to Illustrate the con-
nection BETWEEN THE SPINAL AND SYM-
PATHETIC Nerves (Todd and Bowman).

a. Posterior root of a spinal nerve, with a
ganglion, c.

b. Anterior root.

d. Posterior primaiy branch.

e. Anterior primary bianch of the spinal
nerve.

/. Knotted cord of the sympathetic.

g. Granglia on the cord.

h. White offset from the spinal to the
sympathetic nerve.

i. Grey offset from the sympathetic to the
spinal nerve.

of lower
seven, large,
and form

great
splanchnic

to semilunar
ganglion ;

small
splanchnic
to cctliac
plexus ;

488

DISSECTION OF THE THORAX.

smallest
splanchnic
to renal
plexus.

through the crus of the diaphragm, and enters the part of the solar
plexus by the side of the coeliac artery.

The smallest splanchnic nerve sjJiings from the last ganglion, and
accompanies the other nerves through the diaphragm ; in the
abdomen it ends in the renal plexus. This nerve may be absent,
and its place is then taken by an offset of the preceding.

PARIETES OF THE THORAX.

Soft parts
bounding
the thorax.

Subcosta s ;
position ;

attach-
ments ;

irregulari-
ties ;

and use.

Intercostal
muscles.

Inner layer
reaches
angle of
the rib ;

relations.

Outer layer

extends
back to
tuberosity
of the rib.

Trace
nerves.

Eleven

intercostal

nerves.

Upper and
lower ones
differ.

Last dorsal
nerve.

Between the ribs are lodged the two layers of intercostal muscles,
with the intervening nerves and arteries ; and inside the ribs is a
thin fleshy layer at the back, — the subcostal muscles. The base
of the thorax is formed by the diaphragm.

The SUBCOSTAL MUSCLES are small slips of fleshy fibres, which are
situate on the inner surface of the ribs, where the internal inter-
costals cease. Apparently part of the inner intercostals, they arise
from the inner surface of one rib, and are attached to the like
surface of the rib next succeeding.

They are uncertain in number, but there may be ten : they are
smaller above than below, and the upper and lower may pass over
more than one sj)ace.

Action, The subcostals draw together, and depress the ribs, thus
acting as expiratory muscles.

Intercostal muscles. The anterior part of these muscles has
been described (p. 438) ; and the posterior part may now be examined
from the inner side.

The inner muscle begins at the sternum, and reaches back to the
angles of the ribs, or somewhat farther in the upper sjDaces. Where
the fibres cease, a thin fascia {posterior intercostal aponeurosis) is
continued inwards over the outer muscle. The inner surface is
lined by the pleura, and the opposite surface is in contact with the
intercostal nerve and vessels.

External muscle. When the fascia and the subcostal muscles
have been removed, the external intercostal will be seen between
the posterior border of the internal muscle and the spine. Its
fibres cross those of the inner intercostal layer. While this muscle
extends backwards to the tuberosity of the rib, it is generally
absent, as already described, in front, between the rib-cartilages.

Dissection. In a few spaces the internal intercostal muscle
may be cut through, and the intercostal nerve and artery traced
outwards.

The INTERCOSTAL NERVES, eleven in number, are anterior primary
branches of dorsal nerves ; and they pass from the intervertebral
foramina into the intercostal spaces without forming a plexus.
Near the head of the rib each nerve is joined to the sympathetic
by the two communicating filaments just mentioned. The upper
six are confined to the wall of the thorax ; but the lower five are
prolonged into the abdominal wall, where the ribs cease in front.

The anterior branch of the twelfth dorsal nerve lies below the
last rib, and is seen in the dissection of the abdomen.

INTERCOSTAL NERVES. 489

Upper six nerves. At first the nerves lie between the pleura and Course of
the external intercostal muscle with an artery and vein ; hut they ^^^^ ^^^'
soon enter between the intercostal muscles, and extend forwards to
the side of the sternum (p. 439). In their course they supply
branches to the muscles of the thoracic wall, as well as to the and
levatores costarmn and serrati muscles of the back, and cutaneous
offsets to the surface, which are described in the dissection of
the upper limb (p. 13).

There are some deviations in the first and second nerves from the Exceptions
arrangement above specified. ^ ^ ^^'

The first nerve ascends in front of the neck of the first rib, First nerve
and enters the brachial plexus. Before it leaves the chest it in brachial
supplies to the first intercostal space a branch, which furnishes plexus,
muscidar offsets, and becomes cutaneous by the side of the sternum.
There is not any lateral cutaneous offset from this branch, except
when the second nerve is not as large as usual.

The second nerve may extend a considerable way on the wall of Second

the chest before entering between the intercostal muscles ; and it

frequently sends upwards a branch to join the first nerve. It is

remarkable in having a very large lateral cutaneous branch, which

we have seen described in the upper limb as the intercosto-humeral

nerve. In front it ends like the others.

The lower live nerves resemble the foregoing in their course and Lower five
ii-i- 1 ^- •••! nerves,

branches m the intercostal spaces : their termination m the

abdominal wall is described on p. 274.

Upper surface of the diaphragm. The centre of the muscle Uppersur-
is tendinous, and the circumference is fleshy. In contact with the diaphragm,
upper surface are the lung with the pleura on each side, and the
heart and pericardium in the middle : the phrenic vessels and Parts touch-
nerves pierce this surface, external to the pericardium. In the ^"°"
diaphragm are the following apertures ; — one for the cesophagus Apertures
and the pneumo-gastric nerves, a second for the vena cava, a third
for the aorta with the thoracic duct and the large azygos vein, and
a cleft on each side for the splanchnic nerves. Beneath it the
sympathetic passes into the abdomen.

Section III.

LIGAMENTS OF THE TRUNK.

The ligaments of the vertebrae, ribs, and sternum ai-e now to be Articula-
examined. rib?*"^*^^

Articulations of the ribs. Each rib is united to the spinal
column at the one end, and to the costal cartilage at the other.
Between it and the spine there are two synovial joints, and two
sets of ligaments, viz., one between the head of the rib and the
bodies of the vertebrse, and a second passing from the neck and
tuberosity to the transverse processes of the vertebi-se.

490

DISSECTION OF THE THORAX.

and costal
cartilages.

To see the
costo-verte-
bral liga-

and chondro-
sternal.

Ligaments
of head of
rib are

anterior or
stellate

and interar-
ticular,

with syno-
vial sacs.

Costo-
transverse
ligaments :

The costal cartilages are connected to the sternum and to one
another by s3'novial joints and ligaments.

Dissection. For the purpose of examining the ligaments between
the riljs and the vertebrae, take the piece of the spinal column with
the third, fourth, fifth, and sixth ribs attached to it. After
removing the intercostal and other muscles, and the loose tissue
from the surface of the bones, the student will be able to define, as
below, the ligaments passing from the head and neck of the rib to

the bodies and transverse processes
of the vertebrae.

The ligaments attaching the costal
cartilages to the sternum are to be
dissected on the part of the thorax
which was removed in opening the
cavity.

Ligaments of the head of the
RIB. Where the head of the rib is
received into a hollow in the bodies
of two contiguous vertebrae, there
are two ligaments to the articula-
tion — anterior costo-central, and
interarticular, with two synovial sacs.
The anterior costo-central or stellate
ligament (fig. 177,^) is composed
of radiating fibres, which pass from
the head of the rib to the two
vertebral bodies forming the arti-
cular cavity, and to the disc
between them. Where the rib is
in contact only with one vertebra,

-Ligaments op thkRibs

Fia. 177

AND Vertebkj!; (Bourgeky).

1. Anterior ligament of the
bodies of the vertebrae.

2. Short lateral fibres uniting
the bodies.

3. Stellate ligament.

4. Superior costo - transverse
ligament.

5. Interspinous ligament.

i.e., in the first, eleventh and

twelfth, a few fibres ascend to the
vertebra immediately above.

The interarticular ligament will be
seen w^hen the stellate is divided.
It is a very short thin band, which
is attached on one side to the ridge
separating the two articular surfaces
on the head of the rib, and on the other to the intervertebral disc.
In the joints of the first, eleventh, and twelfth ribs, where the
head is not in contact with, the intervertebral substance, it is
absent.

Synovial sacs. There are usually two synovial cavities in the
costo-central articulation, one on each side of the interarticular liga-
ment; but in the three joints before mentioned (1st, 11th, 12th)
there is but one. The special features of these joints should be
verified at this time.

Ligaments of the neck and tuberosity. Three ligaments
pass from the neck and tuberosity of the rib to the transverse
processes of the two vertebrae with which the head is connected ;

ARTICULATIONS OF THE RIBS. 491

and the tuberosity forms a synovial joint with the transverse process
of the lower vertebra.

The superior costo-transverse ligament (fig. 177, ^) is larger and superior or
longer than the others. It ascends from the upper edge of the neck ^•'^^^'^^"'g'
of the rib to the transverse process of the vertebra above : it is
wanting to the first rib. Between this ligament and the vertebra
the posterior branches of the intercostal vessels and nerves pass ; and
externally it is continued into the posterior intercostal aponeurosis.

The postei-ior cosfo-transverse ligament (fig. 184, 3, p, 497) is a short posterior,
l)and of fibres between the rough part of the tuberosity of the rib
and the tip of the transverse process with which the latter articulates.

The middle or interosseous costo-transverse ligament is placed and middle ;
between the neck of the rib and the transverse process which the
tuberosity touches. It will be best seen by sawing horizontally
through the rib and the transverse process. Its fibres are collected
into separate bundles, with fatty tissue between them.

The synovial cavity of the costo-transverse articulation will be synovial
opened by dividing the posterior ligament. ^^•

There is no joint between the last two ribs and their transverse Differences
processes ; and the posterior and middle costo-transverse ligaments and^t\\4?f^
are united in one band. ribs.

Movements of the ribs. The ribs undergo a movement of rotation The ribs
around an axis which passes through the costo-central articulation around an
in a direction corresponding very nearly to that of the neck of the axis,
bone. By this rotation the fore part of the rib is carried upwards
and outwards in inspiration, and downwards and inwards in
expiration. The degree of outward movement is necessarily pro- which is
portionate to the obliquity of the axis, and is therefore greater in ^"Jq^e ^^^^
the case of the lower ribs than the upper, since the backward
inclination of the transverse process of the dorsal vertebrae, and of
the necks of the ribs, increases from above dow^nwards. The lower The lower
ribs, while being elevated, also move somewhat backwards, their °°®^ ^|^° ,

' p p move back-

tuberosities gliding over the sloped facets of the transverse processes ; wards and

and in the eleventh and twelfth ribs the upward and downward °^^^^' ^^
movements are but slight, while the forward and backward move-
ments are relatively free, owing to the absence of the costo-transverse
articulation.

Costal cartilage with the rib. The end of the rib is hollowed Rib and
to receive the costal cartilage, and the two are directly united. The cartilage,
periosteum of the rib is continued into the perichondrium of the
cartilage.

Choxdro-sternal articulations will now be examined in the costai car-
portion of sternum that had previously been put aside, and in what ^jj^°^® ^^'^^
remains on the body. The cartilages of the true ribs, except the
first, are articulated to the sternum by synovial joints. The
extremity of each cartilage is received into a depression on the side
of the sternum, and is fixed by a surrounding capsule. In front
and behind the capsule is thickened by radiating fibres, which are
described as anterior and posterior ligaments.

In the joint of the second cartilage there is an interariicular Second car-
tilage has a
double joint.

492

DISSECTION OF THE THORAX.

Costo-

xiphoid

ligament.

First carti-
lage.

Cartilages
with one
another.

Motion of
cartilages.

Two sets of
ligaments
unite the
vertebrie.

How to see
tlie several
ligaments.

ligament like that to the head of the rib which joins the cartilage
between the pieces of the sternum ; and the synovial sac is double.
Similar bands are sometimes present in one or two of the
succeeding joints.

A special band of fibres passes from the cartilage of the seventh
rib to the ensiform process, and is named costo-xiphoid ligament.

The cartilage of the first rib adheres directly to the sternum,
without forming any joint.

Interchondral articulations. The cartilages of the ribs
from the sixth to the ninth articulate together by means of broad
processes on their adjacent edges, which are connected by synovial
joints. Each joint is surrounded by a short capsule, and is sup-
ported in front by strong fibres of
the anterior intercostal aponeurosis.
The ends of the eighth, ninthj and
tenth cartilages are united each to
the cartilage above by bands of
fibrous tissue.

Movements. There is only a
limited degree of movement in
the chondro - sternal and inter-
chondral articulations, the carti-
lages being elevated with the ribs
in inspiration, and sinking in
expiration.

Articulation of the ster-
num. The manubrium and body
of the sternum are united by a
piece of cartilage, with anterior
and i^osterior longitudinal fibres.
In some cases there is a cavity
resulting from the absorption of
the central portion of the carti-
lage. There is no appreciable
movement between the pieces of the sternum, but the articulation
aids in giving elasticity to the front of the chest.

Articulations of the vertebrae. The vertebrae are united
together by two sets of ligaments, — one for the bodies, and the other
for the arches and processes.

Along the spinal column the ligaments have a general resem-
blance, and one description will sufiice, except for those between
the first two vertebrae and the head and those of the pelvis, which
are described in the head and neck and abdomen respectively.

Dissection. After the articulations of the ribs have been
examined, the same piece of the spinal column will serve for the
preparation of the ligaments of the bodies of the vertebrae. The
anterior ligament of the bodies will be defined with very little
trouble, by removing the areolar tissue.

The spinal canal is assumed to have been opened in the examina-
tion of the spinal cord, and the posterior iigauient of the bodies of

Fig. 178.

a. Anterior comiuon ligament of
the bodies of the vertebrae.

b. Lateral short fibres.

LIGAMENTS OF VERTEBRA.

•J 1)3

the vertebrae is laid bare ; but if the canal should not be open,
for any reason, the neural arches of the vertebra? are to be removed
by sawing through the pedicles.

The remaining ligaments between the neural arches, spines, and
articular processes of the bones may be dissected on the piece taken
away in opening the spinal canal.

Ligaments of the bodies. The bodies of the vertebrae are
united by an anterior and a posterior common ligament with an
intervening piece of fibro-cartilage.

The anterior common liganunt (fig. 178, a) reaches from the axis
to the sacrum. It is narrow above and wide below ; and it also
increases in thickness from above downwards. Its fibres are
longitudinal ; and by detaching parts of the ligament, the super-
ficial ones will be seen to extend over three or four vertebrae, while

Tlie bodies
are united
by:-

Anterior
common
ligament :

form and
thickness ;

extent of
fibres ;

Fig. 179 a.

Fig. 1

Two Views of the Posterior Common Ligament, c, to show the

DIFFERENCE IN SHAPE, A, IN THE NeCK, AND B, IN THE LoiNS.

the deepest pass from one bone to the next. More of the fibres are and mode ot
attached to the intervertebral discs than to the bones ; and few or ^ ^*^
none are fixed to the centre of the bodies. The ligament bridges
over the transverse hollows on the vertebral bodies, and renders the
front of the column smooth and even.

On e^ch side, over the part uncovered by the anterior common Short lateral
ligament, the bodies of the vertebrae are united by a thin layer of ^^'■^^•
short fibres (fig. 178, 6).

The 'posterior common ligament (fig. 179) is contained in the Posterior
spinal canal, lying on the back of the vertebral bodies from ligament:
the axis to the sacrum. It is much thinner than the anterior,
and, unlike that, is broad above and narrow below. It is form;
wider opposite the intervertebral disc than on the bodies, so that
the margins are dentate. In the neck (a) it covers nearly the whole
breadth of the bodies ; but in the dorsal and lumbar regions (b) it
is a narrow band, which sends off a pointed process on each side to
be attached to the intervertebral disc and the upper margin of the

494

DISSECTION OF THE THOKAX.

relations.

To see the
inter-
vertebral
substance.

Inter-
vertebral
discs :

form and

connec-
tions ;

structure

pedicle. The hinder surface of the ligament is in contact with the
dura mater ; and between the band and the centre of the bodies are
intervals where large veins issue from the bones. The fibres are

arranged as in the anterior liga-
ment ; and they are more closely
united with the intervertebral sub-
stance than with the l)one.

Dissection. To see the inter-
vertebral discs, the anterior and
posterior common ligaments must
be taken away ; and to show their
structure, one disc should be cut
through horizontally (fig. 182),
while another is to be divided
vertically by sawing through the

Fig. 180. — Intervertebral Sub-
stance IN THE Lumbar Region
WITH ITS Lamina Displayed.

a. Superficial, and h, deeper
layer, the fibres in the two taking
ditferent directions.

outer part
fibrous
laminae ;

bodies of two vertebrse (fig. 181).
The intervertebral substances or
discs (fig. 180) are placed between
the bodies of the vertebrae, with
the exception of the atlas and axis.
Each disc is a flattened or slightly
biconvex plate (fig. 181), which

is firmly united to the adjacent surfaces of two bodies ; and its form

and size are determined by the bones between which it lies. It is

connected in front and

behind with the an-
terior and posterior

common ligaments ; and

on the sides, in the

dorsal region, with the

stellate and interarticu-

lar ligaments of the

ribs.

In the sections that

have been made the

intervertebral substance

is seen to consist of

two different parts, —

an external, firm and

laminar, and an in-
ternal, soft and pnlpy

(fig. 181).
of The outer laminar

part (fig. 182, a) forms

more than half of the

disc. The laminae are

disposed concentrically, but do not form complete rings ; and they

are attached by their edges to the bodies of the vertebrae (fig. 181, a).

They are composed for the most part of white fibro- cartilage ; but

the superficial ones consist of fibrous tissue. The fibres are parallel

181. — Vertical Section op the Inter-
vertebral Substance.

a. Peripheral laminar part.
h. Central pulpy part.

THE INTERVERTEBRAL DISCS.

495

in each lamina, and run obliquely between two vertebrae ; but the
direction is reversed in alternate layers (fig. 180). This arrange-
ment is best seen in the thicker discs between the lumbar
vertebrae ; and it may be demonstrated by dissecting layer after
layer.

The central jnilpy portion of the disc (fig. 182, h) is very soft,
and, being tightly confined by the surrounding laminae, it projects
when two vertebrae and the interposed mass are sawn through.
Placed nearer the back than the front of the disc, it is more marked
in the loins and neck than in the dorsal region. It has a yellowish
colour, and is deficient in the stratiform arrangement so conspicuous
in the circumferential j^art.

The surfaces of the vertebrae in contact with the disc have a
cartilaginous covering, which may be seen by cutting the inter-
vertebral substance from the bone.
Over the centre of the osseous
surface it forms a continuous layer,
but it is wanting towards the
circumference.

The discs are thicker between
the lumbar and cervical, than
between the upper and middle
dorsal vertebrae ; and in the loins
and neck, where the spinal
column is convex forwards, they
are deepest at the anterior
edge, being wedge-shaped. The
thickest piece of all, and the
nn)St wedge-shaped, is between
the fifth lumbar vertebra and the
sacrum. The total thickness of
the discs amounts to about a
fourth of the length of the moveable part of the spinal column.

Use. The intervertebral discs form the chief bond of union
between the several bones of the column ; and mainly by reason of
their strength, displacement of the vertebrae is a rare occurrence.

In the movements of the spine the vertebrae revolve around the
central pulpy portion of the disc ; and the extent of the move-
ment between two segments of the column is limited by the
circumferential laminar portion of the discs.

Through their wedge-shaped form the discs are chiefly instru-
mental in giving rise to the convexity of the spine in the loins and
neck ; and by their elasticity they moderate the effect of jars or
shocks transmitted thraugh the column.

Ligaments of the neural arches and processes. The articular
processes of the vertebrae are connected by synovial joints with
surrounding capsules ; the neural arches are united by yellow
ligaments ; the spinous processes have one band along their tips and
others in the intervals between them ; and some of the transverse
processes are joined by fibrous bands.

inner part
of pulpy
substance,

situation

where

largest.

Cartilage
covering
bones.

Thickness

Fig, 182. — Horizontal Section of
AN Intervertebral Disc.

a. Laminar external part.

b. Pulpy central substance.

They bind
bones firmly
together,

but permit
movement :

render
column
convex.

Several
ligaments of
the arch and
processes.

496

DISSECTION OF THE THORAX.

Articular
have capsule
and synovial

Motion in
the joints.

Yellow
ligaments of
the laminae :

extent ;

attach-
ments :

thickness.

Ligaments
of spines :

supraspi-
nous :

and inter-
spinous.

Inter-
transverse
ligaments.

Joints of articular processes. Between the articulating processes
there is a moveable joint, in which the bones are covered with
cartilage, and are surrounded by a capsular ligament, enclosing a
synovial membrane. The capsules are loosest in the cervical, and
strongest in the lumbar region.

Movement. In these gliding joints the articular processes of the
vertebrae move to a limited extent over one another, the direction
of the motion being determined by the form and inclination of their
surfaces. The kinds of movement permitted in any portion of the
column are thus dependent upon the characters of the joints between
the articular processes. The movements are freest in the cervical

region, and least extensive between
the upper dorsal vertebrae. By their
overlapping, the articular processes
also help in giving security to the
spine ; and in dislocation of the
vertebrae they are generallv broken
off.

Ligaments of the arches. The liga-
menta subflava (fig. 183) are small
rhomboidal sheets of yellow elastic
tissue, which close the intervals
between the neural arches at the
back of the spinal canal from the
axis to the sacrum. In each interval
there are two ligaments, a right and
a left, which meet in the middle line,
and extend from the root of the
spine to the articular processes.
They are attached above to the
anterior or deep surface of the
laminae of one vertebra, and below
to the upper border and posterior
surface of the laminae of the next.
They are thin in the neck, and strongest in the loins.

Ligaments of the spines. Along the tips of the spinous processes
of the dorsal and luml)ar vertebrae is a longitudinal band of fibres
(fig. 184, 1) — the supraspinous ligament. It is thickest in the
lumbar region and consists of superficial fibres which pass over
three or more spines, and deep fibres which unite adjoining bones.
Many of the back muscles arise from it on each side.

In the same regions, there are also membranous interspinous
ligaments (fig. 177, ^) reaching from the root to the tip of the
spinous processes. They are thicker and broader in the lumlmr
than in the dorsal part of the column.

In the neck the place of the supraspinous and interspinous
ligaments is taken by the ligamentum nuchae (p. 6).

Ligaments of the transverse processes. In the loins the inter-
transverse ligaments are thin membranous bands in the interA^als
between the processes. In the dorsal region there are rounded

Fig. 183. — An Inner View op
THE Neural Arches of the
Vertebrae, with their Inter-
posed Ligaments (Bodrgery).

1 and 2. Ligamenta subflava.

MOVEMENTS OF THE SPINE.

497

fibrous bundles (fig. 184, ■*) passing between the extremities of the
transverse processes of the middle vertebrae, and representing the
intertransverse muscles of the lower spaces. In the neck they are
absent.

Ligaments of Special Vertebrae. The description of the Ligaments
ligaments of the first two cervical, and of the sacral and coccygeal ^grtebra^
vertebrae, will V)e found with the dissection of the neck and of the
pelvis.

Movements of Spinal Column. The spinal column can be Kinds of
bent forwards, 1 tack wards, and to each side ; and it can be rotated. ™otio°-

In flexion, the ver- Flexion :

tebrae between the
axis and sacrum are
inclined forwards.
The greatest move-
ment takes place be-
tween the lower lum-
bar vertebrae and the

sacrum ; there is an ;,^_^----^^^^-_ ^

intermediate degree ^^il^H^^^^^^^^HMl\ degree;

in the neck ; and the
least is in the upper
half of the dorsal
region, where the ribs
are united to the
sternum.

The bodies of the
bones are brought
nearer together in
front, while they are
separated behind.
The inferior pair of
articular processes of
the second vertebra
glide upwards on the
upper ones of the
third ; the inferior
processes of the third

bone move in like manner on the upper ones of the fourth ; and so
on throughout the moveal)le column.

The ligament in front of the bodies is relaxed, but the posterior
and those uniting the neural arches and processes are tightened.
The fore part of each intervertebral disc is compressed, and the
back is stretched.

In extension, the column is arched backwards. The motion is
most in the neck, and least in the dorsal vertebrae, which are fixed
l)y the true ribs and the sternum, and are impeded in their move-
ment by the overlapping spinous processes.

The posterior parts of the vertebrae are approximated, while
the anterior are separated ; and the inferior articular processes of

movement
of bones ;

Fig. 184. — Ligaments of the Processes op the
Vertebra:, and of the Ribs (Bourgery).

1. Supraspinoiis ligament.

2. Ligamentum subflavum.

3. Posterior costo-trans verse ligament : on the
opposite side the band has been removed and the
joint opened.

4. Intertransverse ligament.

state of
ligaments.

Extension :
where most
and least ;

movement
of bones ;

D.A.

K K

498

DISSECTION OF THE THORAX.

state of
ligaments.

Bending to
side :

movement
of bones ;

state of
ligaments.

Rotation :

movement
of bones ;

where
present.

each glide downwards on the upper ones of the next succeeding
bone.

The condition of the ligaments is the opi30site to that in flexion.
Thus, the intervertebral discs are compressed behind, and stretched
in front ; the spinous and subflaval ligaments are relaxed ; the
anterior common ligament of the bodies is tightened, and the
hinder band is slackened.

Lateral inclination. The spine can be curved to the right or the
left side. Like the last movement, this bend is least in the more
fixed upper dorsal vertebrae, and is greatest in the neck.

On the concave side of the curve, say the right, the bodies are
brought nearer together ; and they are carried away from each other
on the opposite aspect. The right inferior articular surface glides
down, and the left up, in the joints with the vertebra beneath.

On the right side the ligaments will be relaxed and the inter-
vertebral substance compressed ; and on the left those structures
will 1)6 tightened so as to check the movement.

Rotation is the twisting of the bodies of the vertebrae around a
vertical axis through their centres, the fore part being turned to
the right or left, while the lower articular processes glide in the
opposite direction over the upper ones of the next bone below. The
movement will obviously be checked by the tightening of one set
of oblique fibres in the intervertebral disc.

A pure rotation of this kind, however, takes place only to a
small extent in the upper dorsal region ; but in the neck a greater
degree of turning movement is permitted in combination with
lateral flexion, owing to the conformation of the articular surfaces.
In the loins the articular surfaces are so disposed that rotation is
impossible.

CHAPTER IX.
DISSECTION OF THE HEAD AND NECK.

Section I.

EXTERNAL PARTS OF THE HEAD.

Directions. In the dissection of the head and neck, the student Parts to be

should learn the parts described in this and the following Section, [^/'J^y"^*

whilst the ])odv is in the lithotomy position during the first three in the
, - J. ^.' "^ ^ ° lithotomy

days ot dissection. • position.

The scalp is properly limited inferiorlv, from behind forwards, by Limits of
the external occipital protuberance, the superior curved line of the '^® ^^^P-
occipital bone and its prolongation along the temporal lx)ne down
to the tip of the mastoid process, by the temporal ridges on the
parietal and frontal bones and by the supra-orbital margin ; but the
dissection in this section extends downwards to the upper border
of the zygoma.

Characteristics of the part. The skin of the scalp is firmly con- Totigh sub-
nected to the subjacent muscular and aponeurotic structures, and tissue,
instead of the intermediate tissues consisting, as they do in most
parts of the body, of a relatively loose, subcutaneous fascia, they are
composed of dense tissue uniting the parts together. In this dense
tissue the superficial nerves and vessels run ; the roots of the hairs
project into it, and contained in its interstices is a certain amount
of yellowish fat. It is an easy thing to reflect the skin, the super-
ficial vessels and nerves and the aponeurotic tissues in a single
layer, especially towards the upper part of the head. In order to Caution,
avoid this the student should be very careful to keep the knife
well directed to the skin, cutting through the hair roots, and as
much as possible he should dissect from below upwards, for the
1 >lood vessels and nerves are larger below and smaller above.

Position . The body having been placed on its back in the lithotomy
position, the head should be raised to a suitable height by blocks
under the neck, and the face turned towards the opposite side — Position,
this latter being done by mutual arrangements betw^een the
dissectors of the two sides.

Dissection. An incision should be made upwards behind the
auricle along the line of its attachment, from the tip of the mastoid
process below to the upper border of the auricle above, and it
should then pass down the anterior attachment as far as the upper
border of the zygoma. From this it should be prolonged forwards

K K 2

500

DISSECTION OF THE HEAD.

Incisions.

Muscles of
the ear.

Dissection
of upper
muscles.

of posterior
muscle.

Attrahens

aureni

muscle.

Attollens

aurem

muscle.

Retrahens
aurem con-
sists of two
or three
bundles.

Use of ear
muscles.

along the upper "border of the zygomatic arch and along the upper
margin of the orbit as far as the root of the nose. A second incision
should imss from the root of the nose, over the skull in the middle
line to the external occipital protuberance behind. The flap of
skin should be reflected upwards from below in front of the pinna
and then be turned downwards behind that part as far as the
superior curved line of the occipital bone.

Extrinsic Muscles of the Ear. Three muscles pass to the
auricle from the side of the head. Two are above it, — one elevat-
ing, the other drawing it forwards ; and the third, a retrahent
muscle, is behind the ear. There are other special or intrinsic
muscles of the cartilage of the ear, which will be afterwards
noticed.

Dissection. If the auricle be drawn downwards by hooks, the
position of the upper muscle will be indicated by a slight prominence
between it and the head. By cleaning the slight ridge thereby
produced, and removing a little areolar tissue, a thin fan-shaped
layer of pale muscular fibres will come into view, the anterior
portion of which is the attrahens, while the posterior is the attollens
aurem muscle (fig. 185).

On drawing forwards the ear, a ridge marks the situation of the
posterior muscle, and the retrahens muscle must be sought beneath
the subcutaneous tissue. It consists of rounded bundles of fibres,
and is stronger and deeper than the others.

The ATTRAHENS AUREM (fig. 185, ^^) is a small fan-shaped muscle
which arises from the fore part of the aponeurosis of the occipito-
frontalis. Its fibres are directed downwards and backwards, and
are inserted into a projection on the front of the rim of the ear.
Beneath it are the superficial temporal vessels and nerves.

The ATTOLLENS AUREM (fig. 185, 1^) has the same form as the
preceding, though its fil^res are longer and better marked. Arising
also from the tendon of the occipito-frontalis, the fibres converge
to their insertion into the inner or cranial surface of the pinna of
the ear — into an eminence corresponding with a fossa (that of the
antihelix) on the opposite aspect.

The RETRAHENS AUREM (fig. 185, 1') cousists of two or three
roundish but separate bundles of fibres, which are stronger than
those of the other muscles. The bundles arise from the root of the
mastoid j)rocess, and pass almost horizontally forwards to be
inserted by tendinous fibres into the lower part of the ear (concha)
on its cranial asj^ect. The auricular branches of the posterior
auricular artery and nerve are in contact with this muscle.

Action. The three preceding muscles will move the outer ear
slightly in the directions indicated by their names ; the anterior
drawing it upwards and forwards, the middle one upwards, and the
posterior backwards.

Dissection. The muscular fibres of the occipitalis behind and
of the frontalis in front are now to be cleaned according to their
direction (fig. 185) and then the superficial vessels and nerves dis-
played in the following manner (fig. 186, p. 505).

SUPERFICIAL VESSELS AND NERVES.

501

Along the eyebrow seek the branches of vessels and nerves Seek nerves
which come from the orbit, viz., the supraorbital vessels and nerve q" the^^^ '
about the middle, and the supratrochlear nerve and frontal vessels forehead,
near the inner angle of the orbit ; they lie at first beneath the

Fig. 185. — Muscles of the Scalp and Ear.

1. Frontalis, and 4. v^ccipitalis (the
aponeurosis passing over the head
between them).

2. Orbicularis palpebrarum.

3. Levator labii superioris alseque

nasi.
5.
6.
7.

Compressor naris.
Levator labii superioris.
Zygomaticus minor (too large).
Zygomaticus major.
Risorius.

10.

Masseter.

11.

Orbicularis oris.

12.

Depressor labii inferioris.

13.

Depressor anguli oris.

14.

Buccinator.

15.

Attollens aurera.

16.

Attrahens aurem.

17.

Retrahens aureiu (only partly

seen).

Levator anguli oris.

on the side
of the head.

muscular fibres of the frontalis, which must be cut through to find
them.

On the side of the head, in front of the ear, the superficial tem-
poral vessels and nerve are to be traced upwards ; and, above the
zygomatic arch, the branches of the facial nerve which join an offset
of the superior maxillary are to be sought.

Behind the ear the posterior auricular vessels and nerve, and behind ear,
below it branches from the great auricular nerve to the tip and back
of the pinna are to be found ; one or more oflFsets of the last should
be followed to its junction with the posterior auricular nerve.

At the back of the head the ramifications of the occipital vessels,
and the large and small occipital nerves should be denuded ; the

at the back
of the head.

IPN.

T...Jo.\^- V^,o\k^v

502

DISSECTION OF THE HEAD.

Occipito-
frontalis.

Occipital
part: origin
and ending.

Frontal
part :

how at-
tached.

Aponeu-
rosis :

its attach-
ment.

and rela-
tions.

Prolonga-
tion to ea

Use of an-
terior and

posterior
belly.

Vessels of
the scalp.

former nerve lies by the side of the artery, and the latter about
raid way between this vessel and the ear.

The occiPiTO-FRONTALis MUSCLE (fig. 185, ', ^) covers the greater
part of the vault of the skull, and consists of anterior and posterior
fleshy parts with an intervening aponeurotic tendon.

The posterior part, or the occipitalis (^), arises from the outer half
or more of the upper curved line of the occipital bone, and from
the mastoid portion of the temporal bone. The fibres are about
one inch and a half in length, and ascend to the aponeurosis.

The anterior part, or the frontalis Q), forms a thin layer
which covers about the lower two-thirds of the frontal bone. Its
fibres are paler than those of the occipital part, and spring from
the aponeurosis some distance below the line of the coronal suture.
They descend to the eyebrow and root of the nose, where they
interlace with the fibres of the orbicularis palpebrarum, corrugator
supercilii and pyramidalis nasi muscles (fig. 203, p. 553), and
terminate in the subcutaneous tissue. Some fasciculi are frequently
attached to the nasal bone internally, and to the external angular
process of the frontal bone on the outer side. The right and left
muscular portions meet at the lower part of the forehead.

The tendon of the occipito-frontalis, or the epicranial aponeurosis^
covers the upper part of the cranium, and is continuous across the
middle line with the like structure of the opposite half of the head.
In front, it sends a pointed process downwards for some distance
between the two muscular portions ; and behind, it is prolonged
between the posterior bellies, to be attached to the occipital bone
along the highest curved line. From its lateral margin the upper
auricular muscles arise. Superficial to the aponeurosis are the
vessels and nerves of the scalp and a small quantity of fat, which
is traversed by numerous short fibrous bands uniting it closely
to the skin. Its deep surface is connected to the pericranium only
by a loose areolar tissue devoid of fat, so that the scalp moves
freely over the skull.

By making a transverse incision through the aponeurosis above
the ear and separating it from the pericranium towards the side of
the head, it will be seen to be joined by a thin membrane, which
springs from the skull along the superior temporal line, and
descends, closely united to the deep surface of the attollens aurem
muscle, over the temporal fascia to be attached to the pinna of the
ear.

Action. When the anterior belly contracts it raises the eyebrow,
smoothing the skin at the root of the nose, and wrinkling trans-
versely that of the forehead ; and continuing to contract, it draws
forward the scalp. The posterior belly will move the scalp back-
wards ; and the bellies acting in succession can carry the haiiy
scalp forwards and backwards.

Cutaneous Arteries. The arteries of the scalp (fig. 186)
are furnished Ijy the internal and external carotid trunks, and
anastomose freely over the side of the head. Only two small
branches, the supraorbital and frontal, come from the internal

CUTANEOUS ARTERIES. 503

carotid ; while three, viz., the superficial temporal, the occipital,
and the posterior auricular, are derived from the external.

The SUPRAORBITAL ARTERY leaves the orbit through the notch Supraorbi.
in the margin of the orbit, and is distributed on the forehead, ^^i^'^ery.
Some of its branches are superficial to the frontalis and supply the
skin ; while others lie beneath the muscle, and supply it, the
pericranium, and the bone.

The FRONTAL ARTERY is close to the inner angle of the orbit, Frontal
and is much smaller than the preceding. It ends in branches for ^^^^''y-
the supply of the muscles, integuments, and pericranium.

The SUPERFICIAL TEMPORAL ARTERY (d) is One of the terminal Superficial

branches of the external carotid. After crossing the zygoma ^^"^"'^^
immediately in front of the ear, the vessel divides on the temporal
fascia into anterior and posterior branches.

The anterior brarich runs forward with a serpentine course to anterior an4
the forehead, supplying muscular, cutaneous, and pericranial offsets,
and anastomoses with the supraorbital artery ; this is the branch
that is opened when blood is taken from the temporal artery.

The i^osterior branch is larger than the other, and ascends to the posterior
top of the head, over which it anastomoses with the artery of the '^^o*^^*^^-
opposite side. Its offsets are similar to those of the anterior
division, and communicate behind with the occipital and posterior
auricular arteries.

Occipital artery. The terminal part of this artery, Occipital
appearing between the trapezius and sterno-mastoid muscles, ^^ ^^^'
divides into large and tortuous branches, which spread over the
back of the head. Communications take place with the artery of
the opposite side, with the posterior branch of the temporal, and
with the posterior auricular artery. Some offsets pass deeply to
supply the occipitalis muscle, the pericranium, and the bone.

The POSTERIOR AURICULAR ARTERY (/) appears in front of the Posterior

mastoid process, and divides into two branches. One {mastoid) is artery.*^
directed backwards to supply the occipitalis, and anastomoses with
the occipital artery. The other {auricular) supplies the retrahent
muscle, the back of the pinna, and the superficial structures above
the ear : offsets from it also pierce the pinna to be distributed on
the opposite surface.

The Veins of the exterior of the head generally correspond to the Veins of the
arteries in their course, and communicate freely together, as well as *^*^i*-
with the sinuses in the interior of the skull by means of small
branches named emissary, and with the veins of the diploe of the
cranial bones. The frontal vein is of large size, and descends to the
inner end of the eyebrow, beneath which it is joined by the smaller
supraorbital vein : the resulting vessel is known as the angular vein,
and it forms the commencement of the facial trunk. The temporal
vein descends to the temporo-maxillary trunk ; the posterior auricular
vein to the external jugular ; and the occipital veins join the deep
veins at the back of the neck.

Cutaneous Nerves (fig. 186). The nerves of the scalp are ^"^^rves of
furnished from cutaneous offsets of both cranial and spinal nerves. ^^ ^^ ^"

504

DISSECTION OF THE HEAD.

Supraorbital
nerve :

its two cuta-
neous and

palpebral
branches.

Supratroch-
lear nerve :

palpebral
branch.

Temporal
nerves :

of superior
maxillary ;

of inferior
maxillary,

its auricular
branch ;

and of facial
nerve.

Posterior
auricular ,
nerve has

The half of the head in front of the ear receives branches from the
three trunks of the fifth cranial nerve, and twigs to the muscles
from the facial nerve. The skin of the hinder part of the head is
supplied by spinal nerves (anterior and posterior primary branches) ;
and close behind the ear, there is a muscular offset of the facial or
seventh cranial nerve.

The SUPRAORBITAL NERVE (fig. 186), comes from the first trunk
of the fifth nerve, and escapes from the orbit with its companion
artery. It is placed at first beneath the orbicularis palpebrarum
and frontalis muscles, and here gives offsets to these as well as to
the pericranium. In the orbicularis a communication is established
between this and the facial nerve. Finally the nerve ends in two
cutaneous branches.

The inner of these soon pierces the frontalis, and reaches upwards
as high as the parietal bone. The outer branch is of larger size,
and perforating the muscle higher up, extends over the head as far
as the ear.

As the nerves escapes from the supraorbital notch it furnishes
some jjalfebral filaments to the upper eyelid.

At the inner angle of the orbit is the small supratrochlear
NERVE (fig. 186), from the same trunk. It ascends to the forehead
close to the bone and, piercing the muscular fibres, ends in the
integument. Branches are given from it to the orbicularis and
corrugator supercilii, and some palpebral twigs enter the upper
eyelid.

The SUPERFICAL TEMPORAL NERVES are derived from the second
and third trunks of the fifth nerve, and from the facial nerve.

The TEMPORAL BRANCH OF THE SUPERIOR MAXILLARY NERVE

(second trunk of the fifth) is a slender twig (fig. 186), from the
temporo-malar nerve, which perforates the temporal aponeurosis
about a finger's breadth above the zygomatic arch. When cuta-
neous, the nerve is distributed on the fore part of the temple, and
communicates with the facial nerve, also sometimes with the next.

The AURICULO-TEMPORAL NERVE (fig. 186, accompanying d), a
branch of the inferior maxillary (third trunk of the fifth), makes its
appearance with the temporal artery in front of the ear. As soon as
it emerges from beneath the parotid gland, it divides into two terminal
branches. The posterior is the smaller of the two, and supplies
the integument above the ear. The anterior branch ascends verti-
cally to supply the skin as far as the upper limit of the temporal
fossa. The nerve also furnishes an auricular branch (upper) to the
fore part of the ear above the auditory meatus.

The TEMPORAL BRANCHES OP THE FACIAL NERVE are directed
upwards over the zygomatic arch and the temporal aponeurosis to the
orbicularis palpebrarum, corrugator supercilii and frontalis muscles :
they will be described with the dissection of the facial nerve.

The POSTERIOR AURICULAR NERVE (fig. 186) lies behind the ear
with the artery of the same name. It arises from the facial nerve
close to the stylo-mastoid foramen, and ascends in front of the
mastoid process. Soon after the nerve becomes superficial it

CUTANEOUS NERVES.

505

communicates with the great auricular nerve, and divides into
occipital and auricular branches.

The occipital branch is long and slender, and ends in the posterior occipital

branch,

;cipital artery,

rior auricular
^branch of facial)

it occipital nerve.

Facial nerve,

Small occipital nerve.
Great auricular nerve,

Frontal artery.

Supraorbital artery.

Supratrochlear nerv

Supraorbital nerve.

fratrochlear nerve
Malar branch of tei

poro-nialar.
Tempoi-al branch o;
temporo-uial

Nasal nerve.

Infraorbital
nerve.

Long buccal nervi
Mental nerve.

Fig. 186. — Nerves and Arteries of the Scalp.

A. Platysma muscle.

B. Trapezius muscle.

c. Sterno-mastoid muscle.
D. Masseter muscle.

d. Superficial temporal artery.
/. Posterior auricular artery.
h. Orbital branch of superficial
temporal artery.

14. The superficial cervical nerve.

The auriculo-temporal nerve is shown running up with the superficial
temporal artery (d).

belly of the occipito-frontalis muscle. It lies close to the bone,
enveloped in dense fibrous structure.

The auricular branch ascends to the back of the ear, supplying andauri-
the retrahent muscle and the small muscles on the posterior surface
of the pinna.

506

DISSECTION OF THE HEAD.

Great aiiri-
cular uerve.

Great occlpl'
tal nerve :

junctions.

Small occi-
pital nerve

has an

auricular

branch.

How to see

temporal

fascia.

Temporal
fascia :

attach-
ments,

relations,

and layers.

To see tem-
poral
muscle.

Temporal
muscle :

origin,

The GREAT AURICULAR NERVE, from the anterior divisions of the
second and third cervical nerves in the cervical plexus (fig. 186), is
seen to some extent at the lower part of the ear, but its anatomy-
will be afterwards given with the description of the cervical plexus.

The GREAT OCCIPITAL (fig. 186) is the largest cutaneous nerve
at the back of the head, and lies close to the occipital artery. It
is the internal branch of the posterior primary branch of the
second cervical nerve ; it perforates the muscles of the back of the
neck, and divides on the occiput into numerous large offsets ; these
spread over the posterior part of the head, and terminate in the
integument. As soon as the nerve pierces the trapezius, it is joined
by an offset from the third cervical nerve ; and on the back of the
head it communicates with the small occipital nerve.

The SMALL OCCIPITAL NERVE, from the anterior divisions of the
second and third cervical nerves in the cervical plexus (fig. 186),
lies midway between the ear and the preceding nerve, and is con-
tinued upwards in the integuments higher than the level of the
ear. It communicates with the nerve on each side, viz., the
posterior auricular and the great occipital. Usually this nerve
furnishes an auricular branch to the upper part of the pinna on its
cranial aspect.

Dissection. The upper auricular muscles and the temporal
vessels, together with the epicranial aponeurosis and its lateral
prolongation, will now be removed in order that the attachment
of the temporal fascia on the side of the head may be seen.

The temporal fascia is a white, shining membrane, which is
stronger than the epicranial ajjoneurosis, and gives attachment to
the subjacent temporal muscle. Superiorly it is inserted into the
curved line that limits the temporal fossa on the side of the skull ;
and inferiorly, where it is narrower and thicker, it is fixed to the
zygomatic arch. By its cutaneous surface the fascia is in contact
with the muscles already examined, and with the superficial
temporal vessels and nerves.

An incision in the fascia, a little above the zygoma, will show it
to consist there of two layers, which are fixed to the edges of the
upper border of the zygomatic arch. Between the layers is some
fatty tissue, with a small branch of the superficial temporal artery,
and a slender twig of the orbital branch of the superior maxillary
nerve Avith an accompanying artery.

Dissection. The temporal fascia is now to be detached from the
skull, and to be thrown down to the zygomatic arch, in order that
the origin of the underlying temporal muscle may be examined.
The soft areolar tissue which lies beneath it near the zygoma is to be
taken away. The difference in thickness of the parts of the fascia
will be evident.

The TEMPORAL MUSCLE is laid bare only in part. Wide and
thin above, it becomes narrower and thicker below. It arises
from the temporal fascia, and from the surface of the impres-
sion on the side of the skull, which is named the temporal fossa.
From this origin the fibres descend and converge to a tendon,

INTERNAL PARTS OF THE HEAD. 507

which is inserted iuto the margins and inner surface of the coronoid insertion,
n .^ •, • and

process oi the lower jaw.

On the cutaneous surface is the temporal fascia, with the parts relations,
superficial to that membrane ; and concealed by the muscle are the
deep temporal vessels and nerves which ramify in it. The insertion
of the mustde will be seen, and its action explained, in the dissection
of the pterygoid region.

Section II.

INTERNAL PARTS OF THE HEAD.

Dissection. The skull is now to be opened by the workers on Dissection
both sides of the head acting jointly, but before sawing through skuuT" ^
the bone the dissector should detach the temporal muscle nearly
down to the zygoma ; all the remaining soft parts are to be di\dded
by an incision carried round the skull, about one inch above the
margin of the orl>it at the forehead, and about the same distance
above the protuberance of the occipital bone behind.

The cranium is to be sawn in the same line as the incision Precautions
through the soft parts, but the saw is to cut only through the throughThe
oiiter table of the bone. The student will know when he has ^"e.
reached the diploe by the material on the saw becoming red.
The inner table is then to be broken through with a chisel, in
order that the subjacent membrane of the brain (dura mater) may
not be injured. The skullcap is next to be forcibly detached by
inserting the hooked part of the handle of the chisel between the
cut surfaces of bone in front and pulling the shell of bone off
backwards. The dura mater will then come into view.

The DURA MATER is the most external of the membranes investing Dura mater ;
the brain. It is a strong, iBbrous structure, which serves as an
internal periosteum to the bones, and supports the cerebral mass.
Its outer surface is rough, and presents, now the bone is separated appearance
from it, numerous small fibrous and vascular processes ; but these gurface!^
are most marked along the line of the sutures, where the attach-
ment of the dura mater to the bone is more intimate. Ramifying
on the exposed part of the membrane are branches of the large
meningeal vessels.

Small granular masses. Pacchionian bodies, are also seen close to Pacchionian
the middle line. The number of these bodies is very variable ; t^*^'®^-
they are seldom found before the third year, but generally
after the seventh, and they increase with age. The surface of the
skull is frequently indented by those bodies, especially on the back
part of the parietal bone.

Dissection. For the purpose of seeing the interior of the Cut through
dura mater, di^-ide this membrane with scissors close to the ^^™ mater,
margin of the skull, except in the middle line before and behind,
where the superior longitudinal sinus lies. The cut membrane

508

DISSECTION OF THE HEAD.

Inner
surface

and struc-
ture.

Processes.

Falx
cerebri :

form and
attach-
ments ;

borders :

sinuses in it.

Superior
longitudinal
sinus :

situation
and ending

its interior

veins open-
ing into it.

is then to be raised on the right side towards the top of the
head ; and the veins connecting it with the brain may be broken
through.

The inner surface of the dura mater is free and smooth, being
separated from the arachnoid (the second of the coverings of the
brain) by the cavity known as the subdural space, although the two
membranes are in the natural condition closely applied to one
another. The fibrous tissue of which the dura mater is composed
is so arranged as to give rise to two strata, an external (or periosteal)
which adheres to the bones, and an internal (or meningeal) which
is lined by an epithelium similar to that on serous membrane.^.
At certain spots these layers are slightly separated, and form
thereby the spaces or sinuses for the passage of the venous blood.
Moreover, the innermost layer sends processes between different
parts of the brain, forming the falx. tentorium, &c.

The falx cerebri (fig. 187, p. 512) is the median sickle-shaped
process of the dura mater, which dips in between the hemispheres
of the large brain. Its form and extent will be evident if the right
half of the brain is gently separated from it. Narrow in front,
where it is attached to the crista galli of the ethmoid bone, it
widens behind, and joins a horizontal piece of the dura mater
named the tentorium cerebelli. Its upper border is convex, and
is fixed to the middle line of the skull as far backwards as the
internal occipital protuberance ; and the lower or free border is
concave and turned towards the central portion of the brain (corpus
callosum), with which it is in contact interiorly.

In this fold of the dura mater are contained the following
sinuses : — the superior longitudinal along the convex border, the
inferior longitudinal in the hinder part of the lower edge, and the
straight sinus at the line of junction between it and the tentorium
(fig. 187).

The SUPERIOR LONGITUDINAL SINUS (fig. 187, b) extends from
the ethmoid bone in front to the internal occipital protuberance
behind. Its position in the convex border of the falx will be
made manifest by the escape of blood through numerous small
veins, when pressure is made from before backwards with the
finger along the median part of the dura mater.

Dissection. The sinus is now to be opened by cutting into it
from above along the middle line and by detaching the dura from
the bone down to the internal occipital protuberance behind.

When the sinus is opened it is seen to be narrow in front, and
to widen behind, where it ends in a dilatation termed the torcular
Herophili on one side (more frequently the right) of the internal
occipital protuberance. Its cavity is triangular in form, with the
apex of the space turned to the falx ; and across it are stretched
small tendinous cords — chordce Willisii — near the openings of some
of the cerebral veins. Frequently small Pacchionian bodies project
into the sinus.

The sinus receives small veins from the substance of the skull
and dura mater, and larger ones from the brain ; and the blood

REMOVAL OF THE BRAIN. 509

flows backwards in it. The cerebral veins open chiefly at the
posterior part of the canal, and they lie for some distance against
the wall of the sinns before they j^erforate the dura mater ; their
course is directed from behind forwards, so that the current of the
blood in them is opposed to that in the sinus : this disposition of
the veins may be seen on the left side of the brain, where the parts
are undisturbed.

Directions. Before the rest of the dura mater can be examined, Directions
the brain must be taken from the head. To facilitate its removal, ofVrahi!^*
let the head incline backwards, wliile the shoulders are raised on a
block, so that the brain may be separated somewhat from the base
of the skull. For the division of the cranial nerves a sharp scalpel
will be necessary ; and the nerves are to be cut longer on the one
side than the other.

Removal of the Brain. As a first step cut across the anterior Mode of

part of the falx cerebri, and the dift'erent cerebral veins entering the and^parte^'

longitudinal si uus ; raise and throw backwards the falx, but leave cut in sue-

. cession

it uncut behind. Gently lift up the frontal lobes and the olfactory

bull)s of the large brain. Next cut through the internal carotid Anterior

artery (fig. 189) and the second and third nerves^ which then n^^t^s^^ *"

appear, together with some veins descending from the brain ;

the large second nerve is placed on the inner, and the round third

nerve on the outer side of the artery.

The brain is now to be supported in the left hand, and the
pituitary body to Ije dislodged with the knife from the hollow in
the centre of the sphenoid bone. A strong horizontal process of the next the
dura mater (tentorium cerebelli) then comes into view at the iDack " '
of the cranium. Along its free margin lies the small /o?tr//i nerve,
which is to be cut at this stage of the proceeding. Make an
incision through the tentorium on each side, close to its attachment
to the temporal l)one, without injuring the parts underneath : the
following nerves, which will be then visible, are to Ije divided in
succession. Near the inner margin of the tentorium is the fifth posterior
nerve, consisting of a large and small root ; while nearer the
median plane is the slender sixth nei-ve. Below the fifth and
somewhat external to it, are the seveyith and eighth nerves entering
the internal auditory meatus, the former being anterior and the
smaller of the two. Directly below the foregoing are the ninth,
tenth and eleventh nerves in one line : — of these the upper small
piece is the ninth or the glosso-pharyngeal ; the flat band next
below, the tenth or pneumo-gastric ; and the long round nerve
ascending from the spinal canal, the eleventh or spinal accessory.
The remaining nerve near the median plane is the twelfth, which
consists of two small pieces.

After dividing the nerves, cut through the vertebral arteries as vessels, and
they wind round the medulla oblongata. Lastly, cut across the
spinal cord as low as possible, as well as the roots of the spinal lastly, the
nerves that are attached on each side. Then on placing the first ^^*°* *^° "
two fingers of the right hand in the spinal canal, the short upper
portion of the cord may be raised, and the whole brain may be

510

DISSECTION OF THE HEAD.

How to pre-
serve tlie
brain.

Examina-
tiou of it.

Directions.

Dura mater
in base of
skull :

its prolonga-
tions,

and connec-
tions to
bone.

Tentorium
cerebelli :

taken readily from the skull in the two hands. In doing this
some large veins, passing from the hinder part of the cerebral
hemisphere to the attached margin of the tentorium, will be broken
through, as well as small ones from the portions of the brain in the
posterior fossa of the base of the skull.

Preservation of the brain. After removing some of the mem-
branes from the upper part, and making a few apertures through
them on the under surface so that the liquid may have free access,
the brain may be hardened by immersion in a 5 per cent, solution
of formalin in water. Wrap the brain up in a piece of calico, and
then place it upside down in a suitable vessel, on the bottom of
which some cotton-wool or tow has been spread, and let it be quite
covered with the liquid, and insert a little tow or cotton wool
between the cerebellum and the occipital lobes.

Examination of the brain. At the end of two or three days
the dissectors should examine the other membranes of the brain
and the vessels as described in Section 1 of The Brain. As soon
as the vessels have been learnt, the membranes are to be carefully
removed from the surface of the brain, without detaching the
different cranial nerves at the under surface. The brain may then
remain in the preservative liquid till the dissection of the head and
neck has been completed, but it should be turned over occasionally
to allow the fluid to penetrate its substance, and a little extra
formalin added from time to time as fully directed in the Section
referred to.

Directions. After setting aside the brain, the anatomy of the
dura mater, and the vessels and nerves in the base of the skull
should be proceeded with. For this purpose raise the head to a
convenient height, and fasten the tentorium in its natural position
wdth a few stitches. The dissector should be famished with the
base of a dried skull while studying the following parts.

Dura mater. At the base of the cranium the dura mater is
much more closely united to the bones than it is at the top of the
skull. Here it follows the different inequalities of the osseous
surfaces and sends processes through the several foramina,
which join for the most part the pericranium, and furnish sheaths
to the nerves.

Beginning the examination in front, the membrane will be found
to send a prolongation into the foramen caecum, as well as a series
of tubes through the apertures in the cribriform plate of the
ethmoid bone. Through the sphenoidal fissure it joins the peri-
osteum of the orbit ; and through the optic foramen a sheath is
continued on the optic nerve to the eyeball. In the sella turcica
the dura mater forms a recess which lodges the pituitary body, and
behind the dorsum sellse it adheres closely to the basilar process of
the occipital bone. From the latter part it may be traced into the
spinal canal through the foramen magnum, to the margin of which
it is very firmly united.

The tentorium cerebelli is the process of the dura mater which is
interposed in a somewhat horizontal position between the small

VENOUS SINCSES OF CRANIUM. 511

brain (cerebellum) and the posterior part of the large brain (cere-
hvxun).

Its upper surface is raised along the middle, where it is joined surfaces,
1)Y the falx cerebri, and is sloped laterally for the support of the back
part of the cerebral hemispheres. Its under surface rests on the
small brain, and is joined by the falx cerebelli.

The anterior concave margin is free, except at the ends where it edges,
is fixed by a narrow slip to each anterior clinoid process. The
posterior or convex edge is connected to the following bones: —
the occipital (transverse groove), the posterior inferior angle of the
parietal, the petrous portion of the temporal (upper border), and the
posterior clinoid process of the sphenoid.

Along the centre of the tentorium is the straight sinus ; and in and the
the attached edge are the lateral and superior petrosal sinuses on
each side.

The falx cerebelli has a corresponding position below the ten- Falx
torium to the falx cerebri above that fold. It is much smaller ^"^
than the falx of the cerebrum, and will appear on detaching the
tentorium. Triangular in form, this fold is adherent to the
internal occij^ital crest, and projects between the hemispheres of
the small brain. Its base is directed to the tentorium ; and the cont^ns
apex reaches the foramen magnum, on each side of which it gives ^n^]
a small slip. In it is contained the occipital sinus.

The SINUSES are channels for venous blood between the layers of Sinuses of
the dura mater. They are arranged in two groups, the one com- ^ *
prising the sinuses that converge towards the internal occipital
protuberance, while the other is formed by the cavernous sinuses
on the sides of the body of the sphenoid bone and the canals opening
into these.

A. The superior longitudinal sinus has been described at p. 508. Superior

The INFERIOR LONGITUDINAL SINUS (fig. 187, c) resembles a small *"*^
vein, and is contained in the lower border of the falx cerebri at L^[udhlai°°'
the posterior part. It receives blood from the falx and the
large brain, and ends in the straight sinus (d) at the edge of the
tentorium.

The STRAIGHT SINUS (fig. 187, d) lies along the junction of the straight
falx with the tentorium, extending from the termination of the ^^°"^-
preceding sinus to the internal occipital protuberance, where it is
continued into one of the lateral sinuses, generally the left. Its form
is triangular, like the superior longitudinal. Joining it are the
inferior longitudinal sinus, the veins of Galen (which will be seen to
be cut or torn offshort) from the interior of the cerebral hemispheres,
and some small veins from the upj^er surface of the cerebellum.

The OCCIPITAL SINUS (fig. 187, g) is a small canal in the falx Occipital
cerebelli, which reaches from the torcidar Herophili to the foramen ^'°'^^'
magnum and collects the blood from the lower occipital fossae.
This sinus may be double.

The LATERAL SINUSES, right and left, are the channels by which Lateral
most of the blood passes from the skull. Each extends from the ^*°"^«** •
internal occipital protuberance, along the winding groove on the

512

DISSECTION OF THE HEAD.

difference
on two

sides,

and tribu-
taries.

occipital, parietal and temporal bones, to the jugular foramen,
where it ends in the internal jugular vein. The sinus of the right
side is generally larger than the left, and begins at the torcular
Herophili behind, forming, usually, the continuation of the superior
longitudinal sinus. The left lateral sinus is mainly prolonged
from the ending of the straight sinus, but it is also joined by a
branch from the lower end of the superior longitudinal sinus, which
crosses obliquely in front of the occipital protuberance. In some
cases this arrangement is reversed, so that the torcular Herophili
and the larger lateral sinus are placed on the left side ; and
occasionally the torcular Herophili forms a common place of the
meeting (confluence) of the superior longitudinal, the straight and
the two lateral sinuses.

The lateral sinus is joined by some cerebral and cerebellar veins,

Fig. 187. — Some op the Venous Sinuses of the Skull.

e. Lateral sinus.

a. Torcular Herophili.
h. Superior, c. Inferior longi
tudinal sinus.
d. Straight sinus.

g. Occipital sinus.
/. Superior, and h.
petrosal sinus.

Inferior

Subdivision
of the
jugular
foramen.

and, opposite the upper edge of the petrous portion of the temporal
bone, by the superior petrosal sinus. It communicates with the
occipital veins through the mastoid foramen, and often with the
deep veins of the neck through the jDOsterior condylar foramen.

The jugular foramen is divided into three compartments by
fibrous bands. Through the posterior opening the lateral sinus
passes ; through the anterior the inferior petrosal sinus : and
through the central one the ninth, tenth, and eleventh nerves.

Dissection. The dissectors should first examine the cavernous
sinus on the left side. Cut through the dura mater by the side of
the body of the sphenoid l)one from the anterior to the posterior
clinoid process, and internal to the position of the third nerve ;
behind the clinoid process, let the knife be directed inwards for
about half the width of the basilar part of the occipital bone. By

IV NERVE

OPHTH. NERVE
SUP. MAX. NERVE

CAVERNOUS SINUS. 513

placing tlie handle of the scalpel in the opening thus made, the
extent of the space will be defined. A probe or a blow-pipe will
be required, in order that it may be passed into the different
sinuses joining the cavernous centre, and these should then be
opened up.

B. The CAVERNOUS sinus, which has been so named from the Cavernous
reticulate structure in its interior, is situate on the side of the body ^^°"^
of the sphenoid bone. This space, resulting from the separation of
the two layers of the dura mater, is of an irregular shape, and
extends from the sphenoidal fissure to the tip of the petrous portion
of the temporal bone.

The layer of dura mater bounding the siniLS externally is of has nerves
some thickness, and contains in its substance the third and fourth ^yaii^. ^^
nerves, with the ophthalmic and superior maxillary trunks of the
fifth nerve : these lie in the order given from above downwards.

The cavity of the sinus is larger behind than before, and is contains
traversed by a network of slender fibrous cords. Through the artery and
space winds the trunk of the internal carotid artery surrounded by sixth nerve :
the sympathetic, with the sixth
nerve running forwards on the
outer side of the vessel ; but all p,^ g,
these are bound to the outer wall
of the sinus, and separated from int. car. art.'
the blood in the space by a thin ^i nerve'

lining membrane.

The cavernous sinus receives

4.1 ^ i^^i^^i^^- ,. • f i-v. Fig. 188. — Transverse Section of tributaries

the ophthalmic veins from the ^^^ Cavernous Sinus (after and com-

orbit through the sphenoidal Langer). mumca-

fissure, and some inferior cerebral

veins. It communicates "with its fellow of the opposite side by

the intercavernous sinuses, and with the pterygoid plexus outside

the skull through the foramen ovale and the foramen lacerum.

The blood leaves the chamber by the superior and inferior petrosal

sinuses.

The INTERCAVERNOUS SINUSES are two vessels which pass trans- Intercavem-

versely in the sella turcica betw^een the right and left cavernous ck'cuiar
sinuses, being placed one in front of, and the other behind the sinus,
pituitary body. To the venous ring thus formed around the
pituitary body the name of Circular sinus has been given.

The SUPERIOR PETROSAL SINUS (fig. 187,/) lies in a groove in the Superior
upper edge of the petrous part of the temporal bone, and extends ^^ ^^^^ '
between the cavernous and lateral sinuses. Small veins from the
cerebellum are received into it.

The INFERIOR PETROSAL SINUS (fig. 187, h) IS larger than the inferior
superior, and lies in a groove along the line of junction of the petrosal,
petrous part of the temporal with the basilar process of the
occipital bone ; it is joined by small veins from the cerebellum,
and one from the internal ear. This sinus passes through the
anterior compartment of the jugular foramen, and ends in the
internal jugular vein.

D.A. L L

514

DISSECnOX OF THE HEAD.

Artefiesof
don mater
artz —

Ant«!!rinr

Laigefiram

mtoml

wttTilhry

bnachesi

One from

Nermof

thebueoT
thesknU:

The BASILAR sixiTS or PLEXUS is a Tenons network in the sub-
stance of the dura mater over the hadlar process of the occipital
bone, nniting the inferior petrosal sinns^w

MssnxGEAL ARTERIE& These arteries sopplving the craninm
and the dnra mater come thioogh the base of the sknll ; ther are
named from their sitnation in the three fossae, anterior, middle,
and posterior.

The A5TERIOR MENINGEAL, are small branches oi the anterior
ethmoidal artery, which enters the skoll bj the anterior internal
orbital canaL Its meningeal branches are distributed to the dnra
mater over and near the ethmoid bone.

The MIDDLE MEXIXGEAL ABTKRTES are three in number : two of
them, named large and small, are derived from the internal
maxillary trunk ; and tlie third is an ofl^et of the ascending
pharyngeal artery.

a. The large memimgeal artenf (often amply called the middie
menimgad artenf) from the internal maxillary appears throng^
the foramen spinosnm of the sphenoid houe, and divides into two
principal branches. The larger of these passes to the deep groove
on the anterior inferior angle of the parietal bone, and ends in
ramifications which extend upwards to the top of the head and
forwards over the frontal bone. The posterior branch is dis-
tributed over the hinder part cf the parietal and the uppo- part of
the occipital bones. Two reins accompany this artery.

As soon as the artery comes into the cranial cavity, it furnishes
branches to the dura mater and to the ganglion of the fifth nerre.
One small (^^et^jiefroco^ enters the hiatus FaDopii, and supplies
the surrounding boneu One or two branches pass through the
sphencHdal fissure into the orbit, and anastoinaee with the ophthalmic
arteiy.

b. The small meningeal hnuuk is an oflbet of the large one
outside the skull, and is txanamitted throiigh the foramen ovale to
the membrane lining the middle cranial fossa.

e. Another meningeal hrantk frtHU the ascending pharyngeal
artery comes through the foramen lacerum (haras cxanii). This is
seldom injected, and is not often visible.

The PoarrERioR meixingeal abtkbtks are small twigs of the
ascending pharyngeal which enter the skull by the anterior condylar
and jugular foramina, and supply the dnra mater in that neighbour-
hood ; also a branch oi the vftrtebral artery is distributed over
the lower part of the occipital bone. The branch coming through
the jugnlar foramen is sometimes derived from the occipital artery.

Meimxgeal Nerves. Offsets to the dura mater are derived
from the fifth, tenth and twelfth oanial nerves^ and from the
sympathetic.

Cra9iial Kert]^ (fig. 189, p. 515). As the cranial nerves pass
through their apertures in the base of the skuU they are invested by
processes of the membranes of the brain, which are thus di^Mised :
— those of the dura mater and pia mater are continued into the
aheath of the nerve ; while that of the arachnoid, except in the

NERVES IN BASE OF SKULL.

515

case of the second nerve, terminates as the nerve enters the dura

mater. Some of the nerves in the middle fossa of the skull pierce

the dura mater before they reach the foramina of exit. The nerves

are arranged in twelve pairs, which are enumerated from before

backwards in the order in which they perforate the dura mat«r.

Only part of the intracranial course of each nerve will be seen at this only partly

stage ; the rest will be learnt in the dissection of the base of the brain.

Fig, 189. — Crakial Nerves ix the Base of the Skull. Ox tbe left
SIDE the Dcra Matkr has beex removed from the Middle Fossa
TO show the Nerves in the Wall op the Cavernocs Sinds, thb
Gasserias Gasglioit, akd the three Trunks of the Fifth Nervk.

2, 3, 4, 5, 6. Second to sixth
nerves.

7. Facial and auditory.

8. Glosso-pharyngeal, vagus and
spinal accessory.

9. Hyxwglossal. On the right side
tbe dura mater is untouched.

t Offset to the tentorium from the
ophthalmic nerve.

The FIRST or olfactory nerves are alx)ut twenty small Olfactory
filaments which arise from the olfactory bulb of the brain as fn the nose
it lies in the groove at the side of the crista galli, and descend
to the nose through the foramina in the cribriform plate of the
ethmoid bone.

The SECOXD or optic nerve (fig. 189, 2), diverging to the eyeball Second
from its commissure, enters the orbit through the optic foramen . to the eye,
It is accompanied by the ophthalmic artery.

L L 2

516

DISSECTION OF THE HEAD.

Dissection
of third and
fourth
nerves :

of fifth
nerve.

Third nerve

passes to
orbit.

Fourth
nerve

in the wall
of sinus.

Fifth nerve
has two
roots.

Large root,

Cavum
Meckelii,
and Gasse-
rian gang-
lion on it ;

gives three
branches.

Dissection. The third and fourth nerves, and the ophthalmic
trunk of the fifth nerve, lie in the outer wall of the cavernous
sinus ; and to see them, it will be necessary to trace them through
the dura mater towards the orbit.

Afterwards the student should follow outwards the roots of the
fifth nerve into the middle fossa of the skull, as in fig. 189, taking
away the dura mater from them, and from the surface of the large
Gasserian ganglion which lies on the fore part of the petrous
portion of the temporal bone. From the front of the ganglion
arise two other large trunks beside the ophthalmic, viz., superior
and inferior maxillary, and these should also be traced to their
apertures of exit from the skull. If the dura mater is removed
entirely from the bone near the nerves a better view will be
obtained. Some of the nerves may have been injured by the
previous opening of the left cavernous sinus, and if that be so, the
dissectors should jointly exandne the right side.

The THIRD or oculomotor nerve (fig. 189, '^) is destined for the
muscles of the orbit. It enters the wall of the cavernous sinus
near the anterior clinoid process, and is placed at first above the
other nerves ; but when it is about to enter the orbit through the
sphenoidal fissure, it sinks below the fourth and part of the fifth,
and divides into two branches.

Near the orbit the nerve is joined by one or two delicate filaments
from the cavernous plexus of the sympathetic.

The FOURTH or trochlear nerve (fig. 189, "*) courses forwards to
one muscle in the orbit. It is the smallest of the cranial nerves,
and pierces the dura mater at the free edge of the tentorium, close
behind the posterior clinoid process. In the wall of the sinus it
lies below the third ; but as it is about to pass through the
sphenoidal fissure it rises higher than all the other nerves.

While in the wall of the sinus the fourth nerve is joined by
twigs of the sympathetic.

Fifth or trifacial nerve (fig. 189, ^). This nerve is distributed
to the face and head, and consists of two parts or roots — a large or
sensory, and a small or motor.

The large root of the nerve passes through an aperture in the
dura mater into the middle fossa of the base of the skull, where it
immediately enters the Gasserian ganglion. The hollow wherein the
ganglion is lodged is known as the Cavum Meckelii.

The Gasserian ganglion, placed in a depression close to the apex
of the petrous part of the temporal bone, is flattened, and about
half an inch wide. The upper surface of the ganglion is closely
united to the dura mater, and presents a semilunar elevation,
the convexity of which looks forward. Some filaments from
the plexus of the sympathetic on the carotid artery join its inner
side.

BrancJus. From the front of the ganglion proceed the three
following trunks : — The ophthalmic nerve, the first and highest, is
destined for the orbit and forehead. Next in order is the superior
maxillary nerve, which leaves the skull by the foramen rotundum,

CRANIAL NERVES. 517

and ends in the face below the orbit. And the last, or the inferior
maxillary nerve, passes through the foramen ovale to reach the
lower jaw, the lower part of the face, and the tongue.

The small root of the fifth nerve, lying in the same tube of the Small root,
dura mater as the large one, passes beneath the ganglion without
communicating with it, and joins only one of the three trunks derived
from the ganglion: if the ganglion be raised, this root will be seen
to enter the inferior maxillary nerve.

Those branches of the ganglion which are unconnected with the Difference la
small or motor root, viz., the ophthalmic and superior maxillary, \-^^ rcK^ts.
are solely nerves of sensibility ; but the inferior maxillary, which
is compounded of both roots, is a nerve of sensibility and motion.
It will moreover be subsequently seen that the fibres of the motor
root are almost entirely confined to that part of the inferior maxillary
nerve which supplies the muscles of the lower jaw, and that the
larger branches of the nerve are wholly sensory in function.

The ophthalmic nerve is the only one of the three trunks which Ophthalmic
needs a more special notice in this stage of the dissection. It is orbit ;
continued through the sphenoidal fissure and the orbit to the fore-
head. In form it is a flat band, and is contained in the wall of
the cavernous sinus below the third and fourth nerves. Near the
orbit it divides into three branches, frojitnl, nasal, and lachrymal.

In this situation it is joined by filaments of the cavernous plexus supplies
of the sympathetic, and gives a small recurrmi filament (fig. 189, f) in its course,
to the tentorium cerebelli.

The SIXTH or abducent nerve (fig. 189, ®) enters the orbit Sixth nerve
through the sphenoidal fissure, and supplies one of the orbital ous sinus ;
muscles. It pierces the dura mater l^ehind the body of the
sphenoid bone in the wall of the inferior petrosal sinus, and
crosses the space of the cavernous sinus, to gain the outer wall
with the other nerves.

In the sinus the nerve is placed close against the outer side of joins sym-
the carotid artery ; and it is joined by one or two large branches P**'^®*'^*^'
of the sympathetic nerve surrounding that vessel.

The SEVENTH or facial and the eighth or auditory nerves Seventh and

(fig. 189, 7) pass together into the internal auditory meatus, the ^g^l^.^g j^^^^.^
facial being the smaller and higher of the two. At the bottom of skull to-
the meatus they separate ; the facial nerve courses through the
aqueduct of Fallopius to the face, and the auditory nerve is
distributed to the internal ear.

The NINTH or GLOSSO-PHARYNGEAL, the tenth, PNEUMO-GASTRIC Ninth,

or VAGCS, and the eleventh or spinal accessory nerves (fig. 189, ^) gig\*^ufi**^
pass through the middle compartment of the jugular foramen, nerves pass
The glosso-pharyngeal is external to the other two, and has a jugui'^r
distinct opening in the dura mater. The spinal accessory nerve foramen,
ascends through the foramen magnum and, together with the
vagus, enters an aperture in the dura mater close to the occipital
bone.

The twelfth or hypoglossal nerve (fig. 189, ^) is the motor Twelfth
nerve of the tongue, and consists of two small pieces, which pierce "®'"^^-

518

DISSECTION OF THE HEAD.

Disaection
of carotid ;

of sym-
pathetic
plexuses,

cavernous
and carotid.

Internal

carotid

artery

winds
through
cavernous
sinus.

Branches.

Sympathetic
forms

carotid
plexus.

cavernous
plexus,

union with

cranial

nerves.

Distribu-
tion.

Two super-
ficial petro-
sal nerves.

the dura mater separately opposite the anterior condylar foramen ;
these unite at the outer part of that aperture.

Dissection. The dissector should now turn to the examina-
tion of the trunk of the carotid artery as it winds through the
cavernous sinus.

An attempt should be made to find two small plexuses of the
sympathetic on the carotid artery, though in a well-injected body
this dissection is scarcely possible.

One of these (cavernous) is near the root of the anterior clinoid
process ; and to bring it into view it will be necessary to cut off
that piece of bone, and to dissect out with care the third, fourth,
fifth, and sixth nerves, looking for filaments between them and
the plexus. Another plexus (carotid), joining the fifth and sixth
nerves, surrounds the artery as it enters the sinus.

The INTERNAL CxiROTiD ARTERY appears in the cranium at the
apex of the petrous part of the temporal bone. In this part of its
course the vessel lies between the layers of the dura mater bound-
ing the cavernous sinus along the side of the body of the sphenoid
bone, and makes two bends so as to have the form of the letter S
reclined. It first ascends in the inner part of the foramen lacerum,
and then runs forward to the root of the anterior clinoid process ;
finally it turns upwards in the groove on the inner side of this pro-
cess, perforates the dura mater forming the roof of the sinus, and
divides into cerebral arteries at the base of the brain. In this
course the artery is enveloped by nerves derived from the sympa-
thetic in the neck.

The branches of the artery here are some small twigs (arteriae
receptaculi) for the supply of the dura mater and the bone, the
nerves and the pituitary body, and, opposite the anterior clinoid
process, the ophthalmic artery.

The terndnal branches of the carotid will be seen in the dis-
section of the base of the brain.

SoiPATHETic Nerve. Accompanying the carotid artery is a
prolongation of the sympathetic nerve of the neck, which forms
the following plexuses : —

The carotid plexus is situate on the outer side of the vessel, at
its entrance into the cavernous sinus, and communicates with the
sixth nerve and the Gasserian ganglion.

The small cavernous plexus is placed below the bend of the artery
which is close to the anterior clinoid j)rocess, and is mainly
derived from that off'set of the upper cervical ganglion which
courses along the inner side of the carotid artery. Filaments from
the plexus unite with the third, fourth, and ophthalmic nerves. One
filament is also furnished to the lenticular ganglion in the orbit,
either separately from, or in conjunction with the nasal nerve.

After forming these plexuses, the nerves surround the trunk of
the carotid, and are continued on the cerebral and ophthalmic
branches of that vessel.

Petrosal nerves. Beneath the Gasserian ganglion is the large
superficial petrosal nerve (fig. 240, 3, p. 678) entering the hiatus

DEEP DISSECTION OF THE BACK. 519

Fallopii to join the facial nerve. External to this is sometimes
seen the snuill superficial petrosal nei-ve (fig. 240, ^), but this is
frequently concealed in the substance of the temporal bone. The
source and destination of these small nerves will be afterwards
learnt. It will suffice now for the student to notice their position,
and to see that they are kept moi.st and fit for examination at a
future time.

Directions. When the study of the l)ase of the skull has been Directions
completed a preservative fluid should be applied, and the flaps i^^yparts.*^
of skin should be stitched together over all.

Section III.

DEEP DISSECTION OF THE BACK.

Directions. During the first two days that the body is placed on Directions,
its face the dissector of the head and neck should be careful not to
let his work interfere with that of the worker on the upper limb,
whose duty it is in this time to dissect the superficial structures
below the level of the seventh cervical spine, and to study and
reflect the first two layers of the muscles of the back, and to
examine the related structures as described in pages 1 to 10. The
dissector of the abdomen also should have the opportunity of
examining the arrangement of the fascia lumborum when it is
displayed on the third day.

Position. The body lies with the face downwards ; and the Position of
trunk is to be raised by blocks beneath the chest and the pelvis, so ^'^^'
that the limbs may hang over the end and sides of the dissecting
table. To make tense the neck, the head is to be depressed and
fastened with hooks.

In this region there are six successive layers of muscles, amongst strata in
which vessels and nerves are interspersed. The student should *^ '
go over again the surface anatomy of the back, as described on
page 2.

Dissection. Make an incision along the middle line of the To raise the
neck from the external occipital protuberance to the spine of the
seventh cervical vertebra, and reflect the skin outwards as far as
the mastoid process above and as far as the outer border of the
acromion below.

On the first day the cutaneous branches of the posterior divisions Clean
of the cervical nerves should be displayed, the trapezius muscle a^d nerves,
cleaned in the neck, and the small occipital nerve traced down
from the scalp in its tube of fascia along the posterior border of
the sterno-mastoid muscle.

To find the nerves in the cervical region, look near the middle
line, from the 3rd to the 6th vertebra, trace an ofi"set from the
third nerve upwards to the head, and follow the great occipital
nerve down from the scalp to its emergence from the muscles.

520

DISSECTION OF THE BACK.

Cutaneous
nerves how
derived.

In the neck

Second

and third
nerves.

The trape-
zius.

Dissection.

Divide
trapezius.

Clean spinal

accessory

nerve

and parts in

posterior

triangle.

Ligamentum
nuchae.

Cutaneous Nerves. The tegumentary nerves of the hack are
derived from the posterior primary hraiiches of the spinal nerves,
which divide amongst the deep muscles into two pieces, inner and
outer. Arteries accompany the greater number of the nerves,
bifurcate like them, and furnish cutaneous offsets.

Cervical nerves (fig. 2, p. 4). In the neck the nerves are
derived from the inner of the two branches into which the posterior
trunks divide: they perforate the trapezius, and supply the neck and
the back of the head. They are four in number, and come from the
second, third, fourth, and fifth nerves.

The branch of the second nerve is named great occipital, and
accompanies the occipital artery to the back of the head, where it
has already been seen (p. 506).

The branch of the third cervical nerve supplies a transverse offset
to the neck, and then ascends to the lower part of the head, where
it is distributed near the middle line, internal to the great occipital
nerve, with which it usually communicates.

The position and attachments of the trapezius in the neck should
be carefully made out and the student may read the description of
the muscles on pages 4 to 6.

Dissection. On the second day the trapezius and latissimus dorsi
muscles are divided longitudinall}' and the parts thrown outwards
and inwards. The trapezius is divided about two inches from the
middle line, but before dividing it the student should make out the
spinal accessory nerve in the posterior triangle of the neck as it passes
downwards and outwards to the under surface of the muscle ; the
nerve being looked for at the posterior border of the sterno-mastoid
about the junction of the upper with its middle third. Parallel
with, but below, the spinal accessory, and comnjunicating with it
beneath the trapezius, will be found branches of the third and
fourth cervical nerves.

The branches of the superficial cervical artery to the under surface
of the trapezius will also be cleaned and after the reflection of the
inner jjart of the muscle the dissector should clean the splenius, and
the upper part of the levator anguli scapulae, and define the things
beneath the clavicle, viz., the posterior belly of the omo-hyoid
muscle (fig. 210, p. 576) with the suprascapular nerve and vessels,
as well as the transverse cervical vessels, and the small nerves
to the levator anguli scapula? and rhomboid muscles. If the
trapezius be detached along the middle line, the ligamentum
nuchas, from which it takes origin, will be brought into view.

The ligamentum NUCH^ is a narrow fibrous band which extends
from the spinous process of the seventh cervical vertebra to the
external occipital protuberance. From its deep surface a thin
layer of fibres, which forms a median partition between the
muscles of the two sides of the neck, is sent forwards to be
attached to the external occipital crest and to the other cervical
spines.

Dissection. On the third day after the latissimus dorsi has been
divided, the dissector of the head and neck is to examine the

THE FASCIA LUMBORUM. 521

lumbar fascia between the last rib and the hip bone, in company
with the worker on the abdomen.

In the region referred to are portions of the external and internal Define
oblique muscles in the wall of the abdomen. Define the posterior oblique^
border of the external oblique (fig. 98, p. 265). Internal to this
the aponeurosis of the transversalis muscle (fascia lumborum, p. 272)
appears, and perforating it are two nerves : one, the last dorsal,
with an artery near the last rib ; and the other, the ilio-hypogastric,
with its vessels close to the iliac crest.

Three layers of the fascia lumborum are to be demonstrated, to show
passing from the aponeurosis of the transversalis to the spinal |^^^^^_^y6rs
column. The superficial layer is already exposed, being formed posterior,
mainly by the aponeurosis of the latissimus dorsi. To see the
middle layer, which passes beneath the erector spinse to the trans-
verse processes, the first layer is to be divided, with the attached
portion of the latissimus dorsi, by a horizontal incision carried
outwards from the third lumbar spine. On raising the outer middle,
border of the erector spinse muscle, which comes into view, the
strong middle process of the fascia will be api^arent.

After cutting in the same way through this prolongation, another and anterior,
muscle, the quadratus lumborum, will be seen ; and, on raising its
outer border, the thin deepest layer of the fascia will be evident
on the abdominal aspect of that muscle.

The FASCIA LUMBORUM Or LUMBAR APONEUROSIS OCCUpieS the Lumbar

interval between the last rib and the iliac crest, and extends ^*^^^^'
inwards to the spine. It is formed mainly by the posterior tendon transversSlis
of the transversalis muscle of the abdominal wall (fig. 101, c, tendon,
p. 271), but its superficial part receives important accessions from
two of the muscles of the back. If the tendon of the transversalis
be followed inwards, it will be found to divide at the outer edge
of the quadratus lumborum into two layers, which encase that
muscle ; and the posterior of these again splits, or gives oflF a
superficial process, at the outer margin of the erector spinsB. There
are thus in the lumbar aponeurosis three layers of membrane, consists of
forming with the vertebrae two sheaths, the one of which encloses *^''®® ^^^^^^ "
the quadratus lumborum, and the other the multifidus and erector
spinse muscles.

The anterior layer is thin, and passes on the abdominal surface anterior,
of the quadratus lumborum to be fixed to the front of the trans-
verse processes of the lumbar vertebrae near their tips.

The middle layer is the direct continuation of the transversalis and middle
tendon, and lies between the quadratus lumborum and the erector ^^rs™"'^'
spinas muscles ; it is fixed to the extremities of the transverse processes ;
processes.

The posterior or superficial layer is the thickest, and is attached posterior to
internally to the spines of the lumbar vertebrae. In this layer are processes,
united the aponeuroses of the latissimus dorsi and serratus posticus
inferior muscles, with only a small offset of the tendon of the
transversalis.

Directions. The structures in the floor of the posterior triangle

522

DISSECTION OF THE BACK

Levator

aiiguli

scapulae.

Posterior
belly of the
omo-hyoid.

Supra-
scapular
artery :
course to
shoulder.

Supra-
scapular
nerve.

Transverse

cervical

artery

divides into

superficial
cervical and

posterior
scapular.

Accompany
ing veins.

Nerve of
rhomboid
muscles.

will be only incompletely displayed at present, but the following
points are to be made out (fij^. 210, p. 576).

1. The levator anguli scapulcB arises by four separate sUps from
the posterior tubercles of the transverse processes of the upper four
cervical vertebrse, and in the case of the upper three slips, they
will be found to be attached immediately in front of those of the
splenius colli muscle.

2. The posterior belly of the omo-hyoid passes from the upjjer
border of the scapula behind the notch, and from the ligament
converting the notch into a foramen, and forms a thin, riband like
muscle, which is directed forwards from beneath the tra[)ezius
across the lower part of the neck, over the brachial plexus and the
suprascapular nerve, to the under surface of the sterno mastoid,
where it ends in the intermediate tendon.

The SUPRASCAPULAR ARTERY, a branch of the subclavian, is
directed outwards through the lower part of the neck to the upper
border of the scapula. It runs behind the clavicle, and crosses
the suprascapular ligament in front of the omo-hyoid muscle, to
enter the supraspinous fossa.

The SUPRASCAPULAR NERVE IS an offset of the fifth and sixth
cervical nerves in the brachial plexus and inclines downwards
beneath the omo-hyoid muscle to the notch in the upper border
of the scapula, through which it passes into the supraspinous
fossa.

The TRANSVERSE CERVICAL ARTERY, also a branch of the sub-
clavian, has the same direction as the suprascapular, towards the
upper angle of the scapula, but it is higher than the clavicle.
Crossing the upper part of the space in which the sub-clavian
artery lies, it passes beneath the trapezius, and divides into
superficial cervical and posterior scapular branches,

a. The superficial cervical branch is distributed chiefly to the
under surface of the trapezius, though it furnishes ofi"sets to the
levator anguli scapulae and the cervical glands.

b. The posterior scapular branch crosses under the levator anguli
scapulae, and descends along the base of the scapula beneath the
rhomboid muscles (p. 9). This branch arises very frequently
from the third part of the subclavian trunk.

The suprascapular and transverse cervical veins have the same
course and branches as the arteries above descril)ed ; they open into
the external jugular, near its junction with the subclavian vein.

Nerve to the rhomboid muscles. This slender offset of the
fifth cervical nerve in the brachial plexus courses beneath the
elevator of the angle of the scapula, and is distributed to the rhom-
boidei on their deep surface. Before its termination it supplies
one or two twigs to the elevator of the scapula.

Dissection. On the third day the rhomboid muscles will have
been reflected and the part will be free to the dissector of the head
and neck for two days, during which time he will examine the rest
of the parts described in this Section, as well as the spinal cord
and the contents of the spinal canal as set forth in Section IV.

SERRATI POSTTCI MUSCLES.

523

tonthpfl two in
tOOineQ n„inber.

After removing the loose areolar tissue beneath the rhomboids
the thin serratus posticus superior muscle will be laid bare. The
serratus posticus inferior has been already displayed by the reflection
of the latissinius dorsi.

The muscles of the third layer are the two serrati muscles. Serrati are
They are very thin, and receive their name from their
attachment to the ribs.
Their origin from the
spines of the vertebrae
is aponeurotic.

The SERRATUS POSTICUS
SUPERIOR (tig. 190, a)
arises from the ligamen-
tum nuchse, and from
the spinous processes of
the last cervical, and
upper two or three dorsal
vertebrae, with the supra-
spinous ligament. The
fleshy fibres are inclined
downwards and outwards,
and are inserted by slips
into four ribs, from the
second to the fifth, exter-
nal to their angles.

The muscle rests on
the splenius, and is
covered by the rhom-
boidei, except at its upper
border.

The SERRATUS POSTI-
CUS INFERIOR (fig. 3, G,

p. 5) is wider than the
preceding muscle. Its
aponeurosis of origin is
inseparably united with
that of the latissinius
dorsi, and with the fascia
lumborum, and is con-
nected to the spinous
processes of the last two

dorsal and upper two or three lumliar vertebrae. The fleshy fibres
ascend somew hat to be inserted into the last four ribs outside their insertion ;
angles, each successive piece extending further forwards than the
one below.

This muscle lies on the mass of the erector spinas ; and with relations,
the upper border of its tendon the vertebral aponeurosis is
united.

Action. Both serrati are inspiratory muscles. The upper one Use of
raises the ribs into which it is inserted : while the lower one draws ^^"'*^^'-

Fig. 190. — Part of the Third and Fourth
Layers of the Muscles of the Back.

A. Serratus posticus superior.

B. Splenius capitis,
c. Splenius colli.

D, Continuation of the ilio-costalis.

e. Longissinius dorsi.

F. Spinalis dorsi.

ongm

524

DISSECTION OF THE BACK.

Vertebral
aponeu-

attach-
ments ;

continua-
tion below,
and above.

Muscles of
fourth layer.

Dissection.

Splenius has
two parts :

one to the
neck :

the other to
the head :

relations.

Use of

splenius

capitis,

splenius
colli.

Divide
splenius,
and seek
nerves.

backwards the lower ribs, and prevents their being carried upwards
by the contraction of the diaphragnj.

The VERTEBRAL APONEUROSIS is a thin fascia which covers the
fourth layer of muscles in the thoracic region. Internally it is
attached to the spinous processes of the vertebrae. Externally it is
fixed to the angles of the ribs ; and in the intervals between the
bones it joins the layer of connective tissue covering the intercostal
muscles. It is continuous below with the tendon of the serratus
posticus inferior, and through this with the superficial layer of the
fascia lumborum ; l)ut above, it passes beneath the upper serratus,
and blends with the deep intermuscular fascia of the neck. The
strongest fibres of the membrane are directed transversely.

Fourth Layer of Muscles. This comprises the splenius
muscle and the erector spiiise, with its divisions and accessory
muscles to the neck.

Dissection. The upper serratus is to be cut through, the
vertebral aponeurosis taken away, and the part of the splenius
muscle under the serratus cleaned. In turning outwards the fleshy
part of the serratus, slender twigs of the intercostal nerves, which
perforate the external intercostal muscle accompanied by small
arteries, may be found entering its slijjs.

The splenius muscle (fig. 190) is flat and elongated. Single
at its origin, it is divided into two parts, one passing to the
head — splenius capitis, and the other to the neck — splenius colli.
It arises from the upper six dorsal and the seventh cervical spines,
and from the ligamentum nuchfe as high as the third cervical
vertebra. The fibres are directed upwards and outwards to their
insertion.

The splenius colli (c marked low down on the left side of the figure)
is inserted by tendinous slips into the posterior tubercles of the trans-
verse processes of the upper two or three cervical vertebrae with, but
behind, the attachment of the elevator of the angle of the scapula.

The splenius capitis (b), much the larger, is inserted into the apex
and hinder border of the mastoid process, and into the outer third
of the sujDerior curved line of the occij)ital bone.

The muscle is situate beneath the trapezius, the rhomboidei, and
the serratus superior ; and the insertion into the skull is beneath
the sterno-mastoid. The complexus muscle appears above the upper
border of the splenius capitis. The splenius represents the pro-
longation to the upper cervical vertebrae and head of the outer
portion of the erector spinas.

Action. The cranial parts of the muscles of the two sides will
carry the head directly back ; and one will incline and rotate the
head to the same side.

The splenius colli of both sides will bend back the upper cervical
vertebrae ; but one muscle will turn the face to the same side, being
able to rotate the head by its attachment to the transverse process
of the atlas.

Dissection (fig. 191, p. 527). The splenius is to be detached
from the spinous processes, and thrown outwards. In doing this,

PARTS OF THE ERECTOR SPIN^. 525

small branches from the external divisions of the posterior cervical
nerves to the pieces of the muscle are to be looked for.

As the ERECTOR SPIN^ is displayed in the doi-sal and lumbar Define off-
regions, two prolongations from it to the cervical vertebrae and the erector
the head are to be defined : — One, a thin narrow muscle, the cervi- SP'"*-
cxilis ascendens, is continued beyond the ribs from the outer piece of
the erector {ilio-costalis), and is to be separated from the muscles
around. The other is a larger ofiset of the inner piece {longissimus
dorsi) of the erector muscle ; single at first where it is united with
the fibres of the longissimus, it is divided afterwards, like the
splenius, into a cranial part (trachelo-mastoid) and a cervical part
(transversalis colli).

The serratus inferior is to be detached from the spines and Show the
thrown outwards, when fine nerves will be found entering it like spin*
those to the upper muscle. The superficial layer of the fascia ^?f. *.^^^
lumborum is also to be removed, and the areolar tissue is to be
cleaned from the surface of the large mass of the erector spinse
which now comes into view. Opposite the last rib is an inter-
muscular interval, which divides the erector spinae into an outer
piece (ilio-costalis), and an inner (longissimus dorsi). By sinking iHo-
the knife into this interval the ilio-costalis may be turned out-
wards, and the longitudinal column of muscle forming the outer
part of the erector spince will be defined.

Its parts are named, from below upwards —

1. The Ilio-costalis.

2. The Musculus accessorius.

3. The Cervicalis ascendens.

The ilio-costalis is a thick mass below, passing on to the lower
ribs, and as it is turned outwards the fleshy slips of the accessorius
will be uncovered, as they are attached to the angles of the ribs,
and from this part its prolongation into the neck as the cervicalis
ascendens can be readily made out. In preparing the ilio-costalis Vessels and
muscle, the external branches of the dorsal nerves with their °^'"^®^-
accompanying arteries will appear.

The attachments of the longissimus dorsi and its prolongation Longissimus
upwards as the inner longitudinal column of the erector spince are *^°"^ •
then to be traced out.

The parts of this column are named, from below upwards —

1. The Longissimus dorsi.

2. The Transvei-salis colli.

3. The Trachelo-mastoid.

Externally the longissimus has thin muscular slips of insertion outer
into about the lower nine ribs, and thicker processes passing to the
transverse processes of the lumbar vertebrae ; the latter may be
shown by raising the outer border of the muscle, and clearing away
the fat between it and the middle layer of the fascia lumborum.
Internally the longissimus is inserted into the transverse processes
of the dorsal, and the accessory processes of the lumbar vertebrae by and inner
rounded tendons ; and to see these it will be necessary to detach a ^^^^ ^^^^'
thin tendinous and muscular portion of the erector mass (sjjinalis spinalis

526

offsets to
the neck.

Vessels and
nerves.

Erector
spinas is
single
below,

divided
above ;

superficial
tendon ;

origin.

Ilio-
costal is ;

origin ;
insertion.

Cervicalis
ascendens :

origin ;

insertion.

Longissimus
dorsi :

DISSECTION OF THE BACK.

darsi) from the inner side of the longissimus, and to divide longi-
tudinally the part of the thick aponeurosis springing from the
lumbar spines, so as to separate the erector from the subjacent
multifidus spinas. From the longissimus, as from the ilio-costalis,
a fieshy piece (transversalis colli and trachelo-mastoid) is continued
into the neck.

Between the longissimus and the multifidus spinse are thei
internal branches of the posterior divisions of the dorsal and;
lumbar nerves, with offsets of the intercostal and lumbar vessels

Erector Spin^. This is the muscular mass on the side of the
spine, extending from the lower part of the sacrum to the head. It
is single and pointed l)elow, attains its greatest size in the loins, and
over the thorax becomes divided into secondary portions to which
the special names are given. Its prolongations to the neck and head
are very slender. On its posterior surface, in the lumbar and sacral
regions, is a strong flat tendon of origin, from which most of thi
fleshy fibres spring. The muscle arises internally from the lowe
two or three dorsal, and all the lumbar and sacral spines ; externally'
from the posterior fifth of the iliac crest at the inner aspect ; and
inferiorly from the lower part of the back of the sacrum. Below
the last rib it divides into the ilio-costalis and longissimus dorsi ;
and in the thoracic region the spinalis dorsi is given off from
the inner side of the latter part.

The ILIO-COSTALIS or sacro-lumbalis is derived from the outer
and superficial part of the common mass of the erector in the loins.
Its fibres end in six or seven tendons, which are inserted into the
angles of as many of the lower ribs. It is continued to the upper
ribs and the neck by the two following muscles —

The ACCESSORius (musculus accessorius ad ilio-costalen] ; fig.
190, d) arises by a series of tendinous and fleshy slips from the
angles of the lower six ribs internal to the insertion of the ilio-
costalis ; and it ends in tendons which are inserted into the remain
ing ribs in a line with the ilio-costalis, and into the transverse
process of the seventh cervical vertebra.

The cervicalis ascendens is a muscular slip prolonging the
accessorius into the neck ; it arises from four ril)s, viz., the sixth,
fifth, fourth, and third, and is inserted into the posterior tubercles
of the sixth, fifth, and fourth cervical vertebrae.

The longissimus dorsi is the largest of the pieces resulting

double
insertion

from the division of the erector spinse, and has two sets of
insertions into the vertebrae and riljs. Internally it gives off a
series of fleshy and tendinous bundles to the accessory processes of
the lumbar vertebrae, and the transverse processes of all the dorsal
vertebrae : externally it is attached by thick fleshy slips to the
transverse processes of the lumbar vertebrae, and the middle layer
of the fascia lumborum, and by thin flattened processes to the ribs,
except the first two or three, lietween the tuberosity and angle. Its
is continued muscular prolongation to the neck is united with the upper fleshy
fibres, and splits into the two following pieces : —

The transversalis colli (fig. 191, b) arises from the transverse

to neck by

transver-
salis colli

TRACHELO-MASTOID MUSCLE.

527

processes of the upper dorsal vertebrae (from four to six), and is
inserted into the po-terior tubercles of the transverse processes of
the cervical vertebrae except the first and the last.

The TRACHELO-MASTOID MUSCLE (transversalis capitis ; fig. 191, and to head
c) arises in common with the preceding, and receives additional nJ^stoid.^ ^
slips from the articular processes of the lower three or four cervical

Fig. 191. — Disskction op the Muscles beneath the Splenius.

A. Longissimus dorsi.

B. Trausversalis colli.^
c. Trachelo-mastoid.
D. Coraplexus.

F. Splenius capitis, cut.

G. Splenius colli, cut.

H. Semispinalis dorsi.
a. Occipital artery.

1. Great occipital nerve.

2. External branch of the second
nerve.

3. Outer branch of the third nerve.

vertebrae. It is inserted beneath the splenius capitis into the
posterior margin of the mastoid process, where it is about three
quarters of an inch wide.

The SPINALIS DORSI is a special innermost part of the erector Spinalis
spiuae ; it is very narrow, and springs from the tendinous slips of ^^^ '
the erector which arise from the lower dor5>al and upper two or
three him bar spines. Its fibres are inserted into a variable number insertion
(from four to nine) of the upper dorsal spines.

528 DISSECTION OF THE BACK. I

Relations of Relations of the erector spince. The erector spinae is concealed
fumbaraud % ^^^ muscles of the layers already examined. It lies over the
dorsal semispinalis and niultifidus spinso muscles, portions of the ribs and

^*^°' ' external intercostal muscles, and the levatores costarum. In the
loins it is contained in the aponeurotic sheath of the fascia lum-
borum, and in the thoracic region a similar sheath is formed for
the muscle by the vertebral aponeurosis with the ribs and dorsal
vertebrae. The tendon of origin is united over the sacrum with
the posterior layer of the fascia luml»orum ; and from its outer
border in this part some fibres of the gluteus maximus arise,
and in neck. The prolongations of the muscle in the neck lie between the
splenius and levator anguli scapulae on the outer side and the com-
plexus on the inner side, the trachelo-mastoid being next to the
complexus. The cervicalis ascendens is attached to the transverse
processes in a line with the splenius colli, and immediately behind
the middle and posterior scalene muscles.
Use of both Action of erector spince. These powerful muscles draw backwards
erec ors, ^^ extend the spine, and come into play in bringing the column
into, and in maintaining the erect position. The parts inserted into
the dorsal vertebrae will be to some extent inspiratory muscles,
since the dilatation of the thorax is aided by extension of the verte-
bral column ; but the slips inserted into the ribs will draw down-
wards these bones, and may thus act in forced expiration. The
of one muscle of one side acting alone will incline the spine laterally. The

ot'^portion" cervical prolongations have a similar action upon the neck and head,
in neck, FiFTH Layer OF MuscLES. In this layer are included the

mri*'^ ^^ complexus, the semispinalis, and the multifidus spinae ; and most of
the vessels and nerves of the back are to be learnt with this layer
of muscles.
Dissection of Disscction. To display the complexus (fig. 191) it will only
comp exus, -^^ necessary to turn outwards the cervical prolongations of the
erector spinae muscle, and follow down the slips of origin to the
dorsal transverse processes. The semispinalis and multifidus are
now partly seen below the complexus, lying between the erector
spinae and the spines of the vertebrae.
Complexus: The COMPLEXUS (fig. 191, d) is internal to the prolongations
from the longissimus dorsi, and converges towards its fellow of the
opposite side at the occipital bone. Narrow at its lower end, the
origin; muscle arises by tendinous slips from the transverse processes of

the upper six dorsal and seventh cervical vertebrae, and from the
articular processes of the succeeding cervical vertebrae as high as
the third : it is also joined in most cases by one or two slips from
the lowest cervical or upper dorsal spines. The fleshy fibres pass
insertion ; upwards to be inserted into an impression between the curved lines
of the occipital bone, which reaches outwards nearly two inches
from the external occipital crest,
tendinous The inner part of the complexus, having tvvo fleshy bellies with

sections ; ^^ intervening tendon, is often described separately as the biventer
cervicis. Another tendinous intersection crosses the cutaneous
surface of the muscle near the upper end.

PARTS BENEATH THE COMPLEXUS. 529

The complexus is concealed by the splenius and trapezius, relations ;
Along the inner side is the semispinals muscle, with the liga-
meutum nuchse. Beneath it are the small recti and obliqui
muscles, the semispinalis, and the posterior cervical nerves and
vessels ; and the cutaneous oflfsets of two or three of the nerves
perforate it.

The complexus may be regarded as the cranial prolongation of use.
the semispinalis muscle.

Action. Both muscles will move the head directly backwards. Dissection
One will draw the occiput down and backwards towards its own side, nerves of

Dissection of vessels and nerves (fig. 192, p. 531). In the neck the neck;
the nerves and vessels will be brought into view by detaching the
complexus from the occipital bone and the spines of the vertebrae,
and carefully raising it from the subjacent parts. Beneath the
muscle are the ramifications of the cervical nerves, and the deep
cervical and other vessels, surrounded by dense connective tissue.

Each nerve, except the first, divides into an inner and an outer inner and
branch. Dissect out first the inner branches, which lie partly over
and partly beneath the fibres of the semispinalis muscle (fig. 192, g).
The external branches are very small, and are given oflF between the outer
transverse processes close to where the trunks appear ; they are to orancnes ;
be looked for outside the complexus, entering the muscles prolonged
from the erector spinse and the splenius.

The small first nerve is the most difficult of the set to find : it is first nerve
a short trunk, contained in the interval between the recti and
obliqui muscles near the head, and will be best found by looking
for the small twigs furnished by it to the muscles around.

The deep cervical artery is met with on the semispinalis muscle ; and the
a part of the vertebral artery will be found in contact with the first vessels:
nerve ; and the occipital artery will be visible crossing the occipital
bone.

Opposite the thorax the dorsal nerves and vessels will be readily nerves and
displayed on the inner side of the longissimus dorsi muscle, on the thg^dorsai
removal of a little fatty tissue from between the transverse pro- region ;
cesses. External and internal branches are to be traced from each
nerve and vessel into the muscles : some of the former have been
seen in the interval between the ilio-costalis and the longissimus
dorsi.

The two branches of the lumbar nerves and vessels are in the in the lum-
same line as the dorsal ; but the inner set are difficult to find.

The sacral nerves are placed beneath the multifidus spinae, and
will be dissected after the examination of that muscle.

Posterior Primary Branches of the Spinal Nerves. The Posterior
spinal nerves, with a few exceptions in the cervical and sacral spinal
groups, divide in the intervertebral foramina into their anterior and nerves,
posterior primary branches. The posterior supply the integuments
and the muscles of the back, and are now to be learnt.

In the neck. The posterior primary divisions of the cervical In the ueck
nerves are eight in number, and issue between the transverse pro-
cesses ; but those of the first and second, which begin on the neural

D.A. M M

630

DISSECTION OF THE BACK.

they divide
into two
except first.

External
blanches
are small.

Internal
branches :

some give
cutaneous
offsets.

Second
ascends to

Third

Biipplies
neck and
head,

First nerve

ends in
muscles.

Dorsal
nerves.

Outer

branches to
erector
spinse :

lower ones

become

cutaneous.

Inner

branches to
transverso-
spinales :

upper ones

reach

surface.

arches of the atlas and axis, appear above those arches. All, except
the first, divide into internal and external branches.

The external branches are very small, and end in the splenius,
and in the muscles prolonged from the erector spinsB.

The internal branches (fig. 192) are larger than the external ;
they are directed towards the spinous processes, the lower three
passing beneath the semispinalis, and the upper four over that
muscle. By the side of the sj)ines cutaneous branches are furnished
to the neck and the head from the nerves that are superficial to the
seniispinalis : these cutaneous offsets ascend to the surface through
the splenius, the complexus, and the trapezius muscles, and are
distributed as already seen (p. 520). In their course the nerves
supply the surrounding muscles, viz., complexus, semispinalis,
multifidus spinse, and iiiterspinales.

The cutaneous branches of the second and third nerves reach the
head, and require a separate notice.

That of the second nerve (fig. 192,2) named great occipital, appears
beneath the inferior oblique muscle, to which it gives offsets, and is
directed upwards through the complexus and trapezius to end over
the occiput (p. 506).

The branch of the third nerve (fig. 192, 2), becoming superficial
near the middle line, gives an offset upwards to the lower part of
the occiput, internal to the preceding. This nerve usually joins
the great occipital twice, viz., beneath the complexus and superficial
to the trapezius.

The posterior primary division of the suboccipital or Jlrst spinal
nerve (fig. 192,^) is very short, and appears in the interval between
the recti and obliqui muscles. In passing from the spinal canal it is
placed between the posterior arch of the atlas and the vertebral artery.
From its extremity branches radiate to the surrounding muscles,
viz., one to the upper part of the complexus, another to the rectus
posticus major and minor, and two short branches to the obliquus
superior and inferior: the offset to the last muscle joins the inner
branch of the second cervical nerve. Occasionally the first nerve
gives a cutaneous branch to the occiput.

In the dorsal regiox. The posterior primary divisions of
the dorsal nerves, twelve in number, appear between the transverse
processes, and bifurcate into internal and external branches.

The external branches increase in size from above downwards,
and pass beneath the longissimus dorsi to the interval between that
muscle and the ilio-costalis, distributing oflfsets to the several
divisions of the erector spinae. The branches of the upper six or
seven nerves end in these muscles ; but the lower five or six, after
reaching the interval between the longissimus and ilio-costalis, are
continued to the surface through the serratus and latissimus
muscles, nearly in a line with the angles of the ribs.

The internal branches are larger above than below, and supply
the trans verso-spin ales muscles. The upper six or seven are directed
inwards between the semispinalis and multifidus spinse, and become
cutaneous by the side of the spinous processes, after perforating the

NERVES OF THE BACK.

531

splenius, serratus superior, rhomboideus, and trapezius muscles. The
lower jive or six are much smaller, and end in the multitidus spinae.

Fig. 192.

Deep Dissection of the Back op the Neck (Illustrations
OF Dissections).

Muscles :

A. Rectus posticus major.

B. Rectus posticus miuur.
c. Obliquus inferior.

p. Obliquus superior,

E. Sterno-mastoid.

F. Coniplexus, cut across.

G. Semispiualis colli.

Arteries :
a. Occipital, and 6, its princeps
cevicis branch.

c. Vertebral artery, and d, its
cervical branch.
e. Deep cervical.

Nerves :

1. Posterior branch of the sub-
occipital,

2 to 7. Inner branches of the
posterior primary divisions of the
respective cervical nerves.

In the loins. The posterior primary branches of the lumbar Lumbar
nerves, five in number, appear between the erector and multifidus dfvid^^^"^
spinse. In their mode of dividing and general arrangement they into two.
resemble the lower dorsal nerves, cutaneous offsets being furnished
by the external set of branches.

M M 2

532

DISSECTION OF THE BACK.

External
branches :

first three

become

cutaneous.

Internal
branches,

Vessels.

Part of the

occiijital

artery,

which
gives a

cervical
branch.

Part of the

vertebral

artery.

Deep cervi-
cal artery.

Dorsal
arteries are
split into

inner and

outer
branches,

and give
a spinal
branch.

The external hranches pass to tlie erector spinae, and supply it
and the intertransverse muscles. The first three pierce the erector
spinae, and become cutaneous after perforating the posterior layer of
the fascia liimborum. The l)ranch of the last nerve is connected
with the corres]3onding part of the first sacral nerve by an offset
near the bone.

The internal hranches are furnished to tlie multifidiis sjjinse
muscle. They are difficult to find, being contained in grooves on
the upper articular processes.

Vessels in the back. The vessels now dissected are the
occipital and the deep cervical arteries, a small part of the vertebral
and the posterior branches of the intercostal and lumbar arteries of
the aorta. Veins accompany the arteries.

The OCCIPITAL ARTERY (fig. 192, a) courses along the occipital
bone. Appearing from beneath the digastric muscle, the vessel is
directed backwards under the sterno-mastoid, the splenius, and,
usually, the trachelo-mastoid, but over the obliquus superior and
complexus muscles. Behind the insertion of the sterno-mastoid it
becomes superficial, and ascends to the occiput, where it is dis-
tributed (p. 503). It supplies the surrounding muscles, and gives
the following branch to the neck : —

The princeps cervicis (fig. 192, b) artery from the occipital
distributes twigs to the splenius and trapezius, and passing beneath
the complexus, anastomoses with the vertebral and deep cervical
arteries.

The VERTEBRAL ARTERY (fig. 192, c) lies ou the neural arch of
the atlas, behind the articulating process, and appears in the
interval between the straight and oblique nmscles. Beneath it is
the suboccipital nerve. Small branches are given to the surround-
ing muscles, and to anastomose with the contiguous arteries.

The DEEP CERVICAL ARTERY (fig. 192, c) arises in common with the
superior intercostal artery from the subclavian. Passing backwards
between the transA^erse process of the last cervical vertebra and the
neck of the first rib, it ascends between the complexus and semi-
spinalis muscles, as high as the upper border of the latter, and
anastomoses with the cervical branch of the occipital artery. The
contiguous muscles receive branches from it, and anastomoses are
formed between its offsets and those of the vertebral.

The POSTERIOR BRANCHES OF THE INTERCOSTAL ARTERIES paSS

back between the vertebrae and the superior costo- trans verse
ligament, and divide like the nerves into inner and outer pieces.

The internal branches end in the fleshy mass of the multifidus
spinse and semispinalis, and furnish small cutaneous offsets with
the nerves.

The external branches cross beneath the longissimus dorsi, and
supply it and the ilio-costalis. Like the nerves, the lowest
branches of this set are the largest, and extend to the surface.

As the dorsal branch of the intercostal artery passes by the inter-
vertebral foramen, it furnishes a small intraspinal artery to the
spinal canal.

THE TRANSVERSO-SPINALES AND THE SEMISPINALIS. 533

The POSTERIOR BRANCHES OF THE LUMBAR ARTERIES divide, like Lumbar

the foregoing, into internal and external pieces, as soon as they*

reach the interval between the erector and niultitidus spine. Each divide also

gives also a spinal branch to the spinal canal. ^" "

The internal branches are small, and end in the multifidus spinse: inner and

The external branches supply the erector spinse ; and offsets are outer
continued to the integuments with the superficial nerves. '^^"^ ^^^'

Veins. The occipital veins communicate usually with the lateral Occipital
sinus of the skull through the mastoid foramen, and pass beneath
the complexus to enter the deep cervical vein.

The deep cervical vein is of large size, and besides receiving the Deep cervi-
occipital veins, communicates with the other deep veins of this and plexus
region, forming the posterior plexus of the neck. It passes for- ^f ^^^^
wards with its artery between the transverse processes, and joins
the vertebral vein.

The vertebral vein begins above the neural arch of the atlas by Beginning
the union of an offset leaving the spinal canal with the artery and brai vein,
branches from the al)ove-mentioned plexus.

The dorsal and lumbar veins agree in their branching and Dorsal and
distril)ution with the arteries they accompany, and end in the "^" ^'
corresponding trunks of the thoracic and abdominal wall.

In contact with the spinous processes and laminae of the vertebrae and deep
is a deeper set of veins {dorsal spinal), which anastomose freely '
together, and communicate through the ligamenta subflava with the
veins in the interior of the spinal canal.

Transverso-Spinales. Occupying the vertebral groove by the Transverso-
side of the spinous processes is a long muscular mass, which extends ^^'"
from the lower part of the sacrum to the axis. This is composed
of slips which are directed obliquely from transverse or articular arrange-
processes to spinous processes, and are therefore designated collec- ™^"^'
tively transverso-spinales. The slips differ in length, and form
three layers, which are described as separate muscles, yiz., a
superficial stratum of long slips, confined to the cervical and dorsal and sub-
regions — the semi spinalis ; a middle portion, wdth slips of inter-
mediate length — the multifidus spince ; and a deep set of very short
fasciculi, present only in the thoracic region — the rotatores dorsi.
The semispinalis and multifidus are only to be separated with
difficulty ; but the rotatores are more distinct, and are included in
the next layer.

The semispinalis consists of slips which pass over four or five Semispinalis
vertebrae, and it is subdivided into the following two parts, but the jntJ^' ^
separation between them is not always distinct.

The semispinalis dcn'si is thinner than the upper ])art ; it o.rises semispinalis
from the transverse processes of the dorsal vertebrae Irom the sixth
to the tenth, and is inserted into the spines of the last two cervical and
the u{)per four dorsal vertebrae.

The semispinalis colli (fig. 192, g) arises from the transverse and semispi-
processes of the upper six dorsal vertebrae, and is inserted into the
spines of the cervical vertebrae above the last, excej)t into the atlas,
The insertion into the massive spine of the axis is much the largest.

534

DISSECTION OF THE BACK.

Dissection
of multifi-
dus sjtinaj.

Origin of
multifldus
spinas
from pelvis,

from lumbar,
dorsal, and

cervical
vertebrae ;

insertion
into spines.

Relations of
traiisverso-
spinales ;

and use.

Muscles of
the sixth
layer.

Dissection
of suboccipi-
tal muscles.

and other
muscles of
last layer.

Rectus
posticus
major :

Dissection. The multifldus spinse is now to be prepared. The
upper part of it Avill be exposed by cutting through the insertion
of the seniispinalis, and turning aside that muscle.

Over the sacrum the thick aponeurosis of the erector spina)
must be removed. In the dorsal region the multifldus spina) will
appear on detaching and reflecting the semispinalis from the spines.
The slips by which the muscle is attached to the processes of the
vertebrae should be deflned and separated.

The MULTiFiDUS SPiNiE reaclics from the sacrum to the axis :
it is larger below than above, and is smallest in the upper dorsal
region. It takes origin at the pelvis from the back of the sacrum
between the spines and the external row of processes as low as the
fourth aperture, from the posterior sacro-iliac ligament, from the
inner side of the posterior superior spine of the ilium, and from the
overlying tendon of the erector spinas ; in the loins it arises by large
fasciculi from the mamillary processes of the vertebrae ; in the
dorsal region by thinner slips from the transverse processes ; and
in tlu neck from the articular processes of the lower four cervical
vertebrae. From these attachments the fibres are directed obliquely
upwaids and inwards, passing over from one to three vertebrae, to
be inserted into the spinous processes from the axis to the last lumljar
vertebra.

The trans verso-spin ales are entirely concealed by the erector
spinas and complexus muscles ; and beneath them are the laminae
of the vertebrae, with the dorsal spinal plexus of veins. Internally
they rest against the spinous processes and the interspinal muscles.

Action. The trans verso-spinales of the two sides acting together
will extend the spine : and the muscles of one side can rotate the
column in the cervical and dorsal regions, turning the face in the
ojDposite direction.

Sixth Layer of Muscles. This layer includes a number of
short muscles which pass between adjacent vertebrae, or from the
first two vertebrae to the head. They are : —

1. The rectus capitis posticus major.

2. The rectus capitis posticus minor.

3. The obliquus capitis superior.

4. The obliquus capitis inferior.

5. The rotatores dorsi.

6. The interspinales.

7. The intertransversalis.

Dissection. Between the first two cervical vertebrae and the
occipital bone are the recti and oblique muscles, which are to
be fully cleaned.

The slips of the multifldus spinae are to be detached from the
spines of the vertebrae and turned downwards in order to show the
rotatores dorsi in the thoracic region, and the interspinal muscles in
the neck and loins. The intertransverse muscles of the lumbar
region will be exposed by removing the erector spinae.

The RECTUS CAPITIS POSTICUS MAJOR (flg. 192, a) arises from
the side of the spinous process of the axis, and is inserted into the

SUBOCCIPITAL TRIANGLE. 535

outer part of the inferior curved line of the occipital bone for about attach-
an inch, as well as into the surface l)elo\v it. ments;

The muscle is covered by the complexus, and, at its insertion, by relations;
the obliquus superior. It lies over the posterior arch of the atlas
and the ligaments attached to that part of the bone,

Action. By the action of both muscles the head will be drawn and use.
backwards. One rectus acting alone will rotate, as well as extend
the head, turning the face to the same side.

The RECTUS CAPITIS POSTICUS MINOR (fig. 192, B) is a small fan- Rectus pos-

shaped muscle, lying to the inner side of the preceding. Arising ^^^^^ "^^^^^ '
close to the middle line from a slight roughness on the posterior
arch of the atlas, it is inserted into the inner third of the inferior attach-
curved line of the occipital bone and an impression below this. ^^^ '

This muscle is deeper than the rectus major, and lies Over the pos- relations ;
terior occipito-atlantal ligament. The two small recti correspond
to the interspinal muscles between the other vertebrae.

Action.. The rectus posticus minor extends the head. and use.

The OBLIQUUS CAPITIS INFERIOR (fig. 192, c) is the strongest of obiiquus
the suboccipital muscles. It arises from the spinous process of the iiif6"or:
axis below the rectus posticus major, and is inserted into the lower attach-
and back part of the transverse process of the atlas. ments ;

The inferior oblique is concealed by the complexus and trachelo- relations ;
mastoid muscles, and is crossed by the great occipital nerve.

Action. This muscle turns the face to the same side, by rotating and use.
the atlas on the axis.

The OBLIQUUS CAPITIS SUPERIOR (fig. 192, d) arises from the Obiiquus
transverse process of the atlas above the insertion of the pre- s"P«"or =
ceding muscle, and is directed upwards and inwards to be inserted attach-
into the outer part of the space between the curved lines of the ""®°^'*'
occipital bone.

The origin of the muscle is beneath the trachelo-mastoid, and its relations
insertion beneath the complexus. In the interval between these it
is covered by the splenius. It lies over the vertebral artery and
the insertion of the rectus posticus major.

Action. With its fellow the upper oblique will assist in carrying and use.
backwards the head. By the action of one muscle the head will
be inclined backwards, and to the same side.

Suboccipital triangle. This name is given to the small space Triangular
which is bounded below by the obiiquus inferior muscle, by the tween the
rectus posticus major on the inner side and above, and by the ™»iscies:
obiiquus superior on the outer side. It is covered by the com-
plexus ; and its floor is formed by the neural arch of the atlas,
with the posterior occipito-atlantal ligament. In it are seen a small contents,
part of the vertebral artery, and the posterior branch of the sub-
occipital nerve issuing below the artery and lying upon the posterior
arch of the atlas.

The contents of the sub-occipital traingle should be fully displayed
before the following parts are studied.

The rotatores dorsi are eleven short muscular slips in the Rotatores
dorsal region beneath the multifidus spinse, from which they

536

DISSECTION OF THE BACK.

attach-
ments.

Interspinal
muscles :

in neck ;

in dorsal
region :

in loins ;

their use.

Inter-
transverse
muscles :

in neck ;

in dorsal
region ;

in loins

their use.

Dissection
of sacral
nerves.

Five sacral
nerves.

are separated by fine areolar tissue. Each arises from the upper
and back part of a transverse process, and is inserted into the
lower border of the neural arch of the vertebra next above. The
first springs from the transverse process of the second vertebra.

The INTERSPINALES are arranged in pairs in the intervals
betvi^een the spinous processes. They are most developed in
the neck and loins.

In the cervical region they are small rounded bundles
attached to the bifurcated extremities of the spines from the
axis downwards.

In the doi'sal region interspinal muscles are only present in one
or two of the highest and lowest spaces .

In the lumbar region they are thin flat muscles, reaching the
whole length of the spine, one on each side of the interspinous
ligament.

Action. The muscles help to extend the spine.

The INTERTRANSVERSALES lie between the transverse processes
of the vertebrae ; but only those in the loins and the back are now
dissected.

In the neck they are dou1)le, and resemble the intersjDinal muscles
of the cervical vertebrae.

In the dorsal region they are single rounded bundles of small
size, and are found only between the four or five lower vertebrae.
They are represented in the middle spaces by thin fibrous bands,
which constitute the so-called intertransverse ligaments.

In the lumbar region there are two muscles in each space. The
outer set are thin flat muscles between the transverse processes.
The inner muscles are rounded bundles in a line with those of the
dorsal region ; they are attached to the accessory processes above,
and the mamillary processes below ; and the highest is between the
last dorsal and the first lumbar vertebrae.

Action. The intertransverse muscles assist in bending the spine
laterally.

Dissection (fig. 193, p. 537). To see the posterior divisions of
the sacral nerves, it will be necessary to remove the part of the
multifidus spinae covering the sacrum. The upper three nerves are
each split into two ; their external branches will be found readily
on the great sacro-sciatic ligament, from which they may be
traced inwards ; the inner branches are very slender and difficult
to find.

The lower two nerves are very small, and do not divide like
the others. They are to be sought on the back of the sacrum,
below the attachment of the multifidus spinae. The fourth comes
through a sacral aperture, and the fifth between the sacrum and
coccyx. The coccygeal nerve is still lower, by the side of the
coccyx.

Sacral nerves (fig. 193). The posterior primary branches of
the sacral nerves are five in number. Four issue from the spinal
canal by the apertures in the back of the sacrum, and the fifth
between the sacrum and the coccyx. The first three have the

SACRAL NERVES.

537

common branching into inner and
spinal nerves ; but the last two
are undivided.

The first three nerves (1 s, 2 s
and 3 s) are covered by the
multifidus spinae, and divide
regularly.

The in7ier pieces (^) are distri-
buted to the multifidus ; the last
of this set is very fine.

The outer pieces (2) are larger,
and have communicating offsets
from one to another on the back
of the sacrum ; the branch of the
first is also connected with the cor-
responding part of the last lum-
bar nerve ; and the branch of the
third joins in a similar way the
sacral nerve next below. After
this looping they pass outwards
to the surface of the great
sacro-sciatic ligament, where they
join a second lime, and become
cutaneous.

Last two nerves (4 s and 5 s).
These nerves, which are below
the multifidus, are much smaller
than the preceding, and want the
regular branching of the others:
they are connected with each
other and the coccygeal nerve
by loops on the back of the
sacrum. A few filaments are
distributed over the back of the

outer pieces, like the other

First three
have

inner and

outer
branches ;

latter give
cutaneous
offsets.

FtG.

coccyx.

Coccygeal nerve (1 c). Its
posterior primary branch issues
through the lower aperture of the
spinal canal, and appe<irs by the
side of the coccyx. It is joined
in a loop with the last sacral
nerve, and ends on the posterior
surface of the coccyx.

Sacral arteries. Small
branches of the lateral sacral
arteries leave the spinal canal
with the sacral nerves ; they
supply the multifidus spinse, and
anastomose on the back of the sacrum with offsets from the ghiteal
and sciatic arteries

-Dissection of the Pos-
terior Divisions of the Sacral
Nerves.

Muscles :

A. Multifidus spinte, and B. Erector
spinae : both cut.

c. Gluteus maximus detached from
its origin, and thrown down.

D. Great sacro-sciatic ligament.

Nerves ;

51. Last lumbar.

1 s to 5 s. The five sacral nerves
issuing from the sacrum.

1 c. The coccygeal nerve escaping
by the opening of the sacral canal.

1. Internal offsets of the last
lumbar and first three sacral (theae
are represented too large).

2. External offsets of the same
nerves.

3. Anterior, and 4,
primary branch of the
nerve.

5. The nerve derived from the an-
terior divisions of the last two sacral
and the coccygeal nerves, piercing
the great sacro-sciatic ligament and
the gluteus maximus muscle.

Last two are
undivided.

Coccygeal
nerve.

posterior
coccygeal

Small sacral
arteries.

538

DISSECTION OF THE BACK.

Dissectfon
of costal
muscles.

Levatores
costarum :

attach-
ments.

The first.

Longer

elevator

muscles.

Use.

Outer

intercostal

muscle.

Dissection.

Dorsal
nerve has

posterior

and anterior
branches.

Intercostal
artery.

Dissection. The posterior part of the wall of the thorax may be
examined before the body is again turned. By removing, opposite
the ribs, the ilio-costalis and longissimus dorsi, the small levatores
costarum will be imcovered. The hinder part of the external
intercostal muscles will be denuded at the same time.

The LEVATORES COSTARUM are twelve small fan-shaped muscles,
which are connected with the hinder parts of the ribs. Each,
except the first, arises from the tip of the transverse process of a
dorsal vertebra, and is inserted, the fibres spreading out, into the
upper border of" the rib beneath, from the tuberosity to the angle.
The muscles increase in size from above down, and their fibres have
the same direction as the external intercostal layer.

The first is fixed above to the transverse process of the last cervical
vertebra, and below to the outer border of the first rib. Some of
the fibres of the lower muscles are continued beyond one rib to that
next succeeding : these longer slips have been named levatores
longiores costarum.

Action. These muscles have but little influence in elevating the
ribs ; and their principal use appears to be in extending and bending
laterally the spine.

The EXTERNAL INTERCOSTAL MUSCLE is continued backwards
along the ribs as far as the tuberosity, where it joins the elevator
mnscle. Beneath the muscle are the intercostal nerve and artery.

Dissection. To trace the anterior and posterior primary
branches of the dorsal nerves to their common trunk, the elevator
of the rib and the external intercostal muscle are to be cut through
in one or more spaces. The intercostal artery with its posterior
branch is laid bare by this proceeding.

The DORSAL NERVES Split in the intervertebral foramina into
anterior and posterior primary branches.

The -posterior branches are directed backwards, internal to the
superior costo-transverse ligament ; aud their distribution has
been seen in the foregoing dissection.

The anterior named intercostal, are continued between the ribs to
the front of the chest : their anatomy has been learnt in the
dissection of the thorax and upper limb.

The INTERCOSTAL ARTERY has an almost exact correspondence
with the dorsal nerve in its branching and distribution.

SECTIOJf IV.
THE SPINAL CORD AND ITS MEMBRANES.

Cord is con-
tained in
spinal canal,

invested by
membranes.

The spinal cord (medulla spinalis) gives origin to the spinal
nerves, and is lodged in the canal bounded by the bodies and
neural arches of the vertebrae. It is invested by prolongations
of the membranes of the brain, which form sheaths around and
support it.

MEMBRANES OF THE CORD. 539

Dissection. After all the muscles have been taken from the Dissection
arclies and spines of the vertebrae, the spinal canal is to be opened ^he^cord
by sawing through the laminae on each side, close to the articular
processes ; and the cuts of the saw should extend to the lower end
of the sacrum, but not higher in the neck than the fourth cervical
vertebra. As it is difficult to use the saw in the hollow of the
lumbar region, a chisel and a mallet will be foimd useful to
complete the division of the neural arches.

The tube of the dura mater is covered by some veins and fat, and the
and by a loose areolar tissue containing fluid sometimes, especially "^^™ ranes.
at the lower part. The fat may be scraped away with the handle
of the scalpel ; and the lateral prolongations of the membrane
through the invertebral foramina are to be defined.

Membranes of the Cord (figs. 190 and 195, p. 540). Three Spinal
membranes, like those on the brain, surround the cord, viz., an are three
external tube of dura mater, an internal covering of pia mater, "* number,
and an intermediate sheath of arachnoid.

The DURA MATER (a) is the strongest tube, and is continuous Dura mater
with the membrane lining the interior of the skull. It forms a suirounds
loose sheath (theca) along the spinal canal as far as the last lumbar ^"^^ loosely;
vertebra ; and then ttipering gradually it ends opposite the second lower
or third piece of the sacrum in a slender imper\ious cord which is ^°^'"g >
continued to the back of the coccyx (fig. 194 b). The capacity of
the sheath greatly exceeds the dimensions of the cord ; and it is size of
larger in the neck and loins than in the dorsal region. sheath ;

On the outer aspect the spinal dura mater is smooth, in com- connec-
parison with that in the skull, for it does not act as a periosteum *^°°^ '
to the bones. Between it and the w^all of the canal are some vessels
and fat ; and it is connected to the posterior common ligament of
the vertebrae by a few fibrous bands.

On each side the durer mata sends offsets along the spinal nerves offsets on
in the intervertebral foramina ; and these ofisets become gradually °^^^'*^^ »
longer below (fig. 194), where they form tubes w^hich enclose the
sacral nerves, and lie for some distance with the spinal canal. In median
the centre between the lowest offsets on the nerves, is the slender ^ocesl
fibrous cord (6), which blends with the periosteum covering the
back of the coccyx.

Dissection. To remove the spinal cord with the sheath of the Dissection
dura mater from the body, the lateral processes in the intervertebral cor^™°^^
foramina, with the contained nerves, are to be cut ; and one or two
of them in the dorsal region should be followed outwards beyond
the apertures by cutting aw^ay the surrounding bone. The central
prolongation may be now detached from the coccyx ; and the
membranes are to be divided opposite the fourth cervical vertebra,
and to be removed with the contained cord, which has already been
severed in the removal of the brain, by cutting the bands that
attach the dura mater to the posterior common ligament.

When the cord is taken out, place the anterior surface ui)permost, and see next
with the lateral offsets widely separated. To show the arachnoid ^°^^""8-
covering, the dura mater is to be slit along the middle as far as the

540

THE SPINAL CORD AND ITS MEMBKANES.

Deep surface
of dura
mater.

small terminal fibrous cord before referred to ; but tlie membrane
is to be raised while it is being cut through, so that the loose arach-
noid on the cord may not be injured. After its division, fasten
back the dura mater to a long cork strip with pins.

The inner surface of the dura mater is now seen to be smooth

Fig. 194. — Lower end op
THE Dura Mater with
ITS Central and Lateral
Processes.

a. Sheath of dura mater.

b. Central fibrous band fix-
ing it to the coccyx. The
lateral offsets encasing the
last two lumbar, the five
sacral, and the coccygeal
nerves are also shown. Each
nerve is marked by the
numeral, and the first letter
of its name.

Fig. 195.

-Membranes of the Spinal
Cord.

a. Dura mater cut open and reflected.

b. Small part of the translucent arachnoid.
h. Pia mater, closely investing the spinal

cord.

c. Ligamentum denticulatum on the side
of the cord, shown by cutting through the
anterior roots of the nerves.

d. Processes joining it to the dura mater.

e. Anterior roots of the nerves, cut ; and
/, posterior roots, each entering a separate
hole in the dura mater.

g. Linea splendens.

Subdural
space.

Arachnoid
membrane
is loose,

and shining, and everywhere free except at the spots along each side
where it is perforated by the nerves, and where it gives attachment
to the processes of the ligamentum denticulatum. The cavity
between the dura mater and the arachnoid is named the subdural space.
The ARACHNOID (fig. 195,6) is the thin translucent covering of
the cord immediately beneath the dura mater. It surrounds the

•SPINAL PIA MATER. 541

cord loosely, so as to leave a considerable interval between the two and leaves
— the subarachnoid space. The loose sheath is largest at its lower beT^th.
part, where it envelops the mass of nerves forming the cauda
equina. Around the roots of each nerve the arachnoid forms a
short tube, which is lost as they perforate the dura mater.

Dissection. The subarachnoid space may be made e\ident by To show
placing the handle of the scalpel beneath the membrane, or by noidTpace.
putting a piece of the cord in water and blowing air between the
arachnoid and pia mater.

The subarachnoid space separates the arachnoid membrane from Suharach-
the spinal cord invented by the pia mater. It is larger below than ""' ^^^^
above, and is occupied by the cerebrospinal fluid. Superiorly it is contains a
continuous with the cranial subarachnoid space ; and it com- "' ' *"
niunicates with the cavity in the interior of the brain by means opens into
of an aperture in the lower part of the roof of the fourth of brahiT
ventricle (the foramen of Majendie\ Along the back of the cord the
space is imperfectly divided by a median partition {septum posticum) an imperfect
composed of bundles of fibrous tissue, which is most developed in behind!
the neck. Similar fine trabeculae pass between the posterior nerve-
roots and the arachnoid. The subarachnoid space also contains the
ligamentum denticulatum, and the roots of the spinal nerves, with
some vessels.

Dissection. In order to see the next covering of the cord, with Dissection
the ligamentum denticulatum, the arachnoid membrane is to be covering,
taken away ; and two or three of the anterior roots of the upper
dorsal nerves may be cut through and reflected, as in fig. 195.

The PIA MATER (fig 195, /i) is much less vascular on the spinal Pia mater
cord than on the brain. Thicker and more fibrous in its nature, the
membrane closely surrounds the cord with a sheath, and sends a supports
thin fold into the anterior median fissure ; it furnishes coverings to '

the roots of the spinal nerves. gives offsets.

The outer surface of the pia mater is rough. Along the front is Fibrous
a median fibrous band (linea splendens ; fig. 195, g) ; and on each
side another fibrous band, the ligamentum denticulatum, is attached
to it. In the cervical region the membrane has usually a rather
dark colour, due to the presence of pigment cells in it.

Where the spinal cord ceases, viz., about the lower edge of the it ends
body of the first lumbar vertebra, the sheath of the pia mater con- .^^ajYfibrous
tracts, and gives rise to a .>>lender thread-like prolongation, the cord, the
filum tei'minale or central ligament of the cord (fig. 197 rf p. 546). terminaie.
This contains a little nervous substance in its upper part ; and
be1ow% it blends with the central impervious process of the dura
mater. A vein and artery accompany the filum terminaie, and
distinguish it from the surrounding nerves.

The ligamentum denticulatum (fig. 195, c) is a white, fibrous band The dentate
on each side of the spinal cord, and has received its name from its ligament
serrated appearance. It serves to support the cord, w^hich is fixed
by it to the sheatli of the dura mater.

Situate between the anterior and posterior roots of the nerves, the is fixed on
band reaches upwards to the beginning of the medulla oblongata, ^coid^

542

and on other
to dvira
mater ;

number and
attachment
of points.

Vessels and
nerves of
dura mater;

of arach-
noid ;

of pia mater.

Dissection
of roots of
nerves.

and the

ganglion.

Trunks of

spinal

nerves.

Number
and groups.

Relation of
nerves to
vertebrae.

Primary
divisions.

Roots,
anterior and
posterior.

THE SPINAL CORD AND ITS MEMBRANES.

and ends below on the pointed extremity of the cord, Internally it
is united to the pia mater. Externally it ends in a series of tri-
angular or tooth-like projections (f/), which are fixed at intervals
into the dura mater, each being about midway between the aper-
tures of the roots of the spinal nerves. There are twenty or twenty-
one denticulations, of which the first is attached to the dura mater
opposite the margin of the occipital foramen, and the last, opposite
the twelfth dorsal or the first lumbar vertebra.

Vessels and nerves of the Tnembrane. The spinal dura mater has
but few vessels in comparison with that in the skull, as it has
not the same periosteal office. Filaments of the sympathetic and
spinal nerves are furnished to the membrane.

The arachnoid has no vessels ; and jDroof of its containing nerves
in man is yet wanting.

The pia mater has a network of vessels in its substance, though
this is less marked here than on the brain ; and from them offsets
enter the cord. In the membrane are many nerves derived from
the sympathetic and the posterior roots of the spinal nerves.

Dissection. The arachnoid membrane is to be taken away on
one side ; and the nerve roots are to be traced outwards to their
transmission through apertures in the dura mater.

One of the offsets of the dura mater, which has been cut off some
length, is to be laid open to expose the contained ganglion. The
student should define the ganglion, showing its bifid condition
at the inner end (fig. 196, 6), and should trace a bundle of
threads of the posterior root into each point. The anterior root,
consisting also of two bundles of threads, is to be followed over
the ganglion to its union with the posterior root beyond the
ganglion.

Spin A.L Nerves. There are thirty-one pairs of spinal nerves;
and each nerve is constructed by the blending of two roots (anterior
and posterior) in the intervetebral foramen.

They are divided into groups corresponding with the regional
subdivisions of the spinal column, viz., cervical, dorsal, lumbar,
sacral, and coccygeal. In each group the nerves are the same in
number as the vertebrae, except in the cervical region, where
they are eight, and in the coccygeal region where there is only one.
The cervical nerves from the first to the seventh pass out above the
several vertebrae ; and the eighth is below the last cervical vertebra ;
the succeeding nerves are placed each below its corresponding
vertebra.

Each nerve divides into two primary branches, anterior and
posterior ; the former of these is distributed to the front of the
body and the limbs ; and the latter is confined to the hinder part
of the trunk.

Roots of the nerves (fig. 196). Two roots (anterior and
posterior) attach the nerve to the spinal cord ; and these unite
together to form a common trunk in the interverteljral foramen.
The posterior root is marked by a ganglion, but the anterior root is
aganglionic.

ROOTS OF THE NERVES.

543

The posterior or ganglionic roots (fig. 196, A, b) are larger than
the anterior, and are formed by thicker and more numerous fibrils.
They are attached to the side of
the cord between the posterior
and lateral columns in a straight
line, which they preserve even to
the last nerve.

In their course to the trunk of
the nerve the fibrils converge to
an aperture in the dura mater,
opposite the intervertebral fora-
men ; as they approach that aper-
ture they are collected into two
bundles (fig, 196, b, b) which,
lying side by side, receive a sheath
from the dura mater, and enter
the two points of the intervertebral
ganglion.

The intervertebral ganglion (fig.
196 A, c) is reddish in colour and
ctval in shape ; and its size is pro-
portioned to that of the root. By
means of the previous dissection,
the ganglion may be seen to be
bifid at the inner end (fig. 196 b),
where it is joined by the bundles
of filaments of the root (6) ; or the
root might be said to possess two
small ganglia, one for each bundle
of filaments, which are blended at
their outer ends.

Sometimes the first or subocci-
pital nerve is without a ganglion.

The anterior or aganglioiiic roots
(fig. 196 A, a) arise from the side
of the spinal cord by filaments
which are attached irregularly —
not in a straight line, and approach
near the middle fissure at the
lower end of the cord.

Taking the same direction as
the posterior root to the inter-
vertebral foramen, the fibrils enter
a distinct opening in, and have a
separate sheath of, the dura mater.
In their farther course to the trunk

of the nerve they are gathered into two bundles (fig. 196 B, a),
and pass over the ganglion without joining it. Finally, the anterior
root blends with the posterior beyond the ganglion, to form the
trunk of the nerve.

Posterior
larger than
anterior.

Ganglia :

form,

and size ;

each is
bitid.

•

Plan op the Origin op a
Spinal Nerve from the
Spinal Cord.

a.
b.
c.
d
e.
lie

Anterior root.
Posterior root.

Ganglion on the posterior root.
Anterior primary branch.
Posterior primary branch of
Derve-trunk.

B. A Drawing to show the
Arrangemkxt of the
Nervk-roots, and the form
of the Ganglion in a Lum-
bar Nerve.

b, b. Posterior root gathered into
two bundles of threads.

c. The ganglion, bifid at the
inner end.

a, a. Filaments of the anterior
root, also gathered into two bundles.

Anterior
root is
withnut
ganglion,

pierces
dura mater
and joins
posterior
root beyond
ganglion.

644

THE SPINAL CORD AND ITS MEMBRANES.

Characters
of roots.

Some sets
of fibrils
join ;

snor
root larger,

pj'oportion-
ally largest
in neck.

Roots are
largest for
nerves of
limbs.

Oblique in
their course,

most so
inferiorly,

where they
form Cauda
equina.

Length in-
creases from
above
downwards.

Union of
the roots
in inter-
vertebral
foramen.

except in
first two
cervical,

the sacral,

and coc-
cygeal
nerves.

Situation of
ganglia.

Exceptions
in cervical.

Characters of the roots. Besides variations in the relative size of
the two roots, the following characters are to be noted : —

Union of the fibrils. The fihrils of contiguous anterior roots may
be intermingled, and the fil)rils of the neighbouring posterior roots
may be connected in a like manner ; but the anterior is never
mixed with the posterior root.

Size of the roots to each other. The posterior root is larger than
the anterior, except in the suboccipital nerve ; and the number of
the filaments is also greater. Farther, the posterior is propor-
tionally larger in the cervical than in any other group ; in the
dorsal nerves there is but a very slight diff'erence in favour of the
hinder root.

Size of both roots along the cord. Both roots are larger where the
nerves for the limljs arise than at any other part of the cord ; and
they are largest in the nerves to the lower limbs. They are
smallest at the lower extremity of the cord.

Direction and length of the roots. As the apertures of transmission
from the spinal canal are not generally oj^posite the place of origin
of the nerves, the roots are for the most part directed obliquely.
This obliquity increases from above downwards ; for in the upper
cervical nerves the roots are horizontal ; but in the lumbar and
sacral nerves they have a vertical direction around the filura
terminale (fig. 197) ; and the bundle of long nerve-roots descending
from the end of the spinal cord, from its resemblance to a horse's
tail, is named the Cauda Equina.

The length of the roots increases in proportion to tlieir obliquity.
Thus, the distance between the origin and the place of exit of the
roots of the lowest cervical nerve equals the depth of one vertebra ;
in the lowest dorsal nerve it amounts to the depth of two vertebrae ;
and in the lumbar and sacral nerves each succeeding root becomes
nearly a vertebra longer, for the cord does not reach beyond the
first lumbar vertebra.

Place of union of the roots. Commonly the roots unite as before
stated in the intervertebral foramina ; and the trunk of the nerve
bifurcates at the same spot into anterior and posterior primary
branches (fig. 196, d and e). But deviations from this arrangement
are found at the upper and low^er ends of the spinal column in the
following nerves.

The roots of the first two cervical nerves join on the neural
arches of the corresponding vertebrae ; and the anterior and posterior
primary branches diverge from the trunks in that situation.

In the sacral nerves the union of the roots takes place within
the spinal canal ; and the primary branches of the nerves issue by
the apertures on the front and back of the sacrum.

The roots of the coccygeal nerve are also united in the spinal
canal ; and the anterior and posterior branches of its trunk escape
by the lower aperture of that canal.

Situation of the ganglia. The ganglia are placed commonly in the
intervertebral foramina, but where the position of these apertures
is irregular, as at the upper and lower extremities of the spinal

EXTEKNAL CHARACTERS OF CORD. 545

column, they have the following situation : — In the first two nerves
they lie on the neural arches of the atlas and axis. In the sacral sacral, and
nerves they are contained in the spinal canal ; and in the coccygeal coccygeal,
nerve the ganglion is usually within the sac of the dura mater.

Vessels of the spinal cord. The arteries on the surface of Arteries of
the cord are anterior and posterior spinal.

The anterior spinal artery occupies the middle line of the cord Anterior
beneath the fibrous band before alluded to in that position. It a^s'ingie
begins by the union of two small branches of the vertebral artery artery ;
within the skull, and it is continued to the lower end of the cord
by a series of anastomotic branches, which are derived from the
vertebral and ascending cervical arteries in the neck, and from the
intercostal arteries in the dorsal region. Inferiorly it supplies the tennina-
roots of the nerves forming the cauda equina, and ends on the
central fibrous prolongation of the cord. The branches of this offsets,
artery ramify in the pia mater, some entering the median fissure.

The 2)ost£rior spinal arteries, one on each side, are continued from Posterior
the upper to the low^er part of the cord, behind the roots of the two"^^ ^^^
nerves. These vessels are furnished from the vertebral artery
within the skull, and their continuity is maintained by a series of
ana?Jtomotic ofisets, which enter the canal along the spinal nerves.
Dividing into small branches, the vessels of opposite sides form a lie on sides
free anastom<jsis around the posterior roots, and some twigs enter
the posterior septa of the cord.

The veins of the spinal cord are very tortuous and form a plexus Veins :
on the surface. At intervals larger trunks arise, which accompany termina-
the spinal nerves to the intervertebral foramina, and end in the ^^'^^^ •
veins outside the spinal canal. Near the top of the cord the veins at top of
are united into two or more small branches, which, communicating ^°^
with the intraspinal veins, join in the skull the inferior cerebellar
veins, or the inferior petrosal sinuses.

The SPINAL CORD (medulla spinalis) is the elongated cylindrical Situation of
part of the cerebro-spinal centre, which is enclosed within the spinal ^ ^°^ '
c^nal. Invested Ijy the membranes before examined, the cord
occupies about two-thirds of the length of the canal, and is much
smaller than the bony case surrounding it.

The extent of the S))inal cord is from the lower margin of the Extent
foramen magnum of the occipital bone to the lower border of the b^ji^w,
first lumbar vertebra, but its termination inferiorly may be a little
higher or lower than that spot. In the embryo before the third and in the
month the cord reaches the whole length of the spinal canal ; ^°^ ^^'
but it gradually recedes as the surrounding bones enlarge faster
than it, until it takes the position it has in the adult. Its length Length,
is usually from sixteen to eighteen inches.

Above, the cord joins the medulla oblongata ; and below it ends inferior

in a small tapering part (conus medullaris), from which the filimi h7the"aduit.

terminale (fig. 197, d) is continued downwards. The lower end of

the conus medullaris is sometimes marked by one or two irregular

swellings.

The size of the spinal cord is much increased where the nerves Two swell-
ings on it.
D.A. N N

646

THE SPINAL CORD AND ITS MEMBRANES.

Anterior
surface, how
known.

Dissection
to see con-
stituents of
cord.

Furrows of
the cord are
anterior

posterior
median,

Fig. 197. — Membranes op the
Spinal Cord laid open, to

SHOW THE lower END OF

THE Cord with the Fildm

Terminale.

a. Dura mater, and h, the
fibrous band fixing it to the
coccyx.

c. Pointed lower end of the
cord (conus medull.-iris).

d. Filum terminale of the
cord.

of the limbs are attached. There are,
therefore, two enlargements on it, viz.,
cervical or brachial, and lumbar or
crural ; the one in the neck reaches
from the first cervical to the first
dorsal vertebra ; the other is smaller,
and is on a level with the eleventh
and twelfth dorsal vertebrae. In the
upper enlargement the greatest thick-
ness is from side to side ; but in
the lower swelling the measurement
from before backwards nearly ec[uals
the transverse.

While the pia mater remains on the
cord, the anterior surface is distin-
guished from the posterior by the cen-
tral fibrous band and by the anterior
spinal ait(^ry ; as well as by the
irregular line of the anterior nerve-
roots, which approach the middle
towards the lower end.

Dissection. For the examination
of the structure the student will re-
quire a piece of fresh cord which has
been hardened in spirit and formalin,
since the cord which is obtained
from the body at this period is not
fitted for the purpose of dissection.
Supposing the pia mater with the
roots of the nerves removed on one
side, the student will be able to
observe the following divisions of
the cord.

Sulci of the cord (fig. 198).
The anterior median fissure occupies
the middle line of the front of the
cord in its whole length, and pene-
trates about one-third of the thickness
of it. It is lined by a fold of the
pia mater, and is deepest towards
the lower end of the cord. White
medullary substance bounds the fis-
sure ; and at the bottom of it the
white fibres are transverse, and are
separated by apertures for blood-
vessels.

Along the back of the cord, also in
the middle line, there is a narrow
groove, from which a process of
the pia mater called the posterior

DIVISIONS OF THE CORD.

547

Each half of the cord between the Tlieconlis

divided iuto

median septum extends forwards nearly to the centre of the
medulla, sei>arating the nervous substance of the right and left
halves. Vessels of the posterior surface of the cord enter in the
septum.

The lateral fun-mo (fig. 198, d) is a shallow groove along the lateral,
line of attachment of the fasciculi of the posterior roots.

Between the posterior median and the lateral grooves another and pos-
slight furrow, the posterior intermediate, may be seen in the upper r^^^iate. ^^
part of the cord (fig. 198, e).

Divisions of the Cord.
median su'ci is divided into two by
the lateral furrow (fig. 198, d) ; the
part in front of that groove and the
posterior roots of the nerves is called
the antero-lateral column (a) ; and the
part behind, the posterior column (6).

The antero - lateral column (fig.
198, a) includes rather more than
two-thirds of the half of the curd,
extending backwards to the posterior
roots of the nerves, and gives attach-
ment to the anterior nerve roots (^•).
This part of the cord is sometimes de-
scribed as consisting of anterior and
lateral columns, the two being sepa-
rated by the anterior roots of the
nerves.

The posterior column (fig. 198, h) is
situate between the lateral furrow (rf),
with the posterior roots of the
nerves, and the posterior median
septum. In the cervical region, the
posterior intermediate sulcus(e) marks
off a small inner portion, which is
named the posterior median column(c) ;
and the remainder is then distin-
guished as the posterior external
column (b).

A narrow central piece, the com-
missure of the cord, unites the halves
between the anterior median fissure
and the posterior median septum.

Composition of the cord (fig. 198). Horizontal sections ofcordcon-
the cord in the cervical, dorsal, and lumbar regions, show more dis- an./whitT^
tinctly its division into halves, with the commissural or connecting >»atter.
piece between them, and the varying proportion of its grey and
white matter in the different parts. The cuts demonstrate the
existence of a mass of grey matter in the interior, which is arranged
in the form of two crescents (one in each half), imited by a cross
piece, and surrounded by white substance.

NN 2

Fig. 198. — A Skction of the
Spinal Cord in the Cervical
Region to show its composi-
tion AND divisions. 1n THE

middle line below is the
Anterior Median Fissure,

AND above are THE POSTERIOR

Median (jroovk and Septum.

The lateral sulcus.

column,

The posterior intermediate

sulci

IS.

Columns :

Antero-lateral.

with median

Posterior external.

and external

Posterior median.
Composition :

parts,

Grey crescent, surrounded

by white fibres.

Grey transverse commissure,

and

i, canal of the cord in it.

Po.sterior, and k. anterior and com-

root of a nerve entering the grey

missure.

crescent.

548

THE SPINAL CORD AND ITS MEMBRANES.

The com-
missure :

the grey
part,

with its
central
canal

lined by
epithelium ;

the white
part.

The half of
cord.

The grey
crescent.

Posterior
cornu :

its parts.

Anterior
cornu.

Inter-

mediate

process.

Wliite
substance.

The commissure consists of two parts, viz., a transverse band of
grey matter (fig. 198, h), with a white stratum in front.

The grey transverse band ( posterior or grey commissure) connects
the ojiposite crescents, and is placed rather nearer tlie front than
the back of the cord. In its centre is the shrunken canal of the
spinal cord (fig. 198, i), which is best seen in the foetus. It
reaches the whole length of the cord, and a cross section shows it
as a round spot. Above, the canal opens on the fioor of the lourth
ventricle ; and below, it is continued into the filuni terminale.
It is lined by a columbar ciliated epithelium, and is obstructed
by a granular material near the upper end.

The anterior or ivhite commissure is best marked opposite the

cervical and lumbar enlargements on
the cord, and is least developed in
the dorsal region.

Lateral half. In the half of the
cord, as in the commissure, grey and
white portions exist ; the former is
elongated from before backwards,
being crescentic in shape, and is
quite surrounded by white matter.
The grey matter (fig. 198 g), has
its extremities or cornua directed
towards the roots of the nerves,
and the convexity to the middle
line. The crescentic masses in the
opposite halves of the cord are
united by the grey commissure.

Taking a cross section of the
dorsal region as an example : the
posterior cornu is long and slender
(fig. 199), and reaches nearly to
the surface along the lateral fissure.
It is rather narrow at its base {cervix, '), and enlarged towards its
extremity (caput, '), where it is surmounted by a semi-transparent
layer which has been named the substantia gelatinosa (a). There is
also on the inner side of the cervix of the posterior cornu a special
portion of grey matter containing nerve-cells, the posterior vesicular
column of Clarke (^), which is most developed in the lower dorsal
region.

The anterior cornu (fig. 199) is shorter and thicker than the
posterior, and projects towaids the anterior roots without reaching
the surface. Its end has an irregular or zigzag outline.

A third smaller projection of the grey matter is seen in the upper
part of tlie dorsal region of the cord, on the outer side of the crescent,
between the anterior and posterior horns : this is known as the
intermediate process (Gowers) or the lateral cornu (fig. 199.)

The white substance of the cord is composed chiefly of meduUated
nerve-fibres disposed in longitudinal bundles, which are enclosed by
irregular septa of connective tissue prolonged from the pia mater on

Fig.

199. — Outline of the Grey
Substance in the Spinal
Cord, near the Middle op
the Dorsal Region (Lock-
hart Clarke).

Caput cornu posteiioris.
Anterior cornu.
Substantia gelatinosa.
Central canal of the cord.
Posterior commissure.
Intermediate process.
Cervix cornu posterioris.
Posterior vesicular column.

INTRASPINAL VESSELS.

549

the surface. Three larger processes of the pia mater extend into
the back of the cord ; these are the posterior median septum already
referred to, and the posterior intermediate septum on each side, seen
only in the cervical region, which passes forwards from the furrow
of the same name, and separates the posterior median and postero-
external columns.

Modijicatimis in the grey and white substance. The white substance Grey and
much exceeds the grey in quantity in the cervical and doi-sal stance vary,
regions ; but it is less abundant in jiroportion to the grey matter
in the lumbar enlargement. The grey substance is least in amount

Fig. 200. — Intraspinal Arteries
IN THE Loins.

a. Branch of a lumbar artei'y.

b. Asceniling, and c, descending
offset.

d. OflTset to the body of the
vertebra on each side.

e. Central artery formed by offsets
from the lateral loops.

Fig. 201. — Intraspinal Veins
IN the Loins.

a. Branch to join a lumbar
vein.

b. Anterior longitudinal vein,
one on each side.

c. Veins from the bodies of
the vertebrae.

in the dorsal region ; the anterior horn is specially large in the
cervical region, and in the lumbar enlargement both horns are
large and the grey matter forms a considerable proportion of the
substance of the cord. The posterior born is massive, though not
quite so large as the anterior.

The coinua of the grey crescents decrease in length from above
down, especially the posterior, and towards the end of the cord they
blend in one indented or cruciform mass.

I^:TRASPIXAL Vessels. Arteries supply the cord and its mem-
branes, and the l)odies of the vertebrae. The veins form a remark-
aide plexus within the canal, but this will not be seen unless they
have been specially injected.

The intraspinal arteries (fig. 200, a) are derived from the vessels
along the sides and front of the spinal column, viz., from the
vertebral and ascending cervical in the neck, from the intercostal in

Crescents
alter their
shape.

Vessels of
the spinal
canal.

Source of
the intra-
spinal
arteries.

550 DISSECTION OF THE FACE.

the Lack, and from the lumhar and lateral sacral below. They are

distributed after the following plan : —

pistribution ^^ g^(,}^ artery enters the spinal canal by the intervertebral fora-

to the verte- . "^ ^ •'

bra men, it divides into two branches, upper and lower. From the

point of division the branches are directed, one (h) upwards and
the other (c) downwards, behind the bodies of the two contiguous
vertebrae, and join in anastomotic loops with an offset of the intra-
by loops : spinal artery above and below. From the loops offsets (d) are
furnished to the periosteum and to the bodies of the vertebrae.
Anastomotic twigs connect the arches across the vertebrae,
and a cen- The intraspinal vessels produce also a central longitudinal

ra \esse . g^p^g^y ^^^^ jj]^g ^j^g^^. qj^ ^^le front of the spinal cord, which lies on the
bodies of the vertebrae, and is reinforced at intervals by offsets from
the loops.
Intraspinal The mtraspinal veins (fig. 201) consist of two anterior longitu-
Tar^e.^^^ dinal vessels, which extend the whole length of the spinal canal ;
of veins inside the bodies of the vertebrae ; and of a plexus of veins
beneath the neural arches.
Anterior The anterior longitudinal veins (b) are close to the l)odies of the

areon bod^s vertebrae, one on each side of the posterior common ligament ; and
of vertebrae, they are irregular in outline, owing to certain constrictions near the
intervertebral foramina. They receive, opposite the body of each
vertebra the veins (c) from that bone ; and through the interverte-
bral foramina they have branches of communication (a) with the
veins outside the spine in the neck, the dorsal region, the loin's and
the pelvis.
Veins of the Veins of the bodies of the vertehroi. Within the channels in the

YGrtcbrsp

bodies of the vertebrae are large veins, which join on the front of

the bone with veins in that situation. Towards the back of the

vertebra they are united in an arch, from which two trunks issue

by the large apertures on the posterior surface. Escaped from the

bone, the trunks diverge to the right and left, and open into the

longitudinal veins.

'^°iimi veins ^^^^ 'posterior spinal veins form a plexus between the dura mater

are in con- and the arches of the vertebrae. A large vein may be said to lie on

arches!^^^ each side of the middle line, which joins freely with its fellow,

and with the anterior longitudinal vein by lateral branches. Offsets

from these vessels are directed through the intervertebral foramina,

to end in the veins («) at the roots of the transverse processes.

Section V.

DISSECTION OF THE FACE.

Directions. After the dissections of the perineum and of the

back have been completed, the body will be turned on to the back

and will remain in that position.

First dissect The worker on the head and neck will first dissect the face,
face. '

MUSCLES OF THE NOSE. 551

because it is most desirable to have it as fresh as possible. This
will usually take two days, and he will then proceed with the
triangles of the neck, and it is important that he shall have
examined the brachial plexus, and worked up to page 599 at least,
in order that the dissector of the upper limb may be free to remove
his part at the end of the sixth day after turning the body.

Position. The head is to be placed so that the side of the face
being dissected is upwards, as far as the times of the students on
the two sides will allow, and it is to be fixed in this position with
hooks.

Dissection. It is not easy to make a good dissection of the Dissection,
muscle-:, nerves and vessels of the face on one side, and the
students are advised to arrange together to make out the muscles Muscles and
and nerves on the one side and the muscles and vessels on the other. sSJr' °°^
At the same time a good dissector can display them all on the muscles and
same side. As a preparatory step, the muscular fibres of the other,
apertures may be made slightly tense by inserting a small quantity
of tow or cotton wool between the eyelids and the eyeball, and
between the lips and the teeth, and within the cheek.

First lay bare the orbicularis palpebrarum muscle by making a How to
skin-deep incision round the margin of the orbit, and raising the ^fn from
skin of the lids towards the aperture of the eye (fig. 203, p. 553). eyelids
Much care must be taken in detaching the skin from the thin and
pale fibres of the orbicular muscle in the lids, as there is but little
areolar tissue between the two.

Next the integument is to be removed from the side of the face from the

. - ? . face

by one incision in front of the ear from above the zygomatic arch '

prolonging down the incision already made in the scalp to the angle

of the jaw, and another along the lower border of the jaw to the

chin : a cut should also l^e made along the free margin of each lip

from the centre to the angle of the mouth, and another round

the edge of the nostril. The flap of skin is to be raised from

behind forwards, and left adherent along the middle line.

On the side of the nose the skin is closely united to the subjacent and from
parts, and must be detached with caution. Around the mouth are
the orbicular muscular fibres of the lips, and from this many fleshy
slips extend both upwards and downwards, but they are all marked to clean
distinctly enough to escape injury, with the exception of the small around
risorius muscle which goes from the corner of the mouth towards ™o"th.
the ramus of the lower jaw. While removing the fat from the
muscles, each fleshy slip may be tightened with hooks.

The facial vessels and their branches will come into view as the Facial
muscles are cleaned (fig. 204, p. 558); the branches of the facial ^^^^^ ^'
nerve will be seen passing forwards from the parotid gland (fig. 205,
p. 562). Over the lower part of the parotid gland, near the angle
of the jaw, the facial branches of the great auricular nerve will be
found.

In front of the ear is the parotid gland, and its duct (which is on and parotid
a level with the meatus auditorius, and pierces the middle of the ^^^^'
cheek) will be traced forwards.

552

DISSECTION OF THE FACE.

In the face
the muscles
form three
groups.

Muscles of
nose.

Pyramidalis
nasi:

Compressor
naris :

Common
elevator of
wing of
nose and
upper lip :

Dilator of
nostril :

Muscles of the Face (fig. 203). The superficial muscles
of the face are disposed in three groups : one of the nose, another
of the eyelids and eijebrow, and a third of the aperture of the mouth.
One of the muscles of mastication, viz., the masse ter, is partly
displayed at the hinder part of the face covering the ramus of
the lower jaw.

Muscles of the Nose (fig. 202). These muscles are the
following: pyramidalis nasi, compressor naris, levator labii
superioris alseque nasi, dilator naris, and depressor alse nasi.

The PYRAMIDALIS NASI (fig. 202 -), is a small fieshy slip that covers
the nasal bone, and appears to be a continuation of the innermost
part of the frontalis muscle. Its fibres are
attached above to the skin of the forehead ;
below, they end in the aponeurosis of the
compressor muscles over the cartilaginous
part of the nose. Its inner border meets
the muscle of the opposite side.

Action. This muscle draws dow^n the
skin of the centre of the forehead, and
produces transverse wrinkles at the root
of the nose.

Compressor naris. This muscle (fig.
202^) is not well seen till after the exami-
nation of the following one, by which it
is partly concealed. Triangular in shape, it
arises by its apex from the upper maxillary
bone near the anterior nasal aperture. The
fibres are directed inwards, spreading out
at the same time, and end in an aponeu-
rosis, which covers the cartilaginous part of
the nose, and is continued into the opposite
muscle.

Action. It stretches the skin over the
cartilaginous part of the nose, and depresses
the tip of the organ.

The LEVATOR labii superioris ALiEQUE

NASI (fig. 202 \ and fig. 203) is placed by
the side of the nose, and arises from the
nasal process of the ujjper maxillary bone,
in front of the attachment of the orbicularis. The fibres pass down-
wards, and the most internal are attached by a narrow slip to the
ala of the nose, while the rest are inserted into the adjoining part
of tlie skin of the upper lip. Near its origin the muscle is partly
concealed by the orbicularis palpebrarum, but in the rest of its
extent it is subcutaneous. Its outer border joins the elevator of
the upper lip.

Action. This muscle raises the upper lip and' wing of the nose,
forming wrinkles in the overlying skin.

Dilatator naris. In the dense tissue on the outer side of the
nostril are a few muscular fibres, both at the fore and back part of

Fig. 202.— Muscles op
THE Nose

1. Pyramidalis nasi.

2. Common elevator of
the nose and lip.

3. Compressor naris.
4 and 5. The two slips

of the dilatator naris.

6. Depressor alas nasi.

7. Naso-labial slip of
orbicularis oris.

MUSCLES OF THE EYELIDS.

553

that aperture (fig. 202), to which the above name has been

given : they are seldom visible without a lens. The anterior slip anterior and

(^) passes from the cartilage of the aperture to the integument of

the margin of the nostril ; and the posterior (^) arising from the {'^^JT'^''

ujiper jawbone and the small quadrate cartilages, ends also in the

integuments of the nostril.

Acti(m. The fibres enlarge the nasal opening by raising and use.
everting the outer edge.

The DEPRESSOR AL^ NASI (fig. 202 ^) will be seen if the upper Depressor
lip is everted, and the mucous membrane is removed by the side of ° ^"^ '
the frsenum of the lip. It arises below the nose from the incisor
fossa of the superior maxilla, and ascends to be inserted into the
septum narium and the posterior part of the ala of the nose.

Orbicularis palpebrarum
(palpebral portion).

Orbicularis palpebrarum
(orbital portion).

Corrugator supercilii

Internal tarsal ligament.

PjTamidalis nasi.

Levator labii superioris
alaeque nasi.

Levator labii superioris
Levator anguli oris.

Depressor labii inferioris.
Depressor angnli oris.

Attolens aurem.
Attrahens aurem.

Masseter (deep part).

Zygomaticus minor

(too large).
Zygomaticus major.

Masseter (superficial
parts ; some cut away).

Buccinator.
Fig. 203. — Diagram of the Muscles of the Face.

Action. By drawing down and turning in the edge of the
dilated nostril, it restores the aperture to its usual size.

Muscles of the Eyelids. The muscles of the eyelids and eye-
brow are four in numljer, viz., orbicularis palpebrarum, corrugator
supercilii, levator palpebrse superioris. and tensor tarsi "■' : the two
latter are dissected in the orbit, and will be then described.

The ORBICULARIS PALPEBRARUM (fig. 203) is the sphincter
muscle closing the opening between the eyelids. It is a flat and
thin layer, which extends from the margin of the lids beyond the
circumference of the orbit. From a diflerence in the characters of
the fibres, a division has been made of them into two parts — outer, two parts
or orbital, and inner, or palpebral.

Four

muscles of
eyelids and
brow.

Orbicularis
I)ali)ebra-
rum :

* The tensor tarsi muscle is sometimes described as part of the orbicularis.

554

DISSECTION OF THE FACE

Orbital or
external,

attached
internally

forms con-
centric
bundles.

Internal or

palpebral

part.

attached at
both ends.

Ciliary
bundle.

Relations.

Use of inner
and

outer fibres.

CorriTfi^tor
supercilli

inserted into
skin:

Muscles of
the mouth.

The orbital fibres are the best marked, and are fixed only at the
inner side of the orbit. Above the internal tarsal ligament (which
is the short fibrous band at the junction between the two eyelids,
stretching from the palpebral fissure to the inner margin of the
orbit) the fibres are attached to the nasal process of the superior
maxillary and to the internal angular process of the frontal bone ;
and, below the ligament, to the orbital margin of the superior
maxillary bone. From this origin the fibres are directed outwards,
giving rise to ovals, which lie side by side, and increase in size
towards the outer edge of the muscle, where they project beyond
the margin of the orbit. Some of the peripheral fibres spread
upwards to the skin of the forehead, and others downwards to that
of the cheek.

The palpebral fibres, paler and finer than the orbital, occupy the
eyelids, and are fixed at both the outer and inner sides of the orbit.
Internally they arise from the upper and lower margins of the internal
tarsal ligament : externally they end in the much smaller external
tarsal ligament, by means of which they are attached to the malar
bone, and a few may blend with the orbital part of the muscle.
Close to the cilia, or eyelashes, the fibres form a small pale bundle,
which is sometimes called the ciliary bundle.

The muscle is subcutaneous : and its circumference is blended
above with the frontalis. Beneath the upper half of the orbicularis,
as it lies on the margin of the orbit, is the corrugator supercilii
muscle with the supraorbital vessels and nerve ; and beneath the
lower half is a portion of the elevator of the upper lip. The outer
fibres are joined occasionally by slips to other contiguous muscles
below the orbit.

Action. The palpebral fibres cause the lids to approach each
other, shutting the eye ; and in forced contraction the outer com-
missure is drawn inwards. In closing the eye the lids move
unequally — the upper being much depressed, and the lower slightly
elevated and moved horizontally inwards.

When the orbital fibres contract, the eyebrow is depressed, and
the skin over the edge of the orbit is raised around and brought
inwards in front of the eye, so as to protect the ball. Elevation of
the upper lip accompanies contraction of the outer part of the
orbicularis, owing to the associated action of the levator labii
superioris and zygomatic muscles.

The CORRUGATOR SUPERCILII (fig. 203) is beneath the orbicularis,
near the inner angle of the orbit. Its fibres arise from the inner
part of the superciliary ridge of the frontal bone, and are directed
outwards between the bundles of the orbicularis to be inserted into
the skin above the inner half of the eyebrow. It is a short muscle,
and is distinguished by the closeness of its fibres.

Action. It draws inwards and downwards the mid-part of the
eyebrow, wrinkling vertically the skin near the nose, and stretching
that outside its jjlace of insertion.

Muscles of the Mouth (fig. 203). Tne muscles of the mouth
and lips include the elevators of the upper lip and of the angle of the

MUSCLES OF THE MOUTH.

555

Clinical
Urinology

By ALFRED C. CROFTAN,

professor of Medid-e. Chicago Post-GraduaW
Mtdical College and HospiUl, etc, etc.

This book is a treatise on the tjnnary
aspect of disease. It is not merely a labora-
tory guide tr^ the analysis of unne, nor
is it a purel-y clinical disquisition on the dis-
orders th=,t produce urinary -"nonnato^^
Its purrJose is to describe the borderland
that lUs between the laboratory and the
clinif*.

le of the moutli,
;cle of the cheek
)r). Lastly, an
rgelj composed

cally from the Elevator of
T. • £ upper lip:

It arises from

and from the

into the skin
the orbicularis.
)icularis palpe-
y^ its inner side relations :
nd upper lip ;
the small one
id nerve.

lip is raised, use.

levator of the P^'P'^tft^''^

_ lower jftw .
s fibres. The

e front of the

tie beyond the

the skin of the

le of the oppo-

r anguli oris.

ip of the same use

1 muscles, the

iered tense at

and is partly Elevator of

, , . the angle

om the canine

len, its fibres

2 superficial to

ut the greater enters orbi-

f culans :

ip, and sweep

Idle line.

nth, and acts use.

Octavo, 3U P^ges. illustrated by en-
and a colored plate. Extra muslin,

gravings
I $2.50, net.

Wm. Wood & Co.

51 FIFTH AVENUE,

NEW YORK.

It arises from Depressor
J . of angle

md ascending

inserted into

those of the also joins

J orbicularis:
Dicularis, and

.f the middle

the inferior
in with the
ius muscle.

rds bv it, as use.

11 the malar Zygomatic
,. /-^ • muscles,

lip. One is

654

DISSECTION OF THE FACE

Orbital or
external,

attached
internally

forms con-
centric
bundles.

Internal or

palpebral

part.

attached at
both ends.

Ciliary-
bundle.

Relations.

The orbital fibres
inner side of the or
is the short fibrouf
stretching from th
orbit) the fibres ar
maxillary and to t
and, below the li
maxillary bone,
giving rise to ov;
towards the outei
the margin of th
upwards to the sk
of the cheek.

The palpebral fi
eyelids, and are fi
Internally they ar
tarsal ligament :
tarsal ligament, 1
bone, and a few
Close to the cilia
which is sometin
The muscle if
above with the fi
as it lies on th(
muscle with the
lower half is a j
fibres are joined
below the orbit.
Action. The
other, shutting
missure is dra\
unequally — the
elevated and m
oixter fibres. When the 0
the skin over t
inwards in fror
the upper lip
orbicularis, o\\
superioris and
The CORRUG
near the inner
part of the su]
outwards betv
the skin above
and is distingi
Action. Ii
eyebrow, wrir
that outside i
Muscles (
and lips inch

Use of inner
aTid

Corruojator
supercilli

inserted into
skin :

Muscles of
the mouth.

MUSCLES OF THE MOUTH. 555

mouth, the depressors of the lower lip and of the angle of the mouth,
the zygomatic and risorius muscles, and a wide muscle of the cheek
closing the space between the jaws (the buccinator). Lastly, an
orbicular muscle surrounds the opening, but it is largely composed
of fibres of the preceding muscles.

The LEVATOR LABii suPERioRis extends vertically from the Elevator of
lower margin of the orbit to the orbicularis oris. It arises from
the upper maxilla above the infraorbital foramen and from the
innermost part of the malar bone, and is inserted into the skin
of the upper lip, its fibres interlacing with those of the orbicularis.
Near the orbit the muscle is overlapped by the orbicularis palpe-
l>rarum, but below that spot it is subcutaneous. By its inner side relations :
it joins the common elevator of the ala of the nose and upper lip ;
and to its outer side lie the zygomatic muscles, the small one
joining it. Beneath it are the infraorbital vessels and nerve.

Action. By the action of this muscle the upper lip is raised, use.
and the skin of the cheek is bulged below the eye.

The DEPRESSOR LABII iNFERiORis is opposite the elevator of the pppj-essor of

lower iJiw I

upper lip, and has much yellow fat mixed with its fibres. The
muscle has a wide origin from a depression on the front of the
lower jaw, reaching from near the symphysis to a little beyond the
mental foramen ; ascending thence it is inserted into the skin of the
lower lip. Its inner border joins in the lip the muscle of the oppo-
site side ; and its outer is overlapped by the depressor anguli oris.

Action. If one muscle contracts, the half of the lip of the same ase
side is depressed and everted ; but by the use of both muscles, the
whole lip is lowered and turned outwards, and rendered tense at
the centre.

The LEVATOR ANGULI ORIS has well-marked fibres, and is partly Elevator of
concealed by the levator labii superioris. Arising from the canine ^ *"^ ^
fossa of the upper jaw below the infraorbital foramen, its fibres
descend towards the angle of the mouth, w^here they are superficial to
the buccinator and are partly inseiied into the skin, but the greater enters orbi-
number are continued into the orbicularis of the lower lip, and sw^eep
round below the mouth to the opposite side of the middle line.

Action. This muscle elevates the corner of the mouth, and acts «se,
as an antagonist to the depressor.

The DEPRESSOR ANGULI ORIS is triangular in shape. It arises from Depressor
the oblique line on the outer surface of the lower jaw ; and ascending °
to the angle of the mouth, a few of its fibres are there inserted into
the skin, but the greater number decussate with those of the also joins

orbicularis '

elevator muscle and pass into the upper part of the orbicularis, and
sweep round above the mouth to the opposite side of the middle
line. The depressor conceals the mental branches of the inferior
dental vessels and nerve. It is united at its origin with the
platysma myoides, and near its insertion with the risorius muscle.

Action. The angle of the mouth is drawn downwards by it, as use.
is exemplified in a sorrowful countenance.

The ZYGOMATIC MUSCLES are directed obliquely from the malar Zygomatic
bone towards the angle of the mouth and the upper lip. One is '"""^^ ^^'

656

DISSECTION OF THE FACE.

large and

small:

Risorius
muscle :

Uuccinator
muscle :

origin

insertion at
corner of
the mouth ;

parts in con-
tact with it :

use on
apeiture,

on cheek,

in expelling
air.

Orbicular
muscle of
lips includes
fibres of
buccinator.

longer and larger than the other ; they are therefore named niajcn-
and minor.

The zygomaticus major arises from the outer part of the malar
bone, and is inserted into the skin and mucous membrane at the
angle of the mouth.

The zygoviaticus minor arises from the malar bone in front of
the major, and blends with the elevator of the upper lip. This
muscle is often absent.

Action. The large muscle draws upwards and backwards the
corner of the mouth, as in laughing ; and the small one assists the
levator labii superioris in raising the upper lip.

The RISORIUS MUSCLE (fig. 185, p. 501) is a thin bundle of
fibres, sometimes divided into two or more parts, which arises
externally from the fascia over the masseter muscle, and is connected
internally with the apex of the depressor angidi oris.

Action. It retracts the corner of the mouth in smiling.

The BUCCINATOR ( fig. 203) is the flat and thin muscle of the
cheek, and occupies the interval between the jaws. It arises from
the outer surface of the alveolar l)orders of the upper and lower
maxillae, as far forwards in each as the first molar tooth ; and in
the interval between the jaws behind it is attached to a tendinous
band known as the pterygo-maxillary ligament. From this origin
the fibres are directed forwards to the lips, where they pass into the
orbicularis ; most of the upper fibres descend to the lower lip
while many lower ones ascend to the upper lip, a decussation taking
place at the corner of the mouth. The highest and lowest fibres
enter the corresponding lip.

On the cutaneous surface of the buccinator are the diff"erent
muscles converging to the angle of tlie mouth ; and crossing the
upper part is the duct of the parotid gland, which perforates the
muscle opposite the sec(md upper molar tooth. Internally the
muscle is lined by the mucous membrane of the mouth, and ex-
ternally it is covered by a fascia (bucco-pharyngeal) that is con-
tinued over the pharynx behind. By its intermaxillary origin
the buccinator corresponds with the attachment of the superior
constrictor of the i3harynx.

Action. By one muscle the corner of the mouth is retracted, and
by the action of both the aperture of the mouth is widened trans-
versely.

In mastication the cheek is pressed against the arches of the
teeth and food cannot accumulate in the interval, while the corner
of the mouth is fixed by the orbicularis.

In the expulsion of air from the month, as in whistling, the
muscle is contracted so as to prevent bulging of the cheek ; but in
the use of a blow-pipe it is stretched over the volume of air
contained in the mouth, and maintains a continuous stream by its
contraction during expiration.

The ORBICULARIS ORIS is mainly formed by the prolongation of
the fibres of the levator and depressor angulis oris and buccinator
muscles. The buccinator fibres lie next to the mucous membrane,

THE ORBICULARIS ORIS. 557

and are continued across from side to side. Those of the elevator levator and
and depressor muscles, having crossed at the corner of the mouth, angSroris,
turn inwards in the opposite lip, in front of the buccinator fibres,
and are inserted into the skin, for tlje most part crossing the middle
line and decussating with the fibres entering on the other side. A
compact superficial fasciculus at the red margin of the lip is formed
solely by buccinator fibres. In the upper lip there are also two
slips arising, the one (imso-lahialj fig. 202) from the hinder part of naso-labial
the septum narium, the other (incisive) from the outer part of the and incisive
incisor fossa of the superior maxilla, and directed outwards to the ^^^^^'
corner of the mouth ; while in the lower lip there is a similar
incisive slip attached to the incisor fossa of the inferior maxilla. To
see these attachments, the lij^ must be everted and the mucous
membrane carefully raised.

Towards tlie free margin in each lip there are fibres directed ob- Special
liquely from the skin to the mucous membrane, between the fasciculi f^^^
of the orbicularis : they constitute the muse, labii propi'ius.

The inner margin of the orbicularis is free, and bounds the Relation of
aperture of the mouth ; the outer edge blends with the different '

muscles that elevate or depress the lips and the angle of the mouth.
Between the orbicularis and the mucous membrane in each lip are
the coronary artery and the labial glands.

Action. The buccal portion of the muscle flattens the lips and use.
against the teeth, turns inwards the red margin, and gives a linear
form to the aperture. The superficial portion, derived from the
muscles of the angle of the mouth, brings the lips together both
vertically and horizontally, so as to diminish the size of the opening,
and causes the free edges of the lips to protrude.

The LEVATOR MEXTi (levator labii inferioris) is a small muscle Elevator of
on the side of the fraenum of the lower lip, which is opposite the ^^^" *
depressor of the ala of the nose in the upper lip. When the lip
has been everted and the mucous membrane removed, the muscle
will be seen to arise from the incissor fossa of the lower jaw, and
to descend to its insertion into the integument of the chin. Its
position is internal to the depressor of the lip and the attachment
of the orbicularis.

Action. It indents the skin of the chin opposite its insertion, use.
and assists in raising the lower lip.

The principal Vessels of the Face (fig. 204) are the facial and Arteries of
transverse facial arteries with their accompanying veins. The
arteries are branches of the external carotid ; and the facial vein is
received into the internal jugular trunk.

The FACIAL ARTERY (fig. 204, g), a branch of the carotid. Facial
emerges from the neck, and crosses the base of the lower jaw * ^"
immediately in front of the masseter muscle. From this point the
artery ascends in a tortuous manner, near the angle of the mouth
and the side of the nose, to the inner margin of the orbit, where it
anastomoses with the terminal branches of the ophthalmic artery, com-se
The course of the vessel is comparatively superficial in the mass of
fat of the inner part of the cheek. At first it is concealed by the

558

DISSECTION OF THE FACE.

and rela-
tions;

platysma while crossingthe jaw, but this thin muscle does not prevent
pulsation being recognised during life ; near the mouth the large
zygomatic muscle is superficial to it. The vessel rests successively
on the lower jaw, the buccinator muscle, the elevator of the angle

Fig. 204.-

-ExTERNAL Carotid and its Superficial Branches
("Anatomy of the Arteries," Quain).

a. Common carotid.

h. Internal jugular vein.

c. Internal carotid.

d. External carotid.

e. Superior thyroid.
/, Lingual.

g. Facial.

h. Internal maxillary.

i. Superficial temporal.

m. Supraorbital.

n. External nasal.

0. Angular branch of facial

p. Lateral nasal.

r. Superior coronary.

s. Inferior coronary.

t. Inferior labial.

u. Submental artery.

plan of the
bi-anches.

of the mouth, and the elevator of the upper lip. Accompanying the
artery is the facial vein, which takes nearly a straight course, and
lies to its outer side.

Branches. From the outer side of the vessel unnamed branches
are furnished to the muscles and integuments, some of which

VESSELS OF THE FACE. 559

anastomose with the transverse facial branch of the superficial temporal
artery. From the inner side are given the following branches : —

The inferior labial branch (t) runs inwards beneath the depressor inferior
anguli oris muscle, and is distributed between the lower lip and * *^''
chin ; it communicates with the inferior coronary, and with the
mental branch of the inferior dental artery.

Coronary branches {r and s). These are one for each lip (superior Two
and inferior), which arise together or separately from the facial, foJ^^an"
and are directed inwards between the orbicular muscle and the ^^^^ *?
mucous membrane of the lip to inosculate with the corresponding
branches of the oppo^«ite side. From the arterial arches thus
formed offsets are supplied to the structures of the lip. From the
arch in the upper lip a branch is given to each side of the septum branch to
narium, — artery of the septum. septum.

The lateral nasal branch (p) arises opposite the ala nasi, and Lateral
passes beneath the levator labii superioris alaeque nasi to the side branch,
of the nose, where it anastomoses with the nasal branch of the
ophthalmic artery.

The angular branch (o) is the terminal twig of the facial artery at ^°^^^''
the inner angle of the orbit, and joins the nasal branch of the
ophthalmic artery.

The FACIAL VEIN commences at the root of the nose in a vein Facial vein
named the angular. It then crosses over the elevator of the
upper lip, and, separating from the artery, courses beneath the large away from
zygomatic muscle to the side of the jaw. Afterwards it has a short * ^ '
course in the neck to join the internal jugular vein.

Tributaries. At the inner side of the orbit the angular vein joined by-
receives veins from the upper eyelid [superior palpebral) and from
the side of the nose. Below the orbit it is joined by veins
from the lower eyelid (inferior palpebral), as well as by a large
branch, anterior internal maxillary or deep facial vein, that comes
from a plexus in the pterygoid region, and thence on to its
termination by veins corresponding with the branches of the artery
in the face and neck.

The TRANSVERSE FACIAL ARTERY (fig. 204) Is a branch of the Transverse

superficial temporal, and appears on the face at the anterior border facial artery,
of the parotid gland. It lies by the side of the parotid duct,
with branches of the facial nerve, and distributes offsets to the
muscles and integuments ; some branches anastomose with the
facial artery.

Dissection. The parotid gland in front of the ear may be next Lay bare
displayed. A strong fascia covers the gland, and is connected Sand^™^^^
above to the zygomatic arch and behind to the cartilage of the pa^otid
ear, but is continued in front over the masseter muscle. The fascia is fascia,
to be removed, so that the gland may be detached slightly from the
parts around. The great auricular nerve will be seen ascending to
the lobule of the ear ; and three or four small lymphatic glands Parotid
rest on the surface of the gland. gWs?"*"

The Parotid fig. 213, i", p. 589) is the largest of the salivary Parotid
glands. It occupies the space between the ear and the lower jaw, gland:

560

DISSECTION OF THE FACE.

irregular in
shape ;

relations ;

accessory
l>art.

The duct
reaches
mouth :

surface
markinf

its length
and size.

Surface of
gland.

Dissection
to see deep
parts.

Deep part
sinks behind
jaw.

Vessels and

and is named from its position. Its excretory duct enters the
mouth through the niiddle of the cheek.

The shape of the gland is irregular, and is determined hy the
surrounding parts. Thus below, where there is not any resisting
structure, the parotid projects into the neck, and comes into close
proximity with the submaxillary gland, though separated from it by
a process of the cervical fascia ; a horizontal line from the angle of
the jaw to the sterno-mastoid muscle usually marks the extent of
the gland in this direction. Superiorly, the parotid is limited by the
zygomatic arch and the temporal bone. Along the posterior part
the sterno-mastoid muscle extends ; but anteriorly, the gland projects
somewhat into the face over the masseter muscle, and has connected
with it in this situation a small accessory part, known as the socia
parotidis.

Issuing from the anterior liorder is the excretory duct — duct of
Stenson (fig. 204), which crosses the masseter below the socia
parotidis, and perforates the buccinator and the mucous mem-
brane of the cheek obliquely opposite the second molar tooth of
the upper jaw. The duct lies between the transverse facial
artery and some branches of the facial nerve, the latter being
below it. A line drawn from the meatus auditorius to a little
below the nostril would mark the level of the duct on the face ;
and the central point of the line would be opposite the opening
into the mouth. The length of the duct is about two inches and
a half ; and its capacity is large enough to allow a small probe to
pass, but the opening into the mouth is much less.

The cutaneous surface of the parotid is smooth, and three or four
lymphatic glands are seated on it : but from the deep part processes
are sent into the inequalities of the space between the jaw and the
mastoid process.

Dissection. By removing the parotid gland, cautiously and piece-
meal, from behind and below, the hollows that it fills will come
into view : at the same time the dissector will see the vessels and
nerves that pass through it. An examination of the jDrocesses of
the gland, and of the number of important vessels and nerves in
relation with it, will demonstrate the dangers attending any opera-
tion on it. The duct may be opened, and a pin may be passed
along it to the mouth, to show the position and the diminished size
of the aperture.

Two large processes of the gland extend deeply into the neck.
One dips behind the styloid process, and projects beneath the
mastoid process and sterno-mastoid muscle, where it reaches the
deep vessels and nerves of the neck. The other piece is situate in
front of the styloid process ; it passes into the glenoid hollow behind
the articulation of the lower jaw, and sinks beneath the ramus of
that bone along the internal maxillary artery.

Coursing through the middle of the gland is the external carotid
artery, which ascends behind the ramus of the jaw, and furnishes
the posterior auricular, superficial temporal, and internal maxillary
branches. Superficially to the artery lies the trunk formed by the

THE FACIAL NERVE. 561

junction of tlie temporal and internal maxillary veins; and this
common trunk, receiving some veins from the parotid, divides near
the angle of the jaw into two branches, the anterior of which passes
downwards to join the facial vein, while the posterior inclines back-
wards over the border of the sterno-mastoid muscle and is continued
into the external jugular vein (fig. 21 1, p. 582). Crossing the vessels nerves in
in the gland from behind forwards is the trunk of the facial nerve,
which dimles here into its primary branches. The superficial
temporal branch of the inferior maxillary nerve lies above the
upper part of the glandular mass ; and offsets of the great auricular
nerve pierce the gland at the lower part, and join the facial.

In dissecting out the gland it has been seen to consist of a Obvious
number of lobules separated by connective tissue septa. From the ^ilnd."'^ °
lobules small ducts arise, and these join together so as to give rise
to two large tubes, which are placed superficially to the branches
of the facial nerve in the gland, and by their union opposite the
hinder margin of the ramus of the jaw form the beginning of
Stenson's duct. As it crosses the masseter the main duct receives
one or more small branches from the socia parotidis.

The parotid receives its arteries from the external carotid ; and Vessels and
its nerves from the sympathetic, auriculo-temporal of the fifth, and '^^'■^'^^•
facial. Its lymphatics join those of the neck.

Two or three small molar glands lie on the surface of the buccina- Molar
tor, and open into the mouth near the last molar teeth by separate ^
ducts.

The FACIAL NERVE (fig. 205, p. 562), or the seventh cranial Outline of
nerve, is the motor nerve of the superficial muscles of the head ^^'* nerve,
and face. Numerous communications take place between it and
the fifth nerve ; the chief of these are found above and below the
orbit, and over the side of the lower jaw.

Dissection. The trunk of the nerve is concealed by the parotid Dissection
gland, but its ramifications are mostly in front of the glandular^
mass, and will be displayed in the removal of the gland.

The different branches are to be traced forwards as they escape beyond
from beneath the anterior border of the gland and followed to ^*^° ^ '
their termination.

The highest branches to the temple have already been partly on temple,
dissected above the zygomatic arch ; and their junction with the
temporal branch of the superior maxillary, and with the supra-
orbital nerve has been seen. Some still smaller branches are to be in eyelids,
traced to the outer part of the orbit, where they enter the eyelids
and communicate with the other palpebral nerves ; as these cross
the malar bone, a junction is to be found with the subcutaneous
malar branch of the fifth nerve.

With the duct of the parotid are two or more large branches, in the face,
which are to be followed below the orbit to their j miction with
the infraorbital, nasal, and infratrochlear nerves.

The reniaining branches to the lower part of the face are on lower
smaller. One runs with the buccal nerve over the lower part of ^*^'
the buccinator muscle ; and one or two others are to be traced

D.A. O O

562

DISSECTION OF THE FACE.

forwards to the lower lip, and to the mental branch of the inferior
dental nerve.
The nerve The trunk of the nerve should he followed l)ackwards through

in the '^

parotid,

Occiiiital artery.

)sterior auricular
rve(brancli of facia

areat occipital nerve.

Facial nerve

Small occipital nerve,
Great auricular nerve.

Frontal aiiery.

Supraorbital arter
Supratrochlear n
Supraorbital ner

Tnfratrochlear ne

- Malar \)ranch o:

poromaliir.

Temporal liranc

temporo-

- Nasal nerv

Infraorl
nerve.

Long buccal m
Mental nerve.

Fig. 205. — Nerves and Arteries of the Scalp.

d. Superficial temporal artery.
/. Posterior auricular artery.
h. Orbital branch of superficial
temporal artery.

14. The superficial cervical nerve.

A. Platysma muscle.

B. Ti-apezius muscle.

c. Sterno-mastoid muscle.

D. Masseter muscle.

The auriculo-temporal nerve is shown running up with the superficial
temporal artery {d).

the gland, and in this proceeding its small branches of communica-
tion with the great auricular nerve, and, deeply, with tbe auriculo-
temporal nerve (of the fifth) are to be sought for.

THE FACIAL NERVE. 563

Lastly, the first small branches of the facial to the back of the and
ear and to the digastric and stylo-hyoid muscles are to be looked branches,
for close to the base of the skull just after the nerve emerges from
the stylomastoid foramen.

The Facial Nerve outside the Skull (fig. 205). The Branches
nerve issues from the stylo-mastoid foramen, after traversing the skulL
aqueduct of Fallopius, and furnishes immediately the three following
small branches : —

The posterior auricular branch (fig. 205) turns upwards in Posterior
front of the mastoid process, where it communicates with an offset branch^
of the great auricular, and is also joined by a branch to the ear
from the pneuino-gastric nerve. It ends in an occipital branch to
the occipitalis and an auricular branch to the retrahens muscle and
to the small muscles on the back of the pinna.

The branch to the digastric muscle arises generally in common Branch to
with the next. It is distributed by several offset-; to the posterior digastric,
belly of the muscle near the skull.

The branch to the stylohyoid is a long slender nerve, which is Branch to
directed inwards, and enters the muscle about its middle. This stylo-hyoid.
branch communicates with the sympathetic nerve on the external
carotid artery.

As soon as the facial nerve has given off these branches, it is Division
directed forwards through the gland, and divides near the ramus of ^"^ *'^^'
the jaw into two large trunks — temporo-facial and cer^ico-facial.

The TEMPORO-FACIAL TRUNK fumishes offsets to the side of the Tlie upper

head and face which extend downwards to the level of the mouth. fj^I'^'f^^,?^
As this trunk crosses over the external carotid artery it receives
one or two large branches from the auriculo-tenlporal portion of the
inferior maxillary nerve, and then divides into three sets of terminal has three
branches — temporal, malar, and infraorbital, w^hich have frequent branches
communications with one another as they pass forwards in the face.

The temporal branches ascend obliquely over the zygomatic arch Temporal
to enter the orbicularis palpebrarum, the corrugator supercilii and ^^"^f^ead
the frontalis muscles ; they are united with offsets of the supra-
orbital nerve. The attrahens and attollens aurem muscles
are supplied from this set ; and a junction takes place aVjove
the zygoma with the temporal branch of the superior maxillary
nerve.

The malar branches are directed to the outer side of the orbit, Malar
and are distributed to the orbicularis muscle. Communications to^e^^eii^ds.
take place in the eyelids with the palpebral filaments of the fifth
nerve and over the malar bone with the small subcutaneous malar
branch of the superior maxillary nerve.

The infraorbital branches are larger than the rest, and are Infraorbital
furnished to the muscles between the eye and mouth. Close to between^eye
the orbit, and beneath the elevator of the upper lip, a free com- ^"d month,
munication — infraorbital plexus, is formed between these nerves
and the infraorbital branches of the superior maxillary. After
crossing the branches of the fifth nerve, some small offsets of
these branches pass inwards to the side of the nose, and others

0 0 2

564

DISSECTION OF THE FACE.

upwards to the inner angle of the orbit to supply the muscles,
and to join the nasal and infractrochlear branches of the ophthalmic
nerve.

The CERVico-FACiAL is smaller than the upper trunk, and distri-
butes nerves to the lower part of the face and the upper part of the
neck. Its highest branches join the lowest offsets of the temporo-
facial division, and thus complete the network on the face. This
trunk, while in the parotid, gives twigs to the gland, and is united
three sets of with the great auricular nerve. The terminal branches distributed
from it are buccal, supramaxillary, and inframaxillary.

The buccal branches pass forwards towards the angle of the
mouth, giving offsets to the buccinator muscle, and terminate in the
orbicularis oris. On the buccinator they join the buccal l)ranch
of the inferior maxillary nerve.

The supramaxillary branches course forwards over the lower jaw
to the middle line, and supply the muscles of the lower lip and
chin. Beneath the depressor anguli oris these branches of the
facial join the offsets of the mental branch of the inferior dental
nerve.

The inframaxillary branch lies below the jaw, and is distributed
to the platysma muscle, and forms communication with sensory
branches from the second and third cervical nerves.

Dissection. The levater labii superioris muscle is now to be
cut through, and the upper part removed so as to expose the
terminal branches of the infraorbital nerve.

The Infraorbital Nerve (fig. 205) is the continuation of the
superior maxillary division of the fifth nerve. It emerges on the
face through the infraorbital foramen under cover of the levator
labii superioris, and at once divides into terminal branches which
radiate to the eyelid, the nose, and the upper lip.

The palpebral branches are usually two small twigs which pass to
the lower eyelid.

The lateral nasal branches are directed inwards, and supply the
skin of the side of the nose.

The labial branches are three or four larger nerves, which,
descending to the upper lip, supplying the skin of the face between
the orbit and the mouth, as well as the mucous membrane of the
upper lip, and their ramifications, take part in the infraorbital
plexus, just described.

Dissection. The depressor labii inferioris and anguli oris
muscles will next be removed so as to expose the mental nerve as it
issues from the foramen in the lower jaw.

The Mental Nerve (fig. 205) is derived from the inferior dental
nerve within the lower jaw, and issues through the mental foramen
beneath the depressor anguli oris muscle. It gives an offset down-
wards to the skin of the chin, but the greater part of the nerve
ascends beneath the depressor labii inferioris muscle, to be dis-
tributed to the inner and outer surfaces of the lower lip. Its
branches conmiunicate with the supramaxillary branches of the
facial nerve.

Lower
division of
the nerve
hfls also

brandies.

Buccal to
corner of
mouth.

iSupra-
maxillary
between
mouth and
chin.

Infra-
maxillary
to neck.

Infra-
orbital
nerve.

Palpebral,

lateral
nasal and

labial
branches

Mental
ner^•e.

THE CARTILAGES OF THE NOSE.

565

EXTERNAL PARTS OF THE NOSE.

Directions. The external parts of the nose, the appendages of
the eye, and the pinna will now be cleaned and examined.

The Nose has the form of a three-sided pyramid, which is
attached to the face by one of its surfaces, while the base is free.
The lateral surftices meet anteriorly in a rounded edge termed the
dorsum, the upper part of which is known also as the bridge. The
lower and posterior part of each lateral surface is convex and
markeil otf by a curved groove, constituting the ala. The base pre-
sents the oval apertures of the nostrils or anterior nares, separated
by a short thick partition, the septum narium or columna nasi.

The shape of the nose is maintained by a framework consisting
of the nasal bones and the nasal processes of the superior maxillary
bones above, and of the cartilages of the
nose below, in the part corresponding to the
anterior nasal aperture of the skull.

Cartilages of the Nose (fig. 206).
These are five in number, one in the centre,
the cartilage of the septum, and two on each
side, the lateral cartilage and the cartilage of
the aperture. They are all hyaline cartilage,
but do not show any tendency to become
ossified. Only the lateral cartilages are
learnt in this stage of the dissection.

Dissection. The lateral cartilages will be
seen when the muscular and fibrous struc-
tures of the left side of the nose have been
taken away. By turning aside the lateral
cartilages the septal one will appear in the
middle line.

The lateral cartilage (upper lat. cart,
fig. 206,^ is flattened, and triangular in
form. Posteriorly it is attached to the nasal
and upper maxillary bones ; and anteriorly
it joins the cartilage of the septum above,

but is separated from it by a narrow cleft below. Inferiorly, the
lateral cartilage is contiguous to the cartilage of the aperture, and
is connected to it by fibrous tissue.

The cartilage of tlie aperture (lower lat. cart. ; fig. 206) forms a ring
around the opening of the nose except behind. It has not any
attachment directly to bone ; but it is united above to the lateral
cartilage by tibrous tissue, and below with the dense teguments
forming the ala of the nose and the margin of the nostril.

The part of the cartilage (^) which bounds the opening externally
is narrow and pointed behind, where it forms two or three vertical
folds, and sometimes becomes divided into as many small pieces —
cartilagines quadrates ; but it swells out in front where it touches its
fellow, and forms the apex of the nose.

The inner part {*) is shorter and narrower. It projects backwards

Extenial
nose: its
parts,

and frame
work.

Nasal
cartilages.

Fig. 206. — Cartit.aqes
of the nosk.

1. Septal cartilage.

2. Lateral cartilage.

3. Caitilages of the
aperature, its outer
part, and 4, its inner
part.

5. Nasal bone.

Take away
tissue from
surface.

The upper
cartilage
joins the
septal.

The lower
surrounds
aperture ;

not inserted
into bone.

One part
outside :

accessory
cartilages ;

another in-
side nostril.

566

DISSECTION OF THE FACE.

in the columiia nasi below the level of the anterior end of the septal
cartilage, being attached to this and to its fellow of the opposite side
by fibrous tissue, and reaches nearly to the superior maxillary bone.

Appendages
of the eye.

Eyebrow.

Eyelids

Upper
larger.

Shape of
margin.

THE APPENDAGES OF THE EYE.

The Appendages of the Eye include the eyebrow, the eyelid,
and the lachrymal apparatus.

The eyebrow (supercilium) is a curved eminence just above the eye
which is placed over the orbital arch of the frontal bone. It consists
of thickened integuments, and its prominence is in part due to the
subjacent orbicularis palpebrarum and corrugator supercilii muscles.
It is furnished with long coarse hairs, which are directed outwards,
and towards one another.

The eyelids (palpebrcne) are two movable semilunar folds in front
of the eye, which can l)e approached or separated over the eyeball.
The upper lid is the larger and more moveable, and descends below
the middle of the eyel)all when the two meet ; it is also provided
with a special muscle to raise it. The interval between the open
lids is named the palpebi'al fissure. Externally and internally they
are united by a commissure or canthus.

The free border of each lid is somewhat thickened, and pre.-ents
a narrow^ surface which meets the opposite lid when the aperture is
closed, and is bounded towards the eyeball by a sharp smooth edge ;
but at the inner end, for about a quarter of an inch from the

Papilla.
Punctum.

Hairs and
apertures.

Eyelashes.

Apparatus
for the
tears.

Dissection.

Apertures
in eyelids.

spot where the two parts join is a small white eminence (fig. 207),
the payilla lachrymalis ; and in this is the pimchim lachrymale, or the
opening of the canal for the tears.

This margin is provided anteriorly with the eyelashes, and near
the posterior edge with a row of small openings of the Meibomian
glands ; but both the cilia and the glands are absent from the part of
the lid which is internal to the opening of the punctum lachrymale.

The eyelashes (cilia) are two or more rows of curved hairs, which
are fixed into the anterior edge of the free border of the lid ; they
are largest in the upper lid, and diminish in length from the centre
to the sides. The cilia of the two lids are convex to one another,
and cross when the lids are shut.

Lachrymal Apparatus (fig. 207). The lachrymal gland, puncta,
canals, and sac, with the nasal duct, constitute the apparatus by
which the tears are formed and conveyed to the nose.

Dissection. A bristle or blunted pin should be introduced into
each lachrymal canal through the punctum. The lachrymal sac
will appear on the removal of the internal tarsal ligament and of the
areolar tissue from its surface as it lies on the lachrymal bone. The
prolongation from the internal tarsal ligament over the sac should
be defined and understood before its removal (p. 568).

The puncta lachrymalia (^), one on each lid, are the openings of
the lachrymal canals. Each is situate on the free margin of the lid,
about a quarter of an inch from the inner canthus, and at the
summit of the papilla lachrymalis.

THE LACHRYMAL APPARATUS. 567

The lachrymal canals (canaliculi ; fig. 207, 'and ^) lead from the Canals for
puncta, and convey the tears to the lachrymal sac. From the *^® *^'^-
margin of the lid, each canal is directed vertically for about one-
sixteenth of an inch, and then bends inwards following the course
of the internal tarsal ligament. Internally the two canals converge,
and they open into the lachrymal sac, rather above its middle,
either separately or by a common orifice.

The lachrymal sac and nasal duct extends from the inner side of Receptacle
the orbit to the nose, and convey the tears into the latter cavity. °^ *^^ ^**"'
They form one tube, of which the upper dilated end is the sac, and
the lower part the duct.

The sac (^) is placed in the hollow formed by the nasal process of Situation of
the superior maxillary and the lachrymal bones. In front, it is diiated'^rt.
crossed by the internal tarsal ligament of the eyelids ; and behind,
it is covered by an expansion
derived from that band, which is
fixed to the lachrymal crest. If
the aponeurotic covering be re-
moved, the mucous lining will
appear. Into the outer side of
the sac the lachrymal canals open.

The duct {^) is the narrower

part of the tube, and is about

half an inch long. It is entirely

surrounded by bone, and inclines

slightly outwards and backwards Fig. 207. — The Eyelids and

as it 'desct-nds. In the nasal Lachrymal AppARATrs.

cavity it opens into the fore part l. Puncta lachrymalia.

of the inferior meatus, where its '2. Upper, and 3, lower lachrymal

opening is guarded by a small ^"^'" , , . ,•

c T 1 ? j^i 1 4. Caruncula lachrymalis. ..

fold of the mucous membrane. 5 Lachrymal sac. openmg.

Within the bone, the duct has o! Nasal duct.^ ' ^^^A'^^'i'^.

' of the duct,

a fibrous coat lined by mucous

membrane, which is continuous with that of the nose l)elow, and,

through the canals, with the conjunctiva above.

Structure of the Eyelids. Each lid consists fundamentally Different
of a filtrous plate attached to the bone by ligaments. Superficial el^ids?
to this framework are the integuments with a layer of fibres of the
orbicularis palpebrarum, and beneath it the mucous lining of the
conjunctiva. The upper lid includes also the tendon of the levator
palpebrse. Vessels and nerves are contained in the lids.

Dissection. The student should now examine the structure of Dissect lids,
the lids. The bit of tow or wool may remain beneath the lids ;
and the palpebral part of the orbicularis muscle is to be thrown
inwards by an incision around the margin of the orbit. In raising
the muscle care must be taken of the thin membranous palpebral
fascia beneath, and of the vessels and nerves of the lid.

Orbicularis palpebrarum. The palpebral fibres of this muscle form Layer of
a pale layer which reaches the free edge of the eyelids, and a thin
stratmn of areolar tissue without fat unites the muscle with the skin.

568

DISSECTION OF THE FACE.

A fibrous
layer.

A fibrous
plate forms
part of the
lid:

difierence in
the two lids.

Ligaments
of eyelids
attach tarsal
plates.

Sebaceous
tubes in lid

their
structure.

Tendon of

levator

palpebrte.

Mucous
lining of lid.

Caruncle

The paljjehral fascia is a thin fibrous layer, which is continued
from the margin of the orbit to join the anterior surface of the
fibrous tarsal plate. At the inner part of the orbit it is thin and
loose, but at the outer part it is somewhat thicker and stronger.

The fibrous lylates (tarsi), one for each eyelid, are elongated
transversely, and give strength to the lids. Each is fixed internally
and externally by fibrous bands — the tarsal or palpebral ligaments^
to the margin of the orbit. The border corresponding with the
edge of the lid is free, and thicker than the rest of the plate. On
the deep surface each tarsus is lined by the conjunctiva.

The tarsi are not alike in the two lids. In the upper eyelid,
where the fibrous plate is larger, it is crescentic in sliape, and is
nearly half an inch wide in the centre ; and to its fore part
the tendon of the levator palpebrse is attached. In the lower
lid the tarsus is a narrow band, about one-sixth of an inch broad,
with nearly straight borders.

The internal tarsal ligament (tendo palpebrarum) is a small
fibrous band at the inner side of the orbit, which serves to fix the
lids, and is attached to the anterior margin of the lachrymal groove
in the upper jaw. It is about a quarter of an inch long, and
divides into two processes, which are united witkthe tarsal plates,
one to each. This ligament crosses the lachrymal sac, behind which
it sends a fibrous expansion ; and the fleshy fibres of the orbicularis
palpebrarum arise from it. The external tarsal ligament is a much
weaker band uniting the tarsi to the malar bone.

The Meibomian or tarsal glands are embedded in the substance of
the tarsal plates, and can be readily seen through the conjunctiva
on the posterior surface of the lids. They extend, parallel to one
another, from the free towards the opposite margin of the tarsus ;
and their numl)er is about thirty in the upper, and twenty in the
lower lid. The apertures of the glands open in a line at the free
border of the lid near the posterior edge.

Each gland is a small yellowish tube, closed at one end, and
having minute lateral csecal appendages connected with it. The
secretion is similar to that of the sebaceous glands of the skin.

If the palpebral fascia be cut through in the upper lid, the tendon
of the levator palpebra will be seen to be inserted into the fore part
of the tarsus by a wide aponeurotic expansion.

The conjunctiva, or mucous membrane, lines the interior of the
lids, from which it is reflected to the front of the eyeball. The
line of reflection is known as the fornix cojijunctivcB, and is placed,
above and below, some distance beyond the convex margin of the
tarsus. Inside the lids the conjunctiva is inseparably united to the
tarsi, and has numerous fine papillae. At the free margin of the
lids it joins the skin, and through the lachrymal canals and nasal
duct it is continuous M'ith the pituitary membrane of the nose.

Between the eyeball and the inner commissure of the lids is
seen a prominent and fleshy-looking body — caruncula lachrymalis
(fig. 207, *), which contains a group of glands, and has a few
minute hairs on its surface. External to the caruncle is a small

APPENDAGES OF THE EYE. 569

vertical fold of the mucous membrane — plica semilunaris, resting and con-
on tlie inner part of the eyeball. iguous o

Blood-vessels of the eyelids. The arteries of the eyelids are Arteries of
furnished l)y the palpebral aud lachrymal branches of the oph- ' ''■
thalmic artery : —

The palpebral arteries, one for each eyelid, run outwards from palpebral
the inner canthus, lying between the tarsal plate and the orbicular
muscle, and anastomose externally with the lachrymal artery. From
each arch branches are distributed to the structures of the lid.

The terminal portion of the lachrymal artery perforates the and lachry-
palpebral fascia at the outer part of the orbit, and, after having °^^^-
given small offsets to the upper eyelid, divides into two branches
which complete the palpebral arches.

The veiris of the lids open into the angular, facial and temporal veins. Veins.

The nerves of the eyelids are supplied from the ophthalmic and Nerves of
superior maxillary divisions of the fifth and the facial nerves. * '''

The branches of the ophthalmic nerve which give offsets to the from fifth,
upper lid are the following : lachrymal, at the outer part ; supra-
orbital, about the middle ; and svpratrochlear and infratrochlear
at the inner side. In the lower eyelid there are usually two
palpebral bi'anches, inner and outer, of the infra-orbital branch of
the superior maxillai-y nerve.

Branches of the facial nerve enter both lids at the outer side, and seventh
and supply the orbicularis muscle ; they communicate with the °®'^^^"
offsets of the fifth nerve.

THE EXTERNAL EAR.

External Ear. The outer ear consists of a broad, projecting Parts ot
part, named the pinna or auricle, and of a tube — meatus auditorius •-'Eternal ear.
externus, leading in^-ards to the middle ear, from which it is separ-
ated by the tympanic membrane. The pinna may be now examined,
but the meatus will be described with the anatomy of the ear.

The PINNA or auricle (fig. 208) is an uneven piece of yellow fibro- Texture and
cartilage, which is covered with integument, and is fixed to the margin p°""a?
of the meatus auditoiius externus. It is of a somewhat oval form,
with the margin folded and the upper end larger than the lower.

The surface next the head is generally convex ; and the opposite Surface
excavated, but presenting the following elevations and depressions, fossie'and^
In the centre is a deep hollow named the concha, w^hicli is wide above eminences.
but narrow l)elow ; it conducts to the meatus auditorius. In front
of the narrowed part of the hollow is a projection of a triangular
shape — the tragus, which has sonie hairs on the inner surface ; and
on the opposite side of the same narrow end, rather below the level
of the tragus, is placed another projection — the antitragus.

The prominent rim-like margin of the ear, which extends into the Margin,
concha, is called the helix; and the depression internal to it is the
groove or fossa of the helix. Within the helix, forming the hinder
and upper boundary of the concha, is the large eminence of the
antihelix, which presents at its up])er and fore-part a triangular
depression, the fossa of the antihelix.

570

DISSECTION OF THE FACE.

Lobule. Inferiorly the auricle ends in a soft pendulous part, the lobule.

Intrinsic The special muscles of the pinna, which extend from one part of

auricle." ° ^^^ cartilage to another, are very thin and pale. Five small muscles
are to be recognised ; and these receive their names for the most
part from the several eminences of the external ear.
How to find Dissection. In seeking the small auricular muscles, let the
the muscles, gj^j^^ y^^ removed only over the spot where each muscle is said to
be placed. A sharp knife and a good light are necessary for the
display of the muscular fibres. Occasionally the dissector will not
find one or more of the number described below.
One muscle The miiscle of the tragus (fig. 208,^) is always found on the
on tragus, external aspect of the process from which it takes its name. The

Fig. 208.

Muscles of the Outer Surface
OF TUB Ear-cartilage.

1. Muscle of the tragus.

2. Muscle of the antitragus.

3. Large muscle of the helix.

4. Small muscle of the helix.

Muscles on the Inner

SUKFACB OF THE EaR-

cartilage.

6. Transverse muscle.

7. Oblique muscle some-
times seen.

One ou
an ti tragus.

One on root
of helix.

Another on
helix.

And one at
back of
concha.

fibres are short, oblique, and extend from the outer to the inner
part of the tragus.

The muscle of the antitragus (fig. 208, '^) is the best marked of all.
It arises from the outer part of the antitragus, and the fibres are
directed upwards to be inserted into the pointed extremity of the
antihelix.

The small mmcle of the Jielix (fig. 208, *) is often indistinct or
absent. It is placed on the part of the rim of the ear that extends
into the concha.

The large muscle of the helix {fig. 208,^) arises above the small
muscle of the same part, and is inserted into the front of the helix,
where this is about to curve backwards. It is usually present.

The transverse muscle of the auricle (fig. 208, ^) forms a wide layer
which is situate at the back of the ear in the depression between
the helix and the convexity of the concha. It arises from the con-
vexity of the cartilage forming the concha, and is inserted into the

AURICLE OF THE EAR. 571

back of the helix. The Diuscle is mixed with much fibrous tissue,
but it i:5 well seen when that tissue is removed.

Dissection. The remaining skin should now be removed from Clean the
the pinna, and the muscles cleaned off to expose the cartilage: in *^*^ ^
doing this the lobule of the ear, which consists only of skin and
fat, will disappear as in fig. 208.

The cartilage of the pinna (fig. 208) resembles much the external Cartilage
ear in form, and presents nearly the same parts. The rim of the of external
helix subsides posteriorly about the middle of the pinna: while ^^^ =
anteriorly a small process projects from it, and there is a fissure
near the projection. The part of the cartilage forming the fossa of
the helix ends on a level with the lowest part of the concha in a deficient

dgIow

pointed process which is separated from the antitragus by a deep
notch. The antihelix is continued l>elow into the antitragus. On
the posterior aspect of the concha is a strong vertical ridge of
cartilage.

Inferiorlv the cartilage is fixed to the margin of the external and at upper

" t)3.rt; of

auditory aperture in the temporal bone, and forms a portion of the meatus;
meatus auditorius ; but it does not give rise to a complete tube, for
at the upper and hinder part that canal is closed by fibrous tissue.

In the piece of cartilage forming the outer end of the meatus its fissures,
are two fissures (of Santorini) : one is directed vertically beneath
the base of the tragus ; the other passes from before backwards in
the floor of the meatus.

Some ligaments connect the pinna with the head, and others pass Ligaments;
from one point to another of the cartilage.

The external ligaments are two bands of fibrous tissue, anterior extrmsic,
and posterior. The anterior fixes the fore part of the helix to the
root of the zygoma. The posterior passes from the back of the
concha to the mastoid process. The chief special ligament crosses intrinsic,
the interval between the tragus and the helix, and completes the
opening of the auditory meatus.

Vessels and nerves of the auricle. The arteries of the auricle
are derived from the superficial temporal {ant. auricular branches)
and the posterior auricular branches of the external carotid. The
veins have a corresjionding termination. The skin of the pinna is
supplied on the outer surface mainly by the auricular-temporal branch
of the inferior maxillary nerve, on the inner surface in the upper
part by the small occipital, and in the lower part, together with
the outer aspect of the lobule, by the great auricular nerve. The
auricular branch of the vagus also reaches the back of the concha.
The muscles are supplied by the posterior auricular branch of the
facial nerve.

572

DISSECTION OF THE NECK.

Section VI.

DISSECTION OF THE NECK.

Boundaries
of the side
of the neck.

Division
into two
triangles
by stern o-
mastoid.

Hollows.

Objects in
middle line
of neck :

Position. For the dissection of this part, the neck is supported
on a block of a moderate height, the chin drawn up so as to pul
the parts on the stretch and the shoukler depressed as much as th(
work that is being done on the axilla will allow, and the fac<
should be turned to the opposite side.

Surface Marking. The side of the neck lias a somewhat irregularly
quadrilateral outline, and is limited in the following way : — Below
is the prominence of the clavicle ; and above is the base of th(
lower jaw with the skull. In front, the boundary is the middh
line of the neck between the chin and sternum ; and behind, a line
from the occiput to the acromial end of the clavicle. The part
thus included is divided into two triangular spaces {anterior anc
'posterior) by the diagonal prominence of the sterno-mastoid muscle
(fig. 209). And in consequence of the position of that muscle the
base of the anterior triangle is at the jaw, and the apex at th(
sternum ; while the base of the posterior one is at the clavicle, and
the apex at the head.

The surface in front of the sterno-mastoid is depressed at th(
upper part of the neck, near the position of the carotid vessels ;
and behind the muscle, just above the clavicle, is another hollow,
the supraclavicular fossa, which indicates the position of tht
subclavian artery.

Along the front of the neck the following parts can be recognised

through the skin : — About two inches and a half from the chin, in
the retiring angle formed by the outline of the front of the neck,
hyoid bone, the body of the hyoid l)one may be felt, with its large cornu
extending l)ackwards on each side. Below this is the promiirence of
the thyroid cartilage, called piommn Adami, which is more marked
in the male sex ; and between the cartilage and the hyoid bone is a
slight interval, corresponding with the thyro-hyoid membrane.

Below the thyroid is the narrow prominent ring of the cricoid
cartilage ; and between the two the finger may distinguish another
interval, which is opposite the crico-thyroid membrane.

Inmiediately above the sternum, and bounded on each side by the
prominent sterno-mastoid muscle, is a narrow depression — supra-
sternal fossa, the depth of which is much increased in emaciated
persons, and in it the tube of the trachea can be recognised. In
some bodies, especially in women, the swelling of the thyroid gland
may be felt by the side of the air-tube.

Direction. As it is necessary for the liberation of the upper limb
to have an early dissection of the posterior part of the neck, the student
should lay bare now only the part behind the sterno-mastoid muscle.

Dissection. To raise the skin from the posterior triangle of the
neck, make an incision along the sterno-mastoid muscle from the
tip of the mastoid process to the clavicle one inch external to its

thyroid
cartilage,

thyro-hyoid
interval,

cricoid
cartilage,

crico-
thyroid
interval,

and supra-
sternal
depression.

Dissection
of the
platysma.

THE PLATYSMA MYOTDES.

573

articulation with the sternum ; from the lower end of this make
another cut outwards along the clavicle as far as the acromion and
reflect the piece of skin backwards towards the trapezius muscle. The
superficial fascia, which will then be brought into view, contains
the platysma ; and to see that muscle, it will be necessary to take
the subcutaneous laver from the surface of the fibres.

Anterior belly of digastric.
Posterior belly of digastric.

Anterior belly of omo-liyoid.

Supraclavicular
triangle.

Posterior belly of the omo-hyoid.
Fig. 209, — Diagram of the Triangles of the Neck.

The ANTERIOR TRIANGLE is made up of —

1. The sub-maxillary triangle.

2. The carotid triangle.

3. The muscular triangle.

The POSTERIOR TRIANGLE is made up of —

1. The occipital triangle.

2. The supraclavicular triangle.

The PLATYSMA MYOiDES is a thin subcutaneous muscular layer, Platysma
which is now seen only in its posterior half. It is placed across the "^"^'^^^
side of the neck, and extends from the shoulder to the face. Its
fleshy fibres take origin from the skin and subcutaneous tissue over arises at
the clavicle and acromion, as well as from that covering the highest ^ °" ^^ '
parts of the pectoral and deltoid muscles ; ascending through the
neck, the fibres are inserted into the jaw and the angle of the mouth, inserted

into jaw

574

covers
triangle ;

Dissection.

External

iugular

vein

crosses side
of neck to
subclavian.

Cervical
fascia.

Part behind
sterno-
niastoid
muscle

sends a
process
around
omo-hyoid.

DISSECTION OF THK NECK.

The lower part of the muscle is more closely united to the skin
than the upper, and covers the external jugular vein as well as the
lower part of the posterior triangle. At first the fibres of the
muscle are thin and scattered, but they increase in strength as they
ascend. The oblique direction of the fibres should be noted,
because in venesection in the external jugular vein the incision is
to be so made as to divide them transversely.

The action will be found with the description of the remainder
of the muscle (p. 579).

Dissection. The platysma is to be cut across near the clavicle,
and to be reflected forwards as far as the incision over the sterno-
mastoid muscle, but it is to be left attached at that spot. In raising
the muscle the student mast be careful of the deep fascia of the
neck, and of the external jugular vein, with the superficial descend-
ing branches of the cervical plexus, which are close beneath the
platysma, and which he should dissect out.

The EXTERNAL JUGULAR VEIN (fig. 210,^ p. 576) begins just
behind the angle of the jaw by the vinion of the posterior division
of the temporo-maxillary with the jiosterior articular vein (fig. 211,
p. 582). Descending beneath the platysaia to the lower part of
the neck, it there pierces the deep cervical fascia to open into the
subclavian vein. Its course down the neck will be marked by a
line from the angle of the jaw to the middle of the clavicle. Beyond
the sterno-mastoid muscle the vein is dilated, and the swollen part
(sinus) is limited by two pairs of valves, — one being situate below
at the mouth of the vein, and the other near the muscle. Small
superficial branches join the vein, and an offset connects it with the
anterior jugular vein. Its size and the height at which it crosses
the sterno-mastoid muscle, are very uncertain.

The DEEP CERVICAL FASCIA, like the aponeuroses in other
regions of the body, consists of a superficial layer which surrounds
the neck continuously, and of processes that are prolonged inwards
between the muscles. In some bodies this fascia is thin and indistinct.

In its extent round the neck the membrane encases the sterno-
mastoid, and has a different disposition before and behind that
muscle. As now seen passing backwards from the mu-^cle, the
fascia continues over the posterior triangular space, and encloses the
trapezius in its progress to the spines of the vertebrae. At the
lower part of the neck it is attached to the clavicle, and is
perforated by the external jugular vein and the cutaneous nerves.

After the superficial layer has been removed near the clavicle, a
deep process may be observed surrounding the omo-hyoid muscle,
and passing downwards behind the clavicle, to be fixed at the back
of that bone, and the anterior end of the first rib.

POSTERIOR TRIANGULAR SPACE.

triangular This space (fig. 210), having the form and position before noted

space of ij^ about eight inches in length. It contains the cervical and brachial
the neck.

THE POSTERIOR TRIANGULAR SPACE. 575

plexuses, with the portion of the subclavian artery and some
offsets of tlie vessel and the nerves.

Dissection. Bv the removal of the cervical fascia and the fat Dissection
between the sterno-mastoid and trapezius muscles, the posterior ^ ^ space,
triangle of the neck will be displayed. In the execution of this
somewhat difficult task the student should proceed cautiously, to
avoid injuring the numerous nerves and vessels in the space.

Seek first the small omo-hyoid muscle (tig 210 ^), which crosses Find
the space obliquely about an inch above the clavicle, and divides it °'"^' ^°' '
into two smaller triangles, occipital and supra clavicular (fig. 209).
Close to or beneath the upper border of the muscle lie the slender
nerve and vessels to it : the nerve is derived from the ansa
hypoglossi, and the artery from the suprascapular.

Above the omo-hyoid muscle will be found the branches of the Nerves
cervical plexus, together with the spinal accessory nerve ; the latter omo-hyoM ;
will be recognised by its piercing the sterno-mastoid muscle. The
greater number of the branches of the cervical plexus descend to the
shoulder ; but the small occipital and great auricidar nerves ascend
to the head, and the superficial cervical branch is directed forwards
over the sterno-mastoid muscle.

Below the omo-hyoid find the large subclavian artery and the vessels
brachial plexus, which have a deep position, and run downwards *'^'
and outwards. Also the following vessels and nerve are to be
further cleaned, viz., the suprascapular vessels behind the clavicle ;
the tr msverse cer\ical vessel, which is higher in the neck, taking
an outw^ard direction beneath the omohyoid muscle ; and, lastly,
the small branch of nerve to the subclavius muscle, which lies and » small
about the middle of the space between the clavicle and the
omo-hyoid.

Underneath the trapezius, where it is attached to the clavicle, Define
define the uppermost digitation of the serratus magnus muscle ; and ^^"^* "^'
behind the brachial plexu-;, towards the lower part of the space, the
middle scalenus muscle appears. Through the scalenus issue two and nerves
muscular nerves ; one, the long thoracic, formed by two or three s^j^nu^.
roots, for the serratus magnus ; the other smaller, and higher up,
for the rhomboidei.

Limits of the space. The space is bounded in front by the sterno- Boundaries,
mastoid muscle (^), and behind by the trapezius (2). Its base corre-
sponds with the middle third of the clavicle, and its apex is at the
skull. In its floor are several muscles, which are placed in the
following order from above downwards, viz., splenius capitis, levator,
anguli scapulae (^), and middle scalenus (^) ; and at the lower and
outer angle, somewhat beneath the trapezius, lies the upper part of
the serratus magnus. Covering the space are the structures already
examined, viz., the skin and superficial fascia, the platysma over the
lower half or two- thirds, and the deep fascia.

The small omo-hyoid muscle (^) crosses the space near the clavicle, is divided
so as to divide it into two, a lower or supraclavicular triangle, and Jy 9™°-
an upper or occipital (fig. 209).

The supraclavicular triangle is the smaller, and contains the sub-

576

DISSECTION OF THE NECK.

clavian artery. It is bounded in front by the sterno-mastoid, above
by the posterior belly of the onio-hyoid, ^and below by the clavicle.

Fig. 210, — Part of the Posterior Triangle of the Neck is here dis-
played, BUT the Student should carry the Dissection as high as
THE Head, so as to lay bare the whole of that Space.

1. Sterno-mastoid.

2. Trapezius.

3. Posterior belly of omo-hyoid.

4. Anterior scalenus, with the
phrenic nerve on it, exposed by the
shrinking of the sterno-mastoid.

5. Middle scalenus.

6. Levator anguli scapulae.

7. Third part of subclavian
artery.

8. External jugular vein joining
the subclavian below.

9. Brachial plexus.

10. Spinal accessory nerve.
(Blandin's Surgical Anatomy.)

Extent of This space measures commonly about two inches from before

^*^ ■ backwards, and about one inch from above downwards at its base.
Trunks of Crossing the area of this space, rather above the level of the

nervS^'''^ clavicle, is the trunk of the subclavian artery (fig. 210, ') which

POSITION OF THE SUBCLAVIAN VESSELS. 577

issues from beneath the anterior scalenus muscle, and is directed
over the first rib to the axilla. In the ordinary condition of the
vessel the companion subclavian vein is seldom seen, owing to its
being placed lower down behind the clavicle. Above the artery and their

J the large cords of the brachial plexus (^), which accompany the position,
ve&sel, and become closely applied to it beneath the clavicle.
Behind the artery and the nerves is the middle scalenus muscle (^).
And below the A'essel is the first rib.

Along the lower boundary of the space, and rather beneath the Branches
clavicle, lie the suprascapular vessels ; and crossing the upper angle, ^ ^^^® '''
at the meeting of the omo-hyoid and sterno-mastoid muscles, are
the transverse cer^^cal vessels. Entering the space from above is the
external jugular vein (^), which descends over (seldom under)
the omo-hyoid, and opens into the subclavian vein ; in this region
the vein receives the suprascapular and transverse cervical branches,
and sometimes a small vein over the clavicle, from the cephalic
vein of the arm.

The length of this space depends mainly upon the extent of the Variations
ttachment of the trapezius and sterno-mastoid muscles to the of the space,
clavicle : in some bodies these muscles occupy nearly the whole
length of that bone, leaving but a small interval between them ;
and occasionally they meet, so as to cover the subclavian artery
altogether. The space also varies in height according to the
]iosition of the omo-hyoid, for this muscle sometimes lies close to,
or even arises from the clavicle, while on the other hand, it may be
distant one inch and a half from that bone.

In depth the space varies naturally ; and in a short thick neck also in the
with a prominent clavicle, the artery is farther from the surface natural^°*^*^
than in the opposite condition of the parts. But the depth may be
altered much more l>y change in the position of the clavicle, as the
shoulder is carried forwards or backwards. And lastly, the artery and
may be concealed entirely in its usual position by forcing upwards ^'^^I'^^^i^l-
the arm and shoulder, as the collar-bone can be raised above the
level of the omo-hyoid muscle.

The position of the subclavian artery itself is also subject to Departure
variation, for the vessel may be one inch and a half above the ord^ary
clavicle, or at any point intermediate between this and the bone: state of the

flrtGrv

therefore the drawing down of the shoulder, so as to expose the , .' '
vessel as much as possible, is an important preliminary in opera- branches,
tions to reach the subclaWan artery in this space. In the typical
condition there is not any branch arising from the trunk in this
part of its coui-se ; but the posterior scapular artery (fig. 210) is
frequently given off beyond the scalenus anticus, and sometimes
there is more than one branch.

The subclavian vein occasionally rises upwards as high as the Position of
artery ; or in some rare instances, it even lies with the artery
beneath the anterior scalenus. The position of the external
jugular vein with regard to the subclavian artery is very uncertain ;
and the branches connected with its lower end often form a kind of
plexus over the arterial trunk.

578 DISSECTION OF THE NECK.

Occipital The occipital triangle is larger than the supraclavicular. Its

triangle boundaries in front and behind are the stemo-mastoid and the

trapezius, and below the posterior belly of the omo-hyoid muscle,
contains In it are contained cliiefly the ramifications of the cervical

iymphati'cs ; plexus ; and a chain of lymphatic glands lies along the sterno-
aiso spinal ' mastoid muscle. The spinal accessory nerve Q^) is directed
accessory oblifiuely across this interval from the sterno-mastoid muscle,

which it pierces, to the under surface of the trapezius ; and a

communication takes place between it and the spinal nerves in the

space.

Nerves of SUPERFICIAL BRANCHES OF THE CERVICAL PlEXUS. These

the cervical j^gj-ves emerge from beneath the sterno-mastoid muscle about the
middle of its hinder border, and are thence directed both upwards
and downwards.

that ascend, The ASCENDING SET (fig. 210) are three in nimiber, viz., small

^''^'~ occipital, great auricular, and superficial cervical.

Small The small occipital nerve (fig. 205, p. 562) comes from the

occipital. second, and in most cases also from the third cervical nerves, and
is directed upwards to the head along the posterior border of the
sterno-mastoid muscle. It perforates the fascia near the skull, and
is distributed between the ear and the great occipital nerve, as
already seen. Occasionally there is a second cutaneous nerve to
the back of the head.

Great The great auricular nerve (fig. 205) is derived from the second

auricular ^^^j^ third cervical nerves. Perforating the deep fascia at the pos-
terior border of the sterno-mastoid muscle, the nerve is directed
upwards between the platysma towards the lobule of the ear, and
ends in the following branches : — "

supplies The facial branches are sent forwards to the integuments over the

facial, parotid, and a few slender filaments pass into the gland to join the

facial nerve.

auricular, The auricular branches ascend to the external ear, and are chiefly

distributed on its cranial aspect, but one or more reach the lower
part of the outer surface. On the pinna they communicate with
branches furnished from the facial and pneumo-gastric nerves.

and mastoid The mastoid branch is directed backwards to the skin over the

branches, j^astoid process, where it joins the posterior auricular branch of the
facial nerve.

Superficial The superficial cervical nei've (fig. 205, ^■*) arises from the cervical

nerVe*^ plexus in common with the preceding, and turns forward round
the sterno-mastoid muscle about the middle. Afterwards it pierces
the fascia, and ramifies over the anterior triangle. There may
be more than one branch to represent this nerve.

Nerves that The DESCENDING SET of branches (fig. 2 10) are derived from the

escend are ^]jij,(j ^^^ fourth nerves of the plexus, and are directed towards the

clavicle over the lower part of the triangular space. Their number

is somewhat uncertain, but usually there are about three near the

clavicle.

usually three The most internal branch (sternal) crosses the clavicle near its
inner end ; the middle branch (clavicular) lies about the middle of

FRONT OF THE NECK. 579

tliat bone ; and the external {acromial) turns over the clavicular
attachment of the trapezius to the acromion. All are distributed
to the skin of the chest and shoulder.

Derived from the descending set are one or two posterior cutaneous Posterior
nerves of the ned\ which ramify in the integument covering the cutaneous,
trapezius above the scapula.

The lymphatic glands lying along the sterno-mastoid (glandulae Lymphatic
concatenatae) are some of the deep cervical glands, and are continuous °eek^*°
through the lower part of the posterior triangular space with the
glands of the axilla. A chain of siq)erficial cervical glands accom-
panies the external jugular vein ; and close to the skull, over the
apex of the posterior triangular space, are one or two small sub-
occipital glands ; while farther forwards, resting on the insertion of
the sterno-mastoid, there are two or three small mastoid glands.

FRONT OF THE NECK.

Directions. Having displayed the chief structiiies in the
posterior triangle, the student will expose those in the anterior.

Dissection. The skin over the front of the neck is to be turned
forwards to the middle line. Beneath the skin is the superficial to raise
fat, containing very fine oflFsets of the superficial cer^'ical nerve. ^^^^'

To define the platysma muscle, remove the fat which covers it, to show
carrying the knife downwards and backwards in the direction of ^ * ^^^^
the lieshy fibres.

Platysma myoides. The anterior part of the platysma^ viz., Anterior
from the sterno-mastoid muscle to the lower jaw, covers the greater ^f^ysJna-
portion of the anterior triangular space. At the base of the jaw it insertion
is inserted between the symphysis and the masseter muscle ; while into jaw.
other and more posterior fibres are continued over the face, joining
the depressor anguli oris and risorius, as far as the fascia covering
the parotid gland, or even to the cheek-bone.

The fibres have the same appearance in this as in the posterior crossing of
half of the muscle, but they are rather stronger. Below the chin ^^^^ fibres,
the inner fibres of opposite muscles frequently cross for a short
distance, but those of them which are superficial do not always
belong to the same side in difterent bodies.

Action. The hinder part of this muscle draws the corner of the Use on
mouth downwards and outwards ; the fore part is used in swallow- ™^^^^
ing, and carries forwards the skin of the upper part of the neck, jJJJ^*^*^^^-
thus facilitating the upward movement of the larynx. When the
muscle contracts forcibly, the skin of the upper part of the chest and
shoulder is also raised.

Dissection. Raise the platysma to the base of the jaw, and Dissectioc
dissect out beneath it the branches of the superficial cervical nerve,
and the cervical branch of the facial nerve. Clean also the deep
fascia of the neck, and the anterior jugular vein which is placed near
the middle line.

The SUPERFICIAL CERVICAL NERVE has just been traced from its Superficial
origin in the cervical plexus to its position on the deep fascia of the uerve^^^

PP 2

o80

DISSECTION OF THE NECK.

ascending,

descending
branch.

Branch of
facial nerve
to the neck,

Dissection.

Cervical
fascia in
front of
sterno-
mastoid.

Intermus-
cular strata.

neck. Beneath the platysma it divides into an upper and a lower
branch : —

The upper branch perforates the platsyma, and ends in the skin
over the anterior triangle, extending about half way down the
neck. While beneath the platysma this branch joins the facial
nerve.

The loiver branch likewise passes through the platysma, and is
distributed to the integuments below the preceding, reaching as
low as the sternum.

The INFRAM AXILLARY BRANCH OF THE FACIAL NERVE (p. 564)

pierces the deep cervical fascia, and divides into slender offsets
which pass forwards beneath the platysma, and form arches across the
side of the neck (fig. 205), reaching as low as the hyoid bone.
Most of the branches end in the platysma, but a few filaments
perforate it, and reach the integuments. Beneath the muscle there
is a communication between this branch of the facial and the upper
division of the superficial cervical nerve.

Dissection. Cut across the external jugular vein about the
middle, and throw the ends up and down. Afterwards the super-
ficial nerves of the front of the neck may be divided in a line with
the angle of the jaw, the anterior ends being removed, and the
posterior reflected. The great auricular nerve may be cut through
and the ends reflected.

The part of the deep cervical fascia in front of the sterno-
mastoid is stronger than that over the posterior triangle, and
has the following arrangements. Above, it is fixed to the base of
the lower jaw, and is continued over the parotid gland to the
zygoma. A thickened band passes backwards from the angle of
the jaw to the sheath of the stemo-mastoid, and holds forwards the
anterior border of that muscle. Above this, a deep process is sent
inwards from the hinder margin of the ramus of the jaw, between
the parotid and submaxillary glands, to the styloid process, giving
rise to the stylo-maxillary ligament. In front, the fascia is attached
to the body of the hyoid bone ; and below, to the sternum. Its
lower part forms a dense white membrane, which near the
manubrium becomes divided into two layers, one passing in front
and the other behind that bone, so as to enclose a small space
above it containing a little fat and the transverse liranch of
communication l)etween the anterior jugular veins.

Layers of the membrane are prolonged between the muscles ; and
that beneath the sterno-mastoid is continuous with the sheath of
the cervical vessels. One of these, beneath the sterno-thyroid
muscles, descends in front of the great vessels at the root of the
neck to the arch of the aorta and the pericardium.

anterior triangular space.

Anterior This space (fig. 211, p. 582) contains the carotid vessels and their

spac?"^^^ branches, with many nerves ; and it corresponds with the hollow
on the surface of the neck in front of the sterno-mastoid muscle.

CONTENTS OF THE ANTERIOR TRIANGULAR SPACR. 581

Dissection. To define the anterior triangular space and its Dissection
contents, take away the deep fascia of the neck and the suVijacent trianglel^"^
fat, but without injuring or displacing the several parts. First
clean tlie surface of the muscles below the hyoid bone, leaving
untouched the anterior jugular vein.

The trunks into which the large carotid artery bifurcates are to Trace
be followed upwards, especially the more superficial one (external
carotid), the Ijranches of which are to be traced as far as they lie
in the space. In removing the sheath from the vessels, as they
appear from beneath the muscles at the lower part of the neck, the Seek lougi-
dissector should be careful of the small descending branch of the nerves,
hypoglossal nerve on the surface of the artery. In the sheath
between the vessels (carotid artery and internal jugular vein) will
be found the pneumogastric nerve, and behind the sheath lies the
sympathetic nerve.

Clean the digastric and stylo-hyoid muscles, which cross the ami
space in the direction of a line from the mastoid process to the nerves,
hyoid bone (fig. 209, p. 573), and beneath them look for several
nerves. Thus, crossing the carotid arteries just below the digastric
is the hypoglossal nerve, which gives ofi" its descending branch in
front of the artery, and further forwards a smaller offset to the
thyro-hyoid muscle. Under coyer of the muscles, and taking a
similar direction between the \wo carotid arteries, are the glosso-
pharyngeal nerve and the stylo-pharyngeus muscle. Directed Spinal
downwards and backwards from beneath the same muscles to the *'^^*^''*''*^i-
stemo-mastoid is the spinal accessory nerve.

On the inner side of the vessels, between the hyoid bone and Laryngeal
the thyroid cartilage, the dissector will find the superior laryngeal "^'■^^^•
nerve ; and by the side of the larynx, with the descending part of
the superior thyroid artery, the small external laryngeal branch.

Clean then the submaxillary gland close to the base of the jaw ; Clean gland,
and on partly displacing it from the surface of the mylo-hyoid to^myio"*^
muscle, the student will expose the small branch of nerve to that hyoid.
muscle with the sulmiental branch of the facial artery.

The interval between the jaw and the mastoid process has been
already cleaned by the removal of the parotid gland in the dissection
of the facial nerve.

Limits of the sjmce (fig. 211). Behind, is the sterno-mastoid Boundaries,
muscle ; and in front, the l)0undary is formed by a line from
the chin to the sternum, along the middle of the neck. Above, at
the base of the space, are the lower jaw, the skull, and the ear ;
and below, at the apex, is the sternum. Over this space are
placed the skin, the superficial fascia with the platysma, the deep
fascia, and the ramifications of the facial and superficial cervical
nerves, together with the anterior jugular vein.

Mmcles in the simce. In the area of the triangular interval, as Contents of
it is above defined, are seen the larynx and pharynx in part, and ^ ^v^^^-
many muscles converging towards the hyoid bone, some being above
and some below it. Below are the depressors of that bone, viz.,
omo-hyoid, sterno-hyoid, and sterno- thyro-hyoid (~ to^) ; and above

58-.

DISSECTION OF THE NECK.

Carotid
jirtery in
space :

are the elevator muscles, viz., mylo-liyoid, digastric, and stylo-hyoid.
Connected with the back of the hyoid bone and the larynx are two
of the constrictor muscles of the pharynx.

Vessels in the space. The carotid blood vessels and the internal
jugular vein (6 and 7) occujDy the hinder and deeper part of the space
along the side of the sterno-mastoid muscle ; and thsir course would be

Fig. 211. — Anterior Triangular Space of the Neck (Quain's
"Arteries").

1. Sterno-mastoid. 6. Common carotid artery divid-

2. Sterno-hyoid . iug.

3. Anterior belly of omo-hyoid. 7. Internal jugular vein.

4. Thyro-hyoid. 8. External jugular vein.

In the original drawing the sterno-mastoid is partly cut through.

marked on the surface \)}"d\\\\Q from the stern o-clavicidar articulation
to a point midway between the angle of the jaw and the mastoid
coverings ; process. As high as the level of the cricoid cartilage they are buried
beneath the depressor muscles of the hyoid bone ; but beyond that
spot they are covered by the superficial layers over the sjiace, and
by the sterno-mastoid muscle which, before it is displaced, conceals
♦,he vessels as far as the parotid gland.

CONTENTS OF THE ANTERIOR TRIANGULAR SPACE. 583

For a short distance after its exit from beneath the depressor bifiucation.
muscles of the hyoid bone, the common carotid artery remains a
single trunk ; but opposite, or a little above, the upper border of the
thy raid cartilage it divides into two large vessels, external and
internal carotid. From the place of division these arteries are
continued onwards beneath the digastric and stylo-hyoid muscles
to the interval between the jaw and the mastoid process.

At first the trunks lie side by side, the vessel destined for the Position of
internal parts of the head (internal carotid) being the posterior of to one"'
the two ; but above the digastric muscle it becomes deeper than another,
the other. The more superficial artery (external carotid) furnishes
many branches to the neck and the outer part of the head, viz.. Branches,
some forwards to the larynx, tongue, and face ; others Ijackwards
to the occiput and the ear ; and others upwards to the head.

But the common airotid does not always diWde as here said. J?*°?^^*°f
For the point of branching of the vessel may be moved from division of
opposite the upper border of the thyroid cartilage, either upwards carotid,
or do^^-nwards, i^o that the trunk may remain undivided till it is
beyond the hyoid bone, or it may end opposite the cricoid
cartilage. The di^ision l)eyond the usual place is more frequent
than the branching short of that spot. It may ascend as an
undivided trunk (though very rarely) furnishing offsets to the
neck and head.

In close contact with the outer side of both the common and the Jugular
internal carotid artery, and encased in a sheath of fascia with them,
is the large internal jugular vein, which receives branches in the
neck corresponding to some of the branches of the superficial artery.
In some bodies the vein covers the artery ; and the branches position
joining it above may form a kind of plexus over the upper end of
the common carotid.

Xerves in the space. In connection with the large vessels are the ?^"^ ^.'^l^
following nerves with a longitudinal direction : — On the surface of
the common carotid artery, and most frequently within the sheath, lies
the descending branch of the hypoglossal nerve (descendens cervicis) ;
posteriorly between the artery and jugular vein is the pneumo- ^yi"" along
gastric nerve ; and behind the sheath is the sympathetic nerve.
Along the outer side of the vessels the spinal accessory nerve extends
for a short distance, until it pierces the sterno-mastoid muscle.

Several nerves are placed across the vessels : — thus, directed *°^ crossing
transversely over the two carotids, so as to form an arch below the
digastric muscle, is the hypoglossal nerve giving off its descending
branch. Appearing on the inner side of the carotid arteries, close
to the base of the space, is the glosso-pharyngeal nerve, which
courses forwards between them. To the inner side of the internal
carotid artery, opposite the hyoid bone, the superior laryngeal
nerve comes into sight ; while a little lower down, with the
descending branches of the thyroid artery, is the external laryngeal
Iji-anch of that nerve.

Glatids in the space. Two large glandular bodies, the submaxil- Glands :
lary (tig. 213, ", p. 589) and thyroid (i-), have their seats in tliis ^^'^™*^^'-

584

DISSECTION OF THE NECK.

and thyroid
body.

Parotid
gland.

liyuiphatic
glands.

Anterior
jugular veiu

joins

external

jugular.

Sterno-
mastoid
muscle

has its
origin at
sternum and
clavicle,

and inser-
tion at
skull :

position to
other parts

triangular space of tlie neck. The submaxillary gland is placed
altogether in front of the vessels, and is partly concealed by the
jaw ; beneath it, on the surface of the mylo-hyoid, is the small
nerve to that muscle, with the submental artery. By the side of
the thyroid cartilage, between it and the common carotid artery,
lies the thyroid body beneath the sterno-thyroid muscle ; in the
female this body is more largely developed than in the male.

At the upj)er part of the neck, if the parts were not disturbed,
would be the parotid gland, wedged into the hollow between
the jaw and the mastoid process, and projecting somewhat below
the level of the jaw.

Several lymphatic glands, belonging to the deep cervical group,
lie along the internal jugular vein, under cover of the sterno-
niastoid muscle ; and another set of smaller glands {submaxillary
lymphatic glands) is placed below the base of the jaw.

Directions. The student has now to proceed with the exandna-
tion of the individual parts that have been referred to in the
triangular spaces.

Anterior jugular vein. This vein lies near the middle line
of the neck, and its size is dependent upon the degree of develop-
ment of the external jugular. Beginning in some small l^ranches
below the chin, the vein descends to the sternum, and then bends
outwards beneath the sterno-mastoid muscle, to o^Den into the
external jugular, or into the subclavian vein. In the neck the
anterior and external jugular veins communicate. There are two
anterior jugular veins, one for each side, though one is usually
larger than the other ; and at the bottom of the neck they are
joined by a transverse branch (tig. 171, p. 467).

In many subjects the lower part of the anterior jugular vein is
joined by a considerable branch which runs downwards, along
the anterior border of the sterno-mastoid muscle, from the facial
vein.

The STERNo-CLEiDO-MASTOiD MUSCLE (fig. 211, ') fomis the super-
ficial prominence of the side of the neck. It is narrower in the
centre than at the ends, and arises below by two heads of origin
which are separated by an elongated interval. The inner, or
sternal, head is fixed by a narrow tendon to the anterior surface of
the first piece of the sternum ; and the outer, or clavicular,
has a wide fleshy attachment to the inner third of the clavicle.
From this origin the heads are directed upwards, the sternal pass-
ing backwards, and the clavicular almost vertically, and join al)out
the middle of the neck in a flattened belly. Near the skull the
muscle ends in a broad tendon, which is inserted into the mastoid
process at its outer aspect from tip to base, and by a thin aponeu-
rosis into a rough surface behind that process, and into the outer
part of the upper curved line of the occipital bone.

The muscle divides the lateral surface of the neck into the
two main triangular spaces. On its cutaneous asjject it is
covered by the integuments, the platysma, and the deep fascia,
and is crossed by the external jugular vein, and by the great

THE INFRA-HYOID MUSCLES. 585

auricular aud superlicial cervical nerves. If the muscle l>e cut
through, below and raised, it will be seen to lie on the following
parts : — The cla\H[cular origin is superficial to the anterior scalenus
and omo-hyoid muscles, the transverse cervical and supi-ascapular
arteries, and the phrenic nerve. The sternal head conceals the
depressors of the hyoid bone, and the common carotid artery with
its vein and nerves. After the union of the heads, the muscle is
placed over the cervical plexus, the middle scalenus, and the
elevator of the angle of the scapula ; and near the skull on the
digastric and splenius muscles, the occipital artery, and part of the
parotid gland. The spinal accessory nerve perforates the muscular
fibres about the junction of the upper and middle thirds.

Action. Both muscles acting Ijendthe cervia\l part of the spine, use.
carrying the head forwards ; but one muscle will turn the face to
the opposite side. In conjunction with other muscles attached to
the mastoid process, one sterno-niastoid will incline the head
towards the shoulder of the same side.

In laborious respiration the two muscles will assist in elevating
the sternmn.

The OMO-HYOID MUSCLE crosses beneath the sterno-niastoid, and Omohyoid
consists of two fleshy bellies united by a small intermediate tendon, ^^ng^at
The origin of the muscle from the scapula, and the relations of the scapula,
the posterior belly have been studied in the dissection of the
back (p. 522). From the intervening tendon the anterior fleshy and ends at
belly (flg. 211, 2) is directed upwards along the outer border of^y°*^^"^'
the sterno-hyoid muscle, and is inserted into the lower border of
the body of the hyoid bone, close to the great cornu.

The anterior belly is in contact with the fascia, after escaping relations ;
from beneath the sterno-mastoid, and rests on the sterno-thyroid
and thyro-hyoid muscles. This part of the muscle crosses the
carotid vessels on a level with the cricoid cartilage.

Action. The omo-hyoid muscle depresses and tends to draw use.
backwards the hyoid bone.

The STERXO-HYOID MUSCLE (fig. 211, "^) is a flat thin band nearer sterao-
the middle line than the preceding. It arises from the inner end muscle :
of the clavicle at its posterior aspect, from the back of the
manuljrium and of the cartilage of the first rib. From this origin it
ascends to be inserted into the lower border of the body of the
hyoid bone, internal to the preceding muscle. Its fibres are often
interrupted near the clavicle by a tendinous intersection.

One surface is covered by the stemo-niastoid and the fascia, i-eiations ;
When the muscle is divided and turned aside, the deep surface
will be found to rest on the sterno-thyroid, the thyro-hyoid, and the
thyroid cartilage. The right and left muscles are separated by an
interval which is wider below than above.

Action. It draws the hyoid bone downwards after swallowing ; use.
and in laborious respiration it will aid in raising the sternum.

The STERNO-THYROID MUSCLE is broader and shorter than the stemo-
sterno-hyoid, beneath which it lies. It arises from the posterior muscle:
surfaces of the sternum and the cartilage of the first rib Ijelow the

580

DISSECTION OF THE NECK.

relations ;

Thyro-
hyoid
muscle

Thyroid
body

consists of
two lobes
and a cross
piece.

Relations
and

extent of
lobes.

Middle lobe
or pyramid.

Accessory
glands.

stenio-hyoid, and is inserted into the oljlique line on the side of the
thyroid cartilage, where it meets the thyro-hyoid muscle.

The inner border touches its fellow below, while the outer
reaches over the carotid artery. The superficial surface is for the
most part covered by the preceding hyoid muscles ; and the
deep surface is in contact with the lower part of the common
carotid artery, the trachea, the larynx, and the thyroid body. A
transverse tendinous line frequently crosses the muscle near the
sternum.

Action. Its chief use is to draw downwards the larynx after
deglutition, but in conjunction with the following muscle it can
also act on the hyoid bone.

Like the sterno-hyoid it participates in the movement of the
chest in laborious breathing.

The THYRO-HYOID MUSCLE (fig. 211,4)forms a continuation of
the sterno-thyroid. Arising from the oblique line of the thyroid
cartilage, the fibres ascend to the anterior half of the great cornu,
and the outer part of the body of the hyoid bone.

On the muscle lie the omo-hyoid and the sterno-hyoid ; and
beneath it are the superior laryngeal nerve and vessels.

Actio7i. It draws up the larynx towards the hyoid bone, as in
swallowing. The sterno-thyroid and thyro-hyoid together fix the
thyroid cartilage for the action of the intrinsic muscles of the
larynx.

Dissection. The sterno-hyoid and sterno-thyroid muscles should
now be raised and the thyroid gland cleaned as it overlies the larynx
and trachea. The muscles should not be divided but should be
rendered slack for the purpose required by bending the neck for-
ward. Care should be taken not to injure the vessels of the gland,
and the inferior thyroid vein should be clemmed as it runs down the
front of the trachea.

The THYROID BODY (fig. 212 and fig. 213, l^, p. 589) is a soft
reddish mass, which embraces the upper part of the trachea. It
consists of two lateral lobes, united by a narrow piece across the
front of the windpipe. The connecting piece, from a quarter to
three-quarters of an inch in depth, is named the isthmus, and is
placed over the second, third, and fourth rings of the trachea.

Each lobe is somewhat conical in shape, with the smaller end
upwards, and is about two inches in length. It is interposed
between the windpipe with the larynx and the sheath of the common
carotid artery, and is covered by the sterno-thyroid, sterno-hyoid,
and omo-hyoid muscles. The extent of the lobe varies ; but usually
it reaches as high as the middle of the thyroid cartilage, and as low
as the sixth ring of the trachea.

From the upper border of the thyroid body, a conical process,
known as the 'pyramid, often ascends towards the hyoid bone, to
which it is attached by a fibrous band. The pyramid generally
springs from the inner part of one of the lateral lol)es, seldom from
the isthmus ; and it is sometimes connected to the hyoid bone by a
slip of muscle, the levator glandulce thyroidece. Detached portions of

THE THYliOID BODY. 587

glandular substance, or accessory thyroid glands, are not unfrequently
found between tlie main body and the hyoid bone.

The thyroid body is of a brownish red or purple hue, is granular
in texture, and weighs from one to two ounces. It is larger in the Weight and
woman than in the man. On cutting into the gland a viscid ^'^®-
yellowish fluid escapes. It has not any excretory tube or duct. No duct.

The arteries of the thyroid body are two on each side — superior Arteries :
and inferior thyroid — and they wiU be subsequently examined. The
branches of the external carotids (superior thyroid) ramify chiefly superior,

Lesser cornu.

Gi-eater cornu.

Ponnxui Adanii.

Crico-tliyiX)id membrane.

"^f* A C M E ^

Fig. 212. —Diagram of the Thyroid Gtland and Neighbouring Parts.

on the anterior aspect : while those from the subclavians (inferior inferior,
thyroid) pierce the deep surface of the mass.

Occasionally there is a third branch {art. thyroidea ima) which and some-
arises from the innominate artery in the thorax, and ascending in {{"^ro/d.^^***^
front of the trachea assists in supplying the thyroid l)ody.

The rei7is are large and numerous ; they are superior, middle. Veins,
and inferior on each side. The first two enter the internal
jugular vein. The inferior thyroid veins issue from the lower part inferior,
of the thyroid body, and descend on the trachea, forming a plexus {Jj^yg o„
on that tube l>eneath the stenio-thyroid muscles, and finally enter trachea,
the innominate veins by one or two trunks (fig. 171, p. 467).

58d

DISSECTION OF THE NECK.

Dissection

of the

subclavian

artery

and its
branches ;

of thoracic
duct.

Right lym-
phatic duct;

of brachial
plexus ;

of cervical
plexus.

Directions. The remaining parts included in this section are the
gcaleni muscles and the subclavian blood-vessels, with the cervical
nerves and the carotid blood-vessels. The student may examine
them in the order here given.

Dissection (fig. 213). The sterno-mastoid is to be cut and the
fat and fascia taken away from the lower part of the neck so as to
pi^epare the scaleni muscles with the subclavian vessels and their
branches. By means of a little dissection the anterior scalenus
muscle will be seen ascending from the first rib to the lower
cervical vertebrae, having the phrenic nerve and sul)clavian vein in
front of it, the latter crossing it near the rib.

The part of the subclavian artery on the inner side of the
scalenus is then to be cleaned, care being taken not only of its
branches, but also of the branches of the sympathetic nerve which
course over and along it from the neck to the chest. This dissec-
tion will be facilitated by the removal of the inner part of the
clavicle.

All the branches of the artery are in general easily found, except
the superior intercostal, which is to be sought in the thorax in
front of the neck of the first rib. On, or near, the branch (inferior
thyroid) ascending behind the carotid sheath to the thyroid gland,
is the middle cervical ganglion of the sympathetic ; and the
dissector should follow downwards from it a small cardiac nerve to
the thorax. Only the origin and first part of the arterial branches
can be now seen ; their termination is met with in other stages of
the dissection.

On the left side the student should seek the thoracic duct as it
arches over the part of the subclavian artery internal to the scalenus
muscle. If it is uninjected it looks like a vein, rather flattened,
and smaller than a crow-f|uill ; and it will be found about half an
inch above the clavicle, crossing behind the internal jugular vein,
and then bending downwards to end in the angle between the latter
and the subclavian vein.

The small right lymphatic duct at its entry into the veins in a
corresponding position on the right side should also be found.

The outer part of the subclavian artery having been already
prepared, let the dissector remove more completely the fibrous
tissue from the nerves of the brachial plexus. From the plexus
trace down the small branch to the subclavius muscle in front of
the subclavian vessels, and the branches to the rhomboid and
serratus muscles, which pierce the middle scalenus. If it is thought
necessary, the anterior scalenus may be cut through after the
artery has been studied.

Clean the cervical plexus, beginning with the nerves at their
emergence in the neck in front of the origins of the scalenus
medius and tracing them from this. Seek the muscular branches,
the small twigs to join the descendens cervicis from the hypo-
glossal, and the roots of the phrenic nerve. Lastly, let the
middle scalenus muscle be defined, as it lies beneath the cervical
nerves.

THE SCAT.ENE MUSCLES.

589

The SCALENI MUSCLES are usually described as three in number. Number of
and are named from their relative position, anterior, middle, and muscles,
posterior ; they extend from the transverse processes of the cervical
vertebrse to the first and second ribs.

The SCALENUS ANTicus(fig. 213, 1) is somewhat conical in shape, Scalenus

Fig. 213.

A View of the Common Carotid and Subclavian Arteries
(Qcain's "Arteries").

1. Anterior scalenus, with the 7.
jihrenic nerve on it. 8.

2. Middle scalenus. 9.

3. Levator anguli scapulae. 10.

4. Omo-hyoid. 11.

5. Rectus capitis anticus major. 1 2.

6. Common carotid artery. 13.

Subclavian vein.
Subclavian artery.
Digastric muscle.
Parotid gland.
Submaxillary gland.
Thyroid body.
Trapezius muscle, reflected.

and arises from the anterior tubercles of the transverse processes origin ;
of the third, fourth, fifth, and sixth cervical vertebrae. It is
inserted into the upper surface and inner border of the first rib, insertion
surrounding the rough mark or projection on this part of the bone
known as the scalene tubercle( fig. 214, p. 590).

590

THE DISSECTION OF THE NECK.

relations, More deeply seated below than above, the muscle is concealed by

the clavicle and the clavicular part of the sterno-mastoid : the
with vessels, phrenic nerve lies along its anterior surface, and the subclavian

vein crosses over it near the rib. Ah)ng the inner border is the
and nerves ; internal jngular vein. Beneath it are the pleura, the subclavian

artery, and the nerves of the brachial plexus. The attachment to

the vertebra) corresponds with the origin of the rectus capitis

anticus major muscle,
"se. Action. The muscle raises strongly the first rib, in consequence

of its forward atb^ichment. If the rib is fixed, it bends forwards

the lower part of the neck.

Scalenus The SCALENUS MEDius MUSCLE (fig. 213, 2) is larger than the

medius ; anterior, and extends highest of all on the vertebra?. Its oriqin is
origin : "^

Serratus magnus (first digitation).

Tubercle.

Fig. 214. — The First Rib, showing the Upper Surface.

insertion ;

parts in
contact
with it ;

Scalenus
posticus :

from the posterior tubercles of the transverse processes of all the
cervical vertebra? except sometimes the first or the last ; and it is
inserted into an impression on the upper surface of the first rib,
extending from the tuberosity behind to the groo\'e for the subclavian
artery in front (fig. 214).

In contact with the anterior surface are the subclavian artery
and the cervical nerves, together with the sterno-mastoid. muscle :
the posterior surface rests on the posterior scalenus, and the deep,
lateral muscles of the back of the neck. The fibres are perforated
by the nerves of the rhomboid and serratus magnus muscles.

Action. Usually it elevates the first rib. With the rib fixed,
the cervical part of the spine can be inclined laterally Ijy one
muscle.

The SCALENUS POSTICUS is inconsiderable in size, and appears
to be part of the preceding muscle. Arising from two or three of

THE SUBCLAVIAN ARTERY. oWl

the lower cervical transverse processes, it is inserted below, by a attach-
thin tendon about half an inch wide, into the second rib in front of ^^^^^ '
the serratus posticus superior.

Action. It acts as an elevator of the second rib ; and its fibres "^^•
having the same direction as those of the mediiis, it will help to
incline the neck in the same way.

The SUBCLAVIAN ARTERY (fig. 213) is the first portion of the Subclavian
large trunk which supplies the upper limb with blood, and is thus ^ ^
designated from its position beneath tlie clavicle. On the right side, extends to
this vessel is derived from the bifurcation of the innominate "^^^'^'^ ^™**'
artery behind the sternoclavicular articulation, and the part of it
named suljclavian extends as far as the outer border of the firet rib.
Qn tJie left side the artery arises in the thorax from the arch
of the aorta, and the first part therefore has a longer course,
and the special points in connection with the vessel will be mentioned
after a general description of the vessel in the neck has been
given. To reach the limb the artery crosses the lower part of
the neck, taking an arched course over the top of the lung and the «

first rib, and between the scaleni muscles. For the purpose of is divided
describing its numerous connections the vesvsel is divided into three parts. *^^^
imrts ; the first extending from the sterno-clavicular articulation to
the inner l)order of the anterior scalenus ; the second, beneath the
scalenus ; and the third, from the outer border of that muscle to
outer edge of the first rib.

First Part. Internal to the anterior scalenus the artery lies First part,
deeply in the neck, and ascends somewhat from its origin. Between s^ienus, ^
the vessel and the surface will be foimd the common tegumentary is deep,
coverings with the platysma and the deep fascia ; the sterno-
mastoid, sterno-hyoid, and stemo-thyroid muscles ; and a strong in front ot,
deep process of fascia from the inner border of the scalenus muscle.
Behind and below, it rests upon the pleura, which ascends into behind, and
the arch formed by the vessel ; and the apex of the lung separates °^
the artery from the A'ertebrse and the posterior ends of the first and
second ril)s.

Veins. The innominate vein lies below and rather in front of Veins with
this part of the artery. The internal jugular vein crosses the ^^^ ^^'
arterial trunk close to the scalenus ; and underneath this vein,
with the same direction, lies the vertebral vein. Much more
superficial, and separated from the artery by muscles, is the deep
part of the anterior jugular vein.

Xerres. In front of the artery lies the pneumo-gastric nerve, near Position of
to the internal jugular vein ; and inside this, the lower cardiac "®"^^-
branch of the same ner^e trunk. Beneath the subclaAian artery on
the right side winds the recurrent branch of the pneumo-gastric ;
and one or two branches of the sympathetic nerve form loops round
the vessel.

Second Part. Beneath the scalenus the vessel is not so deep as in Second part
the first part of its course, and at this spot it rises highest above the scai^^us
clavicle. It is covered by the integuments, platysma, and deep i„ ^.Q^t
fascia : then by the clavicidar origin of the stemo-mastoid ; and

592

DISSECTION OF THE NECK.

behind and
below.

Position of
vein :

of nerves to
the artery.

Third part

is sui>er-
flcial.

Parts cover-
ing it ;

and beneath.

Position of
veins :

of nerves to
artery.

Pecnliarities
of origin,

level and
course.

Branches of
subclavian :

from first,

second,

lastly by the anterior scalenus. Behind and helow the art en' are
the pleura and lung.

Veins. Below the level of the artery, and separated from it by
the anterior scalenus muscle, lies the arch of the sul:)clavian vein.

Nerves. In front of the scalenus descends the phrenic nerve.
Above the vessel, in the interval between the scaleni, are placed the
large cervical nerves ; and the trunk formed by the last cervical and
first dorsal nerves is behind the artery.

Third Part. Beyond the scalenus the artery traverses the
clavicular part of the posterior triangular space (fig. 210), and is
nearer the surface than in the rest of its course : this part of the
vessel is enclosed in a sheath of the deep cervical fascia, which it
receives as it passes from between the scaleni. It is comparatively
superficial in the greater part of its extent, for it is covered
only l)y the integuments, the platysma, and deep fascia ; but near
its termination the vessel gets under cover of the clavicle and sub-
clavius muscle, and the suprascapular vessels cross in front of it.
In this part of its course the artery rests on the surface of the first
rib, which is interposed between it and the pleura ; and the insertion
of the scalenus medius is behind it.

Veins. The subclavian vein approaches the artery, not being
separated by muscle, but lies commonly at a lower level. The
external jugular vein crosses it near the scalenus muscle ; and the
suprascapular and transverse cervical tributaries, which enter the
jugular, sometimes form a plexus over this part of the artery.

Nerves. The large nerves of the brachial plexus are mostly above
the artery, but the lowest trunk is still behind and close to it,
and the small nerve to the subclavius crosses it about the
middle. Superficial to the cervical fascia lie the descending
cutaneous branches of the cervical plexus.

Pecnliarities. The artery may spring as a separate trunk from
the arch of the aorta, in which case it takes a deeper course than
usual to reach the interval between the scaleni muscles.

The level of the arch fonned by the subclavian artery in the
neck varies in different subjects, and occasionally the vessel pierces,
or even passes in front of the scalenus anticus muscle.

Origin of Branches. The chief branches of the subclavian
artery are four in number. Three of these arise from the first part
of the arterial trunk : — one (verteh'al) ascends to the head ; another
(internal mamniary) descends to the chest ; and the remaining one
{thyroid axis) is a short thick trunk, which furnishes branches
inwards and outwards to the thyroid body and the shoulder. These
arise conmionly near the inner border of the scalenus anticus muscle,
so as to leave an interval at the beginning of the trunk free from
offsets. This interval varies in length from half an inch to an inch
in the greater niimber of cases ; and its extremes range from less
than a quarter' of an inch to an inch and three quarters. In some
instances the branches are scattered over the first part of the artery.

On the right side the fourth branch (superior intercostal) arises
beneath the anterior scalenus from the second part of the artery,

THE SUBCLAVIAN ARTERY. 593

md gives oft' the deep cervical branch : a small spinal artery fre-
{iiently comes from this part of the trunk. On the left side the
jrigin of this vessel is usually from the first part of the artery, a
ittle internal to the scalenus anticus.

If there is a branch present on the third part of tlie artery, and third
t is commonly the posterior scapular : if more than one, the ^*^'^-
nternal mammary, the suprascapular, or the thyroid axis may
je added.

The LEFT SUBCLAVIAN ARTERY arises from the arch of the aorta, Left
LStead of from an innominate trunk, and ascends thence over the arterv^**"
fir^t rib in its course to the upper limb. With this difl'erence on differs imich
the two sides in the origin of the subclavian- -the one vessel stibclavlan

eginning opposite the stenio-cla\icular articulation, the other in
the thorax — it is evident that the length and relations of the part
of the artery on the inner side of the scalenus anticus must also
differ on the two sides.

First part. The part of the artery internal to the anterior scalenus in the first
is much longer on the left than on the right side. It ascends nearly ^^ '
A'ertically from its origin to the level of the first rib, and then bends
somewhat abruptly outwards over the top of the lung. On leaving
the chest it is deeply placed in the neck, near the spine and the
fesophagus, and does not rise iisually so high above the first rib as
the right subclavian.

Between the artery and the surface are structures like those on relations to
the right side, viz., the integuments with the platysma and deep pa^a^" "'°
fascia, and the sterno-mastoid, hyoid, and thyroid muscles. To the
imier side are the cesophagus and the thoracic duct, the latter
arching forwards above this part of the artery ; and the pleura is in
contact with the outer and posterior surfaces. Its relations lower
in the chest are described in the dissection of the thorax (p. 468).

Veins. The internal jugular and vertebral veins, as well as the veins ;
beginning of the innominate, are in front of this part of the artery.

Nerves. The pneimio-gastric nerve lies parallel to the vessel position of
instead of across it as on the right side ; and the phrenic nerve "^'■^^*
crosses over it close to the scalenus. Accompanying the artery are
the cardiac branches of the sympathetic, which course along its
inner side to the chest.

The second and third parts of the artery and its branches are Rest of
essentially the same as on the right side. artery.

Branches of the Subclavian. 1. The vertebral artery is Vertebral
generally the first and largest branch of the subclavian, and arises neck.* *" "^
from the upper and posterior part of the trunk. Ascending between
the contiguous borders of the scalenus anticus and longus colli
muscles, this branch enters the foramen in the transverse process of
the sixth cervical vertebra, and is continued upwards to the skull
through the foramina in the other cervical vertebrae. Before the
artery enters its aperture it lies behind the internal jugular vein, and
is crossed by the inferior thyroid artery (fig. 2 1 3). It is accompanied
by branches of the sympathetic nerve, and supplies small muscular
offsets. Its farther course and distribution ^vill be given afterwards. Small

° brancaes.

D.A. Q Q

594

Vertebral
vein, and
branches.

Internal
mammary
artery in
the neck.

Thyroid axis

divides into
three.

Supra-

scapiilar

artery.

Trausvert
cervical
artery :

size and
ending vary.

Inferior
thyroid
artery

gives laryn-
geal offset,

and ascend-
ing cervical
blanch.

DISSECTION OF THE NECK.

The vertebral vein issues with its accompanying artery, to whicli
it is here superficial, and descends over the subclavian artery tc
join the innominate vein ; it receives the deep cervical vein, and the
branch (anterior vertebral vein) that accompanies the ascending
cervical artery.

2. The internal mammary artery leaves the lower part of the sub-
clavian artery, and coursing downwards beneath the clavicle, and
on the outer side of the innominate vein, enters the thorax betweei
the cartilage of the first rib and the pleura. As the artery dis-
appears in the chest, it is crossed superficially by the phrenic nerve.
The vessel is distributed to the walls of the chest and abdomen ; and
its anatomy has been learnt with the dissection of those parts (see
p. 440).

3. Ihyroid axis. This is a short thick trunk (fig. 213) which
arises from the front of the subclavian artery near the anterior
scalenus muscle, and soon divides into three branches — one to the
thyroid body, and two to the back of the shoulder.

a. The siiprascapular branch courses outwards across the lower
part of the neck, behind the clavicle and subclavius muscle, to the
superior border of the scapula, and entering the supraspinous fossa
is distributed on the dorsum of that bone. The connections of this
artery have been more fully seen in the dissection of the back.

b. The transverse cervical branch, usually larger than the preceding,
takes a similar direction, though higher in the neck, and ends
beneath the border of the trapezius muscle in superficial cervical
and posterior scapular branches as already traced. In its course
outwards through the posterior triangular space, this branch
crosses in front of the anterior scalenus, the phrenic nerve, and the
brachial plexus, but usually behind the omo-hyoid. Some small
offsets are supplied by it to the parts in the posterior triangle.

In many bodies the transverse cervical Aessel is of small size,
and ends as the superficial cervical artery, while the posterior
scapular branch arises separately from the third, or even from the
second part of the subclavian trunk (fig. 213).

c. The inferior thyroid artery is the largest offset of the thyroid I
axis. Directed inwards with a flexuous course to the thyroid l^ody,
this branch passes beneath the common carotid artery and the accom-
panying vein and nerves, and in front of the longus colli muscle, to
the side of the trachea. Behind the lateral lobe of the thyroid
body it crosses either in front of or behind the recurrent nerve, and
divides into branches which enter the lower part of the gland, and
communicate with the superior thyroid and its fellow.

Near the larynx an inferior laryngeal branch is directed upwards
with the nerve of the same name, and other offsets are furnished to
the trachea and oesophagus, and to the neighbouring muscles.

The ascending cervical branch is directed upwards between the
origins of the scalenus anticus and rectus capitis anticus major, and
ends in branches to those muscles and the posterior triangle of
the neck. Some small spinal offsets enter the spinal canal through
the intervertebral foramina.

THE SUBCLAVIAN VESSELS. 595

The veins coiTesponding with the branches of the thyroid axis Veins cor-
have the following destination : — those with the suprascapular and to'artcrieL^
transverse cervical arteries open into the external jugular vein. But
tlie inferior thyroid vein, beginning in the thyroid body, descends
on the front of the trachea to the innominate vein.

4. The superior intercostal artery arises from the posterior part of Superior
the sul)clavian under cover of the scalenus anticiLs on the right side and branch,
internal to the muscle on the left. It arches over the apex of the
lung, and jxisses downwards in front of the neck of the first rib ; its
distribution to the first two intercostal sjjaces has been seen in the
thorax (p. 483).

Arising in common with this branch is the deep cervical artery, Deep
which passes backwards between the transvei-se process of the last bral?ch.
cervical vertebra and the first rib, lying internal to the two hinder
scaleni miLscles and the fleshy slips continued upwards from the
erector spinae, to end beneath the complexus muscle at the i>osterior
l»art of the neck as already seen (p. 532).

A spinal branch is frequently given from the second part of the Spinal
subclavian artery ; its offsets are continued into the spinal canal ™"^ '
through the intervertebral foramina.

The SUBCLAVIAN VEIN is much shorter than the companion artery, Subclavian
reaching only from the outer edge of the first rib to the inner border
c>f the anterior scaleniLs. It is a continuation of the axillary vein,
and ends by joining the internal jugular in the innominate trunk.
Its course is arched below the level of the artery, from which it is
separated by the scalenus anticus.

Branches. The subclavian vein is joined at the outer edge of the its
ant^irior scalenus by the external jugular vein, and sometimes also
by the anterior jugular. Into the angle of union of the subclavian
and internal jugular veins the right lymphatic duct oj)ens (fig. 215,^) ; opening of
and at the like spot on the left side, the large lymphatic or thoracic ducts,
duct ends (tig. 215, ^). The highest pair of valves in the subclavian Valves,
trunk is placed outside the opening of the external jugular vein.

It should be borne in mind that occasionally the vein is as high Position
in the neck as the thiixi part of its companion artery ; and that it ™*y ^^^y-
has been seen in a few instances with the artery beneath the
anterior scalenu-s.

The THORACIC DUCT couveys the chyle and lymph of the greater Thoracic
part of the body into the venous circulation. Escaping from the
thorax on the left side of the tesophagus, the duct ascends in the comes from
neck as high as the seventh cervical vertebra. At the spot men- '

tioned it issuCvS from beneath the carotid artery and the internal
jugular vein, and arches outwards and downwards above or over the
subclavian artery, and in front of the anterior scalenus muscle and and joins
phrenic nerv^e, to open into the angle of junction of the subclavian ^*^""''
with the internal jugular vein. Double valves, like those of the valves;
veins, are present in the interior of the tube ; and a pair guards
the opening into the posterior part of the vein. Frequently the frequent
upper part of the duct is divided ; and there may be separate ^^^^ ^ '
openings into the large \eins corresponding with those divisions.

QQ 2

696

DISSECTION OF THE NECK.

branches. Large lymphatic vessels from the left side of the head and neck,

and from the left upper limh, open into the upper part of the duct,
and sometimes separately into the veins (l^).

The ANTERIOR PRIMARY BRANCHES OF THE CERVICAL NERVES

spring from the common trunks in the intervertebral foramina, and

appear on the side of the neck between the intertransverse muscles.

position and These nerves are eight in number, and are equally divided between

the cervical and brachial j^lexuses ; the upper four being combined

in the former, and the remaining nerves in the latter plexus.

Close to their origin they are joined by offsets of communication

from the sympathetic cord.

First two To this general statement some addition is needed for the first

rest.^ ^^^^ ^^"^^ nerves, the peculiarities of which will be noticed later.

Cervical
nerves :

Fig. 215. — Diagram of the Enwng of the Right Lymphatic Duct and
THE Thoracic Duct in the Veins.

1. Upper vena cava.

2. Right, and 3, left innominate
vein.

4. Left, and 5, right internal
jugular.

6. Left, and 7, right subclavian
vein.

8. Thoracic duct.

9. A lymphatic trunk joining the
right lymphatic duct, as this is about
to end in the subclavian vein.

10. A lymphatic trunk opening
separately into the left subclavian
vein.

Brachial
plexus,
formed by
five nerves.

Disposition
of nerves in
the plexus.

Brachial plexus (fig. 216). The lower four cervical nerves
and the larger part of the first dorsal are blended in this plexus ;
and a fasciculus is added to them from the lowest nerve entering
the cervical plexus. Thus formed, the plexus reaches from the
neck te the axilla, w^here it ends in nerves for the upper limb.
Only the part of it above the clavicle can now be seen. In the
neck the nerves lie at first between the scaleni muscles, oj)posite
the four lower cervical vertebra?, and afterwards in the posterior
triangular space. The arrangement of the nerves in the plexus is
as follows : —

The fifth and sixth nerves unite near the vertebra?, forming an
upper primary trunk ; the seventh remains distinct and constitutes

THE BRACHIAL PLKXUS.

507

[I middle trunk ; and the eighth cervical and first dorsal join beneath Three
the anterior scalenus in a Imcer trunk. Near the outer border of }*"™JZ

Fig. 216. — Diagram of the Brachial Plexus. The Dotted Line Indi-
cates THE Level at which the Cords are Crossed by the Clavicle,

CIV. to cviii. Fourth to eighth
cervical nerves.

Di, and Dii. Fii-st and second
dorsal nerves.

li, and 2i. First and second inter-
costal nerves.

phr. Phrenic nerve,
rh.' Nerve to rhomboids,
pt. Posterior thoracic nerve,
sc. Branch to subclavius.
sps. Suprascapular nerve.

the middle scalenus these three trunks bifurcate, each giviiiii ojff an ?.^^^

1 . , . . . . , ' ? , 1 divides

anterior and a -posterior division. As they pass beneath the into
clavicle the anterior divisions of the upper and middle trunks join Jn^"^'*

posterior
Dranches.

598

DISSECTION OF THE NECK.

Cords of the

brachial

l)lexus.

Branches

in the neck
are :—

Nerves of
scaleni and
longus colli .

Nerve of
rhomboids.

Nerve of
serratus.

Nerve of
.snbclaviiis.

Suprascapu-
lar nerve.

Offset to the
phrenic.

Cervical
plexus.

Arrange-
ment of the

Its offsets
are super-
ficial ;

to form the outer cord of the plexus : the posterior divisions of the
three trunks by their union give rise to the posterior cord ; while
the large anterior division of the lower trunk is continued as tlie
inner cord. The three cords accompany the subclavian artery, lying
to its acromial side, and are continued to the axilla where the
nerves of the limb arise.

Branches. The T)ranches of the plexus may be classed into those
above the clavicle, and those below that bone. Those of the
upper set end mostly in muscles of the lower part of the neck and
of the scapula ; while the lower set consists of the branches to the
upper limb, with which they have been described.

Branches above the clavicle. Branches for the scaleni and
longus colli muscles. These small twigs arise from the nerves close
to the intervertebral foramina, and are seen when the anterior
scalenus is divided.

The branch for the rhomboid muscles (fig. 216, rh) s})rings from
the fifth nerve, and perforates the fibres of the scalenus medius ;
it is directed backwards beneath the levator anguli scapulae to its
destination. Branches are given usually from this nerve to the
levator anguli scapulae.

The nerve of the serratus {\)t), the j^osterior, or long, thoracic nerve,
arises from the fifth, sixth, and generally also the seventh, nerves near
the intervertebral foramina. Piercing the fibres of the scalenus
medius lower than the preceding branch, the nerve is continued
downwards behind the brachial plexus, and enters the serratus
magnus muscle on its axillary surface.

The nerve of the subclavius muscle (sc) is a slender branch, which
arises from the trunk formed by the fifth and sixth nerves, and is
directed downwards over the sul)clavian artery to the deep surface
of the muscle ; it often sends a twig to the phrenic nerve at the
lower part of the neck.

The suprascapular nerve (sps) is the largest of these branches, and
arises from the trunk of the plexus formed Ijy the fifth and sixth
nerves. It is destined for the muscles on the dorsum of the
scapula, and has been dissected with the arm.

Occasionally an off"set from the fifth cervical trunk joins the
phrenic nerve on the anterior scalenus muscle.

The CERVICAL PLEXUS, formed by the upper four cervical nerves,
lies beneath the upper half of the sterno-mastoid muscle, and on the
middle scalenus and the levator anguli scapulae. Each nerve
entering the plexus, except the first, divides into an ascending and
a descending branch, and these unite with corresponding parts of
the adjacent nerves, so as to give rise to a series of arches. From
these arches or loops the difl'erent branches arise : —

The brandies are superficial and deep. Those of the superficial
set are again subdivided into ascending and descending^ and have
been described Avith the posterior triangular space of the neck
(p. 578). The ascending branches may be now seen to spring from
the union of the second and third nerves ; and the descending, to
take origin from the loop between the third and fourth nerves.

DEEP BRANCHES OF THE CERVICAL PLEXUS. r,99

The deejp set of branches remains to be examined : they are and deep,
niiscular and communicating, and may be arranged in an internal ^'~

md an ext-ernal series.

Deep set of branches of the cervical plexus. 1. Internal Phrenic
ERIES. The phrenic or muscular nerve of the diaphragm is "^'^®-
lerived from the fourth, or third and fourth nerves of the plexus ;
nd it may be joined by a fasciculus from the fifth cervical nerve.
Descending oldiquely on the surface of the anterior scalenus
fig. 213) from the outer to the inner edge, it enters the chest
n front of the internal mammary artery, but behind the subclavian
-ein, and traverses that cavity to reach the diaphragm. At the
ower part of the neck the phrenic nerve is joined by a filament of
he sympathetic, and sometimes by an ofl^set of the nerve to the
nibclavius muscle.

On the left side the nerve crosses over the first part of the
uibclavian artery.

The branches to the ansa cervicis are two in number : one arises Nerves to
from the second, and the other from the third cervical nerve. They cervicis.
are spoken of as the communicantes cervicis nerves and are directed
inwards over or under the internal jugular vein to join in a loop with
tlie descendens cervicis branch (p. 602) of the hypoglossal nerve in
fi out of the common carotid artery. The loop of the communication
of the nerves over the carotid artery is called the ansa cervicis.

Muscular branches are furnished to the rectus anticus major and Branches to
longus colli muscles from the trunks of the nerves close to the JJ[„sci^^™^
intervertebral foramina.

Some muscular and connecting branches from the loop between the Branches of
first two nerves will be afterwards seen.

2. External series. Muscular branches are supplied from the Branches to
second nerve to the stemo-mastoid ; from the third and fourth
nerves to the levator anguli scapulae and middle scalenus ; and
from the loop between the same nerves to the trapezius.

Connecting branches with the spinal accessory nerve exist in three Branches
places. First, in the sterno-mastoid muscle ; next, in the posterior ipinaf
triangular space ; and lastly, beneath the trapezius. The union accessory,
with the branches distributed to the trapezius has the appearance of
a plexus.

The COMMON carotid artery is the chief vessel for the supply Common
of blood to the neck and head (fig. 213, ^). The origin of the arterj- :
vessel differs on the two sides, being at the lower part of the neck
on the right side, and in the thorax on the left side.

The cause and relations of the left artery in the neck are the same
as those on the right side, and the description serves for both. (The
part of the left common carotid artery in the thorax has been
described on page 468.)

The right vessel commences opposite the sterno-clavicular articu- origin
lation at the bifurcation of the innominate artery on the right side,
and prolonged up from the thorax on the left, and ends at, or a
little above, the upper border of the thyroid cartilage, on a level
with the fourth cervical vertebra, by dividing into external and

600

DISgECTION OF THE NECK.

Hituation.

Parts
covering it,

beneath it,

and on its
sides.

Position of
veins,

of arteries,

of nerves to
carotid.

Branches
none.

Internal
jugular vein

internal branches. The course of the artery is along the side of the
trachea and larynx, gradually diverging from the vessel on the
opposite side in consequence of the increasing size of the larynx ;
and its direction is marked by a line from the sterno-clavicular
articulation to a point midway between the angle of the jaw and
the mastoid process.

Contained in a sheath of cervical fascia with the internal jugular
vein and the pneumo-gastric nerve, the common carotid artery has
the following connections with the surrounding parts : — As high a.s
the cricoid cartilage the vessel is deeply placed, and is concealed by
the common coverings of the skin, platysma, and fasciae ; and by the
muscles at the lower part of the neck, viz., sterno-mastoid (sternal
origin), sterno-hyoid, omo-hyoid, and sterno-thyroid. But from the
cricoid cartilage to its termination the artery is more superficial, being
covered only by the sterno-mastoid and the common investments of
the neck. The vessel rests mostly on the longus colli and scalenus
anticus muscles, but close to its ending on the rectus capitis anticus
major. To the inner side of the carotid lie the trachea and larynx,
the oesophagus and pharynx, and the thyroid body, the last over-
lapping the vessel by the side of the larynx. Along the outer side
of the carotid sheath is a chain of lymphatic glands.

Veins. The large internal jugular vein lies on the outer side of
the artery, being closely applied to it in the upper part of its course,
but separated from it below by an interval about half an inch wide :
on the left side the vein is nearer to the artery below and is even
sometimes placed over it. One or two superior thyroid veins cross
the upper end of the arterial trunk ; and opposite the thyroid body
another small vein (middle thyroid) is directed backwards over the
vessel. Near the clavicle the anterior jugular vein passes outwards
in front of the artery, but is separated from it by the sterno-hyoid
and sterno-thyroid muscles.

Arteries. An offset of the superior thyroid artery to the sterno-
mastoid aescends over the upper part of the sheath ; and the
inferior thyroid crosses behind it near the lower border of the
cricoid cartilage.

Nerves. The descendens cervicis branch of the hypoglossal lies
in front of the artery, crossing from the outer to the inner side,
and is joined there by the communicating branches from the
cervical plexus. The pneumo-gastric lies within the sheath behind
and between the artery and the vein. The sympathetic cord and
its branches rest on the spine behind the sheath. AH the nerves
above mentioned have a longitudinal direction ; but the inferior
or recurrent laryngeal crosses obliquely inwards beneath the sheath,
towards the lower end of the artery.

As a rule, the common carotid artery does not furnish any
collateral branch, though it is very common for the superior
thyroid to spring from its upper end. At the terminal bifurcation
into the two carotids the artery is slightly bulged.

The INTERNAL JUGULAR VEIN extends upwards to the base of the
skull, but only the part of it that accompanies the common carotid

THE DIGASTRIC MtTSCLE. fiOl

artery is now seen. Placed on the outer side of the artery, the
vein ends below by uniting with the subclavian to form the
innominate trunk. Its proximity to the carotid is not equally
close throughout, for at the lower part of the neck there is a space is close to
between the two, in which the vagus nerve is seen crossing (on the ^^l^^
right side only) the subclavian artery. Sometimes the vein overlaps except
the artery to a considerable extent. - ^lo^^' ■

The lower part of the vein is marked by a dilatation or sinus.
Near its ending it becomes contracted, and is provided with a
single or double valve.

In this part of its course the vein receives the superior and branches,
middle thyroid branches.

Peculiarities of the carotid. The origin of the artery on the right Differences
side may be above or below the point stated. Mention has been arter^" ^
made of the difference in the place of bifurcation, and of the fact
that the common carotid may not be divided into two. As a very in di^ision.
rare occurrence, instead of one there may be two trunks issuing
from l)eneath the hyoid muscles.

Dissection. The dissector may next trace out completely the Dissection,
trunk of the external carotid (fig. 217, p. 603), and follow its
branches until they disappear beneath different parts. Afterwards
he may separate from one another the digastric and stylo-hyoid
muscles, which cross the carotid, and define their origin and
insertion.

The DIGASTRIC MUSCLE (fig. 213, ^, p. 589) consists of two tieshy Digastric

])ellies, united by an intervening tendon. The posterior, the ^-obeiiies
larger of the two, arises from the digastric fossa on the inner side
of the mastoid process ; while the anterior belly is fixed to the
depression by the side of the symphysis of the lower jaw. From
these attachments the fibres are directed to the intervening tendon,
which is surrounded by fibres of the stylo-hyoid, and is united by an which are
aponeurotic expansion to its fellow and to the body and part of tendon I *
the great cornu of the hyoid l)one.

The arch formed by the digastric is superficial, except at the position to
posterior end, where it is beneath the sterno-mastoid and splenius o^^^*''" P^^s.
muscles. The posterior belly covers the carotid vessels and the
accompanying veins and nerves ; and is placed across the anterior
triangular space of the neck in the position of a line from the
mastoid process to the fore part of the hyoid bone. Along its
lower border lie the occipital artery and the hypoglossal nerve, the
former passing backwards, the latter forwards. The anterior belly
rests on the mylo-hyoid muscle.

The muscle forms the lower boundary of a sj)ace between it, the The muscle
jaw, and the base of the skull, which is subdivided into two by the ^^'^^ *
stylo-maxillary ligament. In the posterior portion are contained containing
the parotid gland ('"), and the vessels and nerves in connection °
with it ; in the anterior, are the submaxillary gland (";, with the
facial and submental vessels, and deeper still, the muscles between
the chin and the hyoid bone.

Action. The lower jaw being moveable, the muscle depresses Use,

r>02

DISSECTION OF THE NECK.

Stylo-hyoid
muscle :

insertion ;

sunounds
digastric
tendon :

Twelfth -
nerve in the
anterior
triangle :

one to hyoid
muscles

is joined
with
cervical
nerves.

External
carotid
artery ;

course and
direction.

Parts super-
ficial to it,

that bone and opens the mouth. If the jaw be fixed, the two
bellies acting together will elevate the hyoid bone.

The STYLO-HYOID MUSCLE (fig. 224, H, p. 624) is thin and slender,
and lies immediately alcove the posterior Ijelly of the digastric. It
arises from the posterior surface of the styloid process near the base,
and is inserted into the outer part of the body of the hyoid l)one.

The muscle has the same relations as the posterior belly of the
digastric ; and its fleshy fiT)res are usually perforated by the tendon
of that muscle.

Action. This muscle elevates the hyoid bone in swallowing, and
with the posterior belly of the digastric, prevents the bone being
carried forwards by the elevators.

The HYPOGLOSSAL NERVE (twelfth cranial) (fig. 224, ^), appears
in the anterior triangle at the lower edge of the digastric muscle,
where it hooks round the occipital artery ; it is then directed
forwards to the tongue beneath the tendon of that muscle, and
disappears in front under the mylo-hyoid. In this course the
nerve passes over the two carotids ; and near the great cornu of the
hyoid bone it also crosses the lingual artery. From this part arise
the descending branch, and a small muscular offset to the thyro-
hyoid.

The descendens cervicis branch leaves the trunk of the hypoglossal
as it turns round the occipital artery, and descends on the front of,
or more frequently within, the carotid sheath to below the middle
of the neck, where it is joined by the communicating branches of
the cervical nerves so as to form a single or double loop (ansa cervicis)
with the concavity turned upwards. The descending branch gives
an offset to the anterior belly of the omo-hyoid ; and from the loop
branches proceed to the posterior belly of the omo-hyoid, to the
stemo-hyoid and sterno- thyroid muscles : sometimes another offset
is continued to the thorax, where it joins the phrenic and cardiac
nerves.*

The EXTERNAL CAROTID ARTERY (fig. 217, d) springs from the
bifurcation of the common carotid opposite the thyro-hyoid mem-
brane, and furnishes 1 tranches to the neck, and face, and the outer
part of the head.

From the place of origin it ascends in front of the mastoid
process, and ends just below the neck of the lower jaw in the
internal maxillary and superficial temporal branches. The artery
lies at first in front of the internal carotid, but it afterwards inclines
somewhat backwards and becomes superficial to that vessel. Its
position would be marked with sufficient accuracy l)y a line from
the front of the meatus of the ear to the cricoid cartilage.

At first the external carotid is overlain by the sterno-mastoid,
and by the common coverings of the anterior triangular space, viz.,
the skin, and the superficial and deep fasciae with the platysma.
But above the level of a line from the mastoid process to the hyoid

* Both the descending and the thyro-hyoid branches of the hypoglossal are
composed of fibres which pass from the first and second cervical nerves into
the trunk of the nerve near the base of the skull.

THE EXTERNAL CAROTID ARTERY.

bone, the artery is crossed by the digastric and stylohyoid muscles ;
and higher still it is concealed by the parotid gland. At its
beginning the artery rests against the pharynx ; bnt above the beneath it,
angle of the jaw it is placed over the styloid process and the stylo-

FlG. 217. — EXTKRNAL CaROTID AND ITS SUPERFICIAL BRANCHES ("AnATOMY

OF THE Arteries," Quain).

«.

Comraon carotid.

Supraorbital.

Internal jugular vein.

External nasal.

Internal carotid.

Angular branch of facial

External carotid.

P-

Lateral nasal.

Superior thyroid.

Superior coronary.

Lingual.

Inferior coronary.

//•

Facial.

Inferior labial.

Internal maxillary.

Submental artery.

Superficial temporal.

pharyngeus muscle, which separate it from the internal carotid, and in front.
In front of the upper part of the vessel are the ramus of the jaw
and the stylo-maxillary ligament.

Veins. There is not anyl^companion vein with the external Veins in

,., .,, . "^ ^- .-'^ , . -, -, T .1 X contactwitli

carotid, as with most arteries ; but m the parotid gland the tempore- the artery ;

604

DISSECTION OF THE NECK.

aiifl nervi

Its branches
are anterior,

posterior,
and ascend-

changes in
orijiin

L- -

1
I

and in
nnmber.

Branches
now seen
are —

Superior
thyroid

has these
offsets :

the hyoid
branch,

to sterno-

mastoid

muscle.

to larynx,

to crico-
thyroid
membrane.

Accompany
ing vein.

maxillary vein lies on it, and the anterior division of this trunk
frequently runs with the artery beneath the digastric muscle.
Near the beginning it is crossed by the facial and lingual veins
joining the internal jugular vein.

Nerves are directed from behind forwards over and under the
artery. At the lower border of the digastric the hypoglossal lies
over the vessel, and above that muscle it is crossed by the two
divisions of the facial nerve. Three nerves lie beneath it — begin
ning below, the small external laryngeal; a little higher, th
superior laryngeal ; and near the angle of the jaw, the glosso
pharyngeal.

The BRANCHES of the external carotid are numerous, and are
classed into anterior, posterior, and ascending sets. The anterior
set comprises branches to the thyroid body, the tongue, and the
face, viz., the superior thyroid, lingual, and facial arteries. In the
posterior set are the occipital and posterior auricular branches.
And the ascending set includes the ascending pharyngeal, super-
ficial temporal, and internal maxillary arteries. Besides these, the
external carotid gives other branches to the neighbouring muscles
and to the parotid gland.

The arrangement of the branches of the carotid may be altered by
their closer aggregation on the trunk. The usual number may be
diminished by two or more uniting into one ; or it may be increased
by some of the secondary offsets being transferred to the parent
trunk.

Directions. All the branches, except the ascending pharyngeal,
lingual and internal maxillary, may now be examined ; but those
three will be described afterwards with the regions they occupy.

The SUPERIOR THYROID ARTERY {e) arises near the great cornu of
the hyoid bone, and passes beneath the omo-hyoid, sterno-hyoid
and sterno-thyroid muscles to the thyroid l)ody, to which it is dis-
tributed chiefly on the anterior aspect. This artery is superficial
in the anterior triangle, and furnishes ofl'sets to the lowest con-
strictor muscle of the pharynx and to the muscles beneath which it
lies, in addition to the following named branches ; —

a. The hyoid branch is very small, and runs inwards below the
hyoid bone : it supj)lies the muscles attached to that bone, and
anastomoses with the vessel of the opposite side.

b. A sterno-mastoid branch descends in front of the sheath of the
common carotid artery, and is distril'uted chiefly to the muscle
from which it takes its name.

c. The superior laryngeal artery pierces the membrane between
the hyoid bone and the thyroid cartilage, with the superior
laryngeal nerve, and ends in the interior of the larynx.

d. A small crico-thyroid branch is placed on the membrane be-
tween the cricoid and thyroid cartilages, and communicates with the
corresponding artery of the opposite side, forming an arch.

The superior thyroid vein commences in the larynx and the thyroid
body, and crosses the end of the common carotid artery to open into
the internal jugular vein.

BRANCHES OF THE EXTERNAL CAROTID. 605

The Facial Artery (g) arises above the lingual ; and is directed Facial
u})wards over the lower jaw to the face. In the neck the artery ^' ^'^
]>asses under the digastric and stylo-hyoid muscles, and then beneath
the submaxillary gland, under cover of which it makes a sigmoid
turn. Its anatomy in the face has been given already (pp. 557 et seq.). supplies
From the cervical part branches are given to the pharynx, and to i,I^Ieek *'
structures below the jaw, viz. : —

a. The inferior or ascending falatine branch ascends to the pharynx to the
beneath the jaw, passing between the stylo-glossus and stylo-pharyn- 1*'^^*^*^'
geus muscles, and is distributed to the soft palate, which it reaches
by turning over the upper border of the superior constrictor
muscle. Its place in the palate is frequently supplied by an offset
of the ascending pharyngeal artery.

6. The tonsillar branch is smaller than the i>receding, and passes tonsil,
between the internal pterygoid and stylo-glossus muscles. Opposite
the tonsil it perforates the superior constrictor muscle, and ends
in offsets to that body.

c. Glandular branches are supplied to the submaxillary gland submaxil-
from the part of the artery in contact with it. ^^^' °'^"'^' "

d. The subraental branch arises near the inferior maxilla, and mylohyoid
courses forwards on the mylo-hyoid muscle to the anterior belly "|j"j^^ ^ *"*
of the digastric, where it ends in offsets : some of these tuni

over the jaw to the chin and lower lip ; and the rest supply
the muscles between the jaw and the hyoid bone, one or two
perforating the mylo-hyoid and anastomosing with the sublingual
artery.

The facial vein (p. 559) joins the internal jugular. In the cervical Facial vein,
part of its course it receives branches corresponding to the offsets of
the artery ; and it frequently sends a considerable branch do^^^l wards
to join the anterior jugular vein.

The Occipital Artery springs from the carotid opposite the Occipital
facial branch, near the loMer border of the digastric muscle, and ^^^^
ascends to the inner side of the mastoid process. Here it turns
liackwards in the occipital groove of the temporal bone, passing
al)ove the transverse process of the atlas, and then runs between the ends on
muscles attached to the occipital bone, to become cutaneous and occiput ;
ramify over the back of the head (p. 503). In the part of its
course now exposed the artery lies beneath the digastric muscle,
and crosses over the internal carotid artery, the internal jugular
vein, and the spinal accessory and hypoglossal nerves.

The occijiital artery gives small 1)ranches to the surrounding a stemo-

muscles, and one larger branch to the sterno-mastoid, which bends bra^jjjhl

downwards over the hypoglossal and enters the muscle in company

with the spinal accessory nerve : this branch frequently arises sometimes a

directlv from the external carotid. In some bodies there is also a postenor

" meningeal,

small nuningeal branch entering the skull by the jugular foramen.

The oflfeets at the back of the neck are seen in. the dissection of that

region (p. 532).

The occipital veins are two or three in number, and pass down- Occipital

wards between the muscles of the back of the neck to enter the deep

606

Posterior
auricular :

a branch to
tympanum.

Posterior
auricular
vein.

Temporal
artery :

tenniuation

branches
to parotid,
to articula-
tion,

and to ear ;

branch to
face ;

branch to
temporal
muscle

and fascia.

Temporal
vein.

Dissection.

Tmchea

lies in neck
and thorax :

DISSECTION OF THP: NECK.

cervical vein. They communicate througli the mastoid foramei
with the lateral sinus in the interior of the skull.

The Posterior Auricular Artery is smaller than the pre
ceding branch and takes origin above the digastric muscle. Betweei
the ear and the mastoid process, it divides into two branches for tht
ear and occiput (p. 503).

A small branch (stylo-mastoid), enters the foramen of the samt
name, and supj)lies the middle ear.

The posterior' auricular vein, is of considerable size, and descends
over the upper end of the sterno-mastoid muscle to join the
beginning of the external jugular.

The Superficial Temporal Artery (^) is one of the terminal
branches of the external carotid, and in direction forms the con-
tinuation of that trunk. Ascendiiig in the parotid gland and overJ
the posterior root of the zygoma, it divides on the temporal fascisfl
into anterior and posterior branches, which are distributed over tha
front and side of the head (p. 503). Before dividing the artery give^
off the following branches : —

a. Parotid branches are furnished to the gland of the same name ;
articular twigs to the articulation of the lower jaw ; and musculav
branches to the masseter.

6. Some anterior auricular offsets are distributed to the pinna and
meatus of the external ear.

c. The transverse facial branch leaves the tempoial artery close to
its origin, and is directed forwards over the masseter muscle (p. 559).
On the side of the face it supplies the muscles and integuments, and
anastomoses with the facial artery.

d. The middle temporal branch pierces the temporal aponeurosis
just above the zygoma, and enters the substance of the temporal
muscle : it anastomoses with the deep temporal branches of the
internal maxillary artery.

e. A small orbital branch runs forwards between the layers of the
temporal fascia, and is distributed to the superficial structures near
the eye, anastomosing with an offset of the lachrymal artery.

The temporal vein begins on the side of the head and lies
with its artery in front of the ear. Near the zygoma it is joined
by the middle temporal vein ; it then receives branches correspond-
ing to the other offsets of the artery ; and it ends by imiting with
the internal maxillary vein to form the temporo-maxillary trunk.

Dissection. The trachea and oesophagus in the neck are now
to be cleaned, but care should be taken not to injure the recurrent
laryngeal nerves or the sympathetic nerves behind and to the inner
side of the carotid sheath.

The trachea, or windjjipe, is continued from the larynx to the
thorax, and ends by dividing into two tubes (bronchi), one for each
lung. It occupies the middle line of the body, and extends com-
monly from the lower part of the sixth cervical to the lower border
of the fourth dorsal vertebra, measuring about four inches and a
half in length, and nearly one in breadth. The front and sides of
the trachea are rounded in consequence of the existence of firm

SUPERFICIAL TEMPORAL ARTERY. 607

cartilaginous bands in those parts of the wall ; but at the posterior form,
aspect the cartilages are absent, and the wall is flat and mem-
branous.

The cervical part of the trachea is very moveable, and has the Cervical
following relative position to the surrounding parts. Covering it J^^ng^t
in front are the depressor muscles of the hyoid bone, with the deep muscles
cervical fascia : beneath those muscles is the inferior thyroid plexus
of veins ; and near the larynx is the isthmus of the thyroid body.
Behind the tube is the oesophagus, with the recurrent laryngeal aud \essei.s.
nerves. On each side are the common carotid artery and the
thyroid body.

The (ESOPHAGUS, or gullet, reaches from the pharynx to the (Esophagus
stomach. It commences, like the trachea, opposite the lower part occupies
of the sixth cervical vertebra, and ends opposite the tenth dorsal J^^o^x"^*
vertebra. The tube reaches through part of the neck, and through
the whole of the thorax. Its length is about nine inches. length.

In the neck its position is behind the trachea till near the thorax Position in
where it projects to the left side of the air tube, and touches the "*^*^ '
thyroid body and the thoracic duct. Behind the oesophagus are and i-eia-
the longi colli muscles. On each side is the common carotid artery, *°°'*"
the proximity of the left being greater, in consequence of the
projection of the oesophagus towards that side.

The structure oi the oesophagus will be examined in the dissection
of the thorax.

Directions. The lower part of the neck will now be left for some
days, so that the dissector should stitch together the flaps of skin if
they remain, and carefully wrap up the part and apply preservative.

Section VII

THE PTERYGO-MAXILLARY REGION.

In this region are included the muscles superficial to and beneath Contents of
the ramus of the lower jaw, together with the temporo-maxillary ^^^ region,
articulation. In contact Avdth the muscles (pterygoid) beneath the
jaw, are the internal maxillary l.ilood-vessels, and the inferior
maxillary trunk of the fifth nerve.

Dissection. The masseter muscle, wliich is superficial to the Dissection,
bone, has been partly laid bare in the dissection of the face. To
see it more fully, the branches of the facial nerve and the transverse
facial artery should be cut through and turned backwards, and the
fascia cleaned ofl" the siu-face of the muscle.

Should there be any tow or cotton-wool left in the mouth let it
be removed.

The MASSETER (fig. 203, p. 553) rises by a flattened tendon from Masseter

the lower border of the zygomatic arch, including a small portion of OTiginf

the malar process of the superior maxilla, and by fine fleshy fibres

from the deep surfaces of the zygomatic process and the malar bone.

It is inserted into the whole of the outer surface of the coronoid and inser-
tion :

608

DISSECTION OF THE PTERYGOID REGION.

consists of
two layers ;

muscle
nearly sub-
cutaneous ;

lies on the
jaw;

To see
surface of
temporal
muscle.

To see the
insertion.

Origin of
temporal
muscle :

insertion

relatione

process and ramus of the lower jaw, extending from the angle
behind to the level of the second molar tooth in front. The
superficial fibres are inclined downwards and backwards, and form
a layer that can be readily separated from the deeper portion of
the muscle, in which the fibres run hearl}^ vertically.

The lower part of the masseter is covered only by the integu-
ments, with the platysma and fascia ; but the upper is partly con-
cealed by the parotid gland, and is crossed by Stenson's duct, and
by the transverse facial vessels and branches of the facial nerve.
The anterior border projects over the buccinator muscle, and a
quantity of loose fat resembling that in the orbit is found beneath
it. The muscle covers the ramus of the jaw, and the masseteric
nerve and artery entering its deep surface.

Action. It raises the lower jaw with the internal pterygoid in
the mastication of the food.

Dissection. To lay bare the temporal muscle to its insertion,
the following dissection is to V>e made : — The temporal fascia is to
be detached from the uj^per bolder of the zygomatic arch and
removed from the surface of the muscle. Next, the arch is to be
sawn through in front and behind, so as to include all its length ;
and is to be thrown down (without being cut oft) with the masseter
still attached to it, by separating the fibres of that muscle from the
ramus of the jaw. In detaching the masseter, its nerves and vessels,
which pass through the sigmoid notch of the lower jaw, will come
into view, and should be dissected out of the muscle.

The surface of the temporal muscle may be then cleaned. And
to expose its termination, let the coronoid process be sawn off by a
cut passing from the centre of the sigmoid notch to the last molar
tooth, so as to include the insertion of the muscle. Before sawing
the l)one let the student find and separate from the muscle the buccal
vessels and nerve issuing from beneath it anteriorly. Lastly, the
coronoid process should be raised and the fat removed, in order
that the lower fibres of the temporal muscle and their contiguity to
the external pterygoid beneath them may be seen.

The TEMPORAL MUSCLE (fig. 218, ^) ttvises from the fascia covering
it, and from the bones forming the inner wall of the temporal fossa
(p. 506), reaching upwards to the semicircular line on the side of
the skull, and downwards to the infratemporal crest on the great
wing of the sphenoid bone. From this extensive origin the fibres
converge to a tendon, which appears on the outer surface of the
muscle, and is inserted into the borders and inner surface of the
coronoid process, as well as into a groove on the front of the ramus
of the lower jaw, extending downwards nearly to the last molar tooth.

Behind the posterior border of the tendon are the masseteric
vessels and nerve, and in front of it the buccal vessels and nerve : the
last nerve occasionally perforates some of the fibres of the muscle.

Action. All the fibres contracting, the muscle will raise the
mandible and press it forcibly against the upper jaw. The hinder
fibres acting alone can retract the lower jaw after it has l)een moved
forwards by the external pterygoid.

DISSECTION OF THE PTERYGOID REGION.

609

Dissection. For the display of the pterygoid muscles (fig. 218), To dissect
it will be necessary to remove a piece of the ramus of the jaw. £cS'^
But the greater part of the temporal muscle is to be first detached
from the subjacent bone with the handle of the scalpel, and ihe deep
temporal vessels and nerves are to be sought in its fibres.

A piece of the ramus of the jaw is next to be taken away by saw through
sawing across the bone below the condyle, and close above the Jhe^jaw ;
dental foramen ; to protect the dental vessels and nerve in contact
with its inner surface while doing this, the handle of the scalpel

Fig.

218. — Superficial Vikw of the Pterygoid Region (Quain's
"Arteries").

1. Temporal muscle.

2. External pterygoid.

3. Internal pterygoid.

4. Buccinator.

5. Digastric and stylo - hyoid
muscles, cut and throwTi back.

6. Common carotid.

7. External carotid,

8. Internal maxillary artery pass-
ing beneath the external pterygoid.

may be inserted between them and the bone, and carried downwards
to their entrance into the foramen.

After the loose piece of bone has been removed, and the sub- take it away
jacent parts freed Irom fat, the pterygoid muscles will appear, — *"^ ^^^ ^^^'
the external (^) being directed backwards and outwards to the
condyle, while the internal (^), which is somewhat parallel in direc-
tion to the masseter, descends to the angle of the jaw\ In removing
the abundant fatty tissue, the student must be careful not to take
away the thin internal lateral ligament, which lies on the internal
pterygoid muscle beneath the ramus.

Position of vessels. Running forwards over the external pterygoid Position of
muscle is the internal maxillary artery, which distributes offsets

D.A. RE

610

DISSECTION OF THE PTERYGOID REGION.

Nerves.

External
pterygoid

origin ;

insertion,

relations :

use of both
muscles,

of one
muscle.

Internal
pterygoid

origin ;

insertion

contiguous
parts;

upwards and downwards : sometimes the artery is placed beneath
the muscle as in fig. 218. The veins, which form a large plexus
between the muscles, may be taken away.

Position of nerves. Most of the branches of the inferior maxillary
nerve are seen in this dissection, (fig. 219 and fig. 222, p. 616).
Thus, the masseteric and posterior and middle deep temporal nerves
appear between the upper border of the external pterygoid and the
skull, while the buccal nerve, with the anterior deep temporal nerve,
passes through the fore part of the muscle between its two heads.
Issuing from beneath the lower border of the muscle are the large
inferior dental and lingual nerves, the latter being the anterior of
the two ; and coming out behind the condyle of the jaw is the
auriculo-temporal nerve. The small posterior dental branch of the
superior maxillary nerve is also to be found, lying with the artery
of the same name on the hinder part of the upper jaw.

The EXTERNAL PTERYGOID MUSCLE (fig. 218, ^) is triangular in
shape, and arises by two heads, which are separated by an interval
opposite the spheno-maxillary fossa. The upper head is the smaller,
and is attached to the fore part of the zygomatic surface of the
great wing of the sphenoid bone ; the lower head springs from the
outer surface of the external pterygoid plate. From this origin the
muscle runs backwards and outwards to be inserted into the hollow
in front of the neck of the lower jaw-bone, and into the interarticular
fibro-cartilage of the joint.

Externally the pterygoid is concealed by the temporal muscle
and the lower jaw ; and the internal maxillary artery usually lies
on it. Its deep surface is in contact with the internal pterygoid,
the inferior maxillary nerve and its branches, and the internal lateral
ligament of the jaw. Through the interval between the heads pass
the buccal and anterior deep temporal nerves in a common stem
and the internal maxillary artery, when the latter is placed beneath
the muscle. The parts in contact with the borders of the external
pterygoid have been enumerated above.

Action. If both muscles contract, the jaw is moved directly
forw^ards, so that the lower dental arch is placed in front of the
upper ; but if one muscle act alone (say the right), the condyle of
the same side is drawn forwards, and the grinding teeth of the
lower jaw are moved obliquely to the left across those of the upper.
By the alternate action of the two muscles the trituration of the
food is mainly effected.

The INTERNAL PTERYGOID MUSCLE (fig. 218,^) crosses the direc-
tion of the external, and is nearly parallel to the ramus of the jaw.
It arises in the pterygoid fossa, mainly from the inner surface of
the external pterygoid plate, and by a small slip from the outer
surface of the tuberosity of the palate bone and the superior maxilla
in front of the pterygoid process. The fibres descend to be inserted
into a rough mark on the inner side of the ramus of the lower jaw,
extending from the inferior dental foramen to the angle.

On the muscle are placed the inferior dental and lingual nerves, the
inferior dental vessels, and the internal lateral ligament of the jaw.

THE TEMPORO-MAXILLARY JOINT.

611

Its deep surface is in relation with the superior pharyngeal constrictor
below, and the tensor palati above. The origin of this muscle
embraces the lower part of that of the external pterygoid.

Action. It acts with the masseter in raising the mandible. use.

TeMPORO MAXILLARY ARTICULATION (figS. 220 and 221, p. 612). Joint of

This articulation is a compound joint, being formed by the condyle ^^^^'■J*^-
of the lower jaw and the fore part of the glenoid cavity of the
temporal bone, with an interposed disc of tibro cartilage. The
bones are united by the following ligaments : —

The capsule is a thin membranous tube which is attached above Capsule of
to the temporal bone around the articular surface, and below to ^^"^'^ *
the condyle of the lower jaw, reaching farther down behind than
in front. The cavity in the interior is divided into two parts.

Posterior deep temporal

nerve.
Middle deep temporal

nerve.
Anterior deep temporal

nerve.

External pterj-goid :

Communication with
facial nerve.

Auriculo-temj>oral nerve.

Chorda tympani.

Lingual nerve.

luferior dental nerve.

Branch to ex-
t«rnjil pterygoid.

Long buccal nerve.

Internal pterygoid.

Fig. 219. — Diagram showing the Relations of the Branches of the
Inferior Maxillary Nerve to the Pterygoid Muscles.

upper and lower, by the fibro-cartilage ; and the upper portion of
the capsule is wider and looser than the lower.

The external lateral ligament is a thickened band of the capsule, External
composed of fibres passing from the tubercle at the root of the ^**®^'
zygoma and the adjoining part of the outer surface of that process
to the outer and posterior part of the neck of the lower jaw.

The internal lateral ligament (fig. 220, i) is a long, thin, mem- *'"i '"<^rual
branous band, which is not in contact with this joint. Superiorly ligament,
it is connected to a ridge on the inner side of the glenoid fossa,
formed by the spinous process of the sphenoid and the vaginal
process of the temporal bone ; and inferiorly it is inserted into the
inner margin of the dental foramen in the lower jaw. The
ligament lies between the jaw and the interaal pterygoid : and its
origin is concealed by the external pterygoid muscle. The internal

BR 2

612

DISSECTION OF THE PTERYGOID REGION.

Dissection.

Fibro-
cartilage

shape,

and attach-
ments ;

maxillary vessels, with the auriculo-temporal and inferior dental
nerves, pass between the band and the lainiis of the jaw.

Dissection. After the external lateral ligament and the capsule
have been examined, the interarticular fibro- cartilage will be exposed
by taking away the capsule on the outer side (fig. 221).

The interarticular fihro-cartilage (fig. 221, 4) is an oval plate,
elongated transversely, and thinner in the centre, where it is
sometimes perforated, than at the margins. The up])er surface fits
the articular hollow and eminence of the temporal bone, being
convex behind and concave in front ; and the lower is moulded to
the convexity of the condyle of the jaw. By the circumference
it is connected with the capsule ; and in front the external pterygoid
muscle is attached to it.

This interarticular disc allows a double movement to take place
in the articulation, the condyle of the jaw revolving in the socket

Fig. 220. — Ligaments op the
Jaw — Inner View (Bour-

GERY AND JaCOB).

1. Internal lateral ligament.

2. Stylo maxillary.

Fig. 221. — A View of the Interior

OF THE TeMPORO-MaXILLARY JoINT

(Bourgery and Jacob).

3. Stylo-maxillary ligament.

4. Interarticular fibre cartilage : the
dark intervals above and below the disc
are the synovial cavities.

Two syno-
vial sacs.

Stylo-
maxillary
ligament.

Surfaces of
jaw

arid tem-
poral bone.

formed by the fibro-cartilage, while the latter glides forwards and
backwards over the temporal articular surface.

Two synovial sacs are present in the articulation — a larger one
above, and a smaller one below the fi1)ro cartilage.

Another structure — the stylo-maxillary ligament (fig. 221, •^) — is
described as a uniting band to the articulation. This is a process
of the deep cervical fascia, which extends from the styloid process
to the hinder border of the ramus of the jaw ; it gives attachment
to the stylo-glossus muscle, and separates the parotid and sub-
maxillary glands.

Articular surfaces of the hones. The condyle of the jaw has a
form resembling that of a part of a cylinder, with its axis directed
obliquely from without inwards and somewhat backwards.

The upper articular surface is placed on the squamous part of

THE MOVEMENTS OF THE LOWER JAW. 613

the temporal Lone, and is larger than that on the jaw. It includes

the deep oval hollow formed by the part of the glenoid fossa

in front of the Glaserian fissure, and the convex surface, known as

the articular eminence, which forms the anterior boundary of the

hollow.

Movements of the joint. The lower jaw has up and down, forward Kinds of
JIT , 1 1 T 4. movement.

and backward, and oblique movements.

In depressing the jaw, as in opening the mouth, the condyle I" opening
moves forwards till it is placed under the convexity of the articular how condyle
eminence ; but the interposed concave fibro-cartilage gives security "lo^es.
to the joint. Even with this provision, a slight degree more of
sudden motion may throw the condyle off the prominence of the
temporal bone into the zygomatic fossa, and give rise to dis- Dislocation,
location.

In this movement the fore and lateral parts of the capsule are state of
tightened ; and the fibro-cartilage is drawn forwards with the ^^**"^^" '''
condyle by the external pterygoid muscle.

When the jaw is elevated and the mouth closed, the condyle and Shutting
the fibro cartilage glide back into the glenoid fossa ; and the
posterior part of the capsule is stretched.

During the horizontal movements forv-ards and backwards of the Forward and
jaw the condyle is placed successively opposite the front and back movement,
of the temporal articular surface ; and the fibro-cartilage always
follows the condyle of the jaw, even in dislocation.

Excessive motion forwards would be prevented by the coronoid
process of the jaw striking against the zygomatic arch ; and the
backward movement is checked by the external lateral ligament
and by the meeting of the condyle with the postglenoid process of
the temporal bone.

The oblique moveiiurit is produced by the condyle of one side Oblique
advancing on the articular eminence, while the other remains in ho^w^'"^" '
the glenoid fossa. If the right condyle advances, the chin moves produced,
to the left side, and the grinding teeth of the lower jaw are carried
obli(^iiely to the left and forwards across the upper set. By the
alternate action to opposite sides the food is triturated.

Dissection. The condyle of the jaw is next to be disarticulated Dissection

. / ^ 1 of inferior

and drawn forwards with the attached external pterygoid muscle, maxillary
so as to allow the inferior maxillary nerve to be seen (fig. 222, ^^^''^'^'
p. 616). While cutting through the joint-capsule, the dissector
must be careful of the auriculo- temporal nerve close beneath.

On turning forwards the pterygoid muscle, and removing some ^^^ trunk,
fat and veins, the dissector will find the trunk of the inferior
maxillarv nerve. The masseteric, temporal, and buccal branches ^nd

*^ brRiiCiics '

of the nerve should be traced to a common origin close below the
foramen ovale of the sphenoid bone. The dental and lingual
nerves should be cleaned beneath the muscle ; and the auriculo-
temporal nerve followed forwards with care from the back of

the articulation to its origin from the trunk. The small chorda 9^ chorda
. . tympani,

tympani is to be found joining the back of the lingual nerve near

the skull.

614

DISSECTION OF THE PTERYGOID REGION.

and arteries.

Internal
maxillary
artery :

course and
relations ;

varies in its
position.

Branches
are in three
sets.

Those be-
neath jaw.

Inferior
dental

branch to

mylo-hyoid

muscle.

Great

meningeal

artery

ends in
skull ;

but gives

branch to
tympanum,

to meatus,

The large meningeal artery and its offsets are to be sought beneath
the external pter^'goid. Sometimes the trunk of the internal
maxillary artery lies beneath that muscle, and in that case, it and
its branches are now to be cleaned.

The INTERNAL MAXILLARY ARTERY (lig. 218, ^) is one of the
terminal branches of the external carotid, and takes a winding
course beneath the lower jaw and the temporal muscle to the spheno-
maxillary fossa, where it ends in branches for the face, the interior
of the nose, and the palate and pharynx.

At first the artery is directed forwards between the ramus of the jaw
and the internal lateral ligament of the joint, and crosses the inferior
dental nerve ; it then ascends over tbe lower portion of the external
pterygoid, being placed between it and the temporal muscle ; and
finally, it turns inwards opposite the interval between the heads of
the external pterygoid to gain the spheno-maxillary fossa. The
course of the artery is sometimes lieneath, instead of over the exter-
nal pterygoid ; and when that is the case, the artery reaches the
spheno-maxillary fossa by passing between the heads of the muscle.

The BRANCHES of this artery are numerous, and are classed in
three sets ; the first set arises beneath the jaw : the second between
the muscles ; and the third in tlie spheno-maxillary fossa.

Two chief branches, viz., the inferior dental and the great menin-
geal, leave the internal maxillary artery in its first 'part while it
is in contact with the ramus of the jaw.

The INFERIOR DENTAL ARTERY descends between the internal
lateral ligament and the jaw, and enters the foramen on the inner
surface of the ramus, along with the companion nerve ; it supplies
the molar and bicuspid teeth, and ends in an incisor branch running
forwards in the bone to the incisor and canine teeth, and in a small
mental branch which issues from the bone through the foramen
of that name to end on the face.

As the artery is about to enter the foramen it furnishes a small
mylo-hyoid branch to the muscle of that name ; this is conducted by
a groove on the inner surface of the bone, in company with a branch
from the dental nerve, to the superficial surface of its muscle, where
it anastomoses with the submental artery.

The GREAT MIDDLE MENINGEAL ARTERY is the largest branch of
the internal maxillary, and arises opposite the preceding. It
ascends beneath the external pterygoid muscle, and between the
roots of the auriculo-temporal nerve to the foramen spinosum of
the sphenoid bone, through which it passes into the skull. Its
course and distribution within the cranial cavity have been already
seen (p. 514). Before the artery reaches the foramen, it usually
furnishes the following small branches ; but one or more of them
may arise directly from the internal maxillary trunk : —

a. The tympanic branch passes into the tympanum through
the Gh.serian fissure, and is distributed to the tympanic membrane
and parts within the tympanic cavity.

h. A DEEP AURICULAR BRANCH usually arises with the former,
enters the meatus through the cartilage or between that and

BRANCHES OF THE INTERNAL MAXILLARY ARTERY. 615

the bone, and ramifies in the meatus and on the tympanic
membrane.

c. The SMALL MIDDLE MENINGEAL BRANCH begins near the to dura
skull, and courses through the foramen ovale with the inferior ™^ ^^'
maxillary nerve : it ramifies in the dura mater in the middle fossa
of the s^kull.

Another small branch springs from the dental artery or from the Branch with
internal maxillary trunk, and accompanying the lingual nerve, ends ^""^"g*^
in the cheek and the mucous membrane of the mouth.

The branches from the second part of the artery (between the Branches of
temporal and external pterygoid muscles) are distributed to the Ire— ^"^
temporal, masseter, buccinator, and pterygoid muscles.

The DEEP TEMPORAL ARTERIES are two in number, anterior and to the
posterior, and ascend on the side of the skull beneath the temporal mSe^;
muscle. The posterior anastomoses with the middle temporal
branch of the superficial temporal artery ; the anterior communi-
cates, through the malar bone, with branches of the lachrymal artery.

The MASSETERIC ARTERY is directed outwards with the nerve of to the
the same name Ijehind the tendon of the temporal muscle, and
passing through the sigmoid notch, enters the deep surface of the
masseter muscle. Its branches anastomose with the other offsets
to the muscle from the external carotid trunk.

The BUCCAL BRANCH quits the artery near the upper jaw, and ^^^®
descends beneath the insertion of the temporal muscle with its com-
panion nerve : it is distributed to the buccinator muscle and other
structures of the cheek, joining branches of the facial artery.

The PTERYGOID BRANCHES are uncertain in their position and to pterygoid
number ; whether derived from the trunk or some of the branches '""^^ ^^'
of the internal maxillary, they enter the two pterygoid muscles.

Of the brandies that arise from the artery in the third part of its Branches of
course, viz. in the spheno-maxillary fossa, only one, the posterior ■ " P*
dental, will be now described. The remainder will be examined now seen
with the superior maxillary nerve and Meckel's ganglion ; they are
infra- orbital, descending palatine, spheno-palatim. Vidian, and
pterygo -pa latine.

The POSTERIOR DENTAL BRANCH arises as the artery enters the is the
spheno-maxillary fossa, and descends with a tortuous course on the dental,
zygomatic surface of the upper jaw, along with a small branch of
the superior maxillary nerve. Its branches mostly enter the canals
of the bone and supply the upper molar and bicuspid teeth, as well
as the lining membrane of the antrum ; some external offsets are
furnished to the gum.

The INTERNAL MAXILLARY VEIN is a short trunk, often double, internal

which leaves the hinder part of the pterygoid plexus, and runs back- ^^^'arises
wards, beneath the jaw with the first part of the internal maxillary from
artery, to join the superficial temporal vein in the parotid gland.

The pterygoid plexus is an extensive network of veins surrounding pterygoid
the internal maxillary artery and the pterygoid muscles. Into it ^ ^^^^^ '
the veins corresponding to the branches of the artery empty them-
selves and it communicates with the cavernous sinus in the interior tributaries,

616

DISSECTION OF THE PTERYGOID REGION.

of the skull through the foramen ovale and foramen lacerum.

From the plexus the large internal maxillary vein leads backwards,
and outlets, and another considerable branch, the anterior internal maxillary or

deep facial vein, descends to the face to join the facial vein. A

prolongation of the plexus into the spheno-maxillary fossa is often

distinguished as the alveolar plexus.
Inferior The INFERIOR MAXILLARY NERVE (fig. 222) is the largest of the

nSve.^^ three trunks arising from the Gasserian ganglion. It leaves the

Fig. 222. — Deep View of the Pterygoid Region (Illustrations of
Dissections).

Muscles :

A. Temporal reflected.

B. Condyle of the jaw disarticu-
lated forwards, with the external
pterygoid attached to it.

c. Internal pterygoid.

D. Buccinator.

F. Masseter thrown down.

Nerves :

1. Buccal.

2. Masseteric, cut.

3. Deep temporal.

4. Auriculo-temporal.

6. Chorda tympani.

7. Inferior dental.

8. Lingual.

10. Internal lateral ligament of
the lower jaw. The arteries are not
numbered with the exception of the
internal maxillary trunk, which is
marked with 9.

skull by the foramen ovale in the sphenoid bone, and divides
immediately below that opening into t\vo principal pieces, viz., an
anterior smaller part, which is distributed mainly to muscles, and
a larger posterior part, ending in branches which are, with one
exception, altogether sensory. In addition to these, the nerve of
the internal pterygoid muscle arises from the inner side of the
primary trunk.

Directions. Should the internal maxillary artery obstruct the view
of the nerve, it may be cut through.

THE INFERIOR MAXILLARY NERVE. 617

The .VNTERIOR PART receives nearly all the fibres of the motor Anterior
root of the nerve, and furnishes branches to three of the muscles of ^^^^
the jaw, viz., temporal, masseter, and external pterygoid, and the
buccal branch to the cheek (fig. 219, p. 611).

The deep temporal branches (tig. 219 and fig. 222, ^) are three in supplies
number, and enter the deep surface of the temporal muscle ; the branches,
middle, which is the largest and supplies the greater part of the middle,
muscle, leaves the anterior division of the trunk and ascends close
to the bone, above the upper border of the external pterygoid ; the
posterior is usually conjoined with the masseteric nerve, and enters posterior,
the hinder part of the muscle ; and the anterior is given off from and .
the buccal nerve in front of the external pterygoid.

The rruisseteric hranch (^) takes an outward course above the Masseteric,
external pterygoid muscle, and through the sigmoid notch, to the
under surface of the masseter muscle, in which it can be followed
to near the anterior border. As this branch passes by the articula-
tion of the jaw it gives one or more twigs to that joint.

The nerve to the external pterygoid generally arises in common Branch to
with the buccal nerve, and enters the deep surface of its muscle. pter^oid.

The buccal branch ('), longer and larger than the others, is mainly Buccal
a sensory nerve to the cheek. It is first directed forwards between sensory ;
the heads of the external pterygoid muscle, and then descends
beneath the coronoid process and the insertion of the temporal muscle
towards the angle of the mouth. After perforating the pter3^goid,
it gives off the anterior deep temporal nerve ; and on the surface of gives off
tbe buccinator it divides into branches which form a plexus ^\\th. temporal,
the buccal branches of the facial nerve, and are finally distributed
to the skin and mucous membrane of the cheek.

The POSTERIOR PART of the inferior maxillary nerve divides into Posterior
three branches — auriculo-temporal, inferior dental, and lingual ilfferior
(fig. 219). A few of the fibres of the motor root join the dental maxiiiarj'.
nerve, and are conveyed to the mylo-hyoid and digastric muscles.

The AURICULO-TEMPORAL XERVE (fig. 222, **) arises from the trunk Auricuio-
near the base of the skull, usually by two roots which embrace the ^^P*^"^
middle meningeal artery. In its course to the surface of the head,
it is first directed backwards beneath the external pterygoid muscle
as far as the neck of the jaw, and then upwards with the superficial lies beneath
temporal artery in front of the ear. Its ramifications on the head ^^^'
are described at page 504. In the part now dissected its branches and supplies
are the following :— branches

a. Branches to the meatus auditorius. Two offsets are given to to the
the meatus from the nerve l)eneath the neck of the jaw, and enter
that tube between the cartilage and bone.

b. Articular branch. The branch to the joint of the jaw arises Jo'"* of Jaw,
near the same spot as the preceding, or from the branches to the
meatus.

c. The inferior auricular branch supplies the tragus and adjacent ^^^ ^^^' ^"**
part of the pinna.

d. Parotid branches. These small filaments ramify in the gland, parotid ;

e. Communicating branches with the otic ganqlion. One or two to join otic

ganglion

618

DISSECTION OF THE PTERYGOID REGION.

and facial
nerve.

Inferior
dental

is between
pterygoid
muscles,

then in the
jaw,

and supplies

branch to
mylo-hyoid,

dental
branches to
grinding

and cutting
teeth,

branch to
lower lip.

Dental
artery
has an

incisor and

labial
branch.

Lingual
nerve

courses to
the tongue ;

no branch
here.

Chorda
tympani
joins
lingual,

filaments pass between the otic ganglion and the beginning of the
auriculo-temporal nerve.

/. Branches to the facial nerve. Two considerable branches pass
forwards round the superficial temporal artery to join the upper
trunk of the facial nerve.

The INFERIOR DENTAL ('') is the largest of the branches of the
inferior maxillary nerve. In its course to the canal in the lower
jaw, the nerve is placed behind and external to the lingual,
and lies at first beneath the external pterygoid muscle ; it after-
wards rests on the internal pterygoid, and near the dental foramen
on the internal lateral ligament. After the nerve enters the
bone, it is continued forwards beneath the teeth to the foramen
in the side of the jaw, and ends at that spot by dividing into an
incisor and a mental branch. Only one offset (to the mylo-hyoid
muscle) leaves the dental nerve before it enters the bone. Its
branches are : —

a. The mylo-hyoid nerve arises near the dental foramen, and is
continued along a groove on the inner aspect of the ramus of the
jaw to the cutaneous surface of the mylo-hyoid, and to the anterior
belly of the digastric muscle.

6. The dental branches arise in the bone, and supply the molar
and bicuspid teeth. If the bone is soft, the canal containing the
nerve may be laid open so as to expose these minute branches.

c. The incisor branch is small and continues the direction of the
nerve onwards to the middle line, furnishing offsets to the canine
and incisor teeth, below which it lies.

d. The mental or labial branch which issues on the face beneath
the depressor of the angle of the mouth has been described on
page 564.

The INFERIOR DENTAL ARTERY, after entering the lower jaw, has
a similar course and distribution to the nerve. Thus it supplies
offsets to the bone, dental l)ranches to the molar and bicuspid teeth,
and ends anteriorly in an incisor and a mental branch.

The incisor branch is continued to the symphysis of the jaAv,
where it ends in the bone ; it furnishes twigs to the canine and
incisor teeth.

The mental branch, issuing by the mental foramen, ramifies in
the structures covering the lower jaw, and anastomoses with the
branches of the facial artery.

The LINGUAL or gustatory nerve (8) is concealed at first, like
the others, by the external pterygoid muscle. It is then inclined
forwards with a small artery over the internal pterygoid, and under
cover of the side of the jaw to the tongue. The remainder of
the nerve will be seen in the dissection of the submaxillary region
(p. 623).

In its course beneath the jaw the nerve doe^ not give off any
branches, but the following communicating nerve is received by it.

The chorda tympani (6) is a branch of the facial nerve, and
leaves the tympanum by a special aperture close to the inner end
of the Glaserian fissure. Appearing from beneath the upper

THE SUBMAXILLAKY GLAND. 619

ttachinent of the internal lateral ligament of the jaw, this small
lerve joins the Ungual at an acute angle, about three-quarters of
m inch below the skull. At the point of meeting a comniuni-
;ation takes place with the lingual, but the greater part of the ends in
horda tympani is merely conducted along that nerve to the ^^'^o"®-
ongue.

The origin of this nerve, and its course across the tympanum,
vill be described in Chapter XII.

The nerve to the internal pterygoid can now be seen as it passes Branch to
>eneath the hinder border to the inner surface of its muscle, but pterygoid,
t will be more fully shown in the dissection of the otic ganglion.

Section VIII.

SUBMAXILLARY REGION.

The submaxillary region is situate between the lower jaw and parts in it.
the hyoid bone. In it are contained some of the muscles of the
hyoid bone and tongue, the vessels and nerves of the tongue, and
the sublingual and submaxillary glands.

Position. In this dissection the position of the neck is the same Position of
as lor the examination of the anterior triangle. the neck.

Dissection. If any fatty tissue has been left on the submaxillary Dissection,
land, or on the mylo-hyoid muscle, when the anterior triangular
space was dissected, let it be taken away.

The SUBMAXILLARY GLAXD (fig. 213, i\, p. 589) lies below the jaw in Submaxii-
the anterior part of the space limited by that bone and the digastric ^^^^' ^^^" '
muscle. Somewhat oval in shape, it rests on the mylo-hyoid, and '
sends a deep process round the posterior or free border of that and
muscle. In front of it is the anterior belly of the digastric ; and ^^^^^^^"^ 5
behind is the stylo-maxillarj^ ligament separating it from the
parotid. The gland is covered only by the integuments, platysma,
and deep fascia ; and the facial artery winds forwards on its deep
suiface.

In structure the submaxillary resembles the parotid gland and its structure
duct — duct of Wharton— issuing from the deep process, extends *"^ **"*^*"
beneath the mylo-hyoid muscle to the mouth.

Dissection. To see the mylo-hyoid muscle, detach the anterior Dissection,
belly of the digastric from the jaw, and dislodge without injury the
submaxillary gland from beneath the bone.

The MYLO- HYOID MUSCLE is triangular in shape, with the base at Mylo-hyoid
the jaw and the truncated apex at the hyoid bone, and unites along
the middle line with its fellow of the opposite side. It ai-ises from arises from
the mylo-hyuid ridge on the inner surface of the lower jaw as far'*^'
back as the last molar tooth ; and its posterior fibres, including about inserted
a third of the muscle, are inserted into the front of the body of the ^^^^g^^*^*^
hyoid bone, whilst the remainder blend with those of the muscle of raphe;

parts
around it

Dissection
to detach
mylo-hyoid.

To see deep
muscles saw
the jaw,

fasten
tongue,

and cut
mucous
membrane.

Define
nerves,

DISSECTION OF THE SUBMAXILLARY REGION.

the opposite side, in a median raphe between the hyoid l)one and
the jaw.

On the cutaneous surface lie the anterior belly of the digastric
muscle and the submaxillary gland, the facial artery with its submental
offset, and the mylo hyoid nerve and artery. The fibres of thc-
muscle are frequently deficient near the jaw, and allow the genio-
hyoid to be seen. Only the posterior border is unattached, and
round it a piece of the submaxillary gland winds. The parts in
contact with the deep surface of the muscle will be shown after the
undermentioned dissection has been made.

Action. The mylo-hyoid assists the digastric and genio-hyoid in
depressing the lower jaw or in elevating the hyoid bone ; but its
principal action is to raise the floor of the mouth and press the
tongue against the palate, as in the first stage of deglutition.

Dissection. To bring into view the muscles beneath the mylo-
hyoid, and to trace the vessels and nerves to the substance of the
tongue, the student should first divide the facial vessels on the jaw,,
and remove them with the superficial part of the submaxillary
gland ; but he should be careful to leave the deep part of the gland I
which turns beneath the mylo-hyoid, because the small submaxillary
ganglion is in contact with it. Next he should cut through the;
small branches of vessels and nerve on the surface of the mylo- ■
hyoid ; and detaching that muscle from the jaw, should turn it
down (as in fig. 224, p. 624), but without injuring the genio-hyoid
muscle beneath it.

Afterwards the bone is to be sawn through at the symphysis, with-
out injuring the muscles beneath it, the soft parts covering the jaw
having been first cut. The loose ramus of the jaw (for it has been
sawn in the dissection of the pterygoid region) is to be raised to see
the parts beneath, and it may be fastened up with a stitch ; but it
should not be detached from the mucous membrane of the mouth.

The apex of the tongue is now to be well pulled out of the mouth
over the upper teeth, and fastened with a stitch to the septum of the
nose, and the scalpel should be passed from below upwards between
the sawn surfaces of the bone, for the purpose of dividing a strong band
of the mucous membrane of the mouth ; and it should be carried
onwards along the middle line of the tongue to the tip.

By means of a stitch the hyoid bone may be fastened down, to
make tight the muscular fibres. All the fat and areolar tissue cover-
ing the parts under cover of the jaw are to be removed, and in doing
this the student is to take care of the Whartonian duct, of the hypo-
glossal nerve and its branches, which lie on the hypo-glossus muscle,
and especially of its small offset ascending to the stylo-glossus muscle ;
also of the lingual nerve nearer the jaw. Between the lingual nerve
and the deep part of the submaxillary gland the dissector should
seek the small submaxillary ganglion with its offsets ; and he should
endeavour to separate from the trunk of the lingual the small chorda
tym'pani nerve, and to define the offset from it to the sub-
maxillary ganglion.

PARTS BENEATH THE MYLO-HYOID. 621

At the hinder border of the hyo-glossus clean the lingual vessels, vessels,

:he stylo-hyoid ligament, and the glosso-pharyngeal nerve, all

ic passing beneath that muscle ; and at the anterior border find the

il ssuing ranine artery, which, with tlie companion vein and lingual

nerve, is to be traced on the under surface of the tongue to

the tip.

Adhering to the mucous membrane of the mouth is the sublingual and
gland, and this is to be defined, together with the sublingual artery |iand.°
which supplies it.

Parts heiuath the mylo-hyoid (fig. 224). The relative position of Parts be-
the objects covered by the mylo-hyoid is now apparent : — Extending Hyoid "^ °
from the hyoid bone to the side of the tongue is the hyo-glossus
muscle, the fibres of which are crossed superiorly by those of the above hyoid
stylo-glossus. On the hyo-glossus are placed, from below upwards, '
the hypoglossal nerve, Wharton's duct, and the lingual nerve, the
latter crossing the duct ; and near the anterior border of the muscle
the two nerves are united by branches. Beneath the same muscle
lie, from below upwards, the lingual artery, the stylo-hyoid ligament,
and the glosso-pharyngeal nerve. Above the hyo-glossus is the
mucous membrane of the mouth, with the sublingual gland attached
to it in front, and some fibres of the superior constrictor muscle
covering it behind near the jaw.

Between the chin and the hyoid bone, close to tlie middle line, is in front of
situate the genio-hyoid muscle; above this is a larger fan-shaped ^ '^'^ ^'"'"''•
muscle, the genio-glossus. Along the outer side of the last muscle
lie the ranine vessels ; and a sublingual branch for the gland of the
same name springs from the lingual artery at the anterior border of
the hyo-glossus. On the under surface of the tongue, near the
margin, lies the Ungual nerve ; and the hypoglossal nerve enters the
fibres of the genio-glossus.

The HYO-GLOSSUS MUSCLE (fig. 223,1, p. 622, and fig. 222, c), is thin Hyo-
and somewhat square in shape. It arises from the lateral part of the ^ °''^"^"
body, and from all the great cornu, of the hyoid bone. The fibres
ascend and enter the side of the tongue, extending from the base to
the tip, and they will afterwards be seen to mingle with those of the
palato- and stylo-glossus.*

The parts lying on the outer surface of the hyo-glossus, as well as parts in
those passing beneath its anterior and posterior borders, have already *^°'^^*^*' '
been enumerated ; and under the muscle there are also portions of
the genio-glossus and middle constrictor.

Action. This muscle depresses the tongue, drawing down the use.

sides and giving a rounded form to the dorsum ; and if the tongue

be protruded from the mouth, the fibres will draw it backwards into

that cavity.

The STYLOGLOSSUS (223, 2) is a slender muscle, which aiises from Stylo-
glossus

* A distinct muscular slip (cbondro-glossus), aiisiug from the small cornu
of the hyoid bone, is sometimes regarded as a part of the hyo-glossus. For
farther details respecting the anatomy of this and the other lingual muscles,
reference should be made to the Section on the Tongue.

comes to
side of
tongue ;

of one.

GeniO'
hyoid

relations ;

DISSECTION OF THE SUBMAXILLARY EEGION.

the styloid process near the apex, and from the stylo-maxillarv
ligament, and is directed downwards and forwards to the hinder part
of the lateral margin of the tongue. Here it gives some fibres to the
dorsum, but the greater part of the muscle turns to the under surface,
and is continued forwards to the tip of the tongue. Beneath the jaw
this muscle is crossed by the lingual nerve,
use of both, Action. Both muscles will raise the back of the tongue against the
roof of the mouth ; and if the tongue be protruded they will restore
it to the cavity.

One muscle can direct the point of the tongue towards its own
side of the mouth.

The GENio-HYOiD MUSCLE (fig. 223, ^) arises from the lower of the

mental spines on the innen
aspect of the symphysis off
the jaw, and is inserted intm
the front of the body of th<
hyoid bone.

The lower surface of thii
muscle is covered by th<
my lo- hyoid, and the uppei
is in contact with the genio
glossus (^). The inner horde
touches the muscle of tin
opposite side, and the two ar
often united.

Action. The genio-hyoii
either depresses the lower jaM
or raises the hyoid bone, ac-*
cording to which end is fixed I
by other muscles.

The GENio-GLOSSus (genio-
hyo - glossus, tig. 223, ^, and
fig. 224, a) is a thick, fan-
shaped muscle, having its
apex at the jaw, and its base
at the tongue. It takes origin
from the upper of the mental
spines behind the symphysis of the jaw. From this spot the fibres
radiate, the posterior passing backwards to their insertion into
the body of the hyoid bone, the anterior forwards to the tip of
the tongue, and the intermediate ones to the tongue from the
base to the tip.

Lying close to the median plane, the inner surface of the muscle
is in contact with its fellow. Its lower border corresponds to the
genio-hyoid, and the upper to the fraenum lingua?. On its outer
side are the ranine vessels, and the hyo-glossus muscle ; and the
hypoglossal nerve perforates the hinder fibres.

Action. By the simultaneous action of the whole muscle the
tongue is depressed, and hollowed along the middle. The hinder

Geiiio-
glossus ;

origin

insertion

contiguous
parts ;

Fig. 223. — Muscles of the Tongue.

1. Hyo-glossus.

2. Stylo-glossus.

3. Grenio-glossus.

4. Genio-hyoid.

.5. Stylo-pharyngeus.

THE LINGUAL VESSELS AND NERVE. 623

fibres acting alone raise the hyoid bone and protrude the tongue ;
while the anterior retract the tip of the tongue.

The LINGUAL ARTERY (fig, 217,/, p. 6(i3) arises from the external Lingual
carotid opposite the great cornu of the hyoid bone. At first it is ascends to
directed forwards above the hyoid bone, and then upwards beneath ^n^°jf"^
the hyo-glossus to the under part of the tongue (fig. 224) ; it ends at hyo-
the anterior border of that muscle in the sublingual and ranine ^ °^^^'
branches. Before it reaches the hyo-glossus, the artery forms a
small loop, with its convexity upwards, which is crossed by the
hypoglossal nerve ; and the digastric and stylo-hyoid muscles also lie
over the vessel, but are separated from it by the hyo-glossus. The
trunk rests on the middle constrictor and genio-glossus muscles. Its
branches are : —

ft. A small hyoid branch is distributed to the muscles at the upper its branches
border of the hyoid bone ; it anastomoses with its fellow of the ^^^~
opposite side, and with the hyoid branch of the superior thyroid bone ;
artery of the same side.

b. The dorsalis lingucB hTSiWch. arises beneath the hyo-glossus to back of
muscle, and ascends to supply the dorsal part of the substance of the ^ "^"^ '
tongue and the tonsil. The fibres of the hyo-glossus must be
divided to see it.

c. The sublingual branch springs from the final division of the to the sub-
artery at the edge of the hyo-glossus, and is directed outwards to the gj^^^^l
gland of the same name. Some offsets supply the gums and the con-
tiguous muscles, and one continues behind the incisor teeth to join

a similar artery from the other side.

d. The ranine branch (fig. 224, ^) is the terminal part of the lingual to the sub-
artery, and extends forwards along the outer side of the genio-glossus tongu^e.°
to the tip of the tongue where it ends. Muscular offsets are furnished

to the substance of the tongue of the same side. This artery is very
tortuous, and is embedded in the muscular fibres of the tongue.

The lingual artery is accompanied by two small vence, coraites, but Lingual
the largest vein of the tongue is the ranine, which lies external to ^^*°^'
the artery of the same name, and, after being joined by sublingual
branches, passes backwards over the hyo-glossus muscle with the
hypoglossal nerve. These veins end in the internal jugular.

The LINGUAL NERVE (fig. 224, ') has been followed in the pterygo- Lingual

maxillary region to its passage between the ramus of the lower jaw ^^^^'^

and the internal pterygoid muscle (p. 61 8). In the submaxillary region

the nerve is inclined inwards to the side of the tongue, across the along side ot

mucous membrane of the mouth and the origin of the superior con- ^^s^^

stricter muscle, and above the deep part of the submaxillary gland.

Lastly it is directed forwards below the Whartonian duct, and along

the side of the tongue to the apex. Branches are furnished to the gives

surrounding parts, thus :— branches

Two or more offsets connect it with the submaxillary ganglion, to the
*-u 1 1 f .u ^ J & o ' ganglion,

near the gland of that name.

Further forwards one or more branches descend on the hyo-glossus to twelfth
to unite in a loop with twigs of the hypoglossal nerve. nene,

624

DISSECTION OF THE SUBMAXILLARY REGION.

to mucous
membrane,

to the
papillae.

Submaxil-
lary
ganglion

Other filaments are supplied to the mucous membrane of the
mouth, the gums, and the sublingual gland.

Lastly, the branches for the tongue ascend through the muscular
substance, and are distributed to the conical and fungiform papilla}.

The SUBMAXILLARY GANGLION (fig. 224, ^) resembles the other
ganglia connected with the three trunks of the fifth nerve, and
communicates with motor, sensory, and sympathetic nerve. It lies
on the hyo-glossus muscle immediately above the deep part of th<

Fig. 224.— Deep View op the Submaxillary Reghon (Illustrations
OF Dissections).

Muscles :

Nerves :
1. Lingual.

Genio-glossus.

2. Submaxillary ganglion.

Genio hyoid.

4. Glosso-pharyngeal.

Hyo-glossus.

6. Hypoglossal.

Stylo-glossus.

7. Upper laryngeal. The lingua

Mylo-hyoid reflected.

artery is seen dividing, close to the

JH.

Stylo- hyoid.

hypoglossal nerve : the ranine offset

Posterior belly of digastric.

is marked with 9.
3. Wharton's duct.

has roots
from the
fifth, facial
and sympa-
thetic ;

gives
branches
to gland.

submaxillary gland, and is attached by two or three filaments to th(
lingual nerve.

Connection ivith nerves — roots. The fibres of the sensory root are
derived from the lingual, and of the motor root from the chorda
tynipani nerves, both joining the upper part of the ganglion. The
sympathetic root comes from the plexus on the facial artery.

Branches. From the lower part of the ganglion five or six small
offsets descend to the submaxillary gland ; and from the fore part
other filaments are given to the mucous membrane of the mouth and
to Wharton's duct.

THE HYPOGLOSSAL NERVE. 625

Chorda tympani. Joining the lingual nerve close below its f*^'^^* j .
origin (p. 618), the chorda tympani accompanies that trunk, but can destination,
be easily separated from it nearly as far as the tongue. Beyond
that point its fibres are mixed with those of the lingual nerve. Near
the submaxillary gland, an offset is sent to the submaxillary
ganglion.

The HYPOGLOSSAL or TWELFTH nerve in the submaxillary region Twelfth
is directed forwards across the lower part of the hyo-glossus muscle, Jy^^J bone?
and under cover of the mylo-hyoid. At the anterior border of the
hyo-glossus it enters the fibres of the genio-glossus, spreading out
and dividing into numerous branches as it disappears.

Branches. While resting on the hyo-glossus, the twelfth nerve its branches
furnishes offsets to the stylo-glossus, hyo-glossus and genio-hyoid* muscles
muscles, as well as one or two communicating filaments to theo^*°"8"®-
lingual nerve. Its terminal branches, within the genio-glossus,
supply that muscle and the intrinsic muscles of the tongue. The
lingual branches are long and slender, and some of them may be
traced forwards to the tip of the tongue.

The GLOSSO-PHARYNGEAL nerve (fig. 224, •*), appearing between the
two carotid arteries, courses forwards over the stylo-pharyngeus, and
ends under the hyo-glossus in branches for the tongue. (See the

DISSECTION OF THE TONGUE, p. 688).

The dud of the submaxillary gland (fig. 224, ^), Wharton's duct, Wharton's
issues from the deep part of the glandular mass turning round the
border of the mylo-hyoid muscle. About two inches in length, it is
directed upwards and forwards on the hyo-glossus muscle, and over
the lingual nerve, to open on the centre of an eminence by the side opens by
of the fraenum linguae : the opening in the mouth will be seen if a [j^JJj^^
bristle be passed along the duct. The deep part of the submaxillary
gland extends along the side of the duct, reaching, in some instances,
the sublingual gland.

The SUBLINGUAL GLAND (fig. 224, n) is an almond-shaped body sublingual

with its longest diameter, which measures about an inch and a half, g^^nd

directed from before backwards. It lies beneath the fore part of the

tongue, between the genio-glossus muscle and the lower jaw, and

resting on the mylo-hyoid. Its upper border is covered by mucous forms a

membrane, which is raised into a fold along the floor of the mouth prominence

' . . ° below

over the gland ; and its inner end touches the one of the opposite tongue,

side behind the symphysis of the jaw.

The gland consists of from ten to twenty small masses, each of and is a

which has a separate duct. The ducts (ducts of Rivinus) open for st™^°ur?

the most part on the sublingual mucous fold, but some of them join

the submaxillary duct, and one larger tube (duct of Bartholin), which

is, however, frequently wanting, springs from the deeper part of the

gland and runs forward to end either in common with, or close to,

the duct of Wharton.

* The branch to the genio-hyoid muscle is composed of fibres derived from
the cervical nerves. Compare note on p. 602.

D.A. S S

62«

Parts in this
section.

Position of
head.

Dissection

DISSECTION OF DEEP VESSELS AND NEKVES OF NECK.

Section IX.

DEEP VESSELS AND NERVES OF THE NECK.

In this Section are included the deepest styloid muscle, the
internal carotid and ascending pharyngeal arteries, and some cranial
and sympathetic nerves.

Position. The position of the part is to remain as before, viz., the
neck is to be fixed over a small block.

Dissection. To see the stylo-pharyngeus muscle, the posterior

is between
carotid
arteries :

pharyngeiS, ^elly of the digastric and the stylo-hyoid muscle should be detached
from their origin and thrown down. The trunk of the external
carotid artery is to be removed by cutting it through where the
hypoglossal nerve crosses it, and by dividing those branches that
have been already examined : any veins accompanying the arteries
are to be taken away. While cleaning the surface of the stylo-
andglosso- pharyngeus muscle, the glosso-pharyngeal nerve and its branches,
nerve."^^^ and the stylo-hyoid ligament are also to be prepared. The side of the

jaw is to be drawn forwards on the face,
stylo- The STYLO-PHARYNGEUS MUSCLE (fig. 622, =, p. 622), resembles the

pharyngeus : ^^j^^^ styloid muscles in its elongated form. The fibres arise from
origin ; ^^le root of the styloid process on the inner side, and descend between

the superior and middle constrictors to be inserted partly into the wall
insertion ; ^^ ^■^^ pharynx, and partly into the upper and hinder borders of the
thyroid cartilage.

The muscle lies below the stylo-glossus, and between the two carotid
arteries ; and the glosso-pharyngeal nerve turns over the lower end
of its flesliy belly.

Action. It raises the pharynx, and tends to dilate the part of the
cavity above the hyoid bone. From its attachment to the thyroid
cartilage it will assist in elevating and drawing backwards the
larynx.

The stylo-hyoid ligament is a slender fibrous band, which extends
from the tip of the styloid process to the small cornu of the hyoid
bone. Its position is between the stylo-glossus and stylo-pharyngeus
muscles, and over the internal carotid artery ; while the lower end
is placed beneath the hyo-glossus muscle. To its posterior border,
the middle constrictor muscle is attached below. It is frequently
cartilaginous or osseous in part of, or occasionally in all its extent.
Sometimes a slip of fleshy fibres is continued along it.

The INTERNAL CAROTID ARTERY supplies the deep parts of the
head, viz., the brain, the contents of the orbit, and the nose ; and
takes a circuitous course through and along the base of the skull
before it ends in branches to the cerebrum.

The arterial trunk in the cranium has been already learnt, and its
ophthalmic offset will be seen in the dissection of the orbit ; but the

Stylo-hyoid
ligament

lies by side
of preced-
ing.

Internal

carotid

artery.

Part already
seen.

THE INTER^'AL CAROTID ARTERY. 627

Dortion in the neck and the temporal bone remain to be dissected.

The terminal branches of the Ciirotid are examined with the brain.

Dissection i^ii- 225, p. 628). For the display of the cervical Dissection
. , ^ , . , ■,- t ^• .^ -1 -D of carotid in

[>art ot tlie artery there js now but little dissection required, tsy t^g neck ;

letachiug the styloid process at the root, and throwing it forward

with its muscles, the internal carotid artery and the jugular vein may

be followed upwards to the skull. Only a dense fascia conceals them ;

and this is to be taken away carefully, so that the branches of the

nerves may not be injured.

In the fascia, and directed forwards over the artery, seek the

glosso-pharyngeal nerve, and its branches near the skull, and the

small pharyngeal branch of the vagus lower down ; still lower, the

superior laryngeal branch of the vagus, with its external laryngeal

offset, crossing beneath the carotid. Between the vein and artery,

close to the skull, will be found the vagus, hypoglossal, and

ympathetic nerves : and crossing backwards, over or under the and of the

rein, the spinal accessory nerve. External to the vessels the loop of nerves ;

the first and second cervical nerves over the transverse process of the

atlas is to be defined ; and from it branches of communication are

to be traced to the large ganglion of the sympathetic beneath the

artery, and to the vagus and hypoglossal nerves. The dissection of

these nerves from the carotid vessels at the base of the skull is a

difficult operation in consequence of the strong investing tissue.

Ascending to the cranium, on the inner side of the carotid, the

ascending pharyngeal artery will be met with.

The INTERNAL CAROTID ARTERY (fig. 225, d) Springs from the internal

bifurcation of the common carotid trunk. It extends from the upper carotid,
border of the thyroid cartilage to the base of the skull ; then through enters the
the petrous portion of the temporal bone ; and lastly along the base ^ " "
of the skull to the anterior clinoid process, where it ends in branches
for the brain. This winding course of the artery may be divided its course
into three portions — one in the neck, another in the temporal bone, '^ ^
and a third in the cranium.

Cervical part. In the neck the artery ascends almost vertically through
from its origin to the carotid canal, and is in contact with the *^® "^^^^ '
pharynx on the inner side. The line of the common carotid artery
would mark its position in the neck. Its depth from the surface
varies like that of the external carotid ; and the digastric muscle
may be taken as the index in this difference. Thus, below that less deep
muscle, the internal carotid is overlapped by the stern o-mastoid and "^^°^'
covered by the common integuments, fascia, and platysma, and is on
the same level as the external carotid, though farther back. But
above that muscle, the vessel is placed deeply beneath the external but very
carotid artery and the parotid gland, and is crossed by the styloid *^^®P above ;
process and the stylo-pharyngeus muscle. While in the neck, the
internal carotid lies on the rectus capitis anticus major muscle, which rests on
separates it from the vertebrae. rectus.

Vein. The internal jugular vein accompanies the artery, being positjon of
contained in a sheath with it and placed on its outer side. ^'^'"'

s s 2

628

of vessels.

DISSECTION OF DEEP VESSELS AND NERVES OF NECK.

Small vessels. Below the digastric muscle the occipital artery is
directed back over the carotid ; and the offset from it to the sterno-

FiG. 225. — Deep Vesskls and Nerves op the Neck (Illustrations op
Dissections).

4. Hypoglossal.

5. Pharyngeal branch of vagus.

6. Superior laryngeal branch of
vagus.

7. External laryngeal branch of the
last.

8. Thyro-hyoid branch of hypo-
glossal.

9. Descendens cervicis, cut.

10. Phrenic.

11. Brachial plexus. Recurrent of j
the vagus winds round the subclavian]
artery, a.

Arteries :

a. Subclavian.

b. Common carotid.

c. External carotid, cut.

d. Internal carotid.

/. Inferior palatine branch of
facial.

g. Ascending pharyngeal.

Nerves :

1. Glosso-pharyngeal.

2. Spinal accessory.

3. Pneumo-gastric or vagus.

mastoid may run down on the carotid trunk. Above the digastric
the posterior auricular artery crosses the internal carotid.

THE INTERNAL JUGULAR VEIN. 629

Nerves. The piieumo-gastric is contained in the sheath at the of nerves,
back between the artery and vein, being parallel to them ; and the
sympathetic, also running longitudinally, lies behind the sheatii of
the vessels. Crossing the artery superficially, from below upwards,
are the hypoglossal, which sends its descending branch downwards
along the vessel ; next the pharyngeal branch of the vagus ; and lastly
the glosso-pharyngeal. Directed inwards beneath the carotid are the
pharyngeal offsets of the upper ganglion of the sympathetic and the
superior laryngeal nerve, the latter furnishing the external laryngeal
branch. Close to the skull, the cranial nerves of the neck are inter-
posed between the artery and the vein. Around the carotid entwine
branches of the sympathetic and offsets of the glosso-pharyngeal nerve.

The cervical portion of the artery remains much the same in size
to the end, though it is sometimes very tortuous ; and it usually
does not furnish any branch.

The PART IN THE TEMPORAL BONE is described on page 682.

The INTERNAL JUGULAR VEIN is coutinuous with the lateral sinus internal
of the skull, and extends from the jugular foramen nearly to the first ygfn ^^
rib. Behind the inner end of the clavicle it joins the subclavian to joins sub-
form the innominate vein. ^ ^^'^" '

As far as the thyroid cartilage the vein accompanies the internal is ou^ide
carotid, but below that point it is the companion to the common
carotid artery ; and it lies on the outer side of each. Its contiguity
to the artery is not equally close throughout, for near the skull there
is a small interval between them, containing the cranial nerves ;
and at the lower part of the neck there is a larger intervening space,
in which the pneumo-gastric nerve, with its cardiac branch, is found.

The size of the vein remains much the same from the skull to the enlarged
hyoid bone, where it is suddenly increased owing to the junction of y^^q. ^^^^
a number of tributaries corresponding to branches of the external
carotid artery. Its lower dilatation and its valve have been before
referred to (p. 601).

The following tributaries open into the internal jugular, viz., the branches
inferior petrosal sinus close below the skull, the pharyngeal, lingual,
facial and superior thyroid veins near the hyoid bone, and the
middle thyroid vein opposite the lower part of the larynx.

The ASCENDING PHARYNGEAL ARTERY (fig. 225, g) is a loug slender Ascending

branch of the external carotid, which arises near the beginning of aJtSy"^^^^
that vessel. It runs upwards between the internal carotid artery
and the pharynx to near the base of the skull, where it ends in ends at
pharyngeal and meningeal branches. Its offsets are numerous, but ^^"^^ "
small ; —

a. Prevertebral branches pass to the longus colli and recti antici branches
muscles, supplying also the nerves and lymphatic glands of this tebraC^^
region.

b. Pharyngeal branches supply the wall of the pharynx, the soft pharyngeal,
palate and the tonsil. The highest of these, one of the terminal
branches of the artery, ramifies in the superior constrictor, the
Eustachian tube, and the levator and tensor palati muscles : this

630

DISSEOTION OF DEEP VKSSELS AND NERVES OF NECK.

and menin-
geal.

Directions
concerning
small

branches of
the nerves.

Dissection
to open
jugular
foramen.

spinal

accessory

and

pneumo-

afterwards
glosso-
pharyngeal

and its
branches.

branch is sometimes large and furnishes the inferior pahitine artery>
instead of the facial.

c. Small muningeal branches enter the skull through the foramen
lacerum, the jugular foramen and the anterior condylar foramen.
These arteries are seldom injected.

The 'pharyngeal veins form a plexus which empties itself into the
internal jugular trunk.

Dissection of the cranial nerves in the neck. By the time
this stage of the dissection has been arrived at, the condition of the
parts will not permit the tracing of the very minute filaments of the
cranial nerves in the jugular foramen, and the parts described in the
pai-agraphs marked with an asterisk cannot be seen at present. After-
wards, if a fresh piece ol' the skull can be obtained, in which the
bone has been softened by acid and the nerves hardened in spirit,
the examination of the branches marked thus"^ may be made.

* In the jugular foramen. Supposing the dissection of the
internal carotid to be carried out as it is described at page 682, let
the student cut across with care the jugular vein near the skull.
Let him then remove bit by bit with the bone forceps, or with a
scalpel if the part has been softened, the ring of bone which bounds
externally the jugular foramen, proceeding as far forwards as the
osseous crest between that foramen and the carotid canal. Between i
the bone and the coat of the jugular vein, the small auricular branchi
of the pneumo-gastric nerve is to be found ; it is directed backwards-
to an aperture near the styloid process.

* Trace then the spinal accessory and pneumo-gastrv', nerves
through the foramen, by opening the fibrous sheath around them.
Two parts, large and small, of the spinal accessory nerve should be
defined ; the latter is to be shown joining a ganglion on the vagus,
and applying itself to the trunk of that nerve. A communication
between the two pieces of the spinal accessory is to be found. On
the pneumo-gastric is a small well-marked ganglion [ganglion of the
root\ from which the auricular branch before referred to takes
origin ; and from the ganglion filaments are to be sought passing to
the smaller portion of the spinal accessory nerve, and to the ascending
branch of the upper cervical ganglion of the sympathetic.

* Next follow the glosso-p)haryngeal nerve through the fore part
of the foramen, and take away any bone that overhangs it. This
nerve presents two ganglia as it passes from the skull (fig. 226, p, 633) ;
one (jugular), which is scarcely to be perceived, near the upper part
of the tube of membrane containing it ; the other, much lai-ger
(petrosal), is situate at the hinder border of the petrous portion of
the temporal bone. From the lower one, seek the small nerve of
Jacobson, which enters an aperture in the crest of bone between the
jugular foramen and the carotid canal, and another filament of com-
munication with the gan,L;lion of the sympathetic. Sometimes the
dissector will be able to find a filament from the lower ganglion to
join the auricular branch of the pneumo-gastric, and another to end
in the ganglion of the root of the pneumo-gastric nerve.

EXPOSURE OF THE CRANIAL NERVES. 631

Below the foramen of exit from the skull, the cranial nerves have Dissection
been for the most part denuded by the dissection of the internal nerves in
carotid ; but the intercommunications of the vagus, hypoglossal, ^^® "*"'^^ •
syin})athetic, and first two spinal nerves, near the skull, are to be
traced out more completely.

The larger part of the spinal accessory has been sufficiently laid of spinal
bare already ; but its small part is to be traced to the vagus close ^^^^^^°^y '
to the skull, and onwards along that trunk.

The chief part of the glosso- pharyngeal has also been dissected ; of glosso-
but the offsets on the carotid, and others to the pharynx in front of P^i^ryngeal ;
the artery are to be defined.

On the pneumo-gastric trunk the student will find an enlargement of vagus ;
close to the skull (ganglion of the trunk), to which the hypoglossal
nerve is intimately united. From the ganglion proceed two branches
(pharyngeal and laryngeal), which are to be traced to the parts indi-
cated by their names, especially the first which enters the pharyngeal pharyngeal
plexus. The task of exposing the ramifications of the branch of the
vagus, and those of the glosso-pharyngeal and sympathetic in the
plexus, is by no means easy, in consequence of the dense tissue in
which they are contained. Two or more cardiac offsets of the vagus, cardiac
one at the upper and another at the lower part of the neck, may be
recognised readily. Lastly, the dissector may prepare more fully ^^^ recur-
the recurrent branch coursing iip beneath the lower end of the
common carotid ; by removing the fat around it, offsets may be seen
passing to the chest and the windpipe.

Only the first, or the deep part of the hypoglossal nerve remains °[^'^'P,°;
to be made ready for learning ; its communications with the vagus,
sympathetic, and the spinal nerve are to be shown.

A dissection for the sympathetic will be given farther on (p. 636) ; °^^y™P**

but its large ganglion near the skull (upper cervical) should be part..

cleaned, and the branches from it to the pharyngeal plexus should be

pui sued beneath the carotid artery.

The ninth, tenth, and eleventh cranial nerves (glosso-pharyngeal. Ninth, tenth
'. -1 XI *u • ^ /u u andeleventh

pneumo-gastric, and spinal accessory) leave the cranium together by nerves.

the jugular foramen, from which circumstance they were formerly
grouped together as one nerve — the eighth nerve of Willis. Outside
the skull the nerves take different directions to their destination ;
thus the glosso-pharyngeal is inclined forwards to the tongue and
pharynx over the internal carotid artery ; the spinal accessory back-
wards to the sterno-mastoid and trapezius muscles over the internal
jugular vein ; and the pneumo-gastric nerve descends to the viscera
of the thorax and abdomen lying in the carotid sheath for a
considerable distance.

The GLOSSO-PHARYNGEAL NERVE (figs. 225,1 and 226,^) is the ^^os^5>-^
smallest of the three trunks. In the j ugular foramen it is placed some- nerve
what in front of the other two, and lies in a groove in the hinder
border of the petrous part of the temporal bone. In the aperture of '**^ ^y^^.
exit the nerve is marked by two ganglionic swellings, the upper one foramen,
being the jugular, and the lower the petrosal ganglion.

632 DISSECTION OF DEEP VESSELS AND NERVES OF NECK.

Its upper The jugular ganglion (fig. 226, "*) is very small, and is situate at the

upper end of the osseous groove containing the nerve. It includes
only the outer fibres of the nerve, and is not always to be recognised.

and lower The 'petrosal ganglion (^) is much larger, and encloses all the fibrils
of the nerve. Ovalish in form, it is placed in a hollow in the
posterior border of the temporal bone ; and from it spring the
branches that unite the glosso-pharyngeal with other nerves.

In the neck After the nerve has quitted the foramen, it comes forwards
between the jugular vein and the carotid artery (fig. 225, ^), and
descends over the artery until it reaches the hinder border of the

courses to stylo-pharyngeus muscle. Then curving forwards, it becomes almost
transverse in direction, crosses the stylo-pharyngeus, and finally
passes beneath the hyo-glossus nmscle, where it ends in branches to
the tongue.

Branches The branches of the glosso-pharyngeal may be classed into those

connecting it with other nerves at the base of the skull, and those
distributed in the neck.

with others, 'pjjg connecting branches arise from the petrosal ganglion ; and in this
set is the tympanic nerve.

sympathetic -x- ^ filament ascends from the sympathetic nerve in the neck to

and Tagus, . '■

join the petrosal ganglion. Sometimes there is an ofi'set from the
gan^ilion to the auricular branch of the vagus, another to the upper
ganglion of this nerve and a twig to join the branch of the facial to
the posterior belly of the digastric.

facial and -x- The tympanic branch (nerve of Jacobson ; fig. 226, "5) enters the

thetic. aperture in the ridge of bone between tiie jugular and the carotid

foramina, and ascends by a special canal to the inner wall of the
tympanum : its distribution is given with the anatomy of the
middle ear (page 812).

Distributed Branches for distribution. In the neck the branches are furnished
chiefly to the pharynx and the tongue.

pharynx, ^^ Pharyngeal branches. Two or three branches, arising from the

glosso-pharyngeal nerve as it lies over the carotid artery, descend
to join the pharyngeal branch of the vagus and take part in the
formation of the pharyngeal plexus ; and one or two smaller twigs
penetrate the superior constrictor muscle.

stylo- h. A muscular branch enters the stylo-pharyngeus while the nerve

ryngeus, .^ ^^ contact with the muscle.

tonsil, c. The tonsillitic branches supply the tonsil and the arches of the soft

palate. On the former they end in a kind of plexus — circulus tonsillaris.

and tongue. d. Lingual branches. The terminal branches of the nerve supply
the hinder part of the tongue, in connection with which they are
described (page 688).

Vagus nerve The PNEDMO-GASTRIC Or VAGUS NERVE (figs. 225,^ and 226, 2) is the
largest of the cranial nerves in the neck, and escapes through the jugu-

foramen^^ lar foramen in the same sheath of dura mater as the spiiml accessory.
In the foramen it has a distinct ganglion (gang, of the root), to which
the smaller part of the spinal accessory nerve is connected.

neo^^ ^^^^ When the nerve has left the foramen, it receives the small part of

THE PNEUMO-GASTRIC NERVE.

the spinal accessory, and swells into a ganglion nearly an inch
long (gang, of the trunk). This ganglion lies "between the internal
carotid artery and jugular vein, and communicates with several
uerves. To reach the thorax, the vagus descends almost vertically
between the internal jugular vein
and the internal and common
carotid arteries ; and it enters that
cavity, on the right side, by cross-
ing over the subclavian artery,
but beneath the innominate vein.

* The ganglion of the root
(jugular ganglion ; fig. 226,^) is of

reyish colour, and from it small
branches in the jugular foramen
arise.

The ganglion of the trunk (^) is
cylindrical in form, reddish in
colour, and nearly an inch in
length ; it communicates with the
hypoglossal, spinal, and sympa-
thetic nerves. All the intrinsic
fibres of the trunk of the nerve
enter the ganglion, but those de-
rived from the spinal accessory
nerve (^i) pass over the ganglion
without being connected to it.

The brandies of the pneumo-
gastric nerve arising in the neck
may be divided into those uniting
it with other nerves, and those
distributed to the several organs.

* Connecting branches (fig. 226)
arise from the ganglia of the root
and trunk of the vagus.

* From the ganglion of the root.
The auricular branch (Arnold's

633

courses to
the thorax.

Its upper
gaugUon,

Fig. 226.— Diagram of the Ninth,
Tenth, ani> Eleventh Nkkves.

A. Pous.

B. Medulla oblongata.

1. Grlosso pharyngeal nerve.

2. Vagus.

3. 3. Spinal accessory.

4. Jugular ganglion.

5. Petrosal ganglion.

6. Tympanic nerve.

7. Auricular branch.

8. Root-ganglion, and 9, Trunk-
ganglion of vagus.

10. Branch joining the petrous and
upper ganglion of the vagus.

11. Small part of spinal accessory.

12. Large part of spinal accessory.

13. Pharyngeal, and 14, superior
laryngeal branch of vagus.

Branches

to unite
with others ;

auricular
branch ;

nerve, ') is the chief offset, and

crosses the jugular fossa to enter

an aperture near the root of the

styloid process ; it traverses the

substance of the temporal bone,

and is distributed to the outer

ear. Its farther course will be described with the anatomy of the ear

(page 814).

* One or two short filaments unite this ganglion with the small
part of the spinal accessory nerve ; and a branch from the upper
gauglion of the sympathetic enters it. Occasionally there is an
ottset (^°) to join the petrosal ganglion of the glosso-pharyngeal nerve.

From tJie ganglion of the trunk. Communicating filaments pass

with

eleventh,
sympa-
thetic,
ninth ;

with
twelfth.

634

sympa-
thetic,
and spinal
nerves.

Branches of
supply.

To pharynx

through

pharyngeal

plexus.

Upper
branch to
larynx :

DISSECTION OF DEEP VESSELS AND NERVES OF NECK.

between it and the hypoglossal nerve. Other branches connect it t
the upper ganglion of the sympathetic and the loop of the first tw
cervical nerves.

Branches for distribution. The cervical brandies arise from th
lower ganglion and the trunk of the nerve, and are directed inward.'
to supply the pharynx, the larynx, and the heart.

a. The phary7igeal branch (fig. 225, s) springs from the nppe
part of the ganglion of the trunk, and is directed inwards over th
internal carotid artery to the side <»f the pharynx, being joined i)
its course by the descending pharyngeal branches of the glosso
pharyngeal nerve. On the surface of the middle constrictor, th'
ramifications of the united nerves communicate freely together and
with the pharyngeal branches of the sympathetic, form tin
pharyngeal plexus. The offsets of the plexus enter the wall of thi
pharynx and supply the constrictor muscles, the palato-glossus
palato-j^haryngeus, levator palati and azygos uvulfK muscles, anc
the mucous membrane between the mouth and the larynx.

b. The superior laryngeal

(fig. 225, ''') is much larger thai

its external
oflset.

Branches to
the heart,
upper and
lower.

Lower
branch to
larynx

gives
branches
to heart.

the preceding branch, and comes from the middle of the ganglion o:
the trunk. It runs obliquely downwards and forwards, passing on
the inner side of the internal and external carotids, to the interva'i
between the hyoid bone and the thyroid cartilage. Here it perforates-
the thyro-hyoid membrane, and divides into branches for the supply
of the mucous membrane of the larynx (page 697). While
beneath the internal carotid artery it furnishes the following
offset : —

The external laryngeal branch (fig. 225, ') descends on the inferioi
constrictor muscle to the side of the larynx, and then beneath the
sterno-thyroid to the crico-thyroid muscle in which it ends. Near
its origin it gives off a filament to join the upper cardiac branch of
the sympathetic ; and lower down it supplies twigs to the inferior
constrictor muscle.

c. Cardiac branches. One or two small cardiac nerves spring from
the pneumo-gastric at the ujjper part of the neck, and join cardiac
branches of the sympathetic. At the lower part of the neck, on each
side, there is a large cardiac nerve which descends into the thorax : —
the right one joins the deep nerves to the heart from the sympathetic ;.
and the left terminates in the superficial cardiac plexus.

d. The inferior or recurrent laryngeal nerve leaves the pneumo-
gastric trunk on the right side opposite the subclavian artery, audi
winding round that vessel, takes an upward course in the neck to the?
larynx, ascending beneath the common carotid artery, along the
groove between the trachea and the oesophagus, and crossing either
in front of or behind the inferior thyroid artery. At the larynx it
enters beneath the ala of the thyroid cartilage, where it will be
afterwards traced (page 697). The following branches arise from it : —

Some cardiac branches leave the nerve as it turns round the sub-
clavian artery ; these enter the thorax, and join the cardiac nerves
of the sympathetic.

THE SPINAL ACCESSORY NERVE. 635

Tracheal ami oesophageal branches spring from it as it ascends in the to trachea,
neck ; and near the larynx some filaments are furnished to the ^^ ^^^'
inferior constrictor muscle. pharynx.

On the left side the recurrent nerve arises in the thorax, opposite Left
the arch of the aorta ; in the neck it lies between the trachea and n^rve!^"
oesophagus, as on the right side, and is more frequently behind the
inferior thyroid artery.

The SPINAL ACCESSORY NERVE courses through the jugular fora- Eleventh

nerve
men with the pneumo-gastric, but is not marked by any ganglion.

The nerve is composed of two parts, a smaller one, accessory to has two

the vagus, and a larger, spinal part, which have a different origin and ^^^ ^'

distribution.

The part accessary to the vagus (bulbar part; fig. 226,") arises from Accessory
the medulla oblongata, and ends by joining the pneumo-gastric out- "^^^^"^
side the skull. In the foramen of exit it lies close to the vagus, and
is connected to the upper ganglion of that nerve by one or two
filaments. Below the foramen it passes over the lower ganglion of below
the vagus, and blends with the trunk beyond that ganglion. It ^<^*"*™^°-
gives distinct offsets to join the pharyngeal and superior laryngeal
branches of the pneumo-gastric ; and other fibres are continued into
the cardiac and recurrent laryngeal branches.

The spinal joart (fig. 226,'-), which takes its origin from the spinal Spinal part

cord, is much larger, and is connected with the smaller piece while ^° o^amen,

passing through the jugular foramen. Beyond the foramen the nerve in the neck

(fig. 225, 2) takes a backward course through the sterno-mastoid, and

across the side of the neck to end in the tiapezius : at first it is con- crosses to

cealed by the jugular vein, but it then passes either over or under ^P®^^"^'

that vessel. The connections of the nerve beyond the sterno-mastoid

have been already examined.

The nerve furnishes muscular offsets to the sterno-mastoid and to supplies
,, . . muscles,

the trapezius.

The HYPOGLOSSAL NERVE, issuing from the cranium by the Twelfth
anterior condylar foramen, is at first deeply placed between the
internal carotid artery and the jugular vein (fig. 225, ^). It next
comes forward between the vein and artery, turning round the
outer side of the vagus to which it is closely united. The nerve
now descends in the neck, and becomes superficial below the digastric
muscle in the anterior triangular space (p. 602) ; from this spot it is
directed forwards to the tongue and its muscles (p. 625).

Connecting branches. Near the skull the hypoglossal is united to branches
the lower ganglion of the vagus by filaments crossing between the ^J*gus, °
two nerves as they are iii contact.

A little lower down the nerve is joined by offsets from the sympa-
sympathetic and the loop of the first two spinal nerves. spinal'

The branches for distribution have been met with in the foregoing »^rves, and
dissections. Thus, in the neck its descending branch supplies, in muscles,
common with the spinal nerves, the depressors of the hyoid bone.
In the submaxillary region it furnishes branches to one elevator
(genio-hyoid) of the hyoid bone, to the extrinsic muscles of the

636

DISSECTION OF DEEP VESSELS AND NERVES OF NECK.

Dissection
of rectus
lateralis.

Rectus
lateralis :

parts
around

Dissection
of first
nerve.

Anterior
division of
suboccipital
nerve

lies on atlas

forms a loop
with
second :

branches.

Sympathetic
nerve iu
neck

has tla-ee
ganglia.

Other

ganglia on
fifth nerve.

Dissection
of upper
ganglion ;

tongue except the palato-glossus, and to all the intrinsic muscles of
the tongue.

Dissection. The small rectus capitis lateralis muscle, between th(
transverse process of the atlas and the base of the skull, is now to be
cleaned and learnt. At its inner border the anterior branch of th(
first cervical nerve, which forms a loop in front of the atlas, is to be
found.

The RECTUS CAPITIS LATERALIS 18 very short, and represents
posterior intertransverse muscle. It arises from the fore and uppei
part of the transverse process of the atlas, and is inserted into th(
jugular process of the occipital bone.

On the anterior surface rests the jugular vein ; and in contact with
the posterior are the obliquus superior muscle and the vertebral artery.
To the inner side lie the anterior primary branch of the fir.xt cervical
nerve and the rectus anticus minor muscle.

Action. It assists the muscles attached to the mastoid process in
inclining the head laterally.

Dissection. For the purpose of tracing backwards the anterior
branch of the first cervical nerve, divide the rectus lateralis muscle,
observing the offset to it ; then cut off the end of the transverse pro-
cess of the atlas, and remove the vertebral artery, so as to bring into
view the nerve as it lies on the first vertebra.

The ANTERIOR PRIMARY BRANCH OF THE FIRST CERVICAL, Or SUB-
OCCIPITAL, NERVE is rather smaller than the posterior, and arises from
the common trunk on the neural arch of the atlas. From that spot
it is directed forwards above the transverse process, and on the inner
side of the vertebral artery, to the interval between the rectus
lateralis and rectus anticus minor muscles. Emerging here, it bends
down in front of the transverse process of the atlas and forms a
loop with the second cervical nerve. As the nerve passes forwards
it supplies the rectus lateralis and anticus minor muscles, and
branches connect the loop with the vagus, hypoglossal and sympathetic
nerves.

Sympathetic Nerve. In the neck the sympathetic nerve consists,
on each side, of a gangliated cord, which lies close to the vertebral
column, and is continued into the thorax. On this portion of the
nerve are three ganglia— the superior near the skull, the middle
towards the lower part of the neck, and the inferior close to the first
rib. From the ganglia proceed connecting branches to the spinal
and most of the cranial nerves in the neck, and branches for
distribution to viscera and blood-vessels.

Besides the ganglia above mentioned, there are other ganglia in
the head and neck, where the sympathetic enters into connection
with the three divisions of the fifth nerve.

Dissection. To display the branches of the sympathetic nerve
greater care is necessary than in tracing the white-fibred nerves, for the
sympathetic twigs are softer, more easily torn, and generally of smaller
size. In the neck the ganglia and their branches have been partly
prepared, and only the following additional dissection will be required

THE SYMPATHETIC NERVE. 637

if to bring them into view : — The jugular vein having been cut through,
the upper ganglion will be seen by raising the carotid artery and the
trunks of the vagus and hypo-glossal nerves, and by cutting through
the branches that unite these two to the loop between the first and
second spinal nerves. The several branches of the ganglion are to be
traced upwards on the carotid artery, inwards to the pharynx, down-
wards along the neck, and outwards to other nerves.

The dissector has already seen the middle ganglion on or near the of middle;
inferior thyroid artery, and its branches to spinal nerves, and along
the neck, are now to be traced.

To obtain a view of tlie inferior ganglion the greater part of the *°'i inferior

GranglioQ.
first rib is to be taken away, and the subclavian artery is to be cut

through, internal to the scalenus anticus, and drawn aside, without,

however, destroying the fine nerves that pass over it. It is supposed

that the clavicle has been removed. The ganglion is placed close

above the neck of the first rib ; its branches are large, and are easily

followed outwards to the vertebral artery and the spinal nerves, and

downwards to the thorax.

The SUPERIOR CERVICAL GANGLION is the largest of the three, and Superior
of a reddish-grey colour. Fusiform in shape, it is as long as the near skull,
second and third cervical vertebrae, and is placed on the rectus capitis
anticiis major muscle, beneath the internal carotid artery and the beneath
contiguous cranial nerves. Branches connect the ganglion with other '^™™'
nerves ; and some are distributed to the blood-vessels, the pharynx,
and the heart.

Conitectinq branches unite the sympathetic with both the spinal and Connecting

,, . , * branches

the cranial nerves.

With the spinal nerves. The four highest spinal nerves have with spinal

branches of communication with the upper ganglion of the sym- ^''^^^'

pathetic ; but the ofi"set to the fourth nerve may come from the cord

connecting the upper to the next ganglion.

With the cranial nerves. Near the skull the lower gant^lion of the with cranial

below skull
vagus and the hypoglossal nerve are joined by branches of the sym-
pathetic. Another offset from the upper part of the ganglion ascends and in
to the jugular foramen, and divides into two filaments which join foramCTi;
the petrosal ganglion of the glosso-pharyngeal and the root-ganglion
of the vagus.

Communications are formed with several other cranial nerves by and with
means of the ascending offset from the ganglion into the carotid skulV^ ^
canal (p. 518).

Branches for dUtribution. The branches of this set are more Branches,
numerous than the preceding, and the nerves are generally of larger
size.

The ascending branch, prolonged from the upper part of the To internal
ganglion, accompanies the internal carotid artery and its branches. ^^"*^ >
Near the skull it divides into two pieces which enter the canal for
the carotid, one on each side of that vessel, and are continued to
the eyeball and the pia mater of the brain, forming secondary which join
plexuses on the ophthalmic and cerebral arteries. In the carotid n^4* •

638

DISSECTION OF DEEP VESSELS AND NERVES OF NECK.

to external
carotid,

forming
plexuses

canal communications are formed with the tympanic branch of the
glosso-pharyngeal nerve, and with the spheno-palatine ganglion ;
with the former near the lower end, and with the latter near the
upper opening of the canal. The communications and plexuses
which these nerves form in their course to the brain are described at
p. 518.

Branches for hlood-vesseh (nervi molles). These nerves surround i
the external carotid trunk, and ramify on its branches so as to form
plexuses on the arteries with the same names as the vessels : some
arufgangiia ; small ganglia are occasionally found on these slender nerves. By
means of the plexus on the facial artery the submaxillary gamglion
communicates with the sympathetic ; and through the plexus on
the internal maxillary artery the otic ganglion obtains a similar
communication.

to pharyn- The pharyngeal nerves pass inwards to the side of the pharynx^

geal plexus ; ^^^^^^ ^]^gy j^jj-^ ^-j|-}^ ^|jg branches of the glosso-pharyngeal an(

pneumo-gastric nerves in the pharyngeal plexus.

Cardiac nerves enter the thorax to join in the plexuses of the
heart. There are three cardiac nerves on each side, viz., superiorJ
middle, and inferior, each taking its name from the ganglion
which it is an offset.

The superior or superficial cardiac nerve of the right side cours
behind the sheath of the carotid vessels, and enters the thorax along
the innominate artery. In the neck the nerve is connected with
the cardiac branch of the vagus, with the external laryngeal, and
with the recurrent nerve. In some bodies it ends by joining one
of the other cardiac nerves.

The MIDDLE CERVICAL or THYROID GANGLION is of Small size,
and is situate beneath the great vessels, usually opposite the sixth
cervical vertebra, on or near the inferior thyroid artery. Its
branches are the following : —

Connecting branches with the spinal nerves sink between the
borders of the longus colli and anterior scalenus to join the fifth
and sixth cervical nerves.

A considerable branch passes between the middle and inferior
loop to lower cervical ganglia, forming a loop (ansa Vieussenii) over the front of
the subclavian artery, and sui3plying it with filaments.

Branches for distribution. These consist of nerves to the thyroid
body, together with the middle cardiac nerve.

The thyroid branches ramify around the inferior thyroid artery,
and end in the thyroid body ; they join the external and recurrent
laryngeal nerves.

The middle or great cardiac nerve descends to the thorax across
the subclavian artery ; its termination in the cardiac plexus has been
learnt in the chest (p. 473). In the neck it communicates with the
upper cardiac and recurrent laryngeal nerves.

The INFERIOR CERVICAL GANGLION IS of large size, but irregular
in shape, and lies over the interval between the first rib and the
transverse process of the last cervical vertebra, its position being

to cardiac
plexuses ;

superficial

cardiac

nervo.

Middle
ganglion

joined to
spinal
nerves ;

ganglion ;

branches of
distribution

thyroid
branches,

middle
cardiac
nerve

Inferior
ganglion

THE INFERIOR CERVICAL GANGLION. 639

iternal to the superior intercostal artery. Oftentimes it extends on neck of
; a front of the neck of the lib, and joins the first ganglion of the
ord in the thorax. Its branches are similar to those of the other
wo ganglia.

Gonnectmg hranclus ]o\n the last two cervical nerves. Other Branches to
lerves acconipany the vertebral artery, forming the xertehral plexus nerves and
round it, and communicating with the cervical nerves. Irtery^^

Only one branch for distribution, the inferior cardiac neive, issues and inferior
rom the lower ganglion. It lies beneath the subclavian artery,
oining in that position the recurrent laryngeal nerve, and enters
he thorax to terminate in the deep cardiac plexus behind the arch
)f the aorta.

Directions. The student will now observe, so far as they are left, Directions,
the structures in the upper opening of the thorax, and will then pro-
ceed to the dissection of the orbit whilst the skull is whole, in the
meantime carefully wrapping up and treating with preservative the
parts left in the neck.

Parts in the upper aperture of the thorax (fig. 171, p. 467). Parts inthe

The relative position of the several parts entering or leaving the thorax.'^ °
thorax by the upper opening may be now observed.

In the middle line lie the remains of the thymus gland, and the in middle
trachea and oesophagus. In front of the trachea are the lower ends '"^"
of the sterno-hyoid and sterno-thyroid muscles with layers of the
cervical fascia, and the inferior thyroid veins ; and behind the gullet
and windpipe are the longi colli muscles. Between the two tubes
is the recurrent nerve on the left side.

On each side the dome of the pleura and the apex of the lung On each
project into the neck ; and in the interval between the pleura and ^^^^•
the trachea and oesophagus, are placed the vessels and nerves passing
between the thorax and the neck. Most anteriorly on both sides partly the
lie the innominate vein, the phrenic nerve, and the internal mam- i^th Sdes,
mary artery ; but the vessels and nerves next met with are different and partly
on the two sides : — On the right side are the innominate artery, ^^^*^'^°*^-
with the vagus, the cardiac nerves and the right lymphatic duct.
On the left side are the left vagus, the left common carotid artery,
the thoracic duct and the left subclavian artery with the cardiac
nerves. Lastly, altogether behind on each side are part of the first
dorsal nerve, the cord of the sympathetic, and the superior intercostal
artery.

Section X.

DISSECTION OF THE ORBIT.

Position. In the examination of this cavity the head is to be Position of
placed in the same position as for the dissection of the sinuses of the *^®^^**^-
base of the skull.

Dissection. The cotton- wool beneath the eyelids should be taken How to open
away, and the bone forming the roof of the orbit may be removed in with ^

the orbit
saw,

640

DISSECTION OF THE ORBIT.

chisel,

and bone
forceps.

Periosteum
of orbit.

Open
periosteum.

Position of

parts

exposed.

Trace super-
ficial nerves

Orbit has
seven
muscles :

the following maimer. Two cuts are to be made with the saw through
the frontal bone, the inner one vertically over the internal margin of
the anterior opening of the orbit, and the outer one, commencing
behind the temporal crest, obliquely downwards and inwards, to
the external angular process : then with a chisel these are to be
continued backwards along the roof of the orbit, so as to meet near
the optic foramen. The piece of bone included between the incisions
is now to be tilted forwards, but is not to be taken away. This can
be done by knocking forwards the piece of frontal bone between the
saw-cuts with a mallet, and the orbital plate of the bone will be
carried upwards from the periosteum beneath.

Afterwards the rest of the roof of the orbit, which is formed by
the small wing of the sphenoid bone, is to be cut away with the
bone forceps, except a narrow ring around the optic foramen ; and
any overhanging bone, which may interfere with the dissection,
should be likewise removed. During the examination of the cavity
the eye is to be pulled gently forwards.

The 'periosteum of the orbit is now seen where it has been detached
from the bone in the dissection. This membrane forms a sac around
the contents of the orbit which is continuous posteriorly with the
dura mater through the sphenoidal fissure and the optic foramen, and
is closed in front by the palpebral fascia passing from it to the lids.
It adheres but loosely to the bones, and is perforated behind by
apertures for the passage of the vessels and nerves entering the orbit.
On the sides, prolongations of the membrane accompany the vessels
and nerves leaving the cavity.

Dissection. The periosteum is next to be divided along the
middle of the orbit, and to be taken away. After the removal of a
little fat, the following nerves, vessels, and muscles come into view
(fig. 227, p. 642) ; but it is not needful to remove much of the fat at
this stage of the dissection.

The frontal nerve and the supraorbital artery are placed in the
centre ; the lachrymal nerve and vessels close to the outer wall ;
and the ^T\\a\\ fourth nerve at the back of the orbit : all these nerves
are above the muscles in the cavity. The superior oblique muscle
lies on the inner side, and is recognised by the fourth nerve entering
its upper aspect ; the levator palpebrm and superior rectus are beneath
the frontal nerve ; and the external rectus is partly seen below the
lachrymal nerve. At the outer part of the orbit, near the front, is
the lachrymal gland.

The frontal and lachrymal nerves should be followed forwards
to their exit from the orbit, and backwards, with the fourth
nerve, through the sphenoidal fissure, to the wall of the cavernous
sinus. In tracing them back, it will be expedient to remove the
projecting anterior clinoid process, should this still remain ; and
some care will be required to follow the lachrymal nerve to its
commencement.

Contents of the orbit. The eyeball, the lachrymal gland, and a
quantity of granular fat, are lodged in the orbit. Connected with

THE LACHRYMAL GLAND. 611

the eye are six iiiiiscles — four straight and two oblique ; and there is
also an elevator of the upper eyelid in the cavity.

The nerves in the cavity are numerous, viz., the second, third, several era-
fourth, ophthalmic of the fifth, and the sixth, together with the small ^^^^ °«^^^« '
temporo-malar branch of the superior maxillary nerve, and offsets of
the sympathetic : their general distribution is as follows : — The
second nerve enters the eyeball ; the third supplies all the muscles their distri-
of the cavity but two ; the fourth enters the superior oblique ; and ^"^*°^ '
the sixth is spent in the external rectus muscle. The fifth nerve
supplies some filaments to the eyeball with the sympathetic, but the
greater number of its branches pass through the orbital cavity to the and some
face. The ophthalmic vessels are also contained in the orbit. vessels.

The LACHRYMAL GLAND (fig. 227, f) secretes the tears, and is Lachrymal
situate in the hollow on the inner side of the external angular process futer part
of the frontal bone. It is of an oval form, something like a small of orbit,
almond, and measures about three-quarters of an inch in its longest
diameter, which is directed transversely. From its fore part a thin
accessory piece projects beneath the upper eyelid. The upper
surface is convex, and in contact with the periosteum, to which it
is connected by fibrous bands that constitute a ligament for the
gland ; the lower surface rests on the eyeball and the external rectus
muscle.

The gland has from eight to twelve very fine ducts, which open on Ducts open
the surface of the conjunctiva in a curved line above the outer part behind
of the upper eyelid, and a little in front of the fornix. eyelid.

The FOURTH NERVE (fig. 227, ') is the most internal of the three Fourth
nerves entering the orbit above the muscles. In the cavity, it is "^'"^'^
directed inwards above the levator palpebrae to the superior oblique supplies
muscle, which it pierces on the upper, or orbital surface. obnaue"^

The OPHTHALMIC TRUNK of the fifth nerve as it approaches ophthalmic
the sphenoidal fissure, furnishes from its inner side the nasal branch, gives three

DrciiiCiics

and then divides into the frontal and lachrymal branches ; the
first passes into the orbit between the heads of the external rectus,
but the other two lie, as before said, above the muscles.

Tlie frontal nerve (fig. 227, ^) is close to the outer side of the fourth Frontal
as it enters the orbit, and is much larger than the lachrymal branch.
In the course to the forehead the nerve lies along the middle of the divides into
orbit ; and after giving off" from its inner side the mipratrochlear and^i^pra-^
branch (^), it leaves the cavity by the supraorbital notch. Taking the trochlear,
name supraorbital, it ascends on the forehead, where it is distributed.
This nerve frequently divides into its two main branches (p. 504)
while still within the orbit.

While in the notch the supraorbital nerve gives one or t\iO palpebral Palpebral
filaments to the upper lid. filaments.

The supratrochlear nerve {*) passes inwards above the pulley of the supra-
upper oblique muscle, and leaves the orbit to end in the eyelid and jj.^^^^^
forehead (p. 504). Before the nerve turns round the margin of the
frontal bone, it sends downwards a twig of communication to the
infratrochlear branch of the nasal nerve.

D.A. TT

642

Lachrymal
nerve

ends in
eyelid :

offset joins

superior

maxillary.

DISSECTION OF THE ORBIT.

The lachrymal nerve (fig. 227, ^) after entering the orbit in ;
separate canal of the dura mater, is directed forwards in the oute
part of the cavity, and beneath the lachrymal gland in the nppe
eyelid, where it pierces the palpebral fascia, and is distributed to th<
structures of the lid.

The nerve furnishes branches to the Uxchrymal gland ; and nea:

Fig. 227.— First View of the Oubit (Illustrations of Dissections).

Muscles: Nerves:

A. Superior oblique. l. Fourth.

B. Levator palpebrse.
c. External rectus.
D. Superior rectus.
F. Lachrymal gland.

2. Frontal.

3. Lachrymal.

4. Supratrochlear.

6. Offset of lachrymal
temporo-malar.

to join

Nasal, after-
wards.

Dissection.

the gland it sends downwards one or two small filaments («) to join
the temporo-mahir branch of the superior maxillary nerve.

The nasal nerve is not fully seen at this stage of the dissection, and
will be noticed later (p. 644).

Dissection. Divide the frontal nerve about its middle, and throw
the ends forwards and backwards : by raising the posterior piece
of the nerve, the separate origin of the nasal branch from the

MUSCLES OF THE ORBIT. 643

ophthalmic trunk will appear. The lachrymal nerve may remain
uncut.

The LEVATOR PALPEBR^ SUPERIORIS (fig. 227, B) is the most super- Elevator of

ficial muscle, and is attached posteriorly to the roof of the orbit in "yJiid
front of the optic foramen. The muscle widens in front, and bends
downwards in the upper eyelid to be mainly inserted by a broad attached to
tendon into the front of the tarsal plate. Expansions from the tendon
can be traced to the tissues over the eyebrow and at tlie root of the
upper lid.

By one surface the muscle is in contact with the frontal nerve relations;
and the periosteum; and by the other with the superior rectus
muscle. If it is cut across about the middle, a small branch of the
third nerve will be seen entering the posterior half on the under
surface.

Action. The lid is made to glide upwards over the ball by this use.
muscle, so that the upper edge is directed back and the lower
forwards, the skin above the lid being folded inwards at the same
time.

The SUPERIOR RECTUS (fig. 227, d) is the upper of four muscles Upper i-ec-
that lie around the globe of the eye. It arises from the upper ^"^ '""^^^^ *
pail of the optic foramen, and is connected with the otlier recti °"^''^'
muscles around the optic nerve. In front the fleshy fibres end in iusertion ;
a tendon, which is inserted^ like the other recti, into the sclerotic
coat of the eyeball about a quarter of an inch behind the transparent
cornea.

The under surface of the muscle is in contact with the globe of the position to
eye, and with some vessels and nerves to be afterwards seen; the ° er parts;
upper surface is partly covered by the preceding muscle. The action use.
of the muscle will be given with the other recti (p. 650).

The SUPERIOR OBLIQUE MUSCLE (fig. 227, a) is thin and narrow, upper
and passes through a fibro-cartilaginous loop at the inner angle of o^^iq^e

r n o JT o muscle

the orbit before reaching the eyeball. The muscle arises behind

from the upper and inner part of the optic foramen, and ends

anteriorly in a rounded tendon, which, after passing through the loop,

or pulley, referred to, is reflected backwards and outwards between traverses a

the superior rectus and the globe of the eye to be inserted into the ^^ ^^ '

sclerotic coat behind the middle of the ball. "^ ^ '"° '

The fourth nerve is supplied to the orbital surface of the muscle relations:
and the nasal nerve lies below it. The thin insertion of the muscle
lies between the superior and the external recti, and near the tendon
I of the inferior oblique.

The 'pulley^ or trochlea (fig. 228, p. 645), is a fibro-cartilaginous ring pulley of
about one-sixth of an inch wide, which is attached by fibrous tissue
to the depression of the frontal bone at the inner angle of the orbit.
A fibrous layer is prolonged from the margin of the pulley on to
the tendon ; and a synovial sheath lines the ring, to facilitate the
movement of the tendon through it. To see the synovial sheath
and the free motion of the tendon, this prolongation may be cut
away.

T T 2

644

DISSECTION OF THE ORBIT.

Dissection.

For the use of the muscle, see the description of the inferior
oblique (p. 650).

Dissection (fig- 228). The suj^erior rectus muscle is next to be
divided about the middle and turned backwards when a branch of
the third nerve to its under surface will be found. At the same time
the nasal nerve and the ophthalmic vessels will come into view as they
cross inwards above the optic nerve ; these should be traced forwards
to the inner angle, and backwards to the posterior part of the orbit.

By taking away the fat between the optic nerve and the external
rectus, at the back of the orbit, the student will find easily fine
nerves {ciliary) with small arteries lying along the side of the optic
nerve ; and by tracing these ciliary nerves backwards, he will bf
guided to the small lenticular ganglion (the size of a pin's head).
The dissector should find then two branches from the nasal am
third nerves to the ganglion : the nasal branch is slender, and enters
the ganglion behind ; while that of the third nerve, short and thick
Joins the lower part.

The eyeball is to be fully exposed by dissecting off its investing
fascia (capsule of Tenon), which will be seen to send processei
around the several muscles inserted into the sclerotic.

Lastly, the student should separate from one another the nasalj
third, and sixth nerves, as they pass between the heads of th<
external rectus muscle into the orbit.

The THIRD NERVE is placed highest in the wall of the cavernous

sinus; but at the sphenoidal fifsure it descends below the fourth,

and the two superficial branches (frontal and lachrymal) of the

as it enters ophthalmic nerve. It comes into the orbit between the heads of the

outer rectus, having previously divided into parts.

The iipper division (fig. 228, ^) is the smaller, and ends in the under
surface of the levator palpebrse and superior rectus muscles.

The lower division supplies the internal and inferior recti and the
inferior oblique muscles, and will be dissected afterwards (p. 648).

The NASAL BRANCH OP THE OPHTHALMIC NERVE (fig. 228, 1) enters

the orbit between the heads of the external rectus, lying between
the two parts of the third nerve, and is then directed obliquely
inwards to reach the anterior of the two internal orbital canals.
Passing through this aperture with the anterior ethmoidal artery,
the nerve appears in the cranium at the outer margin of the
cribriform plate of the ethmoid bone. Finally, it enters the nasal
cavity by an aperture at the front of the cribriform plate ; and after
passing behind the nasal bone, it issues between that bone and the
cartilage, to end on the outer surface of the nose.

In the orbit the nasal crosses over the optic nerve, but beneath
the superior rectus and levator palpebrce muscles, and lies afterwards
below the superior oblique ; in this part of its course it furnishes
the following branches : —

The branch to the lenticular ganglion (») is about half an inch long
and very slender, and arises as soon as the nerve comes into the
orbit : this is the long root of the lenticular ganglion.

Find len-
ticular
ganglion,

and roots.

Clean
eyeball

Separate
nerves.

Third nerve

orbit

its upper
branch,

lower
branch.

Nasal nerve.

General
course to
the face.

In the orbit.

THE NASAL NERVE.

645

Long ciliary nerves. As the nasal crosses the optic nerve, it Long ciliary
supplies two or more ciliary branches (fig. 228, 7) to the eyeball. ^^^ ^^'
These lie on the inner side of the optic nerve, and join the ciliary
branches of the lenticular ganglion.

The infratrochlear branch {^) arises as the nasal nerve is about infra-
to leave the cavity, and is directed forwards below the pulley of the branch*'^

Fig. 228. — Second View of the Orbit (Illpstrations op Dissections).

Muscles :

A. Superior oblique.

B. Levator palpehrse and upper
rectus thrown back together.

0. External rectus.
B. Fore part, of upper rectus.
F. Lachrymal gland.

Nerves :

1. Nasal.

2. Its infratrochlear branch.

3. Lenticular ganglion : — 4, its
short root ; 5, its long root (too
large).

6. Branch of third to inferior
oblique muscle.

7. Ciliary branches of the nasal
nerve.

8. Upper branch of the third.

9. Sixth nerve.

10. Third nerve, outside the
orbit.

superior oblique muscle, to end in the upper eyelid, the conjunctiva,
and the side of the nose. Before this branch leaves the orbit it
receives an offset of communication from the supratrochlear nerve.

In the nose (fig. 239, s, p. 675). While in the nasal cavity the nerve Nasal nerve
furnishes branches to the lining membrane of the septum and outer '

wall ; and these will be subsequently referred to with the nerves of
the nose (p. 677).

6^6

DISSECTION OF THE ORBIT.

and in the
face.

Lenticular
ganglion :

situation

connec-
tions.

Three roots
long,

short,

and sym-
pathetic.

Ciliary
branches to
eyeball.

Ophthalmic
artery,

in the orbit.

Branches :

general dis-
tribution.

Branch to
retina.

Ciliary
arteries are

posterior —

two named
long ciliary,

Termination of the nasal nerve. After the nerve becomes
cutaneous on the side of the nose, it descends beneath the com-
pressor naris muscle, and ends in the integuments of the tip of^
the nose.

The OPHTHALMIC OF LENTicuLA'R GANGLION (fig. 228, ^) is a sniallj
reddish body, about the size of a pin's head, and in form nearly!
square. It is placed at the back of the orbit between the optic]
nerve and the external rectus, and commonly on the outer side
of, and close to, the ophthalmic artery. By its posterior part the
ganglion has branches of communication with other nerves (its
roots) ; and from the anterior part proceed ciliary branches to the
eyeball. The ganglion receives roots from sensory, motor, and
sympathetic nerves.

The branches of communication are three in number. One, the
long root ("), is the branch of the nasal nerve before noticed, which
joins the superior angle. A second branch of considerable thickness,
the short root (**), passes to the inferior angle from the branch of the
third nerve that supplies the inferior oblique muscle. And the
sympathetic root is derived from the cavernous plexus, either in union
with the long root, or as a distinct branch to the posterior border of
the ganglion.

Branches. The short ciliary nerves (fig. 228), ten or twelve in
number, are collected into two bundles, which leave the u])per and
lower angles at the front of the ganglion. In the upper bundle are
four or five, and in the lower, six or seven nerves. In their course
to the eyeball they lie along the outer and under parts of the optic
nerve, and communicate with the long ciliary branches of the nasal
nerve.

The OPHTHALMIC ARTERY (fig. 229), a branch of the internal
carotid, enters the orbit through the optic foramen. At first the
vessel is below and to the outer side of the optic nerve, but it then
courses inwards over (or occasionally under) the nerve to the inner
side of the orbit, and finally perforates the palpebral fascia above the
internal tarsal ligament to end by dividing into frontal and nasal
branches.

The BRANCHES of the artery are numerous, though inconsiderable
in size. They supply the structures within the orbit, and some
leave that cavity to be distributed to the lining membrane of the
cranium, to the interior and exterior of the nose, and to the adjoin-
ing part of the forehead.

The central artery of the retina is a very small branch which pierces
the optic nerve about half an inch behind the eyeball.

The ciliary branches are divided into anterior and posterior, which
enter the eyeball at the front and back : —

T\\^ -posterior ciliary usually rise by two trunks — inner and outer,
close to the optic foramen : they divide into a number of branches
(from ten to twenty) which run to the eyeball around the optic nerve,
and perforate the sclerotic coat at the posterior part Two of this set
(one on each side of the optic nerve), are named long ciliary and

THE OPHTHALMIC ARTERY.

647

pierce the sclerotic farther out than the others, and lie along the
middle of the eyeball.

The antenor ciliary arteries arise from muscular branches of the*°4*"-
ophthalmic, and perforate the sclerotic coat near the cornea : in the
eyeball they anastomose with the long ciliary. For the ending of
these vessels, see the dissection of the eyeball, pp. 797 and 798.

The lachrymal artei-y accompanies the nerve of the same name to Lachrymal
the upper eyelid, where it ends by supplying that part, and joining ^
in the arches in the eyelids. It supplies branches, like the
nerve, to the lachrymal gland and the conjunctiva : and it communi- *« g'and and

eyelids

Nasal.

Lachrymal
gland.

LachrjTnal.

Branch to outer
side of orbit.

Communication with middle
meningeal.

External rectus

Anterior meningeal.
Frontal.

Anterior ethmoidal.

Posterior ethmoidal.

Supraorbital.
Posterior ciliary, outer

trunk.
Posterior ciliary, inner

trunk.
Internal rectus.
Superior oblique.
Central artery of retina.

Superior rectus turned
back.

Fig. 229. — Diagram of the Ophthalmic Artery and its Branches.

offsets
through
malar bone.

Supraorbi-
tal branch.

cates with the large middle meningeal artery by an offset through the
sphenoidal fissure.

The lachrymal artery also sends twigs to the external rectus
muscle, and a small branch with each of the di\dsions of the
temporo-malar nerve ;• these join the temporal and transverse facial
arteries.

Tiie supraorbital branch is small, and arises as the artery is
crossing the optic nerve. It takes the course of the nerve of the
same name through the notch in the margin of the orbit, and ends
in branches on the forehead.

The muscular branches are a supei-ior to the upper and outer Muscular,
muscles, and an inferior to the lower and inner muscles, as well as
small irregular offsets.

The ethmoidal branches are two, anterior and posterior, and are Ethmoida
directed through the canals in the inner wall of the orbit : — branches,

The posterior is the smaller of the two, and often arises in common posterior

648

DISSECTION OF THE ORBIT.

and an-
terior.

Branches
to eyelids.

Frontal
branch.

Nasal
branch.

Ophthalmic
veins :

superior

and inferior.

Optic nerve

ends in
retina.

Dissection.

Lower
division of
third nerve

supplies
muscles,

and joins
ganglion,

witli the supraorbital artery. It ends in offsets to the mucous
membrane of the upper part of the nose and the ethmoidal cells.

The anterior branch (internal nasal) accompanies the nasal nerve to
the cavity of the nose, and gives anterior meningeal offsets to tlie
fore part of the falx cerebri and the dura mater of the anterior fossai
of the skull.

The palpebral branches, one for each eyelid, generally rise togethe:
opposite the pulley of the superior oblique muscle, and then separate
from one another. The arches they form have been dissected with
the eyelids (p. 569). m

The frontal branch turns round the margin of the orbit, and i«
distributed on the forehead (p. 503).

The nasal branch (external) supplies the skin and muscles of the
upper part of the nose, and anastomoses with the angular and lateral
nasal branches of the facial artery.

The OPHTHALMIC VEINS are two in number, superior and inferior,
and leave the orbit by the sphenoidal fissure, between the heads of
the external rectus, to end in the cavernous sinus. The superior vein
is the larger and accompanies the artery : it begins in front by
a wide communication with the angular vein, and on its way back-
wards it receives tributaries corresponding to most of the offsets of
the artery. The inferior vein lies below the optic nerve, and is
formed by the lower ciliary and muscular veins ; it communicates
through the spheno-maxillary fissure with the pterygoid plexus.
The supraorbital, frontal and palpebral veins do not join the oph-
thalmic, but pass to the veins of the face.

The OPTIC NERVE in the orbit extends from the optic foramen to
the back of the eyeball. As the nerve leaves the foramen it is sur-
rounded by the recti muscles; and beyond that spot the ciliary
arteries and nerves entwine around it. It terminates in the retinal
expansion of the eye.

Dissection (fig. 230). Take away the ophthalmic vessels, and
divide the optic nerve about its middle, together with the small
ciliary vessels and nerves. Turn forwards the eyeball, and fasten
it in that position with hooks. On removing some fat the three
recti muscles — inner, inferior, and outer, will appear ; and lying on
the first two are the offsets of the lower division of the third nerve.

The LOWER DIVISION OF THE THIRD NERVE (fig. 230) supplies

three muscles in the orbit. As it enters this space, between the
heads of the external rectus, it lies below the nasal, and rather above
the sixth nerve. Almost immediately the nerve divides into three
branches. One (°) passes to the internal, another (^) to the inferior
rectus, both entering the muscles on their ocular surfaces, and the
third (3), the longest and most external, is continued forwards to the
inferior oblique muscle, which it pierces at its hinder border.

Soon after its origin the last branch communicates with the
lenticular ganglion, forming the short root (fig. 228, ^) of that body ;
and it furnishes two or more filaments to the inferior rectus
muscle.

THE RECTI MUSCLES.

6A9

The SIXTH NERVE (tig. 230, '^) lies below the other nerves, and Sixth nerve,
above the ophthalmic veins, in the interval between the heads of
the external rectus. In the orbit it first lies against, and then
penetrates the inner surface of the external rectus muscle.

Recti Muscles. The internal (fig. 230, d), inferior (c), and external straight
recti {b) are placed with reference to the eyeball as their names "^"b^a'ff.'^^
express. They arise posteriorly from the circumference of the optic origin.

Fig. 230. — Third View of the Orbit (Illustrations of Dissections).

Muscles :

A. Upper rectus and levator pal-
pebrse thrown back together.

B. External rectus,
c. Inferior rectus.
D. Internal rectus.

F. Superior oblique cut, showing
the insertion.

H. Insertion of inferior oblique.

Nerves :

1. Upper branch of the third.

2. Sixth nerve.

8. Branch
oblique.

4. Branch
rectus.

5. Branch
rectus.

of third to

iferior

of third to inferior
of third to internal

foramen by a common attachment, which partly surrounds the optic
nerve. The external rectus differs from the others in having two External
heads : the upper one arises on the outer margin of the optic foramen headl-
and joins the superior rectus in the common origin : the lower and
larger head blends on the one side with the inferior rectus in the
common origin, and on the other side is attached to a bony point on
the lower border of the sphenoidal fissure near the inner end, while
some of its muscular fibres are also connected with a tendinous band

650

Between
heads of
outer rectus.

Use of all

inner and
outer,

upper and
lower,

and two
adjacent.

Common
tendinous
origin of
the recti.

Dissect
inferior
oblique.

Lower
oblique
muscle :

origin ;
course ;

insertion ;
relations.

A(ition of
oblique
muscles :
alone,

DISSECTION OF THE ORBIT.

between tlie two heads. All the muscles are directed forwards, the
lower ones also obliquely outwards, and have a tendinous insertion
into the ball of the eye about a quarter of an inch from the cornea,
and in front of the greatest transverse diameter of the ball.

Between the heads of origin of the external rectus, the different
nerves before mentioned are transmitted into the orbit, viz., the
third, the nasal branch of the fifth, and the sixth, together with the
ophthalmic veins.

Action. The four recti muscles are attached to the eyeball at
opposite sides in front of the greatest transverse diameter and are
able to turn the pupil in opposite directions.

The inner and the outer muscles move the ball horizontally
around a vertical axis, the former directing the pupil towards the
nose and the latter towards the temple.

The upper and lower recti elevate and depress respectively the
fore part of the ball around a transverse axis ; but as the muscles
are directed obliquely outwards, the upper muscle turns the pupil
upwards and inwards, and the lower muscle turns it downwards and
inwards.

By the simultaneous action of two adjacent recti, the ball will
be moved to a point intermediate to that to which it would be
directed by either muscle singly.

Dissection. By opening the optic foramen, the attachment of
the recti muscles will be more fully laid bare, and they will be seen
to arise from a tendinous ring which passes above, outside and inside
the optic foramen, and bridges across the sphenoidal fissure from
below the inner and outer sides of the foramen, the two fibrous
bands meeting below at a small spicule of bone on the upper margin
of the great wing of the sphenoid. To dissect out the inferior
oblique muscle, let the eyeball be replaced in its natural position ;
then by separating from the facial aspect the lower eyelid from the
margin of the orbit, and removing some fat, the muscle will appear
beneath the eyeball arching from the inner to the outer side : if the
external tarsal ligament be divided, it may be followed upwards to
its insertion into the ball.

The INFERIOR OBLIQUE MUSCLE (fig. 230, h) is placed near the
anterior margin of the orbit, and differs from the other muscles in
being directed across, instead of parallel to the axis of the orbit.
It arises from the superior maxillary bone immediately outside the
opening of the nasal duct. From this spot the muscle passes out-
wards between the inferior rectus and the bone and then between the
eyeball and the external rectus, to be inserted into the sclerotic coat
between the outer and upper recti.

The borders of the muscle look forwards and backwards, and the
posterior receives its branch of the third nerve. The insertion of
the tendon is near that of the superior oblique muscle, but rather
closer to the optic nerve.

Action of the oblique muscles. The superior oblique acting alone
would draw the back of the eyeball upwards and inwards, and

ACTION OF THE OBLIQUE MUSCLES. 651

therefore cause the front of the eye to be directed downwards and

outwards. The inferior oblique would similarly turn the front of

the eye upwards and outwards. In consequence of their transverse

direction, these muscles would also tend to rotate the eyeball around

its antero-posterior axis, the superior oblique depressing, and the

inferior oblique elevating the inner end of the horizontal meridian

of the eye, but movements of this nature take place only to a very

limited extent during life.

The oblique muscles are believed to act mainly in controlling the and with

tendencv of the superior and inferior recti to rotate the eveball and ^"Perior

. ." J^ *' and inferior

turn it inwards. Thus, to move ttie eye directly upwards, the superior recti.

rectus and the inferior oblique are used, while the inferior rectus and

superior oblique co-operate in directing the eye downwards.

Dissection. To expose the small tensor tarsi muscle, the remain- Seek tensor
ing portion of the palpebral fascia is to be separated from the margin ^*^^'
of the orbit ; but the lids must be left attached at the inner side by
means of the internal tarsal ligament. On clearing away a little
areolar tissue in the neighbourhood of the inner commissure, after
the lids have been placed across the nose, the pale fibres of the
tensor tarsi will be seen.

The TENSOR TARSI MUSCLE arises from the crest of the lachrymal Tensor tarsi
bone, and slightly from the bone behind the crest. Its fibres are "™"^^ ^ *
pale, and form a very small flat band, behind the internal tarsal
ligament, which divides like that structure into a slip for each eye-
lid. In the lid the slip lies by the side of the lachrymal canal, and insertion ;
blends with the fibres of the orbicularis along the free margin of the
tarsus.

Action. The tensor tarsi draws backwards the inner canthus of use.
the eye and compresses the lachrymal sac, after it has been dilated
by the orbicularis palpebrarum in the act of winking.

Dissection. A small nerve, the orbital branch of the superior Trace offset
maxillary trunk, lies along the lower part of the outer wall of the maxiUaiy'^
orbit, and is now to be brought into view by the removal of the eye- "«rve.
hall and its muscles. This nerve is very soft and easily broken,
and is covered, as it enters the orbit through the spheno-maxillary
fissurCy by pale fleshy fibres (orbi talis muscle). Two branches,
temporal and malar, are to be traced forwards from it ; and the
junction of a filament of the lachrymal nerve with the former is to
be sought close to the bone. The outer wall of the orbit may be
cut away bit by bit, to follow the temporal branch to the surface
of the head.

The TEMPORO-MALAR or ORBITAL BRANCH of the superior maxillary Orbital
nerve arises in the spheno-maxillary fossa, and divides at the back .J^rior^^
of the orbit into malar and temporal branches, which ramify on the maxillary
face and the side of the head with companion vessels.

The malar branch is directed forwards through the canal of the its malar
same name in the malar bone to supply the skin of the upper and
outer part of the cheek, where it communicates with the malar
branches of the facial nerve.

662

DISSECTION OF THE ORBIT.

and

temporal

oflfsets.

Orbitalis
muscle.

Dissection
in spheno-
maxillary

Superior

maxillary

nerve.

in floor of
orbit.

Infraorbital
vessels.

Upper max-
illary nerve

passes to

through

infraorbital

canal.

Its branches
are— to
orbit ;

to the nose
and palate ;

to the

hinder teeth
and cheek :

The temporal bi-anch ascends in a groove in the bone on the outer
wall of the orbit, and after being joined by a filament from the
lachrymal nerve, passes into the temporal fossa through the temporal
canal in the malar bone : it is then directed upwards between the
temporal muscle and the skull, and perforates the temporal fascia
near the orbit (p. 501).

Orhitalis muscle. At the lower and outer angle of the orbit this
thin layer of unstiiped muscle is sometimes well seen. The fibres
cross the spheno-maxillary fissure, being attached to the edges, and
are pierced by the temporo-malar nerve.

Dissection. The contents of the orbit having now been removed
with the exception of the temporo-malar nerve, which is to
preserved if possible, the whole of the outer wall is to be cu
away and the greater wing of the sphenoid chipped away so as to
open up the spheno-maxillary fossa. Only an osseous ring should
be left round the superior maxillary division of tJie fifth nerve
where it issues from the skull through the foramen rotundum, and
the exposure of the nerve as it crosses the fossa to pass on to the
floor of the orbit will be completed by removing the fat. In the
fossa the student seeks the following oftsets, — the orbital branch
entering the cavity of the orbit, branches to Meckel's ganglion which
descend in the fossa, and the posterior dental branch along the back
of the upper jaw.

To follow onwards the nerve in the floor of the orbit, the contents
of the cavity having been taken away, the bony canal in which it
lies must be opened to its termination on the face. From the
infraorbital canal the anterior and middle dental branches are to
be traced downwards for some distance in the bone. The infra-
orbital vessels are prepared with the nerve.

The SUPERIOR MAXILLARY NERVE (fig. 231) commences at the
Gasserian ganglion, and leaves the cranium by the foramen rotun-
dum. The course of the nerve is almost straight to the face, across
the spheno-maxillary fossa, and along the orbital jjlate of the upper
maxilla through the infraorbital canal. Issuing from the canal by
the infraorbital foramen, where it is concealed by the elevator of the
upper lip, it ends in infraorbital or facial branches which radiate to
the eyelid, nose, and upper lip.

After the nerve comes to lie on the floor of the orbit it is called

the INFRAORBITAL NERVE.

Branches.— a. The orbital or temporo-malar branch (•*) has already
been described.

b. The spheno-palatine branches {^) descend from the nerve in
the fossa, and supply the nose and the palate ; they are con-
nected with Meckel's ganglion, and will be dissected with it
(Section XIII., p. G73).

c. Tiie posterior dental branch (») leaves the nerve near the upper
jaw. It enters a canal in the maxilla, and supplies branches to
the molar teeth and the lining membrane of the antrum ; near the
teeth it joins the middle dental nerve. Before entering the canal

THE SUPERIOR MAXILLARY NERVE. 653

it furnishes one or more offsets to the gum and the mucous mem-
brane of the cheek.

After the nerve becomes the infraorbital it gives off —

d. and e. The middle and anterior dental branches which arise to fore
together or separately from the trunk in the floor of the orbit, and ^^^^ '
descend in special canals in the wall of the antrum to end in branches
to the teeth, after forming loops of communication with one another,
and with the posterior dental nerve. From the middle branch
filaments are given to the bicuspid teeth ; and from the anterior to
the canine and incisors, as well as a twig or two to the inferior
meatus of the nose.

The terminal branches on the face, palpebral, lateral nasal and to lower
labial, have already been studied (p. 564). ^^^'^^ '

The INFRAORBITAL ARTERY is a branch of the internal maxillary infraorbital
in the spheno-maxillary fossa (p. 615). Taking the course of the ^^^^"^

Fig. 231. — Diagram of the Superior Maxillary Nerve.

2. Trunk of the nerve leaving the 5. Posterior dental nerves.
Gasserian ganglion. 6. Middle and anterior dental.

3. Spheno-palatine branches. 7. Facial branches.

4. Temporo-malar branch.

nerve through the infraorbital canal, the vessel appears on the face
beneath the elevator muscle of the upper lip ; and it ends in branches
which are distributed, like those of the nerve, between the eye and g^^jg i^
mouth. On the face its branches anastomose with offsets of the facial f^^e :
and buccal arteries. In the canal in the maxilla the artery furnishes oJ!^"^*^^^^ ^
small twigs to the orbit, and a larger antei-ior dental branch which ^^^ o^g to
runs with the nerve of the same name to the incisor and canine anterior

teeth,
teeth ; the dental branch also gives offsets to the antrum, and near

the teeth it anastomoses with the posterior dental artery.

The vein accompanying the artery communicates in front with the infraorbital
facial vein, and terminates behind in the alveolar plexus.

Direction. The examination of an eyeball may be omitted with
advantage till after the dissection of the head and neck has been
completed.

664

DISSECTION OF THE PHARYNX.

Section XL

THE PHARYNX AND THE CAVITY OF THE MOUTH.

Direction.

Detach
pharynx
from spine,

detach
head,

Separate
pharynx
from verte-
bral column

chisel
through
basi-occipi-
tal.

direction of
a saw-cut,

complete
division
with chisel.

Preserve
piece of
spine.

Fasten
pharynx.

then clean

muscles,

viz.

Direction. In this section the students of the two sides must work
together.

The pharynx can be examined only when it has been separated
from the back of the liead and the spinal column ; and it will
therefore be necessary to cut through the base of the skull in the
manner indicated below, so as to have the anterior half, with the
pharynx connected to it, detached from the posterior half.

Dissection. The head is to be separated from the trunk by
sawing through the vertebral column at the third dorsal vertebra
unless the dissector of the thorax has already done this in his
examination of the ligaments. The block then being removed from
beneath the neck, the head is to be placed downwards, so that it may
stand on the cut edge of the skull. Next the trachea and cesophagus,
together with the vagus and sympathetic nerves, are to be cut near
the first rib, and all are to be separated from the spine by drawing
them forwards as high as the basilar process of the occipital bone,
defining the base of the skull between the pharynx and the pre-
vertebral muscles, but being careful not to injure either. Then incise
the periosteum on the under surface of the exposed basilar part of
the occipital and cut through this part of the bone with a sharp
chisel, directing the chisel somewhat backwards as it is driven into
the skull cavity — a block being placed inside the skull against the
base to give the necessary support. Next turn the head on its side
and make a saw-cut on each side passing close behind the mastoid
process and extending, internally, to the posterior limit of the jugular
foramen. The division of the skull will then be completed by
chiselling, from within the cranial cavity, backwards through the base
between the outer end of the chisel-cut through the basi-occipital
and the inner end of the saw-cut behind the jugular foramen, taking
care that the chisel passes in this operation on the inner side of the
jugular foramen and the inferior petrosal sinus. The base of the
skull is now divided into two parts (one having the pharynx attached
to it, the other articulating with the spine), which can be readily
separated with a scalpel.

The spinal column with the piece of the occipital bone connected
with it should be set aside, and kept for after examination by the
workers on the two sides together.

Dissection of the pharynx (fig. 232, p. 656). Let the student take
the anterior part of the divided skull, and, after moderately filling
the pharynx with tow, fasten it with hooks on a block, so that the
cesophagus may be pendent and towards him.

He will then proceed to remove the fascia from the constrictor
muscles, in the direction of their fibres, and complete the separation

DISSECTION OF THE PHARYNX. 655

of the ditierent structures lying against the pharyngeal wall from one
another and make out their relations from the fresh point of view.
The margins of the inferior and middle constrictor muscles are to lower and
he defined. Beneath the lower one, near the larynx, will be found ^dctor^**'^
the recurrent nerve with companion vessels ; between the inferior and
middle are the superior laryngeal nerve and vessels ; and the stylo-
pharyngeus muscle disappear.-; beneath the upper border of the middle
constrictor.

To see the attachment of the superior constrictor to the lower jaw upper con-
and the pterygo-maxillary ligament, it will be necessary to cut ^^^^ ^'
through the internal pterygoid muscle. Above the upper fibres of
this constrictor, and near the base of the skull, are two small muscles
of the palate (f and h) entering the pharynx : one, tensor palati, lies
close inside the internal pterygoid muscle ; and the other, levator
palati, is deeper and larger.

The Pharynx is a portion of the alimentary canal which gives Pharynx:
passage to both food and air. It is placed behind the nose, mouth
and larynx, and extends from the base of the skull to the lower extent;
border of the cricoid cartilage of the larynx, where it ends in the
oesophagus on a level with the lower part of the sixth cervical
vertebra. In form it is somewhat conical, with the dilated part form ;
upwards ; and its length averages about four and a half inches, but length ;
varies according to the position of the head and the degree of
elevation of the larynx.

The tube of the pharynx is incomplete in front, where it com- is an incom-
municates with the cavities above mentioned, but is closed above, ^ ^ ^'
behind, and at the sides. Below, it opens into the gullet. On each relations ;
side of it are placed the trunks of the carotid arteries, with the
internal jugular vein, and the accompanying cranial and sympathetic
nerves. Behind it is the spinal column, covered by muscles, viz.,
longi colli and recti capitis antici.

In front, the pharynx is united to the larynx, the hyoid bone, attach-
the tongue, and the bony framework of the nasal fossae, which form "^^^ '''
the boundaries of its cavity in this direction. Behind and at the and con-
sides, it has a special muscular wall, and is only united by very " ™*^ ^^^'
loose connective tissues to surrounding parts. At the upper end the
bag is completed by a fibrous aponeurosis which fixes it to the base
of the skull ; and the whole is lined by nmcous membrane.

The aponeurosis of attachment is seen at the upper part of the Aponeurosis
pharynx, where the muscular fibres are absent, to connect the tube ° ^ arjnx.
to the base of the skull, and to complete the posterior boundary.
Superiorly it is fixed to the basilar process of the occipital, and the
petrous part of the temporal bone ; but inferiorly it becomes thin,
and is lost in the layer of connective tissue between the muscular
and mucous strata. On this membrane some of the fibres of the
superior constrictor muscle terminate.

The Muscles of the pharyngeal wall are arranged in two layers — Muscles in
an outer comprising the three constrictors, the fibres of which run
more or less transversely to the direction of the tube, and an inner

656

DISSECTION OF THE PHARYNX.

Pharyngeal
fascia.

of longitudinal fibres derived from the stylo-pharyngeiis and palato-
pharyngeus. Externally the constrictor muscles are covered by a

FiQ. 232. — External View op the Pharynx (Illustrations op

DlSSE(jTIONS).

Muscles :

A. Inferior constrictor

B. Middle constrictor,
c. Upper constrictor.
D. Stylo-pharyngeus.
P. Levator palati.

H. Tensor palati.
I. Buccinator.
K. Hyo-glossus.

Nerves :

1. Glosso-pharyngeal.

2. Hypoglossal.

3. Superior laryngeal.

4. External laryngeal.

5. Inferior, or recurrent,

laryngeal.

6. Lingual.

fascia, which is continued forwards above, beneath the internal
pterygoid muscle, to the surface of the buccinator.

THE CONSTRICTOR MUSCLES. 657

The INFERIOR CONSTRICTOR (fig. 232, a), the most superficial, Lo'^er
irises from the side of the cricoid cartilage, and from the inferior arises from
jornii, oblique line, and upper border of the thyroid cartilage. The ^^^^"^ "
origin is small when compared with the insertion, for the fibres JhemWdi?
radiate as they pass backwards, to be inserted along the middle line, lii^®:
where the muscles of opposite sides join.

The outer surface of the muscle is in contact with the sheath of parts in
the carotid vessels, and with the muscles covering the spinal column. ^^tiTlt
The lower border is nearly horizontal, and beneath it the inferior
laryngeal nerve and vessels (^) pass ; while the upper border ascends
ery obliquely and overlaps the middle constrictor. A few of the
lowest iibres of the muscle turn downwards, and are continued into
the longitudinal fibres of the oesophagus.

The MIDDLE CONSTRICTOR (fig. 232, b) lias a similar shape to the pre- Middle
ceding, that is to say, it is narrowed in front and expanded behind, constrictor
Its fibres arise from the great and small cornua of the hyoid bone on F^^?^ ^™^ .
a deeper plane than the hyo-glossus and from the stylo-hyoid liga-
ment. From this origin the fibres radiate, and are blended along the
middle line with those of the opposite muscle.

The posterior surface of this muscle is to a great extent concealed relations,
by the inferior constrictor. Laterally, it touches the carotid sheath ;
and its origin is beneath tb.e hyo-glossus muscle, the lingual artery-
passing between the two. Its upper border is separated from the
superior constrictor by the stylo-pharyngeus ; and in the interval
between the origins of the middle and inferior constrictors are the
superior laryngeal nerve and vessels.

The SUPERIOR CONSTRICTOR is thinner than the others, and of a Upper
quadrilateral form. It has a broad origin from the following parts ar/ses^from
in succession, commencing above, — the lower end of the internal pterygoid

. , ' ,111 1 -n process,

pterygoid plate and the hamular process, the pterygo-maxiUary jaw and

ligament, the hinder part of the mylo-hyoid ridge of the lower jaw, °^®"

the mucous membrane of the mouth, and the side of the tongue.

The fibres pass backwards, and are inserted by joining those of the inserted

fellow muscle along the middle line, where a tendinous raphe is a^iJph]"

formed between the two for the upper half of their depth. Some of

the highest fibres reach the tubercle on the under surface of the

basi-occipital and others end on the aponeurosis of the pharynx.

The parts in contact with this muscle externally are the deep relations:

vessels and nerves of the neck at the side, the middle constrictor

and prevertebral muscles behind : internally are the aponeurosis of

the pharynx and the palato-pharyngeus muscle. The upper border interval
.. 1 • 1 1 ^ ., "^ ^ , ,1. ,. ^\.i , between

forms an arch with the concavity upwards extending trom the ptery- muscle and

goid plate to the basilar process ; and the space between it and the ^*^"'^'
base of the skull is occupied by the aponeurosis of the pharynx, which
projects outwards above the muscle, and by the levator palati. Eusta-
chian tube and inferior palatine artery. The attachment to the
pterygo-maxillary ligament corresponds with the origin of the bucci-
nator muscle (i) between the two maxillary bones.

Action of constrictors. The muscles of both sides contracting at the use of

„ „ constrictors

D.A. U V

658

DISSECTION OF THE PHARYNX.

in swallow-
ing;

of upper
constrictor.

Pterygo-
maxillaiy
ligament.

Dissection
to show

longitudinal
muscles.

Dissection.

Interior of
pharynx.

Objects to
be noted.

same time will diminisli the size of the pharynx ; and as the anterior
attachments of the lower muscles are nearer together than those of
the upper, the tube will be contracted more behind the larynx than
near the head.

In swallowing, the object is first seized by the lower part of the
upper constrictor, and then forced on to the oesophagus by the succes-
sive action of the middle and inferior constrictors. Since the back of
the pharynx is closely applied to the prevertebral muscles, from:
which it cannot be separated in the natural condition of the parts,,
the effect of the contraction of these muscles is to draw the tongue,,
hyoid bone and larynx backwards, as well as somewhat upwards-
owing to the oblique direction of the greater number of the fibres of
the middle and lower constrictors ; and the cavity, when empty, is
compressed from before backwards.

The upper part of the superior constrictor narrows the space above
the mouth, and assists in bringing together the posterior pillars o.
the soft palate. (See the action of the palato-jDharyngeus, p. 664.)

The pterygo-maxillary ligament is a thin fibrous band which pass'
from the tip of the hamular process to the hinder end of the mylo
hyoid ridge of the lower jaw, and gives origin in front to the middl
fibres of the buccinator and behind to the superior constrictor. It i
often partly concealed externally by the meeting of the fleshy fibre
of the two muscles.

Dissection (fig. 233). By dividing the middle and inferior con
strictors midway between their origin and insertion, and reflectiuj
the parts forwards and backwards, the longitudinal fibres of the^
pharyngeal wall will be exposed.

The LONGITUDINAL or ELEVATOR MUSCLES of the pharynx are the
stylo-pharyngeus and palato-pharyngeus. The stylo-pharyngeus has
already been described (p. 626), but it may now be followed to its
insertion. The palato-pharyngeus is only partially seen, and will be
described with the muscles of the soft palate. Its fibres appear
behind those of the stylo-pharyngeus, and descend to the lower part
of the pharynx, reaching backwards to the middle line.

Dissection (fig. 233). Open the pharynx by an incision along the
middle, and, after removing the tow from the interior, keep it open
with hooks : a better view of the cavity will be obtained by parti
dividing the occipital attachment on each side.

The INTERIOR OF THE PHARYNX IS widcr from side to side tha
from before backwards, and its greatest width is opposite the hyoii
bone ; from that spot it diminishes both upwards and downward
but much more rapidly in the latter direction. In it the following^
objects are to be noticed.

At the top are situate the posterior apertures (g) of the nasal
fossae, which are separated by the septum nasi. Below them han^
the soft palate, partly closing the opening into the mouth ; and from;
its free margin a prominent fold of the mucous membrane, th
posterior pillar of the fauces (l), is continued downwards and back
wards on each side of the pharynx. Immediately behind each nasal

INTERIOR OF THE PHARYNX.

aperture is the trumpet-shaped end of the Eustachian tube ; and
from tlie anterior extremity of the prominence formed by the tube,
a ridge descends to join the posterior pillar of the fauces. Behind

659

Fig. 233. — Istekior View of the Pharynx (Illustrations of Dissections.)
Muscles of the Palate, and named h. Mouth cavity

parts

Levator palati.

Tensor palati.

Salpingo-pharyngeus.

Azygos uvulae.

Internal pterygoid.

End of the Eustachian tube.

Posterior naris.

Anterior pillar of fauces.

Position of tonsil.

Posterior pillar of fauces.

Opening of larynx.

Opening of oesophagus.

Uvula.

Superficial part of palato-

pharyngeus.

the opening of the Eustachian tube the mucous membrane is pro-
longed into a deep hollow, the lateral recess of the yharynx^ which
corresponds to the projection of the aponeurosis of the pharynx seen
externally.

u u 2

660

DISSECTION OF THE PHARYNX.

Seven aper-
tures, viz. —

Posterior
nares.

Eustachian
tube

cartilagi-
nous part ;

pharyngeal
opening ;

con.stnic-
tion.

Fauces.

Isthmus of
the fatices.

Upper
opening of
larynx.

On raising the soft palate, the opening into the mouth — isthmus
faucium (h) is exposed, bounded laterally by a mucous fold which
descends to the tongue and is named the anterior pillar of the fauces ;
while between the anterior and posterior pillars on each side is a
hollow containing the tonsil (k).

Next in order, below the mouth, comes the aperture of the
larynx (n) with the epiglottis projecting above it. Lowest of all
is the opening (o) from the pharynx into the oesophagus.

The apertures into the pharynx are seven in number, and have
the following position and boundaries : —

The posterior openings of the nasal fossa (choanae ; g) are oval in form,
and measure about an inch from above downwards, but only half ai
inch across. Each is constructed in the dried skull by the sphenoic
with the vomer and palate bones above, by the palate below, by th«
vomer internally, and by the internal pterygoid plate on the outer sid<

The Eustachian tube (f) is a canal, partly osseous, partly cartih
ginous, by which the tympanic cavity of the ear communicates wit]
the external air.*

If the mucous membrane be removed from the tube on the rig
side, the cartilaginous part is seen to be nearly an inch long. It is
fixed above to a groove between the petrous part of the temporal
and the sphenoid bones, and ends in front by a wide opening on
the inner side of the internal pterygoid plate, on a level with the
posterior extremity of the inferior spongy bone of the nose (fig. 237,
p. 670). Its opening in the pharynx is oval in form, and the inner
margin projects forwards, giving rise to a trumpet-shaped mouth.

This part of the tube is constructed of a triangular piece of yellow
fibro-cartilage, which is bent downwards on each side so as to enclose
a narrow space. The inner portion is larger than the outer, and
increases in breadth from behind forwards. On its outer side the tube
is completed by fibrous tissue. The cartilage is covered on its inner
side by mucous membrane, and through the tube the mucous lining
of the cavity of the tympanum is continuous with that of the pharynx.

The space included between the root of the tongue and the soft
palate is called the fauces. It is wider below than above ; and on
each side lies the tonsil.

The ISTHMUS FAUCIUM (h) is the narrowed aperture of communica-
tion between the mouth and the pharynx. It is bounded above by
the soft palate, below by the tongue, and on the sides by the anterior
pillars of the soft palate. Its size varies with the movements of these
parts, and it can be closed by the meeting of the soft palate and the
tongue.

The APERTURE OF THE LARYNX (n) is wide in front, where it is
bounded by the epiglottis, and pointed behind between the arytenoid
cartilages. The sides are sloped from before backwards, and are
formed by folds (aryteno-epiglottidean) of the mucous membrane
extending between the arytenoid cartilages and the epiglottis.
Behind it is limited by the cornicula laryngis, and by the arytenoid
muscle covered by mucous membrane. During respiration this

OPENING INTO THE (ESOPHAGUS. (>fil

aperture is unobstructed, but in the act of deglutition it is closed
by the approximation of the lateral folds and the lower part of the
epiglottis.

The OPENING INTO THE (ESOPHAGUS (o) is the narrowest part of Beginning of

the pharynx, and is opposite the cricoid cartilage and the sixth ^*^"^^ *^"'^'
cervical vertebra. At this spot the mucous membrane in the
oesophagus becomes paler than in the pharynx ; and the point at
which the pharynx ends is marked externally by a slight contraction,
and by a change in the direction of the muscular fibres.

The CAVITY OF THE PHARYNX is divided into three parts, which Snb<ii\ision
differ in their function with regard to the transmission of the food ph^ynx *^
and air. The upper or nasal portion is limited below by the soft '"^ nasal,
palate and its posterior pillars ; it gives passage only t(» air, and is
always open. The middle or oral portion extends downwards to oral,
the aperture of the larynx, and is traversed by both food and air ;
it is open when breathing through the mouth, but closed when
breathing solely through the nose, the aperture of the larynx then
corresponding to the interval between the posterior pillars. The
third part being behind the larynx is termed laryngeal, and only and laryn-
transmits food ; its walls are naturally in contact, except during the tkms^"^
act of deglutition.

The SOFT PALATE (velum pendulum palati ; q) is a moveable Soft palate
structure between the mouth and the pharynx, which can either mouth:"
close the opening of the mouth, or cut off the communication with
tlie nose, according as it is depressed or elevated. In the usual surfaces ;
position of the soft palate (the state of relaxation) its anterior
surface is concave, and is continuous with the roof of the mouth ;
A\hile the opposite surface is convex and turned to the pharynx.
The upper border is fixed to the posterior margin of the hard borders ;
palate ; and on each side it joins the pharynx. The lower border from it
is free, and is produced in the centre into a conical pendulous part *°^^ "^ **
— the uvula (p). Along its middle is a slight ridge, indicative of
the original separation into two halves.

Descending from the soft palate on each side of the fauces are Arches or
the two folds of mucous membrane before referred to, containing ^'
muscular fibres, and named the arches or pillars of the soft palate
or fauces. The anterior pillar (i) springs from the anterior surface anterior;
of the soft palate near the base of the uvula, and reaches to the
side of the tongue rather behind the middle ; and the posterior (l), posterior,
longer than the other, is continued from the lower border of the
velum to the side of the pharynx. As they diverge from their
origin to their termination, they limit a triangular space in which
the tonsil lies.

The soft palate consists of an aponeurosis, wiih muscles, vessels, CJonsti-
nerves, and mucous glands ; and tfie whole is enveloped by the velum,
mucous membrane.

Dissection. Some of the muscles of the palate are readily Dissect

displayed, but others require care in their dissection.

The two principal muscles of the soft palate — the elevator and levator and
' -^ ^ tensor on

right half;

662

DISSECTION OF THE PHAKYNX.

on left,
palato-
pharyngeus,

uvulae,

and palato-
glossus.

Aponeurosis
of palate.

Nine mus-
cles in it.

Elevator

muscle

arises

outside

pharynx,

and is lost
in velum ;

relations.

tensor, are very plain. These have already been partly dissected ;
but to follow them to their termination, let the upper attachment oft
the pharynx on the right side, and the part of the superior constrictor*
which arises from the internal pterygoid jdate be cut through. The
levator will be fully laid bare by the removal of the mucous mem-
brane and a few muscular fibres covering its lower end. The
tendon of the tensor palati should be followed round the hamular
process of the internal pterygoid plate ; and its situation in the
palate beneath the levator should be made evident. The position of
the Eustacliian tube with respect to those muscles should also be
ascertained.

On the left side, the mucous jnembrane is to be raised with great
care from the posterior surface of the soft palate, to obtain a view
of the superficial muscular fibres. Immediately beneath the mucous
covering are some fine transverse fibres of the palato-pharyngeus
muscle ; and beneath them, close to the middle line, are the longi-
tudinal fibres of the azygos uvulae. A slender muscular bundle
contained in the ridge of mucous membrane descending from the
extremity of the Eustachian tube is to be exposed and traced to its
junction wdth the palato-pharyngeus. On the right side, a deeper
set of fibres of the palato-pharyngeus is to be followed beneath the
levator and az3'^gos muscles.

The mucous membrane should next be removed from the muscular"
fibres contained in the arches of the palate, anil the muscle fibres
should be followed upwards and downwards. In order to see those
in the anterior fold, it will be necessary to take the membrane away
from the anterior surface of the palate. If the part is not tolerably
fresh, some of the paler fibres may not be visible.

Aponeurosis of the soft palate. Giving strength to the velum is a
thin but firm aponeurosis, v/hich is attached to the hard palate.
This membrane becomes thinner as it descends in the velum ; and it
is Joined by the tendon of the tensor palati muscle.

The MUSCLES OF THE SOFT PALATE are, on each side, an elevator
and tensor, which descend from the skull, with the palato-glossus
and palato-pharyngeus, which act as depressors, and a small median
azygos muscle.

The LEVATOR PALATI (fig. 233, A ; 234, ^) is a thick roundish
muscle which is partly situate outside the pharynx. It arises from
the under surface of the petrous portion of the temporal bone close
in front of the carotid foramen, and from the lower border of the
adjacent cartilaginous part of the Eustachian tube. Entering the
pharynx above the superior constrictor, the fibres of the muscle
spread out in the soft palate, where they join along the middle line
with those of the muscle of the opposite side.

The belly of the muscle rests against the lower border of the
Eustachian tube ; and the expanded part is embraced by two layers
of fibres of the palato-j^haryngeus (4).

Action. It raises the soft palate from the tongue, so as to enlarge
the fauces ; and by bringing the hinder part of the velum into

MUSCLES OF PALATE. 663

contact with the posterior wall of the pharynx, it can shut off the
upper part of that cavity, as in vocalisation, when the air is pre-
vented from passing through the nose.

The TENSOR or circumflexus palati (fig. 233, b ; 234 ^) is a thin Tensor
flattened muscle, lying immediately behind the internal pterygoid ^^'^^^
plate. About an inch wide at its origin^ it is attached to the
scaphoid fossa at the root of the internal pterygoid plate, to the arises
outer side of the Eustachian tube, and to the spinous process of pharyax;
the sphenoid. The fleshy fibres end below in a tendon, which
turns round the hamular process, and is inserted into a ridge close inserted into
to the posterior border of the hard palate, and blends inferiorly o? soft*"^^^
with the aponeurosis of the velum. palate;

The fleshy part of the tensor palati is placed between the internal relations;

1 . Azygos uvulae. 4. Palate - pharyngeus — upper

2. Tensor palati. end.

3. Levator palati. 5. External pteiygoid.

pterygoid muscle externally and the Eustachian tube and levator
palati internally. The tendon enters the pharynx between the
attachments of the buccinator muscle, and is thrown into folds as
it winds round the hamular process, a bursa being placed between
the two. In the soft palate it lies between the palato -pharyngeus
and palato-glossus.

Action. Acting from the skull the miLscle will fix and make use^on
tense the soft palate ; but its movements will be very limited, ^ *
seeing that the tendon is inserted partly into the palate bone.

The soft palate being fixed by its depressor muscles, the tensor, on tube,
taking its fixed point below, opens the Eustachian tube in
swallowing.

The PALATO-GLOSSUS MUSCLE (coustrictor isthmi faucium) is a ^fj^^j^.
small, pale band of fibres, which is contained in the anterior pillar
(fig. 233, i) of the soft palate. It is connected below with the side of ^^^'.

664

DISSECTION OF THE PHARYNX.

relations ;

Palato-
pharyngeus

forms two
layers in
velum ;

posterior
layer is
joined by
salpingo-
pliaryngeus ;

anterior
layer is
larger :

inserted
into thyroid
cartilage
and wall of
pharynx ;

in swallow,
ing;

of salpingo-
pharyngeus.

Azygos
muscle is in
two slips ;

the tongue ; from this spot the fibres cascend in front of the tonsil to
the anterior aspect of the soft palate, where they form a thin muscular
stratum, and join those of the fellow muscle along the middle line.^

At its origin the muscle is blended with the glossal muscles, andj
at its insertion it is placed beneath the tensor palati.

Action. The palato-glossus closes the isthmus of the fauces,
bringing the soft palate into contact with the tongue, and approxi-j
mating the anterior pillars, thus shutting off the mouth, from the^
pharynx.

The PALATO-PHARYNGEUS (fig. 233, Q ; 234, ■*) is much larger than
the preceding muscle, and gives rise to the eminence of the pos-
terior pillar of the soft palate. It begins in the soft palate in
two layers, which enclose between them the levator palati and
azygos uvulse muscles. The superficial part, very thin, and situate
immediately beneath the mucous membrane, meets in the middle
line the corresponding part of the opposite muscle ; it is also
joined by a slender fasciculus, which descends from the anterior
extremity of the cartilage of the Eustachian tube {salpingo-jj/iaryn-
geus, Santorini ; fig. 233, c). The deep or anterior layer is much
stronger, and lies between the levator and tensor palati muscles ;
its upper fibres spring from the hinder margin of the hard palate
and the aponeurosis of the velum, while the lower ones join those
of the opposite side. The two layers meet at the outer part of the
soft palate, and the muscle descends behind the tonsil on the side
wall of the pharynx. Spreading out below, the anterior fibres are
inserted into the hinder border of the thyroid cartilage, but the
greater number end in the submucous tissue of the pharynx beneath
the inferior constrictor, the hinder ones meeting the fellow muscle
in the middle line.

Action. The palato-pharyngeus depresses and tightens the soft
palate, raises the larynx and lower part of the pharynx, and at the
same time brings together the posterior pillars of the fauces, thus
acting as a sphincter by which the nasal portion is separated from
the oral portion of the pharynx. In swallowing, the hinder pillars
of the soft palate, being approximated by the action of this muscle,
form, together with the uvula, an inclined plane, beneath which
the food is directed downwards. The contraction of the salpingo-
pharyngeus at the same time assists in opening the Eustachian
tube, by drawing inwards and backwards the cartilage bounding
its orifice.

^ The AZYGOS uvuL^ (fig. 233, D ; 234, i) is situated along the middle
line of the velum near the posterior part. The muscle consists of
two narrow slips of pale fibres, which arise from the spine at the
posterior border of the hard palate, or from the contiguous aponeu-
rosis, and end below in the base of the uvula. Behind this muscle,
separating it from the nmcous membrane, is the thin stratum of the
palato-pharyngeus.

Action. Its fibres shorten the mid-part of the soft palate, and
elevate the uvula, directing that process backwards.

THE CAVITY OF THE MOUTH. 665

The TONSIL is an oval body, of variable size, placed above the Tonsil is
root of the tongue, in a recess between the anterior and posterior piuars of
pillars of the soft palate. Externally it is covereil by the superior <"a"ces :
constrictor muscle, and is a little above the angle of the lower jaw.

The surface of the tonsil is marked by apertures, which lead into stmcture.
crypts, or recesses, lined by mucous membrane. Its substance
consists mainly of lymphoid tissue, partly diffused, and partly
collected into follicles set round the walls of these recesses. A siaiilar Pharyngeal
collection of lymphoid tissue stretches across the posterior wall of ***'^^^*-
the pharynx, between the openings of the Eustachian tube, and is
known as the pharyngeal tonsil.

The arteries of the tonsil are numerous, and are derived from the Vessels,
facial, lingual, ascending pharyngeal and internal maxillary branches
of the external carotid. Its veins have a plexiform arrangement on and nerves,
the outer side. Nerves are furnished to it from the fifth and glosso-
pharyngeal. Its lynijjhatics join the deep cervical glands.

The MUCOUS membrane of the pharynx is continuous in front Mucous
with the lining of the nose, mouth and larynx. A fold encloses the pbary^T^
muscles and glands of the soft palate, from which the membrane
descends on each side over the tonsil to the tongue. It is also pro-
lunged by the Eustachian tube to the tympanum ; and below, it is
continued into the esophagus. It is provided with numerous glands ;
mucous glands in the upper part of the pharynx, and on both sur-
faces, but especially the upper, of the soft palate. Another collec-
tion of glands (arytenoid) is enclosed in the fold of mucous mem-
brane bounding the opening of the larynx on each side. The epithelium,
epithelium is columnar and ciliated above the soft palate, but scaly
and stratified below that part.

The CESOPHAGUS. This tube is much smaller than the pharynx. Beginning
and the walls are flaccid. It consists of two layers of muscular guJ^"^
fibres, with a lining of mucous membrane. The external layer is Two layers
formed of longitudinal fibres, which begin opposite the cricoid fibresr"^*'^
cartilage by three bundles, an anterior and two lateral ; the former outer ion-
is attached to the ridge at the back of the cartilage, and the others ^ * '
join the inferior constrictor. The internal layer is formed of circular and inner
fibres, which are continuous with those of the inferior constrictor.
The structure of the oesophagus is described more fully in the
dissection of the thorax.

The CAVITY OF THE MOUTH. The cavity of the mouth extends Mouth.
from the lips in front to the anterior pillars of the fauces behind.
Its boundaries are partly osseous and partly muscular, and its size
depends upon the position of the lower jaw-bone. When the lowpr fonn,
jaw is moderately removed from the upper, the mouth is an oval
cavity with the following boundaries. The roof, concave, is consti- ^^^ bounda-
tuted by the hard and soft palate, and is limited in front and on the
sides by the arch of the teeth. In the Jloor is the tongue, surrounded
by the arch of the lower teeth ; and beneath that body is the sub-
lingual gland on each side. Each lateral boundary consists of the
cheek and the ramus of the lower jaw ; and in it, uear the second

Vestibule.

Lining of
the mouth

differs in
parts :

on roof,

666 DISSECTION OF THE PHARYNX.

molar tooth in the upper jaw, is the opening of the parotid duct.
The anterior opening of the mouth is bounded by the lips ; and the
posterior is the isthmus faucium, leading into the pharynx. The
space between the lips and the teeth is distinguished from the rest
of the cavity as the vestibule of the mouth.

The mucous membrane is less sensitive on the hard than on the soft
boundaries of the mouth ; it lines the interior of the cavity, and
is reflected over the tongue. In front it is continuous with the skin,
and behind with the lining of the pharynx. The epithelium cover-
ing the membrane is scaly and stratified.

Between each lip and the front of the corresponding jaw the
membrane forms a small fold — frsenulum. Over the bony part of
the roof it blends with the dense tissue enclosing the vessels and
nerves ; on the soft palate it is smooth, and thinner. Along the
middle of the roof is a slightly raised raphe, which ends in front
opposite the anterior palatine fossa in a small papilla ; and on each
side of this, at the fore part of the hard palate, there are two or
three irregular transverse ridges. In the floor of the mouth the
membrane forms the fraenum linguae beneath the tip of the tongue,
and on each side of the fraenum it is raised into a ridge by the sub-
lingual gland, at the fore part of which is a small papilla, perforated
by the opening of Wharton's duct. On the interior of the cheek
and lips the mucous lining is smooth, and is separated from the
muscles by small buccal and labial glands.

Over the whole cavity, but especially on the lips and tongue, are
papillae.

The CHEEK extends from the commissure of the lips to the ramus
of the lower jaw, and is attached above and below to the alveolar
process of the jaw on the outer aspect. The chief constituent of the
cheek is the fleshy buccinator muscle : on the inner surface of this
is the mucous membrane ; and on the outer the integuments, with
some muscles, vessels, and nerves. The parotid duct perforates the
cheek obliquely opposite the second molar tooth of the upper jaw.

The LIPS surround the opening of the mouth ; they are formed
mainly by the orbicularis oris muscle covered externally by integu-
ment and internally by mucous membrane. The lower lip is the
larger and more moveable of the two. Between the muscular struc-
ture and the mucous covering lie the labial glands ; and in the sub-
stance of each lip, internal to the muscular structure, and separated
from the free edge by the marginal bundle of the orbicularis, is
placed the arch of the coronary arteries.

Teeth. In the adult there are sixteen teeth in each jaw, which are
arrangem'ent ^^^ ^^ ^^^^ alveolar borders in the form of an arch, and are surrounded
in jaw. by the gums. Each dental arch has its convexity turned forwards;

and, commonly, the arch in the maxilla overhangs that in the man-
dible when the jaws are in contact. The teeth are similar in the
half of each jaw, and have received the following names : — the
most anterior two are incisors, and the one next behind is the canine
tooth ; two, still farther back, are the two bicuspids ; and the last

floor,

cheek, and
lips.

Papillae.

Cheek ;

extent,

and struc-
ture.

Lips,

formed by
orbicularis.

contain
arteries.

Teeth
number and

THE CAVITY OF THE NOSE. 667

three are molar teeth. For details as to the form and structure of
the teeth reference must be made to a work on systematic or general
anatomv.

Section XII.

DISSECTION OF THE NOSE.

The skull will now be divided from before backwards into two Directions,
halves for the examination of the nasal cavity and of various remain-
ing parts of the anatomy of the skull. The tongue and larynx will
be separated, as directed, and put aside for examination by the
workers on the two sides together ; after which they will similarly
examine the prevertebral region and the ligaments. In this Section
also, and in the next, the students work together. While examining
the boundaries of the nose, the student should be provided with
a similar section of a macerated skull. It is also desirable, in order
to fully comprehend the form of the cavity, that he should have the
opportunity of inspecting a coronal section of the nose in the recent
state.

Dissection. Before sawing the bone, the loose part of the lower Dissection,
jaw should be taken away, and the tongue, hyoid bone, and larynx,
all united, are to be detached from the opposite half of the lower
jaw, and laid aside till the dissectors are ready to use them.

On the right side of the middle line saw carefully through the frontal Cut through
and nasal bones, the cribriform plate of the ethmoid, and the body *v\th^w.
of the sphenoid bone, without letting the saw descend more than can
be helped into the nasal cavity.

Next the roof of the mouth is to be turned upwards, and the soft Cut soft
parts are to be divided on the right side opposite the cut in the roof 1^^ bone in
of the nose. Then by sawing through the hard palate and the roof of

11 .'1 • , 1 ,. , . ^ mouth.

alveolar process ot the upper jaw along the same line, the piece of

the skull will be separated into two parts, right and left ; the right

half will serve for the examination of the meatuses, and the left

will show the septum nasi, after the mucous membrane has been

removed.

The CAVITY OF THE NOSE is placed in the centre of the bones of situation of

the face, being situate above the mouth, below the cranium, and "*^^^'

between tlie orbits. The space is divided into two nasal fossa? by Division
,. 1 ,.,. ., , into two.

a vertical partition, the septum.

Each fossa is elongated from before backwards, and compressed from Form and

side to side. Its length is greater below than above, and measures

near the floor about three inches. Its height in the middle of the

cavity is about one inch and three-quarters, becoming less in front

and behind. The upper part of the fossa is narrow (tig. 235, p. 668),

not exceeding one-eighth of an inch in breadth, and has been named

the olfactory cleft, which extends down as far as the lower border of

668

DISSECTION OF THE NOSE.

the middle turbinate bone ; below this the outer wall recedes, foi-m-
ing the respiratory passage, which has a width near the floor of about

Openings, three-fifths of an inch. In front, each fossa opens on to the face, and
behind into the pharynx, by orifices called nares. Other apertures
in the roof and outer wall lead into air-sinuses in the surrounding
bones, viz., frontal, ethmoid, sphenoid, and superior maxillary.
Each fossa presents for examination a roof and floor, an inner and
outer wall, and an anterior and j)osterior opening.

Roof. The ROOF is strongly arched from before backwards, and is formed

by the cribriform plate of the ethmoid bone in the centre ; by the
frontal and nasal bones, and the lateral cartilages in front ; and by
the body of the sphenoid, and the sphenoidal spongy bone, and the

8up.tnr%. hone
nUcL ethm. e«Il.

The Nasal Foss.e in Coronal Section.

On the right side of the figure the section passes through the openings of
the middle ethmoidal cells and the antrum into the middle meatus : on the
left side, a section of the hinder part of the fossa is represented, and the
posterior ethmoidal cells are seen opening into the superior meatus.

Floor.

Inner
boundary

palate bone, at the posterior part. In the dried skull many
apertures exist in it ; most are in the ethmoid bone for the
branches of the olfactory nerve with vessels, and one for the nasal
nerve and vessels ; on the front of the body of the sphenoid is the
opening of its sinus.

The FLOOR is slightly hollowed from side to side, and is formed by
the palate processes of the superior maxillary and palate bones.
Near the front in the dry skull is the incisor foramen leading to the
anterior palatine fossa.

The INNER WALL (septuui nasi) is partly osseous and partly cartila-
ginous. The osseous part is constructed by the vomer, by the
perpendicular plate of the ethmoid bone, and by those parts of the
frontal and nasal with which this last bone articulates. The

THE SPONTGY BONES AND MEATUSES.

669

partly carti-
laginous.

angular space in front in the macerated skull is filled in the recent
state by the cartilage of the sejnam, which forms part of the parti-
tion between the nostrils, and supports the lateral cartilages.
Fixed between the vomer, the ethmoid, and the nasal bones, this
cartilage rests in front on the incisor crest of the superior maxillge,
and projects between the cartilages of the nostrils. The septum
nasi is commonly bent to one side.

The OUTER WALL has the greatest extent arid the most irregular Outer
surface. Seven bones enter into its formation, and they come in ^°""^*^
the following order from before backwards :— the nasal and
superior maxillary ; the small lachrymal bone and the lateral mass

Outer Wall of the Nasal Cavity.

Upper turbinate bone.
Middle turbinate bone.
Inferior turbinate bone.
Flat part of the ethmoid bone.
Upper meatus.
Middle meatus.

8. Lower meatus.

9. Rudimentary fourth meatus.

10. Vestibule. The cut also shows
the apertures of the glands of the
nose.

of the ethmoid, with the inferior turbinate bone below these ; and
posteriorly the ascending part of the palate bone, with the internal
pterygoid plate of the sphenoid ; of these, the nasal, lachrymal, and formed of
ethmoid reach only about half way from roof to floor, and the ^^"^^ ^"^*'
inferior turbinate is confined to the lower half, while the others
extend the whole depth. In front of the bones, the lateral cartilages
complete this boundary.

From this wall three slightly convoluted osseous plates, named is irregular
turbinate or spongy hones (fig. 236), project into the cavity: — the °" *" **®'
upper (1) and middle (2) are processes of the ethmoid, but the lower spongy
one f) is a separate bone. The turbinate bones are confined to that ^^^^^
portion of the outer wall which is situate above the hard palate, hollows.

670

Meatuses.

Upper
meatus.

DISSECTION OF THE NOSE.

Between each turbinate bone and the wall of the nose is a
longitudinal hollow or meatus; and into these hollows the nasal
duct and tlie sinuses of the surrounding bones open.

The meatuses are the spaces arched over by the spongy bones ; and
as the bones are limited to a certain part of the outer wall, so are
the spaces beneath them.

The upper meatus (fig. 236, ^) is tiie smallest and straightest of the
three, and is limited to the posterior half of the space above the
hard palate. Into its fore part the posterior ethmoidal cells open
(figs. 235 and 237), and at its posterior end, in the dried skull, is

atrium

j'rontaX ginus

niiJ . ctkrrt. ccU»

st. ctltm. cells

splien. ethm. rcc.

gphen. sinus

Fig. 237. — Outer Wall of Right Nasal Fossa.

The whole of the middle, and the fore part of the lower turbinate bones
have been cut away, to show the openings in the middle and inferior
meatuses.

Middle
meatus.

Hiatus
semilunaris.

Ethmoidal
bulla.

the spheno-palatine foramen by which nerves and vessels enter the
nose.

The middle meatusj^h^^. 236, ') is longer than the upper, and reaches
from the posterior opening of the nasal fossa, nearly as far forwards
as the hard palate. The free border of the middle turbinate bone
being curved upwards anteriorly, this meatus is open in front as well
as below. On raising, or cutting away, the overhanging turbinate
bone (fig. 237), a deep groove, hiatus semilunaris, will be seen in the
fore part of the lateral wall of the meatus, bounded below by the
uncinate process of the ethmoid, and leading upwards through the
infundibulum of the latter bone to the frontal sinus. Into the
groove lower down the anterior ethmoidal cells open, and at its
hindmost part is a small aperture leading into the antrum of the
superior maxilla. Above the hiatus is a crescentic enlargement (the
ethmoidal bulla), above which is an opening leading into the middle

KEGIONS OF THE NOSE. 671

ethmoidal cells ; and in some cases there is a second opening into
the antrum close above the lower turbinate bone.

The inferior meatus (fig. 235), is wider than the middle one, and Lower
extends the whole length of the hard palate. Near its anterior "^^**'"^-
extremity is the opening of the nasal duct (fig. 237).

Above the superior meatus, in an angle formed by the roof, there Spheno-
is a vertical depression called the spJieno-ethmoidal recess (fig, 237), on recess,
the posterior wall of which the sphenoidal sinus opens ; and occasion-
ally a small fourth meatus, communicating with a posterior ethmoidal a fourth
cell, is present between the recess and the superior meatus, Smetfmes,

In front of the attached border of the middle turbinate bone there
is usually to be seen a faint ridge, the agger nasi (fig, 237), directed Agger nasi,
obliquely downwards and forwards, and forming the upper boundary
of a slight hollow known as the atrium of the middle meatus (fig. and atrium.
237).

The nares. In the recent condition of the nose each fossa has a Nares,
distinct anterior opening on the face, and another in the pharynx ;
but in the skeleton there is only one common opening in front for
both sides. These apertures and their boundaries have been before
described in the anatomy of the face.

The MUCOUS lining of the nasal fossae is called the pituitary Mucous
or Schiuiderian membrane, and is blended with the subjacent perios- ^osef ° ^
teum or perichondrium. It is continuous with the skin at the
nostril, with the membrane lining the pharynx through the posterior
nares, and with the conjunctiva through the nasal duct ; and it sends
prolongations to line the difterent sinuses, viz,, frontal, ethmoidal,
sphenoidal, and maxillary.

The apertures in the dry bone which transmit nerves and vessels, some fora-
viz., the incisor and spheno-palatine foramina, the holes in the ^^^^ closed,
cribriform plate, and the foramen for the nasal nerve and vessels,
are entirely closed by the membrane ; and the openings leading to others
the sinuses are reduced in size by the prolongations passing through byit."
them. At the tei-mination of the nasal duct the mucous membrane
forms a single or double fold, which is sometimes sufficient to close
the opening and prevent air entering the canal from the nose.

Over the middle and lower turbinate bones (to a greater extent Folds on
on the latter) the mucous membrane is thickened and projected ^"f^
beyond the edges of the bones by the large submucous vessels, so
that the meatuses are deeper and longer in the recent state than in
the dried skull.

The appearance and structure of the lining membrane diff'er in the Three
upper and lower parts of the nasal fossa, and near the anterior open- na^^al'fossa.
ing, whence a division of the cavity is made into three portions,
which are termed respectively the olfactory region, the respiratory
region, and the vestibule.

The vestibule (fig. 237) is the slightly dilated portion of the Vestibule,
cavity immediately within the nostril It is bounded by the
cartilage of the aperture and the ala of the nose ; and its wall is
more flexible than that of the part above. The lining membrane of

lished

672

DISSECTION OF THE NOSE.

Respiratory-
region.

Olfactory
region.

the vestibule has the characters of the outer skin, being furnished
with papillae and hairs (vibrissas), and lined by a stratified scaly
epithelium.

The respiratory region is the part below the level of the middle
turbinate bone. Its mucous membrane is thick, of a red colour,'
very vascular, and has numerous mucous glands, the openings of
which are readily seen on the. surface. The glands are largest and
most abundant on the inferior turbinate bone, andat the lower and
back part of the cavity. The epithelium of this region is columnar
and ciliated.

The olfactory region is the narrowed upper part of the nasal fossa,
which is enclosed by the ethmoid bone. It comprises the part of the

Fig. 238. — Nerves of the Septum of the Nose.

1. Olfactory bulb and inner set of 3. Naso - palatine nerve from
olfactory nerves. Meckel's ganglion (too large in the

2. Nasal nerve of the ophthalmic figure).
trunk.

Mucous
membrane
in sinuses.

roof formed by the cribriform plate, the part of the septum (about
one-third) formed by the perpendicular plate of the ethmoid, and,
on the outer wall, the upper and middle turbinate bones, together
with the flat surface of the lateral mass of the ethmoid in front of
the former. Over this region the olfactory nerves are distributed,
and it is, therefore, the seat of the sense of smell. The olfactory
mucous membrane is thinner, softer, and less vascular than that in
the respiratory region, and it has in the fresh state a yellowish
colour. Its epithelium is columnar, but not ciliated ; and it is
thickly beset with simple tubular glands.

In the sinuses the mucous lining is thin and pale, and its glands
are few and small.

OLFACTORY NERVES. 673

Dissection. At this stage of the dissection, but little will be Dissection
seen of the distribution of the olfactory nerves. If the bony and andTessels.
cartilaginous septum be removed, so as to leave entire the membrane
covering it on the left side, the nervous filaments will appear on
the surface, near the cribriform plate. In the membrane, near the
front of the septum, an offset of the nasal nerve is to be found.

The naso-palatine nerve and artery (fig. 238, '') are to be sought
lower down, as they are directed from behind forwards, towards
the anterior palatine fossa ; the artery is readily seen, especially if
it is injected, but the fine nerve is embedded in the membrane, and
will be found by scraping with the point of the scalpel.

By cutting through the fore and upper part of the membrane
detached from the septum nasi, other branches of the olfactory
nerve may be traced on the outer wall of the nasal fossa.

The OLFACTORY NERVES Spring from the under surface of the Olfactory
olfactory bulb as it lies on the cribriform plate of the ethmoid bone °®''^'^^ •
(fig. 238, ^), and descend to the olfactory region of the nose through
the apertures in this part of the roof. They are about twenty in
number, and are divided into two sets. Those of the inner set are inner set ;
the larger, and run downwards in the grooves on the perpendicular
plate of the ethmoid, to be distributed over the upper third of the
septum. The outer set (fig. 239, p. 675) ramifies over the upper
turbinate bone, the flat surface of the ethmoid in front of this, and outer set,
the fore part of the middle turbinate bone. As the nerves leave the
skull, they receive sheaths from the dura mater and pia mater, which
are continued as far as their terminal ramifications, and then become
lost in the surrounding tissue. The trunks break up into tufts of
filaments which communicate freely together, forming a close net-
work beneath the mucous membrane. The olfactory nerves consist
wholly of non-medullated fibres.

The other nerves in the nose will be described in the following
section.

Blood-vessels. The different vessels of the nose will be described Blood- ves-

• « S6ls of TIOSC

in the next section, p. 677 et seq. The arteries form a network in . '
the pituitary membrane, and a large submucous plexus on the edge
of each of the two lower spongy bones, especially on the inferior.
The veins have a plexiform disposition like the arteries, and this veins,
is largest on the lower spongy bone and the septum nasi.

Section XIII.

SPHENO-PALATINE AND OTIC GANGLIA, THE FINAL
BRANCHES OF THE INTERNAL MAXILLARY VESSELS,
THE FACIAL NERVE AND THE INTERNAL CAROTID
ARTERY IN THE TEMPORAL BONE.

The preparation of Meckel's ganglion and its branches (fig. 239), Meckel's
and of the terminal branches of the internal maxillary artery, is ^°^ ***°'
a difficult task, in consequence of the nerves and vessels being

D.A, X X

674

DISSECTION OF THE HEAD.

Dissection

of palatine
and

nasal
branches

body of
ganglion ;

Vidian
nen'e.

contained in osseous canals which require to be opened. Tlie
branches are first to be eought, and these are then to be followed
to the ganglion and the main trunk.

Dissection. The left half of the head is to be used for the dis-
play of Meckel's ganglion and its branches ; but the students will
derive advantage from first attempting the dissection on the remains
of the right side.

To lay bare the branches to the palate, detach the soft parts in
the roof of the mouth from the bone, until the nerves and vessels
escaping from the posterior palatine canals are arrived at. Cut oft",
with the bone forceps, the posterior part of the hard palate to a
level with the vessels and nerves ; and cleaning these, trace offsets
behind into the soft palate, and follow the main pieces forwards to
the front of the mouth.

Take away, without injury to the naso-palatine nerve and vessels
(already found), the hinder portion of the loose piece of mucous
membrane detached from the septum nasi ; and separate the mucous
membrane from the outer wall of the nasal fossa, behind the spongy
bones, as high as the sph en o -palatine foramen. In reflecting for-
wards the membrane, vessels and nerves will be seen entering it
through the foramen ; but these may be left for the present, and
directions for their dissection will be subsequently given. When
the lining membrane of the nose has been removed behind the
spongy bones, the palatine nerves and vessels will appear through
the thin translucent palate bone, and may be readily reached by
breaking carefully through the latter with a chisel. Afterwards
the tube of membrane containing the palatine vessels and nerves
being opened, these are to be followed down to the soft palate and
the roof of the mouth, and upwards to the ganglion which is close to
the body of the sphenoid bone.

To bring Meckel's ganglion fully into view, it will be necessary to
saw through the overhanging body of the sphenoid bone, to cut away
pieces of the bones surrounding the hollow in which it lies and to
remove with care the enveloping fat and the i^eriosteum. The
ganglion then appears as a flattened reddish-looking body, from
which the Vidian and pharyngeal nerves pass backwards. Besides
these branches, the student should seek two large nerves from the
top of the ganglion which join the superior maxillary trunk, and
smaller offsets to the floor of the orbit.

To trace backwards the Vidian branch to the carotid plexus and
the facial nerve, the student must lay open the Vidian canal in the
root of the pterygoid process ; and in doing this he must define the
small pharyngeal branches of nerve and artery which are superficial
to the Vidian, and lie in the pterygo-palatine canal. At the back of
the Vidian canal, a small branch from the nerve to the plexus on the
internal carotid artery is to be looked for. Lastly, the prolongation
of the Vidian nerve (large superficial petrosal) is to be followed into
the skull through the dense tissue in the foramen lacerum, after
cutting away the apex of the petrous portion of the temporal bone,

MECKEL'S GANGLION.

675

dividing the internal carotid artery ; and it is to be pursued on
surface of the temporal Lone, beneath the ganglion of the fifth
nerve, to the hiatus Fallopii. Its junction with the facial nerve
will be seen with the dissection of that nerve.

The branches of the ganglion to the nose will be found entering Seek
the outer surface of the detached mucous membrane opposite the th^n'Se'! ^°
;pheuo- palatine foramen, with corresponding arteries. One of these
nerves (naso-palatine), dissected before in the membrane of the
:eptum, is to be isolated, and to be followed forwards to where it
enters the floor of the nose. The branches of the internal maxillary
artery with the nerves are to be cleaned at the same time.

Fig, 239. — Nerves op the Outer Wall of the Nose and op the Palate.

1. Olfactory tract.

2. Olfactory bulb giving branches
to the nose.

3. Third nerve.

4. Fourth nerve.

5. Fifth nerve.

6. Nasal nerve of the ophthalmic.

7. Meckel's ganghon.

8. Vidian nerve.

9. Large palatine nerve.
10. Small palatine nerve.
tt Nasal branches.

The SPHENO-PALATINE or Meckel's ganglion (fig. 239,2) lies
in tlie spheno-maxillary fossa, close to the spheno-palatine fora-
men, and is connected with the branches of the superior maxillary
nerve to the palate. The ganglionic mass is somewhat triangular in
form, and of a reddish grey colour. It is situate, for the most part,
behind the branches (spheno-palatine) of the superior maxillary
nerve, so as to surround only some of their fibres ; and it is prolonged
posteriorly into the Vidian nerve. Meckel's ganglion resembles the
other ganglia in connection with the fifth nerve in having sensory,
motor, and sympathetic offsets or roots connected with it.

The BRANCHES of the ganglion are distributed chiefly to the nose
and palate, but small offsets are given to the pharynx and the orbit.
Other offsets or roots connect it with surrounding nerves.

X X

Ganglion of
Meckel :

situation
and connec-
tion with
lifth nerve :

composi-
tion ;

branches.

676

DISSECTION OF THE HEAD.

Nasal
branches
are —

superior
nasal,

naso-
palatine.

Palatine
branches

are three.

Large nerve
has branches
to nose ;

small ; and

external
palatine.

Pharyngeal
branch.

Orbital
branches.

Uniting
branches,
to fifth.

and to facial
and sympa-
thetic

through the
Vidian.

Branches to the nose. The nasal branches, from three to five
in number, are very small and soft, and pass inwards through thet
spheno-palatine foramen ; they are distributed in the nose and the
rOof of the mouth.

]. The superior nasal branches ramify in the mucous membrane on
the two upper spongy bones, and a few filaments reach the back part:
of the septum nasi.

The naso-palatine nerve (fig. 238, ^, p. 672), crosses the roof of the
nasal fossa to reach the septum, on which it descends to near the front'
of that partition. In the floor of the nose it enters a special canal by,
the side of the septum, the left being anterior to the right, and is
conveyed to the roof of the mouth, where it lies in the centre of the
anterior palatine fossa. Finally, the nerves of opposite sides are
distributed in the mucous membrane behind the incisor teeth, and
communicate with one another. On the septum nasi filaments are
supplied by the naso-palatine nerve to the mucous membrane. To
follow the nerve to its termination, the canal in the roof of the
mouth must be opened.

Branches in the palate. The nerves of the palate, though
connected in part with the ganglionic mass, are the continuation of
the spheno-palatine branches of the superior maxillary nerve (p. 652).
Below the ganglion they are divided into three — large, small, and
external.

1. The large or anterior palatine nerve (fig. 239,^) reaches the roof
of the mouth through the largest palatine canal, and courses for-
wards nearly to the incisor teeth, where it joins the naso-palatine
nerve. While in the canal, the nerve furnishes two or more filaments
(inferior nasal^ t) to the membrane on the middle and lower spongy
bones ; in the roof of the mouth it supplies the mucous membrane
and glands, and gives an offset to the soft palate.

2. The small or posterior palatine nerve {^^) lies in the smaller canal,
and ends below in the soft palate, the uvula, and the tonsil.

3. The external palatine nerve is very small, and descends in the
canal of the same name to be distributed to the velum palati and
the tonsil.

The pharyngeal branch is a minute twig which is directed
through the pterygo-palatine canal to supply the mucous membrane
of the pharynx near the Eustachian tube.

Branches to the orbit. Two or three in number, these ascend
through the spheno- maxillary fissure, and end in the periosteum and
orbital muscle (p. 652). It will be necessary to cut through the
sphenoid bone to follow these nerves to their termination.

Connecting branches. The ganglion is united, as before said,
with the spheno-palatine branches of the fifth nerve (fig. 239, 7),
receiving sensory fibres through them ; and through the medium of
the Vidian, which is described below, it communicates with a motor
nerve (facial), and with the sympathetic nerve.

The Vidian nerve (^) passes backwards through the Vidian canal,
and sends some small filaments through the bone to the membrane

BRANCHES OF THE fNTERNAL MAXILLARY ARTERY. 677

at the back of the roof of the nose (upper posterior nasal branches). At
its exit from the canal, the nerve receives a soft reddish offset {large
ieep 2)etrosal nerve) from the sympathetic on the outer side of the
carotid artery. The continuation of the nerve enters the cranium,
through the foramen lacerum, and is directed backwards in a groove
^ on the surface of the petrous part of the temporal bone, where it takes
the name of large superficial petrosal nerve (fig. 240, ', p. 678). Lastly
it is continued through the hiatus Fallopii, to join the geniculate
ganglion of the facial nerve (p. 679).

The Vidian nerve is supposed to consist of motor and sympathetic vidian a
fibres in the same sheath, as in the connecting branches between the ^e™'^^"^'^
ympathetic and spinal ner\es.

Directions. The students may now give their attention to the
remaining nerves in the nasal cavity.

Dissection. The nasal nerve is to be sought behind the nasal Seek other
bone (fig. 239) by gently detaching the lining membrane, after "^^^^^*"
having cut off the projecting bone. A branch is given from the
nerve to the septum, but probably this, and the trunk of the
nerve, will be seen but imperfectly in the present condition of the
part.

The terminal branches of the internal maxillary artery in the vessels of
spheno-maxillary fossa have been laid bare in the dissection of°
Meckel's ganglion, but they may be now completely traced out.

The NASAL NERVE (of the ophthalmic) (fig. 239, ^) has been already Xasai nerve
teen in the skull and orbit. Entering the nasal fossa by an aperture na^{^bon?;
at the fiont of the ethmoid bone, the nerve gives a branch to the gives
membrane of the septum, and then descends in a groove on the back
of the nasal bone. At the lower margin of the latter it escapes
between the bone and the upper lateral cartilage to the surface of
the nose.

Branches. The hranch to the septum (fig. 238) divides into ^^^^J^'^^''
tilaments that ramify on the anterior part of that partition, and
reach nearly to the lower border.

One or two filaments are likewise furnished by the nerve to the and to
mucous membrane on the outer wall of the nasal fossa : these extend
as low as the inferior spongy bone.

Terminal branches of the internal maxillary artery. Branches of

The branches of the artery in the spheno-maxillary fossa, which maSiiary
have not been examined, are the superior palatine, nasal, pterygo- artery are
palatine, and Vidian.

The supeHor or descending palatine is the largest branch, and P^^^*'"^®
accompanies the large palatine nerve through the posterior palatine
canal, and along the roof of the mouth ; it anastomoses behind the
incisor teeth with its fellow, and with the naso-palatine branch
through the incisor foramen. This artery supplies offsets to the
soft palate and tonsil through the other palatine canals, and some
twigs are fiurnished to the lining membrane of the nose. In the
roof of the mouth the mucous membrane, glands and gums receive
their vessels from it.

678

DISSECTION OF THE HEAD.

nasal
branches,

one to sep-
tum nasi ;

pterygo-
palatine
bmnch ;

"Vidian
branch

Veins to
alveolar
plexus.

Facial
nerve.

The nasal or spheno-palatine artery enters the nose through the
spheno-palatine foramen, and divides into branches. Some of these
(lateral nasal) are distributed on the spongy bones, and the outer
wall of the nasal fossa, and supply offsets to the posterior ethmoidal
cells. One long branch, naso-palatine or artery of the septum nasi,
runs on the partition between the nasal fossae to the incisor foramen,
through which itanastomoses with the descending palatine in the roof
of the mouth ; this branch accompanies the naso-palatine nerve, and
covers the septum with numerous ramifications.

The pterygo-palatine is a very small branch which, passing
backwards through the canal of the same name, is distributed

to the lining membrane of
the pharynx.

The Vidian or pterygoid
branch is contained in the
Vidian canal with the nerve
of tlie same name, and ends
on the mucous membrane of
the Eustachian tube and the
upper part of the pharynx.

Some small nasal arteries
are furnished to the roof of
the nasal fossa by the pos-
terior ethmoidal branch of the
ophthalmic (pp. 647, 648).
Also the anterior ethmoidal
(internal nasal) enters the
cavity with the nasal nerve,
and ramifies in the lining
membrane of the fore part
of the nasal chamber as low
as the vestibule ; a branch
passes to the face between
the nasal bone and the carti-
lage with the nerve. Other
offsets from the facial artery
supply the nose near the
nostril.
Veins. The veins accompanying the terminal branches of the
internal maxillary artery enter the alveolar plexus in the spheno-
maxillary fossa. Beneath the mucous membrane of the nose the
veins have a plexiform arrangement, as before said.

Facial Nerve in the Temporal Bone (fig. 240). Tliis nerve
winds through the petrous part of the temporal bone ; and it is
followed with difficulty in consequence of the extreme density of
the bone, and the absence of marks on the surface to indicate its
position. To render this dissection easier, the student should be
provided, for comparison, with a temporal bone, in which the course
of the facial nerve and the cavity of the tympanum are dis^jlayed.

Fig. 240. — Facial Nkrve in the
Temporal Bone.

1. Facial nerve.

2. Large suijerficial petrosal.

3. Small superficial petrosal from
Jacobson's nerve.

4. External superficial petrosal.

5. Chorda tympani of the facial.

THE FACIAL NERVE IN THE TEMPORAL BONE. 679

Dissection. Each student may now work on his own side. The Dissection
trunk of the nerve is to be found as it leaves the stylo-mastoid th^bOTTe"
foramen, and from this point it is to be followed upwards through
the temporal bone. With this view, the side of the skull should be
sawn through vertically between the meatus auditorius extemus and
the anterior border of the mastoid process, so as to open the lower
part of the aqueduct of Fallopius from behind. The nerve will be
then seen entering deeply into the substance of the temporal bone ;
and it can be followed forwards by cutting away with the bone-
forceps all the bone projecting above it. In this last step the cavity of
the tympaniuu will be opened, and the chain of bones in it exposed.

The nerve is to be traced onwards along the inner side of the and its
tympanum, until it becomes enlarged, and bends suddenly inwards ^^°" '
to the meatus auditorius internus. The surrounding bone is to be
removed from the enlargement, so as to allow of the petrosal nerves
being traced from it ; and the internal meatus is to be laid open, to
see the facial and auditory nerves in that canal.

The course of the chorda tympani nerve (branch of the facial) of chorda
across the tympanum will be brought into sight by the removal of '

the central ear bone, the incus. This nerve may be also followed
to the facial through the wall of the cavity behind, as well as out
of the cavity in front.

The remaining branches of the facial nerve in the bone are very and other
minute, and are not to be seen except on a fresh piece of the skull
which has been softened in acid. The student may, therefore, omit
the paragraphs marked with an asterisk, until he is able to obtain a
part on Mhicli a careful examination can be made.

The FACIAL NERVE (lig. 240, 1)) traverses the internal auditory Facial nerve
meatus, and entering the aqueduct of Fallopius at the bottom of that
hollow, is conducted through the temporal bone to the stylo-mastoid winda
foramen, and the face. In its serpentine course through the bone, ^^^^^i
the nerve is first directed outwards to the inner wall of the bone,
tympanum ; at that .spot it bends backwards, and is marked by a is marked
ganglionic swelling — geniculate ganglion, with which several small whi'chV"^
nerves are united. From this swelling the nerve is continued at off twigs,
first backwards and then downwards through the arched aqueduct,
to the aperture of exit from the bone.

The hrancJies of the nerve in the bone serve chiefly to connect it
with other nerves ; but one supplies the tongue, and another the
stapedius muscle, but the branches marked thus * will not be seen
except on a specially prepared part as described on p. 812.

* Connecting branches unite the facial with the auditory and Branches
glosso-pharyngeal nerves, with Meckel's ganglion, and with the nerve
lingual branch of the inferior maxillary nerve.

* Union with the auditory nerve. In the bottom of the meatus to auditory,
the facial and auditory nerves are connected by one or two minute
filaments.

Connecting branches of the geniculate ganglion. From the con-
vexity of the swelling on the facial nerve three small branches

DISSECTION OF THE HEAD.

to Meckel's
ganglion,
tympanic of
glosso-pha-
ryngeal, and
sympa-
thetic ;

nerve to
stapedius ;

chorda
tympani
to lingual.

Auditory
nerve.

Otic

ganglion.

Dissection
to find it.

r-4

proceed. One is the large superficial petrosal nerve {^), passing to
the Vidian ; another is a filament* of communication with the
small superficial petrosal nerve of the tympanic plexus {^) ; and the
third is the external superficial petrosal nerve* (f-), which unites the
ganglion with the sympathetic on the middle meningeal artery.

* The branch of the stapedius muscle arises at the back of the
tympanum, and is directed forwards to its muscle.

Chorda tympani. This long but slender branch of the facial
nerve crosses the tympanum, and ends in the tongue. Arising about

a quarter of an inch
from the stylo-mastoid
foramen, it enters
the tympanum below
the pyramid. In the
cavity (fig. 240,-^) the
nerve is directed for-
wards across the han-
dle of the malleus and
the membrana tympani
to an aperture on the
inner side of the Gla-
serian fissure, through
which it leaves the
tympanum.

Outside the skull
the chorda tympani
joins the lingual nerve,
and continues along it
to the submaxillary
ganglion and the tongue
(p. 625).

The AU DITORY

NERVE will be learnt
with the ear. Entering
the internal auditory
meatus with the facial
nerve, it divides into
an upper smaller, and a lower larger part, which are distributed to
the membranous labyrinth.

Otic ganglion. At this stage of the dissection there is little to
be seen of the ganglion, but the student should keep in mind that
it is one of the things to be examined in a fresh part. Its situation
is on the inner aspect of the inferior maxillary nerve, immediately
below the foramen ovale, and it adheres closely to the trunk of the
nerve.

Dissection (fig. 241). Putting the part in the same position as for
the examination of Meckel's ganglion, the dissector should define
the Eustachian tube and the muscles of the palate, and then take
away the levator palati and the cartilaginous portion of the tube,

Fig.

241. — The Otic Ganglion from the
Inner Side.

with

Tensor tympani muscle.
Internal pterygoid muscle.
External carotid artery

the sympathetic on it.
Otic gangHon.

Small superficial petrosal nerve.
Nerve to tensor tympani.
Chorda tympani joining lingual.

5. Nerve to internal pterygoid.

6. Nerve to tensor palati.

7. Auriculo- temporal nerve.

BRANCHES OF THE OTIC GANGLION. 681

K using much care in removing the latter. When some loose areolar
tissue has been cleared away, the internal pterygoid muscle (6)
comes into view, with the trunk ot the inferior maxillary nerve
above it ; and a branch descending from that nerve to the internal
pterygoid muscle. If the nerve to the pterygoid be taken as a
guide, it will lead to the ganglion.

To complete the dissection, saw vertically through the petrous to deHue
part of the temporal bone near the inner wall of the tympanum, the SS^ts"
bone being supported while it is divided. Taking off some mem- branches,
brane which covers the ganglion, the student may follow backwards
a small branch to the tensor tympani muscle ; but he should open
the small tube that contains the muscle, by entering it below
through the carotid canal. Above this small branch there is
another minute nerve (small superficial petrosal), which issues
from the skull, and joins the back of the ganglion. A small twig
is to be sought from the front of the ganglion to the tensor palati
muscle ; and other minute filaments to join the sympathetic nerve
on the large meningeal artery and the chorda tympani.

The OTIC GANGLION (Arnold's ganglion ; fig. 241) is a small reddish JjV^^^^"-^
body, which is situate on the inner surface of the inferior maxillary fnner side of
nerve close to the skull, and surrounds the origin of the nerve to J^SuIry
the internal pterygoid muscle. By its inner surface the ganglion is oerve.
in contact with the Eustachian tube, and at a little distance behind
lies the large middle meningeal artery. In this ganglion, as in the structure,
others connected with the fifth nerve, filaments from motor, sensory,
and sympathetic nerves are blended. Some twigs are furnished by
it to muscles.

Connecting branches — roots. Through its connection with the Branches
nerve to the internal pterygoid, the otic ganglion receives fibres from Sh)
both the small and large roots of the inferior maxillary- nerve, so
that it may be said to derive its motor and sensory roots from the
fifth. Its sympathetic root comes from the plexus on the middle J>'^P-
meningeal artery. The ganglion is farther joined behind by the
small superficial petrosal nerve (^), through which fibres are conveyed seventh,
to it from the facial and glosso-pharyngeal nerves. One or two ninth,
short branches pass between the ganglion and the beginning of the auricuio-
auriculo-temporal nerve ; and a filament descends to the chorda and chorda
tympani. *^P"°*'

Branches to muscles. Two muscles receive their nerves through Branches to

1 . , . . .1 1 ^ • mi- muscles :

the Otic ganglion, viz., tensor tympani and tensor palati. ine nerve tensor

to the tensor tympani {^ is directed backwards to gain the bony ^^^P^^j^^

canal lodging the muscle. The branch for the tensor palati (^) arises palati.

from the front of the ganglion, and enters the outer surface of its

muscle. The fibres of these branches are derived mainly from the

internal pterygoid nerve.

The nerve of the internal pterygoid muscle (») arises from the inner ^^^^^.J^^^*}^

side of the inferior maxillary nerve near the skull, and penetrates pterygoid.

the deep surface of the muscle. This nerve is formed almost entirely

by an oflset from the motor root of the fifth.

682

DISSECTION OF THE TONGUE.

Expose the

carotid

artery.

The Carotid Canal. Dissection. The student should now com-
plete the exposure of the internal carotid artery in the temporal bone-
by chipping away the outer wall of the canal, taking the artery as]
a guide. In cleaning the artery large, and rather red, branches of
the superior cervical ganglion of the sympathetic will be seen if the
part has been well kept ; and, in a fresh part, a small filament from
the tympanic branch of the glosso-pharyngeal may be seen to join the
sympathetic at the posterior part of the canal, and another from
the Vidian at the fore part.

The INTERNAL CAROTID ARTERY IN THE TEMPORAL BONE. The

artery has a winding course in the bone ; at first it ascends in front
of the cochlea and tympanum ; next it is directed forwards and . ]
inwards almost horizontally ; and, lastly, it turns upwards into th«
cranium through the foramen lacerum. Branches of the symjpathetic^
nerve and a venous plexus surround the vessel in the bone.

Section XIY.

DISSECTION OF THE TONGUE.

Directions.

Dissection.

Tongue :

fomi and
situation

relations of
apex, and
base.

Upper
surface ;

body
root.

Directions. The tongue and larynx are to remain connected with
each other while the students learn the general form and structure
of the tongue.

Dissection. The ends of the extrinsic lingual muscles that have
been detached may be shortened, but enough of each should be left
to trace it afterwards into the substance of the tongue.

The TONGUE is an ovoid, somewhat flattened body, witli the
larger end turned backwards, wliich occupies the floor of the mouth,
and forms a part of the anterior wall of the pharynx. It is free
over the greater part of its surface ; but at the back, and at the
posterior two-thirds of the under surface, it is attached by muscles
and mucous membrane to the parts around.

The tip of the tongue touches the incisor teeth. The base is
attached to the hyoid bone, and is connected likewise with the
epiglottis by three folds of mucous membrane— a central and two
lateral.

The upper surface or dorsum is convex, and in the anterior two-
thirds of its extent is marked by a medium longitudinal groove or
raphe, which terminates behind in a depression of variable depth,
named the foramen ccecum. From the depression a slight lateral
groove is directed outwards and forwards on each side for a short
distance. The part of the tongue in front of the lateral grooves is
distinguished as the body, and is received into the hollow of the roof of
the mouth ; its surface is covered with papilhe. The posterior third
or root of the organ looks into the pharynx ; and its surface is
smoother, although rendered somewhat irregular by projecting
mucous glands and groups of lymplwid follicles, and hj small

STRUCTURE OF THE TONCiUE. r,83

apertures leading into recesses of the mucous membrane. Tlie
untler surface, free only in part, gives attachment to the mucous Lower
membrane and to the different lingual muscles connected with the *^"''^*'^'^-
hyoid bone and the jaw. In front of the muscles the mucous
membrane forms a fold in the middle line, termed the frcenum
lingiice ; and on each side an irregular ridge — ^lica Jimhriata (better
seen in infants), runs forwards and inwards about midway between
the fraenum and the margin of the tongue towards the tip.

Kach border of the tongue is joined opposite the lateral groove Borders,
above mentioned by the fold of mucous membrane descending from
the soft palate, and known as the anterior pillar of the fauces.
Behind this fold, the root of the tongue is attached on each side to
the wall of the pharynx ; but in front the margin of the body is free.
The free border is thick and rounded in its hinder part, where it is
marked by vertical ridges and furrows, and becomes gradually
thinner towards the tip.

Papilla. On the dorsum of the tongue are the following kinds Kinds of
of papillae ; the conical and filiform, the fungiform, and the ^^' '* '
circumvallate. A hand lens may conveniently be used in the
examination of them.

The conical and jiliform papilUe are the numerous small projec- conical
tions which cover the anterior two-thirds of the dorsum of the
tongue. They taper from the base towards the free extremity,
where they are provided with smaller secondaiy papillae ; and
many of them, especially towards the sides of the organ, have their
epithelial covering produced into long hair-like processes, whence
the name filiform is given to them. Towards their limit behind
they are arranged in lines parallel to the lateral grooves, and on the
sides they form vertical rows.

The fungiform papillce are less numerous but larger than the fungiform ;
preceding set, amongst which they are scattered, especially at the
tip and sides of the tongue. They are wider at the free end than
at the part fixed to the tongue, and project beyond the conical
papillae. Their surface is covered with small simple papillae.

The circumvallate papillm are much larger than the foregoing, circumvai-
and are placed at the junction of the middle and posterior thirds
of the tongue. Their number varies from seven to twelve. One,
larger than the rest, is situate immediately in front of the foramen
ca'cum, and the others are disposed in two rows (one on each side)
parallel to the lateral groove, so as to form a figure like a widely-
spread letter V. Each papilla is attached by a constricted stem,
which is surrounded by a groove ; its wider end or base projects
beyond the surface of the tongue, and is covered with small
simple papillae. Around the groove the mucous membrane forms
a slightly prominent fold, which is also beset with secondary
papillae.

Structure. The toncjue consists of two symmetrical halves Parts found

in t/On£zu6

separated by a fibrous layer in the median plane. Each half is
made up of muscidar fibres with interspersed fat ; and entering it are

68i

Define

septum,

hyo-glossal
membrane,

and inferior
lingoalis.

Fibrous
structures
of tongue.

Septum.

Hyo-glossal
membrane.

Submucous
layer.

Muscles in
each half :

two kinds,

Extrinsic :
number.

Dissection
of palato-,
stylo-, and
hyo-glossus.

DISSECTION OF THE TONGUE.

the lingual vessels and nerves. The tongue is enveloped by mucous
membrane ; and a special fibrous layer attaches it to the hyoid boneJ

Dissection. To define the septum, and the membrane attaching!
the tongue to the hyoid bone, the tongue is to be placed on its
dorsum ; and, the remains of the right mylo- and genio-hyoid
muscles having been removed, the genio-glossi muscles are to be
cleaned, and drawn from one another along the middle line. After
separating those muscles, and cutting across their intercommuni-
cating fibres, the edge of the septum will appear. By tracing the
hinder fibres of the genio-glossus muscle towards the hyoid bone,
the hyo-glossal membrane will be arrived at.

On the outer side of the genio-glossus muscle is the longitudina
bundle of the inferior lingualis, which will be better seen subse
quently.

Fibrous tissue. Along the middle line of the tongue is placed a
thin lamina of this tissue, forming a septum ; the root of the tongue
is attached by another fibrous structure, the hyo-glossal membrane ;
and covering the greater part of the organ is a submucous layer of
the same tissue.

Septum. This structure forms a vertical partition between the two
halves of the tongue (fig. 243, b, p. 686), and extends from the base
to the apex, but does not reach to the dorsum. It is thicker behind
than in front, and is connected posteriorly with the hyo-glossal
membrane. To each side the transverse muscle is attached. Its
disposition may be better seen subsequently on a vertical section.

The hyo-glossal memhrcme is a thin but strong fibrous lamina,
which attaches the root of the tongue to the upper border of the
body of the hyoid bone. On its under or anterior surface some of
the hinder fibres of the genio-glossi are inserted, as if this was their
aponeurosis to attach them to the hyoid bone.

The submucous Jibrous stratum of the tongue invests the organ, and
is continued into the sheaths of the muscles. Over the posterior
third of the dorsum its strength is greater than elsewhere ; and in
front of the epiglottis it forms bands in the folds of the mucous
membrane in that situation. Into it are inserted the muscular fibres
which end on the surface of the tongue.

Muscles. Each half of the tongue is made up of extrinsic and
intrinsic muscles. The former or external are distinguished ])y
having only their termination in the tongue ; and the latter, or
internal, by having both origin and insertion within the organ — that
is to say, springing from one part and ending at another.

The extrinsic muscles (fig. 242) are the following : palato-glossus,
stylo-glossus, genio-glossus, hyo-glossus, chondro-glossus, and pharyn-
geo-glossus. Only the lingual endings of these, except in the case
of the chondro-glossus, are now to be studied.

Dissection. After the tongue has been firmly fastened on its left
side, the extrinsic muscles may be dissected on the right half. Three
of these muscles, viz., palato- (d), stylo- (b), and hyo-glossus (c), come
together to the side of the tongue ; and, to follow their radiating

THE EXTRINSIC MUSCLES OF THE TONGUE.

fibres inwards and forwards, it will be necessary to remove from the
dorsum, between them and the tip, a thin layer consisting of the
mucous membrane with the submucous fibrous tissue, and the fleshy
fibres of the upper lingualis. Beneath the tip a junction between
the stylo-glossus muscles of opposite sides is to be traced.

The piece of the constrictor muscle (g) which is attached to the
tongue, and the ending of the genio-glossus will come into view on
the division of the hyo-glossus.

To lay bare the chondro-glossus (p), which is a small muscular
slip attached to the lesser cornu of the
hyoid bone, turn upwards the dorsum
of the tongue, and feel for the small
cornu of the hyoid through the mucous
membrane. Then remove the mucous
membrane in front of this, and the
fibres of the muscle radiating forwards
will be visible.

The PALATO-GLOSSUS reaches the side
of the tongue at the junction of the
posterior and middle thirds. Its fibres
are directed inwards, in part on the
surface, and in part deeply with the
transverse muscle of the septum.

The STYLO-GLOSSUS joins the body of
the tongue below the foregoing, and
is continued forwards as a gradually
tapering bundle beneath the lateral
margin to the tip of the organ, where
it becomes united with the inferior
lingualis, and meets the muscle of the
opposite side. From its upper border
fibres are directed inwards over the
dorsum of the tongue to the middle
line ; and other bundles pass inwards
from its lower edge between the fasci-
culi of the hyo-glossus.

The HYO-GLOSSUS enters the under
surface of the tongue in its middle

685

of i»lia-
rj-iigeo-
glossus,

of chondro-
glossus.

Fig, 242. — Muscles ox the
Dorsum op the Tongue.
(After Zaglas.)

A. Superficial lingualis.

B. Stylo-glossus.
c. Hyo-glossus.
D. Palato-glossus.

F. Chondro-glossus.

G. Pharyngeo-glossus.
H. Septum Hnguae.

Palato-
glossus
in tongue.

Stylo-
glossus pro-
longed to tip
of tongue ;

sends many
fibres in-
wards.

Hyo-

glOSSQS

third, between the stylo-glossus and

the inferior lingualis. Its fibres are collected into bundles which
turn round the margin and form, with those of the preceding
muscles, a layer on the dorsum of the tongue, the hinder fibres
passing almost transversely inwards, the anterior inclining forwards
to the tip.

The CHONDRO-GLOSSUS is a small Ian-shaped muscle, which arises
from the lesser cornu and the adjacent part of the body of the hyoid
bone. Its fibres are directed forwards, spreading out beneath the
mucous membrane of the posterior third of the tongue, and are
insdied into the submucous layer.

united with
palato- and
stylo-
glossus.

Chondro-
glossus.

DISSECTION OF THE TONGUE.

Muscular
cortex of
tonKue.

Geuio-
glossus in
tlie tongue ;

its posterior
fibres.

Constrictor
in the
tongue.

Intrinsic
muscles.

First show
inferior.

then supe-
rior lin-
gualis,

then trans-
versal is.

Trace the
nerves.

Transver-
salis is hori-
zontal :

attach-
ments :

Cortex of the tongue. The muscles above described, together witl^
the superficial lingiialis, constitute a cortical layer of oblique ancfl
longitudinal fibres, which covers the tongue, except below where
the genio-glossus and inferior lingualis muscles are placed, and
resembles "a slipper turned upside down" (Zaglas). This stratum
is pierced by the deeper fibres.

The GENIO-GLOSSUS (fig. 243, a) enters the tongue vertically by
the side of the septum and perforates the cortical covering to end in
the submucous tissue. In the tongue the fibres spread like the rays
of a fan from apex to base, and are collected into transverse lamina3J
as they pass through the trans versalis. The hindmost fibres end oi
the hyo-glossal membrane and the hyoid bone ; and a slip is pro-
longed from them, beneath the hyo-glossus, to the upper constrictoi
of the pharynx. A vertical section at a future stage will show th(
radiation of its fibres.

The PHARYNGEO-GLOSSUS (fig. 242, g), or the fibres of the uppei

constrictor attached to the side o\
the tongue, passes beneath th(
fibres of the hyo-glossus, and ia
continued with the transvei*s€
muscle to the septum.

The intrinsic muscles are four
in number in each half of the
tongue, viz., transversalis, a supe •
rior and an inferior lingualis, and
a set of perpendicular fibres.

Dissection. To complete the
preparation of the inferior lin-
gualis on the right side, the fibres
of the stylo-glossus covering it in
front, and those of tlie hyo-glossus
over it behind are to be cut
through.

The superior lingualis (fig. 242, a) may be shown on the left side,
by taking the thin mucous membrane from the upper surface from
tip to base.

The transversalis ma} be laid bare on the right side, by cutting
away on the upper surface the stratum of the extrinsic muscles
already seen ; and by removing on the lower surface the inferior
lingualis and the genio-glossus, after the former muscle has been
examined.

The nerves of the tongue are to be dissected on the left half as
well as the part will admit ; but a fresh specimen will 1)e required
to follow them satisfactorily.

The TRANSVERSE LINGUALIS MUSCLE (fig. 243, c) fomis a hori-
zontal layer in the substance of the tongue from base to apex. The
fibres are attached internally to the side of the septum, and are
directed thence outwards, the posterior being somewhat curved, to
their insertion into the submucous tissue at the side of the tongue.

Fia. 243.-

-Transversk Section of
THE Tongue.

las.)

Genio-glossus.
Septum linguae.
Transversalis.
Inferior lingualis.

(After Zag-

THE INTRINSIC MUSCLES OF THE TONGUE. 687

Its fibres are collected into flattened bundles, so as to allow the fibi-es in
passage between them of the ascending fibres of the genio-glossus. ^^'^^^ >

Action. By the contraction of the fibres of the two muscles the "^e,
tongue is made narrower and rounder, and is increased in length.

The SUPERIOR LiNGUALis (fig. 242, a) is a very thin layer of Superficial
oblique and longitudinal fibres close beneath the submucous tissue ^*"^**^'* •
on the dorsum of the tongue. Its fibres arise from the fraenum
epiglottidis, and from the fibrous tissue along the middle line ;
from this attachment they are directed obliquely outwards, the
anterior becoming longitudinal, to the margin of the tongue at
which tliey end in the submucous fibrous tissue.

Action. Both muscles tend to shorten the tongue ; and they will use.
bend the point upwards.

The INFERIOR LINGUALIS (fig. 243, d) is much stronger than the Lower
preceding, and is placed on the under surface of the tongue, between ii^guaiis :
the hyo-glossus and genio-glossus. The muscle arises behind from origin ;
the fascia at the root of the tongue ; and the fibres are collected into
a roundish bundle : from its attached surface fasciculi are continued ending;
upwards through the transverse fibres to the dorsum ; and at the
anterior third of the tongue, where the muscle is overlaid by the
stylo-glossus, some of the fibres are applied to that muscle and dis-
tributed with it.

Action. This muscle shortens the tongue, and bends the apex use.
dov/n wards.

The intrinsic perpendicular fibres are found near the border Pei-pendicu-
of the fore part of the tongue, and can be seen only in transverse ^^ ^^^^ ® "
sections. They pass from the submucous tissue of the dorsum
downwards and somewhat outwards, decussating with the cortical
and transverse fibres, to the under surface.

Action. By their contraction these fibres flatten and render u^e.
broader the part of the tongue in which they occur.

Medullary portion of the tongue. The central part of the tongue, Medulla of
which is thus named, is paler in colour and softer than the cortex. "
It is composed mainly of the bundles of the transverse muscle cross-
ing the laminae of the genio-glossus internally and the perpendicular
fibres externally, together with interspersed fat.

The mucous membrane of the tongue is a continuation of that lining Mucous
the mouth, and is provided with a stratified scaly epithelium. It its epithe-'
invests the greater part of the tongue, and is reflected off at different ^'"™-
points in the form of folds. At the epiglottis are three small
glosso-epiglottidean folds, connecting this body to the root of the Folds,
tongue ; the central one of these is called the frcenum of the epiglottis.
It is furnished \nth numerous glands, and lymphoid crypts and
follicles.

The crypts are depressions of the mucous membrane, which are sur- Lymphoid
rounded by lymphoid follicles in the submucous tissue (" the lingual
tonsil"), like the arrangement in the tonsil ; they occupy the dorsum
of the tongue between the circumvallate papillae and the epiglottis,
where they form a stratum close beneath the mucous membrane.

688

and glands
at til e base ;

glands at
the side,

and beneath
tip.

Nerves
from three
sources :

lingual of
fifth.

twelfth,
and ninth.

Arteries,
veins, and
lymphatics.

DISSECTION OF THE LAKYNX.

The lingual glands are racemose, similar to those of the lips and
cheek, and are placed beneath the mucous membrane on the dorsum
of the tongue behind the circumvallate papillae. A few are found
in front of the circumvallate papillae, where thev project into the
muscular substance. Some of their ducts open on the surface and
others in the hollows around the circumvallate papillae, or into the
foramen caecum and the depressions of the crypts.

Opposite the circumvallate papillae, at the margin of the tongue,
is a small cluster of mucous glands. Under the tip of the tongue,
on each side of the fraenum, is another elongated collection of the
same kind of glands embedded in the muscular fibres, from which
several ducts issue.

Nerves. There are three nerves on the under surface of each
half of the tongue, viz., the lingual of the fifth, the hypoglossal, and
the glosso-pharyngeal (fig. 224, p. 624).

The lingiLal nerve sends upwards filaments through the muscular
substance to the mucous membrane of the anterior two-thirds
of the tongue, and supplies the conical and fungiform papillae.
Accompanying this nerve are the lingual fibres of the chorda
tympani.

The hypoglossal nerve is spent in long slender offsets to the mus-
cular substance of the tongue.

The glosso-pharyngeal nerve divides under the hyo-glossus into two
branches. One turns to the dorsum, and ramifies in the mucous
membrane behind the foramen caecum, sujd plying also the circum-
vallate papillae. The other passes to the side of the tongue, and
ends in branches for the mucous membrane, extending forwards to
about the middle of the border.

Vessels. The arteries are derived from the lingual of each side :
the veins pass to the internal jugular trunk. The lymphatics of the
tongue for the most part pass backwards to the upper deep cervical
glands, and have connected with them two or three small lingual
glands on the outer surface of the hyo-glossus muscle ; but some
descend to the submaxillary lymphatic glands.

Section XV.

DISSECTION OF THE LARYNX.

General
construc-
tion of
larynx.

Dissection.

The Larynx is the upper dilated part of the airtube, in which
the voice is produced. It is constructed of several cartilages united
together by ligamentous bands ; of muscles for the movement of
the cartilages ; and of vessels and nerves. The whole is lined by
mucous membrane.

Dissection. The tongue may be removed from the larynx by
cutting through its root, but this is to be done without injuring the
epiglottis.

THE CRICO-THYROID MUSCLE. 689

The student will lind it advantageous to study a museum prepara-
tion of the laryngeal cartilages as described in the next section (pp. 698
to 704) before beginning the dissection of the larynx.

The Larynx is placed in the middle of the neck, in front of the situation
l^liarynx, and in the resting condition opposite the fourth, fifth and
sixth cervical vertebrae. It is however very moveable, its connections varies,
permitting especially a considerable degree of elevation, which comes
into play in the act of swallowing.

Its form is pyi*amidal, the base being turned upwards and attached Form;
to the hyoid bone, while the apex joins the trachea. In length it anddimen-
measures, in the male, about an inch and three-quarters ; in width, male,
at the top nearly as much, and at the lower end one inch ; while
the greatest depth from before backwards is about an inch and a
half. In tlie female, the average length is an inch and a half, and in female,
the depth one inch. Before the age of puberty the larynx is *°** ^° ^^^***
relatively very small.

On each side the larynx is covered by the depressor muscles of Relations,
the hyoid bone, the carotid vessels, and the lateral lobes of the
thyroid body. The front projects beneath the skin in the middle
line of the neck ; and the posterior surface is covered by the mucous
membrane of the pharynx.

Muscles. The stemo-thyroid and thyro-hyoid muscles, which. Muscles,
together with the stylo-pharyngeus and inferior constrictor of the
pharynx, move the larynx as a whole, are frequently called the
extrinsic muscles of the larynx. The intrinsic muscles are six pairs extrinsic
and one single muscle. Of these, one paired muscle is exposed on and
the side of tlie larynx ; two pairs and a single muscle are seen at *'^^"'^^*'^'
the back ; and the rest are concealed by the thyroid cartilage.

Directions. On one side of the larymx, say the right, the muscles Directions,
may be dissected, and on the opposite side the nerves and vessels ;
and the superficial muscles, which do not require the cartilages to
be cut, are to be first learnt.

Dissection. The larynx being extended and fastened with pins, Dissection
the dissector may clear away from the hyoid bone and the thyroid
cartilage the following muscles, viz., omo-hyoid, sterno-hyoid, sterno-
thyroid, thyro-hyoid, and inferior constrictor.

Along the side, between the thyroid and cricoid cartilages, the of the
crico-thyroid muscle (fig. 245, i) will be recognised. miSes!

To denude the posterior muscles (fig. 244), it will be necessary to
turn over the larynx, and to remove the mucous membrane covering it.
On the back of the cricoid cartilage the dissector will find the posterior
crico-arj'tenoid muscle (c) ; and above this, on the back of the aryte-
noid cartilages, the arytenoid muscle (b) will appear, with the crossing
fasciculi of the aryteno-epiglottidean muscles (a) on its surface.

The CRICO-THYROID MUSCLE (fig. 245, ^) is fan-shaped, and is crico-
separated by a triangular interval from the one on the opposite side. ^^^
It arises from the front and the lateral part of the cricoid cartilage ; origin ;
and its fibres radiate to be inserted into the lower comu, and the insertion ;
lower border of the thyroid cartilage as far forwards as a quarter of

D.A. Y Y

690

DISSECTION OF THE LARYNX.

an inch from the middle line ; as well as for a short distance into th(
inner surface of that cartilage. The muscle rests on the crico-thyroid
membrane, and is concealed by the stern o -thyroid muscle,
use. Action. It draws the cricoid cartilage upwards and backwards,

as to increase the distance between the thyroid and the arytenoic
cartilages, and thus tighten the vocal cords.
Posterior The POSTERIOR CRico-ARYTENOiD MUSCLE (fig. 244, c) arises froi

arytenoid is *^^ depression by the side of the vertical ridge at the back of tlit
on back of cricoid cartilage. From this origin the fibres are directed outwardj

cricoid ° . ,....,

cartilage: and upwards, converging to their insertion into the muscular proces
at the outer side of the base of the arytenoid cartilage.

Fig. 244. — Hinder View of the
Larynx.

A. Aryteno-epiglottidean muscle.

B. Arytenoid muscle.

CO. Posterior crico-arytenoids.

Fig. 245. — Side View of the
Larynx.

1. Crico-tbyroid muscle.

2. Thyroid cartilage.

3. Cricoid cartilage.

Kerato-
cricoid.

Ai-ytenoid
muscle lies
on back of
arytenoid
cartilages

Action. It draws the arytenoid cartilage downwards and outwards
to a slight extent, separating this from the one of the opposite side ;
but its principal action is to rotate the cartilage, turning outwards
the vocal process, and thus dilating the glottis.

Kerato-cricoid muscle (Merkel). This is a small fleshy slip which]
is occasionally seen at the lower border of the preceding muscle.
It arises from the cricoid cartilage, and is inserted into the back oi
the lower cornu of the thyroid cartilage.

The ARYTENOID MUSCLE (fig. 244, b) is single, and extends acrossj
the middle line, closing the interval between the arytenoid cartilages
behind. Its transverse fibres are attached on each side to the outer

THE ARYTENOID MUSCLES. fi91

part of the posterior surface of the arytenoid cartilage. On its hinder
surface lie the aryteno-epiglottidean muscles ; and the laryngeal
mucous membrane covers it in front in the space between the
cartilages.

Action. It draws together the arytenoid cartilages, rendering use.
narrower the opening of the glottis.

The ARYTENO-EPIGLOTTIDEAN MUSCLES (a) are tWO small bundles Aryteno-

which cross obliquely from one side to the other on the back of the deln^mus-
arvtenoid muscle. Each arises from the outer and lower part of ^}^^ ^^^^^
the posterior surface of one arytenoid cartilage, and passes to the x :
uj^per part of the outer border of the cartilage of the opposite side,
where a few of the fibres are inserted, but the greater number turn
round this border and end in the aryteno-epiglottidean fold of the
mucous membrane, some reaching the margin of the epiglottis. A
slip is also prolonged into the thyro-arytenoid muscle. The ending
of the muscle will be seen later when the ala of the thyroid cartilage
has been removed.

Action. These muscles bring together the tips of the arytenoid use.
cartilages, and depress the epiglottis, thus assisting to close the
upper aperture of the larynx in swallowing.

Dissection. The remaining muscles (fig. 246, p. 692) will be Dissection
brought into view by removing the greater part of the right ala of muscfes!*^
the thyroid cartilage, by cutting through it a quarter of an inch from
the middle line, alter its lower cornu has been detached from the Remove half
cricoid, and the crico-thyroid muscle taken away. By dividing next ^rtiisS*.
the thyro-hyoid membrane attached to the upper margin, the loose
piece will come away on separating the subjacent areolar tissue
from it.

By the removal of some areolar tissue, the dissector will define Position of
inferiorly the lateral crico-arytenoid muscle ; above it, the thyro- ™"^^ ^'''
arytenoid muscle ; and still higher, the pale fibres of the aryteno-
epiglottidean and thyro-epiglottidean muscles in the fold of mucous
membrane between the epiglottis and the arytenoid cartilage. On
cleaning the fibres of the thjTo-arytenoid near the front of the
larynx, the top of the sacculus laryngis with its small glands will
appear above the fleshy fibres.

The LATERAL CRICO-ARYTENOID MUSCLE (fig. 246, '^j arises from Lateral

the iipper border of the cricoid cartilage at the side, and is directed a^^,ioi(i
backwards to be inserted into the fore part of the muscular process of muscle :
the arytenoid cartilage. It is concealed by the crico-thyroid muscle
and the thyroid cartilage, and its upper border is contiguous to the
succeeding muscle.

Action. It rotates inwards the arytenoid cartilage, opposing the use.
posterior crico-arytenoid muscle, and bringing one vocal cord to the
other, so as to narrow the glottis.

The THYRO-ARYTENOID MUSCLE (fig. 246,*) extends from the thyroid Thyro-ary-

to the arytenoid cartilage ; it is thick below, but thin and expanded muscle
above. The muscle arises from the thyroid cartilage near the middle
line, for about the lower half of its depth, and from the crico-thyroid

Y Y 2

692

DISSECTION OF THE LARYNX.

consists of
outer

aud inner
parts :

some fibres
from aryte-
noid carti-
lage to vocal
cord :

relations

Thyic-
epiglotti
deau
muscle:

membrane. The fibres are directed backwards with different inclina-
tions : — The external (4) ascend somewhat and are inserted into the
outer border of the arytenoid cartilage. The internal fibres (^) are
horizontal, and forma thick bundle which is inserted inio the margins

of the vocal process and the-
lower part of the outer surface
of that cartilage, whilst a few
of the deepest fibres of the
muscle pass from the outer
surface of the vocal process of
the arytenoid cartilage to be
inserted into the true vocal
cord.

The outer surface of the
muscle is covered by the
thyroid cartilage ; and the
inner surface rests on the
vocal cords, and on the ven-
tricle and pouch of the larynx.
Action. The thyro-aryte-
noid draws forwards the aryte-
noid cartilage, and causes the
cricoid to move forwards and
downwards, thus opposing the
crico - thyroid muscle, and
slackening the vocal cords.
It also moves inwards the
fore part of the arytenoid car-
tilage with the true vocal cord,
so as to place the latter in the
position necessary for vocali-
sation. The short fibres pass-
ing from the arytenoid carti-
lage to the vocal cord will
tighten the fore part, and relax
the hinder part of the cord.

The THYRO-EPIGLOTTIDEAN,

MUSCLE is a thin layer whicl
varies much in its develoj
ment in different bodies. Il
fibres arise from the thyroidl
cartilage in conjunction with!
the outer part of the thyro-j
arytenoid, and are directed upwards, covering the outer surface of |
the saccule of the larynx, to be inserted into the margin of the
epiglottis and the aryteno-epiglottidean fold with the aryteno-
epiglottidean muscle. The whole of the muscular fibres passing
from the arytenoid and thyroid cartilages to the epiglottis are
sometimes described together as the depressor of the epiglottis.

Fig.

246. — Internal Muscles of the
Larynx.

1. Crico-thyroid detached.

2. Posterior crico-arytenoid.

3. Lateral crico-arytenoid.

4. Thyro-arytenoid, superficial part.

5. Depressor of the epiglottis, consist-
ing of fibres of the aryteno epiglottidean
muscle and others given off from the
thyro-arytenoid.

6. Thyro-hyoid, cut.

8. Deep part of thyro-arytenoid.

THE GLOTTIS AND THE LARYNGEAL POUCH. 693

Action. This iiinscle draws do^vn wards the epiglottis and aryteno- use.
epiglottidean fold, and assists in closing the upper aperture of the
larynx,

Catity of the larynx and farts inside. On looking into the interior of
cavity of the larynx from above, the tube will be seen to become xEavityis
narrower from above downwards, owing to the projection inwards of constricted
two prominent folds on each side termed the vocal'cords. The lower
or true vocal cords are placed on a level with the bases of the ary-
tenoid cartilages, and the slit-like interval between them is called
the glottis. Below this the cavity enlarges again to the lower
apetiure of the larynx, where it is continued into the trachea.

Upper aperture of the larynx (fig. 233, N, p. 659). This is the orifice Upper open-
by which the larynx communicates with the pharynx. It is tri- '"^'
angular in shape, with the base, which is formed by the epiglottis, form and
turned forwards and upwards. The sides, which are sloped from *^"" ^"^^"
before downwards and backwards, are formed by the aryteno- epi-
glottidean folds of the mucous membrane ; and at the apex is the
arytenoid muscle, with the upper ends of the arytenoid cartilages,
covered by the mucous membrane. This aperture is closed by the
tubercle of the epiglottis during deglutition.

The loicer aperture of the larynx, bounded by the lower edge of Lower open-
the cricoid cartilage, is nearly circular in form, and of the same size '°^"
as the interior of the cartilage.

Dissection. To see the parts within the larynx, the tube is to be Dissection,
divided by a median incision along the back ; but in cutting through
the arytenoid muscle, let the knife be carried a little to the right of
the middle line, so as to avoid the nerves entering it.

On the side wall of the larynx (fig. 247, p. 695) there will now be Parts inside
seen the projecting bands of the vocal cords separated by a depression ^'T^"^'
called the ventricle of the larynx (a). If a probe be passed into this
hollow, it will enter a small pouch — sacculus laryngis (d), by an
aperture at the upper and fore part, under cover of the superior
vocal cord.

The glottis or rima glottidis is the narrowest part of the laryngeal Glottis :
cavity, and is placed on a level with the bases of the arytenoid position,
cartilages. If the cut surfaces of the back of the laiynx be placed forms and
together, it will be seen to have the form of an elongated triangle, boundaries ;
with the base turned backwards. It is bounded on the sides by
the true vocal cords (b) in the anterior two- thirds of its extent,
and by the arytenoid cartilages (e) in the posterior third. In front,
the right and left vocal cords meet at their attachment to the
thyroid cartilage ; and behind, the base is formed by the arytenoid
muscle. The portion of the slit between the vocal cords, being subdivision.
alone concerned in the production of the voice, is distinguished as
the vocal glottis, while the part between the arytenoid cartilages is
termed the respiratory glottis.

The size of the glottis differs in the two sexes ; and its form Size and
undergoes frequent changes during life, caused by the movements of
the arytenoid cartilages and the vocal cords. In the inale, the length,

694

DISSECTION OF THE LARTNX.

and breadth.

Form during
life;

in easy
respiration ;

in forced
inspiration ;

in produc-
tion of the
voice.

Muscles
producing
changes in
glottis.

Ventricle :
situation.

Pouch of
larynx :

form and
position ;

sunounding
parts.

Dissection
of vocal
cords.

interval measures nearly an inch from before backwards ; iv fJf
female, nearly a quarter of an inch less. Its breadth at the biise
is about one-third of the length. The length of the glottis is :
increased by the stretching, and shortened by the relaxation of the
vocal cords.

In quiet breathing the glottis has the triangular form seen after
death, the space being slightly widened in inspiration, and narrowed
in expiration. In forcible inspiration it becomes widely dilated,
the vocal processes of the arytenoid cartilages being directed out-
wards, and the aperture acquiring the form of a lozenge with the
jjosterior angle truncated. The widest part is then opposite the
junction of the vocal cords with the arytenoid cartilages, and its
transverse measurement is about one half of the length. During
vocalisation the cords and the vocal processes of the arytenoid
cartilages are brought together, and the vocal glottis is reduced to a
narrow chink, while the hinder part of the space is closed by the
meeting of the anterior borders of the arytenoid cartilages.

The glottis is rendered longer, and the vocal cords are tightened
by the crico-thyroid muscles ; the opposite effect is produced by the
elasticity of the cords and the contraction of the thyro-arytenoid
muscles. Widening of the glottis is effected by the posterior crico-
arytenoid muscles ; and the cords and arytenoid cartilages are
approximated by the thyro-aiytenoid, lateral crico-arytenoid, and
arytenoid muscles.

The ventricle of the larynx (fig. 247, a) is best seen on the left
side. It is the boat-shaped hollow between the vocal cords, the
upper margin being concave, and the lower nearly straight. It is
lijied by the mucous membrane, and on the outer surface are the
fibres of the thyro-arytenoid muscle. In its roof, towards the front,
is the aperture of the laryngeal pouch.

The laryngeal pouch or sacculus laryngis (fig. 247, d), has been
laid bare partly on the right side by the removal of the ala of the
thyroid cartilage, but it will be opened in the subsequent dissection
for the vocal cords.

It is a small membranous sac, about half an inch long and rather
conical in form, which projects upwards between the false vocal
cord and the ala of the thyroid cartilage, reaching as high as the
upper border of the latter. Its cavity communicates with the fore
part of the ventricle by a somewhat narrow aperture. On the deep
surface of the mucous lining are numerous small glands, the ducts
of which open on the inside. Its outer side is covered by the
thyro-epiglottidean muscle. The size and extent of the pouch vary
greatly in different subjects.

Dissection. The general shape and position of the vocal cords «
are evident on the left half of the larynx, but to show more fully the ■
nature of the lower cord, put the cut surfaces in contact, and detach
on the right side the lateral crico-arytenoid muscle from its cartilages.
Take away in like manner the thyro-arytenoid, raising it from before
back. By the removal of the last muscle an elastic membrane, crico-

THE VOCAL CORDS.

695

thyroid (fig. 249, ^, p. 702), comes into view ; and it ^vill be seen to
be continued upwards into, and give rise to the prominence of the
inferior or true vocal cord. Lastly, dissect off the mucous membrane
from the vocal cords on the right side, and in doing this the wall of
the ventricle and saccule,
which are formed mainly
by this membrane, vvill dis-
appear.

The VOCAL CORDS (fig. 247)
are two bands on each side,
which extend from the angle
of the thyroid to the aryte-
noid cartilage, one forming
the upper, the other the
lower margin of the ventricle
of the larynx. Each consists
of a fold of the mucous
membrane supported by a
ligamentous structure — the
superior and inferior thyro-
arytenoid ligaments respec-
tively.

The superio}' or false vocal
cord (c) is arched with its
concavity downwards, and is
much softer and looser than
the lower. Its free border is
thick and rounded. The
contained superior thyro-aryte-
noid ligament consists mostly
of white fibrous tissue, and
is fixed in front to the angle
of the thyroid cartilage near
the attachment of the epi-
glottis, behind to the middle
portion of the anterior sur-
face of the arytenoid carti-
lage. It is continuous above
with scattered fibrous bun-
dles in the aryteno-epiglot-
tidean fold.

The inferior or triie vocal cord (b) is attached in front to the angle
of the thyroid cartilage about half way down below the notch, and
behind to the vocal process of the arytenoid cartilage. Between
these points, it« free margin, by the vibration of which the voice is
produced, is straight, sharp and smooth. The cord projects upwards
and inwards into the cavity of the larj-nx, and forms the boundary
of the vocal portion of the glottis. It is about jUhs of an inch long
in the male, and ^ths of an inch less in the female. The mucous

and crico-
thyroid
membrane.

Vocal cords:

Superior
cord.

and thjrro-

arytenoid

ligament.

Fig. 247. — Vocal Apparatus, on a
Vertical Section of the Larynx.

A. Ventricle of the larynx.

B. True vocal cord,
c. False vocal cord.

D. Sacculus laryngis.

E. Arytenoid cartilage.

F. Cricoid cartilage.

G. Thyroid cartilage,
n. Epiglottis.

K. Crico-thyroid membrane.
L, Thyro-hyoid membrane.

Inferior
cord,

DISSECTION OF THE LARYNX.

and liga-
ment.

Mucous
membrane
of larynx.

Epithelium

differs in
kind.

Glands.

Dissection
of nerves ;

inferior,

superior
laryngeal

of vessels.

membrane of the true vocal cord is very thin, and intimately united
to the inferior thyro- arytenoid ligament. The latter structure is the
upper edge of the lateral portion of the crico-thyroid membrane, andi
consists of fine elastic tissue, which shows a slight thickening close
its attachment to the thyroid cartilage. On the outer surface of th(
ligament is the deep part of the thyro-arytenoid muscle, some of th(
fibres of which are inserted into the band ; and a thin submucous
layer of elastic tissue is continued outwards from it to line th(
ventricle of the larynx.

The MUCOUS membrane of the larynx is continued from that
lining the pharynx, and is prolonged downwards into the trachea.
At the superior aperture of the larynx it forms the aryteno-epiglotti-
dean fold on each side, between the margin of the epiglottis and the
tip of the arytenoid cartilage : here it is very loose, and the sub-
mucous tissue abundant. In the larynx the membrane lines the
wall of the cavity closely, sinks into the ventricle, and sends a pro-
longation upwards into the laryngeal pouch. On the lower thyro-
arytenoid ligaments it is very thin and closely adherent, allowing
these to be visible through it.

In the small part of the larynx above the superior vocal cords, the
epithelium is of the stratified squamous kind, and free from cilia.
But a columnar ciliated epithelium covers the edges of the superior
cords and the surface below these, though it becomes flattened
without cilia on the lower cords ; on the epiglottis the epithelium
is ciliated in the lower half.

Numerous racemose glands are connected with the mucous mem-
brane of the larynx ; and the orifices will be seen on the surface,
especially at the posterior aspect of the epiglottis. In the edge of
the aryteno-epiglottidean fold there is a little swelling occasioned by
a mass of subjacent glands (arytenoid) ; and along the upper vocal
cord lies another set. None exist over the true vocal cords, but
close to those bands is the collection of the sacculus laryngis, which
moistens the ventricle and the lower vocal cord.

Dissection of nerves and vessels. The termination of the laryngeal-
nerves may be dissected on the left side of the larynx. For this
purpose the half of the thyroid is to be disarticulated from the
cricoid cartilage, care being taken of the recurrent nerve, which lies
close behind the joint between the two. The trachea and larynx
should be fastened down with pins ; and after the thyroid has been
drawn away from the cricoid cartilage, the recurrent laryngeal nerve
can be traced over the side of the latter cartilage to the muscles of
the larynx and the mucous membrane of the pharynx.

Afterwards the superior laryngeal nerve is found as it pierces the
thyro-hyoid membrane, and branches of it are to be followed to the
mucous membrane of the larynx and pharynx. Two communications
are to be looked for between the laryngeal nerves ; one is beneath the
thyroid cartilage, the other in the mucous membrane of the pharynx.

An artery accompanies each nerve, and its offsets are to l)e dis^
sected at the same time as the nerve.

THE NERVES AND VESSELS OF THE LARYNX. 69T

Nerves. The nerves of the larynx are the superior and inferior Nerves are
aryngeal branches of the pneumo-gastric : the former is distributed f™°^^»eus-
o the mucous membrane, and the latter mostly to the muscles.

The inferior laryngeal nerve (recurrent), when about to enter the Recurreut.
larynx, furnishes backwards an offset to the mucous membrane of "^"®
he pharynx ; this joins filaments of the upper laryngeal. The
lerve passes finally beneath the ala of the thyroid cartilage, and supplies
nds in branches for all the special muscles of the larynx, except JJJuscles^
the crico- thyroid. Its small muscular branches are mostly super- except one.
ficial, but that to the arytenoid muscle lies beneath the posterior
crico-arytenoid. Beneath the thyroid cartilage the inferior is joined
by a long offset of the upper laryngeal nerve.

The superior laryngeal nerve (internal division) pierces the thyro- Superior
hyoid membrane, and gives offsets to the mucous membrane of the ^II\q^^
pharynx ; it furnishes also a long branch beneath the ala of the
thyroid cartilage to communicate with the recurrent nerve. The joins recur-
trunk terminates in many branches for the supply of the mucous ^^°*'
membrane : — Some of these ascend in the aryteno-epiglottidean fold
to the epiglottis, and the root of the tongue. The others, which are and ends ia
the largest, descend on the inner side of the sacculus, and supply membrane.,
the lining membrane of the larynx as low as the true vocal cords.
One branch of this set pierces the arytenoid muscle, and ends in the
mucous membrane.

The external branch of the superior laryngeal nerve has previously External
been traced to the crico-thyroid muscle (p. 634). ne7v°!^^

Vessels. The arteries of the larynx are furnished from the Arteries :
superior and inferior thyroid branches.

The laryngeal branch of the superior thyroid artery enters the superior
larynx with the superior laryngeal nerve, and divides into ascending from^^*
and descending branches ; some of these enter the muscles, but the superior
rest supply the epiglottis, and the mucous membrane from the root
of the tongue to the vocal cord. Like the nerves, the two laryngeal
arteries communicate beneath the ala of the thyroid cartilage, and
in the mucous membrane of the pharynx.

The laryngeal branch of the %nferior thyroid artery ascends on the inferior
back of the cricoid cartilage, and ends in the mucous membrane of from inferior
the pharynx and the posterior muscles of the larynx. thyroid;

Some other twigs from the crico-thyroid branch of the superior from crico-
thyroid artery perforate the crico-thyroid membrane, and ramify in a^^.
the mucous lining of the interior of the larynx at the lower part.

Laryngeal veins. The vein accompanying the branch of the Veins,
superior thyroid artery joins the internal jugular or the superior
thyroid vein, and the vein with the artery from the inferior thyroid
opens into the plexus of the inferior thyroid veins.

Xhe lymphatics of the larynx pass to the deep cervical glands. Lympha-

698

DISSECTION OF THE LARYNX.

Section XVI.

THE HYOID BONE, THE CARTILAGES AND LIGAMENTS OF
THE LARYNX, AND THE STRUCTURE OF THE TRACHEA.

Dissectiou.

Hyoid bone ;
form :

body;

cornua,
large

and small.

In larynx
tliere are
four large

and some
small carti-
lages.

Thyroid
cartilage

Dissection. A fresh larynx should be obtained for this Section
if possible. Failing that good use may be made of the parts
remaining in the specimen already examined. All the muscles and-,
the mucous membrane are to be taken away so as to denude the
hyoid bone, the cartilages of the larynx, and the epiglottis ; but the
membrane joining the hyoid bone to the thyroid cartilage, and the
ligaments uniting one cartilage to another on the left side, should
not be destroyed.

In the aryteno-epiglottidean fold of mucous membrane, a small
cartilaginous body (cuneiform) may be recognised ; an oblique
whitish projection indicates its position.

The HYOID BONE (fig. 248) is situate between the larynx and the
root of the tongue. Resembling the letter U placed horizontally,
and with the legs turned backwards, it offers for examination a central
part or body, and two lateral pieces or cornua on each side.

The body (g) is elongated transversely, in which direction it
measures about an inch, and flattened from before backwards.
The anterior surface is convex, and marked in the centre by
a tubercle, on each side of which is an impression for muscular
attachment. The posterior surface is concave and smooth. To
the upper border the hyo-glossal membrane, fixing the tongue, is
attached.

The cornua are two in number on each side — large and small.
The large cornu (h) continues the bone backwards, and is joined to
the body by an intervening piece of cartilage, or in old persons by
continuous bony union. The surfaces of this cornu look rather
upwards and downwards ; and the size decreases from before back-
wards. It ends posteriorly in a tttbercle. The small cornu (j) is
directed upwards from the point of union of the great cornu with
the body, and is joined by the stylo-hyoid ligament ; it is seldom
wholly ossified. It is united to the body of the bone by a synovial
joint, with a surrounding capsule.

Cartilages op the Larynx (fig. 248). There are four large
cartilages in the larynx, by which the vocal cords are supported,
viz., the thyroid, the cricoid, and the two arytenoid. In addition
there are some yellow fibro-cartilaginous structures, viz., the epi-
glottis, a capitulum to each arytenoid cartilage, and a small ovalish
piece (cuneiform) in each aryteno-epiglottidean fold of mucous
membrane.

The THYROID cartilage (b) is the largest of all : it forms the
front of the larynx, and protects the vocal apparatus as with a
shield. The upper part of the cartilage is considerably wider than

THE THYROID AND CRICOID CARTILAGES.

tlie lower, and in consequence of this form the larj'nx is somewhat
funnel-shaped. The fore part is prominent in the middle line in
front, forming the subcutaneous swelling named the pomuTn Adami,
and concave behind, where it gives attachment to the epiglottis, and
to the thyro-arytenoid muscles and ligaments. The upper border is
notched in the centre.

The caitilage consists of two squarish halves or alee, which are
united in front. Posteriorly each
ala has a thick border, which is
continued upwards and down-
wards into a rounded process or
cornu (e and f). Both cornua
are bent slightly inwards : of
the two, the upper (e) is the
longer ; but the lower one (f)
is the thicker, and articulates
with cricoid cartilage. The
inner surface of the ala is
smooth ; the outer is marked by
an oblique line for the attach-
ment of muscles, which extends
from a tubercle near the root of
the upper cornu, to a projec-
tion at the middle of the lower
border.

The CRICOID CARTILAGE (d) is

stronger though smaller than the
thyroid, and surrounds the lower
part of the cavity of the larynx ;
it is partly concealed by the
thyroid cartilage, below which
it is placed. It is something like
a signet ring, being very unequal
in depth before and behind, —
the posterior part being nearly
four times as deep as the anterior.
Its contained space is about as
large as the forefinger.

699

IS convex m
front,

concave
behind:

Fig. 248. — Hyoid Bone ajjd Laryn-
geal Cartilages.

Cricoid
cartilage

form ;

C.C.
D.

F.
lage.

Epiglottis.

Thyroid cartilage.

Arytenoid cartilages.

Cricoid cartilage.

Upper cornu.

Lower cornu of tbvroid

Body of hyoid hone.
Large cornu.
Small cornu.

At the back of the cartilage ^- bo^'er cornu of thyroid carti- surfaces ;
there is a flat and rather square
portion, which is marked on its
posterior surface by a median
ridge between two oval depres-
sions which are occupied by the posterior crico-arytenoid muscles. On
each side, immediately in front of the square part, is a slightly raised
articular facet, which receives the lower cornu of the thyroid cartilage.
The inner surface is smooth, and is covered by mucous membrane.

The lower border is horizontal, somewhat undulatiug, and 'is borders,
united to the trachea by fibrous membrane. The upper border of

700

DISSECTION OF THE LAEYNX.

Arytenoid
cartilages :

situation
and form ;

base ;

fipex ;

surfaces,
Internal,

anterior or
external,

and

posterior.

Fibro-carti.
lages of
Santorini.

Fibro-carti-
lages of
Wrisberg.

Epiglottis

form and
position ;

surfaces,
interior,

the broad part of the cartilage is slightly excavated in the middle,
and is limited on each side by a convex articular facet for the
arytenoid cartilage, which slopes downwards and outwards. In
front of that spot, the border descends rapidly as it passes forwards
to the middle line.

The two ARYTENOID CARTILAGES (c) are placed one on each side
at the back of the larynx, on the upper border of the cricoid carti-
lage. Each is pyramidal in shape, is about half an inch in depth,
and offers for examination a base and apex, and three surfaces.

The base has the form of an elongated triangle, with one of the
angles (the postero-internal) rounded off. Its anterior extremity is
thin and tapering, and gives attachment to the inferior thyro-
arytenoid ligament, whence it is named the vocal process. The
external angle is thick, and projects backwards and outwards, form-
ing the muscular process, into which the crico- arytenoid muscles are
inserted. On the under aspect of the muscular process is an oval,
concave articular facet, sloped downwards and outwards, for the
cricoid cartilage. The apex of the cartilage is directed backwards,
and is surmounted by the cartilage of Santorini.

The inner surface is narrow, especially above, and flat ; and it is
covered by the mucous membrane. The anterior or outer surface
is the largest and irregular, being convex above and concave below.
It is marked near the upper end by a tubercle, and lower down, at
the junction of the middle and lower thirds, by an oblique ridge.
This surface gives attachment to the superior thyro-arytenoid liga-
ment and the thyro-arytenoid muscle. At its posterior aspect the
cartilage is concave and smooth, being covered by the arytenoid
muscle.

Cartilages of Santorini, cornicula or capitula laryngis. At-
tached to the apex of each arytenoid cartilage is the small, conical
fibro-cartilage of Santorini, which is inclined backwards and inwards.
The aryteno-epiglottidean fold is connected with it.

Cuneiform cartilages. Two other small fibro- cartilaginous
bodies, one on each side, which are contained in the aryteno-
epiglottidean folds, have received this name. Each is somewhat
elongated in form, like a grain of rice ; it is situate obliquely in
front of the capitulum of the arytenoid cartilage, and its place in
the fold of the mucous membrane is marked by a slight whitish
projection. These cartilages are often absent.

The epiglottis (fig. 248, a) is single, and is the largest of the
pieces of yellow fibro-cartilage. In form it resembles an ovate
leaf, with the stalk below and the blade above. Its position is
behind the tongue and in front of the orifice of the larynx. Uurin
respiration it is x^laced vertically ; but during deglutition it takes an
oblique direction over the opening of the larynx.

The anterior surface is covered in its upper part by mucous
membrane, which forms the three glosso-eijiglottidean folds (p. 687)
between it and the tongue ; its lower part is attached to the hyoid
bone by fatty tissue containing glands, and by the hyo-epiglottidean

LIGAMENTS OF THE LAKYNX. 701

ligament. The posterior surface is entirely covered by closely and
adherent mucous membrane, and is for the most part concave ; but ^^^ "^^ '
\t the lower end there is an elevation known as the tubercle or
cushion of the epiglottis. To the sides the aryteno-epiglottidean folds sides;
of mucous membrane are united. After the mucous membrane has glands in it.
been removed from the cartilage, its substance Mill be seen to be
excavated by numerous pits, which lodge mucous glands.

In the aduit the hyaline cartilages of the larynx are commonly ossification
to a greater or less extent (in old persons sometimes completely) ^rtu^'^^^*^
converted into bone. The ossification begins in the thyroid and
ricoid cartilages at about twenty years of age, the deposition of
osseous matter in the former taking place first in the neighbourhood
of the inferior cornu, and thence extending along the inferior and
posterior borders; while in the cricoid two or three bony spots
appear near the arytenoid articular surface on each side, and spread
through the upper part of the cartilage. The arytenoid cartilages
ossify later, from below upwards. The tendency to ossification is
more marked in the male than in tlie female.

Ligaments of the Larynx. The larynx is connected by extrinsic Ligameutsi
ligaments with the hyoid bone above and the trachea below. Other "arynx
ligaments unite together the cartilages, sometimes with joints.

Union of the larynx with the hyoid bone and the trachea. A loose To hyoid
elastic membrane (thyro-hyoid) extends from the thyroid cartilage to ?°°he"*^
the hyoid bone ; and a second membrane connects the cricoid cartilage
with the trachea.

The thyro-hyoid membrane (fig. 247, L, p. 695) is attached on the one Thyro-hyoid
hand to the upper border of the thyroid cartilage ; and on the other '"^'^^^"®'
to the upper border of the hyoid bone. Its central part, extending
from the body of the hyoid bone to the margins of the notch in the median and
thyroid cartilage, is of some thickness, but its lateral parts are thin part^
and ill-defined. It ends behind in a rounded elastic cord on each
side (lateral thyro-hyoid ligament), uniting the extremity of the
great cornu of the hyoid bone to the superior cornu of the thyroid thyro-hyoid
cartilage : this band frequently contains a small cartilaginous or Jj^g™®"^
osseous nodule (cartilago triticea). contains

The superior laryngeal nerve and vessels perforate the lateral part ^^ ]^ '
of the membrane : and a synovial bursa is placed between its central
part and the posterior surface of the body of the hyoid bone.

The membrane joining the lower border of the cricoid cartilage Crico'
to the first ring of the trachea, crico-tracheal ligament, resembles membrand,
the fibrous layer joining the rings of the trachea to the other.

Union of the cricoid and thyroid cartila^ges. These cartilages are
united by a membrane in front, and a synovial joint on each side.

The crico -thyroid membrane (fig. 249, *^) occupies the space Crico-
between the thyroid, cricoid, and arytenoid cartilages ; and its right mSrane :
half is now visible. It is of a yellow colour and is formed mainly of
elastic tissue. By its lower border the membrane is fixed to the upper
edge of the cricoid cartilage, reaching back to the articulation with
the arytenoid. Its central part is thick and strong, and is attached median part,

702

and lateral
parts ;

relations.

Crico-
thyroid
joint :

movements.

Crico-
arytenoid
joint and
ligament :

movements,

gliding
and

rotation.

Arytenoid

and

capitulum.

DISSECTION OF THE LAEYNX.

above to the lower border of the thyroid cartilage (see fig. 212, p. 587)
The lateral part is thinner, and is continued upwards beneath the alg
of the thyroid cartilage, to end in a thickened border, which is attached
behind to the vocal process of the arytenoid cartilage, constituting th<
inferior thyro-arytenoid ligament in the true vocal cord.

The central part of the membrane is partly exposed between the
crico-thyroid muscles, and small apertures exist in it for the passag
of vessels into the larynx. The latera
part is separated from thyroid cartilage
by the thyro-arytenoid and lateral crico-
arytenoid muscles. The deep surface of
the membrane is lined by the mucousn
membrane.

The crico-thyroid articulation is formed
between the inferior cornu of the thyroid
and the lateral articular facet of the
cricoid cartilage. A capsular li/jament
which is thickest behind, and lined
by synovial membrane, surrounds the
articulation.

This joint allows of a slight degree ol
gliding movement backwards and for-
wards, and of a rotatory movemen
around a transverse axis, by which th(
front of the cricoid cartilage is raisec
or depressed.

Grico-arytenoid articulation. Between
the cricoid and arytenoid cartilages there
is a synovial joint surrounded by a loose
capsule. To the inner side of the joint
there is a well marked crico-arijtenoid
ligament, which passes from the upper
border of the cricoid cartilage near the
middle line to the adjacent part of the
base of the arytenoid and prevents the
latter cartilage being drawn forwards
over the cricoid.

The arytenoid cartilage glides upwards
and inwards, or downwards and out-
wards, to a slight extent on the oblique
articular facet of the cricoid ; but its prin-
cipal movement is one of rotation, by which the vocal process is carried
inwards and somewhat downwards, approximating the vocal cords and
narrowing the glottis, or outwards and upwards, enlarging the glottis.
Between the apex of the arytenoid cartilage and the capitulum
there is sometimes a synovial joint, but the two cartilages are most
frequently united by connective or fibro-cartilaginous tissue.

The thyro-arytenoid ligaments have been examined with the vocal
cords (pp. 695 and 696).

Fig. 249. — View of the
Vocal Cords and Crico-
thyroid Ligaments.

1. True vocal cord.

2. Posterior crico-arytenoid
muscle.

3. Cricoid cartilage.

4. Arytenoid cartilage.

5. Sacculus laryngis.

6. Lateral part of the crico-
thyroid membrane.

STRUCTURE OF THE TRACHEA. 703

Ligaments of the epiglottis. An elastic band, thyro-epiglottidean Twoiiga-
ligament, connects the lower extremity of the epiglottis to the ™^°K?^

^1 • I ••% 1 1 " -to epiglottis.

thyroid cartilage, close to the notch in the upper border of the
latter (fig. 247) ; and a membranous layer of fibrous and elastic
tissue, hyo-epiglottidean. ligament, passes between the front of the
epiglottis and the hyoid bone.

Structure of the Trachea. The windpipe consists of a series Constitu-
of pieces of cartilage, which are deficient behind, and connected trachel.
together by fibrous tissue. The interval between the cartilages at the
back of the tube is closed by fibrous membrane and muscular fibres ;
and the interior is lined by mucous membrane with subjacent
elastic tissue.

Cartilages. The pieces of cartilages vary in number from sixteen Cartilages:
to twenty. Each forms about three-fourths of a ring, extending form ;
round the front and sides of the airtube. Their arrangement is not irregu-
quite regular throughout, for some of them are often bifurcated at ^^^*^®-
one end, or sometimes two adjacent pieces are partly fused together.
The highest is commonly broader than the others, and may be
joined to the cricoid cartilage. The lowest piece is triradiate, or
V-shaped, a median process being sent downwards and backwards
in the angle between the two bronchi.

The fibrous membrane ensheaths the cartilages, and, being con- Fibrous
tinned across the intervening spaces, binds them together. It also ***^^'^'
extends across the posterior part of the trachea.

. Dissection. On removing the fibrous membrane and the mucous Dissection,
glands from the interval between the cartilages at the back of the
trachea, the muscular fibres will appear.

Aft€r the muscular fibres have been examined the membranous
part of the tube may be divided, to see the elastic tissue and the
mucous membrane.

Muscular fibres. Between the ends of the cartilages is a continuous Muscular
layer of transverse bundles of unstriated muscle, which is attached ^ck!*
to the truncated ends and the adjacent part of the inner surface of
the cartilaginous hoops. By the one surface the fleshy fibres are in
contact with the fibrous membrane and glands, and by the other
with the elastic tissue. Some longitudinal fibres are superficial to
the transverse ; they are arranged in scattered bundles, and are
attached to the fibrous tissue.

The elastic tissue forms a complete lining to the trachea beneath Submucous
the mucous membrane ; and at the posterior part, where the carti- tissue!
lages are wanting, it is gathered into strong longitudinal bundles.
This layer is closely connected with the mucous membrane
covering it.

The mucous membrane of the trachea lines the tube, and is Mucous
furnished with a columnar ciliated epithelium. epithelium'

Connected with this membrane are numerous branched mucous and glands.
glands of variable size. The largest are found at the back of the
trachea, in the membranous part of the wall, where some are placed
outside the fibrous layer, and othei-s between that membrane and

704

DISSECTION OF THE NECK.

"Vessels and
•nerves.

the muscular fibres. Smaller glands lie beneath the mucou
membrane.

Other small glands are found at the front and sides of the trachea
being situate on and in the fibrous tissue connecting the cartilaginou
rings.

The arteries of the trachea are derived from the inferior thyroi(
and bronchial. The veins have a corresponding disposition. Nerve
are supplied to the tube from the vagus, mainly through the recur
rent laryngeal, and from the sympathetic.

Section XVII.

PREVEETEBKAL MQSCLES AND VERTEBRAL VESSELS.

^Muscles in
front of
spine.

Dissection.

^onguB colli
in three
parts:

vertical,

superior
-oblique,

and inferior
■oblique ;

parts in
contact
with it:

Directions. On the piece of the spinal column which was laic
.aside after the separation of the pharynx the student is to learn th(
•deep muscles on the front of the vertebrae.

Dissection. The prevertebral muscles will be prepared by re
moving the fascia and areolar tissue. They are three in number ol
each side (fig. 250), and are easily distinguished. Nearest the middL
line, and the longest, is the longus colli (a) ; the muscle external t(
it, which reaches to the head, is the rectus capitis anticus major (b)
and the small muscle close to the skull, which is external to the las
and partly concealed by it, is the rectus capitis antic as minor (g). Th
smaller rectus muscle is often injured in cutting through the basila
process of the occipital bone in separation of the pharynx.

The LONGUS COLLI MUSCLE (a) is situate on the bodies of th<
cervical and upper dorsal vertebrae, and is pointed above anew
ibelow. It consists of three parts, one internal or vertical and two
external or oblique, which differ in the direction of their fibres, but
are closely] united together. The vertical part arises by fleshy and
tendinous processes from the bodies of the upper two dorsal and
lower two cervical vertebrae, and from the front of the transverse
processes of the lower three cervical vertebrae. It is inserted bj4
similar slips into the bodies of the second, third, and fourth cervical
vertebrae. The upper oblique part is inclined inwards. It arises from
the anterior tubercles of the transverse processes of the third, fourth,
and fifth cervical vertebrae, and is inserted into the side of the tubercle
oh the anterior arch of the atlas. It is generally joined by a slip
from the upper end of the vertical part of the muscle. The lower
oblique part, passing in the opposite direction to the last, arises in
common with the vertical part from the upper dorsal vertebrae, and is
inserted into the transverse processes of the fifth and sixth cervical
vertebrae.

In contact with the anterior surface of the longus colli are the
pharynx and the oesophagus. The inner border is at some distance
from the muscle of the opposite side Ijelow, but above only the

RECTUS CAPITIS ANTICUS MAJOR. 705

*^ loiiited anterior common ligament of the vertebrae separates the
wo. The outer border is contiguous to the anterior scalenus, to
^'■"^e vertebral vessels, and to the rectus capitis anticus major. The
'•'^^ Lumber and attachments of the slips of this muscle are subject to
Teat variation.
Action. Both muscles bend forwards the neck ; and the upper use.
""^blique part of one may rotate the head to the same side.

The RECTUS CAPITIS ANTICUS MAJOR (b) is external to the preceding Rectus
Duscle, and is largest at the upper end. Its origin is by pointed mj^o"f
endinous slips from the anterior tubercles of the transverse processes origin;

Fig. 250. — Deep Muscles of the front of the neck, and
the scaleni.

A. Longus colli. d. Scalenus medius.

B. Rectus capitus anticus major. k. Scalenus posticus.

0. Scalenus anticus. g. Rectus capitis anticus minor.

of the third, fourth, fifth, and sixth cervical vertebrae ; and the fibres insertion ;
ascend to be inserted into the basilar process of the occipital bone
by the side of the pharyngeal tubercle, reaching from the middle Une
to the petrous portion of the temporal bone.

This muscle partly conceals the longus colli and rectus anticus relations;
minor. Its anterior surface is in contact with the pharynx, the
internal and common carotid arteries, and the sympathetic nerve.
The origin from the cervical vertebrae corresponds with that of the
scalenus anticus.

Action. It flexes the head and the cervical portion of the spine, use.

D.A. zz

706

Rectus
anticus
minor is
beneath
preceding i

Dissection
of inter-
transver-

Inter-
transverse
muscles :
number
and attach-
ments ;

relations ;

Cervical
nerves in
their fora-
mina give

and pos-
terior
branches.

First two

nerves

differ:

anterior and

posterior
branches.

DISSECTION OF THE NECK.

The. RECTUS CAPITIS ANTICUS MINOR (g) is a siiiall flat muscle
which arises from the front of the lateral mass of the atlas at tin
root of the transverse process, and is inserted into the basilar proces;
of tlie occipital bone behind the last muscle, and half an inch frou
its fellow.

The anterior primary branch of the suboccipital nerve emerge.'
between the borders of this muscle and the rectus capitis lateralis.

Action. It helps in bending forwards the head. .

Dissection. The small intertransverse muscles will come intr
view when the other muscles have been removed from the front and
back of the transverse processes. By tracing towards the spine the
anterior primary branches of the cervical nerves, the intertransver-
sales will be readily seen in front of and behind them.

After the muscles and nerves have been examined, the tips of th
transverse processes may be cut off to lay bare the vertebral artery.

The INTERTRANSVERSE MUSCLES are slender fleshy slips in th(
intervals between the transverse processes. In the neck there are
six pairs on each side — the first being l)etween the atlas and axis,
One set is attached to the anterior, and the other to the posterioj
tubercles of the transverse processes.

The anterior primary divisions of the corresponding spinal nervei
issue between these muscles ; and the posterior primary divisions lie
to the inner side of the hinder muscles. Between the atlas and thi
occipital bone the rectus anticus minor and rectus lateralis represent^
intertransverse muscles.

Action. By approximating the transverse processes these muscles
bend the spinal column laterally.

Cervical nerves at their exit from the spinal canal.
The trunks of the cervical nerves issue from the spinal canal through
the intervertebral foramina, except the first two, and bifurcate into
anterior and posterior primary branches.

The anterior 'primary branch passes outwards between the inter-
transverse muscles, and joins with its fellows in the plexuses already
described.

The -posterior primary branch turns to the l)ack beneath the
posterior intertransverse muscle and the other muscles attached toj
the posterior parts of the transverse processes ; in its course it lie;
close to the bone between the articular processes of the vertebra.

Peculiarities in the first tivo. The first two nerves leave the spina"
canal above the neural arches of the atlas and axis, and divide at
the back of the neck into anterior and posterior branches.

The anterior pimary branch of the first or suboccipital nerve has
been examined (p. 636). The anterior branch of the second nerve,
after perforating the membrane between the neural arches of the
first and second vertebrae, is directed forwards outside the vertebral
artery, and between the two intertransverse muscles of the first
space, to join the cervical plexus.

The posterior primary branches of the first two nerves are described
in the dissection of the l)ack.

THE VERTEBRAL VESSELS. 707

The VERTEBRAL ARTERY Lus been seen at its origin in the lower Vertebral
part of the neck (p. 593) ; and its termination is described with the neckT '"
vessels of the brain. Entering, usually, the foramen in the sixth course ;
cervical vertebra the artery ascends through the corresponding
foramina in the other vertebrae. Finally, the vessel winds back-
wards round the upper articular process and crosses the neural arch
of the atlas, piercing the posterior occipito-atlantal ligament and the
dura mater, to enter the skull through the foramen magnum. In
its course upwards the artery lies in front of the anterior trunks of relation to
the cervical nerves, except the first, which crosses on the inner side. *'"^^^^'

The vessel is accompanied by a vein, and by a plexus of nerves of a vein, and
,1 nerves are

the same name. with it ;

In the neck the artery furnishes small twigs to the surrounding branches,
muscles, the spinal canal, and the spinal cord.

The vertebral vein begins on the neural arch of the atlas by the Vertebral
union of a considerable offset from the intraspinal venous plexuses
with other branches proceeding from a network between the muscles
in the suboccipital region. It is also joined by the emissary vein
leaving the skull through the posterior condylar foramen when that
aperture is present. In the neck, the vein forms a plexus around course ;
the artery in the foramina of the transverse processes ; and it termi-
nates below by emptying itself into the innominate trunk. ending ;

In this course it is joined by branches from the internal and branches,
external spinal veins ; its other tributaries are noticed at p. 594.

The vertebral plexus of nerves is derived from the inferior cervical Vertebral
ganglion of the sympathetic. It surrounds the artery, and com- nerves,
municates with the spinal nerves which it crosses.

vein ;
origin

Section XYIII.

LIGAMENTS OF THE VERTEBRA AND CLAVICLE.

Directions. On the remaining part of the spine, the ligaments Directions,
connecting the cervical vertebrse to each other and to the occipital
bone are to be learnt.

Dissection. Disarticulate the last cervical from the first dorsal Dissection,
vertebra. Then remove altogether the muscles, vessels, nerves, and
areolar tissue and fat from the cervical vertebrae. By sawing through
the occipital bone, so as to leave only an osseous ring behind the
foramen magnum, the ligaments between the atlas and the occipital
bone can be more easily cleaned.

The COMMON LIGAMENTS attaching together the cervical vertebrae Common
are similar to those uniting the bones in other parts of the spine, vfrtebra
viz., an anterior and a posterior common ligament, bands between
the laminae and spines, capsular ligaments lined by synovial mem-
brane for the articular processes, and an intervertebral disc between
the bodies of the bones.

z z 2

708

DISSECTION OF THE NECK.

are

described

elsewhere.

Special
ligaments

between
first two
vertebrae
and occipi-
tal bone.

Directions. The common ligaments will be best seen on the dorsa
or lumbar portion of the spine, where they are more stronglj
developed ; their preparation and description will be found at the
end of the thorax, with the description of the ligaments of the spintj
(pp. 492 to 498). Should the student examine them in the neckj
to see their difference in this region, he should leave uncut the neural
arches of the upper two vertebrifi, to which special ligaments are
attached.

Special ligaments unite the first two cervical vertebra? to eacli
other and to the occipital bone : some of these are external to. and
others within the spinal canal.

The ligaments outside the spinal canal are fibrous membranes,
which connect the axis to the atlas, and the latter to the occipital

Fig. 251,-

-ExTERNAL Ligaments in front between the Occipital Bone,
Atlas, and Axis. (Bourgery.)

1. Sawn basilar process.

2. Capsule of articulation between
occipital bone and atlas, internal to
which is the anterior occipito-atlantal

ligament.

3. Anterior atlan to-axial.

4. Lateral articulation between the
atlas and axis opened.

Anterior
ligament
between
atlas and
axis,

bone in front and behind. Capsular ligaments also surround the
articulations formed by these bones on each side, but they will be
examined more conveniently after the spinal canal has been opened.
The anterior atlanto-axial ligament (fig. 251, ^) consists of a mem-
branous layer attached to the anterior arch of the atlas and the body
of the axis, and a superficial thickened band in the centre, prolonged
from the upper end of the anterior common ligament, and connect-
ing the ridge on the front of the axis to the tubercle on the anterior
arch of the altas.
and between The anterior occipito-atlantal ligament (fig. 251,^) resembles the
ocdpite? foregoing, and passes from the basilar process of the occipital bone,
bone. immediately in front of the foramen magnum, to the anterior arch

of the atlas. Its central part is also thickened, and is fixed to the
tubercle on the front of the atlas.

THE LIGAMENTS OF THE ATLAS AND AXIS.

709

The posterior occipito-atlantal ligament {^g. 252, ^) is a thin broad Posterior
membrane, the deep surface of which is intimately united to the bftween

occipital
bone and
atlas,

Fig. 252. — External Ligaments behind between the Occipital Bone,
Atlas, and Axis.

1. Posterior occipito-atlantal liga- 3. Vertebral artery entering be-
Dient. neath the occipito-atlantal ligament.

2. Posterior atlanto-axial.

dura mater. It is attached above to the hinder margin of the
foramen magnum of the occipital bone, and below to the posterior
arch of the atlas. Behind the upper articular process of the altas

Fig. 253. — Internal Ligaments between the Occipital Bone, Atlas,
AND Axis. First view. (Bourgery.)

1. Long occipito- axial ligament.

2. Beginning of the posterior common ligament.

it forms an arch over the groove of the bone in this situation,
bounding with the latter an aperture through which the vertebral
artery and the suboccipital nerve pass.

710

and between
atlas and
axis.

Internal
ligaments
between
same bones.

Dissection
of the liga-
ments.

DISSECTION OF THE NECK.

The posterior atlanto-axial ligament (^) is also thin, and adherent tc
the dura mater. It closes the interval between the neural arches ol
the atlas and axis, and is pierced on each side by the second cervical
nerve.

The ligaments inside the spinal canal are much stronger, and
assist in retaining the skull in place during the rotatory and nodding,
movements of the head. Between the occipital bone and the second
vertebra are four ligaments — a long occipito-axial with a central
and two lateral odontoid ; and the odontoid process of the axis is
fixed against the body of the atlas by a transverse band.

Dissection (fig. 253). Sui)posing the neural arches of the cervi
vertebrae to be removed except in the first two, the arches of the
A'ertebrse are to be sawn through close to tlie articular processes.
Next, the ring of the occipital bone bounding posteriorly the

Fig. 254. — Intkrnal Ligaments between the Occipital Bone, Atlas,
AND Axis. Second view. (Bourgery.)

1. Check ligament.

2. Transverse ligament, sending
offsets upwards and downwards.

3. Cut end of long occiijito-axial
ligament.

Long
occipito-
axial
ligament.

foramen magnum is to be taken away. Lastly, the student should
detach the tube of dura mater from the interior of the spinal canal ;
and, by following upwards the posterior common ligament of the
bodies of the vertebrae, its continuation, the long occipito-axial
ligament will be exposed.

The long ox posterior occipito-axial ligament (fig. 253) is a strong flat
band which continues upwards the posterior common ligament of the
vertebrae. It is broad above, where it is attached to the upper
surface of the basilar process of the occipital bone, reaching outwards
on each side as far as the insertion of the check ligaments. Descend-
ing thence through the foramen magnum, and over the odontoid
process, it becomes somewhat narrower, and is inserted mainly into
the back of the body of the axis, but many of the superficial fibres
are prolonged into the posterior common ligament. Occasionally a
bursa is found between it and the transverse ligament.

THE ODONTOID LIGAMENTS. 711

Dissection (tig. 254). After the removal of the long occipito-axial Dissection
ligament, by cutting through it transversely above, and reflecting ye^"**
it downwards, the student should define a strong band, the trans-
verse ligament, which crosses the neck of the odontoid process, and
sends upwards and downwards a slip to the occipital bone, and the
axis. The upper offset from the transverse ligament may be cut
through afterwards for the purpose of seeing the odontoid ligaments,
which radiate from the process, the central one being a slender band and odontoid
in the middle line, and the lateral, much stronger, passing nearly ^^s*™^'^^-
horizontally outwards.

The transverse ligarnent of the atlas (fig. 254, "^ and fig. 255, ') is a xoflx
strong arched band behind the odontoid process, which is attached odontoid

° . . process

on each side to a tubercle on the inner surface of the lateral mass is the
of the atlas, below the fore part of the upper articular process. The u^^en^
ligament is rounded at each end, but flattened and wider in the
middle ; and at this spot it has a band of longitudinal fibres con- also named
iiected with its upper and lower margins (fig. 254, '^) so as to produce ^'■""^**"^

Fig. 255. — Atlas with the Transverse Ligament.

1. Transverse ligament with its offsets cut.

2. Space occupied by the odontoid process.

a cruciform figure : the upper band is inserted into the basi-
occipital, and the lower into the body of the axis. Towards the
spinal canal it is concealed by the long occipito-axial ligament.

This ligament form^j, with the anterior arch of the atlas, a ring Socket for
(fig. 255, 2) which surrounds the neck of the odontoid process of the pr^ss\
axis, and prevents sej^aration of the bones.

The lateral odontoid or check ligarnents (fig. 254, ') are two strong Check
bundles of fibres, attached by one end to a flat impression on each ^s*™®"^
side of the head of the odontoid process, and by the other to a
rough mark on the inner surface of the condyle of the occipital
bone. These ligaments are covered by the long occipito-axial band :
their upper fibres are short and nearly horizontal ; the lower are
longer and oblique.

The central odontoid ligament is a small median cord, which Suspensory
passes from the tip of the odontoid process to the anterior margin of ^s*™^'^*-
the foramen magnum.

When the transverse and odontoid ligaments have been cut Articular
through, the odontoid process will be seen to have two cartilage- "odontoid**

712

DISSECTION OF THE NECK.

covered surfaces, which correspond to as many synovial sacs. One :
surface is on the front of the process, and articulates with the
anterior arch of the atlas; the other is the floor of the groove
behind the neck of the process, and is in contact with the transverse
ligament. The posterior synovial sac is larger than the anterior.

OcciPiTO-ATLANTAL ARTICULATIONS. A Synovial joint is formed
between the condyle of the occipital bone and the upper articular pro-
cess of the atlas on each side. Surrounding the articulation is a
capsular ligament of scattered fibres, which is strongest externally and
in front. When the joint is opened, the elliptical articular surface of
the condyle will be seen to be convex in all directions, and to look
outwards as well as downwards. The articular cavity of the atlas
has a corresponding direction, upwards and inwards, and is marked by
a slight transverse groove, from wdiich the cartilage is often wanting.
Atlanto-axial articulations. Three synovial joints exist
between the atlas and axis. The central articulation is between the
anterior arch of the atlas and the odontoid process, and has already
been exposed. The lateral articulations are formed on each side by
the inferior articular process of the atlas and the upper articular
surface of the axis. These are united by a loose capsule (fig. 251, ■*,
p. 708), which is thickened so as to give rise to an accessory ligament
at the inner and posterior aspect of the joint. The articular surface
of the axis is somewhat convex, and is sloped downwards and
outwards ; while that of the atlas presents a slight transverse ridge
in the middle, so that the opposed surfaces are more extensively in
contact when the atlas is turned to one side, than when it is placed
symmetrically over the axis.

Movements of the head. The head can be bent forwards —
flexion, or backwards — extension ; it can be inclined towards the
shoulder — lateral flexion ; and it can be turned to either side —
rotation.

Flexion and extension take place in the joints between the atlas
and occipital bone ; and the range of movement is greater in the
forward than in the backward direction. Flexion is limited mainly
by the long occipito-axial and the check ligaments ; extension by the
anterior occipito-atlantal ligament, and by the apj)roximation of the
occipital bone to the neural arch of the atlas. When the head is
moved more freely, flexion and extension of the cervical portion of
the spine come into play.

Lateral flexion is effected mainly by movement between the
place tn*^^^ cervical vertebrae ; but a very slight degree may be due to move-
ment having its seat in the occiiDito-atlantal articulations.

Rotation takes place in the atlanto-axial articulations, the atlas
and head moving together round the pivot formed by the odontoid
process. The movement is stopped by the check ligaments. Less
than half of the whole possible rotation of the head is obtained
and in neck, between the atlas and axis, the rest being made up in the neck,
sterno- Sterno-clavicular ARTICULATION (fig. 256). The articular

SicuStion sui"faces of the two bones are not precisely adapted to each other,

process,
and two
synovial
sacs.

Occipito-
atlantal
articula-
tions are
condyloid
joints :

articular
surfaces.

Between
atlas and
axis are a
pivot-joint
and two
gliding
joints :

articular
surfaces of
latter.

Movements
of head,
kinds of.

Nodding
movement :
seat, extent,
and checks.

Inclination

neck.

Turning
movement
between
atlas and
axis;

THE STERNO-CLAVICULAR ARTICULATION.

713

IS a com-

aiid an interarticular fibro-cartilage is placed between them. They
are united by a capsular ligament ; and the clavicle receives addi- ^^^

tional support from a ligament passing to the first rib-cartilage, and
from another band connecting it to the bone of the opposite side.

Dissection. For the examination of the ligaments of the sterno- Dissection,
clavicular articulation, take the piece of the bones that have been
set aside. If the ligaments have become dry, they may be moistened
for a short time. The several ligaments will be seen in the situation
indicated bv their names, after the removal of some connective tissue.

Fig. -ioti.-

-llgaments of the ixner end of the claviolt, and of the
Cartilage of the Second Rib.

1. Capsule.

2. Costo- clavicular ligament.

3. Interclavicular ligament.

4. Anterior ligament of the second
choncho-sternal articulation.

6. Interarticular ligament of the
same joint.

7. Interarticular fibro-cartilage be-
tween the sternum and clavicle.

The capsular ligament (fig. 256, ') is a stout membrane surrounding Fibrous
the articular portions of the bones and the fibro-cartilage. Its fibres '^P'*"^^-
run obliquely from the clavicle downwards and inwards to the
sternum. The stronger parts in front and behind are described as
the anterior and posterior sterno-clavicular ligaraents.

The interclavicular ligament (fig. 256, ^) extends above the sternum, inter-
between the ends of the clavicles. The fibres dip into the hoUow *^^*^^^"'^''
Ijetween the collar-bones, and are connected with the upper edge of
the sternum.

The costo-clavicular or rhomboid ligament (fig. 256, 2) is a short and costo-
strong band of oblique fibres, passing from the upper surface of the jJjaiSt!

714

DISSECTION OF THE NECK.

Fibro-
cartilage ;

attach-
ments.

Two

synovial
sacs.

Motion in

four

directions.

cartilage of the first rib lo a rough mark on the under surface of
the clavicle near the sternal end. In front of the ligament is the
origin of the subclavius muscle. Sometimes the ligament is hollow,
and contains a synovial bursa.

The interarticidar fibro-cartilage (fig. 256, ') will come into view
by cutting the ligaments before described, and raising the clavicle.
It is ovalish in form and flattened, and is thicker at the circumference
than in the centre. Its upper margin is firmly united to the inner
end of the clavicle ; and below, it is similarly fixed to the cartilage
of the first rib. At its circumference it unites with the capsule of
the joint. The fibro-cartilage is of considerable strength, and
prevents the clavicle being displaced upwards or inwards.

Two synovial sacs are present in the articulation, one on each side
of the fibro-cartilage. The external one is prolonged outwards for a
short distance below, between the clavicle and the cartilage of the
first rib.

Movements. The clavicle can be moved upwards and downwards
and forwards and backwards ; but the extent of movement in each
direction is very limited, in consequence of the shortness of the
ligaments surrounding the articulation : the forward and upward
movements are freer than the opposite. In the upward and down-
ward movements, the clavicle glides on the interarticular fibro-
cartilage ; and when the shoulder is depressed, the inner end of the
bone is raised, while elevation of the shoulder is accompanied by a
sinking of the inner end of the clavicle. In the forward and
backward movements, the fibro-cartilage glides in the same direction
over the sternal articular surface. Dislocation may take place in
any direction, except downwards ; but it is of rare occurrence owing
to the strength of the ligaments.

CHAPTER X.
DISSECTION OF THE BRAIN.

Section I.

MEMBRANES AND VESSELS.

Directions. The workers on the head and neck examine the
brain together, and it is most desirable that, at the time of its
removal from the head, they should obtain a second specimen, so that A second
the minor cutting operations should be performed on one and the desirable,
other left in its entirety till the study of the cerebral hemispheres is
commenced. Notwithstanding this, however, the directions for
dissection are given as far as possible so that one specimen should
suffice. Both l»rains will be preserved according to the subjoined
instructions.

Preservation and dissection. After the removal of the brain
with its divesting membranes as directed on pp. 509 et seq, it should be
thoroughly washed free of blood and then placed, with its under
surface upwards, in a good-sized earthenware jar provided with a
well-titting co^er. The brain should rest on a large, loose, pad of
tow or cotton wool spread over the bottom of the jar, and the vessel Preserve iu
should contain a 5 per cent, solution of formalin in water in sutficient go^J".
quantities to cover the brain with a clear inch of liquid. The
membranes and vessels, as described in this Section, should be
examined as soon as possible after the specimen has been in the
preservative for two days ; for the reason that they are more easUy
traced whilst the preparation is still moderately soft, and that they
can then be more readily removed without injury to the brain
substance ; moreover, it is necessary to remove them at an early stage
in order to give the hardening fluid free access.

When the preparation is removed from the jar for the examination
of the membranes and vessels, it should be well washed in running
water to remove the adhering formalin solution, which is apt to be
inconvenient to the dissector by the lachrymation it causes.

In describing the distribution of the blood vessels it is unavoidable
to refer to various parts of the brain that have not yet been examined
in detail, and it is therefore desirable that the student should have at
hand a museum preparation in which the convolutions and sulci are
clearly dehned and marked (see fig. 270, p. 746, and fig. 273, p. 753).

716

DISSECTION OF THE BRAIN.

Outline of

cranial

mass.

Medulla
oblongata.

Pons Varolii

and its
fonuections.

Cerebellum.

Cerebrum,

and its great
divisions.

Weight of
brain.

Three
membranes.

Dura mater

Arachnoid
membrane :

relations
to sulci ;

Subdivisions of the encephalon. Before the description of
the membranes and vessels is given, the chief subdivisions of the
encejihalon may be shortly noticed.

The cranial or encephalic mass of the nervous system (fig. 268,
p. 741), consists of cerebrum or great brain, cerebellum or small brain,
pons, and medulla oblongata. Each of these parts has the following
situation and subdivisions : —

The medulla oblongata, or bulb of the spinal cord (fig. 268, a), lies
in the groove between the halves of the cerebellum, and is divided
into two symmetrical parts by a median fissure. To it several of the
cranial nerves are united.

The pons Varolii (d) is situate above the medulla oblongata,
and is marked along the middle by a groove, which indicates a
separation into halves and which lodges the basilar artery. Above it
are two large processes (crura cerebri, /) connecting it to the
cerebrum ; and on each side it is united to the cerebellum by a
similar white mass.

The cerebellum (b), or the small brain, is separated into two
hemispheres by a median groove ; and its surface is marked by
concentric lamina3.

The cerebrum (r and p\ or the large brain, is divided into two
hemispheres by a longitudinal fissure in the middle line ; and each
hemisphere presents a deep transverse cleft — the fissure of Sylvius.
The surface of the hemispheres is convoluted.

The average weight of the brain in the European male is about
49 oz. ; in the female about 44 oz.

Membranes of the Brain. The coverings of the brain (meninges)
are three in number, viz., dura mater, arachnoid, and pia mater. The
dura mater is a firm fil^rous investment, which separates and supports
the different parts of the brain, and serves as an internal periosteum to
the cranial bones. The pia mater is the most internal layer ; it is
adherent to the brain substance and contains the ramifications of the
vessels of the brain. The arachnoid, which is interposed between
the other two, is the membrane that is seen when the brain is
removed from the cranial cavity.

Besides enveloping the brain, these membranes are prolonged on
the cord into the sjDinal canal. Only the cranial part of tlie last
two will be now noticed. For the description of the cranial portion
of the dura mater, see pp. 507 et seq.

The ARACHNOID is a very thin fibrous membrane, which envelopes
the brain loosely, and is separated from the dura mater by the
interval named the subdural i^pace and from the pia mater by the sub-
arachnoid space. Its outer surface is free and smooth and in the
natural state is in close apposition to the dura mater. The inner
surface is attached to the pia mater by numerous fine cords and
bands, which cross the subarachnoid space. The membrane covers
the convolutions and laminae of the large and small brain, bridging
over the sulci between them, and at the under surface or base of the
brain it stretches across from side to side between the cerebral

THE ARACHNOID AND THE PI A MATER. 717

liemispheres, so as to leave a considerable space beneath it. Superiorly,
it is prolonged into the median fissure between the cerebral hemi-
spheres as far as the falx cerebri, but does not reach to the bottom of
the cleft.

The arachnoid forms tubular sheaths on the nerves leaving the sheaths on
cavity of the cranium which enter the apertures in the dura mater, "®"'^''
and then terminate in a free edge ; but around the vessels passing to and vessels.
or from the brain, the membrane joins the dura mater.

The subarachnoid space is filled, by a watery fluid named cerebro- Subarach-
spinal. The space varies greatly in size at different parts. Over the varies in
convolutions and prominences of the brain the arachnoid approaches extent:
the pia mater closely, and the interval between them is very small ;
but opposite the sulci and depressions of the surface the space is
expanded. The largest cavity {cisterna vmgna) is between the cere-
bellum and medulla oblongata, \vhere the arachnoid is reflected from
the one to the other, being widely separated from the pia mater which
follows the surfaces. By an aperture in the pia mater at the depth three large
of this space the subarachnoid space is placed in communication
■ ith the fourth and, ultimately, with the other ventricular cavities

the brain. Another considerable subarachnoid space {cisterna

<aUs) exists between the cerebral hemispheres in front of the pons
ith extensions outwards into the fissures of Sylvius and backwards

the cisterna magna ; and a third extends the whole length of the

ipus callosum, in the great longitudinal fissure.

The PIA MATER closely invests the brain, following all inequalities Pia mater
of the surface, and dips into the sulci of the cerebrum and cere-
bellum. It also sends a large process, named the velum interpositumj forms velum
into the interior of the cerebrum, and from this vascular processes ^g^tiim
known as the choroid plexuses proiect into some of the ventricles of the and choroid
brain. Two smiilar hinges, the choroid plexuses of the fourth ventricle^
similarly project into that cavity between the cerebellum and medulla
oblongata.

The pia mater consists of a network of vessels, formed by the structure,
ramifications of the arteries and veins entering into, or issuing from
the nervous substance, the intervals between the vessels being closed
by connective tissue so as to form a continuous membrane. From
its deep aspect minute and very numerous vessels pass into the brain
perpendicularly to the surface ; and these can readily be seen as fine How to
hair-like processes projecting from the membrane when a portion of vessels^
it is stripped from the brain substance under water or when a piece
of the freshly removed membrane is floated out in a dish.

Vessels and nerves. The arachnoid has no vessels, but various Vessels and
anatomists have described minute branches of some of the cranial membranes,
nerves in the membrane. The sources of the vessels of the pia
mater are given below, and its nerves, which are probably destined
for the vessels, come from several cranial nerves and the sympathetic.

Dissection. First follow out the arteries at the base (fig. 257, Dissection
p. 719), let the brain be upside down, and remove the arachnoid °
membrane. Having displayed the trunks of the vertebral arteries {^^)

718

DISSECTION OF THE BRAIN.

of large
brain.

and of small
brain.

on the medulla oblongata, and those of the carotid near the median
fissure of the large brain, the student should lay bare on one side the
branches to the large brain. Define first the two arteries {anterior cere-
bral) lying in the median fissure (^) and joined by a short branch (3)
(anterior communicating) ; next, an artery that passes outwards ("') in
the fissure of Sylvius [middle cerebral), and pursue it to the outer sur-
face of the hemisphere. Look then for a much smaller vessel {anterior
choroid) which sinks into the brain on the outer side of the crus
cerebri ('). Then by gently raising the cerebellum on the same side,
the last artery of the cerebrum {posterior cerebral, '') may be traced back
round the crus cerebri to the inner part of the hemisphere.

Two principal arteries pass to the cerebellum. One on the upper
surface {superior cerebellar) may be brought into view just behind the
bifurcation of the basilar artery (^) and se]->arated from the posterior
cerebral by the third nerve. The fourth nerve runs beside it, and
the cerebellum should be raised in tracing the vessel. Two other
arteries {anterior and posterior inferior cerebellar) turn backwards
and outwards from the vertebral, and may be easily followed.

The branches of the anterior, middle and posterior cerebral arteries
will be followed out as they are described by removing the adhering
membranes, by gently opening the fissures and sulci in which they
j)artially lie, and by drawing them and their branches away from the
brain substance as the work proceeds, and if care is taken no material
injury will be done.

Arteries of the Brain (fig. 257). The brain is supplied with
blood by the vertebral and internal carotid arteries.

The VERTEBRAL ARTERY {^^) is a branch of the subclavian trunk
and enters the skull through the foramen magnum ; directed
upwards and forwards round the medulla oblongata, it blends with
its fellow in a common trunk (basilar) at the lower border of the
winds round pons. As the vessel winds round the medulla oblongata, it lies
oblongata: l>etween the roots of the first cervical and hypoglossal nerv^es ; but it
is afterwards internal to the latter.

Branches. Between its entrance into the spinal canal and its
termination in the basilar, each artery furnishes offsets to the dura
mater, to the spinal cord, and to the cerebellum.

a. The posterior meningeal branch leaves the trunk opposite the
foramen magnum, and ramifies in the dura mater lining the cere-
bellar fossa of the occipital bone.

h. The posterior spinal branch is of inconsideral)le size, and arises
opposite the back of the medulla oblongata : it descends along the
side of the cord, behind the nerves, and anastomoses with its fellow
and with branches that enter by the intervertebral foramina.

c. The anterior spinal branch (^•^) is small like the preceding, and

springs from the trunk opposite the front of the medulla. It joins the

corresponding twig of the opposite side, and the resulting vessel is

continued along the middle of the cord on the anterior aspect.

and to under d. The posterior inferior cerebellar artery (^*^) arises from the end of

cerebellum, ^^^ vertebral (sometimes from the basilar), and winds backwards

Arteries of
the brain.

Vertebral

ends in
basilar,

branches

to dura
mater :

> spi:
)rd,

to spinal

posterior
and

anterior;

THE VERTEBRAL AND BASILAR ARTERIES.

719

round the medulla oblongata, between the pneumo-gastric and spinal
accessory nerves, to the median groove of the cerebellum. Directed
onwards in the sulcus between the hemisphere and the inferior
vermiform process, the artery reaches the hinder margin of the
cerebellum, and there anastomoses with the superior cerebellar

arterv.

An offset of this branch ramifies over the under part of the offsets,
cerebellar hemisphere, and ends externally by anastomosing with the
artery of the upper surface. As the vessel passes by the side of

— -7

Fig. 257. — Diagrammatic representation of the Arteries at the
Base of the Brain.

1. Internal carotid trunk.

2. Anterior cerebral.

3. Anterior communicating.

4. jNIiddle cerebral.

5. Anterior choroid.

6. Posterior communicating.

7. Posterior cerebral.

8. Superior cerebellar.

9. Auditory.

10. Posterior inferior cerebellar.

11. Basilar.

12. Vertebral.

13. Anterior spinal.

The anterior inferior cerebellar ai-tery which passes outwards from the
1'a.silav behind No. 8 is not indicated by a pointer.

the fourth ventricle, it gives a small choroid branch to the plexus of
that cavity.

The BASILAR ARTERY (•!), formed by the union of the two verte- Basilar
brals, reaches from the lower to the upper border of the pons, where ^^ ^^ '
it ends by dividing into two branches (posterior cerebral) for the
cerebrum. The vessel lies in the median groove of the pons, resting situation ;
against the body of the sphenoid bone. On each side of, and almost
parallel to it, is the sixth nerve.

Branches. Besides the two posterior cerebral branches, the artery branches ;
supplies transverse offsets to the pons and the fore part of the cere-
bellum, and a large brancli to the upper surface of the cerebellum.

720

DISSECTION OF THE BRAIN.

transverse a. The transverse arteries of the pons are four or five small twigs,
to the pons ; ^j^j^j^ ^re named from their direction, and are distributed to the
substance of the pons. One of them (9) gives an offset (auditory)
to the internal ear along the auditory nerve,

h. Like the branches of this set is the anterior inferior cerebellar
artery : it arises from the basilar trunk, and is distributed to the
fore part of the under surface of the cerebellar hemisphere.

c. The superior cerebellar artery {^) is a considerable vessel derived
from the basilar so near the termination as to be often described as
one of the final branches of that vessel. Its destination is the upper
surface of the cerebellum, to which it is directed backwards, winding
round the crus cerebri below the third, but parallel to the fourth

auditory ;

anterior
cerebellar,

Superior
cerebellar.

Artery of corpus callosum. ^ebro-^

Praecuneal.

ArCe7

Parieto-occipital.

Internal frontal
Central
Anterior cerebral. --
Internal orbital.

Posterior communicating.

Anterior choroid
Posterior cerebral

Posterior choroid.

Calcarine.

Temporal.
Temporal.

Fig. 258. — The Mesial and Under Surfaces op the Cerebral Hemi-
sphere, SHOWING THE DISTRIBUTION OF THE ANTERIOR AND POSTERIOR

Cerebral Arteries.

giving
oflFsets
to velum.

Posterior

cerebral

artery

branches of
which are
cortical,

nerve. The ramifications of the artery spread over the upper surface
of the cerebellum, and anastomose with the vessel of the opposite
side, and with the inferior cerebellar arteries.

Some twigs of this vessel enter the fold of the pia mater (velum
interpositum) which projects into the cerebrum,

d. The POSTERIOR cerebral artery (fig. 257, 7, and fig. 258) takes a
backward course, similar to that of the preceding artery, but separated
from it by the third nerve. It winds round the crus cerebri and is
directed upwards and backwards to beneath the posterior end of the
corpus callosum ; it enters the calcarine fissure and divides into its
two terminal branches, parieto-occipital and calcarine. Near its
origin it is joined by the posterior communicating artery, passing
backwards on each side from the terminal part of the internal carotid.
The artery gives off numerous branches —

1. The deep or central arteries leave the trunk close to its origin,

THE POSTERIOR CEREBRAL ARTERY.

721

i enter the posterior perforated space between the crura cerebri, to

i«ly the optic thalarai in the interior of the brain. They are

.. ided into two sets, those near the middle line and those further

out, and are named respectively the postero-mesial and yostero -lateral

centi^ arteries.

2. The posterim choroid artery (fig. 258) leaves the parent vessel as
it winds round the cms and pursues a parallel course until it turns
forwards beneath the posterior end of the corpus callosuni to enter
the velum interpositum and the choroid plexuses of the ventricles of
the cerebrum.

3. Two or more superficial, or cortical, temporal branches pass
outwards from the artery in its course backwards and supply the
under surface of the temporal lobe, except at the most anterior and
most posterior parts.

4. The calcarine and parieto-occipitalj like the foregoing, are cortical
ai-teries. The calcarine runs into the posterior limb of the calcarine

two sets ;

posterior

choroid

artery.

Cortical
branches :

Temporal.
Calcarine.

Ascending parietal.
Ast-eudiug frontal, ^g^re-hral fWr-ter-

External orbital

Middle cerebral

ARTERY.

Temporal

Parieto- temporal.

Fig. 259. — The Outer Surface of the Cerebral Hemisphere, showing
THE Distribution of the Middle Cerebral Artery.

fissure and supplies the back part of the fifth temporal convolution
and the adjoining cuneus. The parieto-occipital branch runs mainly parieto-
in the internal parieto-occipital fissure and supplies the front part of occipital,
the cuneus and the back part of the pre-cuneate convolution.

The posterior cerebral artery thus supplies the cortex of the
cerebral hemisphere over the whole of the mesial aspect of the
temporal (except the most anterior part) and occipital lobes, with a
small part of the parietal (pre-cuneus) ; as well as a small part of the
corresponding parts on their outer or convex surface (fig. 259).

From the foregoing examination of the offsets of the vertebral Part of
arteries and the basilar trunk, it appears that about half the brain — Jf^ ^'
viz., the medulla oblongata, the pons, the cerebellum, and the vertebral

^ ' r ^ ' arteries.

D.A. 3 A

722 DISSECTION OF THE BRAIN.

posterior third of the cerebrum, as described — receives its blood

through these branches of the subclavian arteries.

Internal The INTERNAL CAROTID ARTERY (fig. 257, ^) terminates in branches

^^° ^ for the remaining part of the cerebrum. The vessel emerges from

the cavernous sinus internal to the anterior clinoid process, and

ends in divides at the inner end of the fissure of Sylvius into cerebral and

C6r6br3.1

arteries : communicating arteries.

branches. BRANCHES. In the skull the carotid gives oft" the ophthalmic

offset, before it ends in the following branches (fig. 257) : —

a. Posterior communicating.

b. Anterior cerebral.

c. Middle cerebral.

d. Anterior choroid.

Posterior a. The posterior communicating artery {^) is generally a small

eating. " vessel, directed backwards on the inner side of the third nerve,

to join the posterior cerebral artery near the pons.

Anterior h. The ANTERIOR CEREBRAL ARTERY (fig. 257,^, and fig. 258) Supplies

artery : the inner part of the cerebral hemisphere. It is directed forwards to

the median fissure between the halves of the large brain ; and as it

its com- is about to enter the fissure, it is united to its fellow by a short thick

branch — the anterior communicating (fig. 257, ^). Then passing into

the fissure, it bends- round the fore part of the corpus callosum,

and is continued backwards along the upper surface of that body,

sending its branches nearly to the posterior extremity of the

hemisphere.

Its branches, like those of the posterior cerebral, consist of deep or
central and superficial or cortical arteries,
central, The central branches iantero-mesiaX) consist of two or three small

offsets which arise near the beginning of the artery, and penetrate
the anterior perforated space at the inner end of the fissure of Sylvius
to reach the fore part of the corpus striatum in the interior of the
hemisphere,
and cortical The cortical branches supply the fore and upper parts of the
o sets. internal surface of the hemisphere, extending backwards as far as
the parieto-occipital fissure ; and some turn round the margin to
the adjacent portions of the frontal lobe on both the upper and
lower aspects.

They are named as follows :— (fig. 258).

1. Internal orbital.

2. Internal frontal.

3. Prsecuneal.

4. The artery of the corpus callosum.

Internal 1. The internal orbital is distributed to the inner part of the under,

orbital. ^j. orbital surface of the frontal lobe.

Internal 2. The internal frontal are two or three branches given off

frontal. ixom the convexity of the vessel as it winds round the anterior end
of the corpus callosum, and are distributed to the whole of the
mesial surface of the frontal lobe and to a small part of its outer or
convex surface (fig. 259).

I THE MIDDLE CEREBRAL ARTERY. 723

3. The prcBcwieal is a considerable vessel lying more or less in Pi-*cuueaL
tlie calloso-marginal sulcus and distributed to the para-central

and praecuneate convolutions as well as to the upper part of the
callosal.

4. The artery of the carpus callosum is a small vessel directed Artery of
backwards in the callosal sulcus, and distributed to the corpus caUosum,
callosum and the lower part of the callosal convolutions.

C. The MIDDLE CEREBRAL ARTERY (fig. 257,4, and fig. 259) is the ^j.^J^®i
largest branch of the carotid, and ramifies over the outer surface of the artery :
hemisphere. Entering the fissure of Sylvius, it di\ddes into four or
five large cortical branches, which issue therefrom and supply the cortical
whole of the parietal lobe, together with the neighbouring parts of
the frontal and temporal lobes.

As the vessel enters the fissure of Sylvius it gives oft" the antero- and central
lateral set of central arteries, which are the largest of their kind and
pass upwards through the anterior perforated area to the central Autero-
nuclei, supplying chiefly the lenticular and caudate nuclei of the set.
corpus striatum and the intervening white matter of the internal
capsule.

The origin of the cortical branches will be seen by opening out Cortical
the fissure of Sylvius, as in fig. 259, and they are named as are^*^ ^
follows : —

1. External orbital.

2. Inferior external frontal.

3. Ascending frontal.

4. Ascending paiietal.

5. Parieto-temporal.

6. Temporal.

1. The external orbital is distributed to the outer part of the under, external
or orbital, surface of the frontal lobe. °^ * '

2. The inferior external frontal are two or three small branches inferior
which pass to the lower part of the outer surface of the frontal fjjjjaf^
lobe.

3. The ascending-frontal is a considerable vessel lying more or less ascending
in the pre -central sulcus and distributed to the adjoining parts of ^^^ '
the cortex.

4. The ascending-parietal branch, like the foregoing, passes ascending
upwards ; it is partially received into the post central sulcus, and is ^*"^ '
distributed to the cortex in its neighbourhood.

5. The parieto-temporal are, usually, two large terminal vessels from parieto-
the middle cerebral which emerge from the back part of the Sylvian and^*^''
fissure to pass to the outer surface of the back part of the parietal,

the front of the occipital, and the contiguous portions of the temporal
convolutions.

6. The temporal branches are two or three in number : they temporal,
emerge from the lower part of the Sylvian to the anterior part of

the temporal lobe, and to the whole of its outer surface as far back
as the preceding vessels.

On comparing figs. 258 and 259, it wdll thus be seen that the

3A2

724

DISSECTION OF THE BBAIN.

clioroid

arteiy.

Circle of
Willis :

vessels that'
form it.

Use of the
free in- *
osculation.

Other

anastomoses
are small.
Veins of the
brain.

Two sets to
cerebriun :

external,
which are
upper and
lower :

and internal.

Veins of
cerebellum.

Di.ssection.

'Care to be
taken in
removing
pia mater.

cortical distribution of the anterior cerebral brancli of the internal
carotid is mainly on the mesial, whilst that of the middle cerebral is
on the outer surface of the cerebral hemisphere.

The anterior choroid artery (fig. 257,^ and fig. 258), is small, and
arises either from the trunk of the carotid, or from the middle cerebral
artery : it passes backwards on the outer side of the posterior com-
municating artery, and makes its way between the hemisphere and
the cms cerebri into the dentate fissure, at the bottom of which it
enters the choroid plexus of the lateral ventricle.

Circle of Willis (fig. 257). The arteries at the under part of
the brain are united freely both on their own side and across the
middle line in an anastomotic ring — tlie circle of Willis. On each
side this ring is formed by the trunk of the internal carotid giving
forwards the anterior cerebral, and backwards the posterior com-
municating artery. In front it is constructed by the converging
anterior cerebrals, and the anterior communicating artery. And
behind is the bifurcation of the basilar trunk into the posterior
cerebrals which receive the ^Josterior communicating. In the area of
the circle lie several parts of the brain corresponding with the floor
of the third ventricle.

The complete inosculation between the cranial vessels in the circle
of Willis possibly allows at all times a free circulation of blood
through the brain, even though a large vessel on one side of the neck
should be obstructed.

Beyond the circle of Willis the arteries of the cerebrum communi-
cate together only by fine anastomoses.

The VEINS of the brain enter the sinuses of the dura mater, and
do not form companion trunks to the arteries.

Two sets of veins belong to the cerebrum, viz., superficial or
external, and deep or internal.

The superficial veins of the upper part of the hemisphere ascend
to the superior longitudinal sinus ; and those of the lateral and
under parts enter the sinuses in the base of the skull, especially
the cavernous and lateral sinuses. These vessels communicate freely
together.

The deep veins of the cerebrum join the veins of Galen (p. 764),
and reach the straight sinus.

The veins of the cerebellum end differently above and below. On
the upper surface they are received by the veins of (jralen and the
straight sinus ; and on the lower surface they terminate in the occi-
pital and lateral sinuses.

Dissection. The pia mater and the vessels are now to be stripped
from the brain, and the origin of the cranial nerves is to be care-
fully defined. Over the cerebrum and pons, the pia mater can be
detached with tolerable ease by using two pairs of forceps ; but on
the cerebellum and the medulla oblongata the membrane adheres so
closely as to require much care in removing it without tearing the
brain- substance, or injuring the nerves.

In clearing out the groove between the halves of the cerebellum

THE BASE OF THE BRAIN. 735

on the under surface, the membrane bounding the opening into the
fourth ventricle will be taken away : therefore the position, size, and
limits of that opening between the back of the medulla oblongata
and the cerebellum should be noAv noted (p. 781).

When the surface has been cleaned, the brain is to be replaced in Replace in
the formalin liquid, but it is to be turned over occasionally, so that
all the parts may be hardened. A little additional formalin may
be added from time to time to maintain the strength of the solution.
The remaining Sections on the brain will be taken after the dissection
of the head and neck is completed.

Section II.

GENERAL SURVEY OF THE BASE AND THE ORIGIN OF
THE CRANIAL NERVES.

Directions. Now that the student enters upon the systematic Transfer
dissection of the brain he is recommended to transfer the hardened gl^'J^
preparation from the formalin solution to methylated spirit in order
to avoid the inconvenience that arises from a close examination ol
specimens recently taken from the former liquid.

For convenience sake a general survey of the base of the The base of
BRAIN will be made first so that the student may be familiar with the ^^^ ^^"^*
names of the parts, although the structures mentioned will be
examined again later.

Beginning behind on the lower, or anterior, surface of the medulla
oblongata (fig. 261, p. 732) is the anterior median fissure in the middle
line ; on either side of this are tw^o elongated eminences, the anterior
pyi'amids (1) ; external to the pyramid below the pons Varolii is the Parts of the
oval olivary body (5) ; external to this is a narrow band, which, if J^j^s""* ^"'^
traced downwards, appears to become continuous with the lateral
tract (2) of the spinal cord, and beyond this, passing upwards into the
cerebellum, is a large mass at the postero-external part of the medulla
known as the restiform body (3). Emerging from the groove between
the anterior pyramid and the olive are the roots of the twelfth nerve
and in front of the restifonn body a large number of nerve roo+s
appear which belong to the ninth, tenth, and eleventh nerves. In
front of the medulla the large mass of the pons (fig. 268 d, p. 741)
passes across, and lying in the outer and back part of this is a con-
voluted piece of the cerebellum, the flocculus (c). Immediately in Enumera-
front of the pons are two large white masses, the peduncles of tlie central
cerebrum or crura cerebri (/), one belonging to each hemisphere ; and parts,
between them is a small area perforated by vessels, which is named
the posterior perforated space (g). Crossing the peduncle is the optic
tract; and between it and the inner part of the hemisphere is a
fissure leading? into the lateral ventricle.

In front of the posterior perforated space are seen two rounded

726

PTSSECTION OF THE BRAIN.

Parts in
front of the
crura
cerebri.

Olfactory
lobe.

Definition.

Origin is
apparent
and real.

Real is from
grey matter.

Classifica-
tion as
twelve pairs.

Scemmer-
ing's.

Designation

from

number,

name of
part,

or function.

Olfactory
nen-es.

white bodies — the corpora albicantia (e) ; and then a prominent
greyish mass, called tuher cinereum [h). From the tuber cinereum a
conical process, the infundihulum, descends to the pituitary body in
the sella Turcica of the sphenoid bone.

Anterior to the tuber cinereum are the converging optic tracts
with their commissure (i). In front of the commissure lies a thin
greyish layer — lamina cinerea (m) : and still farther forwards is the
great longitudinal fissure between the hemispheres, with the white
corpus callosuni (n) in the bottom of it.

At the inner end of the Sylvian fissure is a depression termed
the vallecula Sylvii (l), at the bottom of which is seen another spot
perforated by vessels — the anterior perforated space.

Lastly, in front of the anterior perforated space, and resting on
the surface of the frontal lobe of the cerebral hemisphere, is the
elongated process of the brain (o) named the olfactory lobe, from which
the olfactory nerve-filaments spring. This process is frequently
called the olfactory nerve, but its true nature as a lobe of the
cerebrum is shown by its position and structure, as well as by its
condition in the lower animals, in which it is generally of large size.

The CRANIAL NERVES take origin from the encephalon, with one
exception, the sj^inal accessory, and pass through apertures in the wall
of the cranium.

The origin of a nerve is not determined by the place at which it
appears on the surface, for fibres or roots may be traced deeply into
the brain-substance. Each nerve has therefore a superficial or appa-
rent, and a deep or real origin.

With respect to the superficial attachment there cannot bo any
doubt ; but the deep origins, in consequence of the difficulty of tracing
the roots, are matters for the most part outside the possibilities of
ordinary dissection. When the roots are followed into the encephalon,
they enter masses of grey substance, containing nerve-cells, which
are looked upon as nuclei of origin in the case of motor nerve fibres
or of termination in the case of sensory, or afferent, fibres.

The cranial nerves are enumerated as forming twelve pairs.
According to this arrangement (Soemmering's) each trunk is con-
sidered a separate nerve, although it may be associated with others in
the foramen of exit.

The several nerves may be designated first, second, third, and so
forth : this numerical mode of naming applies to all.

But a second name has been derived for some of the nerves from
the parts to which they are supplied ; as instances of this nomen-
clature the terms pneumo-gastric. and hypoglossal may be taken.
A different appellation is given to others, in consequence of the
function conferred on the part to which they are distributed, as the
terms auditory, oculomotor and olfactory express. In this way two
names may be employed in referring to a nerve : — one being
numerical, the other local or functional, as is exemplified below.

The FIRST or olfactory nerves are about twenty fine filaments
which spring from the under surface of the olfactory bulb (fig. 260, ^)

OETGIN OF THE CRANIAL NERVES.

727

They are very soft, and break off close to their origin when the brain
is removed from the skull.

The SECOND or optic (ficr. 260, ^) is the largest of the cranial Second

• ncrvG is

nerves except the fifth, and appears on the crus cerebri as a flat optic :

band (the optic tract), which is directed inwards to join the one of

the opposite side in a commissure. The name aptic nerve is confined part called

to the portion in front of the commissure which is round and firm. ™*^ '

The destination of the nerve is the eyeball.

The optic tract winds round the crus cerebri to end, in front in Optic tract:

Fig. 260. — Base of the Brain, with origin op the Cranial Nerves.

7. Facial and auditory, the former
smaller and internal.

8. Grlosso-pharyngeal, pneumo-
ga-stric, and spinal accessory nerves,
in order from above downwards.

9. Roots of hypoglossal nerve.

1. Olfactory lobe.

2. Optic commissure.

3. Oculomotor.

4. Trochlear.

5. Trigeminal, with small and
large root.

6. Abducent.

the commissure. Behind it divides into two pieces which will be
subsequently seen to take their origin from the optic thalamus, the origin now
corpus geniculatum externum, and the superior corpus quadrigemi- ^°°^^^^*^ '
num. As the tract passes forwards it is attached to the crus cerebri
by its outer or anterior edge ; and internal to the crus it is placed relations,
between the anterior perforated spot on the outer, and the tuber
cinereum on the inner side ; it is said to be joined here by
additional fibres springing from the latter body.

The commissure (chiasma) of the nerves measures nearly half an its commis-

728 DISSECTION OF THE BRAIN.

iucli across, and lies on tlie olivary eminence of the sphenoid bone,

situation, within the circle of Willis. It is placed in front of the tuber cine-

reuni ; and passing beneath it (in this position of the brain) is the

thin lamina cinerea.

arrangement In the commissure each tract is resolved into three sets of fibres

of fibres. ^|^j^ ^^^ following arrangement : — The outer fibres, few in number,

are continued straight to the temporal side of the eyeball of the

same side. The middle, the most numerous, decussate with the

corresponding fibres of the other tract, — those of the right tract

being continued into the inner part of the left nerve and passing to

the nasal portion of the opposite eye, and vice versa. The most internal

fibres are continued across the back of the commissure into the tract

of the other side back to the brain without entering the eye, and

are not visual fibres.

Trunk of The optic lUTve extends from the commissure to the eyeball, and

nerve. -^ g^i^Q,-^^^ Qjjg mc^Yi and a half in length. It leaves the skull by the

optic foramen, where it receives its sheaths from the dura mater and

arachnoid and crosses the orbit to end in the retina.

Origin of the The THIRD or OCULOMOTOR NERVE ('^ is round and firm, and is

nene. .^^.^-j^^jj-jy^]^ \^y g^ series of filaments along an oblique groove on the

inner side of the crus cerebri, near the posterior perforated space,

and close in front of the pons Varolii.

deep in crus Deep origin. The fibres of the nerve traverse the crus in their course
cerebri. from a nuclear origin in the grey substance in the floor of tiie aqueduct of

Sylvius beneath the anterior corpus quadrigeminum. *

Fourth The FOURTH or TROCHLEAR NERVE (*) Cannot be followed back-

"^^^b 11°"^ • ^^'^^^^ ^^ present to its origin. It is the smallest of the cranial
nerves, and emerges on the upper surface of the crus behind the
posterior corpus quadrigeminum through the valve of Vieussens
(fig. 277, ^, p. 765). The nerve appears at the base between the
cerebrum and cerebellum on the side of the crus cerebri, and is
directed forwards to enter an aperture in the free edge of the tentorium
cerebelli near the posterior clinoid process.

nucleus in Deep origin. In the valve of Vieussens the nerve crosses to the opposite
floor of side, decussating with its fellow, and then arches round tlie aqueduct of

amift!fm».t Sylvius to reach its nucleus in the floor of that canal, immediately behind the
nucleus of the third nerve.

aqueduct.

Fifth nerve The FIFTH or TRIGEMINAL {^) is the largest of the cranial nerves,
roots^" and consists of two roots, ganglionic or sensory, and aganglionic or

motor, which are separate to beyond the ganglion,
both issuing The nerve emerges from the side of the pons Varolii, nearer the
from pons. ^^pp^j. ii^q;^^ the lower border. The small or aganglionic root is the
higher, and is separated from the large root by one or two of the
transverse bundles of the pons. Both roots pass outwards through
an aperture in the dura mater, above the petrous part of the
temporal bone into the cavum Meckelii, as already described, p. 516.

* The position of the nuclei of this and the following nerves is roughly
shown on fig. 287, on p. 783.

ORIGIN OF THE CRANIAL NERVES. 720

Deep orlyiii. The large root divides within the pons into two parts. One Deep origin
of these is connected with a mass of grey matter (sensory nucleus of the fifth) 9^ l^^S^ ^^^
near the floor of the fourth ventricle : the other (ascending root of the fifth ; ^^lufa*"
fig. 267 Va, p. 739) arises from the cells of the posterior horn of the grey matter oblongata ;
in the lower part of the medulla oblongata and upper part of the spinal cord,
and is directed upwards on the outer surface of the gelatinous substance of
Rolando to join the upper part.

The snuill root also has a double origin, one part springing from a special of small in
nucleus (motor nucleus of the fifth) in the floor of the fourth ventricle internal ^j^'^y^^j^
to the sensory nucleus, and the other (descending root of the fifth ; fig. 283,
p. 775) from a collection of nerve-cells on the side of the aqueduct of Sylvius.

The SIXTH NERVE {% abducent nerve of the eyeball comes through Sixth nerve
the outer part of the anterior pyramid close behind the pons, and p^mid,
often by a second band from the lower border of the pons.

Deep origin. The fibres of the nerve pass forwards, through the lower and nucleus
part of the pons, from a nuclens in the floor of the fourth ventricle, beneath j?^'^^^
the outer part of the fasciculus teres (fig. 267). ventricle.

The SEVENTH or facial nerve (7) appears at the lower border of seventh
the puns, to which it is closely adherent, in the depression between faterai^ct
the upper ends of the olivary and restiform bodies. A small accessory ?^.^"|^*
bundle {portio inteiTnedia of Wrisberg) leaves the medulla oblongata intermediate
L'etween the facial and the auditory nerves, and joins the former Portion,
within the internal auditory meatus.

Deep origin. The fibres of the facial nerve pass backwards to the floor of Deep origin
the fourth ventricle, and there wind round the nucleus of the sixth nerve, to fro^i a
arise from a group of nerve-cells lying in front and to the outer side of the do^al'part
latter (fig. 267). Whether some of the fibres are connected with the cells of of iions.
the nucleus of the sixth is uncertain.

The EIGHTH or auditory nerve has a suiface attachment outside Eighth
the foregoing to the restiform body internal to the flocculus ; one of rStifo^
its roots passing round the restiform body to its dorsal surface. ^^o<iy-

Deep origin. At its attachment to the medulla oblongata, the auditory Deep origin,
nerve consists of two roots, upper and lower. The fibres of the upper or
dorsal part constitute the cochlear division of the nerve, some of its fibres Cochlear
terminate in cells forming the ventral cochlear nucleus on the under part of division,
the restiform body, and others pass to the dorsal cochlear nucleus (outer
auditory nucleus) in the lateral angle of the floor of the fourth ventricle
dorsal to the restiform body. The fibres of the striae acusticae arise from the
latter nucleus, and they, with many more from the ventral nucleus, eventually
pass, through the intervention of the superior olivary nucleus and other groups
of cells, into the lateral fillet and are connected with the posterior corpus
quadrigeminum.

Tlie lower, or ventral part of the auditory nerve constitutes the vestibular Vestibular
ision. Many of its fibi-es pass through the pons, internal to the restiform division,
body to the inner auditory nucleus, or the dorsal vestibular nucleus, beneath
the auditory tubercle in the floor of the fourth ventricle : other fibres pass to
groups of large cells internal to and beneath the restiform body forming the
nucleus of Deiters, and some to a group of cells styled the nucleus of the
descending root. Many fibres from the dorsal nucleus of the vestibular
division of the auditory nerve pass through the restiform body into the
cerebellum.

The NINTH or glosso-pharyngeal nerve (^) leaves the medulla Ninth nerve

below facial

730

DISSECTION OF THE BRAIN.

nucleus in
floor of
fourth
ventricle.

Tenth nerve
below ninth

nucleus
beneath
fourth
ventricle.

Eleventh
nerve in two
pieces ;

accessory
from
medulla
oblongata.

spinal from
cord.

oblongata by five or six filaments close below the facial nerve, in the
groove between the olivary and restiform bodies.

Deep origin. Directed backwards through the medulla oblongata, the fibres
join a main nucleus beneath the inferior fovea in the floor of the fourth
ventricle. A considerable bundle of fibres passes to the fasciculus solitarius
in the medulla and upper part of the cord, and some motor fibres spring,
with others of the vagus, from the mtcleiis amhiguus in the medulla.

The TENTH, VAC4UR Or PNEUMO-GASTRIC NERVE (^) IsSUes by 'A

number of filaments (twelve to fifteen) from the medulla oblongata
in a line with, and below the glosso-pharyngeal.

Deep origin. Taking a similar course in the medulla oblongata to the roots j
of the ninth nerve, the fibres of the vagus reach their main nucleus beneath the
calamus scriptorius of the fourth ventricle. Other fibres pass to the fasci- j
cuius solitarius, and others spring from the small nucleus amhiguus in th«
medulla.

The ELEVENTH Or SPINAL ACCESSORY NERVE COnsistS of twO pai

— accessory to the vagus, and spinal.

The accessory or bulbar part is of small size, and is formed by thj
union of slender filaments continuing the line of the glosso-pharyi
geal and vagus nerves along the medulla oblongata, as low as tl
first cervical nerve. After communicating with the spinal part il
the jugular foramen, it passes into the vagus nerve outside the skull

The spinal part is firm and round, like the third or the sixth
nerve, but only a small piece of it can now be seen. It arises by a
number of fine filaments from the lateral column of the spinal cord
as low as the sixth cervical nerve. As the nerve ascends along the
side of the cord it lies between the ligamentum denticulatum and
the posterior roots of the spinal nerves, with the upper of which it
may be connected. It enters the skull by the foramen magnum.

Both from Beep origin. The fibres of both accessory and spinal parts have been

one nucleus, traced inwards to an elongated column of cells reaching from the lower third
of the olivary body to the level of the fifth cervical nerve, and situate, in the
spinal part of its extent, in the outer part of the anterior horn of the grey
matter, and, in the medulla oblongata, behind and to the outer side of the
hypoglossal nucleus.

The ninth, tenth, and eleventh nerves converge below the crus
cerebelli, and rest on the flocculus. From that spot they are directed
outwards to tlie jugular foramen.

The twelfth or hypoglossal nerve (^) appears on the front
of the medulla oblongata, where it is attached by a series of
filaments (ten to fifteen) along the groove between the pyramid
and the olivary body, in a line with the anterior roots of the spinal
nerves. The filaments of origin unite into two bundles, which pierce
the dura mater separately, and unite at the outer part of the anterior
condylar foramen.

Deep origin. The roots of the nerve can be followed through the medulla
oblongata to a nucleus, which is placed in front of the central canal below,
and extends upwards into the lower part of the fasciculus teres in the fourth
ventricle.

Twelfth
nerve from
front of
medulla
oblongata :

nucleus near
central canal
and fourth
ventricle.

THE MEDULLA OBLONGATA. 731

Section III.

MEDULLA OBLONGATA AND PONS VAROLIL

The medulla oblongata and the pons are interposed between the

nal cord and the brain proper.

Dissection. On a single brain the student may learn nearly all Dissection,
iiii' anatomy of the medulla and pons ; but if he has a second brain
' ' should cut through the crus cerebri above the cerebellum imme-

tely behind the posterior corpus quadrigeminum and then carefully

ce away the cerebellum from the pons and medulla by cutting

i ough the attachments close to the cerebellum, opening out thereby
^ng. 262, p, 733), the fourth ventricle and exposing the upper surfaces
of the pons and medulla.

Position. The brain is to remain in the same position as for the Position,
examination of the vessels and nerves.

The MEDULLA OBLONGATA or BULB is the expanded upper end of Medulla
the spinal cord which is contained in the cranium. Its limits are extent* '
the lower border of the pons in one direction, and the lower margin
of the foramen magnum in the other. It is somewhat conical in
form, and measures nearly an inch in length, half an inch in form and
breadth below, and about an inch at its widest part above.

Its base joins the pons, the transverse fibres of the latter marking Base.
its limit ; and its apex is blended with the spinal cord. The Apex,
anterior surface (fig. 261) is irregularly convex, and is in contact with Surfaces,
the hollowed basilar process of the occipital bone. The opposite
surface (fig. 262) is convex below, and somewhat excavated above,
where it forms the floor of the fourth ventricle ; it rests in the
groove between the hemispheres of the cerebellum, and on this
posterior or upper aspect there are not any cross fibres of the pons, as
in front, to mark the limit of the bulb.

The medulla ol)longata is divided into halves by a median fissure Median
in front and behind, in a line with those of the cord. The anterior anterior
median fissure is interrupted at the lower end of the bulb by some
bundles of filires which cross obliquely from one side to the other,
and constitute the decussation of the injramids ; above, it ends at
the lower border of the pons in a dilatation (foramen caecum). The
jyosterior median fissure is continued upwards from the cord through and
the lower half of the medulla oblongata, and then terminates by the ^^ ^"*^'"*
separation of its lateral boundaries to form the sides of the fourth
ventricle.

On each half of the medulla oblongata are elongated eminences, Surface con-
separated by slight grooves, and continuous with the columns of the partly con-
spinal cord; but they receive difterent names in this part of their ^jjj^*^^ ^^°[".
extent, and some fresh bodies are added. Thus, the part continuing new.'
the anterior column of the cord, by the side of the anterior median
fissure, is known as the anterior pyramid (fig. 261, ^). The pro-
longation of the lateral column takes the name of lateral tract (=^), the

732

DISSECTION OF TFTE BRATN.

Pyramid.

Lateral
tract.

Olive.

Funiculus
and tubercle
of Rolando.

position of wliich is occupied in the upper half of the bulb by ai
oval eminence called the olivary body. Continuing the posterioi
column is the funiculus cuneatus (fig. 262, /c), which is separateol
from the lateral tract by a smaller eminence to which the name o4
funiculus of Rolando (R) has been given : in the upper part of th(
medulla these are succeeded by, or become lost on, the restiform hodi
(fig. 261, 2 ; fig. 262, rb) projecting outwards towards the cerebellunu
And lastly, between the funiculus cuneatus and the posterior median
fissure is the funiculus gracilis (fig. 262, fg) continued from tht
posterior median column of the cord.

The anterior i^yramid is placed between the anterior median fissure

on the inner side and the lateral
tract with the olivary body on th^^
outer side. It increases in size from \
below upwards, whence its name
l)Ut at the upper end it is somewhat
constricted and rounded just befor<
it disappears beneath the superficial
transverse fibres of the pons. This
body is only in small part pro-
longed from the anterior colunm of
the cord, its inner and lai-ger por-
tion being formed by the decussating
fibres seen in the anterior median
fissure.

The lateral tract in the lower half
of the medulla oblongata is of the
same width as the lateral column
of tlie cord ; but above, it is reduced
to a narrow strij) along the bottom
of the groove between the olivary
and restiform bodies.

The olivary body is oval in shape
and about half an inch long. Its
upper end, which is more jjrominent
than the lower, does not quite reach
the pons. Internally it is separated
from the anterior pyramid by a narrow groove along which the
hypoglossal nerve arises ; and externally from the restiform body
by a broader one, where the glosso-plmryngeal and vagus nerves
issue.

The funiculus of Rolando begins in a pointed extremity at the
lower end of the medulla oblongata, and enlarging upwards forms,
on a level with the lower end of the olivary body, a slight prominence
known as the tubercle of Rolando. Towards the front this funiculus
is separated from the lateral tract by the continuation upwards of
the lateral groove of the cord ; but posteriorly the line of separation
from the cuneate funiculus is often indistinct. The funiculus and
tubercle of Rolando are better marked in the child, and the tubercle

Fig.

261.— Medulla Oblongata
AND Pons from before.

Pyramid.

Lateral tract.
Restiform body.
Olivary body.
Decussation of pyramids.

THE MEDULLA OBLONGATA.

rS3

lias then a greyisli colour, whence the name tuherculum cinereum is

Kilso given to it.

The funiculus cuneatm is the prolongation of the posterior column
^of the cord, and forms a %WQ\\\ng— tuherculum cuneatum (fig. 262, cf),

}«osite tlie lower extremity of the fourth ventricle.
The restiform body is the largest of the prominences of the medulla
i I'longata, and appears to be the continuation of the funiculus of
Jiiilando and the funiculus
cuneatus. It inclines outwards
above, and entei-s the hemi-
sphere of the cerebellum, of
wliich it constitutes the inferior
peduncle. On the back of the
medulla oblongata, the inner
margin of this body forms the
later.d boundary of the lower
part of the fourth ventricle.

The funiculus gracilis (pos-
terior pyramid) lies b}*^ the side
of the posterior median fissure,
and is the smallest of the parts
of the medulla oblongata. It
L'uds above in an enlargement
termed the clava (fig. 2b2, cl),
which bounds the lower point
of the fourth ventricle.

On the anterior surface of the
medulla oblongata there may be
seen, more or less distinctly in
different subjects, a set of fibres
crossing transversely to the res-
tiform body over the upper half
of the pyramid and the olivary
body. These are the superficial
arciform fibres.

Structure. The fibres of
the several columns of the
spinal cord enter the niedulla
oblongata below, where they

Cuneate
funiculus
and
tubercle.

Restiform
bodv.

Fig. 262. — Medulla Oblongata and
Pons from behind.

fg. Funiculus gracilis.

cl. Clava.

fc. Funiculus cuneatus.

ct. Cuneate tubercle.

H. Funiculus of Rolando.

rb. Restiform body.

a St. Auditory strife.

ft. Fasciculus teres.

sp. Superior peduncle (cut).

vip. Middle peduncle (cut).

ip. Inferior peduncle (cut).

Internal
structure of
medulla
oblongata.

undergo a partial re- arrange-
ment and are partly continued onwards to the cerebrum and
cerebellum, being joined by other fibres which take theii- origin in
the bulb, and they partly end in the grey substance of the medulla
oblongata. The course of the fibres can only be shown to a very
small extent by dissection, and for the complete study of the
arrangement of the fibres, as well as of the grey matter, it is necessary
to examine sections of different parts of the medulla oblongata.

Dissection. In tracing out groups of fibres in the hardened brain
the student will use the knife very little, but he will find that by

Dissection
to trace
pyramid.

734

How to
expose tlie
Ijyramidal
tibres.

DISSECTION OF THE BKAIN.

taking hold of a bundle of fibres in the forceps or fingers and gently
tearing them, up that they will separate in their proper direction.
To expose the connection of the pyramid with the spinal cord
he should take hold of with the forceps and turn outwards on
the left side, as in fig. 2t53, the small part of the anterior column
of the cord at the lowest part of the specimen (which will be below
the decussation), and the pyramid of the right side will then be seen
to divide below into two parts, one passing directly into the anterior
column, and the other crossing the median fissure and disappearing
in the opposite half of the cord. Similarly

Fig. 263. — Superficial Disskciion of the Medulla Oblongata and Pons.

a. Anterior pyramid.

b. Decussation of the pyramids.

c. Pyramidal fibres in the pons.

d. The same in the cms cerebri.

e. Superficial fibres of the pons,
cut through and reflected.

/. Superficial fibres of the pons, in
place.

of an inch deep will be made in the middle line of the pons and its
superficial fibres stripped transversely and the pyramidal fibres
carefully cleaned upwards on the right side, when they will be found
to pass into the lowest part (crusta) of the crus cerebri.
Fibres of Pyramid and anterior column. The fibres of the pyramid form a

the pyramid well-defined and independent bundle (seen in section on fig. 265 rt,
p. 736) through the whole extent of the medulla oblongata, and are
continued below partly into the anterior column of the same side
of the cord and partly into the lateral column of the opposite half.
The set of fibres keeping to the same side forms the outer portion of
the pyramid, but in the anterior column of the cord, where it is
known as the direct pyramidal tract, it is placed close to the anterior

direct,

FIBRES OF THE MEDULLA OBLONGATA.

735

yledian fissure. The decussating fibres are the more numerous, and
u ass obliquely backwards, across the median fissure and behind the and ci-ossed.
ill pposite anterior column, to enter the lateral column of the cord, where
liey constitute the crossed pyramidal tract. Upwards, the fibres of the
yrainid are prolonged through the pons to the crusta of the cerebral
eduncle (fig, 263, c, d). The fibres of the anterior column of the Rest of
ord which are not continued into the pyramid incline backwards, coiunm!

Fig. 264. — Deep Dissection of thk Medulla Oblongata, Pons, and
Grus Cerebri.

I. Pyramidal fibres, cut through,
and raised as far as the optic
thalamus.

b. Lateral tract.

c. Olivary body.

d. Deep longitudinal fibres in the
pons, derived from the anterior and

lateral columns of the cord.

e. Superficial, and /, deep trans-
verse fibres of the pons, cut through,
and partly removed.

g. Substantia nigra in the crus
cerebri, between the crusta and
tegmentum.

and enter the reticular formation (fig. 265, k, I) in the deeper parts of
the medulla oblongata.

The decussation of the jjyramids (fig. 263, b) occupies the anterior Decus.satiou
fissure of the medulla oblongata at a distance of three-quarters of an ^^ P^*^""*^^
inch below the pons. It is about a quarter of an inch in length, and
is generally constructed by the crossing of three or four bundles of
fibres from each side, but the proportion of the pyramidal fibres varies in
which decussate in the medulla varies much in diflerent individuals.

Dissection. For the purpose of seeing the deeper fibres of the Dissection,
medulla oblongata, the pyramid may be cut across on the right side
just below the olivary body (fig. 264) and raised towards the pons.

7B6

DISSECTION OF THE BRAIN.

Fibres of
lateral tmct.

Direct

cerebellar

tract.

Formation
of restiform
body.

Arciform
fibres :

supei-flcial,

The lateral tract is composed of the remainincr fibres of the lateral
column of the cord, after the crossed pyramidal tract has been given
off. Most of these pass deeply behind the olivary body, and through
the reticular formation to the pons ; but one small band, the direct
cerebellar tract, is continued superficially from the lateral column t
the cerebellum. This band is often visible on the surface of tli
medulla, as a whiter streak lying along the outer edge of the lateral

tract, and inclining backwards
above the tubercle of Kolando i
to join the restiform body.

Posterior funiculi. The
white fibres of the cuneate
and slender funiculi are the
continuation of the postero-
external and postero-median
columns of the cord respec-
tively, and are believed to end
entirely in the grey nuclei of
the funiculi. The funiculus of
Rolando has only a very t&in
superficial white layer, which
is also derived from the pos-
terior column.

The restiform body is formed
by the arciform fibres of the
medulla, by the direct cere-
bellar tract, by fibres from the
gracile and cuneate nuclei and
from the vestibular portion of
the auditory nerve.

Dissection. The separated
pons and medulla will now be
divided longitudinally. One
half we will put aside. On the
other, by making transverse
sections at different levels, the
student will be able to dis-
tinguish the grey matter of
the olivary body and a few
other larger nuclei as well as
the chief bundles of white fibres, but the parts described in small
type require specially stained sections for their proper display.

Arciform fibres. In the upper half of the medulla oblongata,
covering its anterior surface and traversing its substance, is an
extensive system of fibres, curving outwards and backwards from
the median plane to the restiform body, to which this name has
been given.

The superficial arciform fibres (fig. 265, s) have already been
noticed in the description of the exterior of the medulla oblongata.

Fig. 265. — Transversk Section of the
Medulla Oblongata at the Lower
Part of the Fourth Ventricle
(Clarke).

a. Pyramid.

h. OHvary body.

c. Tubercle of Rolando.

d. Restiform body.

e. Lateral boundary of fourth ventricle.
/. White core of the olivary body, with

the roots of the hypoglossal nerve to its
inner side.

g. Olivary peduncle.

h. Deep arciform fibres entering the
raphe (a few more are added from a
second drawing).

k.l. Reticular formation.

n. Floor of foui-th ventricle.

0. Hypoglossal nucleus.

p. Glosso-pharyngeal nucleus.

r. Inner auditory nucleus.

s. Superficial arciform fibres.

t. Remains of the gelatinous substance.

STRUCTURE OF MEDULLA OBLONGATA. 737

The deep arciform fibres {h) are more numerous, and are seen over the and deep,
whole area of transverse sections except in the pyramid. Some of tliem come
to the surface on the inner side of, and through the olivary body, and join
the superficial set. Others are deep in their whole extent, and pass outwards
into the restiforra body, and to the nuclei of the cuneate and slender funiculi.
Internally, the arciform fibres enter the raphe, through which they are
continued to the opposite half of the bulb.

The raphe (between h and /) occupies the median plane of the medulla Raphe,
oblongata above the decussation of the pjrramids, and consists of fibres running
obliquely, longitudinally, and from before backwards, which are in part con-
tinuous with the superficial and deep arciform fibres, and in part spring from
the nuclei in the floor of the fourth ventricle.

Formatio reticularis. In the dorsal portion of the medulla oblongata, Reticular
behind the pyramid and olivary body {I and k), the longitudinal fibres formation,
derived from the anterior a!id lateral columns of the cord, decussating with
the deep arciform fibres, give rise to a structure that is known as the
redicular fornuition of the bulb. In the part of the reticular formation
behind the olivary body (^') interspersed grey matter containing nerve-cells
is also present.

Olivary body (fig. 265, /}. On removing a thin slice from the Olivary
olivary body, it will be seen to consist of three parts, viz., an ^'
external investment of white substance, a thin grey layer, the
olivary nucleus, and a central white core.

The outer white layer consists mainly of transverse fibres, which
belong to the superficial arciform group.

The olivary nucleus or corpus dentatum is a thin plaited capsule its nucleus,
or bag, having a zigzag outline in section. Towards the surface
and behind it is closed, but on the inner side it is open, forming
a narrow neck, which is turned towards the raph6, and gives
passage to the olivary peduncle.

The central white matter fills the grey capsule, and is formed
by the spreading out of a tract of white fibres called the olivary and
peduncle, which passes inwards through the opening in the nucleus ^^ "°cle.
to the raph6. The fibres of the peduncle partly terminate in the
cells of the corpus dentatum, and are partly continued through the
grey layer to join the arciform fibres.

Grey matter of the meduUa oblongata. The larger part of the grey matter Grey matter
in the bulb is a continuation of that of the cord, but there are in addition ^^ ^^^^
some smaller independent masses.

Prolongation of grey matter of the spinal cord. At the lower end of the prolonged
medulla oblongata the central grey matter resembles that in the spinal cord, ^^^^ cord,
but as it extends upwards it undergoes the following changes : —

The anterior cornu is broken up by the passage through it of the fibres of Changes in
the crossed pyramidal tmct, and the detached extremity of the horn is anterior
continued upwards in the lateral tract for some distance as the lateral nucleus. "*^™'

The posterior cornu is pushed outwards by the increasing development of in posterior
the gracile and cuneate funiculi, and its extremity (caput), consisting of the horn,
substantia gelatinosa of Rolando, becomes greatly enlarged aud approaches
the surface, giving rise to the funiculus and tubercle of Rolando (fig, 265, c).
From the Ijase of the horn, processes of the grey matter extend backwards
into the slender and cuneate funiculi, and are known as the nuclei of those
bodies. They are largest in the neighbourhood of the lower end of the fourth
ventricle, where they cause the swellings which have been described above
as the clava and cuneate tubercle (p. 733).

By the opening out of the posterior median fissure and central canal of the and in
cord to form the fourth ventricle, the anterior portion of the grey commissure commissure.

D.A. 3 B

738

Special
masses.

DISSECTION OF THE BRAIN.

and the bases of the anterior horns are exposed, constituting the grey layer in
the floor of that cavit *.

Special deposits of grey jnatter. These are the olivary nucleus, which
has just been examined, some groups of nei-ve-celis at the back of the medulla
oblongata forming nuclei of origin for several cranial nerves, which will be
noticed in connection with the anatomy of the fourth ventricle, and a few
small masses of grey substance of the front of the medulla beneath the
superficial arciform fibres.

Pons Varolii.

Pons: The PONS VAROLII is situate above the the medulla oblongata, and

position, between the hemispheres of the cerebellum. In its natural position

in the skull it lies below the opening in the tentorium cerebelli,

«up. med.velum

dorsal grey layer

reticular
formation

sup.ped. uncle
oj cerebellum

inf. peduncle

^^'//; mid .peduncle

deep transuerse
^ j^ibree

purainiaal ^oii

siiperjirial tT^iuKucrse fibres.

Fig. 266. — Diagram of a Transverse Section through the Lower Part
OF THE Pons, showing its Chief Constituents.

surfaces

borders,
and sides.

It consists
of ventral

and dorsal
portions.

Dissection
to expose
the fibres.

resting against the hinder part of the body of the sphenoid bone. It
is nearly of a square shape, though it is rather wider from side to
side, in which direction it measures about an inch and a half.

The anterior surface is convex and prominent on each side, but
marked along the middle line by a groove in which the basilar artery
lies. By the opposite surface the pons forms the part of the floor of
the fourth ventricle.

The upper border is the longer, and arches over the crura cerebri.
The lower border is nearly straight, and projects above the medulla
oblongata. On each side the pons is continued into the middle
peduncle of the cerebellum, and the fifth nerve issues through it on
each side.

Structure. The ventral or anterior half of the pons consists of
transverse fibres which are in part of their extent divided into two
layers by the prolongation upwards through them of the fibres of the
pyramids of the medulla oblongata. Tlie dorsal or posterior half is
a continuation of the reticular formation, with the grey layer of the
floor of the fourth ventricle, from the medulla oblongata.

Dissection. The superficial transverse ^fibres of the pons have

STRUCTURE OF THE PONS VAROLII.

739

already been divided along tlie line of the pyramid of the right side
(fig 263, p. 734) and turned outwards so as to denude the longitu-
dinal fibres (c) of that body ; and this set of longitudinal fibres, having
been cut across already in the medulla oblongata, may be raised as
far as the upper border of the jJons. Beneath them will appear the
second or deep set of transverse fibres of the pons (fig. 264/, p. 735).
The deep transverse fibres may next be cut through outside the
pyramidal tract (fig. 264), and the reticular formation will then be

Rvmo

267. — Transverse Section of the Lower Part of the Pons
(after Obersteiner).

ra. Raphe.

ipc. Inferior peduncle of cere-
bellum.

stf. Superficial transverse fibres.

pyr.h. Pj'raraidal bundles.

(Itf. Deep transverse fibres.

fi. Fillet.

Son. Superior olivary nucleus.

Va. Ascending root of fifth nerve.

VI. Sixth nerve.
nVI. Its nucleus.

VII. Seventh nerve.
n VII. Its nucleus.

VIII. Upper root of auditory
nerve.

n VIIIo. Outer auditory (dorsal
vestibular) nucleus.

seen, in which deep longitudinal fibres ascend from the medulla
oblongata [d).

The transverse Jihres of the ventral portion of the pons pass into the Transverse
middle peduncle of the cerebellum. They are mostly collected into ventra°
two layers, superficial and deep (fig. 266), which enclose the longi- portion,
tudinal fibres of the pyramid; but some transverse fibres pass
between the bundles of the pyramidal tract. The superficial fibres
are nearly horizontal in the lower part of the pons, but the upper
ones descend to join the cerebellar peduncle, and some are seen
on the surface crossing obliquely over the lower fibres. It wall be
found, however, that the same bundles of transverse fibres cannot be
traced across in the pons from one side of the cerebellum to the

3b 2

740

DISSECTION OF THE BRAIN.

Pyramidal
tract in
pons.

Grey matter
in transverse
fibres.

Formatio
reticularis.

Raph6.

Superior
olive.

Other, but that they break off near the middle line and mostly
assume a longitudinal direction. They are in great part connected
with pontine cells which are associated with fiijres descending in
the crusta of the crus cerebri of the opposite side.

The pijramidal fibres (fig. 266, 267, pyr. h) enter the pons below as
a single mass, but in their passage upwards through the pons they
are broken up by decussating bundles of transverse fibres. Much
increased in number, they emerge at the upper border of the pons,
and are continued into the lower portion (crusta) of the crus cerebri.

Scattered amongst the transverse fibres are numerous small masses
of grey matter (nuclei pontis), with which the cerebellar fibres are
connected, as just explained.

The reticular formation of the pons (fig. 266) is formed of longi-
tudinal fibres continued from the medulla oblongata and passing
upwards to the upper portion (tegmentum) of the crus cerebri and
decussating with various transverse fibres. It contains much in-
terspersed grey matter ; and near the floor of the fourth ventricle
there are several nerve-nuclei, which will be referred to when that
cavity is described.

In the dorsal portion of the ponr?, as in the medulla oblongata,
there is a median raphe (fig. 267, ra), formed mainly by the trans-
verse fibres changing their direction as they cross the middle line.

There is also in the lower part of the pons, close behind the deep
transverse fibres of the ventral portion, and occupying a position
immediately above the olivary body, a small collection of grey
matter to which the name of superior olivary nucleus is given (fig. 267,
Son), and which is connected witli some of the fibres coming from
the cochlear portion of the auditory nerve.

Section IV.

DISSECTION OF THE CEIIEBRUM.

Situation
of the
cerebrum.

The CEREBRUM, or great brain, the largest of the subdivisions of
the encephalon, fills the upper part of the cranial cavity, and
occupies the anterior and middle fossae of the base of the skull. Its
hinder part rests on the tentorium, which sejDarates it from the cere-
Lower limit bellum. Its lower limit would be indicated on the surface of the
head by a line carried along the eyebrow^ to the external angular
process of the frontal bone and then descending to the upper border
of the zygoma and continued backwards to the external occipital
protuberance.

Taking the general form of the cranial cavity, the cerebrum is
convex on the uj^per aspect, and uneven on the lower. It consists
of two hemisjiheres, which are placed side by side, and separated by a
median longitudinal fissure above as far down as the great transverse

Form.

Two hemi'
spheres.

BASE OF THE CEREBRUM.

741

iiimissure — the coi'pus callosum. In tlieir lower half the heini-
-["heres are united by other conimissiire.s, as well as by several united by
(innecting parts at the under surface. The under part of each ^^rts*"
ht inisphere is divided into two by the deep transverse cleft — the
->'/?•(? of Sylvius.
Under Surface, or Base, of the Cerebrum (tig. 268). The Under

' ' \ o J surface of

cerebrum

Under Sukfack of the Brain.

(I. Medulla oblongata.

b. Hemisphere of cei*ebelluni.

c. Flocculus.

d. Pons.

e. Corpus albicans.
/. Crus cerebri.

g. Posterior perforated space.
h. Tuber cinereum.
i. Optic commissure.
I. Vallecula Sylvii and anterior
perforated space.

ni. Lamina cinerea.

n. Rostrum of corpus callosum : on
each side of m, is a narrow white
band — the peduncle of the corpus
callosum.

o. Olfactory bulb.

]). Frontal lobe of the cerebral
hemisphere.

r. Temporal, separated from the
foregoing by the tissure of Sylvius.

under surface of the cerebrum is irregular, in consequence of its
fitting into inequalities in the base of the skull ; and on this aspect
the separation into hemisphere is not so complete as on the upper.
The main objects to be recognised along the median part of the base
of the brain have already been enumerated (pp. 725 and 726).

The peduncle of the cerebrum or crus cerebri (J). This is a Cms
large, white, stalk-like body, which reaches from the upper border

742

DISSECTION OF THE BRAIN.

Dissection
of the crus
cerebri

of the pons to the under part of the cerebral hemisphere of the same
side, near the inner margin. In the natural position, the two
peduncles occupy the opening in the tentorium cerebelli. Each is
about three-quarters of an inch long, and widens as it approaches the
cerebrum. Crossing its lower surface is the optic tract ; and between
the crura of opposite sides is the interpeduncular space, which contains
the posterior perforated space, the corpora albicantia, and the tuber
cinereum with the infundibulum.
Composed of Structure. The peduncle consists of a superficial (lower) layer of
tliree paits. ^jj^fg fibres, the crusta, continued from the longitudinal fibres of the
pons, a prolongation of the reticular formation and of other parts
termed the tegmentum, and an intermediate stratum of grey matter —
the substantia nigra.

Dissection. For the present, the main constituents of the crus
cerebri may be made out ; but various accessory parts will be
referred to later. If the students are working with two brains, the
cut surface of the crura should l^e examined on the preparation in
which the pons and cerebellum have been removed, the fibres of
the crusta should be dissected forwards to their entry to the cerebrum
and sections should be made of the tegmentum as far forwards as
through tlie anterior corpus quadrigeminum. If only one brain is
used the right crus only should be examined. The optic tract
should be divided, and the fibres continuous with the pyramid of
the medulla oblongata should be raised as far as the junction of the
crus with the hemisphere. In this proceeding the substantia nigra
(fig. 264, g) will appear ; and beneath it will be seen the tegmentum.
Finally a block of this crus should be removed beneath the
quadrigeminal bodies, but leaving them behind, taking care not to
transgress the middle line into the left cru.s.

The crusta (fig. 269) is composed of coarse bundles of white fibres,
ascending from the pons to the cerebral hemisphere, where they enter
a layer of wliite fibres termed the internal capsule, which will be
subsequently seen. The continuation of the pyramidal fibres of the
medulla oblongata (pyramidal tract) occupies the central part only
of the crusta ; and the lateral parts consist of fibres which have
already been traced into the pons. Those on the inner side of the
crusta pass from the frontal lobe of the hemisphere, the outer ones
from the occipital and temporal lobes, whilst fibres from the fronto-
parietal regions, with the pyramidal tract, occupy the intermediate
station.

The substantia nigra (fig. 269) is a layer of dark grey matter which
separates the crusta from the tegmentum. In transverse sections it
is seen to be convex towards the crusta, and thicker at the inner than
at the outer side.
Tegmentum. The tegmentum is united internally with the like structure of the
opposite side below ; but higher up, the two are separated by the
grey matter of the posterior perforated .space. It consists of a
recticular formation continuous with that of the pons, together with
a considerable bundle of fibres derived from the cerebellum (sujjerior

Crusta.

Substantia
nigra.

STRUCTURE OF THE CRUS CEREBRI. 743

peduncle of the cerebellum), in connection with which a roundish
mass of grey substance named the nucleus of the tegmentum or red Red
nucleus (fig. 283, p. 775) may be seen on transverse section of the fore ""<^^'^"^-
part. Above, the tegmentum joins the under surface of the optic
thalamus.

Between the tegmentum and the substantia nigra will be seen, on stratum
section, an intermediate greyish layer known as the stratum medium,
intermedium, and above this, and along the outer margin of the
tegmentum in the region of the inferior quadrigeminal body, will be
seen a whitish band, the fillet (tig. 269).

The POSTERIOR PERFORATED SPACE (fig. 268, g) is situate in the Posterior

depression between the crura cerebri. The bottom of this hollow is Jpot^*^^
formed by a layer of grey matter, which is perforated by the central
branches of the posterior cerebral arteries. This structure forms the
hinder part of the floor of the third ventricle.

The CORPORA ALBiCANTiA (corp. mamillaria ; e) are two round Corpora
white bodies, about the size of small peas, which are constructed in * **^" '**

inf. quad, body oquoliujt of Syluiua

~ lamina ijuaJrijcmintt

^rey matter of '
aqueduct ""''
fillet

sup.ped. of
cerebellum

Fig, 269. --Transverse section of the Cruri Cerebri through the
Superior Corpus Quadrigeminum.

greater part by the crura of the fornix. If one, say the right, is
cut across, it will be seen to contain grey matter.

The TUBER ciNEREUM [h) is a portion of the thin grey layer forming xuber
the floor of the third ventricle, which is continuous behind with the cmereum
grey matter of the posterior perforated space, and in front, above
the optic commissure, with the lamina cinerea. It is convex on the
surface, and is prolonged at its fore part into the foil-owing body.

The INFUNDIBULUM is a funnel-shaped tube which reaches from and in-
the tuber cinereum to the posterior lobe of the pituitary body. It ^»i°<ii^"''i'"-
consists of a layer of grey matter ; and its cavity is a part of the
third ventricle. In the foetus this tube is open between the third
ventricle and the pituitary body, but in the adult it is closed below.

The PITUITARY BODY will be very imperfectly seen when it has Pituitary
been dislodged from its resting place : it should therefore be ^"
examined when opportunity otters in the base of the skull by
removing the surrounding bone.

It is situate in the hollow of the sella Turcica on the sphenoid situation ;
bone, and consists of two lobes, anterior and posterior. The anterior two lobes.
is the larger, and is hollowed out behind, where it receives the round
posterior lobe. In the adult this body is solid and firm in texture ;

744

DISSECTION OF THE BliAlN,

Dissection.

Grey
lamina.

Corpus
callosum

ends below
in two
bands,

and'extends
into hemi-
sphere.

Vallecula
Sylvii,

perforated

space.

Olfactory
lobe

lies in

olfactory

sulcus.

Olfactory
bulb.

Olfactory
tract :

roots, outer

and inner.

but in the foetus it is hollow, and the posterior lobe opens into the
third ventricle through the inlundibulum.

Dissection. To see the lamina cinerea and the anterior end of
the corpus callosum, the hemispheres are to be gently separated from
each other in front.

The LAMINA CINEREA (fig. 268, 7?i) is a thin concave layer of grey
substance, which gradually tapers upwards from the tuber cinereurn
to the termination of the corpus callosum. This stratum closes the
anterior part of the third ventricle l)etween the two central hemi-
spheres, and is continuous laterally with the anterior perforated
space. In consequence of its great thinness, this structure is often
broken through in removing the brain.

The CORPUS CALLOSUM (n), bent downwards in front, is continued
horizontally backwards in the longitudinal fissure to the lamina
cinerea, and ends by two white narrow bands — the peduncles of the
corpus callosum (or suh-callosal convolutions), which are continued
along the edge of the lamina cinerea on each side to the anterior
perforated spot. The anterior bend of the corpus callosum is known
as the genu (fig. 274, p. 757), and the recurved portion is known as
the rostrum; but this, with the other parts of the corpus callosum,
will be seen to more advantage later.

Vallecula Sylvii and anterior perforated space. The
vallecula Sylvii is a depression between the optic commissure and the
fore part of the temporal lobe of the hemisphere, which lodges the
upper end of the internal carotid artery. Externally it leads into
the Sylvian fissure, and in front it is bounded by the diverging roots
of the olfactory tract. The floor of the fossa is formed by a layer of
grey matter which is perforated by the central branches of the
anterior and middle cerebral arteries, thus giving rise to its name as
the anterior perforated space.

The OLFACTORY LOBE consists of an elongated nerve-like part
which is named the olfactory tract, and a terminal expansion in front
— the olfactory bulb. It lies in a groove (olfactory sulcus ; fig. 272,
p. 750, ol) on the surface of the inner orbital convolution of the
frontal lobe of the hemisphere.

The olfactory bulb (fig. 268, o) is an oval mass, of a greyish colour,
and nearly half an inch in length, which rests on the cribriform
plate of the ethmoid bone. From its under surface the olfactory
nerves arise.

The olfactory tract is a prismatic band, about an inch long, the
upper edge of which is received into the olfactory sulcus. It is
attached by its base, where it is somewhat expanded, to the frontal
lobe close in front of the anterior perforated space ; and from this
part two diverging white streaks, the inner and oider olfactory roots,
proceed to neighbouring convolutions. The external root passes
along the outer margin of the anterior perforated space, and across
the beginning of the Sylvian fissure, to the anterior extremity of the
temporal lobe. The internal root, not always visible, bends inwards,
and joins the lower end of the subcallosal convolution. By raising

FISSURES, SCLCI AND CONVOLUTIONS. 745

the olfactory lobe from its sulcus, the dorsal ridge will be seen to Olfactory
become enlarged at its posterior end, forming the olfactory tubercle.

Position of the part. Now that the base of the cerebrum has Position f
been studied, the brain should be turned over for the examination of eSmiS
the upper part. Something should tlien be placed beneath the fore upper part,
part, in order that it may be raised to the same level as the back ;
and a roUed-up cloth should loosely encircle the whole, to support
the hemispheres.

THE FISSURES, SULCI AND CONVOLUTIONS OF THE CEREBRAL
HEMISPHERE.

Upper Surface of the Cerebrum, Viewed from above, the cerebrum m
cerebrum is ovoidal in form, and the upper surface is convex in ^ve^and
accordance with the shape of the skull.

A median longitudinal Jissure divides it incompletely into halves, divided into
At the front and back the hemispheres are quite separated by it ; but Vidian*
at the middle and under parts they are united by connecting bodies, fissure,
the largest of which is the white corpus callosum. The falx cerebri
is lodged in the fissure.

Each hemisphere is larger in front than behind, although the Hemisphere
greatest breadth is placed behind the middle. Its outer surface is
convex and applied to the skull, and the inner is flat and rests
against the falx cerebri. The surface of the hemisphere consists of s^l o"
grey matter (cortex of the cerebrum), and is marked by tortuous marked by
eminences separated by grooves. The eminences are named convolu- tion^^and
tions or gyri; the grooves are either fissures or sulci. furrows.

Tlie grooves are of tu'o kinds. The greater number are superficial Furrows are
depressions which carry inwards the grey cortex and only indent the *°^°'"P
central white substance, and are called sulci ; a few, however, penetrate
more deeply, and are the result of folds involving the whole thickness and
of both grey and white substance of the hemisphere, so as to affect the '^ ™P ^ •
form of the cavity (lateral ventricle) contained within or to give rise
to eminences projecting on its v.'all. These hollows are distinguished
as fissures.

The convolutions and sulci, especially the smaller ones, vary in Convoiu-
different brains, and they are not exactly alike even in the two ^^^^ ^*'^^'
hemispheres of the same cerebrum. Their general arrangement or
plan is, however, sufficiently constant, and there will seldom be plan is
much difficulty in recognising the several parts referred to in the ""' °""*
following description.

Interlobar Sulci and Lobes of the Hemisphere. The outer Division of
surface of the hemisphere is divided into regions, or groups of con- sphere™^
volutions, known as the lohes of the cerebrum, by means of some of
the most constant fissures or sulci, aided by lines prolonged from
these. The interlobar sulci are three in number, viz. : —

The fissure of Sylvius (fig. 270, s) begins at the vallecula Sylvian
Sylvii, whence it extends transversely outwards across the under
surface of the hemisphere, separating the frontal and temporal lobes.

746

DISSECTION OF THE BRAIN.

Las three
branches.

As soon as it reaches the outer surface, it gives off one small branch .
forwards, the anterior limh (fig. 270, s'), and another upwards, the
limb{s"), which project into the inferior frontal convolution,

Fig. 270.- Sulci and Convolutions of the Outer Surface of the
Hemisphere.

Fissures and StdcL

Convolutions :

s. Fissure of Sylvius ; s', its an-

SF. Superior.

terior, s" its ascending, aud s'", its

MF. Middle, and

posterior branch.

IF. Inferior frontal.

r. Sulcus of Rolando.

AF. Ascending frontal.

jx). Parieto-occipital fissure.

AP. Ascending parietal.

sf. Superior, and

SPL. Superior parietal lobule.

if. Inferior frontal sulcus.

s.M. Supramarginal convolution.

pr.c. Priecentral sulcus.

Anf/. Angular.

ip. Intraparietal.

so. Superior.

2)t. c. Postcentral (superior).

MO. Middle, and

cm. End of calloso-marginal sulcus.

10. Inferior occipital.

s'. First temporal or parallel sul-

ST. First.

cus, and

MT. Second, and

mt. Second temporal sulcus.

IT. Third temporal.

Note. — The inferior parietal lobule

is commonly described as consisting of

these parts : —

1 . The supra-marginal surround-

sulcus.

ing the upturned end of the fissure of

3. The postparietal surrounding

Sylvius.

the upturned end of the second

2. The angular surrounding the

temporal sulcus.

upturned end of the first temporal

Only the first two of these ai-e represented on the figure. The upturned,
posterior, part of the second temporal sulcus is often separate from the
anterior part.

and then continues backwards as the posterior limh (s") through
about the middle third of the hemisphere. The posterior limb
separates the temporal from the frontal and parietal lobes ; it ascends

LOBES OF THE CEREBRAL HEMISPHERE. 747

somewhat as it ruus backwards ; and at its termination it is
bent upwards for a short distance and projects into the parietal
lobe.

When the brain is in the skull, the place of division of the Position in
fissure of Sylvius is opposite the articulation of the great wing ^ueSfof^
of the sphenoid with the parietal bone ; or opposite a point one head,
and a quarter inches behind the external angular process of the
frontal bone and quarter of an inch above the level of that process
on the undissected head.

The sulcus of Rolando (central sulcus; fig. 270, r) crosses the Sulcus of
outer surface of the hemisphere near the middle. Beginning above ^^'*°*^**
close to the margin of the great longitudinal fissure, the furrow-
runs downwards and somewhat forwards, with a serpentine course,
to end about one inch behind the place of division of the Sylvian
fissure, and very near to its posterior limb. This sulcus separates
the frontal from the parietal lobe.

The upper end of the furrow of Rolando is placed from an is behind
inch-and-a-half to two inches beliind the coronal suture, and the suture.
lower end about one inch. In the undissected head its upper end

half an inch behind a point midway between the glabella and
Lue external occipital protuberance, measured along the convexity of
the skull, and the general direction of the sulcus is downwards and
forwards towards the mid-point of the zygoma.

The parieto-occipital Jiss^ire (fig. 270 and fig. 273, p. 753, po) is Parieto-
a deep hollow at the hinder part of the inner surface of the hemi- assure ;
sphere. Its upper end appears on the superior surface of the
cerebrum about midway between the sulcus of Rolando and the
posterior extremity of the hemisphere, and extends outw^ards for
nearly an inch from the margin of the longitudinal fissure. It
indicates the anterior limit of the occipital lobe. The part on the
mesial surface of the hemisphere is often called the interned, and
that on the outer surface the external parieto-occipital fissure.

The fissure is placed opposite the summit of the lambdoid suture, situation.

Lobes. The outer surface of the hemisphere is divided into five Lobes of
lobes (excluding the olfactory) which have the following names and ^™'^P
limits : —

The frontal lobe forms the anterior half of the hemisphere. It is Frontal lobe
limited below by the posterior branch of the fissure of Sylvius '*' ^'^^^ '
(fig. 270, s'"), and behind by the sulcus of Rolando (r). Its under
part, which rests on the roof of the orbit, is named the orbital orbital
lobuU. ^°^'^'"-

The parietal lobe is little more than half the size of the frontal. Parietal
Its anterior limit is the sulcus of Rolando (r), and its posterior a ^ '
line drawn transversely over the hemisphere from the parieto-
occipital fissure. Below, it is bounded in its fore part by the boundaries
posterior branch of the fissure of Sylvius {s"), and in its hinder ^3*5."^ ^"^^^^
part by a line extending backwards from the spot where this artificial,
fissure turns upwards to the line draw^n transversely outwards from
the parieto-occipital fissure. This limitation of the lobe is quite
arbitrary and can be used only for descriptive purposes, since its

748

Occipital
lobe.

Temporal
lobe.

DISSECTION OF THE BRAIN.

convolutions are continuous with those of the occipital lobe behind,
and of the temporal lobe below.

The occipital lobe is small, and triangidar in shape. It is
separated from the parietal lobe for a short distance above by the
parieto-occipital fissure (jjo) ; bttt its anterior boundary is for the!|
most part artificial, being constituted by the line just mentioned, |
continuing the direction of that fissure across the outer surface of
the hemisphere. Its convolutions join those of the parietal and
temporal lobes.

The temporal lobe projects into the middle fossa of the liase of
the skull. Its fore part is separated from the frontal and parietal
lobes by the fissure of Sylvius, but its hinder part is only limited
by the lines above mentioned, across which its convolutions pass
into those of the parietal and occipital lobes.

Sulcus of Rolando.

Fronto-parietal operculum.
Frontal operculum. -• - ":

Short gyri of tlie island.

Temporal operculum.
Central .sulcus.

Fig. 271. — The Island of Reil, showing where the Opercula
have been cut away.

Central
lobe, or
island of
ReU,

surrounded
by three
sulci of Reil.

Opercula
of tlie
insula ;

Other convolutions of this lobe will be seen on the under surface
of the hemisphere.

The central lobe, insula, or island of Eeil (fig. 271), is placed at
the bottom of the fissure of Sylvius, and is concealed by the over-
lapping of the temporal, parietal and frontal lobes. If the margins
of the Sylvian fissure be drawn asunder, the island will be seen to
have a triangular form, with the apex directed downwards towards
the anterior perforated space, and to be bounded by three furrows
(the sulci of Reil), one in front, one above, and anotlier behind ; the
hinder one being continuous with the posterior branch of the fissure
of Sylvius. The central lobe is placed opposite the lenticular
muscles of the corpus striatum in the interior of the hemisphere.

The i^ortions of the frontal, parietal and temporal lobes which
overhang, and conceal, the island are called opercula of the insula.
These opercula have been cut away to expose the island in fig. 271,

CONVOLUTIONS OF THE FRONTAL LOBE. 749

but the whereabouts of each is indicated. (Compare figs. 270 and
272).

The opercula are called (1) orbital, (2) frontal, (3) fronto-
parietal, and (4) temporal.

1. The orbital operculum is the back part of the posterior orbital,
orbital convolution (P.O., fig. 272) of the frontal lobe which conceals

the front part of the island.

2. The. frontal operculum is the overhanging piece of the frontal frontal,
lolje between the anterior and ascending limlis of the Sylvian
fissure.

3. The front o-parietal operculum is the part belonging to the fronto-
frontal and parietal lolies that overlaps the island behind the P*'"'^^^'
ascending limb of the fissure of Sylvius.

4. The temporal opeixulum is the projecting anterior part of temporal,
the temporal lol)e.

Sulci and convolutions of the frontal lobe. On the outer
surface of the frontal lobe there are four convolutions, separated by
three sulci.

The pr(€central sulcus (fig. 270, j:>r c) is placed in front of, and Frontal
neiirly parallel to, the lower half of the sulcus of Rolando. From t^nsvSser
it the inferior frontal sulcus {if) runs forwards and downwards, and two
towards the orljital surface of the lobe. Al)Ove this, the superior tudnial.
frontal sulcus (sf), which is often interrupted once or t\\'ice by cross
gyri, takes a similar course.

The ascending frontal convolution (af) is simple, and forms the Frontal con-
hindmost part of the frontal lobe, extending from the upper margin t^nsl^rse •
of the hemisphere to the Sylvian fissure, along the front of the
furrow of Rolando. From its fore part the three longitudinal
convolutions of this lobe take their origin.

The superior frontal convolution (sf) is longer and broader than superior,
the others, and is commonly subdivided by a special sulcus
paramedians into secondary gyri. It lies between the margin of
the hemisphere and the upper frontal sulcus.

The middle frontal convolution (mf) runs from the ascending middle,
frontal to the lower margin of the lobe, between the upper and
lower frontal sulci. Like the superior frontal convolution, it is
also often subdivided into upper and lower parts by a sulcus {sulcus'
frontalis medius, Eberstaller) running along it.

The inferior frontal convolution (if) is the smallest of all. Spring- and inferior
ing from the lower end of the ascending frontal convolution, it arches [u^fnal
round the ascending and anterior bmnches of the Sylvian fissure,
and passes into the posterior orbital gyrus. It is sometimes described Three parts
as consisting of three parts : — inferior :

1. pars hasilaris, between the ascending limb of the fissure of pars
Sylvius and the inferior part of the praecentral sulcus. ^"^'

2. pars triangularis, between the ascending and anterior limbs of pars
the Sylvian fissure, being only another name for the frontal
operculum ; and

3. the pars orbit alis, the part below the anterior limb of the pars

n r c« 1 • orbi talis.

nssure of Sylvius

730

DISSECTION OF THE BKAIN.

Orbital
sulcus and
gyri.

and post-
central.

Convolu-
tions :
ascending
parietal

Orbital lobule (fig. 272). The orbital lobule is subdivided by a Y-
or H-shaped orbital sulcus (orb) into three convolutions, named
internal (lo), anterior (ao), and posterior (po), orbital, which are the
continuation respectively of the superior, middle, and inferior
frontal convolutions. On the internal orbital convolution is a longi-
tudinal groove — olfactory
sulcus (ol), for the recep-
tion of the olfactory lobe.
Sulci and convolu-
tions OF THE PARIETAL
LOBE. In the parietal
lobe there are two named
sulci ; and four convolu-
tions are distinguished.

The intraparietal sulcus
(tig. 270, ijp) begins close
to the posterior branch
of the fissure of Sylvius,
about midway between
the upturned extremity of
this and the lower end
of the sulcus of Rolando.
It first ascends, running
nearly parallel to the
lower half of the latter
sulcus, and then is directed
backwards to the hinder
limit of the parietal lobe,
where it often becomes
continuous with the supe-
rior occipital sulcus. Com-
monly, also, it ends in a
forked manner in a sulcus,
{anterior occipital), which
passes from above down-
wards at the front of the
occipital lobe. The upper,
or horizontal, part of the
intraparietal sulcus is fre-
quently interrupted by
one or two cross gyri.
The lower, or vertical
part, is often distinguished
as the inferior postcentral sulcus, and is mostly continuous with the
following one.

The superior postcentral sulcus (ptc) continues the direction of the

ascending part of the intraparietal sulcus, and ascends behind the

upper half of the furrow of Rolando. It generally opens into the

intraparietal sulcus at the spot where the latter is directed backwards.

The ascending parietal convolution (ap) is placed opposite the

Fig. 272.-

•Orbital Lobule and Island
OF Reil.

orb. Orbital sulcus.

ol. Olfactory sulcus.

ar. Anterior, er. Superior, and pr. Posterior
sulci of Reil, the last opened by the removal
of the temporal lobe.

10. Internal, ao. Anterior, and PO. Posterior
orbital convolutions.

c. Central lobe or island of Reil.

IF, AF, and AP. Lower parts of the inferior
frontal, ascending frontal, and ascending
parietal gyri, constituting opercula.

APS. Anterior perforated space.

THE PARIETAL AND OCCIPITAL CONVOLUTIONS. 751

ascending frontal, and like that is simple, and extends from the upper
margin of the hemisphere to the posterior branch of the Sylvian
fissure. In front of it is the furrow of Rolando, round the ends of
which it joins the ascending frontal convolution. Behind, it is
limited by the superior postcentral sulcus above, and the ascending
part of the intraparietal, or the inferior postcentral sulcus below.

Parietal lobules. The larger portion of the parietal lobe behind superior
the ascending parietal convolution is divided into two parietal lobuie,
lobules by the horizontal part of the intraparietal sulcus. The
superior parietal lobule (spl) is connected in front to the upper end
of the ascending parietal convolution between the postcentral sulcus
and the upper margin of the hemisphere, and behind to the upper
occipital convolution by a small winding gyrus which is called the
first or sujoerior parieto-occipital annectant convolution (below po).
This lobule is divided into several secondary gyri.

The inferior parietal lobule is again subdivided into two, or some- and inferior
times three, convolutions, but the separation between them is often lobnie,
very indistinct. The supramarginal convolution (sm) is the anterior consisting
and larger of these ; it springs in front from the lower end of the marginal,
ascending parietal convolution, encircles the extremity of the
posterior branch of the Sylvian fissure, and ends by joining the
first temporal convolution.

The angular convolution (Aug) arises from the hinder part of the angular,
foregoing, arches over the upper end of the first temporal sulcus (st)
and descends behind that furrow to be continued into the second
temporal convolution.

A third part of the inferior . parietal lobule may also be dis- and post-
tinguished, l)ut it is not indicated in fig. 270. It is called the convoiu-
post-parietal convolution, and is continuous with the angular convolu- tions.
tion in front. It arches over the up-turned end of the second
temporal sulcus, in front of which it is continuous with the second
and behind with the third temporal convolution. Posteriorly
also it is continued into the occipital lobe and forms the inferior
parieto-occipital annectant convolution. The posterior part of the
second temporal sulcus, which it embraces, is often separate from
the anterior part of that sulcus, and can only be distinguished from
the latter l:)y the fact that it continues the direction of the furrow
backwards and upwards.

Sulci and convolutions of the occipital lobe. The occipital Occipital
lobe is divided into three convolutions, which run forwards from convolu^
the posterior extremity of the hemisphere, by two small furrows — tions are
the superior and middle occipital sulci. The superior occipital convolu- middle, and
tion (so) is united anteriorly to the superior parietal lobule by the inferior,
superior annectant gyrus ; the middle (mo) to the post-parietal con- Annectant
volution by the inferior, and the inferior (lo) to the third temporal
convolution by the occipito-temporal annectant gyrus. An inconstant
inferior occipital sulcus, at the lower margin of the hemisphere,
separates the third occipital convolution from the temporal lobe on
the under surface. The occipital convolutions are very variable,
and the sulci are frequently ill marked.

convolu-
tions.

752

DISSECTION OF THE BRAIN.

Temporal
sulci :

lirst or
parallel,

second, and
third.

Convolu-
tions.

Convolu-
tions, of
island of

Reil.

Sulci and
convolu-
tions of
inner and
tentorial
surfaces.

How to see
them.

Calloso-
marginal
sulcus.

Sulci and convolutions of the outer surface of the
TEMPORAL LOBE (fig. 270). There are fi.ve convolutions of this
lobe; the first, second and a part of the third, with their inter-
vening sulci, are seen on the outer surface and the remainder on
the under aspect of the cerebral hemisphere.

The first temporal ov 2Mr(tllel sulcus (st) is well marked, and runs
below and parallel to the posterior branch of the fissure of Sylvius,
from near the anterior extremity of the lobe, backwards and
upwards, into the inferior parietal lobule. The second temporal
sulcus {rat) takes a similar course at a lower level, but it is not so
constant as the superior ; and the third (fig. 273, it), which is also
very variable, is placed on the under surface of the hemisphere near
the margin, separating the third from the fourth convolution.

The ^rs^ temporal convolution (inframarginal ; fig. 270, st) forms
the lower boundary of the posterior branch of the Sylvian fissure,
and is continuous behind with the supramarginal convolution.
The second and third temporal convolutions (mt and it) are com-
monly united in some part of their extent. The posterior end of
the second one is joined by the angular and post-parietal gyri.
The third forms the lower margin of the lobe and joins the post-
parietal and lowest occipital gyri.

Convolutions of the central lobe (figs. 271 and 272, c).
The surface of the insula is divided by an oblique furrow — the
central sulcus of the insula, placed opposite the lower end of the
furrow of Rolando, into an anterior triangular, and a posterior
more elongated portion. The anterior part is again suljdivided
externally into three small gyri breves, and the posterior part into
two gyri longi.

Sulci and convolutions of the inner surface of the
hemisphere (fig. 273). The convolutions of the inner aspect of
the hemisphere, with which are included those of the lower surface
behind the fissure of Sylvius, are generally well defined ; but some
being so long as to reach beyond the extent of a single lobe of the
outer surface, they are not usually like those described as forming
lobes.

Dissection. The parts to be now described can only be seen
satisfactorily on a separate hemisphere, and if the students are
working with two brains, one of the hemispheres on that brain in
which the cerebellum and other parts have been removed, should be
used by separating it irom its fellow by a mesial incision. If,
however, the student possesses only the one brain, he may show
much of the inner surface by cutting off the left hemisphere as low
as the corpus callosum and examining the right side and the under
surface of the left.

Sulci. The calloso-marginal sulcus {cm) begins Ijelow the rostrum
of the corpus callosum, and arches upwards, following the curve of
the fore part of that body. It is then directed backwards as far as
the posterior extremity of the corpus callosum, where it bends
upwards and ends by notching the superior margin of the hemi-
sphere (fig. 270, cm). Its fore part is frequently interrupted by

SULCI ON THE MESIAL SURFACE. 753

one or two small gyri uniting the adjacent convolutions. Some
distance before its posterior termination it sends a small limb
upwards, which forms the anterior limit of a convolution (para-
central, fig. 273, ov) enclosing the upper end of the Rolandic, or
central sulcus on its mesial aspect.

The par ieto- occipital or perpendicidar fissure (fig. 273, jjo) is a Parieto-
deep cleft which descends from the upper margin of the hemisphere ^^^Jj^'^^
at the back part, with a slight inclination forwards, to join the

Fig. 273.-

-SuLci AND Convolutions of the Innkr Aspect of the
Hemispherb.

Fissures ami Sulci :

cm. Calloso-marginal.
po. Parieto-occipital fissure,
c. Calcarine fissure.
h. Hippocampal or dentate fissure.
coll. Collateral fissure (fourth tem-
poral hollow).

it. Third temporal sulcus.

Convolutions :
M. Marginal.
Ov. Para-central, or oval, lobule.

Call. Callosal convolution.

Q. Prgecuneus or quadrate lobule.

Cun. Cuneate lobule.

u. Uncinate convolution (fifth
temporal).

EOT. Fourth temporal (occipito-
temporal).

IT. Third temporal.

FD. Dentate convolution or fascia
dentata.

th. Taenia hippocampi.

* Cut surface of optic thalamus.

calcarine fissure on a level with the hinder end of the corpus
callosum.

The calcarine fissure (c) is nearly horizontal. It begins close to Calcarine
the posterior extremity of the hemisphere, and is directed forwards,
receiving the parieto-occipital fissure about the middle of its length,
to end a little below the splenium of the corpus callosum. It gives
rise to the eminence called the hippocampus minor in the lateral
ventricle. The posterior and anterior parts of this fissure are
developed separately at first ; and if the student opens up the
fissure near the entrance of the parieto-occipital he will see a small

D.A. 3 0

754 DISSECTION OF THE BRAIN.

convolution running across its floor from the cuneate lobe {Can].

to the back part of the fifth temporal or uncinate convolution (u).

The back part of the uncinate convolution is commonly styled the

A taut i^'^^yu^h ^^^^ the small gyrus crossing the calcarine fissure is therefore

convolution, the cuiieo-Ungual annectant convolution.

Hippocam- The hippocampal or dentate fissure (h) is placed in front of the
pal lissme. foregoing, at the inner margin of the lower portion of the hemi-
sphere, and separates the uncinate, or hippocampal convolution (u)
from the taenia hippocampi (th), which will be revealed by gently
The fissure opening up the fissure. The fissure produces the hippocampus
major in the descending cornu of the lateral ventricle, and its
relations will be better seen when that body is examined.
Collateral The collateral fissure (coll) represents the fourth temporal sulcus

fissure. Qj^^ gives rise to the collateral eminence in the lateral ventricle.
It extends from near the posterior extremity of the hemisphere to
the fore part of the temporal lobe, and is frequently broken up into
two or three parts by cross gyri.
Third The third temporal sulcus (it) is usually broken into two or three

temporal parts which run more or less parallel with the outer margin of the
temporal lobe. The posterior extremity of the sulcus is sometimes •
prolonged on to the outer surface for a short distiince.
Caiiosal The callosal sulcus is the hollow between the upper surface of the

sulcus. corpus callosum and the lower surface of the callosal convolution

(Call).
Marginal CONVOLUTIONS. The marginal convolution (m) occupies the space

tion. between the calloso-marginal sulcus and the border of the hemi-

sphere. It is much subdivided, and at its posterior extremity a
small portion is marked off by a short vertical furrow, and is
Oval lobule, distinguished as the oval or paracentral lohule (Ov.) The marginal
convolution is continuous over the border of the hemisphere with
the internal orbital and superior frontal convolutions, while the
oval lobule is formed by the upper end of the ascending frontal
and parietal convolutions.
Convoiu- The callosal convolution (gyrus fornicatus ; Gall) is narrower and

corpus simpler than the marginal. Beginning below the rostrum of the

callosum. corpus callosum, this convolution follows the curve of that body,
and turns downwards behind its posterior extremity to end in a thin
part which joins the uncinate convolution (u). It is bounded in
the greater part of its extent by the calloso-marginal sulcus, but
behind the sjiot where this furrow turns upwards it is continuous
with the prsecuneus, or quadrate lobule (q). Near its ending, it
is limited below by the calcarine fissure. Between it and the
corpus callosum is the callosal sulcus.

Prfecuneus The prcecuneus or quadrate lobule (o) is placed lietween the end
or Quadrate n ,, ^ ,, ., , ,^ /, ^ . , • •. i ^

lobule. 01 the calloso-marginal sulcus and the parieto-occipital fissure.

Much subdivided by secondary furrows, it reaches the margin of

the hemisphere above, where it is continuous with the superior

j)arietal lobule ; it joins the callosal convolution below.

lobiTi?^ The cuneate lobule (occipital lobule ; Cu7i) is triangular in shape,

the base being formed by the margin of the hemisphere. In front

I THE TEMPORAL CONVOLUTIONS. 755

of it is the parieto-occipital, and below the calcariue fissure. Small
iiregular sulci divide it into secondary gyri.

The uncinate or Jifth temporal convolution (u) extends from the Uncinate
posterior extremity of the hemisphere behind to the Sylvian fissure *"
in front, being bounded by the calcarine and hippocampal fissures
above, and by the collateral fissure below. It is somewhat
narrowed in the middle, where the callosal convolution joins it,
and enlarged in front and behind. At its fore part is a small
piece (uncus) bent backwards over the lower end of the dentate
fissure, and from this feature the convolution derives it name. The
posterior part of the convolution, that which is limited above by the lingual
calcarine fissure, is often described as the lingual convolution. futions.

The fourth temporal^ or occipito -temporal, convolution (eot) lies Fourth
between the collateral fissure and the third temporal sulcus (it), convolution.
This is frequently not distinct from the third temporal convolution,
which forms the outer margin of the temporal lobe in the greater
part of its extent.

At the bottom of the dentate fissure, the grey cortex of the
hemisphere ends in a projecting notched margin, which is named Dentate
i\\Q. fascia dent<ita or the dentate convolution (fd). This will be better gyrus,
seen subsequently.

Structure of tlie convolutions. Each convolution is continuous Form and
with the general mass of the hemisphere on the one side and is con\oiu-
free on the other, where it presents a summit and lateral surfaces, ^i^ns ;
which are covered by pia mater. A cross section will show it to
consist of a laver of cortical grey substance on the surface, which grey

" cortical

is continued at the bottom of the sulci from one eminence to another,
and of a white medullary part in the centre, which appears as a and white
process of the large medullary mass forming the greater part of the ^rts. *^
substance of the hemisphere. On examining closely the section of a
convolution in a fresh specimen, the cortex may generally be seen to Structure of
consist of three grey, and of intermediate white, layei-s arranged
alternately, covered externally by a thin white stratum, which is
most marked over the fore part of the uncinate convolution.

If a portion of the cuneate lobule be taken it will be found that
the fourth layer of the cerebral cortex is particularly distinct as a
white line running in the grey matter.

INTERIOR OF THE CEREBRUM.

Each cerebral hemisphere consists of white and grey substance, Outline of
the white forming the larger portion of the mass (medullary centre ^^^ """'
of the hemisphere), while the grey matter is chiefly disposed in a
superficial layer (cortex) which covers the medidlary centre, except medullary
over the region on the inner side whence the corpus callosum issues j ^^^"^ '^ '
but at the lower part of the hemisphere there are other collections cortical
of grey matter more or less surrounded by the medullary substance. ^^y'^masSs;
In each hemisphere is an elongated cavity, named the lateral
ventricle, which communicates with another median space — the ventricles.
third ventricle, placed close to the base of the brain.

3c 2

766

DISSECTION OF THE BRAIN.

Cut down to
smaller oval
centre of the
hemisphere.

Reflect
eallosal con-
volution.

Cingulum.

Repeat dis-
section on
right side

to show
collosal
fibres.

ITie larger
oval centre
is deeper.

Corjnis
callosum :

situation,

extent and
form;

anterior and
posterior
ends :

ftbres
transverse ;

a few longi-
tudinal.

Dissection.

The student will now proceed to examine the parts in the interior
of the hemisphere, cari-ying the dissection from above downwards.

Dissection. Supposing hoth hemispheres entire, the left is to be
cut off" to the level of the calloso-marginal sulcus. When this has
been done, the surface displays a white central mass of a semi-oval
shape (centrum ovale minus) sending processes into the convolu-
tions, and surrounded b}^ an irregular grey margin. In a fresh
brain this surface would be studded with drops of blood escaping
from the divided vessels.

Next, the eallosal convolution is to be divided transversely about
the middle, and the two pieces, taken in the fingers, are to be thrown
backwards and forwards. On its under surface will be seen a thin
band of wliite fibres, the cingulum or covered band of Reil, wdiich
bends downwards before and behind the corpus callosum.

A similar dissection is to be carried out on the opposite side ;
but in this case the student should insert his fingers into the
calloso-marginal sulcus and i)eel off the marginal convolution, and
again he should do likewise with the eallosal convolution. He
will find that the parts tear in the direction of the central white
fibres, and in this way he will obtain a good idea as to how the
fibres of the corpus callosum diverge into the convolutions above
its level.

Finally both hemispheres are to be removed to the level of the
corpus callosum.

Now a much larger white surface comes into view (centrum ovale
majus), and the white masses in the two hemispheres are seen to be
continuous, across the middle line, through the corpus callosum.

The CORPUS CALLOSUM reaches from one half of the cerebrum to the
other, and forms the roof of the lateral ventricle in each hemisphere
(fig. 279, p. 768). Its central j)art, which is exposed in the longi-
tudinal fissure, is narrow, and measures about three inches in
length from before backwards. It is nearer to the anterior than
to the posterior end of the cerebrum, and is somewhat arched from
before backwards. On each side its upper surface is free for a
short distance beneath the eallosal convolution, from which it is
separated by the eallosal sulcus.

In front, the corpus callosum is bent downwards, forming the
genu and rostrum ; and behind, it ends in a thickened part named
the splenium (fig. 274).

The fibres of the corpus callosum are for the most part directed
transversely, but on its upper surface there is a somewhat irregular,
narrow longitudinal band on each side close to the middle line (the
supra-callosal convolution or the striae longitudinales). Between the
two bands is a median groove or raphe. Farther out there may be
seen other longitudinal fibres belonging to the cingulum, if that has
not been completely removed. The longitudinal striae are prolonged
downwards in front, and are connected with tlie sub-callosal convo-
lutions or the peduncles of the corpus callosum.

Dissection. In order to see the thickness of the corpus callosum,
and to bring into view the parts in relation with its under surface,

THE CORPUS CALLOSUM.

757

a cut is to l>e made through it on the right side about half an inch
from the middle line ; and this is to be extended forwards and
Uickwards, as far as the limits of the underlying ventricle. While
cutting through the corpus callosum, the student may observe that
a thin meml>raniforin structure (ependyma) lines its under surface.

The corpus callosum is thicker at each end than at the centre, in Is thickened
consequence of a greater number of fibres being collected from the * ^*^ ^^ >

Jx>p.Moa

pineal stria
post. comm,.
pineal hodu

in^unJilj.
pit. bod

tut. ualv.
pijranvitl

Fig. 274. — Portion op a Median Section of the Brain, showing the Corpus
Callosum, Third (3) and Fourth (4) Ventricles, Arbor Vitje Cerebklli, &c.

third ventricle. Above 4, is the

In front of 3, the soft commissure
is seen cut across. Between the in-
fumlibuhim and the corpus albicans
the tuber cinereum, and behind the
corpus albicans the posterior per-
forated space and the united teg-
menta are formintj the floor of the

superior medullary velum with the
lingiila upon it, and below are the
inferior me<lullary velum and the
nodule. The pia mater and velum
interpositum are removed.

cerebrum in those positions ; and the posterior part is the thickest under

surface.

of all. Connected with its under surface along the middle at
the fore part is the septum lucidum or partition between the
ventricles (fig. 274), and behind is the fornix.

This is the chief commissural body of the halves of the cerebrum,
and it« fibres pass laterally into the medullary centre of the hemi-
sphere, in which they radiate to the convolutions.

Dissection. The left lateral ventricle is to be now opened in Dissection,
the same way as the right ; and to prepare for the examination of

758 DISSECTION OF THE BRAIN.

the cavity on the right side, as much of the corpus callosum as!

forms the roof of the space is to be removed. A part of the j

ventricle extends down into the temporal lobe towards the base of the

brain ; and to open it, a cut is to be carried outwards and do^n-

wards, through the substance of the hemisphere, along the course

of the hollow ; and the best way to do this is to remove the parts-

with a scalpel, piecemeal, carefully following the descending horn

of the ventricle imtil the parts are displayed as in fig. 275.

Brain con- VENTRICLES OF THE Brain. Five ventricles are described in the

wntrides : ^^rain ; but four of them are subdivisions of one large central

cavity, and these are lined throughout by a thin membrane named

the ependyma, Avhich is covered l)y epithelium, for the most part

ciliated. They are the two lateral ventricles, one in each cerel)ral

hemisphere, the third ventricle close to the base of the brain

lietween the two hemispheres, and the fourth ventncle between the

cerebellum and the back of the pons and medulla oblongata (fig. 274).

tiftii is The fifth ventricle is a small space between the layers of the septum

from others, hiciduui, and has not any lining of ependyma (fig. 275 b.)

Lateral The LATERAL VENTRICLE (fig. 275) is a narrow space which

ventricle, extends nearly the w^hole length of the hemisphere, and sends a

process downwards into the temporal lol)e. The cavities of the

two sides approach one another in front, where they are only

separated l)y the thin septum lucidum ; and below the hinder part

of that partition, each communicates with the third ventricle by an

aperture known as the foramen of Monro (fig. 274). At the back

there is a wider interval between them. The roof of the space is

formed in its whole extent by the fibres of the corpus callosum

passing outwards to the convolutions; in the fioor are numerous

objects which will be enumerated in connection with the several

parts of the ventricle.

Subdivision. The Ventricle consists of a central part or body, and three

processes or cornua, anterior, posterior, and middle or descending.

Body; The body is beneath the parietal lobe of the hemisphere, and

extends from the foramen of Monro to the splenium of the corpus

callosum. It is somewhat arched, with the convexity upwards, and

in its floor are seen the following parts, proceeding from without

objects in inwards (fig. 275): — 1, the hinder portion of a pyriform mass of

°"^' grey matter forming a part of the corpus striatum (caudate

nucleus ; e), 2, a slender white band — the taenia semicircularis (/ ),

3, a narrow part of the optic thalamus {g\ 4, a vascular fringe of

the pia mater— the choroid plexus {h), and 5, a thin white layer —

the lateral part of the fornix (c). It is bounded internally for a

mesial limit, short distance in front by the hinder part of the septum lucidum (6),

and behind this by the meeting of the fornix and corpus callosum.

Anterior The anterior cornu projects forwards, with an inclination dow^n-

^^' wards and outwards, into the frontal lobe. In the floor are the

boundaries, large anterior extremity {head) of the caudate nucleus and the

rostrum of the corpus callosum ; its anterior boundary is formed by

the genu of the latter body ; and internally it is separated from the

cavity of the opposite side by the septum lucidum.

THE LATERAL VENTRICLE.

The posterior cornu (o) is narrower and generally longer than the Posterior
anterior, Init its breadth and length vary much in different brains. ^°™ '
It extends backwards into the occipital lobe, being curved outwards form ;
round the parieto-occipital fissure of the internal surface of the
hemisphere. Along its inner side is an elongated white eminence inner wall

-the hippocampus minor (i), which will be seen, on pushing the

and floor.

Fig. 275.-

-ViEw OF THK Lateral Ventricles : os the Left Side the
Descending Cornu is laid open.

a. a. Ends of the corpus callosum.

b. Septum luciduro, enclosing the
.small space of the fifth ventricle.

c. Fornix.

d. Posterior pillar of the fornix or
taenia hippocampi.

e. Caudate nucleus of the corpus
striatum.

/. Taenia semiciicularis.

g. Optic thalamus.

k. Choroid plexus.

i. Hippocampus minor.

k\ Eminentia collateralis.

/. Hippocampus major.

o. Posterior cornu of the ventricle.

handle of the scalpel into the calcarine fissure, to be an infolding
of the brain wall corresponding to that fissure ; and the floor is
formed by the hinder part of the eminentia collateralis (k), which, in
the same manner as the preceding, represents the collateral fissure.

The middle or descending cmniu leaves the hinder part of the Middle
body of the ventricle opposite the splenium of the corpus callosum, ^^^ '
and runs downwards and forwards in the temporal lobe, describing direction

760

DISSECTION OF THE BRAIN.

roof;

and floor.

Septum
lucid urn :

position,

form, and
attach-
ments ;

is a double

partition,

containing

fifth

ventricle.

Dissection.

Fifth
ventricle.

Dissection,

Fornix

position and
form.

Upper sur-
face and
borders.

a curve with the convexity outwards. In the roof are contained the
fibres passing from the hinder end of the corpus callosum down-
wards and outwards into the temporal lobe, together with the pro-
longation of the caudate nucleus and the taenia semicircularis ; and
at the anterior extremity is a prominence called the amygdaloid
tubercle. The fioor is formed mainly by a long curved eminence —
the hijDpocampus major (Z), along the inner margin of which is a
thin band prolonged from the fornix — the taenia hippocampi id\
while to its outer side lies the tapering fore part of the eminentia
collateralis {k). The choroid plexus {h) is continued downwards
along the inner side of the taenia hippocampi to the lower extremity
of this cornu.

Dissection. If the student has a separated hemisphere and
opens the descending horn of the lateral ventricle as already
described, he will be able, by placing the handle of the scalpel in
the dentate fissure below, to demonstrate that the hippocampus
major is an infolding of the brain wall corresponding to that hollow.

The SEPTUM LUCIDUM (figs. 274, 275, h) is placed vertically
between the two lateral ventricles, beneath the anterior half
of the corpus callosum, to which its upper border is attached.
It is triangular in shape, with the base turned downwards and
forwards, and fixed to the rostrum of the corpus callosum. The
posterior border is oblique, and joins the fornix. Its surfaces look
into the lateral ventricles, opposite the head of the caudate nucleus.
Although often so thin as to be translucent, the septum lucidum
consists of two laminae which enclose a space — the fifth ventricle.
Each lamina is composed of white substance, with a thin layer of
grey matter internally ; and the ependyma of the lateral ventricle
covers its outer surface.

Dissection. The fifth ventricle will be exposed by cutting
through the piece of the corpus callosum which remains in the
middle line, and detaching the anterior half from the septum
lucidum.

The FIFTH VENTRICLE (vent. of the septum) is a narrow slit
in the fore part of the septum lucidum, where this is deeper.
Posteriorly and above, the laminae of the septum are united to a
variable extent. Like the septum, it is larger in front than behind.
This cavity has not any epithelial lining.

Dissection. The fornix is to be next examined. To lay bare
this body the posterior part of the corpus callosum should be
detached with care from it, and thrown backwards ; and the septiun
lucidum should also be removed from its upper surface.

The FORNIX (fig. 275, c) is a thin white layer beneath the corpus
callosum, which, projecting on each side into the lateral ventricle,
forms part of the floor of that cavity. Its central part or body is
triangular in shape, with the base turned backwards ; and it is con-
tinuous with the rest of the brain by processes named crura, or
'pillars, in front and behind.

The upper surface of the body has the septum lucidum attached
to it along the middle line in front ; and behind, its median part

THE FORNIX. 7<;i

united to the corpus callosuni. Each border is free in the

.responding lateral ventricle, where it rests on the optic thalamus,
velum interpositiuu l)eing between the two ; and along it lies
choroid plexus. Posteriorly it joins the corpus callosum in the Posterior

Idle, while on each side it sends off a small riband-like l)and — ^°
posterior pillar or tcenia hippocampi (fig. 276, c, p. 763), along the

ucave margin of the hippocampus major. At the anterior end anterior
11 is arched over the foramen of Monro, opposite the front of the ^* '
optic thalamus, and ends likewise in two anterior pillars, which
will be afterwards followed downwards to the corpora albican tia
and thence into the optic thalami.

If the fornix l>e cut across near its front, the foramen of Miuiro Under
will be opened, and the descending anterior pillars will be seen ^"
(fig. 276). When the posterior part is raised (and it must
be done with great care), it will be found to be supported on a
process of the pia mater, named velum interpositum. Posteriorly,
on the under aspect, is a triangular surface, marked by transverse is marked
lines, which are produced by the fibres of the corpus callosum
appearing in the interval between the two diverging posterior
pillars of the fornix : the part which is so defined has been called
the lyj-a (fig. 276, a).

The fornix may be described as consisting of two bands, right Fornix
and left, which are united for a certain distance in the central part t^hands
or body. According to this view, each band, commencing in the
optic thalamus and passing through the corpus albicans, arches over
the foramen of Monro, and after forming the body of the fornix, is
continued as the taenia hippocampi to the hook of the uncinate
convolution.

The FORAMEN OF MoNRO (fig. 274, p. 757) is a short slit Foramen of

between the fore part of the fornix and the optic thalamus. °°'^^'
Through it the lateral ventricle communicates with the third
ventricle, and indirectly with the one of the opposite side. It is
lined by a prolongation of the ependyma, which is thus continued
from one ventricle to the other.

The student may leave untouched for the present the velum
interpositum, and proceed to examine the l>odies which have been
enumerated in the floor of the posterior and descending cornua.

The HIPPOCAMPUS MINOR or CALCAR AVIS (fig. 275, i) is a spindle- Hippocam-
shaped prominence on the inner side of the posterior cornu of the ^^"^ """or,
lateral ventricle. If it is cut across, it will be seen to be formed formed by
by the calcarine fissure pushing outwards the wall of the cavity, £su're"^
and beneath the white layer is the cortical grey substance passing
from the uncinate convolution to the cuneate lobule at the bottom
of the fissure.

The HIPPOCAMPUS MAJOR (figs. 275, I, and 276, b) is the large Hippocam-
convex eminence in the floor of the descending cornu of the lateral P^^'^^J^'-
ventricle, and, like that, is curved, with the concavity directed
inwards. Its anterior extremity, which is named the j)es hippocampi^ pes hippo-
is somewhat enlarged and presents two or three indentations, ^'*'"P'-
resembling the foot of a feline animal.

762 DISSECTION OF THE BRAIN.

Tupnia Along the inner margin of the hippocampus is the tcenia hi^^j^o-

hippocampi. ^^^^^ q^. jijui^^ia (flg, 276, c), which is the prolonged posterior

i:)illar of the fornix ; this ends below by joining the recurved ])art

of the uncinate convolution.

Dissection. Dlssectioil. To examine more fully the hippocampus, the

hinder portions of the corpus callosum and fornix should be divided

in the middle line, and the posterior part of the right hemisphere

should be drawn away from the rest of the brain. When the pia

mater has been removed from the inner side of the hippocampus,

and this projection has been cut across, its structure will be seen.

Structure The hippocampus is covered on the ventricular surface by a

campiis!' thin medullary layer, with which the taenia blends. On its opposite

surface is the hollow of the hippocampal, or dentate, fissure of the

exterior of the brain, which is lined bv grey substance. Beneath

the taenia hippocampi the grey matter projects in the form of a

notched ridge, the fascia dentata, or dentate convolution, which is

external to the cavity of the ventricle (p. 755).

Collateral The EMiNENTiA coLLATERALis (fig. 275, k), is the triangular,

eminence, giig^j^jy convex surface occupying the floor of the posterior and

descending corniia of the lateral ventricle to the outer side of the

formed by hippocampi. It lies over the collateral fissure of the under surface

flssuref* of the hemisphere, and its extent varies greatly in different sulyjects.

Amygdaloid The AMYGDALOID TUBERCLE is a variable eminence due to a col-

*"^^^^^® ^"'^ lection of grey matter, amygdaloid nucleus (fig. 279, p. 768), on

the outer side of the uncus, with the cortical layer of which it is

continuous.

Great trans- TRANSVERSE FISSURE OF THE CEREBRUM. By drawing the

verse fissure g^parated part of the right hemisphere away from the cms cerebri
and the optic thalamus, and replacing it, the dissector will com-
prehend the position and boundaries, on one side, of the great cleft
of the brain,
is beneath This fissure lies beneath the fornix and splenium of the corpus
reaches^Sise callosum, and above the optic thalami and corpora quadrigemina
of brain. (flg^ 274, p. 757) ; and in the dissected brain it opens into the
lateral ventricle along the edge of the fornix on each side, from the
foramen of Monro to the extremity of the descending cornu. The
slit opening into the lateral ventricle (choroidal fissure) is bounded
by the edge of the fornix with the taenia hippocampi above
and by the optic thalamus and crus cerebri below. A fold of
Pia jmater pia mater (velum interpositutn) projects into the transverse fissure
beneath the fornix (fig. 276, g), and forms lateral fringes — the
choroid plexuses, which appear in the ventricles along the margins
of the slit. In the natural state the fissure is separated from the
cavity of the ventricle by the epithelium of the ependyma being
continued over the choroid plexus, and therefore does not exist as a
complete fissure except in the dissected specimen.
Parts in the The student is now to return to the examination of the parts in
the brain, the centre of the brain, viz., the fold of pia mater and its vessels,
with the third ventricle. Afterwards the corpvis striatum and optic
thalamus will be studied.

enters it.

THE VELUM INTERPOSITDM.

i63

The VELUM IXTERPOSITUM (fig. 276, g) is the fold of pia mater Veium, or
entering the great transvei-se fissure. Triangular in shape, it has mater ^**
the same extent as the body of the fornix, and reaches in front to
the foramen of Monro. The upper surface is in contact with the
fornix, to which it supplies vessels. The lower surface, looking to is over third
the third ventricle, covei-s the pineal body and a part of each optic ^^° "*^ ^'
thalamiLs : on it, close to the middle line, are the two choroid

Fig. 276. — Second View of the Dissection of the Brain, the Fornix

BEING cut through IN FrONT AND RAISED BACKWARDS.

a. Fornix.

b. Hippocampus major.

c. Tienia hippocampi.

d. Caudate nucleus.

c. Optic thalamus.
/. Choroid plexus.
g. Velum interpositum.

plexuses of the third ventricle ; and along each side is the choroid and carries
plexus of the lateral ventricle. piSiuses.

The CHOROID PLEXUS OF THE LATERAL VENTRICLE (fig. 276,/) Choroid

is the red, somewhat rounded and fringed margin of the velum inter- P'*^'^"! °*^,

1-1 • • 111 • 1 1 • p *^^ lateral

positum, which projects into the lateral ventricle, extending from ventricle.

the foramen of Monro to the extremity of the descending coriiu.

Its lower part is larger than the upper. The epithelium lining the

ventricle is continued over the choroid plexus, but it loses its cilia

in this situation. The right and left choroid plexuses are continuous

76+

DISSECTION OF THE BRAIN.

Vessels of
the velum

arteries :

with veins
of Galen.

Dissection,

Choroid
I)lexnses of
third
ventricle.

Third
ventricle

is near base
of brain.

Roof.
Floor.

Parts on the
sides.

in front
and behind.

at the anterior extremity of the velum interpositum, where they are
similarly excluded from the foramina of Monro by the epithelial
lining.*

Vessels of the velum. Small arteries have been already traced to
the velum and the choroid plexus from the cerebral and cerebellar
arteries (pp. 720, 721 and 724). There are two main ones on
each side, anterior and posterior choroid, and they supply the sui--
rounding cerebral substance. The veins of the choroid plexus
receive branches from the ventricle, and end in the following : —

Veins of Galen. Along the centre of the velum are placed two
large veins with this name ; they begin at the foramen of Monro,
by the union of branches from the corpus striatum and the choroid
plexus. Lying side l)y side in the membrane, they are usually
united into one at the posterior part of the velum ; and through
this they pass out beneath the splenium of the corpus callosum and
enter the straight sinus.

Dissection. When the velum interpositum has been raised and
thrown backwards, the third ventricle will be opened (fig. 277).
In reflecting the velum the student must be careful not to detach
the pineal body behind, which is surrounded by the membrane and
rests on the fore part of the anterior quadrigeminal bodies (fig. 277, g).
On the under surface of the velum are seen the choroid plexuses
of the third ventricle.

The CHOROID PLEXUSES OF THE THIRD VENTRICLE are tWO sliort

and narrow fringed bodies below the velum, which resemble the
like structures in the lateral ventricle.

The THIRD VENTRICLE is the narrow interval between the optic
thalami (fig, 277). Its situation is in the median plane of the
cerebrum, below the level of the lateral ventricles, with which it
communicates ; and it reaches to the base of the brain. Its
boundaries and communications are the following : —

The roof is formed by the velum interpositum with the choroid
plexuses, above which is the fornix. The floor (fig. 274) is very
oblique from behind forwards, so that the depth of the cavity is
aljout three-quarters of an inch in front and half as much behind :
its hinder part is formed hj the united tegmenta of the crura cerebri ;
and in front of these it corresponds with the parts at the base of
the brain, which lie between the crura cerebri, viz,, the posterior
perforated space, the corpora albicantia, the tuber cinereum with
the infundilndum, and the optic commissure. On the sides of the
cavity are situate the optic thalami and the anterior pillars of the
fornix (fig. 274). In front of the space are the anterior com-
missure and the lamina cinerea. Behind are the posterior com-
missure and the pineal body. Crossing the centre of tlie ventricle,
from one optic thalamus to the other, is a band of grey matter —
the middle or soft commissure ; and care should be taken that this
is not torn through in exposing the ventricle.

* Particles of brain-sand, like that in the pineal body, are sometimes present
in the choroid plexus.

THE THIRD VENTRICLE.

765

This space communicates in front with each lateral ventricle g^'^^jss^
through the foramen of Monro ; and behind is a jjassage beneath ventricles.

Fig.

277. — View of the Third and Fourth Ventricles : the former
BEING Exposed by the Removal of the Velum Interpositfm ; and the
latter by dividing thk cerebellum vertically in the middle line.
The Third Ventricle is the Interval in the Middle Line between

THE OpIIC ThALAMI.

a. Caudate nucleus.

posterior surface of the medulla

h. Optic thalamus.

oblongata.

c. Anterior commissure, seen be-

Tc. Valve of Vieussens.

veeu the anterior pillai-s of the

I. Upper peduncle of the cere-

mix.

bellum.

d. Middle or soft commi.ssure.

0. Fasciculus t«res.

e. Posterior commissure.

•p. Superior fovea.

/. Pineal stria.

r. Inferior fovea.

g. Pineal body.

s. Clava.

A and i. Corpora quadrigemina.

4. Fourth nerve arising from the

The fourth ventricle, m, is on the

valve of Vieussens.

the corpora quadrigemina into the fourth ventricle, which is named
the aqueduct of Sylvius. In the tloor, in front, there is a

766

DISSECTION ^OF THE, BRAIN.

Lining of
cavity.

Grey matter
of the
ventricle.

Corpus
striatum,

structure.

Dissection.

Caudate
nucleus
shows in
lateral
ventricle :

vems on
surface.

Lenticular
nucleus is
only seen in
sections ;

surrounded
by white
capsule.^ .^

depression opposite the infundibulum, where the cavity at an early
period of foetal life was prolonged into the pituitary body.

The ependyma lining the ventricle is continued into the neigh-
bouring cavities through the different apertures of communication,
and its epithelium is continued over the choroid plexuses in
the roof.

Grey matter of tlie ventricle. A stratum of grey matter forms the
lower part of the wall of the ventricle. Portions of this layer
appearing at the base of the brain constitute the posterior per-
forated space, the tuber cinereum and the lamina cinerea. It also
extends into the corpus albicans, forming the nucleus of that body.
At the fore part of each optic thalamus it covers the pillar of the
fornix, and ascends to the septum lucidum. In the middle of the
space it reaches from side to side, and forms the middle or soft
commissure {d).

The CORPUS STRIATUM is the large grey body a part of which has
been seen in the floor of the lateral ventricle. The grey matter
composing it is incompletely divided into two masses — caudate and
lenticular nuclei, by a layer of white fibres, named the internal
and it has received its name from the striated appearance

of this layer. The caudate nucleus, as already seen (fig. 275, e), is
intraventricular in position, whilst the lenticular is extraventricular
and requires further dissection to expose it.

Dissection. To show the composition of the corpus striatum,
the upper part of that body and of the optic thalamus should be
sliced off horizontally on the right side, until a view resembling
that in fig. 278 is obtained. The superficial anatomy of the
corpus striatum and optic thalamus may be studied on the left side
at the same time by comparison.

The caudate or intraventricular nucleus (fig. 277, a) is a long
pyriform mass of reddish-grey substance which projects into the
lateral ventricle. Its larger extremity or head (fig. 278, en) is
turned forwards, and forms the floor and outer wall of the anterior
cornu of the ventricle. The middle tapering portion is directed
backwards and outwards, along the outer side of the oj^tic thalamus,
beneath the body of the ventricle, and ends in the tail (fig. 278, m'),
which bends downwards and is prolonged in the roof of the descend-
ing cornu of the cavity nearly to its anterior extremity. Numerous
veins run over the surface of the caudate nucleus, and they may be
seen to join a larger vessel (vein of the corpus striatum) which lies
along the groove between the caudate nucleus and the optic thalamus.

The lenticular or extraventricular nucleus is entirely surrounded
by white matter, and is placed opposite the bottom of the fissure of
Sylvius, corresftonding to the Island of Reil on the exterior. It
appears lens-shaped in horizontal section (fig. 278, In), but triangular,
with the base turned outwards, when cut transversely (fig. 279,
p. 768). Internally, it is separated from the caudate nucleus
and optic thalamus by the internal capsule (fig. 278, ica to icp) ;
and externally and below, it is bounded by a thinner white layer
named the external capsule (ec).

THE COKPUS STRIATUM.

767

When the sections are carried to a little lower level than has so Consists
1 )een done (and this should now be done by removing thin slices parts :

Fig. 278. — Middle Part of a Horizontal Section through the Cerebrum
AT THE Level of the Dotted Line in the Small Figure of a
Hemisphere in the Top Left-hand Corner of the Figure
(after Dalton).

ccg. Genu, and cc spl. Spleniuni
of corpus callosuiu.

/. Foniix ; the septum lucid um,
containing the fifth ventricle between
its layers, unites the fornix with the
corpus callosum.

Iva. Anterior, and Ivi. Descending
cornu of the lateral ventricle.

en. Caudate nucleus, head, and
en', tail.

ts. T?enia semicircularis.

o th. Optic thalamus.

th. Taenia hippocampi.

h. Hippocampus major.

ic<t. Anterior limb, icg. Genu, and
icp. Posterior limb of the internal
capsule.

In. Lenticulai" nucleus.

ec. External capsule.

cl. Claiistrum.

I. Island of Reil.

Sy. Deep part of fissure of Sylvius.

of the lenticular nucleus only by horizontal sections) it wdll be putamen,
found that the nucleus consists of three parts : an outer larger and
more deeply coloui'ed portion — the putamen — and two inner, paler

768

DISSECTION OF THE BRAIN.

globus
pallidus
major and
minor.

Internal
cai^sule,

I>arts,

.source of
fibres ;

parts — the globus pallidus major and minor. The three parts are
concentrically disposed from without inwards, and faint white lines
indicate the separation Ijetween them.

The INTERNAL CAPSULE (figs. 278 and 279) is a thick layer of
white fibres, which is seen in the horizontal section to form a bend,
or genu, (fig. 278, icy), opposite the groove between the optic
thalamus and the head of the caudate nucleus. The part in front
of the genu is named the anterior limh (ica), and the longer part
behind is the jwsterior limh (icp) of the capsule. The internal
capsule is formed in large part by the fibres of the crusta of the
crus cerebri coursing upwards to the medullary centre of the hemi-
sphere, but many fibres are added from the nuclei on each side.

caad. niicl.

tccnia.aemic

-lent. nucl.

-insula

-flauBtrum

amif^d. nucl.

Fig. 279. — Coronal Section op the Cerebrum, passing through the Fore
Part op the Third Ventricle. The Anterior Position is Repre-
sented (after Merkel).

pyramidal
tract.

The pyramidal fibres, which have been traced from tlie medulla
oblongata through the pons, and crusta, occupy the anterior two-
thirds of the posterior limb. The posterior third of the posterior
limb contains a few fibres that pass directly from the tegmentum,
others which pass from the grey matter of the thalamus and,
most posteriorly, fibres radiating the optic radiation to the
angular and cuneate convolutions from the loAver visual centres
contained in the pulvinar of the optic thalamus, the external
geniculate l)ody and the anterior corpus quadrigeniinum.
The anterior limb contains fibres which are connected with the
grey matter of the head of the caudate nucleus and the cortex of
the frontal lobe. The fibres of the capsule are collected into

THE OPTIC THALAMUS. 769

paiate bundles, between which the grey matter is continued from
lie caudate to the lenticular nucleus.
On the outer side of the e:rternal capsule, separating it from the Ciaustruni.
medullary substance of the convolutions of the insula, is a third
portion of grey matter, which appeai-s, in sections, as a slightly
wavy grey line : this is named the claustrum (fig. 278, cl ; and
fig. 279), and it represents an enlarged and well-defined fifth layer
r>f the cerebral cortex.

The TiENIA. SEMICIRCULARIS (fig. 275, /) is a narrow whitish Taeuia semi-

■ ■and of longitudinal fibres, which lies along the groove between the ^"^^^ *"*'"
caudate nucleus and the optic thalamus. In front, the band
l>ecomes broader and joins the pillar of the fornix ; behind, it is
continued with the tail of the caudate nucleus into the roof of the
descending cornu of the lateral ventricle, at the lower end of which
it joins the amygdaloid nucleus.

Dissection. The anterim- commissure is next to be exposed in Anterior
its course through the cerebral hemisphere. For this purpose the ,. ^ " "^^*
remaining fore part of the caudate nucleus, the white fibres, and to show it ;
the lenticular nucleus, on the right side, must be successively
scraped away with the handle of the scalpel, and the rounded band
traced outwaixls from the spot where it is seen at the front of the
third ventricle to the medullary centre of the tempore -sphenoidal
lobe.

The ANTERIOR COMMISSURE is a round bundle of white fibres its form,
' out as large as a crow-quill, which is free only for about an eighth
: an inch in the middle of its extent, where it lies in front of the position,
[i liars of the fornix (fig. 279). Laterally, it passes outwards
I'eneath the corpus striatum, lying between the lenticular nucleus course, and
and the grey matter of the anterior perforated space, and curving
backwards, spreads out in the white substance of the temporal lobe ending,
above the descending cornu of the lateral ventricle.

The OPTIC THALAMUS (fig. 277, h) is an oval-shaped body which Optic
takes part in bounding the lateral and third ventricles. Its upper **™"®-
surface is marked by a shallow oblique groove, which corresponds upper
to the edge of the fornix. The part of the surface inside the ^"^ ^^® '
groove is in contact with the velum intei-positum ; but the
narrower outer part is free in the floor of the lateral ventricle, and
is covered by the ependyma of that cavity : at its anterior end it
forms a slight prominence known as the tubercle of the optic
thalamus. Externally this surface is bounded by the taenia semi-
circularis, which separates it from the caudate nucleus. The inner inner
surface is for the most part free, forming the lateral wall of the s">faee ;
third ventricle, but near the middle it is united to the one of the
opposite side by the middle commissure (d). Along the line of
junction of the iipper and internal surfaces is a narrow white
streak — the pineal stria (/), which springs behind from the stalk
of the pineal body, and ends in front by joining the anterior pillar
of the fornix.

The under surface is concealed, except at its hindmost part, by lower and
the crus cerebri, the tegmentum of which joins the thalamus ; and surfaces;

D.A. 3 D

770

DISSECTION OF THE BKAIN.

anterior and
posterior
ends ;

pulvinar ;

external
geniculate
body ;
structure.

Dissection
of fornix.

Origin of
fornix.

Dissection.

Midbrain.

on the outer side it is separated from the lenticular nucleus 1)y tin-
posterior limb of the internal capsule (fig. 278, ic/p).

The anterior end of the optic thalamus hounds the foramen of
Monro. The posterior end is much larger, and projects above the
superior quadrigeminal body (fig. 277, h) and crus cerebri, being
covered by the pia mater : behind and internally it forms a con-
siderable prominence called the loulviiw.r ; and below and outside,
appearing at present as if it were a part of the optic thalamus, there
is a smaller oval elevation named the external geniculate body (fig.
281, p. 772).

In the section that has been made on the right side (fig. 278),
the optic thalamus is seen to be composed of dark grey matter ;
but it appears white on the upper surface, the grey substance
being here covered by a thin medullary layer. A faint white line,
which bifurcates in front, divides the grey mass into three portions
— a small anterior, a larger internal and an external nucleus.

Dissection. The origin of the fornix in the optic thalamus
may now be followed out. As a preparatory step the anterior
commissure, the front of the corpus callosum, and the commissure
of the optic nerves should be cut along the middle line, so that the
fore parts of the hemispheres can be separated from one another.
On the left hemisphere the anterior pillar of the fornix is to be
traced downwards through the grey matter of the third ventricle
to the corpus albicans, and thence upwards into the optic thalamus.
This can readily be done by following down the pillar of the
fornix and scraping away the overlying soft grey sulistance.

The ANTERIOR PILLAR OF THE FORNIX is joined below the
foramen of Monro by the fil)res of the taenia semicircularis and
pineal stria, and then curves downwards and backwards in front of
the optic thalamus, through the grey matter of the third ventricle,
to the corpus albicans. Here it makes a turn like half of the
figure 8, furnishing a white envelope to the grey matter of that
body. Finally it ascends to the fore part of the optic thalamus, in
the anterior nucleus of which its fibres end. The ascending band
from the corpus albicans into the optic thalamus is commonly
named the bundle of Vicq d'Azir.

The bodies lying behind the third ventricle, viz., the corpora
quadrigemina, the pineal l)ody, and the posterior commissure may
1)6 next examined.

Dissection. All the pia mater should be carefully removed from
the surface of the quadrigeminal bodies, especially on the right
side, on Avhich they are to be seen. The posterior part of the
hemisphere of the same side may be taken away if this has not
been done already.

The constricted portion of the brain between the optic thalami
above and the pons and cerebellum below is known as the isthmus
cerebri or Tnesencephalon, and occupies, when the brain is in the
skull, the aperture of the tentorimn cerebelli. The dorsal part of
the mesencephalon is formed by a layer which is marked on
the surface by four eminences — the corpora quadrigemiyiaj and is

THE CORPORA QUADRIGEMIXA. 771

therefore named the lamina qnndrigemwa. The ventral part of the ^^^^
niid-brain is much larger, and constitutes the crura cerebri. The ^emina.
lamina quadrigemina is separated from the crura in the middle by

a canal the aqueduct of Si/lrnwi ; but on each side it is united with j^^^ueduct of

the tegmentum.

The CORPORA QUADRIGEMINA (fig. 277) are four prominent Ixxiies, QjJ^arhv
an upper and lower pair, which are separated l^y a crucial groove. b^"eT:
The superior, or anterior, eminence (h) is the larger, and is rather oval anterior,
in shape. The inferior, or posterior, (?") is smaller, but more prominent, posterior,
and rounded ; it is also whiter in colour than the upper one. From
the outer side of each quadrigeminal body a white Imnd, brachium Bracbia.
(fig. 281) is continued outwards and forwards : the upper brachium
passes into the optic tract ; while the lower band sinks l^eneath a internal^
small but well defined oval prominence, w^hich is placed between |^y" *
the cms cerebri and the optic thalamus, and is named the internal
fieniculate body {\\g. 281).

The quadi-igeminal bodies are small masses of grey substance.

in/, quad, bod rj acjueduft of Syluiua

lamina cjuadrigemina

qrcif matter of
aqueduct

sup.ped. of
cerebellum

Fig. 280. — Traxsyersr Section of the Lower Part op the'^Midbrain.

covered by a white layer. From the grey matter of the upper one
fibres of the optic tract take origin.

Behind the quadrigeminal bodies are seen the superior peduncles
of the cerebelhmi (fig. 277, I); with the valve of Yieussens, or
superior medullary velum (k), between them. Issuing from beneath
the transverse filires of pons, and arching over the cerel^ellar
peduncle, is an oblique, slightly raised band named the fillet Below
(fig. 286 /, p. 782), which disappears under the lower quad- J^f Jfjet^'i^
ligeminal botly and its Ijrachium. seen.

The FILLET is a white fibrous tract which appears in sections of ^*^^®*' •
the pons lietween the recticular formation and the deep transverse
fibres (fig. 267^1, and fig. 280). It is formed mainly by fibres origin;
continued upwards from the anterior and lateral columns of the
same side of the spinal cord, by others from the nuclei of the
posterior columns (cuneate and gracile) of the opposite side of the
bulb, and, in its lateral portion, by fibres connected with the cochlear
portion of the eighth nerve. At the upper edge of the pons the
outer part of the fillet becomes superficial, and curving round the ending of
tegmentum (fig. 280), passes to the quadrigeminal bodies, particularly gJJ^^tJdai
to the posterior, in which many of the fibres are lost, while others part, and

3d 2

772

DISSECTION OF THE BRAIN.

inner or
deep part.

Optic tract
arises from
anteri(ir
quadrige-
niinal and
exte)nal
geniculate
bodies, and
thalamus.

decussate in the lamina qiiadrigemina, above the aqueduct of Sylvius,
with those of the opposite side. The inner fibres of the fillet main-
tain their deep position, and are continued upwards with the
tegmentum to the cerebral hemisphere.

The ORIGIN OF THE OPTIC TRACT Can now be seen (fig. 281). At
the outer side of the crus cerebri the optic tract forms a bend (genu),
and then divides into two parts. The inner and smaller of these
springs from beneath the internal geniculate body ; while the outer is
continued into the external geniculate body and the optic thalamus,
receiving also the brachium of the anterior quadrigeminal body.

The proper visual fibres pass to the grey matter (I) of the pulvinar
of the optic thalamus (2) of the external geniculate body, and (3)
of the anterior corpus quadrigeminum. The fibres passing to the

inl. aen. i

IctniiL semtA

ea:t'.qcn.b.

up. hrnrh.

itj^. hrach.

if. <^uud.b.

opt.ntrvc

Fig. 28L — Origin of the Optic Tract. The Mesencephalon is divided

CLOSE ABOVE THE PoNS.

Posterior
commissure.

Pineal
gland ;

internal geniculate body, the most posterior fibres of the tract (see
p. 728) are, apparently, not associated with vision.

The POSTERIOR COMMISSURE (fig. 277, e) is the thin foremost part
of the lamina quadrigemina, which is folded back so as to present a
rounded margin in front towards the third ventricle, above the open-
ing of the aqueduct of Sylvius (fig. 274, p. 757). On each side it
joins the optic thalamus, and to its upper part the stalk of the pineal
body is attached. It consists mainly of decussating fibres con-
tinuous with those of the fillet ; but some are said to be commis-
sural, uniting the tegmenta of the two sides.

The PINEAL BODY (coiiarium ; fig. 274) is ovoidal in shape,
like the cone of a pine, and about a quarter of an inch in length.
It lies with its base turned forwards in the groove between the
anterior quadrigeminal bodies. It is surrounded by pia mater;
and its base is attached by a hollow white stalk, below to the
posterior commissure, and above to the optic thalamus on each

THE AQUEDUCT OF SYLVIUS.

77B

side, along which it sends forwards the thin Land already described
as the pineal stria.

This body is of a red colour and very vascular. It is not com- structure,
posed of nervous substance, but consists of small follicles lined by
epithelium, and containing minute gmnular masses of calcareous
matter (brain-sand) : similar concretions are often found on its
surface, and adhering to its stalk.

The AQCEDUCT OF Sylvius (iter a tertio ad quartimi ventriculum ; Aqueduct of

fig. 274) is a narrow passage, about five-eighths of an inch
long, uniting the third and fourth ventricles and passing beneath

Sylvius.

Fig. 282. — Posterior View of the Connections between the Cerebrum,
Medulla Oblongata and Cerebellum.

1. Superior : 2, Middle ; and 8,
Inferior peduncle of the cerebellum.

4. Fillet.

5. Funiculus gracilis.

6. Tegmentum passing into the

optic thalamus.

7. Lamina quadrigemina.

8. Optic thalamus.

9. Caudate nucleus.
10. Corpus callosum.

the quadrigeminal bodies and over the united tegmenta of the
crura cerebri. It is lined by ependyma, external to which is a
layer of grey matter continuous with that of the floor of the two
cavities.

Fibres of the Cerebrum. In the cerebral hemispneres three Three sets
systems of fibres are distinguished, viz., ascending, transverse, and cerebral
longitudinal. The ascending are derived in large part from the ^^'^''' P^^"^®-
spinal cord and the low^er portions of the encephalon ; the transverse
and longitudinal connect together parts of the cerebrum.

Ascending or ijedancular fibres (fig. 282). The longitudinal fibres Ascending
entering the midbrain from the pons are collected into two sets,

?74

DISSECTIOI^ 0^ THfi BllAlK.

their origin.

Fibres of
crusta,

and of
tegmentum.

Dissection
of them

in the corims
striatum.

Ascending
fibres spread
out in
hemisphere,

forming

corona

radiata.

Transverse
fibres.

Longitu-
dinal fibres.

wliich are coutained respectively in the crusta and the tegmentiini.
In this region they are reinforced by the superior peduncles of the
cerebellum, and by fibres derived from the corpora quadrigemina,
as well as l>y others springing from the grey nuclei of the crura.
The fibres of the crusta enter the internal capsule ; and while some
(including the pyramidal tract) are continued without interruption
through this into the medullary centre of the hemisphere, others
pass into the lenticular and caudate nuclei, and fresh fil)res are
added from those bodies. The longitudinal fibres of the tegmentum
end for the most part in the grey matter of the optic thalamus,
from the outer side of which also numerous fibres are given off to
the capsule ; but one tract of tegmental fil)res, prolonged from the
fillet, passes beneath the thalamus into the hinder part of the
internal capsule, some of the outer fil)res inclining to the side and
traversing the inner part of the lenticular nucleus as they course
upwards.

Dissection. A complete systematic view of the ascending fibres
cannot now be obtained on the imperfect brain. At this stage the
chief purpose is to show the passage of the radiating fibres from
the crus through the large cerebral ganglia.

To trace the ascending fibres through the cor2)us striatum, the
caudate nucleus of this body should be scraped away (fig. 282);
and the dissection should be made on the left side, on which the
striate body and the optic thalamus remain uncut. In this pro-
ceeding the internal capsule comes into view, consisting of white
fibres with intervening grey matter of the corpus striatum, giving
the appearance of the teeth of a comb (pecten of Reil).

On taking away completely the hinder part of the caudate
nucleus, others of the same set of til>res will be seen issuing from
the outer side of the optic thalamus, and radiating to the posterior
and inferior portions of the hemisphere.

Arramjement of the ascending fibres. The fibres of the internal
capsule diverge as they pass through the grey matter of the corpus
striatum, and at the outer margin of that body they enter the
medullary centre of the hemisphere, where they decussate with the
transverse fibres of the corpus callosum, and radiate to all parts of
the hemisphere. The ascending fibres thus form in the hemisphere
a part of a hollow cone, named the corona radiata^ the apex of
which is towards the crus cerebri, and the concavity turned down-
wards. The base of the cone is at the surface of the hemisphere,
where the fibres pass into the grey cortex of the convolutions.
From the foregoing description it will be evident that the fibres
constituting the corona radiata are of two kinds, viz., those extend-
ing without interruption from the cortex to the crus cerebri, and
those uniting the cortex with the corpus striatum and optic thalamus.

The transverse or commissural fibres connect the hemispheres of
the cerebrum across the median plane. They give rise to the great
commissure of the corpus callosum, and to the anterior commissure.
These bodies have already been examined.

LoMjitudinal or collateral fibres. These are connecting fibres

FIBRES OF THE CEREBRUM.

775

which pass from before backwards, uniting together parts of the
same hemisphere. The chief bands of this system which the
student can recognise are the following : The fornix, the taenia
semicircularis, the pineal stria, the longitudinal stria of the corpus
callosum, and the cingulum. Other fibres pass in the medullary
centre between adjoining and more distant convolutions, describing
arches beneath the sulci : these are known as the association-fibres.

Dissection. The dissector may now make a transverse section
of the remains of the left hemisphere at the fore part of the optic
thalamus, when the form and relations of the lenticular nucleus
and the claustrum, together with the position of the anterior
commissure, will be apparent (fig. 279).

Cuts should also be made into the geniculate bodies to show the
grey nuclei within them.

By dividing transversely the left half of the midbrain through

knowTi as

association

fibres.

Make

sections of

lenticular

nucleus,

geniculate
bodies,

and mesen-
cephalon.

aij.S'.

nuelttf tup.^acul.1].

Fig. 283. — Transverse Section of the Upper Part of the Midbrain
(after Obersteiner).

the superior quadrigeminal body, there will be seen the grey matter
of that eminence, the crusta and tegmentum separated by the sub-
stantia nigi-a, the red nucleus of the tegmentum, and the grey
matter of the Sylvian aqueduct (fig. 283).

Finally, if the student has been working with two brains, he
should make a longitudinal section through the remains of the Lougitudi-
pons, medulla and crus, passing a shade to the left of the middle medinr"^^'
line, and on examining the cut surface below the floor of the fourth and pons ;
ventricle and below the grey matter in the floor of the remains of
the Sylvian aqueduct he will see a small, longitudinally running,
Ijaud of white fibres coming up from the deeper part^ of the
medulla. This is the posterior longitudinal bumUe, which chiefly posterior
consists of fibres running between the motor nuclei of the medulla, io"g*tudiual
pons and midbrain.

bundle.

776

DISSECTION OF THE BRAIN.

Prepare
cerebellum.

Parts to be
separated

Section V.

THE CEREBELLUM.

Dissection. The cerebellum is to be separated from the remains
of the cerebrum by carrying the knife through the optic thalamus,
so that the small brain, the corpora quadrigemina, the crura
cerebri, the pons, and the medulla oblongata may remain united
together.

Any remaining j^ia mater is to be carefully removed from the

Pous.

Culmen.

Declive

Post central
sulcus.

Pre-clival
sulcus.

Post-
clival
sulcus.

Foliviin cacuminis.
Fig, 284.— The Upper Surface op the Cerebellum.
The chief sulci are represented by thick lines.

from one
another.

Form and

position of
cerebellum.

Division
into two.

median groove on the under surface ; and the diflFerent bodies in that
hollow are to be separated from one another. I^astly, the handle of
the scalpel should be passed along a deep sulcus (the horizontal
fissure) at the circumference of the cerebellum, between the upper
and under surfaces.

The CEREBELLUM or small brain (figs. 284 and 285) is oval in
shape, and flattened from above down. Its longest diameter, which
is directed transversely, measures about four inches. This part of
the encephalon is situate in the posterior fossa of the base of the
skull, beneath the tentorium cerebelli. Like the cerebrum, it is
incompletely divided into two hemispheres ; the division being
marked by a wide median groove along the under surface, and by
a notch at the posterior border into which the falx cerebelli pro-
jects. The narrower part along the middle line imiting the two
hemispheres is known as the worm (vermis).

THE CEREBELLUM— LAMINJ^: AND SULCI.

777

Upper Surface. On the upper aspect the cerebellum is raised
in the centre, and sloped towards the sides (fig. 284). There is
not any median sulcus on this surface ; and the hemispheres are
united by a median part — the superior vermiform process. Separat-
ing the upper from the under surface, at the circumference, is the
horizontal fUssure, which extends from the middle, or pontine,
peduncle in front to the median notch behind.

The UNDER SURFACE of the cerebellum is convex on each side,
where it is received into the lower fossse of the occipital bone ; and
the hemispheres are separated by a median hollow — vallecula
(fig. 285), which is widest in front where it lodges the upper end
of the medulla oblongata ; the hinder end of the vallecula is con-

No gioove
on the upper
surface ;

halves
joined by
upper worm.

Horizontal
fissure.

A hollow
below,
which is
called
valley,

Flocculus.

Lobus
cacuminis,

Back part of the vallecula.

Fig. 285. — The Under Surface of the Cerebellum with the Medulla

Removed,
The chief sulci are distinguished as in fig. 284.

tinned into the notch at the posterior l)order, and receives the i'alx
cerebelli. At the bottom of the groove is an elongated mass named
the inferior vermiform process, which corresponds to the central
part uniting the hemispheres above. The two vermiform processes
constitute the general commissure of the halves of the cerebellum.
Lamina and Sulci. The superficial part of the cerebellum is
composed of grey substance, and is marked by concentric lam\p8e
or folia, wliich have their free edges towards the surface, and run
in a curved direction with the concavity turned forwards. The
laminae are separated by sulci, which are lined by pia mater, and
are of variable depth. Only a small number of the laminae appear
on the surface, for many others are placed on the sides of the
larger processes, and are concealed within the deeper sulci. The

and

contains
lower worm.

Surface
foliated.

Between
folia are
sulci.

Many folia
are hidden.

778

DISSECTION OF THE BRAIN.

Arrauge-
ment in
worm.

Upper lobes
ai'e

from behind
forwards,

lobus cacu-
minis,

lobus clivus,

lobus
culminis,

lobus cen-
tralis,

liiiKula.

Lower lobes
are

inferior
semilunar.

gracile,
biventral,

amygdaloid.

and the
flocculus.

laminse, especially the smaller ones, are frec[uently interrupted l)y
the junction of neighbouring sulci. On the upper asjDeet many of
the laminae pass continuously from one hemisphere to the other, with
only a slight bending forwards in the superior vermiform process ;
but those of the under surface of the two hemispheres are connected
by means of the special commissural bodies composing the inferior
vermiform process. The deepest sulci of the hemisphere divide the
laminae into groups which are known as the lobes of the cerebellum.
Lobes of the upper surface (fig. 284). On the upper surface
the hemisphere is divided into four lobes by deep sulci which arch
outwards and forwards from the superior vermiform process. Only
three of these lobes, how^ever, are wholly seen on the surface.
Tracing them from behind forwards they are : —

1. The lohiis cacuminis is semilunar in shape, and has its
two lateral parts connected across the middle line by a single
lamina {folium cacuminis), which is deeply placed at the bottom of
the median notch.

2. The lobus clivus, crescentic in shape, and wath its two lateral
parts connected across the middle line by the slope (declive) of the
superior worm.

3. The lobus culminis, similar in shape to and somewhat more
massive than the preceding ; its median portion forming the highest
part (culme7i) of the upper vermiform process ; and

4. The lobus centralis, composed of about eight laminae, w^hich
overlap the superior peduncle. Its lateral parts (alee) are concealed
by the most anterior portions of the lobus culminis.

On a mesial section of the cerebellum a small amount of grey
matter (lingula) may be seen on the upper surface of the superior
medullary velum (valve of Vieussens), in front of the central lobe
(fig. 274, p. 757), and this may be considered as the most anterior
representative of the grey matter of the upper surface of the
cerebellum.

The LOBES OP the under surface of the hemisphere (fig. 285)
are five in number. Beginning behind, and tracing them forw\ards,
they are : —

1. The inferior semilunar lobe, which is separated from the lobus
cacuminis of the upper surface by the horizontal fissure.

2. The gracile lobe, composed of four or five parallel laminae, and
often divisible into anterior and 'posterior parts.

3. The biventral lobe, triangular in shape, and subdivided into
two main parts. It reaches as far forwards as the flocculus, and is
external to the following.

4. The amygdaloid lobe, or, the tonsil, which lies to the inner
side of the biventral, and projects into the vallecula, touching the
medulla oblongata, and concealing a part of the inferior vermiform
process (the uvula), which is its rej^resentative in the middle line.

5. The flocculus, or sub-peduncular lobe, is placed in front of
the biventral lobe, and curves upwards round the lower liorder of
the cms cerebelli, l)eing attached to the general mass of the small
brain only by a narrow white stalk.

THE INFERIOR VERMIFORM PROCESS. 779

l^ARTS OF THE INFERIOR VERMIFORM PROCESS (fig. 285). Oil Lower worm

inferior vermiform process there are seen, from behind forwai-ds "'*=^"'i<^^
hrst, a small eminence, comprising seven or eight narrow tmns-
-e laminae which unite the posterior inferior and gracile lobes of
two sides and is named the tubei' valvul(e ; next, a larger, tongue- tuber
)»ed projection, which serves as a commissure to the bi ventral '

I .^, and is called the pyramid; and then a narrow elongated pyram*^
t — the uvula, at the anterior extremity of which is the rounded nodule,
uiinence of the nodule.

Ihe uvula is connected to the amygdaloid lobe on each side by
_iey strip named the fuirowed hand, and the nodide to the furrowed

ulus l>y a thin white lamina — the inferior medullary velum, but inferior"

ee these ixirts the foUowiiiL,' dissection must be made. medullary

1 - velum.

Dissection. The biventral and gracile lolies are to be sliced off jjisse^tiou

I he left side, so that the amygdaloid lobe may be everted from
valley. By this proceeding the stalk of the flocculus is

, jsed, and is seen to be continued into the thin and soft white
layer of the inferior medullary velum, which joins the nodule
internally. The furrowed band is also exposed on the side of the
uvula.

The inferior medullary velum is a thin white layer which forms a inferior
commissure to the flocculi, and is connected to the upper surface of "^/ly*^^^"^^
the nodule in the middle. Its exposed part on each side, between
the flocculus and the nodule, is semilunar in shape, and the anterior
edge is free ; but behind, it is continued into the medullary centre
of the cerebellum (fig. 274).

The furrmctd band is a narrow ridge of grey matter, notched on purrowetl
the surface, which passes from the side of the uvula to the con- ^"^•
stricted base of the amygdaloid lobe. It lies along the attached
posterior margin of the inferior medullary velum.

Structure of the Cerebellum. The interior of the cerebellum Cerebellum
consists of a large white mass — the medullary centre, from which a"wh\t« '^
oflsets proceed to the laminae and to other parts of the encephalon. medullary
The medullary centre is surrounded, except in front, where the
processes to other parts of the brain (peduncles of the cerebellum)
issue from it, by a superficial layer of grey substance — the cortex of and grey
the cerebellum ; and other small masses of grey matter are embedded ^^^ ^^'
in it.

Structure of the laniince. The laminae are seen, in the section that Laminse
has been made of the separate cerebellum or of the under part of ^J^aiiy,
the left hemisphere, to consist of a grey external portion enveloping and white
a white centre (fig, 277, p. 765). The grey matter is subdivided
into two layei*s, the superficial of which is lighter and clear, while
the deeper stratum is darker and of a rust colour. The white part
is derived from the medullary centre, which sends ofi" numerous
processes to the lobes and the bodies composing the worm, and
these, dividing like the branches of a tree, end in small offsets
which enter the several laminae.

Dissection. For the purjwse of seeing the medullary centre, i>issection.
with its contained corpus dentatum, remove all the laminae from

ISO

White
centre

consists of
radiating,

commis-
sural,

and

collateral

fibres.

Dentate

body:

situation.

and
structure.

Other grey
masses.

Superior
peduncle ;

ongm,

and
destination.

INTERNAL STRUCTURES.

the upper surface on the left side. This dissection may b«
accomplished by placing the scalpel in the horizontal fissurt
at the circumference, and carrying it inwards as far as th(
upper vermiform process, so as to detach the anterior and pos
terior lobes of the upper aspect. If the corpus dentatum doe.^
not at first appear, thin slices may be made anteriorly till it h
reached.

The medullary centre of the cerebellum forms a large oval rnasf
in each hemisphere, but is flattened and narrow in the middle
between the vermiform processes. The lateral part contains the
grey corpus dentatum, and is continued in front into a large
stalk-like process, which becomes divided into the three peduncles.
From its surface, as already stated, offsets are furnished to the
different lobes and laminae. The white centre is composed mainly
of the fibres of the peduncles radiating to the cortical grey
matter ; but there are in addition, as in the cerebrum, commissural
fibres between the two hemispheres, which are most developed at
the fore part of the superior vermiform ])rocess, and at the back
close to the median notch, as well as a system of association-fihres
uniting the laminse beneath the sulci.

The covpus dentatum is situate in the inner part of the white
mass of the hemisphere, and resembles the nucleus in the olivary
body of the medulla oblongata. It measures about three-quarters
of an inch from before back, and consists of a plicated capsule,
which when cut across by a sagittal section about a third of
the u'ay across the cerebellum from the middle line outwards,
appears as a thin, wavy, greyish-yellow line : it is open at the
fore and inner part, and encloses a core of white substance.
Through its aperture issue a band of filjres to join the superior
23ed uncle.

Between the two dentate bodies, embedded in the central white
matter, are some smaller portions of grey substance, the chief of
which is an oval mass on each side, nearly half an inch long, lying
close to the middle line in the fore part of the superior vermiform
process, and known as the roof-nucleus from its relation to the fourth
ventricle (fig. 274).

Peduncles of the cerebellum (fig. 282, p. 773). These are
three in number on each side, an upper (^) passing to the cere-
brum, a middle (') to the pons, and an inferior (^) to the medulla
oblongata.

The superior peduncle (processus ad cerebrum ; fig, 277 ^, p. 765)
is directed forwards, and disappears beneath the corpora quadri-
geraina. It is rather flattened in shape, and forms part of the
roof of the fourth ventricle. The processes of the two sides are
united by the suj^erior medullary velum, or the valve of Vieus-
sens (k). Its fibres are derived mainly from the interior of the
dentate body, but a few are added from the white centre of the
hemisphere and the worm. Beneath the corpora quadrigemina
the superior peduncle enters the tegmentum of the crus cerebri,
and crosses the middle line decussating with the one of the

THE FOURTH VENTRICLE. 781

)pposite side. The fi1>res are then connected with the red
lucleus of the tegmentum, and are continued with the longi-
udinal tegmental fibres to the optic thalamus.

The valve of Vieussens, or superior medullary velum, is a thin Vaive of
translucent white layer which enters into the roof of the upper ' *^"^'
[)art of the fourth ventricle (fig. '277, k). It is narrow in front,
but widens l^ehind, where it is continued into the medullary centre
of the worm. On each side it joins the superior peduncle. Near
tlie lamina quadrigemina the fourth nerve is attached to the valve : covered by
and its upper surface is covered by four or five small transverse ^'"S"la.
grey ridges, constituting the lingula.

The middle peduncle (processus ad pont^m), commonly named iiiddie
the crus cerebelli, is the largest of the three processes. Its fibres P^"°<^ ^•
liegin in the lateral part of the hemisphere, and are directed
forward to the pons, of which they form the transverse fibres.

The inferior peduncle (processus ad medullam) passes dowTiwards inferior
to the medulla oblongata, where it is known as the restiform body, ^^^^^l^ ^^
Its fibres begin chiefly in the laminae of the upper surface of the
hemisphere. It will be better seen when the fourth ventricle has
been opened.

Dissection. One other section (fig. 277) must be made to Dissection,
expose the fourth ventricle. The cerebellum still resting on its
under surface, let the knife be carried vertically through the centre
of the vermiform processes ; and then the structure of the worm,
as well as the boundaries of the fourth ventricle, may be observed
on separating the lateral portions of the cerebellum.

Structure of the TForm (fig. 274). The upper and lower vermi- Vermiform
form processes of the cerebellum are united in one central piece [ikTother
which connects together the hemispheres. The structure of this parts,
connecting piece is the same as that of the rest of the cerebellum,
viz., a central white portion and investing laminae. Here the
branching appearance of a tree {arbor vital) is best seen, in con-
sequence of the laminae being more di^^ded, and the white central
stalk being thinner and more ramified.

The FOURTH VENTRICLE (fossa rhomboidalis) is a space between Fourth
the cerebellum and the posterior surface of the medulla oblongata ^^^ ^^ ® '
and pons (fig. 274). It has the form of a lozenge, with the points
placed upwards and downwards. The upper angle reaches as high fonn and
as the upper border of the pons ; and the lower, nearly to the level ^^^^^ »
of the lower end of the olivary body. Its greatest breadth is breadth :
opposite the lower edge of the pons ; and a transverse line in this
situation would di\dde the hollow into two triangular portions —
upper and lower. The lower half has been named calamus scrip- calamus
torius from its resemblance to a writing pen. ^^"^ "^^"

The lateral boundaries are more marked above than below. For Boundaries
about half way down the cavity is limited on each side by the ^'^ ^* ^'
superior peduncle of the cerebellum, which, projecting over it,
forms part of the roof ; and along the lower half lies the eminence
of the restiform body, with the clava of the funiculus gracilis
(fig. 286, cl) at the inferior extremity. At the lower border of the lateral

782

DISSECTION OF THE CEREBELLUM.

Floor

middle peduncle of the cerebellum a lateral process of the cavity '
extends outwards over the surface of the restiform body.
Roof. The roof of the space is formed above l)y the valve of Vieussens

with the superior peduncles of the cerebellum, and by the inferior

medullary velum and nodule
of the inferior vermiform pro-
cess ; below by the reflection i
of the pia mater from that'
process to the medulla oblon-
gata. Between the valve of
Vieussens and the inferior
medullary velum the ven-
tricle forms an angular recess,
the apex of which is directed
towards the medullary centre
of the worm.

The floor of the ventricle
(fig. 286) is constituted by
the posterior surface of the
medulla oblongata and pons,
and is greyish in colour.
Along the centre is a median
groove, which ends below,
near the point of the calamus,
in a minute hole — the aper-
ture of the canal of the cord.
On each side of the groove
is a spindle-shaped elevation,
the fasciculus s. eminentia
teres (ft). This eminence
reaches the whole length of
the floor, and is pointed and
well defined below, but less
distinct above. Its widest
]mrt is opposite the centre of
the ventricle.

Crossing the floor on each
side, at the lower border of
the pons, are some white
lines — the auditory strice
(a st), which vary much in
their arrangement : they issue

fasciculus
teres.

auditory
striH*,

Fig. 286. — Back of Medulla Oblon-
gata AND Pons, showing the floor

OF THE fourth VeNTRICLE.

/. Fillet.
sp. Superior.
mp. Middle, and

ip. Inferior peduncle of the cerebellum ;
attached to the superior peduncle on the
left side is the half of the superior me-
dullary velum, covered l)y the lingula. .
ft. Fasciculus teres.
fs. Superior fovea.
fi. Interior fovea.
a St. Auditory striae.
rh. Restiform body.
cl. Clava. Crossing the restiform body
of the right side, below the auditory
striae, is the lingula.

from the median groove, and

outwards to the auditory nerve.

The fasciculus teres is limited externally by tAvo small depressions

— the superior and inferior fovea;, separated by the auditory strise.

superior anil The su'perior( fs) is the broader, and is connected to the lower one

inferior by a faint groove. The inferior fovecB (fl) is well marked, and has

the form of the letter Y inverted. The triangular portion between

the two branches is of a darker colour than the surface on each side,

fovea,

NUCLEI OF THE CKAXIAL NERVES.

783

auditory
tubercle,

nucleus of
sixth nerve,

JBo

and is named the ala cinerea (fig. 287, ac) : it corresponds to the aia cinerea

nucleus of the vagus nerve. On the outer side of the fovea the

surlace is elevated over the principal nucleus of the auditory nerve,

forming the auditory tubercle (at),

which is crossed hy the auditorj' jn;

striae.

In the upper half of the floor of
the ventricle there may he seen, on
the inner side of the superior fovea,
a rounded elevation of the fasciculus
teres, produced l)y the nucleus of the
.sixth nerve. And lastly, above the
superior fovea is a narrow, slightly
depressed area of a bluish colour (locus
caeruleus), caused by a depasit of very
dark grey substance (substantia ferru-
ginea) beneath the thin surface -layer.

The fourth ventricle communicates
al)ove with the third ventricle through
the aqueduct of Sylvius, and with the
sul (arachnoid space l)elow through an
aipertnTe ( foramen of Majendu) in the
'- 1 mater between the cerebellum and
lulla oblongata. Below, also, it
opens into the central canal of the cord.
It is lined by ependyma, the epithe-
lium of which is continued over the
pia mater in the roof, and prolonged
upwards and downwards into the
canals leading from the ventricle.

Projecting into the lower half of
the ventricle is a vascular fold on
each side, the choroid plexus, similar to
the body of the same name in the
lateral and third ventricles. It is
attached to the inner surface of the
pia mater which closes the ventricle
between the medulla and the cere-
bellum, and extends from the point
of the calamus scriptorius • to the ex-
tremity of the lateral recess of the
cavity. It receives branches from the
inferior cerebellar artery.

and locus
cjeruleus.

Openings
into other
cavities.

Foramen of
Majendie.

Fig. 287. — Diagram showing

THE POSITIOK OF THE XeRVE-
NUCLEI KEAR THE FLOOR OF
THE FOURTH VeNTRICLK. ThE

Roman numbers indicate
THE Nuclei of the corre-
sponding Nerves.

Yd. Nucleus of the descend-
ing root.

Xm. Motor nucleus, and

Vs. Sensory nucleus of the
fifth nerve.

VIIIo. Outer, and

VIII?. Inner auditory nucleus.

XI. Upper part of the spinal
accessory nucleus. On the left
side :

cq. Position of the corpora
quadrigemina.

at. Auditory tubercle.

ac. Ala cinerea.

Choroid
plexus of
ca^^tv.

The floor of the fourth ventricle
i.< covered by a layer of grey matter, which is continuous below
with the grey commissure of the cord, and above with the grey
substance of the aqueduct.

Nuclei of cranial nerves (fig. 287). In the dorsal portion
of the medulla oblongata and pons are situate the collections of
nerve-cells from which many of the cranial nerves take their origin.

Grey layer
of floor.

Nerve
nuclei in
and near

784

DISSECTION OF THE CEKEBELLUM.

floor of
fourth
ventricle.

In lower

half of floor,

four nuclei,

viz.,

of twelfth.

tenth,
ninth,

and eighth
nerves.

Beneath
upper half
are five
nuclei, viz.,

of sixth,

seventh,
two of fifth.

In midbrain
three nuclei,
viz., of
third,
fourth, and
fifth nerves.

Some of these appear in the floor of the fourth ventricle, while
others are placed a little below the surface.

Beneath the calamus scriptorius, and in the portion of the floor
of the cavity formed by the medulla oblongata, are the nuclei of the
twelfth, tenth, ninth and eighth nerves. The hypoglossal nucleus
(XII) extends through nearly the whole length of the medulla
oblongata ; its lower part is hidden, lying in front of the central
canal below the level of the fourth ventricle, but its upper half
approaches the surface in the lower portion of the fasciculus teres.
The main nucleus of the vagus (X) corresponds to the ala cinerea,
and is continued above into the chief glosso-pharyvgeal nucleus (IX)
which lies beneath the inferior fovea. The position of the inner or
principal nucleus of the vestibular division of the auditory nerve
(VIII'^) is indicated by the area acustica ; and the dorsal nucleus of
the cochlear division (VIIIo) by an enlargement just above the
acoustic strise.

In the hinder part of the pons, and beneath the upper half of the
floor of the ventricle, are nuclei of the fifth (two), sixth, seventh
and eighth nerves, but only that of the sixth is indicated by a
superficial prominence. The nucleus of the sixth (VI) lies beneath
the elevation of the fasciculus teres above the auditory striae. The
facial nucleus (VII) is placed external to and deeper than the last ;
and the motor nucleus of the fifth nerve (Vm) is above that of the
facial. The sensory nucleus of the fifth (Vs) lies external to the
foregoing, and just beyond the lateral margin of the ventricle.

Above the fourth ventricle, in the grey matter surrounding the
aqueduct of Sylvius, are the nuclei of the fourth (IV) and third (III)
nerves in the floor, and the nucleus of the descending root of the fifth
(Yd) on the side of the canal.

Further details of these nuclei are given on pages 728 to 730.

ARTERIES OF THE HEAD AND NECK.

785

TABLE OF THE CHIEF ARTERIES OF THE HEAD AND NECK.

( Infra-hyoid branch
/I. Superior thyroid

1. External
carotid .

2. lingual

3. facial

4. occipital

J superior laryngeal
(thjTXiid.

iSupra-hyoid branch
dorsal lingual
sublingual
ranine.

/ Ascending palatine branch
tonsillar
glandular
submental
inferior labial

( inferior
coronary . j superior

lateral nasal
Vangular

/ Stemo-mastoid branch
1 mastoid
. J princeps cervicis
meningeal ?
V cranial

1. Right
common
carotid

Stylo-mastoid branch
auricular

V stylo-mastoid.
r Pharyngeal branches

6. ascending pharyngeal-! prevertebral

V meningeal

5. posterior auricular . |

1. The In-
/ nominat*" .

7. superficial temporal.

\8. internal maxillary

/I. Arteriae receptaculi

Auricular
I parotid

transverse facial

middle temporal
1 anterior superficial tern-
1 poral

posterior superficial tem-
» poral.

Inferior dental

tympanic and auricular

middle and small men-
ingeal

posterior dental
•\ muscular

infraorbital

spheno-palatine

descending palatine
1 Vidian

\ pterygo-palatine.

2. Internal
carotid .

r 1. Vertebral
(with basi-
lar) . . .

_. Right
\ subcla-
vian .

2. internal
mammary

3. thyroid
axis . . .

4. supenor
intercostal.

Central of the retina
ciliary
lachrymal
supraorbital
J muscular .

2. ophthalmic. . -"^ ethmoidal (anterior ana
posterior)

palpebral

frontal

nasal.

3. posterior conununicating

4. anterior cerebral

5. middle cerebral
v6. anterior choroid.

Posterior meningeal
posterior spinal
anterior spinal
inferior cerebellar (an-
terior and posterior)
transverse basilar
superior cerebellar
\ posterior cerebral.

j Inferior thyroid ,
J suprascapular

(transverse cervical
l Deep cervical.

/ Ascending cervical
1 tracheal, oesophageal
i inferior laryngeal
(thyroid.

f Superficial cervical
1 1 nsterior scapular.

786

VEINS OF THE HEAD AND NECK.

TABLE OF THE CHIEF VEINS OF THE HEAD AND NECK.

fl. Lateral sinus

2. inferior petrosal
sinns.

Superior longitudinal
sinus (on right side)

straight sinus (on left side)/ ^ s'"°' ^^^^^^^^^^^^^

occipital sinus
superior petrosal sinus

sinus
I veins of Galen

3. pharyngeal

4. lingual .

Internal ju-
gular

Innominate
is joined by

5. facial

6. superior thyroid

7. middle thyroid.

aubclavian . External jugular

Cavernous sinus and
ophthalmic veins.

r Meningeal branches
• i prevertebral
V pharyngeal.

{Superficial dorsal
lingual venae comites
ranine.

^Angular .

inferior palpebral
lateral nasal

(Supraorbital
frontal
palpebral
nasal

I Nasal veins
anterior internal maxil- vidian
lary 1 superior palatine

• I infraorbital
j^^. J I posterior dental

submental
inferior palatine
tonsillar
glandular

anterior part of temporo-
\ maxillary

(The trunk formed
shown below).

J Thyroid
' ( laryngeal.

,, -r, , . /Anterior

/I. Posterior part of tem- posterior

poro-maxillary vein, J middle temporal
formed by temporal . ) parotid

I anterior auricular
Uransverse facial

/ Middle meningeal
inferior dental

vertebral

internal
mammary

inferior
thyroid.

/ Spinal

J deep cervical ,
I anterior vertebral
\ highest intercostal.

and internal maxillary

2. posterior auricular

3. transverse cervical

4. suprascapular
\5. anterior jugular.

Occipital.

deep temporal

pterygoid

masseteric.

j Superficial cervical
1 posterior scapular.

CRANIAL NERVEvS OF THE HEAD AND NEC^.

787

TABLE OF THE CRANIAL NERVES.

1. Fii-st nerve ,

2. Secoud nerve .

3. Tliird nerve .

4. Fourth nerve .

. Filaments to the nose.
. To retina of the eyeball,

(To ciliary muscle and sphincter iridit^
■ I external rectus and superior oblique.

. To superior oblique muscle.
Recurrent]
lachrymal .

and muscles of the orbit, except

/Ophthalmic .^

Fifth or
trifacial
nerve .

frontal

nasal

ophthalmic or / Connecting branches
lenticular i

ganglion . . ( short ciliary nerves.
Orbital branch .

superior
lary

Meckel'
glion

maxil-

spheno-palatine
posterior dental
middle dental
anterior dental
infraorbital.

Internal branches

ascending

gan-

' \ descending .

^ posterior

/ anterior part

inferior maxil-
lary

J Lachrymal
1 palpebral.

] Supraorbital
I supratrochlear.

(To lenticular ganglion
long ciliary nerves
infra trochlear
■ "N internal nasal,
external nasal.
I anterior nasal.

/ To nasal nerve
. -J to third nerve
( to sympathetic.

f Malar
' t temporal.

I Upper lateral nasal
t naso-palatine.

To the orbit.

( Large palatine
- small palatine
I external palatine.

f Vidian .

( pharyngeal.

/^ Deep temporal
1 masseteric
1 buccal
[ pterygoid.

AuriciUo-temporal

posterior part

nerve to internal ptery-

otic ganglion

submaxillary
\ ganglion .

gold

■ Connecting branches

branches for muscles

lingual .

(Connecting branches ,
branches to glands and I
mucous membrane of
mouth.

inferior dental

,To trunk of inferior
j maxillary
. - to Jacobson's nerve
I to auriculo-temporal
Ho sympathetic.

J To tensor palati
■ ( to tensor tympani.

(To the lingual, chorda
- tympani, and sympa-
thetic.

J To facial nerve
\ to symi)athetic

Articular

to meatus

parotid
I auricular
V temporal.

/To submaxillary
j ganglion
1 to hypoglossal
\ to the tongue.

iMylo-hyoid
dental
mental
incisor.

3e2

788

CRANIAL NERVES OF THE HEAD AND NECK.

TABLE OF THE CRANIAL NERVES-cantumed.
6. Sixth nerve ... To external rectus.

/ Connecting
/ brandies

Seventh nerve, or facial

bmnches for dis-
tribution

/ To join auditory
to Meckel's ganglion
J to tympanic and syn
. I pathetic nerves
I chorda tympani
to auriculo-temporal

Posterior auricular
digastric branch
stylo-hyoid branch

Eighth nerve, or auditory

/Connecting
branches

Ninth nerve or glosso-,
pharyngeal .

temporo-facial

\^ cervico-facial
To the facial

upper part .

lower part .

To vagus

to sympathetic

Jacobson's nerve .

( Temporal

- malar

' infraorbital.

^ Buccal

- supramaxillary
V inframaxillary.

10. Tenth nerve, or pneumo-/
gastric .

1 1 ^ J. ( To the pharynx
branches for dis- J tonsillitic branches
tnbution . 1 to stylo-pharyngeus
Uingual.

' To glosso-pharyngeal
to sympathetic
auricular nerve
to hypo-glossal andcer-
vical nerves.

/ To the utricle
: to the superior and ex-
i ternal semi - circular
^ canals.

/To the cochlea

J to the saccule

i to the posterior semicir-

^ cular canal.

ri'o sympathetic

I to otic ganglion, ulti-

- mately to the parotid

I gland

\^ supplies tympanum.

f Connecting
branches

branches for
tnbution

11 i?i ii I Connecting

11. Eleventh nerve, or spinal 1 branches
accessoiy -,

branches for dis-
I tribution

Pharyngeal

superior laryngeal

cardiac nerves

12. Twelfth nerve or hyjio-
glossal . . . .

/Connecting
branches

branches for diS'
tribution

inferior laryngeal , ,
gastric and intestinal

j To pneumo-gastric
1 to the cervical plexus.

f To sterno-mastoid and
1 trapezius

. To pneumo-gastric
nerve

to sympathetic

to loop on atlas
Ho lingual of fifth.

(Descending branch
thyro-hyoid nerve
to genio-hyoid
to lingual muscles.

I External laryngeal
J ascending ) ^^ *^^
j descending f mucous

* ^ membrane
Uo jom inferior laryngeal.

/ Cardiac

I esophageal, tracheal
- to inferior constrictor
I and muscles of larviix
(_ to join superior laryngeal.

SPINAL AXP SYMPATHETIC NERVES.

789

TABLE OF THE SPINAL AND SYMPATHETIC NERVES OF THE HEAD AND NECK.

Spinal Nerves.

f Superficial ( Small occipital nerve

ascending \ ^^^ auricular
ascenaing . ( superficial cenical.

/The first four form
' the Cervical

Plexus, which

grives

superficial

Acromial
clavicular

descending ."(s{^J;^i

Anterior /
/ branches \

The cervical
spinal
nerves
divide
into

posterior
branches

Tlie last four and
part of first dor-
sal form the
Brachial Plexcs,
which gives .

Are distributed to
the muscles of the
back, and give ofi"

^ cutaneous nerves.

deep int/cmal

■ deep external

Branches above
the clavicle .

branches below

To pneumo-gastric

to hypoglossal

to sympathetic

to ansa hypoglossi

to prevertebral muscles

to diaphragm.

/ To stemo-mastoid

I to levator anguli scapul?

- to scalenus medius

j to trapezius

I to join spinal accessory.

The rhomboid nerve
I to phrenic nerve
; suprascapular nen-e
" to subclavius
j posterior thoracici
^ to scaleni muscles.

j Are dissected with the upper
t limb.

Sympathetic Nerve.

. Superior
cervical
ganglion
has .

. Middle
cervical
ganglion

. Inferior
ganglion

Ascending branches,
which unite in

external branches

internal branches

l branches to vessels
Extemal branches

internal .
External .

(.internal

^ ^.j , ,., fTotvmpanic plexus

/Carotidplexus which I ^ y-j^ian nerve

gives branches . [ ^^ gj ^^.j^ ^^^^ fifth cranial nerves.

To third cranial nerve

to fourth cranial nerve

to ophthalmic nerve

to lenticular ganglion

to carotid arterj- and branches.

Cavernous plexus,
which gives
branches

( To join pneumo-gastric and

hypoglossal nerves
(to spinal nerves.

( Pharj-ngeal branches
\ superficial caixliac ner\ e.

Nervi molles.

To spinal nerves.

/ Middle cardiac nerve
1 to supply thjToid body and
"I join external laryngeal
\ loop over subclavian artery

j To spinal nerves
( vertebral plexus.

Inferior cardiac nerve,

790

CHAPTER XT.
DISSECTION OF THE EYE.

Situation of
the eyeball ;

surrounding

Parts in
front of it.

The dissec-
tion to be
made on the
eye of the
ox.

Detach the
muscles.

Foi-m of the
ball.

Position of
optic nerve.

Diameter.

Composi-
tion ;

number of
coats,
and central
parts.

Dissection.

The ej^eball is the organ of vision, and is lodged in the orbit.
Supported in that hollow on a mass of fat, it is surrounded l)y
muscles which impart movement to it ; and a thin meml)rane
(tunica vaginalis oculi or capsule of Tenon) isolates the ball, so as to
allow free movement.

Two lids protect the eye from external injury, and regulate the
amount of light admitted into the interior ; and the anterior or
exposed surface is covered by a mucous membrane (conjunctiva).

Directions. In the absence of specimens of the human eye, the
structure may be learnt on the eye of the pig or ox. Let the student
procure half a dozen eyes of the ox for the purpose of dissection.
One or two shallow^ basins will be needed ; and some wax or tallow
in the bottom of one, or in a deep plate, will be useful.

Dissection. To see the general form of the ball of the eye, and
the outer surface of the external coat, the attachments of the different
muscles are to be taken away ; and the loose mucous membrane is
to be removed from the front.

The hall of the eye (fig. 288) consists of two parts, which differ in
appearance, viz., an opaque white posterior portion (sclerotic), form-
ing about five-sixths of the whole, and a smaller transparent piece
(cornea) in front ; these two parts are segments of different sized
spheres, the anterior Ijelonging to the smaller sphere. To the back
of the eye the optic nerve is attached, rather to the inner side of the
axis of the ball ; and around it ciliary vessels and nerves enter.

The antero-posterior diameter of the liall amounts to nearly an
inch (i^ths), Imt the transverse measures an inch.

The organ of vision is composed of central transparent parts,
with enclosing membranes or coats. The coats, placed one within
another, are named sclerotic, choroid, and retina. The transparent
media in the interior are liJcewise three, viz., the lens, the aqueous
humour, and the vitreous body.

Dissection. To ol)tain a general idea of the structures to l)e
dissected, the student may destroy one eyel)all by cutting through
it circularly ; he will then be able to recognise the arrangement of
the parts mentioned above, with their strength and appearance, and
will be better prepared to follow the directions that are after-
wards given.

SCLEROTIC COAT.

791

Fibrous Coat of the Eyeball. The outer casing of the eye Fibrous
consists of an opaque hinder part called sclerotic, and of an anterior *^°**-
transparent portion, the cornea.

Tlie sclerotic is the firm, whitish, opaque portion of the outer Sclerotic
coat of the eyeball, which supports the more delicate structures P*^*
within.

Dissection. To examine the inner and outer surfaces of this layer. Dissection
it will be necessary to cut circularly with scissors through the Jn^^o?^

Fig. 288. — Diagram op a Horizontal Section of the Eyeball.

a. Sclerotic coat.

I. Optic nerve.

b. Choroid.

m. Circular fibres of the ciliary

c. Ketina, continuous with

the

muscle.

optic nerve behind,

with

dark

71. Hyaloid membrane.

layer outside it.

0. Canal of Petit.

d. Cornea.

r. Canal of Schlemm.

e. Ciliary muscle.

s. Ciliary process.

/. Iiis.

t. Suspensory ligament of lens.

g. Lens.

The dotted line through the centre is

h. Vitreous body.

the longitudinal axis of the ball.

«. Posterior chamber of the aqueous.

cornea close to the sclerotic, and to remove the cornea from the
front of the eyeball ; on piercing the cornea the aqueous fluid
escapes from the containing chamber. The other structures may
be then abstracted from the interior of the sclerotic covering, and
may be set aside in water with the cornea for subsequent use.

The sclerotic tunic of the eye (fig. 288, a) extends from the Extent of
entrance of the optic nerve to the margin of the cornea, forming ^*^ ®^ ^^ '
above five-sixths of the ball.

At its back, and a little to the inner side of the centre (one-tenth apertures

behind,

792

DISSECTION OF THE BYE.

and before

ending in
front ;

outer and
inner sur-
faces ;

thickness :

circular
sinus ;

composed
of fibrous
tissue ;
vessels
and nerves.

Cornea :

extent and
size;

form:

thickness :

surfaces :

curve;

condition
after death.

It consists
of laminar
fibrous
tissue, with
conjunctiva
in front,

and an
elastic
membrane
behind ;

of an incli), the oj)tic nerve (I) is transmitted through an aperture
in it ; this opening decreases in size from without inwards, and is
cribriform when the nerve is drawn out, — the lattice-like condition
being due to the bundles of fibrous tissue between the funiculi of
the nerve. Small apertures for the passage of vessels and nerves
are situate around the optic nerve ; and there are others for vessels
at the front and the centre of the ball. Anteriorly the sclerotic is
continuous with the transparent cornea.

On the outer surface this coat is smooth, except where the
muscles are attached : on the inner aspect it is of a dark colour,
with flocculi of fine areolar tissue (membrana fusca) uniting it to
the next coat, and with the ends of ruptured vessels and nerves.

The sclerotic covering is thickest at the back of the eyeball, but
it becomes thinner and whiter about a quarter of an inch from the
cornea, where it is visible as the " white of the eye." Towards
the junction with the cornea it is again somewhat thickened.
In its substance, near the union with the cornea, is a small
flattened venous space, the canal of Schlemm (sinus circularis iridis ;
fig. 288, r).

Structure. The sclerotic consists of bundles of fibrous tissue,
which interlace with one another, but run for the most part longi-
tudinally and transversely. Its vessels are very scanty. Minute
filaments of the ciliary nerves have been described, entering the
deep surface of the membrane.

Cornea (fig. 288, d). This firm transparent membrane forms
aljout one-sixth of the eye-ball, and measures about half an inch
across. Its shape is circular, though when viewed from the front
it appears larger in the transverse direction, in consequence of the
opaque sclerotic structure encroaching farther on it above and below
than on the sides.

It is convex in front and concave behind ; and its thickness is
nearly uniform (from gV^^ ^^ "sV^^ ^^ an. inch), except near the
circumference, where it is somewhat thicker at the junction with
the sclerotic. The anterior surface of the cornea is slightly less
extensive than the posterior, owing to its being overlapped by the
sclerotic. Supported by the aqueous humour, it is tense and
nearly spherical during life ; but its radius of curvature varies in
different individuals, and in the same person at different ages,
being shorter in the young. After death it l^ecomes flaccid from
the transudation of the aqueous humour ; or if the eye is immersed
in water, it is rendered opaque by infiltration of the tissues by that
fluid.

Structure. The substance of the cornea is composed of a special
kind of connective tissue, arranged in irregular layers. Over the
front the conjunctiva (which is here reduced to its epithelium) is
continued ; and covering the back of the cornea proper is a very
thin elastic stratum known as the membrane of Descemet. The
latter may be peeled off, after a cut has been made through it, in
shreds which curl up with the attached surface innermost. At the
circumference of the cornea the membrane of Descemet breaks up

CHOROID COAT. 793

into processes {pillars of the iris or ligamentum pectinatum iridis)
which are partlj^ reflected on to the front of the iris, and partly join
the sclerotic and choroid coats.

In the healthy condition the blood-vessels do not permeate the no vessels ;
cornea, but cease in capillary loops at the circumference. Numerous many
tine branches of the ciliary nerves ramify in its substance. nerves.

Vascular Coat of the Eyeball (fig. 289). The next cover- Vascular
ing is situate within the sclerotic, and is formed in large part of ^"^ TOat!^"
1)lood- vessels ; the muscles of the interior of the ball also belong
to this coat.

It is constructed of three parts, — a posterior {chm-oid) correspond- Compo-
ing with the sclerotic, an anterior {iris) opposite the cornea, and an "^^ ^'
intermediate ring {ciliary muscle) on a level with the union of the
sclerotic and cornea.

Dissection. Supposing the cornea of an eye cut through circularly Dissection
as before directed, it will be necessary to take away the sclerotic to ^oroid^^
lay bare the choroid coat. With the point of the scalpel or with portion.
a shut scissors, detach the fore part of the sclerotic from the front
of the choroid by breaking through a soft whitish structure uniting
them. Then, the eye being put into water, the outer coat is to be
removed by cutting it away piecemeal with the scissors ; in taking
it off, the slender vessels and nerves beneath are to be preserved.
The white ring round the eye in front, which comes into view
during the dissection, is the ciliary muscle.

For the purpose of obtaining a front view of the ciliary pro- To show
cesses, which are connected with the anterior termination of the pr^^^'sses^
choroid coat, let the cornea be removed as before on another eyeball.
Detach next the fore part of the sclerotic from the choroid ; and
after three or four cuts have been made in it towards the optic
nerve, the resulting flaps may be pinned out, so as to support the
eye in an upright position (fig. 289). On removing with care the by an
iris, taking it away fi'om the centre towards the circumference, the ^"^^"""^
ciliary processes beneath will be displayed. A posterior view of andapos-
the processes may be prepared on another ball by cutting through ^^"°^ ^ '^^ '
it circularly with scissors, about one-third of an inch behind the
cornea, so that the anterior can be removed from the posterior half ;
on taking away the portion of the vitreous mass adherent to the
anterior part of the ball, and washing off the pigment from the
back of the iris, the small processes will l^e made manifest. By
means of the last dissection the interior of the choroid coat may
be seen.

If a vertical sagittal section is made of another eyeball (fig. 290), To make a
it will show the ciliary processes in their natural position, and will Jection.
demonstrate the relative situation of all the parts. This section,
which is made with diftieulty, should be attempted in water with
a large sharp knife, and on a surface of wax or wood, after the
cornea and sclerotic have been cut with scissors. When the eye
has been divided, the halves should remain in water.

The CHOROID COAT (fig. 288, 6) is a thin membrane of a dark Choroid:
colour, and extends from the optic nerve to the fore part of the extent ;

794

DISSECTION OF THE EYE.

anterior eyeball. When viewed on the eye in ^vhich the ciliary muscle is
terminaioii, ^^^^^g^ ^^ appears to terminate there; but it may be seen in the
other dissections to pass inwards behind the muscle, and to end in
a series of projections (ciliary processes) at the back of the iris.

This covering is rather thicker and stronger behind than in
front. Its outer surface is for the most part only slightly attached
to the sclerotic by delicate bands of areolar tissue, and has a floccu-
lent appearance Avhen detached ; but in front the ciliary muscle
nnites the two coats more firmly: on this surface may be seen
small veins arranged in arches, and the ciliary arteries and nerves
(fig. 289). The inner surface is smooth, and is lined by the thin

relations of

outer

surface.

of inner ;

Fig. 289. — View uf the Front of the Choroid Coat and Ibis — External
Surface (Zinn).

/. CiHary nerves, and g, ciHary
arteries, between the two outer
coats.

h. Veins of the choroid coat (vasa
vorticosa).

a. Sclerotic, cut and reflected.
h. Choroid.

c. Iris.

d. Circular.

e. Radiating fibres of ciliary
muscle.

opening
behind.

Ciliary
processes :

arrange-
ment ;

two kinds ;

dark pigmentary layer of the retina (fig. 288). Posteriorly it is
pierced by a round aj^erture for the passage of the optic nerve ;
and anteriorly it joins the iris.

The ciliary processes (fig. 290, b) are solid projections on the
inner surface of the choroid coat, disposed radially, and forming a
circle beneath the ciliary muscle and the outer margin of the iris.
About seventy in number, they comprise larger and smaller
eminences, the former being the more numerous, and having a
length of about one-tenth of an inch. They increase in depth from
without inwards ; and at their inner ends they are united by
transverse ridges.

CILIARY MUSCLE AND IRIS.

By their free extremities the processes bound peripherally the
space (posterior chamber; fig. 291, i, p. 796) behind the iris; in
front, they correspond to the ciliary muscle, and at their inner ends
to the back of the iris ; while behind, they are closely applied to
the membrane on the front of the \itreous body (suspensory
ligament of the lens ; fig. 291, t), and fit into hollows between
eminences on the anterior surface of that structure.

Structure. The choroid coat and its ciliary processes are composed
of blood vessels supported by pigmented areolar tissue. Most
externally is a delicate stratum of connective tissue known as the
lamina suprachoroidea, similar to the membrana f usca of the sclerotic,
to which it is connected ; next

to this is a layer containing ~

the larger ramifications of the
iiiteries and veins ; and in the
deepest part the vessels form
a very fine and close capillary
network {tunica Rmjschiana).
In the ciliary processes the
meshes of the capillary net-
work are larger, and the inter-
-titial pigment disappears to-
wards the free ends of the
larger processes.

Ciliary muscle (fig. 289,
d, e). In the eye from which
the sclerotic coat has been re-
moved, the white ring of the
ciliary muscle may be seen
covering the front of the
choroid coat.

The muscle forms a circular
band, of a greyish white colour,
and about one-tenth of an inch
wide, on the surface of the
choroid coat close to the outer

relations
to parts
around.

Structure of
choroid,

supra-
choroid
layer,

and vascular
networks ;

Ciliary
muscle :

Fig. 290. — Posterior View of the
Fore Part of the Choroid Coat
WITH ITS Ciliary Processes, and
the Back of the Iris.

a. Anterior piece of the choroid
coat.

6. Ciliary processes.

c. Iris.

d. Sphincter of the pupil.

e. Bundles of fibres of the dilator
of the pupil, represented diagram-
maticaUy,

position ;

margin of the iris. It consists

of unstriated fibres, which are in two sets, radiating and circular : —

The radiating fibres (fig. 291, «) arise in front from the sclerotic
coat close to the junction with the cornea (beneath r), and are
directed backwards, spreading out, to be inserted into the choroid
coat opposite to, and a little behind, the ciliary processes. Some of
the deeper fibres becoiiie transverse, and pass gradually into the
following set.

The circular fibres are beneath the radiating, and form a narrow
bimdle (fig. 291, m) surrounding the edge of the iris, opposite the
inner part of the ciliary processes.

AcUon. The ciliary muscle draws forwards the fore part of the
choroid coat and the ciliary processes, and relaxes the suspensory
ligament of the lens, thereby allowing the lens to become more

consists of
radiating

and circular
fibres;

796

DISSECTION OF THE EYE.

Iris is vas-
cular and
muscular ;

situation ;
form;

attachment

anterior
surface ;

posterior
surface.

The pupil.

Membrane
of the pupil
in the fcetus:

situation ;

time of dis-
appearance.

convex, as required for vision at near distances. The ciliary nins( It-
is therefore the muscle of accommodation.

The IRIS (fig. 289, c) is avascular and muscular structure, about
half an inch in diameter, the vessels of which are continuous witli
those of the choroid coat. Its position and relations may be
observed in the diflFerent dissections that have been prepared.

Placed within the ring of the ciliary muscle, it is suspended in
front of the lens (fig. 288, f), and is pierced by an aperture for the
transmission of the light. It is circular in form, is variously
coloured in different persons, and is immersed in the aqueous humour.
By its 'circumference, it is connected with the choroid coat, and by
the ligamentum pectinatum with the cornea. The anterior surface

is free in the aqueous
humour, and is marked
by lines converging to-
wards the pupil. The
posterior surface is
covered M'ith a thick
layer of pigment (fig.
291), to which the term
uvea has been applied.

The aperture in it
(fig. 289) is the pwpil
of the eye ; this is
slightly internal to the
centre, and is nearly
circular in form ; l)ut
its size is constantly
varying (from a^th to
^rd of an inch) by the
contraction of the mus-
cular fibres, according
to the degree of light
acting on the retina.

Fig. 291, — Enlarged Representation of the
Parts op the Eyeball on One Side
Opposite the Lens : the Letters refer
to the Same Parts as in Fig. 288.

d. Cornea.

e. Ciliary muscle, radiating fibres.
/. Iris.
g. Lens.

i. Posterior chamber.
j. Ciliary part of the retina.
m. Circular bundle of the ciliary muscle.
11. Front of vitreous body,
o. Canal of Petit.
r. Canal of Scblemm.
s. Inner end of ciliary process.
t. Suspensory ligaiuent of the lens.

Memhranc of the pupil.
In the foetus the aper-
ture of the pupil is closed
by a Avascular transparent membrane, which is attached to the edge of the
iris, and divides into two distinct chambers the space in which the iris is
suspended. The vessels in it are continuous behind with those of the iris
and the case of the lens. About the eighth month the vessels become
impervious, and at the time of birth only fragments of the structure remain.

Component
structures.

Sphincter

and dilator
of pupil.

Structure. The stroma of the iris is com2:)osed of connective tissue,
the fibres of which are directed for the most part radially towards
the pupil. In it are involuntary muscular fibres, l)oth circular and
radiating, together with pigment-cells ; and vessels and nerves ramify

through the tissue.

Muscular fibres. The sphincter of the pupil (fig. 290, d) is a
narrow band about -^oth of an inch wide, which is close to the
pupil, on the posterior aspect of the iris. The dilator of the pupil (e)

CILIARY VESSELS AND NERVES.

707

consists of ^bundles of tibres which begin at the outer border of the
iris, and end internally in the sphincter.

Action. Enlargement of the pupil is effected by shortening of the
radiating fibres ; and diminution, by contraction of the circular ring.
The movements of the iris are involuntary, and regulate the admis^
si on of light into the l)all.

The piffmeyit of the iris is partly interspersed in the substance of
the membrane, and partly collected into a thick layer on the pos-
terior aspect, the above-mentioned uvea, which is continuous with
the pigmentary stratum of the
retina. The colour of the iris
depends upon the nature and
quantity of the interspersed
pigment.

The arteries of the iris (fig.
^92, b) have a looped arrange-
ment ; they are derived chiefly
from the long and the anterior
ciliary branches (d), but some
come from the vessels of the
■ iliary processes. On arriving

the ciliary muscle, the long
Mill anterior ciliary arteries
t'ani a circle (e) round the
margin of the iris ; from this
ring other anastoniotic branches
are directed towards the pupil,
near which they join in a
second arterial circle (/). From
the last circle capillaries run
to the edge of the pupil, and
end in veins.

The veins resemble the ar-
teries in their arrangements
in the iris, and terminate in
the veins of the choroid coat.

The nerves of the iris are
the terminal branches of the
ciliary nerves ; they divide

into branches which accompany the blood vessels, and communicate
^^'ith one another so as to form a plexus which gets gradually finer
towards the pupil (fig. 292, a).

Ciliary vessels and nerves (fig. 289). The ciliary arteries
are offsets of the ophthalmic, and supjjly the choroid, the ciliary
processes, and the iris. They are classed into posterior and
anterior, and two of the first set are named long ciliary ; but
they will not be seen without a special injection of the vessels of
the eye.

The posterior ciliary arteries (g) pierce the sclerotic coat around
and close to the optic nerve, and running forwards on the

How they
act.

Situation of
pigment.

Fig. 292. —Distribution of the Nerves
AND Vessels of the Iris.

A. Half of the iris showing the nerves.
(/. Nerves entering the membrane,

and uniting in a plexus.
b. Within it. (Kolliker.)

B. Half of the iris with a plan of the Veins
vessels.

d. Ciliary arteries.

e. Arch of vessels at the outer edge
of the iris.

/. Inner circle of vessels in the iris.
g. Sphincter of the pupil.

Nerves of
the iris.

Arteries of
the middle
coat:

posterior
ciliary,

798

two of them
named long
ciliary,

anterior
ciliary.

Veins are
posterior
ciliary,

and anterior
ciliary.

Ciliary
nerves

end in iris
and ciliary
muscle.
Space con-
taining
aqueous
humour

is partly
divided into
two by the
iris :

anterior
part;

posterior,

its bound-
aries.

Retina

is in two
parts.

DISSECTION OF THE EYE.

choroid, divide into branches which enter its substance at different
points.

Two of this set {long ciliary) are directed forwards between the
sclerotic and choroid, one on each side of the eyeljall, and form a
circle round the iris in the ciliary muscle, as l^efore explained. In
the ball the outer one lies rather above, and the inner, rather
below the middle.

The anterior ciliary arteries^ five or six in number, are smaller
than the posterior, and arise at the front of the orbit from musculai-
branches ; they pierce the sclerotic coat about a line behind the
cornea, supply the ciliary processes ; and join the circle of the long
ciliary vessels. In inflammation of the iris these vessels are
enlarged, and offsets of them form a ring round the cornea.

The posterior- ciliary veins have a different arrangement from th
arteries. The branches form arches (vasa vorticosa ; fig. 289, h) i
the superficial part of the choroid coat, external to the arteries, an
converge to four or five trunks, which perforate the sclerotic coal
about midway l^etween the cornea and the optic nerve to end in the
ophthalmic veins.

The anterior ciliary veins begin in a plexus within the ciliary
muscle, receiving tributaries from the iris and the ciliary processes,
and accompany the arteries through the sclerotic to end in the
ophthalmic trunks : they commu.nicate with the venous space of
the canal of Schlemm.

The ciliary nerves (fig. 289, /) are derived from the lenticular
ganglion, and the nasal nerve. Entering the back of the eyeball
with the arteries, they are continued with the vessels between the
sclerotic and choroid as far as the ciliary muscle : at this spot
the nerves send offsets to the cornea, and piercing the fibres of the
ciliary muscle, enter the iris. Offsets from the nerves supply the
ciliary muscle and the choroid, and fine twigs enter the sclerotic.

Chamber of the Aqueous Humour (fig. 288, p. 791). The
space. between the cornea in front and the lens behind, in which
the iris is suspended, contains a clear fluid named the aqueous
humour. In the foetus before the seventh month this interval is
separated into two by the iris and the pupillary membrane ; but
in the adult it is only partly divided, for the two communicate
through the- pupil. The boimdaries of the two chambers may be
seen in the eye on which a vertical section has been made.

The anterior chamber is the larger of the two ; it is limited iir
front by the cornea, and behind by the iris.

The posterior chamber (i) is a narrow interval behind the iris at
the circumference, which is bounded in front by the iris ; behind
by the lens capsule, and by a piece of the membrane (suspensory
ligament of the lens) on the front of the vitreous humour ; and at
the circumference by the ciliary processes.

The Eetina (fig. 288, c). This layer is the innermost and most
delicate of the coats of the eyeball, and is situate between the
choroid coat and the transparent mass (vitreous) in the interior. It
consists of two parts, viz., a thin membrane internally, continuous-

KEKVOUS PORTION OF THE RETINA.

rith the optic nerve, aud a pigmentary layer outside, which adheres
0 the choroid coat.

Dissection. The retina can be satisfactorily examined only on
m eye which is obtained within forty-eight hours after death. To
)riug it into view on the eyeball in which the middle coat was
iissected, the choroid must be torn away carefully with two pairs
jf forceps, while the eye is immersed in fluid. In this dissection
the pigmentary layer separates from the nervous portion of the
retina, and is removed with the choroid coat.

The -pigmentary portion of the retina is a very thin, dark layer,
which lines closely the inner surface of the choroid coat, and is
continued over the ciliary processes into the uvea on the posterior
surface of the iris (fig. 291).

The nervous portion of the retina is a soft membrane of a pinkish
grey tint and semitrausparent when
fresh ; but it soon loses this trans-
lucency, and is moreover rendered
opaque by the action of water and
other substances. In the living state,
however, the retina is characterised by
the existence of a purplish red colour,
which is discharged under the influence
of sunlight. This part of the retina
extends over about the posterior two-
thirds of the eyeball, reaching from
the entrance of the optic nerve to the
outer extremities of the ciliary pro-
cesses, where it ends in an irregular
wavy border — the ora serrata. Its
thickness diminishes from behind for-
wards.

The outer surface of the dissected
retina is slightly flocculent, owing to
the tearing away of the pigmentary
layer. The inner surface is smooth :
it is covered with folds in a prepara-
tion of the eye cut in two, but these are accidental, in conse-
quence of the membrane having lost its proper support. At
the spot where the optic nerve expands (poriis opticus, optic disc ;
fig. 293) the suriace is slightly elevated {papilla optica') ; but in
the centre of this is a slight excavation where the central vessels
appear.

In the interior of the human eye, in the axis of the ball, is a
slightly elliptical yellow area (fig. 293), one-twelfth of an inch in
diameter, which is named the yellow spot (macula luted). Almost
in the centre of this spot is a minute hollow, the fovea centralis,
which appears black in consequence of the thinness of the wall
allowing the dark pigment outside to be seen.

From the ora serrata a very thin layer is continued on as far as
the tips of the ciliary processes ; it is called the ciliary part of the

799

Dissection
to see the
retina.

Pigmentary
membrane.

Nervous
retina :

extent :

Fig. 293. — Objects on the
Inner Surface of the
Retina (Scemmerring).

In the centre of the ball is
the yellow spot, here repre-
sented by shading : and in its
middle the fovea centralis. To
the inner side is the optic disc
with the branching of the
artery.

thickness :

outer
surface ;

inner sur-
face presents

optic disc,

central
vessels,

yellow spot,

and central
fovea.

Ciliary
part of
retina.

800

Artery of
retina

has four
cliief
branches :

another in
foetus.

Vitreous
botly.

To obtain a
view of it,

and of its
front.

Form and
position of
vitreous :

it consists
of jelly,

with a
central
canal ;

and of the
hyaloid
niembiane :

both are
without
vessels.

Suspensory
ligament :

DISSECTION OF THE EYE.

retina, but does not consist of nervous substance. It is not visible
to the naked eye.

For a description of the structure of the retina, the student is
referred to a work dealing with microscopic anatomy.

Vessels of the retina. The central artery of the retina, accom-
panied by its veins, enters the eyeball through the optic nerve. In
the central depression of the optic papilla the artery divides into,
four primary branches,— two inner or nasal (upper and lower), and
two outer or temporal (also upper and lower). The outer branches
are the larger, and follow an arched coarse above and below the
yellow spot : all ramify in the innermost part of the nervous coat.
No vessels enter the pigmentary layer. The veins have a similar
arrangement.

In the fcetus a branch of the artery passes through the centre of
the vitreous mass to supply the lens-capsule.

Vitreous Body. This is a soft transparent mass which fills the

greater part of the space within the coats of the eyeball (fig. 288, h).

Dissection. The vitreous body may be seen on the eye on

which the retina was dissected, by taking away the retina, the iris,

and the ciliary muscle and processes.

To obtain a view of its anterior part, with the lens in situation,
an eyeball should be fixed upright, and the sclerotic and choroid
coats cut through about a quarter of an inch behind the cornea ;
then on removing carefully the cornea, the ciliary muscle and pro-
cesses, and the iris, the vitreous body will be apparent.

The vitreous body (fig. 288, h) is globular in form, and fills about
four-fifths of the ball, supporting the retina. In front it is slightly
hollowed, and receives the lens ((/), with its capsule to which it is
closely united. It is composed of a thin watery jelly, contained
in a transparent membrane named hyaloid. The jelly consists in
great part of fluid, which drains away when the vitreous body is
exposed on a fiat surface, or placed on a filter, and only a very
small amount of solid matter remains. In the central part of the
vitreous body, however, there is a canal filled with fluid [hyaloid,
canal), which extends from the optic papilla of the retina to the
back of the lens-capsule, and served in the fcEtus for the trans-
mission of the capsular branch of the central artery of the retina :
but this canal is not visible without special preparation.

The hyaloid membrane (n) is the thin, glassy, structureless layer
enclosing the vitreous body, except at the fore part where the lens
is placed. At the bottom of the ball, around the optic papilla, the
membrane is closely connected with the retina ; and it sends a
prolongation forwards to line the canal of the vitreous. In front,
the membrane becomes thicker as it approaches the ciliary processes,
and is continued into the suspensory ligament of the lens.

The vitreous mass and the hyaloid membrane are extravascular,
and receive their nutritive material from the vessels of the ciliary
processes and retina.

Suspensory ligament op the lens (Zonule of Zinn). This is
a transparent membranous structure (fig. 291, t), placed around

LENS AND ITS CAPSULE. 801

thelens-capsnle, which joins externally the hyaloid membrane opposite

the anterior termination (ora serrata) of the retina. After the extent ;

ciliary processes of the choroid coat are detached from it, dark lines

of pigment cover the surface ; and when these are washed away, is marked

plaits {ciliary processes) come into view, which are less prominent ^^' ^^^^^ '

and longer than the processes of the choroid coat, but do not

quite reach the lens-capsule internally. The two sets of prominences

are dovetailed together, — the projections of one being received into

hollows between the other ; and in the fresh state the two structures inner

are closely adherent. The membrane contains numerous stiff ^t^<^^"™®^*

radiating fibres, which internally become collected into bimdles,

and are attached to the margin, and the adjacent part of the

anterior surface of the lens-capsule. The tenseness is influenced by condition

the state of the ciliary muscle, for during its contraction the ^^*^ •

membrane is rendered lax by the drawing forwards of the ciliary

processes.

Canal of Petit. Around the margin of the lens-capsule is a narrow Canai of
space (fig. 288, o) about one-tenth of an inch across, which is situate
between the suspensory ligament and the front of the ^'itreous situation ;
humour. When the canal has been opened, and filled with air by anterior
means of a blow-pipe, it is sacculated at regular intervals, like the fa^ted^*^*^**
large intestine, by the inflation of the plaits of the anterior
l)oundar}'. The margin of the capsule of the lens boimds the space
internally.

Lens and its Capsule. The lens is situate behind the pupil of Lens of the
the eye (fig. 288, g), and brings to a focus on the retina the rays of ^^^
light entering through that aperture.

The CAPSULE is a firm and very elastic transparent case, which Capsule of
closely surrounds the lens proper. The anterior surface is free, ^ ^ *°^-
and projects towards the pupil, around which it touches the iris ; relations of
but externally the two are separated by a small interval — the surface,
posterior chamber (i) ; close to the margin of the lens it is joined
by the suspensory ligament (t). The posterior surface is received posterior
into a hollow on the front of the vitreous body, to which it is ^^ ***'
inseparably united. The circumference of the case gives attachment and cir-
to the posterior fibres of the suspensory ligament, and behind this *^^ e'^nce ,
bounds the canal of Petit (o).

The capsule is a structureless glassy membrane, much thicker is a homo-
over the front of the lens, as far out as the attachment of the membrane ;
suspensory ligament, than over the back, where it is very thin in
the centre. In the adult human eye the capsule of the lens is not
provided with blood-vessels ; but in the foetus a branch of the vessels only-
central artery of the retina supplies it.

Dissection. The lens mU be obtained by cutting across the Open cap-
thin membranous capsule in which it is enclosed.

Tlie LENS is a solid and transparent doublv convex body ; but Surfaces are

r r " 1 • 1 • cur\-ed un-

the curves are unequal on the two surfaces, the posterior being equally ;

greater than the anterior. Its margin is somewhat rounded ; and

the measurement from side to side is one -third of an inch, but dimensions

from before back about one-fifth of an inch. The density increases density ;

D.A. 3 F

DISSECTION OF THE EYE.

lines on the
surfaces ;

structure is
laminar

and fibrous.

Change in
form of lens,

in colour
and con-
sistence,
with age.

from the circumference to the centre ; for while the superficial
layers may be rubbed off with the finger, the deeper portion is firm,
and is named the nucleus.

On each surface are three lines diverging from the centre, and
reaching towards the margin ; they are the edges of planes or
" septa," where the ends of the lens-fibres meet, and are so situate
that those on one side are intermediate
in position to those on the other. In
the human eye they are not distinctly
seen, because they bifurcate repeatedly
as they extend outwards.

Structure. After the lens has been
hardened by spirit or by boiling, it may
be demonstrated to consist of a series
of layers (fig. 294) arranged one within
another, like those of an onion. The
laminae of each surface have their apices
in the centre, where the septa meet ;
they may be detached from one another
at that spot, and turned outwards to-
wards the equator of the lens. The
laminae are composed of fine parallel
fibres which run between two septa
on opposite asi3ects of the lens.

Changes in the lens with age. The form of the lens is nearly
spherical in the foetus ; but its convexity decreases with age,
particularly on the anterior surface, until it becomes flattened in
the adult.

In the fcetus it is soft, rather reddish in colour, and not quite
transparent ; in mature age it is firm and clear ; and in old age it
becomes flatter on both surfaces, denser, and of a yellowish colour.

Fig. 294. — A Representa-
tion OF THE Lamina in a
Hardened Lens.

a. The nucleus.

b. Superficial laminae.

803

CHAPTER XIT.
DISSECTION OF THE EAR.

The organ of hearing is made up of complex bodies, which are Subdivision
lodged in, and attached to the surface of, the temporal bone. It is apmratu?
commonly divided into three parts, known as the external ear, the
middle ear, and the internal ear. Of these, the last is the essential
portion, containing the terminal expansion of the auditory nerve ;
and the others are to be regarded as accessory, serving to convey to
it the vibrations produced by the sonorous undulations of the air.

External Ear. This includes the pinna or auricle and the Parts of
auditory canal : the former has been noticed at p. 569 et seq.^ and ^" ^'^^r-
the latter remains to be described.

The EXTERNAL AUDITORY CANAL (meatus auditorius externUS ; Auditory

fig. 295) is the passage which leads from the pinna towards the ^"*^^ =
tympanic cavity (a part of the middle ear), from which it is separated
in the recent state by the tympanic membrane.

Dissection. To obtain a view of this canal, a recent temporal how to
bone is to be taken, to which the cartilaginous pinna remains view^oH
attached. After the removal of the soft parts, the squamous piece
of the bone in front of the Glaserian fissure is to be sawn off ; and
the front of the meatus, except a ring at the inner end which gives
support to the thin membrana tympani, is to be cut away with a
pair of bone- forceps.

The canal is about one inch and a quarter in length, and is length ;
formed partly by bone and partly by cartilage. It is directed
forwards somewhat obliquely, and describes a slight vertical curve direction ;
with the convexity upwards. In shape it is rather flattened from size and
before Ijackwards ; and it is narrowest in the osseous portion. The shape ;
outer extremity is continuous with a hollow (concha) of the external
ear, and the inner is closed by the membrana tympani.

The cartilaginous part (a) is largest. It is about half an inch in cartiiagi-
length, and is formed chiefly by the pinna of the outer ear, which "°"^ P*^
is attached to the margin of the osseous meatus ; but at the upper is deficient
and posterior aspect the cartilage is deficient, and the tube is closed ^^^^'® '
by fibrous tissue. One or two fissures (fissures of Santorini) cross
the cartilage (p. 571).

The osseous part (6) is about three-quarters of an inch long in the osseous
adult, and is slightly constricted about the middle. Its outer P^^"^'
extremity is dilated, and the posterior edge projects farther than outer end
the anterior ; the greater portion of the margin is rough, and gives

3 F 2

804

DISSECTION OF THE EAR.

inner end. attachment to the cartilage of the pinna. The inner end is smaller,
and is marked in the dry bone, except at the upper part where
there is a notch in the osseous margin, by a groove for the insertion
of the membrane of the tympanum ; it is so sloped that the anterior
wall and the floor extend inwards beyond the hinder wall and the
roof for nearly a quarter of an inch.

Condition in In the foetus tlie osseous part of the meatus is very imperfect,
the floor and anterior wall being composed of fibrous tissue. After
birth the osseous wall is completed by an outgrowth from the ring
(tympanic bone) which supports the membrana tympani.

the foetus.

295

a. Cartilaginous
meatus.

h. Osseous poitioD.

Vertical Section of the Meatus Auditorius \nd
Tympanum (Scarpa).

part of the

c. Membrana tympani.

d. Cavity of the tympanum.

e. Eustachian tube.

Lining Lining of the meatus. A prolongation of the integument lines

of the skin. ^^^ auditory passage, and is united more closely to the osseous than
to the cartilaginous portion ; it is continued over the membrane of
the tympanum in the form of a tbin pellicle. At the entrance of
the meatus are a few hairs. In the subcutaneous tissue over the
Ceniminous cartilage of the meatus lie some ceruminous glands of a yellow-
brown colour, resembling in form and arrangement the sweat-glands
of the skin ; these secrete the ear-wax, and open on the surface by
separate orifices ; they are absent in the osseous part, and are most
abundant in that small portion of the tube which is formed by
fibrous tissue.

Vessels and nerves. The meatus receives its arteries from the
posterior auricular, the internal maxillary, and the superficial

glands.

Vessels.

BOUNDARIES OF THE TYMPANUM. 805

temporal branches of the external carotid. Its nerves are derived Nerves,
from the auric ulo-temporal branch of the fifth nerve, and enter the
auditory pa.ssage between the bone and the cartilage.

Middle Ear. The chief part of the middle ear is the tympanum Middle ear
or drum, a cavity containing air, which is interj^osed between the tym^num,
external auditory canal and the labyrinth or internal ear. The
space is traversed by a chain of small bones, with which special
muscles and ligaments are connected. It communicates in front
with the pharynx by a canal named the Eustachian tube ; and Eustachian
behind, it is prolonged into a series of excavations in the mastoid " '
part of the temporal bone — the mastoid cells. Small vessels and cells,
nerves ramify in the cavity.

Dissection. The tympanic cavity should be examined in both a Dissection
dried and a recent bone.

On the dry temporal bone, after removing most of the squamous to open it in
portion by means of a vertical cut of the saw through the root of bone,^^
the zygoma and the Glaserian fissure, the tympanum will be brought
into view by cutting away with the bone- forceps some of the upper
surface of the petrous portion, and the anterior part of the meatus
auditorius.

In the recent bone prepare the dissection as above, but without ^^'^ in ^®
doing injury to the memln-ana tympani, the chorda tympani nerve,
and the chain of bones with its muscles.

The TYMPANUM has the form of a very short cylinder, which is Tympanum:
placed obliquely, so that its end-surfaces (the inner and outer walls ^^"" *"'^
of the tympanum) are nearer to the median plane in front than
behind. The circumference of the cylinder is somewhat irregular,
and interrupted at parts ; in it a roof, a floor, and an anterior and
a posterior w^all are distinguished. The cavity measures about half dimensions,
an inch from above down and from before back. Its breadth may
be given as one-sixth of an inch ; but it is wider above and behind
than at the lower and fore parts ; and it is narrowest in the
centre, owing to the projection towards the cavity of the promontory
on the inner wall, and of the tympanic membrane externally.

The inner boundary of the tympanum (fig. 296) is formed by the Inner wall
outer wall of the osseous labyrinth, by the parts of which the con-
formation of this surface is mainly determined. Occupying the
greater part of the inner wall is a rounded eminence called the is marked by
promontory (pr) ; this becomes narrow behind, and its surface is P^'nontory
marked by two or three minute grooves which lodge the nerves of and grooves;
the tympanic plexus. Above and below the narrowed end of the
promontory is an aperture : both lead into the labyrinth.

The upper aperture (/o) is semicircular in shape, with the con- fenestra

vexity upwards, and is immed fenestra ovalis: it opens into the°^*^'^'

vestibule, and into it the inner bone (stapes) of the chain is fixed.

The lower aperture, fenestra rotunda (/r), is rather triangular in fenestra

form, and is situate within a funnel-shaped hollow : in the macerated '

bone it leads into the cochlea ; but in the recent state it is closed by

a thin membrane — the secondary membrane of the tympanum.

Arching above the fenestra ovalis on this wall is a ridge of ridge of

° ° aqueduct of

806

DISSECTION OF THE EAK.

Faliopius; bone (c/*) which marks the situation of the aqueduct of Fallopius,
and contains the facial nerve. Lastly, in front of this ridge, and
close to the roof of the fore part of the cavity, is the ending of the

and canal of canal for the tensor tym.pani muscle (ctt). The canal is separated from
the Eustachian tube (et) below it by a thin plate of bone named
the cochlear if orm process (cp); this becomes expanded on reaching the

tensor
tynipan

UTTV

Fig. 296.— Inner Wall

OF THE Left Tympanum
Natural Size.

Three Times the

pr. Promontory.

fo. Fenestra oval is.

fr. Fenestra rotunda.

py. Pyramid.

cf. Canal of the facial nerve (aque-
duct of Fallopius), cut obliquely.

cf*. Ridge formed by the canal of
the facial nerve.

am. Antrum mastoideum.

tt. Tegnien tympani.

ctt. Canal of the tensor tympani.

cp. Cochleariform process.

et. Eustachian tube.

cc. Carotid canal.

cty. Canal of tympanic nerve.

jf. Jugular fossa.

tympanic cavity, and being bent upwards, prolongs the canal

beyond the end of the Eustachian tube. In most cases the outer

wall of the tympanic portion of the canal is partly formed by

fibrous tissue. The aperture by which the tendon of the muscle

escapes is placed a little above and in front of the fenestra ovalis.

On outer The outer boundary of the cavity is formed by the membrana

membrana ^y^P^^^i (^g* 295, c), and the surrounding bone. Above and in

tympani and front of the membrane is the upper ojjening of the Glaserian fissure^

fissure!^^ which is occupied in the fresh condition by the long process of one

of the small bones (malleus) and some fibres of its anterior ligament,

MEMBRANE OF THE TYMPANUM. 807

and by the anterior tympanic vessels. Crossing the membrane
towards the upper part is the chorda tympani nerve, which issues
through a special aperture close to the Glaserian fissure.

The roof (tegmen tympani ; fig. 296, tt) is a thin plate of bone The roof is
separating the tympanic cavi4y from the cranium. It occasionally perforated,
presents one or more apertures, where the mucous lining of the
tympanum comes into contact wdth the dura mater.

The floor separates the tympanum from the jugular fossa (;/)j Floor is
and is more or less excavated by small cells, which are extensions '^®""^*^-
of the tympanic cavity, and lined by a prolongation of its mucous
membrane.

An anterior wall is present only in the lower half of the space, in front is
which it separates from the carotid canal {cc) ; in the upper half is ESlchian
the tympanic orifice of the Eustachian tube. tube.

The posterior u-all is similarly deficient in the upper half, where Behind are
there is a large aperture leading into a space called the antrum ^^J^™
mastoideum (am), from which the mastoid cells are given off. Below^ deum
this opening, but near the inner wall, and on a level w^th the
narrow part of the promontory, is the small conical projection of and
the pyramid (py). At the summit of the pyramid is a small pyramid,
orifice, from which a canal leads backwards and downwards to the
aqueduct of Fallopius : the canal lodges the stapedius muscle, with canal
Sometimes there is a slender round bar of bone connecting the ^ ^^^ '"^*
pyramid to the promontory.

Some objects that have been referred to above, viz., the mem-
brana tympani, the Eustachian tube, the mastoid cells, and the
secondary tympanic membrane, require separate notice.

The MEMBRANA TYMPANI (fig. 297) is a thin translucent disc Tympanic
between the external auditory canal and the ca^dty of the tym- "^"^'^"^^
panum. It is rather elliptical in shape, and its longest diameter, form and
which is directed from ab(J\'e down, measures about two-fifths of '
an inch. By its circumference it is attached to a groove at the
inner end of the auditory passage. In the foetus it is supported attachment ;
by a separate osseous ring — the tympanic bone (/). The mem-
brane is placed very obliquely, so that it forms an angle of about position ;
45° with both a horizontal and a sagittal plane, the outer surface
looking downwards and forwards. It is concave towards the is rather
auditory canal, being sloped inwards from the circumference to the shaped ;
centre ; and it projects into the cavity of the tympanum. The malleus
handle of the malleus (one of the ossicles ; b) is attached to
the inner side of the membrane from the centre to the upper
margin.

Structure. The membrane is formed of three strata, — external, internal, It consists
and middle. The outer one is continuous with the integuments of the meatus of acuta-
auditorius ; and the inner is derived from the mucous membrane of the ^ mucous
tympanum. The middle layer is formed of fibrous tissue, and is fixed to the and a fibrous
groove in the bone. From its centre, where it is tirmly united to the layer,
extremity of the handle of the malleus, fibres radiate towards the circum-
ference ; and near the margin, at the inner aspect, lies a band of stronger
circular fibres (fig. 297, c), which bridges across the notch at the upper part
of the tympanic bone.

808

DISSECTION OF THE EAR.

A thin part
of the
membrane
in notch.

Eustachian
tube :

osseous
part,

situation

and termi-
nation ;

cartilagi-
nous part.

Mastoid
cells :

liosition and
extent ;

open into
mastoid
antrum :

may

approacli
surface ;

develop-
ment.

Membrane
in fenestra
rotunda :

construc-
tion

Occupying the notch above-mentioned in the upper part of the
osseous margin (notch of Rivinus), there is a small piece of the
membrane which is softer and looser than the rest (memhrana
Jlaccida), being formed only by lax connective tissue between the
skin and the mucous membrane. ».

The Eustachian tube (fig, 295, e) is the channel through
which the tympanic cavity communicates with the external air. It
is about an inch and a half in length, and is directed forwards and
inwards, as well as somewhat downwards, to the pharynx. Like
the meatus auditorius, it is partly osseous and partly cartilaginous
in texture.

The osseous part is rather more than half an inch in length, and
is narrowest at its anterior end. Its course in the temporal bone is
along the angle of union of the squamous
and petrous portions, outside the passage
for the carotid artery. Anteriorly it
ends in a somewhat oval opening, with
an irregular margin, which gives attach-
ment to the cartilage.

The cartilaginous 2^art of the tube is
nearly an inch in length, and extends
from the temporal bone to the interior
of the pharynx.

Through this tube the mucous mem-
brane of the drum of the ear is con-
tinuous with that of the pharynx ; and
through it the mucus escapes.

The MASTOID CELLS are air-spaces occu-
pying the interior of the temporal bone
behind the tympanum and the external
auditory meatms. They reach downwards
into the mastoid process, and upwards for
a short distance into the adjoining region
of the squamous portion of the bone. In
front they communicate with the tym-
panum through a chamber named the
antrum mastoideum (fig. 296, am). Above the tympanic membrane
is a small recess communicating Avith the mastoid antrum, which is
called the mastoid attic. The size and extent of the cells vary
greatly in diff'erent individuals ; and in some cases they are sepa-
rated only by a very thin layer of l)one from the exterior of the
skull on the one side, and from the lateral sinus on the other. In
the infant the mastoid antrum is present, but the cells are not
formed ; the latter are developed at, or a little before, the period
of puberty.

The SECONDARY MEMBRANE OF THE TYMPANUM is placed in the
fenestra rotunda, and is rather concave towards the tympanum,
l)ut convex towards the cochlear passage which it closes.

It is formed of three strata, like the membrane on the opposite
side of the cavity, viz., an external or mucous, derived from the

Fig. 297. — Inner View of

THE AIemBRANA TyM-
PANI IN THE F(BTUS,

WITH THE Malleus
Attached.

of the

a. Membrane
tympanum.

b. Malleus.

c. Band of circular fibres
at the circumference of
the membrane.

d. Anterior, and e, pos-
terior tympanic artery.

/. Tympanic bone.

OSSICLES OF THE TYMPANUM.

809

lining of the tympanum ; an internal, continuous with that lining of three
the cochlea ; and a central layer of fibrous tissue.

Ossicles of the Tympanum (figs. 298 and 299, p. 811). Three Ossicles of
in number, they are placed in a line across the tympanic cavity, numare^*
The outer one is named malleus from its resemblance to a mallet ; three,
the next, incus, being compared to an anvil ; and the last, stapes,
from its likeness to a stirrup. For their examination the student
should be provided with some separate ossicles.

The MALLEUS (fig. 298) is the longest bone, and is twisted and Malleus has
bent. It is large at the upper part (head ; a) and small and
pointed below (handle ; c) ; and it has two processes, with a
narrowed part or neck. The head or capitulum (a) is free in the head,
cavity, is club-shaped, and at the back has a depression for articula-
tion with the next bone. The n€ck (6) is the constricted part °^^'
between the head and the processes. The handle or manubrium (c) handle,

Fig. 298. — The Three Tympanic Ossicles of the Right Side : the Central
Bone is the Malleus, the Left-hand one the Incus, and the Right-
hand ONE the Stapes.

Incus :

Malleus :

Stapes :

a. Articular surface

Head.

r malleus.

Neck.

b. Body.

Handle.

Anterior cms.

c. Short process.

Long, and

Base.

d. Long process.

Sliort process.

e. Orbicular process.

decreases in size towards the tip, and is compressed from before
backwards ; but at the extremity it is flattened from within out-
wards : to its outer mtirgin the special fibrous stratum of the
membrana tympani is connected.

The shoii process (e) springs from the root of the handle on the short
outer side, and is attached to the upper border of the tymijanic
membi-ane where it bridges across the notch of Rivinus. The long and lon^
process (processus gracilis ; d) (commonly broken off in removal) is P'^^*^^^"
during infancy a slender flattened piece of bone, which projects
from the neck of the malleus at the anterior aspect, and extends
into the Glaserian fissure ; in the adult this process is most frequently
conA'erted into a fibrous band ; and in cases where the osseous pro-
cess persists, it is joined with the surrounding bone, and cannot be
separated.

The INCUS is a flattened bone (fig. 298), and consists of a body incus:
and two processes. The body (6) is hollowed at the fore part (a) to body;

810

DISSECTION OF THE EAK.

processes,
short

and long.

Stapes ;
base ;

head

neck ; and
crura.

articulate with the malleus. The short process (c) is somewhat
conical, and j)rojects backwards nearly horizontally ; its extremity
rests against the lower and inner part of the margin bounding the
opening into the mastoid antrum. The long process (d) is almost
vertical, and descends parallel to the handle of the malleus, behind
and internal to which it lies : it diminishes towards the extremity,
where it is bent inwards, and ends in a small flattened knob — the
orbicular process (e), for articulation wuth the stapes.

The STAPES (fig. 298) has a base or wider portion, and a head
with two sides or crura, like a stirrup. The base (d) is directed
inwards, and is a thin osseous plate, convex at the upper margin
and nearly straight at the lower, corresponding with the shape of
the fenestra ovalis, into which it is received : the surface turned to
the vestibule is convex, while the opposite is excavated. The
head (a) is marked at the extremity by a superficial depression
which articulates with the orbicular process of the incus ; and it is
supported on a slightly constricted part, the neck (b). The crtira
extend horizontally from the neck to the base, and are grooved on
the surface towards the enclosed aperture ; the anterior crus (c) is
shorter and straighter than the posterior.

The bones
have two
sets of liga-
ments ;
either to
unite one to
another
by joints,

or to fix
them to the
tympanic
wall.

Ligaments
of malleus
are superior,
anterior.

and

external.

One band to
incus,

and one to
stapes.

Membrane
in aperture
of stapes.

Ligaments of the ossicles. The small bones of the tympanic cavity are
united into one chain by joints, and are farther kept in position by ligaments
fixing them to the surrounding wall.

Joints of the bones. Where the ossicles touch, they are connected together
by articulations corresponding with the joints of larger bones ; for the osseous
surfaces are covered with cartilage, are surrounded by a thin capsular liga-
ment of fibrous tissue, and lubricated by a sijuovial sac. One articulation of
this nature exists between the head of the malleus and the incus, and a second
between the orbicular process of the incus and the head of the stapes.

Union of the hones to the wall. The bones are kept in place by the reflec-
tion of the mucous membrane over them, and by the following ligaments,
three being connected with the malleus, and one each with the incus and
stapes : —

Ligaments of the malleus. The superior or suspensory ligament is a
slender band which descends from the roof of the tympanum to the head of
the malleus. The anterior ligament is the strongest of all : it passes from the
foie part of the neck of the malleus to a projection at the anterior margin of
the notch of Rivinus, and to the sides of the Glaserian fissure. A part of this
ligament entering the fissure has been described as a muscle under the name
of laxator tympani. The external ligament is short and fan-shaped : its fibres
radiate from the outer and posterior parts of the neck of the malleus to the
edge of the notch.

Th'A ligament of the incus dii\eic\iQ% the extremity of the short process of
that bone to the tympanic wall at the lower part of the orifice of the antrum
mastoideum.

The annular ligament of the stapes is composed of very short fibres, which
unite the circumference of the base of the stirrup to the margin of the
fenestra ovalis.

Special ligament of the stapes. Closing the interval between the crura of
the stapes there is a very thin membrane which is attached to the groove of
the bone. It is covered above and below by the mucous membrane.

Two Muscles of the ossicles (fig. 299). Two muscles are connected

ttirosTicies ^^^^ ^^^ chain of bones, one being attached to the malleus, the

other to the stapes.

MUSCLES OF THE OSSICLES.

811

Tensor
tympani :

insertion ;

The TENSOR TYMPANI (fig. 299, h) is the larger of the two
muscles of the tympanum, and takes the shape of its containing
tube, which must le laid open to see it completely. The muscle
arisen in front from the cartilage of the Eustachian tube and the origin
posterior extremity of the great wing of the sphenoid bone, and it
also receives fibres from tlie surface of its l)ony canal. Posteriorly
it ends in a tendon which is reflected over the end of the cochleari-
forni process, and is inserted into
the inner border of the handle
of the malleus near its base.

Action. The muscle draws in-
wards the handle of the malleus
towards the inner wall of the
tympanic cavity, and tightens
the meml)rane of the tympanum ;
and as the long process of the
incus is moved inwards with the
malleus, the base of the stapes
will be pressed into the fenestra
ovalis.

The STAPEDIUS (fig. 299, i) is
lodged in the canal hollowed
ill the interior of the pyramid.
Arising inside the tube, the
muscle ends in a small tendon,
which issuer at the apex of the
pyramid, and is inserted into the
back of the head of the stapes.

Action. By directing the neck
of the stapes backwards, the
muscle raises the fore j^art of the
base out of the fenestra ovalis,
diminishing the pressure on the
fluid in the vestibule ; and sup-
posing it to contract simul-
taneously with the tensor, it
would prevent the sudden jar of
the stapes on that fluid.

Mucous MEMBRANE OF THE

TYMPANUM. The mucous lining

of the tympanic cavity adheres closely to the wall ; it is continuous
with that of the pharynx through the Eustachian tube, and is
prolonged into the mastoid cells through the antrum.

It forms part of the meml>rana tympani, and of the secondary
membrane in the fenestra rotunda ; it is reflected also over the
chain of bones, the muscles, ligaments, and chorda tympani nerve.
In the tympanum the membrane is thin, not very vascular, and
secretes a watery fluid ; but in the lower end of the Eustachian
tul>e it is thick and more vascular, and is provided with numerous
glands.

Stai>edius

contained in
pyramid ;

Fig. 299. — Plan of the Ossicles of
THE Tympanum in Position,
WITH THEIR Muscles.

a. Cavity of the tympanum.

b. Membrana tympani.

c. Eustachian tube.

d. Malleus.

e. Incus.
/. Stapes.

g. Laxator tympani muscle, some-
times described.
h. Tensor tympani.
i. Stapedius.

Lining of
tympartiim ;

arrange-
ment in
cavity ;

in Eusta-
chian tube.

812

DISSECTION OF THE EAE.

Arteries are
branches of
carotids.

From

internal

maxillary,

middle*
meniugeal,

posterior
auricular,

ascending
pharyngeal.

internal
carotid.

Nerves from

several

sources.

Dissection
to prepare
the nerves ;

outside

tympanic

cavity.

and inside
cavity.

Tympanic
nerve

Blood-vessels. The arteries of the tympanum are furnishec |
from the following branches of the external carotid, viz., interna. ;
maxillary, middle meningeal, posterior auricular, and ascending
pharyngeal; and some offsets come from the internal carotid in th€
temporal bone. The veins join the pterygoid plexus, and the large'
meningeal and pharyngeal Ijranches.

The internal maxillary artery supplies an anterior tympanic
branch (fig. 297, c?), which enters the cavity through the Glaserian
fissure, and gives an offset to the membrane of the tympanum.

The middle meningeal artery also sends fine twigs to the upper
part of the tympanum through small apertures in the roof of the
cavity.

The stylo-mastoid branch of the posterior auricular artery,
entering the lower end of the aqueduct of Fallopius, gives twigs
to the back of the cavity, and the mastoid cells. One of this set,
posterior tympanic (fig. 297, e), anastomoses with the tympanic
branch of the internal maxillary artery, and forms a circle around
the membrana tympani, from which offsets are directed inwards.

Other branches from the ascending pharyngeal, or from the
inferior palatine artery, enter the fore part of the space by the
Eustachian tube.

One or two minute branches of the internal carotid artery reach
the anterior wall of the tympanum from the carotid canal.

Nerves. The lining membrane of the tympanum is supplied
from the plexus (tympanic) between Jacobson's and the sympathetic
nerve ; but the muscles derive their nerves from other sources.
Crossing the cavity is the chorda tympani branch of the facial
nerve.

Dissection (fig. 300). The preparation of the tympanic plexus
will require a separate fresh temporal bone, which has been
softened in diluted hydrochloric acid, and in which the nerves
have been hardened afterwards in spirit.

The origin of Jacobson's nerve from the glosso-pharyngeal is first
to be sought close to the skull ; and the fine auricular branch of
the pneumo-gastric may be looked for at the same time (p. 633).
Supposing the nerve to be found, the student should place the
scalpel on the outer side of the Eustachian tube, and carry it back-
wards through the vaginal and styloid j^rocesses of the temporal
bone, so as to take away the outer part of the tympanum, but
without opening the lower end of the aqueduct of Fallopius.

After the tympanum has been laid open, Jacobson's nerve is to
be followed in its canal ; and the branches in the grooves on the
surface of the promontory are to be pursued ; — two of these, arching
forwards, pass to the sympathetic on the carotid artery and to the
Eustachian tube ; and two others are directed upwards beneath the
tensor tympani muscle.

The course of the chorda tympani nerve can be seen on the
preparation used for the muscles.

The tympanic branch of the glosso-pharyngeal nerve
(fig. 300,^ ; nerve of Jacobson) enters a special aperture in the

NERVES OF THE TYMPANUM.

813

iporal bone (fig. 296, dy), to reacli the inner wall of the tym- supplies
!um. In tliis cavity the nerve supplies filaments to the lining mem^ne,
jubrane, to the fenestra rotunda and fenestra ovalis, and to the
tachian tube; and it terminates in the three under-mentioned and other
nches, which are contained in grooves on the promontory, and ^?^°*'^^^'
meet this nerve with others.

Branches.

One branch is arched forwards and downwards, and o"« ^ sy™*

pathetic,

FiQ. 300. — Jacobson's Nerve in the Tympanum (Breschkt).

a. Carotid artery.

b. Tensor tympani muscle.

c. Inferior maxillary trunk of the
fifth nerve.

d. Otic ganglion.

Nerves :
1. Petrosal ganglion of the glosso-
pharyngeal.

2. Nerve of Jacobson.

3. Sympathetic on the carotid.

4. Small superficial petrosal nerve.

5. Small deep petrosal nerve.

6. Branch to Eustachian tube.

7. Facial nerve.

8. Chorda tympani.

9. Nerve of the otic ganglion to
the tensor tympani muscle.

enters the carotid canal to communicate with the sympathetic (*)
on the artery.

The second (') is the small deep petrosal nerve, which is directed small deep
forwards through a canal beneath the cochleariform process, to join nerv^
the carotid plexus of the sympathetic (sometimes also the large
superficial petrosal nerve) in the foramen lacerum.

And the third (^) has the following course : — It ascends in front and small
of the fenestra ovalis, and near the gangliform enlargement on the petro^T*^
facial nerve, to which it is connected by filaments. Beyond the
union with the facial, the nerve is named small superficial petrosal,
and is continued forwards through the substance of the temporal

814

DISSECTION OF THE EAR.

to otic
ganglion.

Nerves for
the muscles.

Chorda
tympaiii
crosses
cavity.

Branch of
vagus to the
outer ear.

Labyrinth
formed of
osseous and
mem-
branous
parts.

Constitu-
ents of the
osseous
part.

Vestibule :

dissection
to see it ;

form and

dimensions

apertures
before and
behind :

in outer
wall;

bone, to end in the otic ganglion, and eventually, in great part, tc^,
enter the auriculo-temporal nerve and be distributed to the parotid!
gland.

Nerves to Muscles. The tensor tympani muscle is supplied by»
a branch from the otic ganglion (fig. 300, s) ; and the stapedius*
receives an offshoot from the facial trunk.

The CHORDA TYMPANI (fig. 300, 8) is a branch of the facial nerve.
Entering the cavity behind, it crosses the membrana tympani, lying
on the inner side of the handle of the malleus, and issues from the
space by an aperture internal to the Glaserian fissure ; it joins the
lingual nerve, and its farther course to the tongue is described!
at p. 688.

The AURICULAR BRANCH OP THE VAGUS, though not a nerve of the
tympanum, may now be traced in the softened bone. Arising in
the jugular fossa (p. 633), the nerve enters the special canal, and
crosses through the substance of the temporal bone to the back of
the ear.

INTERNAL EAR OR LABYRINTH.

The inner portion of the organ of hearing consists of a complex
chamber surrounded by dense bone, within which are included sacs
containing fluid, for the terminal expansion of the auditory nerve.

The Osseous Labyrinth comprises the vestibule, the semi-
circular canals, and the cochlea : in the macerated bone these
communicate externally with the tympanum, and internally through
the meatus auditorius internus with the cranial cavity.

The vestibule (fig. 301), or the central cavity of the osseous
labyrinth, is placed behind the cochlea, but in front of the semi-
circular canals.

Dissection. This space may be seen on the dry bone which has
been used for the preparation of the tympanum. The bone is to
be sawn through vertically close to the inner wall of the tympanum,
so as to lay bare the fenestra ovalis leading into the vestibule. TBy
enlarging the fenestra ovalis a very little in a direction upwards and
forwards, the vestibular space will appear ; and the end of the
superior semicircular canal will be opened.

Other views of the cavity may be obtained by sections of the
temporal bone in different directions, according to the opportunities
and skill of the dissector.

The vestibular space (fig. 301) is ovoidal in form, and the ex-
tremities are directed forwards and backwards. The larger end is
turned back, and the under-part or floor is more narrowed than the
upper part or roof. It measures about one-fifth of an inch in length ;
but it is narrower from without inwards. The following objects
are to be noted on the boundaries of the space.

In front, close to the outer wall, is a large aperture (g) leading
into the cochlea ; and behind are five round openings of the three
semicircular canals (d, e, f).

The outer wall corresponds with the tympanum, and in it is the
aperture of the fenestra ovalis. On the inner wall, nearer the front

THE OSSEOUS LABYRINTH.

than the back of the cavity, is a vertical ridge or crest (h). In crest on
front of the crest is a circular depression, fovea hemispherica (a), with^fosV
which is pierced by minute apertures for nerves and vessels, and *" front,
corresponds with the bottom of the internal auditory meatus.
Behind the crest of bone, near the common opening of two of the
semicircular canals, is the aperture of the aqueduct of the vestibule (c), and aque-
a narrow canal which ends on the posterior surface of the petrous <i"ct behind;
portion of the temporal bone : it contains a process of the mem-
branous labyrinth called the ductus endolymphaticus, and a small
vein.

Thereof is occupied by a slight transversely oval depression, fossa in roof.

Fig. 301. — View of the Vestibule of the Right Side, obtainkd bycdtting
AWAY the Outer Boundaky in a Fcetus, enlarged Three Times.

a. Fovea hemispherica.

b. Crest of the vestibule.

c. Aperture of aqueduct of the
vestibule.

d. Common opening of two semi-
circular canals.

e. Upper semicircular canal, partly
laid open,

/. Horizontal semicircular canal,
partly opened.

g. Opening of the scala vestibuli of
the cochlea.

fovea hemielliptic<i ; this is separated from the fovea hemispherica by
a prolongation of the crest (6) on the inner wall.

The SEMICIRCULAR CANALS (fig. 302) are three OSSeoiLS tubes, Three semi-

which are situate behind the vestibule, and are named from their ^SsT
form.

Dissection. These small canals will be brought into view by preparation
the removal of the surrounding bone by means of a file or bone
forceps. Two may be seen opening near the aperture made in the
vestibule, and may be followed thence ; but the third is altogether
towards the posterior aspect of the petrous portion of the temporal
bone.

The carmls are unequal in length, and each forms more than half length ;
an ellipse. They communicate at each end with the vestibule, but

816

DISSECTION OF TRE EAR.

termination
by Ave
openings ;
one end
dilated ;

form and
size ;

they are
named

superior
vertical,

posterior
vertical,

Fibrous
membrane
lines the
labyrinth,

and contains
a fluid.

Coclilea :

dissection
for it in dry

the contiguous ends of two are blended together so as to give onl
five openings into that cavity. Each is marked by one dilated'
extremity, called the ampulla. When a^ube is cut across it is not
circular, but is compressed laterally, and measures about gV^^ ^^'
an inch, though in the ampulla the size is as large again.

From a difference in the direction of the tubes, they have been
named superior vertical, posterior vertical, and horizontal.

The superior vertical canal (a) crosses the upper border of the
petrous part of the temporal bone, and forms a projection on the

surface. • Its outer end is
marked by the ampulla, while
the inner is joined with the
following.

The posterior vertical canal (b)
is directed backwards from its
junction with the preceding
towards the posterior surface of
the temporal bone ; it is the
longest of all, and has its
ampulla at the lower end.

The horizontal canal (c) has
separate apertures, and is the
shortest of the three. Deeper
in position than the superior
vertical, it lies in the substance
of the bone nearly on a level
with the fenestra ovalis ; its
dilated end is at the outer
side close above that aperture.

Lining membrane of the osseous
labyrinth. A thin fibrous peri-
osteal membrane lines the vesti-
bule and the semicircular canals,
and is continuous with the
fibrous process in the aqueduct
of the vestibule. On the outer
wall of the cavity it stretches
over the fenestra ovalis ; and in front it is prolonged into the cochlea
through the aperture of the scali vestibuli (fig. 301, g). The space
between the periosteum and the membranous labyrinth is occupied
by a thin fluid — liquor Cotunnii or perilymph, which also fills the
scalae of the cochlea.

Cochlea. This part of the osseous labyrinth has a position
anterior to the vestibule, and has received its name from its
resemblance to a spiral shell.

Dissection. To obtain a view of the cochlea it will be needful to
cut or file away the bone between the promontory of the tympanum
and the internal auditory canal on the preparation before used for
displaying the vestil)ule ; or this section may be made on another
temporal bone in which the semicircular canals are not laid bare.

Fig. 302. — Representation of the
Semicircular Canals, enlarged.

and

of the two

a. Upper vertical.

b. Posterior vertical,

c. Horizontal canal.

d. Common opening
vertical canals.

e. Part of the vestibular cavity.

/. Opening of the aqueduct of the
vestibule.

THE OSSEOUS COCHLEA.

817

For the like dissection in the recent state, a softened bone should
be used.

The cochlea (fig. 303) is conical in fomi, and is placed almost
horizontally in front of the vestibular space. The base of this body
is turned to the meatus auditorius internus, and is perforated by
small apertures ; while the apex is directed to the inner wall of the
tympanum, opposite the canal for the tensor muscle. Its length is
about a quarter of an inch, and its width at the base is about the
same. Resembling a spiral shell, the cochlea consists of a tube
wound round a central part or axis ; but it differs from the shell in
having its tube subdivided by a partition.

The axis or modiolus (fig. 303, a) is the central stem which
supports the windings of the spiral tube. Conical in shape, its size

and recent
bone ;

form and
situation ;

resembles a
snail-sheU
in some
respects.

Central
pillar or
axis

7/L

Fig. 303. — Section through the Cochlea (Breschkt).

a. Bi"anches of the auditory nerve,
contained in the canals of the axis.

b. Enlarged upper end of the axis.

c. Septum of the cochlea.
c. Membrane of Reissner.

f. Hiatus or helicotrema.
s.t. Scala tympani.
s.v. Scala vestibuli.
s.m. Scala media or canal of the
cochlea.

diminishes rapidly towards the last half turn of the tube, but it is conical,
enlarges at the tip of the cochlea, forming a second small cone (6),
which is bent. The axis is perforated by canals as far as the con- and porous
tracted part of the last half-turn, and the central one is larger than
the others ; these transmit vessels and nerves in the fresh state.

The spiral tube forms two turns and a half round the stem, and a spiral
terminates above in a closed extremity named the cupola. When at one'enr'
measured along the outer side, it is about one and a half inch long, forms 2^
Its diameter at the beginning is about one-tenth of an inch, but it
diminishes gradually to half that size towards the opposite end.

Of the coils that the tube makes, the first is much the largest ;
this projects towards the tympanum, and gives rise to the eminence
of the promontory on the inner wall of that cavity. The second
turn is included within the first coil. The last half-turn bends
sharply round, and presents a free margin (6) — the edge of the axis.

D.A. 3 G

measure-
ment ;

coils.

818

DISSECTION OF THE BAR.

Tube
divided
into two.

Septum
bony and
membra-
nous.

Os.seous
part

In the recent bone the tube is divided into two main passage?
(scalse) by the septum (fig. 303). In the dry bone a remnant oi|
this partition is seen in the form of a thin osseous plate — lamina^
spiralis, 2:>rojecting from the axis.

Septum of the spiral tube (fig. 304). The partition in th^
recent state dividing the tube of the cochlea into two passages
consists of an osseous and a membranous portion : —

The osseous part (^), formed by the lamina spiralis, extends abouij
half-way across the tube. Inferiorly it begins in the vestibule

304. — A Diagram op a Section of the Tube of the Cochlea,

ENLARGED (MODIFIED FROM HeNLe).

SV. Scala vestibuli.
ST. Scala tympani.
CC. Canal of the cochlea.

1. Membrane of Reissner.

2. Cochlear branch of the auditory
nerve.

3. Lamina spiralis ossea.

4. Ligamentum spirale.

a. Limbus laminae spiralis.

b. Sulcus spiralis.

c. Tympanic lip of the sulcus
spiralis.

mb. Merabrana basilaiis.
The remaining letters refer to
parts of the organ of Corti.

ends above
in a point

over an
aperture.

Lamina
spiralis

has limbus
on upper
surface.

where it is wide, and is attached to the outer wall so as to shut out
the fenestra rotunda from that cavity ; and diminishing in size, it
ends above in a point — the hamuhis, opposite the last half-turn_^of
the cochlea. Between the hamulus and the axis is a sf)ace, which
is converted by the membranous piece of the septum into a foramen
{hiatus, helicotrema ; fig. 303,/), and allows the intercommunication
of the two chief passages of the cochlear tube.

The lamina spiralis is formed by two plates of bone, which
enclose canals for vessels and nerves, and are separated farthest
from each other at the axis. The upper surface of the lamina is
covered in the outer fourth of its extent by a border or limbus of

THE COCHLEAR PASSAGES. 819

fibrous structure (a), which ends in wedge-shaped teeth near the
margin of the bony plate.

Between the teeth and the underlying bone is a channel (6) spiral
which is called sulcus spiralis : its edges are named vestibular (a) g'"°*'^^-
and tympanic (c).

The memhranous part of the septum {inembrana basilaris ; ^lem-
fig. 304, m b) reaches from the lower (tympanic) jedge (c) of the parts^"^
lamina spiralis to the outer wall of the cochlear tube, where it is includes
fixed l)y a fibrous band — ligameiitum spirale ("*). Its width varies, ^e^brane
for near the base of the cochlea it forms half of the partition across and spiral
the tube ; but at the apex, where the lamina spiralis is wanting, it iiga^^nt.
constructs the septum altogether.

SCALiE OF THE COCHLEA (fig. 303). The tube of the cochlea is Scalae of

divided by the septum into two primary passages, of which one is JJ^*?*^^^®**
the scala tympani (s t), and the other scala vestibuli (s v) ; but the
latter is rendered smaller hj a third canal being cut oflF from it by
membrane.

The passages are placed one above another, the scala vestibuli position ;
(s v) being nearest the apex of the cochlea. Above, they com- extent;
municate through the aperture named helicotrema (/). -^^l^^j ioined
they end differently, as the names express: — the scala vestibuli above ;
opens into the front of the vestibule (fig. 301, g) ; but the scala separate
tympani is shut out from the vestibular cavity by the lamina spiralis below
of the septum cochleae, and is closed below by the membrane of the
fenestra rotunda, though in the dry bone it opens into the
tympanum.

Each has certain peculiarities. The vestibular scala extends into they differ
the apex of the cochlea ; while the tympanic scala is largest near >» extent

»> X «» ftnci S17G '

the base. Connected with the last is the small aqueduct of the
cochlea, which begins at an opening close to the lower end of the opening in
scala, and ends at the lower border of the petrous portion of the lower;
temporal bone : it transmits a small vein from the cochlea.

The scalse are clothed with a thin fibrous membrane, continuous nning
with that in the vestibule : in the scala tympani it helps to close membrane,
the fenestra rotunda, forming the inner layer of the secondary
membrane of the tympanum, and joins the fibrous process in the and con-
aqueduct of the cochlea. The perilymph fills both scalae. tents.

Caxal of the cochlea. In the upper division of the cochlear Cochlear
tube a fine membrane (fig. 304,^) extends obliquely across from the ^"*^*s
upper surface of the lamina spiralis, at the inner border of the between
limbus, to the outer wall of the cavity a little above the spiral me^mbrane
ligament. This is called the membrane of Reissner, and separates a ^^^j mem-
small cavity named the canal or duct of the cochlea (c c) from the scala braiie of
vestibuli (s v). The canal thus formed extends from apex to base of
the cochlea, and contains a fluid — endolymph. Above, it reaches into .
the cupola and is closed. Below, it is connected by a very small tube duct from
{canalis reuniens ; fig. 305, c) with the saccule in the vestibule. ^Jow^
Within the canal of the cochlea, resting on the basilar membrane, is
the complicated structure known as the organ of Corti (fig. 304), in qJ"^' of
which the cochlear branches of the auditory nerve end. Corti.

3g 2

820

The mem-
branous
labyiinth
consists of
utricle,
saccule,
semicircular
canals, and
cochlear
canal.

DISSECTION OF THE EAR.

Lodged in the vestibule

Utricle :

situation

and form ;

macula,

and otoliths.

Semicircular
canals :
not free in
cavity ;

have
ampullae,

which
receive the
nerves.

Membranous Labyrinth (fig. 305).
are two membranous sacs, the utricle and saccule from the formen
of which tubular offsets are continued into the semicircular canals.
These, together with the canal of the cochlea and the organ of Corti,
which have been referred to above, make up the membranous -f
labyrinth. The sacs and their prolongations are immersed in the
perilymph, and are themselves filled with a fluid called the
endolymph. In them the ramifications of the auditory nerve are
distributed.

Dissection. The delicate internal sacs of the ear, with their

nerv^es, cannot be dissected
except on a temporal bone
which has been softened in
acid, and afterwards put in
spirit. The previous instruc-
tions for the dissection of the
osseous labyrinth will guide
the student to the situation
of the membranous structures
within it, but the surrounding
softened material must be re-
moved with great care.

The UTRICLE (fig. 305, d),
or the common sinus, is the
larger of the two sacs, and is
situate at the posterior and
upper part of the vestibule,
of)posite the fovea hemiellip-
tica in the roof. It is trans-
versely oval in form, and con-
nected with it posteriorly are
three looped tubes, which
occupy the semicircular canals.
At the fore part of the sac is
a thickened and more opaque
part of its wall — macula acus-
tica (e), where the nerves
enter ; and opposite this, in

Fig. 305. — Petrous Bone partly re-
moved TO SHOW THE MEMBRANOUS

Labyrinth of the Left Side in

PLACE (BrBSCHET).

a. Saccule.

b. Its macula.

c. Ductus reuniens.

d. Utricle.

e. Its macula.

/. AmpuUary enlargement of the ex-
ternal semicircular canal, g.

calcareous granules or otoliths.
The MEMBRANOUS SEMICIRCULAR CANALS (g) are about one-third
of the diameter of the osseous tubes, along the convex border of
which they lie, being closely attached to the periosteal lining of the
bony wall ; and the remaining space is filled by perilymph. Each
is marked at one end by an ampulla, which is relatively of large
size and nearly fills the osseous case. Two are blended at one end,
like the canals they occupy, so that they communicate with the
utricle by five openings. At each ampullary enlargement there is
a transverse projection {crista acustica) into the anterior of the tube ;
and at that spot a branch of the auditory nerve enters the wall.

THE AUDITORY NERVE.

821

The SACCCLE (fig. 305, a) is a smaller and rounder cyst than the
utricle, in front of which it is placed, in the hollow of the fovea
liemispherica. It communicates with the utricle through the ductus
endolymphaticus, and is continuous Ijelow by a short and small
passage (canalis reuniens ; c) with the canal of the cochlea. Like
the other sac, it possesses a macula {h) and otoliths where the
nerves enter.

The ductus endolymphaticus is a fine tubular offset of the mem-
branous labyrinth, which occupies the aqueduct of the vestibule,
and ends in a dilated blind extremity (saccus eudolymphiUicus),
embedded in the dura mater
on the posterior surface of the
petrous portion of the temporal
bone. In the vestibule the duct
divides into two small branches,
one of which joins the saccule,
and the other the utricle.

For an account of the minute
structure of the membranous
labyrinth, reference must be
made to a work on microscopic
anatomy.

Nerve of the Labyrinth. A
special nerve, the eighth cranial
or auditory, is distrilnited to the
labyrinth. Entering the internal
auditory meatus with the facial
nerve, it divides into an upper
smaller, and a lower larger piece,
each of which again subdivides
into three branches. At the
bottom of the meatus, the upper
piece is marked by a ganglionic
swelling — the intumescentia gan-
glioformis of Scarpa.

The upper divisio7i of the nerve
sends its branches to the macula
of the utricle (fig. 306, c), to the
ampulla of the superior vertical semicircular canal
ampulla of the external semicircular canal.

From the loicer division of the nerve proceed an offset to the
saccule (a) and a slender branch to the ampulla of the posterior
vertical semicircular canal (6) ; but the greater part is destined for
the cochlea.

Each of the branches of the auditory nerve l)reaks up into a
bundle of filaments, which pass through minute apertures of the
lamina cribrosa, to reach their special part of the membranous
labyrinth. The nerves of the semicircular canals enter the ampullae
on their outer flattened side, and end in the crista acustica ; while
those of the sacs end in the respective maculae.

Saccule
has com-
munications
with utricle
and cochlea;
macula and
otoliths.

Endo-
lymphatic
duct
and sac ;

Fig. 306. — Distribltion of Nerves
TO THE Membranous Labyrinth
(Brkschet).

a. Nerve to the saccule.

b. Nerve entering the arapullary
enlargement on the posterior serai-
circular canal.

c. Nerve entering the utricle. The
nerve to the cochlea is not repre-
sented.

upper has

ganglion.

and to the

and supplies
utricle,
superior and
external
canals ;

lower gives
branches to
saccule,
posterit)r
canal, and
cochlea ;
ending of
vestibular
branches ;

822

DISSECTION OF THE EAR.

cochlear
nerve has a
spiral^
ganglion,

and ends in
organ of
Corti.

Vessels of
labyrinth.

Auditory
artery from
basilar,
has a

vestibular,

and a

cochlear

branch.

Veins to
petrosal
sinu.ses and
internal
jugular.

The cochlear nerves traverse the canals of the modiolus, and:
bend outwards in the passages of the lamina spiralis (fig. 304, -).
As they enter the latter, the)'' join a ganglion (ganglion spirale)
which occupies a winding canal at the junction of the lamina
spiralis with the modiolus ; and from this they are continued as il
fine branches, forming a close plexus, to the organ of Corti.

Blood Vessels. The membranes of the laljyrinth are supplied
hy an artery which enters the internal auditory meatus with the
auditory nerve. The veins are more numerous.

The INTERNAL AUDITORY ARTERY arises from the basilar trunk
within the skull, and divides in the internal auditory meatus
into two branches, — one for the vestibule, and the other for the
cochlea.

The vestibular artery subdivides into small offsets which enter the
cavity with the branches of the auditory nerve, and ramify over the
sacs and the semicircular canals.

The cochlear branch breaks up into numerous fine twigs which
enter the modiolus and the canals in the lamina spiralis. Off"sets
supply the nerve and the parts in the neighbourhood of the limbus
laminae spiralis, and others ramify in the periosteal lining of the
scalse ; but there are no vessels in the outer part of the membrana
basilaris.

Veins. The internal auditory vein accompanies the artery, and
ends in the inferior petrosal sinus in the base of the skull. The
vein of the aqueduct of the cochlea joins the internal jugular ; and the
vein of the aqueduct of the vestibule opens into the superior petrosal
sinus.

INDEX.

The letter (o) refers to the origin, (c) to the course, and (d) to the distribution of a nerve
or vessel which is described in difiFerent pages.

Abdomen, cavity of, 296.

surface of, 260.
Abdominal aorta, 362.
hernia, 285.
regions, 297.
ring, external, 266, 288.
internal, 275, 288.
Abducent nerve. See Nerve.
Abductor. See Muscle.
Aberrant ducts of liver, 350.
Accessorius. See Muscle.
Accessory nerve of the obturator, 163.
pudic artery. See Artery,
spleens, 343.
thyroid glands, 587.
Acromial cutaneous nerves, 31.
Acromio-clavicular articulation, 37.

thoracic artery. See Artery.
Adductor. See Muscle.
Agger nasi, 671.

Agminated glands. See Glands.
Air-cells of the lung, 478.
Ala cinerea, 783.
of nose, 665.
Alar ligaments of the knee, 216.

thoracic artery. See Artery.
Alveolar plexus. See Plexus.
Ampullae, of the semicircular canals, 816.

membranous, 820.
Amygdaloid lobe of cerebellum, 778.
nucleus, 762.
tubercle, 762.
Anal canal, 387.

fascia. /See Fascia.
Anastomotic artery. See Artery.
Anconeus muscle, 87.
Angular artery. See Artery,
convolution, 751.
vein. See Vein.
Ankle-joint, 222.
Annectant convolutions, 751.
Annular ligament. See Ligament.
Annulus ovalis, s. Vieussenii, 458.
Ansa hypoglossi, 599, 602.

Vieussenii, 638.
Anterior commissure, 769.
Antihelix, 569.
Antitragus, 569.

muscle of. See Muscle.

Antrum mastoideum, 807.
pylori, 339.

of superior maxilla, 670.
Anus, 237.
Aorta, 465.

abdominal, 362.
arch of, 466.
ascending, 465.
descending thoracic, 480.
Aortic opening in diaphragm, 361.
orifice of heart, 473.
plexus. See Plexus,
sinus, 466.
Aperture, of the aorta, 473.

for the femoral artery, 167.
of the larynx, 660.
of the pulmonary artery, 461.
of the thorax, 639.
Apertures, of the cavse, 459.
of the heart, 464.
of the pulmonary veins, 462.
Aponeurosis, epicranial, 502.

of external oblique, 265.
over femoral artery, 154.
intercostal, anterior, 438.
posterior, 488.
of internal oblique, 269.
lumbar, 272, 521.
palmar, 70.
perineal, deep, 248.
of the pharynx, 655.
of the soft palate, 662.
temporal, 506.
over tibialis posticus, 194.
of the transversalis muscle,
272.
vertebral, 524,
Appendages of the eye, 31.
Appendices epiploicae, 301, 312.
Appendix auriculae, 455.

vermiformis, 302, 324.
Aqueduct of the coclilea, 819.
of Fallopius, 806.
of Sylvius, 773.
of the vestibiile, 815.
Aqueous humour, 798.
Arachnoid membrane of the brain, 716.
of the cord, 540.
Arantii, corpus, 462.

824

INDEX.

Arbor yitse cerebelli, 781.
uterinus, 421.
Arch, of aorta, 466.

crural or femoral, deep, 145.

superficial, 143
of diaphragm, 360.
palmar, deep, 80.

superficial, 71.
plantar, 207.
of soft palate, 661.
Arciform fibres, 733, 736.

nuclei, 738.
Areola of the mamma, 14.
Arm, dissection of, 39.
Arnold's ganglion, 681.

nerve. See Nerve.
Arteria comes nervi ischiadici, 118. I

phrenici, 365, 441, 470
pancreatica magna, 332.
thyroidea ima, 587.
Arteries receptaculi, 518.
Arterial duct, 465.
Artery or Arteries : —

acromio-thoracic, 23.
anastomotic of brachial, 48.
of femoral, 154.
of profunda, 166.
of sciatic, 119.
angular, 559.
aorta, abdominal, 320.

thoracic, 480.
articular of knee, azygos, 129.
inferior, 128.
. , superior, 127.

auricular, anterior, 606.
deep, 614.
posterior, 503, 606.
auditory, 720, 822.
axillary, 22.
basilar, 719.
brachial, 46.
brachio-cephalic, 467.
bronchial, 480, 481.
buccal, 615.
of bulb, 251, 417.
calcaneal, internal, 203.
capsular, inferior, 358, 364.
middle, 358, 364.
superior, 358, 365.
carotid, common, left, 468.
right, 699.
external, 602.
internal, 518, 626, 627, 682,

carpal, radial, anterior, 63.
posterior, 90.
ulnar, anterior, 66.
posterior, 66.
central of retina, 646, 800.
cerebellar, anterior, 720.
inferior, 718.
superior, 720.
cerebral, anterior, 722.
middle, 723.
posterior, 719, 720.
cervical, ascending, 594.
deep, 532, 595.
superficial, 522.

Artery or Arteries : —

cervical, transverse, 9, 522.
choroid of brain, 721, 724, 764.
ciliary, anterior, 647, 798 '
long, 646, 798.
posterior, 646, 797.
circumflex, anterior, 24, 34.
external, 159.
iliac, deep, 284.

superficial, 138,
264.
internal, 123, 166.
posterior, 24, 34.
coccygeal, 118.
cochlear, 822.
coeliac, 331.
cohc, left, 317.

middle, 316.
right, 316.
communicating, anterior, 722.
plantar, 184.
posterior, 722.
of posterior tibial,
195.
coronary, of heart, 455.
of lips, 559.
of stomach, 332.
of corpus cavernosum, 251, 416
cremasteric, 277, 284.
crico-thyroid, 604, 697.
cystic, 333.

deep femoral, 149, 164.
deferential, 277.
dental, anterior, 653.

inferior, 614, 618.
posterior, 615.
diaphragmatic, 365.
digital, of foot, 202, 209, 210

of hand, 71, 80.
dorsal, of clitoris, 259.
of foot, 182. 210.
of index finger, 91.
of penis, 251, 253.
scapular, 24.
of thumb, 91.
of tongue, 623.
epigastric, deep, 284.

superficial, 138, 264.
superior, 283.
ethmoidal, anterior, 648.
posterior, 647.
facial, 556, 605.

transverse, 559.
femoral, 148, 154.

deep, 149, 164.
frontal, 503, 648.
gastric, 332.
gastro-duodenal, 332.

epiploic, left, 332.
, , , right, 333.

gluteal, 116, 398.
hemorrhoidal, inferior, 242.
middle, 398.
superior, 318, 400.
hepatic, 332.
hyoid of lingual, 623.
of thyroid, 604.
hypogastric, 396.

INDEX.

825

Artery or Arteries : —

iliac, common, 365.
external, 366.
internal, 396.
ileo-colic, 316.
ilio-lumbar, 396.
incisor, 618.
infraorbital, 653.
infrascapular, 24, 31.
innominate, 467.

intercostal, anterior, 439, 441, 538.
aortic, anterior

branches, 283, 439, 482.
aortic, posterior

branches, 482, 532.
superior, 439, 483, 595.
interosseous, of foot, 184.

of forearm, 66.

anterior, 68.
posterior, 90.
of hand, 80, 91.
intestinal, 315.
intraspinal, 549.
labial, inferior, 559.
lachrj-mal, 569, 647.
laryngeal, inferior, 594, 697.
superior, 604, 697.
lingual, 623.
lumbar, 283, 374.

anterior branches, 283.
posterior branches, 533.
malleolar, 182, 195. !

mammary, external, 24.

internal, 283, 440, 470,
594.
masseteric, 615.
maxillary, internal, 614, 677.
median, 69.
mediastinal, 441, 482.
medullary, of femur, 166.
of fibula, 196.
of humerus, 48.
of radius, 69.
of tibia, 195.
of ulna, 69.
meningeal, anterior, 514.

of ascending pharyngeal,
514.
large, 514.
middle, 514, 614.
of occipital, 514, 604.
posterior, 514, 718.
small, 514, 615.
of vertebral, 514.
mental, 618.

mesenteric, inferior, 317.
superior, 314.
metacarpal, radial, 91.
ulnar, 66.
metatarsal, 184.
musculo-phrenic, 365, 441.
mylo-hyoid, 614.
nasal, external, 648.
internal, 648.
of internal maxillary, 678.
lateral, 559.
of septum nasi, 678.
naso-palatine, 673, 678.

Artery or Arteries : —

obturator, 168, 284, 398.
occipital, 503, 532, 605.
oesophageal, 332, 482.
ophthalmic, 518, 646.
orbital (of temporal), 606.
ovarian, 365, 400.
palatine, inferior, 605.
superior, 677.
palpebral, 569, 648.
pancreatic, 332.

pancreatico-duodenal, 315, 333.
parotid, 606.

perforating of femoral, 133, 166.
of foot, 184, 208.
of hand, 80.

of internal mammary,
441.
pericardial, 482.
perineal, superficial, 245.
transverse, 245.
peroneal, 196.

anterior, 196.
petrosal, 514.

pharyngeal, ascending, 629.
phrenic, inferior, 365.

superior, 365, 441, 470.
plantar, external, 202.
internal, 202.
popliteal, 126.
prevertebral, 629.
profunda of arm, inferior, 48.

superior, 48, 53.
of palm, 71.
of thigh, 149, 164.
pterygoid, 615, 678.
pterygo-palatine, 678.
pubic, 398.
pudic, accessory, 399.

external, 138, 264.
internal, 119, 242, 250, 258,
399.
pulmonary, 464, 479.
pyloric, 333.
radial, 62, 80, 90.
ranine, 623.

recurrent, interosseous, posterior, 90.
palmar, 80.
radial, 63.
tibial, 182.
ulnar, anterior, 65,
posterior, 66.
renal, 356, 364.
sacral, lateral, 397, 537.

middle, 400.
scapular, dorsal, 38.

posterior, 38, 522.
sciatic, 118, 399.
sigmoid, 318.
spermatic, 277, 282, 364.
spheno-palatine, 678.
spinal, anterior, 545, 718.
posterior, 545, 18.
splenic, 332.
sternal, 441.
stemo-mastoid of thyro

of occipital, 605.
stylo-mastoid, 606.

INDEX.

Artery or Arteries : —

subclavian, left, 468, 593.

right, 591.
sublingual, 623.
submental, 605,
subscapular, 24.
superficial cervical, 9, 522.
perineal, 245.
volar, 63.
superior fibular, 182.
supraacromial, 9.
supraorbital, 503, 647.
suprarenal, 364.
suprascapular, 9, 38, 522, 594.
sural, 127.
tarsal, 183.

temporal, anterior, 503.
deep, 615.
middle, 606.
posterior, 503.
superficial, 503, 606.
thoracic, alar, 24.
long, 24.
superior, 23.
thyroid, inferior, 587, 594.
lowest, 587.
superior, 587, 604.
tibial, anterior, 181.
posterior, 195.
tonsillar, 605, 665.
transverse, cervical, 9, 522, 594.
facial, 559, 606.
perineal, 245.
of pons, 720.
tympanic, 614.
ulnar, 64.
umbilical, 396.
uterine, 399.
vaginal, 398.

vertebral, 532, 593, 707, 718.
vesical, inferior, 398.
superior, 398.
vestibular, 822.
Vidian, 678.
volar, superficial, 63.
Articular popliteal arteries, 127, 128.
nerves, 129, 130.
Articulation, acromio-clavicular, 37.

astragalo-calcanean, 224.
astragalo-navicular, 226.
atlanto-axial, 712.
of bones of the tympanum,

809.
calcaneo-cuboid, 227.
of carpal bones, 100.
carpo-metacarpal, 103.
of cervical vertebrae, 707.
chrondo-costal, 492.

sternal, 491.
of coccygeal bones, 427.
of costal cartilages, 492.
costo- vertebral, 489.
crico-arytenoid, 702.

thyroid, 702.
of cuneiform bones, 229.
cuneiform to cuboid, 229.
cuneiform to navicular, 228.
femoro-tibial or knee, 213.

Articulation, of hip, 169.

humero-cubital or elbow, 95.
inter chondral, 492.
of lower jaw, 611.
lumbo-sacral, 427.
of metacarpal bones, 102.
metacarpo-phalangeal, 104.
metatarsal, 229.
metatarso-phalangeal, 232.
of navicular bone, 228.
occipito-atlantal, 712.
phalangeal of fingers, 105.

of toes, 232.

of pubic symphysis, 429.

radio-carpal or wrist, 98.

ulnar, inferior, 100.

superior, 97.

sacro-coccygeal, 427.

iliac, 429.
scapulo-humeral or shoulder,
92
sterno-clavicular, 712.
sternum, pieces of, 492.
tarsal, transverse, 228.
tarso-metatarsal, 230.
temporo-maxillary, 611.
of the thumb, 103.
tibio-fibular, 221.
tibio-tarsai or ankle, 222.
of vertebrae, 492.
Aryteno-epiglottidean folds, 696, 701.

muscles, 691.
Arytenoid cartilages, 700.
glands, 696.
muscle, 690.
Ascending aorta. See Aorta,
cava, 320, 367, 409.
cervical artery, 594.
colon, 302.

pharyngeal artery, 629.
Association-fibres of brain, 775.
Atlanto-axial articulations, 712.

ligaments, 712.
Atrium of heart, 457.

of middle meatus, 671.
Attollens aurem. See Muscle.
Attrahens aurem. See Muscle.
Auditory artery. See Artery.

canal or meatus, external, 803.
nerve. See Nerve,
nuclei, 784.
striae, 782.
tubercle, 783.
Auricle of the ear, 569.
Auricles of the heart, 455.

left, 462.
right, 457.
structure of, 474.
Auricular appendages, 455.

arteries. See Artery,
vein, posterior. See Vein,
nerves. See Nerve.
Auriculo-temporal nerve. See Nerve,
ventricular aperture, left, 463.
right, 461.
Auriculo-ventricular groove, 454.

rings, 463.
Axilla, 16.

INDEX.

827

Axillary artery, 22.

glands, 18.

sheath, 20.

vein, 17, 24.
Axis, of cochlea, 817.

coeliac, of artery. See Artery,
thyroid of artery, 594.
Azygos, artery, 129.

uvulae muscle. See Muscle.

veins. See Veins.

Back, dissection of, 1.
Bartholin's duct, 258.

glands. See Glands.
Base of bladder, 388, 395.
brain, 725.

the skull, arteries of, 514, 518.
dissection of, 512.
nen-es of, 515.
Basilar artery. See Artery,
membrane, 819.
plexus. See Plexus.
Basilic vein, 41.
Biceps. See Muscle.
Bile-ducts, 335.

structure of, 341.
Biventer cervicis muscle. See Muscle.
Biventral lobe, 778.
Bladder, gall, 351.

urinary, interior of, 410, 425.
ligaments of, 378.
relations of, 387, 394.
structure of, 409.
Bodies, geniculate, 770.
Pacchionian, 507.
quadrigeminal, 771.
suprarenal, 357.
Bones of the ear, 809.

ligaments of, 810.
muscles of, 810.
Brachia of corpora quadrigemina, 771 .
Brachial aponeurosis, 43,
artery, 46.
plexus, 25, 596.
veins, 48.
Brachialis anticus, 50.
Brachio-cephalic artery. See Artery.

veins. See Veins.
Brain, base of, 725.

membranes of, 716.
origin of nerves, 726.
preservation of, 510, 715.
removal of, 509.
vessels of, 718.
Breast, 13.

Broad ligament of uterus, 391.
Bronchial arteries, 479.

glands. See Glands,
tubes, 479.
veins, 479.
Bronchi, 477.
Bronchia, 479.

Brunner's glands. See Glands.
Buccal artery. See Artery.
Buccal nerves. See Nerve.
Buccinator muscle. See Muscle.

Bulb, of corpus cavemosum, 252.
spongiosum, 252.
olfactory, 744.
of spinal cord, 731.
of the urethra, 252.

artery of. See Artery,
nerve of. See Nerve,
of the vestibule, 257.
Bulbo-cavemosus muscle. See Muscle.
Bulbous'part of the urethra, 413.
Buttock, dissection of. See Dissection.

Caecum coli, 302.

relations of, 324.
Calamus scriptorius, 781.
Calcaneal arteries. See Artery.
Calcaneo-plantar nerve. See Nerve.
Calcar avis, 761.
Calcarine fissure, 753.
Calices of the ureter, 357.
Callosal convolution, 754.

sulcus, 754.
Calloso-marginal sulcus, 752.
Canal, anal, 387.

auditory, external, 803.

of cochlea, 819.

crural, 145.

Hunter's, 154.

hyaloid, 800.

inguinal, 286.

lachrymal, 566.

of Nuck, 276.

of Petit, 801. V

of Schlemm, 792.

semicircular, 816.

membranous, 820.
of spinal cord, 548.
of the tensor tympani, 806.
of Wirsung, 342.
Canalis reuniens, 819, 821.
Canthus of eyelids, 566.
Capitula laryngis, 700.
Capsular arteries. See Artery.

ligament. See Ligament.
Capsule, of crystalline lens, 801.

external, of cerebrum, 766.
of Ghsson, 349.
internal, of cerebrum, 768.
of kidney, 356.
suprarenal, 357.
of Tenon, 644, 790.
Caput caecum coli, 507.
gallinaginis, 412.
Cardia of stomach, 338.
Cardiac nerves. See Nerve,
plexus. See Plexus,
veins. See Veins.
Carotid arteries. See Artery,
plexus. See Plexus.
Carpal arteries. See Artery.

articulations, 100.
Carpo-metacarpal articulation. See Arti-
culation.
Cartilage, arytenoid, 700.
cricoid, 699.
cuneiform, 700.

828

INDEX.

Cartilage, of the ear, 571.

septal of the nose, 565, 669.
thyroid, 698.
Cartilages, of the nose, 565.
of Santorini, 700.
of trachea, 703.
Cartilagines quadratae, 565.
Cartilago triticea, 701.
Caruncula lachrymalis, 568.
Carunculae myrtiformes, 255.
Cauda equina, 544.
Caudate lobe, 347.

nucleus, 766.
Cava, inferior. See Vena Cava,
superior. See Vena Cava.
Cavernous body, 252.

artery of. See Artery,
plexus, 518.
sinus. See Sinus.
Central artery of the retina, (o) 646, (d).
800.
branches of cerebral arteries. See

Artery,
ligament of cord, 541.
lobe of cerebellum, 778.

of cerebrum, 748, 752.
pillar of cochlea, 817.
point of the perineum, 246.
sulcus, 747.
tendon, 359.
Centrum ovale cerebri, 756.
Cephalic vein, 16, 42.
Cerebellar arteries. See Artery.
Cerebellum, form of, 776.
lobes of, 777.
structure of, 779.
Cerebral arteries. See Artery.
Cerebro-spinal fluid, 717.
Cerebrum, convolutions of, 745.
fibres of, 773.
form of, 740.
interior of, 755.
lobes of, 749.
Ceruminous glands, 804.
Cervical arteries. See Artery,
fascia. See Fascia,
ganglion, inferior. See Ganglion,
middle. See Ganglion,
superior. See Ganglion,
glands, 579.
nerves. See Nerve,
plexus of nerves, deep branches,
598.
superficial
branches,
578.
Cervicalis ascendens muscle. See Muscle.
Cervico-facial nerve. See Nerve.
Cervix uteri, 393.

vesicae, 388.
Chamber of the aqueous, 798.
Check ligaments. See Ligaments.
Cheeks, 666.

Chiasma of the optic nerves, 727.
Choanee, 660.

Chondro-costal articulations. See Articu-
lation,
glossus muscle. See Muscle.

Chondro-sternal articulations. See Articu-

j lation.

j Chorda tympani nerve, 625.
Chordas tendinese, 461.

Willisii, 508.
Choroid arteries of the brain. See Artery,
coat of the eye, 793.
plexuses of the brain. See Plexus,
veins of the eye. See Vein,
brain. See Vein.
Choroidal fissure. See Fissure.
Ciha, 554.

Ciliary arteries, 797.
muscle, 795.
part of retina, 799.
processes of the choroid, 794.

of the suspensory liga-
ment, 801.
nerves, 797.
veins. See Veins.
Cingulum, 756.
Circle of Willis, 725.
Circular sinus, 513.
Circumflex artery. See Artery.

nerve, 17, 34.
Circumvallate papillae, 683.
Claustrum, 769.
Clava, 733.

Clavicular cutaneous nerves. See Nerves.
Clitoris, 255, 257.
Coccygeal artery. See Artery,
muscle. See Muscle,
nerve. See Nerve.
Cochlea, 816.

aqueduct of, 819.
canal of, 819.
nerve of. See Nerve.
vessels of, 822.
Cochleariform process, 806.
Coeliac artery or axis. See Artery.
glands, 371.
plexus. See Plexus.
Colic arteries. See Artery.

impression on liver, 347.
Collateral eminence, 754, 760.

fibres of cerebrum, 774.
fissure. See Fissure.
Colles, fascia of, 244.
Colon, 301, 302.

structure of, 326.
Columna nasi, 565.
Columnse carneae, 460.
Columns, of the rectum, 418.

of the spinal cord, 547.
of the vagina, 420.
Comes nervi ischiadici artery, 118.

phrenici artery, 441.
Commissure, anterior of cerebrum, 769.
of the cord, 548.
optic, 727.

posterior of cerebrum, 772.
soft of cerebrum, 766.
of vulva, 255.
I Commissural fibres of the cerebellum, 780.

of the cerebrum, 774.
j Common sinus, 820.
i Communicating arteries. See Artery.
I peroneal nerve. See Nerve.

INDEX.

829

Communicating tibial nerve. See Nerve. 1
Complexus muscle. See Muscle.
Compressor iiaris muscle. See Muscle.
Conarium, 772.
Concha, 569.
Congenital hernia, 289.
Coni vasculosi, 280.
Conical papillae, 683.
Conjoined tendon, 272.
Conjunctiva, 568.
Conoid ligament, 36.
Constrictor. See Muscle.
Conus arteriosus, 460.
medullaris, 545.
Convolutions of the brain, 745.
Coraco-acromial ligament, 37.
brachialis muscle, 45.
clavicular ligament, 36.
humeral ligament, 92.
Cord, spermatic, 276.
Cordiform tendon, 359.
Cords on the abdominal wall, 292.

vocal, 695.
Cornea, 792.
Cornicula laryngis, 700. i

Comua of grey crescent, 548.

of lateral ventricle, 758. I

Corona glandis, 253.
radiata, 774.
Coronary arteries. See Artery. i

ligament of the liver. See Liga-
ment,
plexus of the stomach. See !
Plexus. 1

plexuses of the heart. See \

Plexus,
sinus, 456.

vein of the stomach. See Vein.
Corpora albicantia, 726, 743.
Arantii, 462.
cavernosa, 252, 415.
geniculata, 770, 771.
mamillaria, 743.
quadrigemina, 771.
Corpus callosum, 726, 744, 756.
dentatum cerebelli, 780.
medullse, 737.
fimbriatum, 394.
Highmorianum, 279.
luteum, 424.

Morgagni. See Hydatid,
spongiosum urethree, 252, 253,

416.
striatum, 766.
Corpuscles of Malpighi, 356.
Corrugator. Sef^ Muscle.
Cortex, of cerebellum, 755.
of cerebrum, 745.
of tongue, 686.
Corti, organ of, 819.

Cortical branches of cerebral arteries. See
Artery,
substance of the kidney. See
Kidney Structure.
Costo-clavicular ligament. See Ligament,
colic fold, 312.
coracoid membrane, 20.
transverse ligaments. See Ligament.

Cotunnius. fluid of, 816.
Cotyloid ligament, 171.
Covered band of Keil, 756.
Cowper's glands, 250, 413.
Cranial nerves, 514.

nuclei of, 783.
Cremaster muscle. See Muscle.
Cremasteric artery. See Artery.

fascia, 270.
Crest of the urethra, 412.

vestibule, 815.
Cribriform fascia, 138.
Crico-arytenoid articulation. See Articu-
lation,
muscle, lateral. See
Muscle,
posterior. See
Muscle,
thyroid artery. See Artery.

articulation. See Articu-
lation,
membrane. See Membrane,
muscle. See Muscle,
tracheal ligament. See Ligament.
Cricoid cartilage, 699.
Crista acustica, 820.
Crucial ligaments. See Ligament.
Crura cerebelli, 780.

cerebri, 725, 741.
of the clitoris, 267.
of the diaphragm, 359.
of the fornix, 760.
of the penis, 252, 416.
Crural arch, 143.

deep, 145, 283.
canal, 145.
hernia, 146.
nerve, 144.
ring, 146.
septum, 146.
sheath, 146.
Crusta of cerebral peduncle, 742.
Crypts of Lieberklihn, 323.

of tongue, 687.
Crystalline lens, 801.
Cuneate funiculus and tubercle, 733.

lobule, 754.
Cuneiform cartilages, 700.
Cupola cochleae, 817.
Curve of the urethra, 390.
Cutaneous nerves of the abdomen, 262.
of the arm, 42.
of the back, 3, 4.
of the buttock, 110.
of the face, 564.
of the foot, back, 176.
sole, 197.
of the forearm, 42, 56.
of the hand, back, 57, 58.

palm, 70.
of the head, 504.
of the leg, back, 187.
front, 176.
of the neck, back, 579.
front, 578.
of the perineum, 240, 243.
of the shoulder, 31.
of the thigh, front, 140.

830

INDEX.

Cutaneous nerves of the thorax, 13.
Cystic artery. See Artery.

duct, 352.

plexus of nerves. See Plexus.

vein. See Vein.

Dartoid tissue, 252.
Decussation of the pyramids, 731, 735.
Deep cervical artery. See Artery,
crural arch, 145.

transverse muscle of perineum. See
Muscle.
Deferential artery. See Artery.
Deltoid ligament. See Ligament.

muscle, 31.
Dental arteries. See Artery.

nerves. See Nerve.
Dentate body of cerebellum, 780.

of medulla oblongata, 737.
fascia, 755.
fissure, 754.

ligament. See Ligament.
Depressor. See Muscle.
Descendens cervicis nerve. See Nerve.
Descending cava, 468.
colon, 303.
thoracic aorta, 481.
Diaphragm, 358, 489.

arteries of, 365.
plexus of, 337.
Digastric muscle. See Muscle.

nerve. See Nerve.
Digital arteries. See Artery,
nerves. See Nerve,
sheaths, 71.
Dilator. See Muscle.
Disc, interpubic, 430.

intervertebral, 494.
optic, 799.
Dissection of the abdominal cavity, 296.
wall, 260.
of the arm, 39.
of the axilla, 11.
of the back, 1, 519.
of the base of the skull, 512.
of the brain, 715.
of the buttock, 109.
of the cardiac plexus, 472.
of the carotid artery, internal,
627.
of the carotid plexus, 518.
of the cerebellum, 776.
of the cerebrum, 740.
of the coeliac axis, 331.
of the corpus callosum, 756.
of the corpus striatum, 766.
of the cranial nerves in the
neck, 630.
of the crus cerebri, 742.
of the deep vessels and nerves
of the neck, 626.
of the diaphragm, 358.
of the ear, 803.
of the eye, 790.
of the eyelids, 556.
of the face, 550.
of the facial nerve, 679.

Dissection of the fascia lumborum, 271,

272.
of femoral hernia, 143.
of the foot, back, 184.
sole, 197.
of the forearm, back, 83.
front, 55.
of the fourth ventricle, 781.
of the hand, back, 90.
palm, 69.
of the head, external parts, 499.
internal parts, 507.
of the heart, 457.
of the hollow before the elbow,
59.
of the hypogastric plexus, 318.
of inferior maxillary nerve, 613.
of inguinal hernia, 285.
of Jacobson's nerve, 812.
of the labyrinth, 814.
of the larynx, 688.

cartilages, 698.
muscles, 689.
nerves, 696.
of the leg, back, 186.
front, 175.
of the ligaments of atlas and
axis, 707.
of the ligaments of atlas and
occiput, 707.
of the ligaments of axis and
occiput, 710.
of the ligaments of clavicle and
scapula, 36, 707.
of the ligaments of the hip-
joint, 169.
of the ligaments of the jaw,
612.
of the ligaments of the lower
limb, 212.
of the ligaments of pelvis, 427.
of the ligaments of ribs, 490.
of the ligaments of the upper
limb, 92.
of the ligaments of the vertebrae,
492, 707.
of the lower limb, 109.
of Meckel's ganglion, 674.
of the neck, 572.

anterior triangle,
581.
posterior triangle,
675.
of the nose, 667.
of the ophthalmic of the fifth
nerve, 516.
of the orbit, 639.
of the otic ganglion, 680.
parotid gland, 559.
of the pelvis, 376.

side view, female,
390.
male,
376.
of the perineum, female, 255.

male, 236.
of the pharynx, 654.
of the poHs, 739.

INDEX.

8B1

Dissection of the popliteal space, 124.

of the prevertebral muscles, 704.
of the pterygoid region, 607.
of the sacral plexus, 400.
of the shoulder, 28.
of the soft palate, 661.
of the solar plexus, 336.
of the spinal cord, 539.
of the subclavian arterj^ 588.
of the submaxillary region, 619.
of the superior maxillary nerve,
652.
of the testis, 277.
of the thigh, back, 130.
front, 136.
of the thorax, 436.
of the tongue, 682.
of the triangular space of the
thigh, 146.
of the tympanum, 805.

vessels and
nerves, 812.
of the upper limb, 1.
Dorsal artery. See Artery,
nerves. See Nerve.
Dorsalis scapulae artery, 24.
Douglas, fold of, 274.

pouch of, 376, 391.
Drum of the ear, 805.
Duct, of Bartholin, 258.

bile, common, 335, 341.
of cochlea, 819.
cystic, 352.
ejacuiatorj-, 408.
hepatic, 335.
lactiferous, 14.
lymphatic, right, 486.
nasal, 567.
pancreatic, 342.
parotid, 560.
of Rivinus, 625.
seminal, common, 389.
of Stenson, 560.
thoracic, 371, 485, 595.
of Wharton, 625.
Ductus arteriosus, 465.

communis choledochus, 335, 341.
endolpnphaticus, 815, 821.
Stenonis, 560.
venosus, 348.
Duodenal impression on liver, 347.
Duodeno-jejunal flexure, 301, 328.

fossa, 313.
Duodenum, characters of, 321.
peritoneum of, 312.
relations of, 301, 327.
Dura mater, cranial, 507, 510.
spinal, 539.
nerves of, 514.
vessels of, 514.

Ear, external, 569, 803.

internal, 814.

middle, 805.
Eighth nerve. See Auditory Nerve.
Ejaculator urinee. See Muscle.
Elbow-joint, 95.

Eleventh nerve. See Nerve, Spinal

Accessory.
Eminentia coUateralis, 762.

teres. 782.
Encephalon, 715.
Encysted hernia, 289.
Endocardium, 477.
Endolymph, 819.
Ependyma, 758.
Epididymis, 281.
Epigastric arterj'. See Artery,
fossa, 260.

plexus. See Plexus,
region of the abdomen, 298.
veins. See Vein.
Epiglottis, 700.
Epoophoron, 424.
Erector. See Muscle.
Ethmoidal arteries, 647.
bulla, 670.
cells, 670.
Eustachian tube, cartilaginous part, 660,

808.
osseous part, 808.
valve, 459.
Eversion of foot, 186.
Extensor. See Muscle.
External cutaneous nerves. See Nerve.
Extraventricular nucleus, 766.
Eyeball, 790.
brows, 556.
lashes, 556.
lids, 556.

muscles of, 553.
nerves of, 569.
structure, 567.
vessels, 569.

Face, dissection of, 550.
Facial artery. See Artery,
nerve. See Nerve,
nucleus, 729.
vein. See Vein.
Falciform border of saphenous opening,

143.
ligament of the liver, 305, 313.
Fallopian tube, 394, 424.
Fallopius, aqueduct of, 806.
Falx cerebelli, 511.

cerebri, 508.
Fascia, anal, 383.

axillary, 12.
brachial, 43.
bucco-pharyngeal, 655.
cervical, deep, 574, 580.
of Colles, 244.
cremasteric, 270.
cribriform, 138.
dentata, 755, 762.
of the forearm, 68.
iliac, 293, 370.
infundibuliform, 275.
intercolumnar, 267.
lata, 125, 141.
of the leg, 177, 187, 188.
lumborum, 272, 521.
obturator, 380.

832

INDEX.

Fascia, palmar, 70.

palpebral, 568.
parotid, 560.
pelvic, 376, 378.
perineal, deep, 248.

superficial, 244.
plantar, 198.
of psoas, 370.
of pyriformis, 380.
of quadratus, 370.
recto-vesical, 380, 383.
of Scarpa, 262.
spermatic, 267.
temporal, 506.
transversalis, 275.
triangular, 268.
Fasciculus teres, 782.
Fauces, 661.

Femoral artery, 148, 154.
hernia, 146, 292.
ligament, 143.
vein, 149.
Fenestra ovalis, 805.

rotunda, 805.
Fibres of the cerebrum, 774.

of the cerebellum, 780.
Fibro-cartilage. See Interarticular.

of heart, 474, 477.
Fibrous coat of eye. See Sclerotic Coat.
Fifth nerve. See Nerve Trigeminal,
nuclei of, 784.
^ventricle of brain. See Ventricle.
Filiform papillae, 683.

Fillet of the pons and mid-brain, 743, 771.
Filum terminale, 541.
Fimbria of brain, 762.
Fimbriae of the Fallopian tube, 424.
First nerves, 726.
Fissure, calcarine, 753.
choroidal, 762.
collateral, 754.
dentate, 754.
Glaserian, 806.
hippocampal, 754.
longitudinal, of cerebrum, 745.

of liver, 348.
parieto-occipital, 747, 751.
portal, 347.
of Sylvius, 745.
transverse of cerebrum, 762.
of liver, 347.
Fissures, of the cerebrum, 745.
of the cord, 546.
of Santorini, 571.
Flexor. See Muscle.
Flexure, duodeno-jejunal, 301, 328.
hepatic, 302.
splenic, 302.
Flocculus cerebelli, 778.
Fold of Douglas, 274.
Folia of cerebellum, 777.
Folium cacuminis, 778.
Foot, dorsum, 184.

sole, 197.
Foramen caecum of medulla oblongata, 731.
of tongue, 682.
of Monro, 761.
ovale, 458, 463.

Foramen quadratum, 361.

for vena cava, 362, 489.
of Winslow, 309, 311.
Foramina Thebesii, 459.
Forearm, dissection of, 55, 83.
Formatio reticularis, 737, 740.
Fornix, 760.

conjunctivae, 568.
Fossa, duodeno-jejunal, 313.
ischio-rectal, 238.
navicular of the urethra, 413.

of the vulva, 255.
ovalis, 458.
rhomboidalis, 781.
Fossae of abdominal wall, 292.
Fourchette, 255.

Fourth nerve. See Nerve Trochlear,
nucleus of, 784.
ventricle. See Ventricle.
Fovea, centralis, 799.

hemielliptica, 815.
hemispherica, 815.
Foveae of fourth ventricle, 782.
Fraenulum clitoridis, 255.
labii, 666.

pudendi, s. vulvae, 255.
Fraenum epiglottidis, 687.

of ileo-csecal valve, 325.
linguae, 683.
praeputii, 252
Frontal artery. See Artery.

lobe of cerebrum, 747, 749,
nerve. See Nerve,
sinus. See Sinus,
vein. See Vein.
Fundus of bladder, 387.
of stomach, 338.
of uterus, 393, 420.
Fungiform papillae, 683.
Funiculus cuneatus, 732.
gracilis, 732.
of Eolando, 732.
Furrow of Rolando, 747.
Furrowed band, 779.
Furrows of cerebrum. See Fissures,
of spinal cord. See Fissures.

Galactophorus ducts, 14.
Galen, veins of. See Veins.
Gall-bladder, 351.
Ganglia, of glosso-pharyngeal, 632.
lumbar, 374.
sacral, 404.
semilunar, 337.
of spinal nerves, 542.
thoracic, 470.
of vagus, 633.
Ganglion, cervical, inferior, 638.
middle, 638.
superior, 637.
Gasserian, 516.
geniculate, 679.
impar, 404.
intervertebral, 543.
jugular, 632.
lenticular, 646.
Meckel's, 673.

INDEX.

833

Ganglion, ophthalmic, 646.
otic, 673, 680.
petrosal, 632.
sphenopalatine, 673.
spirale, 822.
submaxillary, 624.
thyroid, 638.
(iastric arteries. See Artery.

impression on liver, 347.
veins. See Veins.
Gastro-colic omentum, 311.

duodenal artery. See Artery,
epiploic arteries. See Artery.

veins. See Veins,
hepatic omentum, 310.
splenic omentum, 311.
Gastrocnemius muscle. See Muscle.
Gelatinous substance, 737.
Gemellus. See Muscle.
Generative organs, 419.
Geniculate bodies, 770.

ganglion. See Ganglion.
Genio-glossus or Genio-hyo-glossus. See

Muscle,
hyoid muscle. See Muscle.
Genital organs, 419.
Genito-crural nerve, 140.
Genu, of corpus callosum, 744.
of internal capsule, 768.
of optic tract, 772.
Gimbemat's ligament, 144.
Giraldes, organ of, 282.
Gland of Havers, 172.
lachrymal, 641.
parotid, 559, 584.
pineal, 772.
prostate, 406.
sublingual, 625.
submaxillary, 619.
thymus, 446.
thyroid, 586.
Glands, agminated, 323.
arytenoid, 696.
Bartholin's, 258.
Brunner's, 341.
ceruminous, 804.
Cowper's, 250.
labial, 666.
laryngeal, 696.
Lieberkiihn's, 323.
lingual, 688.
lymphatic, axillar\', 18.

bronchial, 485.
cardiac, 485.
cervical, superficial,

579.
deep, 579.
cceliac, 371.
concatenate, 579.
inguinal, 138, 264.
intercostal, 485.
lingual, 688.
lumbar, 371.
mastoid, 579.
mediastinal, 485.
mesenteric, 316.
meso-colic, 316.
parotid, 559.

D.A.

Glands, lymphatic, pelvic, 405.

popliteal, 130.
sternal, 485.
submaxillary, 584.
suboccipital, 579.
mammary, 13, 16.
Meibomian, 568.
molar, 561.
of Pacchioni, 507.
Peyer's, 323.
solitary, 323.
tarsal, 568.
of trachea, 703.
Glandulse concatenatae, 579.

odoriferae, 2.52.
Glans of the clitoris, 257.

of the penis, 253.
Glaserian fissure, 806.
Glenoid ligament, 93.
Glisson's capsule, 349.
Globus major epididymis, 281.
minor epididymis, 281.
Glosso-epiglottidean folds, 687.

pharyngeal nerve. See Nerve,
nucleus, 784.
Glottis, 693.
Gluteal artery, 116.

nerve, inferior, 119.
superior, 117.
muscles. See Muscle.
Graafian vesicles, 423.
Gracilis muscle, 161.
Grey commissure of the cord, 548.
crescent of the cord, 548.
substance of medulla oblongata, 737.
of the third ventricle, 766.
tubercle of Rolando, 732.
Gullet, 484.

Gustatory nerve. See Lingual.
Gyri breves, 752.

of cerebrum, 745, 748, 752.
longi, 752.
Gyrus fornicatus, 754.

Hsemorrhoidal arteries. See Artery.

nerve, inferior. See Nerve,
plexus of nerves. See
Plexus,
veins. See Veins.
Ham, 130.

Hamulus, laminae spiralis, 818.
Hand, dissection of, 60.
Havers, gland of. See Gland.
Head, movements of, 712.
Heart, 452.

constituents, 454.
dissection of, 456.
position, 453.
structure of, 473.
Helicotrema, 818.
Helix, 569.

fossa of, 569.
muscles of, 570.
Hemispheres of cerebellum, 776.

of cerebrum, 745.
Hepatic artery. See Artery,
ducts, 335.

8S4

INDEX.

Hepatic flexure of colon, 302.
plexus. See Plexus,
veins. See Veins.
Hernia, crural or femoral, 146.
inguinal, external, 286.
internal, 290.
umbilical, 291.
Hesselbach's triangle, 290.
Hiatus cochleae, 818.

semilunaris, 670.
Highmore, body of, 279.
Hilum of kidney, 353.
of lung, 447.
of ovary, 423.
of spleen, 343.
of suprarenal body, 357.
Hip-joint, 169.
Hippocampal fissure, 754.
Hippocampus major, 761.
minor, 761.
Hollow before elbow, 59.
Hunter's canal, 154.
Hyaloid canal, 800.

membrane, 800,
Hymen, 255.

Hyo-epiglottidean ligament, 700.
glossal membrane, 684.
glossus muscle. See Muscle.
Hyoid artery. See Artery.

bone, 698.
Hypochondriac region of abdomen, 298.
Hypogastric artery. See Artery.

plexus of nerves. See Plexus,
region of the abdomen, 297.
Hypoglossal nerve. See Nerve,
nucleus, 730, 784.

Ileo-csecal fold, 314.
valve, 325.
colic artery. See Artery,
fold, 314.
valve, 325.
Ileum, relations of, 301.
structure of, 321.
Hiac arteries. See Artery,
colon, 304.
fascia, 293, 370.
part of fascia lata, 142.
region of the abdomen, 298.
veins. See Vein.
Iliacus muscle, 167.
Hio-costalis. See Muscle,
femoral ligament, 170.
hypogastric nerve. See Nerve,
inguinal nerve, 140.
lumbar artery. See Artery.

ligament. See Ligament,
vein. See Vein,
psoas, 370.
tibial band, 142.
Incisor branch of nerve. See Nerve.
Incus, 809.

Indicator muscle. See Muscle.
Infantile hernia, 289.
Inframarginal convolution, 752.
Inframaxillary nerve. See Nerve.
Infraorbital artery. See Artery,

Infraorbital nerves. See Nerve,
plexus. See Plexus,
vein. See Vein.
Infrascapular artery. See Artery,
Infraspinatus muscle, 34.
Infrasternal fossa, 260.
Infratrochlear nerve. See Nerve.
Infundibula of the lung, 479.

of the ureter, 357.
Infundibuliform fascia, 275.
Infundibulum of the brain, 726, 743.
of the heart, 460.
of the nose, 670.
Inguinal canal, 286,
fossae, 292.
furrow, 260.
glands, 138, 264,
hernia, external, 286.
internal, 290.
region of the abdomen, 298.
Innominate artery. See Artery.

veins. See Veins.
Inscriptiones tendineee, 273.
Insula, 748.
Interarticular fibro-cartilage of the jaw,

612.
of the knee,

218.
sterno-clavi-

cular, 714.
of the wrist,
100.
ligament. See Ligament.
Interclavicular ligament. See Ligament.
Intercolumnar fascia and fibres, 267.
Intercostal aponeuroses, 438.

arteries. See Artery,
muscles. See Muscles,
nerves. See Nerves,
veins. See Vein.
Intercosto-humeral nerve, 43.
Intermediate process, 548.
Intermuscular septa of the arm, 52.
of the foot, 198.
of the leg,

177, 185, 188, 192.
of the thigh, 159.
Internal cutaneous nerve. See Nerve.
Interosseous arteries. See Artery,

ligaments or membrane. See
Ligament,
muscles. See Muscle,
nerves. See Nerve,
Interpeduncular space, 742.
Interpubic disc, 430.
Interspinal muscles. See Muscles.
Intertransverse muscles. See Muscles.
Intervertebral disc or substance, 494.

ganglia, 543.
Intestinal arteries. See Artery,
canal divisions, 301.

structure of, 321, 324,
Intestine, large, 324.

small, 301, 321.
Intraparietal sulcus, 750.
Intraspinal vessels, 549.
Intraventricular nucleus, 766.
Intumescentia ganglioformis, 821.

INDEX.

S3o

Inversion of foot, 194.
Iris, 796.

nerves of, 797.
structure of, 796.
vessels of, 797.
Ischio-cavemosus muscle. See Muscle.

rectal fossa, 238.
Island of Reil, 748.
Isthmus cerebri, 770.
faucium, 660.
of the thyroid body, 586.
of the uterus, 421.
It€r a tertio ad quartum ventriculum, 773.

Jacobson's nerve. See Ner\e.
Jejunum, relations of, 301.
structure of, 321.
Joint, ankle, 222.

elbow, 95.

great toe, 230.

hip, 169.

knee, 213.

lower jaw, 611.

shoulder, 92.

thumb, 103.

wrist, 98.
Jugular ganglion. See Ganglion,
veins. See Vein.

Kerato-cricoid muscle. See Muscle.
Kidney, 306.

relations of, 307, 353.

structure of, 355.

vessels of, 356.
Knee-joint. See Articulation.

Labia pudendi externa s. majora, 255.
interna s. minora, 255.
Labial arterj', inferior. See Artery,
glands, 666.
ner\-es. See Nerves.
Labyrinth, 814.

lining of, 816.
membranous, 820.
osseous, 814.
Lachrymal artery. See Artery,
canals, 566.
gland. See Gland.
nerA'e. See Nerve,
papilla, 566.
point, 566.
sac, 567.
Lacteals, 324.
Lactiferous ducts, 14.
Lacunae of the urethra, 413.
Lamina cinerea, 726, 744.

quadrigeraina, 770.
spiralis cochleae, 818.
suprachoroidea, 795.
Laminae of cerebellum, 777, 779.

of the lens, 802.
Large intestine, relations of, 301.

structure and form of, 324.

Laryngeal arteries. See Arteiy.
nerves. See Nene.
pouch, 694.
Larynx, 688.

apertures of, 661, 693.
cartilages of, 698.
interior of, 693.
ligaments of, 701.
muscles of, 689.
nerves of, 697.
ventricle of, 694.
vessels of, 697.
Lateral column of the cord, 547.

cutaneous nerves. See Nerves,
nucleus, 737.

recess of the pharynx, 665
sinus, 511.
tract, 731, 736.
ventricles, 758.
Latissimus dorsi, 7, 27.
Leg, dissection of the back, 186.
front, 175.
Lens of the eye, 801.
Lenticular ganglion. See Ganglion.

nucleus, 766.
Levator. See Muscle.
Lieberkiihn's crypts, 323.
Lieno-renal ligament, 306.
Ligament or Ligaments : —
acromio-clavicular, 37.
alar of the knee, 216.
annular, anterior of ankle, 178.
external of ankle, 178.
internal of ankle, 197.
of radius, 97.
of stapes, 810.
anterior of wrist, 82, 91.
posterior of wrist, 83.
anterior, of ankle-joint, 223.
of elbow-joint, 96.
of knee-joint, 215.
of wrist-joint, 99.
of carpus, 101.
arched, of diaphragm, 360.
of arterial duct, 465.
astragalo-calcanean, 225.
astragalo-navicular, 226.
atlanto-axial, accessory, 712.
anterior, 708.
posterior, 710.
transverse, 711.
of bladder, 378, 384, 392.
broad, of uterus, 391.
calcaneo-cuboid, 227.

navicular, 226.
capsular of the hip, 169.
of the knee, 213.
of the shoulder, 92.
of the thumb, 103.
carpal, dorsal, 101.
palmar, 101.
carpo-metacarpal, 103.
central, of the cord, 541.
check, 711.
chondro-stemal, 491.
of the coccyx, 427.
common, anterior of vertebrae, 427,
493, 707.

3 H 2

836

INDEX.

Ligament or Ligaments : —

common, posterior, 427, 493, 707.
conoid, 36.
coraco-acromial, 36.
clavicular, 36.
humeral, 92.
coronary of liver, 305, 313.
costo-central, 490.

clavicular, 713.
coracoid, 20.
transverse, middle, 491.

posterior, 491.
superior, 491.
vertebral, 490.
xiphoid, 492.
cotyloid, 171.
crico-arytenoid, 702.
thyroid, 701.
tracheal, 701.
crucial, 217.

of cuneiform bones, 229.
deltoid, 223.
dentate, 541.

falciform of liver, 305, 313.
femoral, 143.
of Gimbernat, 144, 267.
glenoid, 93.
hyo-epiglottidean, 703.
ilio-femoral, 170.
lumbar, 428.
of incus, 810.

interarticular of the hip, 172.
of the ribs, 490.
of sacrum and coccyx,
427.
interclavicular, 703.
interosseous of astragalus and os
calcis, 225.
of carpus, 101.
of cuneiform bones,
229.
of metacarpal bones,
102.
of metatarsal bones,
229.
radio-ulnar, 97.
naviculo-cuboid, 229.
tibio-fibular, 215.
interspinous, 496.
intertransverse, 496.
lateral, of ankle-joint, 223.
of carpus, 101.
of elbow, 95.
lumbo-sacral, 427.
phalangeal of foot, 232.

of hand, 104, 105. ■
of jaw, 611.
of knee, 213, 214.
of liver, 305, 313.
of lung, 442.
♦ of wrist, 98, 99.

of larynx, 698.
lieno-renal, 306.
of liver, 313.
lumbo-sacral, 427.
of malleus, 810.
metacarpal, 102.
metatarsal, 229, 232.

j Ligament or Ligaments : —

I mucous, 216.

I naviculo-cuboid, 229.

cuneiform, 228.
oblique, 98.

occipito-atlantal, anterior, 708.
posterior, 709.
occipito-axial, 710.
odontoid, 711.
orbicular of the radius, 97.
ovario-pelvic, 392.
of the ovary, 392.
palpebral, 568.
of the patella, 158, 215.
of the pinna, 571.
plantar, long, 227.
short, 227.
of Poupart, 143, 267.
posterior of ankle-joint, 223.
of carpus, 101.
of elbow, 96.
of knee, 214.
of wrist, 82, 99.
pterygo-maxillary, 658.
pubic, anterior, 429.
superior, 430.
pubo-femoral, 170.
recto-uterine, 391.
of rectum, 386.
rhomboid, 713.
round, of the hip, 172.
of the liver, 348.
of the uterus, 277, 392, 394,
422.
sacro-coccygeal, 427.
iliac, 429.

sciatic, large, 124, 428.
small, 124, 428.
of sacrum, 427.
of scapula, 37.
of stapes, 810.
stellate, 490.
sterno-clavicular. 713.
stylo-hyoid, 626.

maxillary, 580, 612.
subpubic, 430.
suprascapular, 37.
supraspinous, 496.
suspensory of axis, 711.

of clitoris, 257.
of lens, 800.
of liver, 313.
of penis, 252.
of uterus, 392, 394, 422.
tarsal of eyelids, 568.
tarso-metatarsal, 230.
thyro-arytenoid, 695, 696, 702.
epiglottidean, 703.
hyoid, 701.
tibio-fibular, 221.
transverse of the atlas, 711.
of the fingers, 71.
of the hip, 171.
of the knee, 218.
of metacarpus, 81.
of metatarsus, 210.
of the toes, 199.
trapezoid, 36.

INDEX.

837

Ligament or Ligaments: —

triangular of the urethra, 248, 258.
of the uterus, 392.
vesico-uterine, 391.
Ligamenta subflava, 496.

suspensoria of mamma, 14.
Ligamentum arcuatum, 360.

denticulatum, 541.
latum pulmonis, 442.
nuchas, 6, 520.
patellae, 215.
pectinatum iridis, 793.
spirale, 819.
teres of hip, 172.
of liver, 313.
of uterus, 394.
Limb, lower, 109.

upper, 1.
Limbus cochleae, 818.
Linea alba, 266.

semilunaris, 266, 274.
splendens, 541.
Lineae transversae, 266, 274.
Lingual artery. See Arteiy.
glands. See Glands,
nerve. See Nerve,
veins. See Vein.
Linguales muscles. See Muscle.
Lingula, 781.
Lips, 666.

Liquor Cotunnii, 816.
Lithotomy, parts cut, 253.
Liver, 304.

ligaments of, 313.
lobes of, 347.
relations of, 304.
structure of, 349.
vessels of, 348, 349.
Lobes of the cerebellum, 778.
of the cerebrum, 749.
of the liver, 347.
of the lungs, 447.
of the prostate, 406.
of the testis, 280.
Lobule, cuneate, 754.
of ear, 569.
occipital, 754.
orbital, 750.

oval, or paracentral, 754.
parietal, 751.
quadrate, 754.
Lobules of the liver, 349.
Locus caeruleus, 783.
Longissimus dorsi. See Muscle.
Longitudinal fibres of cerebrum, 774.

fissure of the cerebrum. See
Fissure,
of the liver, 347, 348.
sinus, inferior. See Sinus,
superior. See Sinus.
Longus colli muscle. See Muscle.
Lower, tubercle of, 457.
Lumbar aponeurosis, 272.

arteries. See Artery,
ganglia, 374.
glands. See Glands,
nerves. See Nerve,
plexus, 110, 371.

Lumbar region of the abdomen, 298.

veins. See Veins.
Lumbo-sacral articulation, 427.

cord or nerve, 372.
Lumbricales, of the foof , 205.
of the hand, 75.
Lung, 446.

physical characters of, 447, 478.
relations of, 446.
roots of, 448.
structure of, 478.

vessels and nerves of, 449, 479, 480.
Lunula, 462.
Lymphatic duct, right, 486.

glands. See Glands.
Lymphatics of the arm, 42.
of the axilla, 18.
of the bladder, 411.
of the gall bladder, 353.
of the intestine, 324.
of the kidney, 356.
of the liver, 351.
of the lungs, 480.
of the mamma, 15.
of the neck, 584.
of the pelvis, 405.
of the penis, 417.
of the popliteal space, 130.
of the prostate, 407.
of the rectum, 418.
of the tpleen, 344.
of the stomach, 341.
of the suprarenal body, 358.
of the testicle, 277, 282.
of the thorax, 485.
of the tongue, 688.
of the tonsil, 665.
of the uterus, 422.
of the vagina, 420.
Lyra, 761.

Macula acustica, 820.

lutea, 799.
Malar nerves. See Nen-es.
Malleolar arteries. See Artery.
Malleus, 809.

Malpighian corpuscles of spleen, 344.
of kidney, 356.
Mamilla. See Nipple.
Mamillae of the kidney, 355.
Mamma, 13 — 16.

Mammary artery, external. See Artery,
internal. See Artery,
gland, 13—16.
Marginal convolution, 754.
Masseter muscle. See Muscle.
Masseteric artery. See Arterj%

nerve. See Nerve.
Mastoid antrum, 808.
cells, 808.

lymphatic glands, 579.
Maxillary artery, internal. See Artery,
nerves. See Nerve,
veins. See Vein.
Meatus auditorius extemus, 803.
nerves of, 804.

838

INDEX.

Meatus auditorius, vessels of, 804.

urinarius, 255.
Meatuses of the nose, 671.
Meckel's ganglion, 673.
Median-basilic vein. See Vein,
cephalic vein. See Vein,
nerve, 17, 48, 67, 73.
vein, 41, 56.
Mediastinal arteries. See Artery.
Mediastinum of thorax, 443.

testis, 279.
Medulla oblongata, 731.

spinalis, 538.
Medullary arteries. See Artery.

centre of cerebellum, 780.

of cerebrum, 755.
portion of tongue, 687.
velum, inferior, 779.
superior, 781.
Meibomian glands, 568.
Membrana basillaris, 819.
flaccida, 808.
pupillaris, 796.
tympani, 807.

secundaria, 808.
Membrane, costo-coracoid, 20.
crico-thyroid, 701.
of Descemet, 791.
hyaloid, 800.
hyo-glossal, 684.
obturator, 431.
pituitary, 671.
of the pupil, 796.
of Reissner, 819.
Schneiderian, 671.
thyro-hyoid, 701.
Membranes of the brain, 716.

of spinal cord, 539.
Membranous labyrinth, 820.

part of the cochlea, 820.
part of the urethra, 389, 413.
Meningeal arteries. See Artery,
nerves. See Nerves.
Meninges, 716.
Mental nerve. See Nerve.
Mesencephalon, 770.
Mesenteric artery, inferior. See Artery,
superior. See Artery,
glands. See Glands,
plexuses. See Plexus,
vein, inferior. See Veins,
superior, See Veins.
Mesentery, 312.
Meso- caecum, 302.

colon, left, 312.
right, 312.
pelvic, 312.
transverse, 312.
ovarium, 392.
rectum, 386.
salpinx, 392.
Metacarpal arteries. See Artery.

articulations. See Articulation.
Metatarsal artery See Artery.
Mid-brain, 770.
Mitral valve, 463.
Modiolus of the cochlea, 817,
Monro, foramen of, 761,

Molar glands, 561.
Mons Veneris, 260.
Monticulus, 778.
Morgagni, body of, 278.

columns of, 418.
Mouth, cavity of, 665.
Mucous ligament. See Ligament.
Multifidus spinee muscle. See Muscle.
Muscle or Musculus : —

abductor hallucis, 199.
indicis, 81.

minimi digiti mantis, 79.
pedis, 201.
pollicis, 76.
accessorius pedis, 205.

ad sacro-lumbalem, 526.
adductor brevis, 163.

hallucis obliquus, 207.

transversus, 207.
longus, 162.
magnus, 133, 167, 214.
pollicis obliquus, 79.

transversus, 79.
anconeus, 87.
of antitragus, 570.
aryteno-epiglottidean, 691.
arytenoid, 690.
attollens aurem, 500.
attrahens aurem, 500.
azygos uvulae, 664.
biceps of arm, 43.

of thigh, 131, 214.
biventer cervicis, 601.
brachialis anticus, 50.
buccinator, 556.
bulbo-cavernosus, 247, 256.
cervicalis ascendens, 526.
chondro-glossus, 621, 685.
ciliary, 795.

circumfiexus palati, 663.
coccygeus, 381, 426.
complexus, 528.
compressor naris, 552.
constrictor inferior, 657.

isthrai faucium, 633.
medius, 657.
superior, 657.
urethrse, 249.
coraco-brachialis, 45.
corrugator cutis ani, 240.
supercilii, 554.
cremaster, 269.
crico-arytenoid, lateral, 691.
posterior, 690.
thyroid, 689.
crureus, 157.
deltoid, 31.
depressor alas nasi, 553.

anguli oris, 555.
epiglottidis, 692.
labii inferioris, 555.
detrusor urinee, 409.
diaphragm, 358, 489.
digastric, 601.
dilatator naris, 552.

pupillaj, 796.
ejaculalpr urinse, 247.
erector clitoridis, 257,

INDEX.

839

Muscle or Musculus : —
erector penis, 246.
spinee, 526.
extensor carpi radialis brevior, 85.
longior, 84.
ulnaris, 86.
brevis digitorum pedis, 184.

pollicis, 88.
communis digitorum, 85.
indicis, 89.
longus digitorum pedis, 180.

pollicis, 88.
minimi digiti, 86.
ossis metacarpi pollicis, 87.
primi internodii pollicis, 88.
proprius hallucis, 179.
secundi internodii pollicis,
88.
flexor accessorius, 205.

brevis minimi digiti maniis,79.
brevis minimi digiti pedis, 207.
carpi radialis, 61, 82.

ulnaris, 62.
digitorum brevis pedis, 199.
longus pedis, 194,

206.
profundus, 67, 74.
sublimis, 64, 74.
haUucis brevis, 206.

longus, 193, 205.
perforans, 67, 194.
perforatus, 64, 199.
pollicis brevis, 78.

longus, 68, 76.
gastrocnemius, 189.
gemellus inferior, 121.
superior, 121.
genio-glossus, or genio-liyo-glossus,
622, 686.
hyoid, 622.
gluteus maximus, 112.
medius, 116.
minimus, 117.
gracilis, 161.
of helix, 570.
hyo-glossus, 621, 685.
iliacus, 167, 369.
ilio-costalis, 526.
incisive, 557.
indicator, 89.
mfraspinatus, 34.
intercostals, 438, 488, 538.
interosseus of foot, 211.
of hand, 81.
interspinales, 536.
intertransversales, 536, 706.
ischio-cavemosus, 246, 257.
kerato-cricoid, 690.
labii proprius, 557.
latissimus dorsi, 7, 27.
levator anguli oris, 555.

scapulae, 8, 522.
ani, 240, 382.
glandulae thyroidese, 586.
labii inferioris, 557.
superioris, 555.

alaeque nasi, 552.
menti, 557.

Muscle or Musculus : —
levator palati, 662.

palpebree, 568, 643.
levatores costarum, 538.
linguales, 687.
longissimus dorsi, 526.
longus colli, 704.
lumbricales of foot, 205.
of hand, 75.
masseter, 607.
multifidus spinae, 534.
mylo-hyoid, 619.
naso-labial, 557.

obliquus abdominis extemus, 265.
internus, 269.
capitis inferior, 535.
superior, 535.
oculi, inferior, 650.
superior, 643.
obturator extemus, 123, 168.
internus, 121, 426.
occipito-frontalis, 502.
omo-hyoid, 9, 29, 522, 585.
opponens minimi digiti, 80.

pollicis, 77.
orbicularis oris, 556.

palpebrarum, 553.
orbitalis, 652.
palato-glossus, 663, 685.

pharyngeus, 658, 664.
palmaris brevis, 70.
longus, 62.
pectineus, 162.
pectoralis major, 18.
minor, 20.
peroneus brevis, 186.

longus, 185, 212.
tertius, 180.
perpendicular of tongue, 687.
pharyngeo-glossus, 686.
plantaris, 190.
platysma myoides, 573, 579.
popliteus, 193, 214.
pronator quadratus, 68.
radii teres, 60.
psoas magnus, 167, 368.

parvus, 369.
pterygoid, external, 610.
internal, 610.
pyramidalis abdominis, 274.

nasi, 552.
pyriformis, 118, 426.
quadratus femoris, 123.

lumborum, 370.
quadriceps extensor cruris, 155.
rectus abdominis, 272.

capitis anticus major, 705.
minor, 706.
lateralis, 636.
posticus major, 534.
minor, 535.
femoris, 117, 155.
oculi extemus, 649.
inferior, 649.
internus, 649.
superior, 643.
retrahens aurem, 500.
rhomboideus major, 8.

840

INDEX.

Muscle or Musculus : —

rhomboideus minor, 8.
risorius, 556.
rotatores dorsi, 535.
sacro-lumbalis, 526.
salpingo-pharyngeus, 664.
sartorius, 152.
scaleni, 589.

semimembranosus, 132, 214.
semispinalis colli, 533.
dorsi, 533.
semitendinosus, 132.
serratus magnus, 27.

posticus inferior, 523.
superior, 523.
soleus, 190.

sphincter ani externus, 240.
intemus, 240.
pupillse, 796.
vaginae, 256.
spinalis dorsi, 527.
splenius capitis, 524.

colli, 524.
stapedius, 811.
sterno-cleido-mastoid, 584.
hyoid, 585.
thyroid, 585.
stylo-glossus, 621, 685.
hyoid, 602.
Ijharyngeus, 626, 658.
subclavius, 21.
subcostal, 488.
subcrureus, 159.
subscapularis, 30.
supinator radii brevis, 89.
longus, 83.
supraspinatus, 37.
temporal, 506, 608.
tensor fasciae femoris, 155.
palati, 663.
tarsi, 553, 651.
tympani, 811.
teres major, 35.
minor, 35.
thyro-arytenoid, 691.

epiglottidean, 692.
hyoid, 586.
tibialis anticus, 178.

posticus, 194, 212.
trachelo-mastoid, 526.
of tragus, 570.

transversalis abdominis, 271.
colli, 526.
linguae, 686.
transverse of auricle, 670.
transverso-spinales, 533.
transversus pedis, 207.

perinei, 247, 257.
alter, 247.
profundus, 250,
258.
trapezius, 4.
triangularis stemi, 440.
triceps of arm, 51.
vastus externus, 156.
internus, 156.
zygomaticus major, 556.
minor, 556.

Musculi papillares, 461, 463.

pectinati, 458.
Musculo-cutaneous nerve. See Nerve,
phrenic artery. See Artery,
spiral nerve, 17, 53.
Mylo-hyoid artery. See Artery,
muscle. See Muscle,
nerve. See Nerve.

Nares, 668.

Nasal arteries. See Artery,
cartilages, 565.
duct, 671.
fossae, 667.
nerves. See Nerve.
Naso-palatine artery. See Artery.

nerve. See Nerve.
Nates, of brain, 773.
Neck, anterior triangle of, 580.
posterior, 574.
dissection of, 572.
Nerve or Nerves : —

abducent, 517, (o) 729.
accessory, 163, 374.

spinal, 517, (c) 578, 635
(d), (o) 730.
acromial cutaneous, 31, 579.
Arnold's, 633.

articular of popliteal, 129, 130.
auditory, 517, 680, (o) 729, 821 (d).
auricular anterior, 504.
great, 505, 578.
inferior, 617.
posterior, 504, 563.
superior, 104,
of vagus, 814.
auriculo-temporal, 504, 617.
buccal of facial, 564.

of inferior maxillary, 617.
calcaneo-plantar, 197.
cardiac inferior, (d) 473, 638.
middle, (d) 473, 638.
superior, (d) 473, 638.
of vagus, 471, 634.
cavernous, 417.

cervical, anterior branches, 596,
636, 705.
posterior branches, 520,
529, 705.
branch of facial, 580.
superficial, 579.
cervico-facial, 564.
chorda tympani, 618, 625, 680, 814.
ciliary, long, 645, 798.

short, 646, 798.
circumflex, 17, 25 (o), 31, 34 (c) (d).
clavicular, cutaneous, 13, 578.
coccygeal, 402, 537.
cochlear, 821, 822.
(ommunicating to descendens cer-
vicis, 599
fibular or peroneal,
130.
tibial, 129.
crural, anterior, 160, 373.
cutaneous, anterior, 13, 263.

INDEX.

841

Ner\-e or Nenes : —

cutaneous external, of arm. See
Musculo-
cutaneous.
of leg, 176.
of musculo-
spiral, 54, 57.
of thigh, 110,
140, 373.
internal of arm, large, 17,
42, 49, 56.
of ami, small,
13, 16, 17,
42, 49.
of musculo-

spiral, 43, 54.
of thigh, 141,
160, 187.
lateral, 13, 262.
middle, of thigh, 141, 160.
palmar, 66, 67.
plantar, 197.
radial, 57.
dental, anterior, 653.
inferior, 618.
middle, 653.
j)osterior, 652.
descendens cervicis, 602.
to digastric, 563.
digital, dorsal of toes, 176.
of median, 73.
■ palmar, 73.
plantar, 204.
of radial, 57.
of ulnar, 73.
dorsal, anterior branches, 274, 439,
488.
1 osterior branches, 538.
of clitoris, 259.
last, 110, 263, 274, 374.
of penis, 243, 251, 253.
of ulnar, 58, 67.
facial, 517, 561, 678, (o) 729.
frontal, 517.

genito-crural, 140, 277, 372.
glosso-pharyngeal, 517, 625, 631,688.
gluteal, inferior, 119, 403.
superior, 117, 403.
gustalorj'. (See Lingual,
heemorrhoidal, inferior, 242.
superior, 319.
of fourth sacral, 402.
hypoglossal, 517, 602, 603, 625, 635,
688, (o) 730.
ilio-hypogastric, 110, 263, 275, 372.

inguinal, 140, 264, 275, 372.
incisor, 618.

inframaxillary of facial, 564, 580.
infraorbital of facial, 563.

of fifth, 564, 652.
infratrochlear, 645.
intercostal, 274, 439, 488.
inlercosto-humeral, 43.
interosseus, anterior, 69.
posterior, 90.
of Jacobsou, 632, 812.
labial, inferior, 564.
superior, 564.

Nerve or Nerves : —

lachrymal, 517, 642.
laryngeal, external, 634.

infer 'or or recurrent, 471,
634, 697.
superior, 634, 697.
lingual, 618, 623, 688.
lumbar, anterior branches, 372.

posterior branches, 110, 531.
lumbo-sacral, 372.
malar of facial, 563.

of superior maxillary, 651.
masseteric, 617.
maxillary, inferior, 517, 616.
superior, 516, 652.
median, 17, 25 (o), 48 (o, c), 67 (c),

73 (d).
meningeal, 514.
mental, 564, 618.

musculo-cutaneous of arm, 25 (o),

42, 50 (c, o, d),

56 (c, d).

of leg, 176, 185.

spiral, 17, 25 (o), 42, 53 (o,c).

mylo-hyoid, 618.

nasal, 517, 642, 644, 646, 676, 677.
lateral, 564.

of Meckel's ganglion, 676.
nasopalatine, 673, 676.
obturator, 163, (o) 164, 374.

accessoi-y, 163, 374.
to obturator intemus, 118, 404,
occipital, great, 506, 520, 530.

small, 506, 578.
oculomotor, 16, 644, 648, (o) 728.
oesophageal, 472, 635.
olfactory, (o) 515, (d) 673, (o) 726.
ophthalmic, 516, 641.
optic, 515, 648, (o) 727.
orbital, of Meckel's ganglion, 676.
palatine, external, 676.
large, 676.
small, 676.
palmar, cutaneous, 70.
palpebral, 504, 564.
parotid, 617.
patellar, 141, 161.
to pectmeus, 160.

perforating cutareous, 112, 243,404.
perineal, 242, 248.

of fourth sacral, 243.
superficial, 246.
peroneal, 130.

communicating, 130.
petrosal, deep, large, 677.
small, 813.
superficial, external, 680.
large, 518, 677.
small, 518,

680, 813.
phai-yngeal, 632, 634, 665, 676.
phrenic, 450, 470, 599.
plantar, external, 204, 210.

internal, 204.
pneumo-gastric, (d) 338, (c) 471. 517,
632, (o) 730.
popliteal, external, 130.
internal, 129.

842

INDEX.

Nerve or Nerves ; —
prostatic, 384.
pterygoid, external, 617.

internal, 619, 681.
pudendal, inferior, (o) 119, (c) 246.
pudic, (c, d) 121, (o) 242, 258, 404.
pulmonary, 471.
to pyriformis, 121, 404.
to quadratus femoris, 121, 404.
radial, 57, 63, 67.
recurrent, articular, 185.

laryngeal, 471, 634.
• meningeal, 514.
to rhomboids, 10, 522, 598.
sacral, anterior branches, 401.

posterior branches, 110, 116,
536.
saphenous, external, 177, 187.

internal, 141, 161, 177,

187.
to scaleni, 598.
sciatic, great, 120, 133, 402.

small, 111, 119, 133, 187, 403.
to serratus, 27, 598.
spermatic, 282, 319.
spheno-palatine, 652.
spinal, 529, 542.

accessory, 517, (c) 578, 635 (d),
(o) 730.
splanchnic, large, 338. 371, 487.
small, 338, 371, 488.
smallest, 338, 371, 488.
splenic, 337.
to stapedius, 680, 814.
sternal cutaneous, 13, 578.
to stylo-hyoid, 563.
to subclavius, 598.
suboccipital, anterior branch, 636.
posterior branch, 530.
subscapular, 27.
supra-acromial, 31, 579.
supraclavicular, 31, 578.
supramaxillary of facial, 564.
supraorbital, 504, 641.
suprascapular, 9, 38, 522, 598.
supratrochlear, 504, 641.
sympathetic, in abdomen, 318, 336,
374.
in head, 518.
in neck, 636.
in pelvis, 404.
in thorax, 472, 486.
temporal, deep, 617.

of facial, 504, 563.
superficial, 504.
of superior maxillary, 504,
651.
temporo-facial, 563.
malar, 651.
to tensor palati, 681.

tympani, 681, 814.
vaginae femoris, 117.
to teres major, 27.
minor, 34.
thoracic, anterior, 25.

posterior, 27, 530.
thyroid, 638.
tibial, anterior 177, 185.

Nerve or Nerves : —

tibial, communicating, 129.

posterior, 196.
tonsillar, 632, 665.
trifacial or trigeminal, 516, (o) 728.
trochlear, 516, 641, (o) 728.
tympanic, 632, 812.
ulnar, 17, 25 (o), 49 (c), 58 (d),
66 (c, d), 73 (d), 81 (d).
uterine, 405.
vaginal, 405.

vagus, (d) 338, (c) 471, 517, 632,
(o) 730.
vesical, 405.
vestibular, 729.
Vidian, 676.

of Wrisberg, 13, 16, 17, 42, 49.
Nervi molles, 638.

Ninth nerve. See Glosso-pharyngeal Nerve.
Nipple of the breast, 14.
Nodule of cerebellum, 779.
Nose, cartilages of, 565.
cavity of, 667.
external, 565.
meatuses of, 671.
muscles of, 552.
nerves and muscles of, 673, 678.
regions of, 672.
Nostril, 565.
Notch of Rivinus, 808.
Nuck, canal of, 276.
Nuclei arciformes, 738.

of cranial nerves, 783.
of medulla oblongata, 737.
of optic thalamus, 770.
pontis, 740.
Nucleus, amygdaloid, 762.
caudate, 766.
of funiculus cuneatus, 737.

gracilis, 737.
lateral, 737.
of lens, 802.
lenticular, 766.
olivary, 737.

superior, 740.
red, of tegmentum, 743.
Nymphae, 255.

Oblique ligament. See Ligament,
muscles. See Muscle,
vein of heart. See Vein.
Obturator artery, 168.

fascia. See Fascia,
membrane, 431.
muscles. See Muscles,
nerve, (o) 164.
Occipital artery. See Artery.

lobe of cerebrum, 748, 751.
lobule, 754.
nerves. See Nerve,
sinus. See Sinus,
veins. See Veins.
Occipito-atlantal articulations. See Articu-
lation,
ligaments. See Liga-
ment,
axial ligaments. See Ligament,
frontalis muscle. See Muscle.

INDEX.

843

Occipito-temporal convolutions, 755.
Oculomotor nerve. See Nerve.
Odontoid ligaments. See Ligaments.
(Esophagus, relations of, 484, 607.
structure of, 484, 665.
CEsophageal arteries. See Artery,
groove in liver, 347.
nerves. See Nerves,
opening of diaphragm, 361.
Oliactorj' bulb, 744.
cleft, 667.
lobe, 726, 744.
nerves, 726, 744.
region of nose, 672.
striae, 744.
sulcus, 744, 750.
tract, 744.
tubercle, 745.
Olivary body, 725, 732, 737.
nucleus, 737.

superior, 740.
peduncle, 737.
Omental tuberosity of liver, 347.

of pancreas, 330.
Omentum, gastro-colic or great, 311.

hepatic or small, 304.
310.
splenic, 306, 311.
Omo-hyoid muscle, 9.
Operculum, 748.

Ophthalmic artery. See Artery,
ganglion, 646.
nerve. See Nerve,
veins. See Vein.
Opponens. See Muscle.
Opposition of thumb, 103.
Optic commissure, 727.
disc, 799.

ner^-e. See Nerve,
papilla, 799.
thalamus, 769.
tract, 725, 727, 772.
Ora serrata, 799.

Orbicular ligament of the radius. See
Ligament.
Orbicularis oris. See Muscle.

palpebrarum. See Muscle.
Orbit, 639.

muscles of, 643,
nerves, 640.
periosteum of, 640.
vessels, 646.
Orbital branch of artery. See Artery,
branches of nerve. See Nerve,
lobule, 747, 750.
sulcus, 750.
Orbitalis muscle. See Muscle.
Organof Corti, 819.

of Giraldes, 282.
of Rosenmiiller, 424.
Orifice, of the urethra, 410.
of the uterus, 420.
of the vagina, 255.
Orifices, auriculo- ventricular, 461, 463.

of the stomach, 339.
Ossicles of the tympanum, 809.
Ob tincae, 420.

uteri externum, 420.

Otic ganglion. See Ganglion.

Otoliths, 820.

Oval lobule, 754,

Ovarian artery. See Artery.

plexus of nerves. See Plexus,
vein. See Vein,
Ovary, 394, 423.

appendage to, 424.

vessels of, 424,
Ovisacs, 423.

Pacchionian bodies, 507.

Palate (soft), 661,

Palatine arteries. See Artery.

nerves. See Nerve,
Palato-glossus. See Muscle.

pharyngeus. See Muscle,
Palm of the hand, 69,
Palmar arch, deep, 80.

superficial, 71.
cutaneous nerves, 66, 67.
fascia, 70.
Palmaris. See Muscle.
Palpebrse, 566.

Palpebral arteries. See Artery,
fascia or ligament, 568,
fissure, 566,
nerves. See Nerve,
veins. See Vein,
Pampiniform plexus, 282, 424.
Pancreas, 329,

relations of, 327.
structure of, 342.
Pancreatic arteries. See Artery,
duct, 342.
veins. See Veins.
Pancreatico - duodenal arteries. See

Artery.
Papilla lachrymalis, 566.

optica, 799.
Papillae of the kidney, 355.
of the tongue, 683.
Paracentral lobule, 764.
Paradidymis, 282.
Parallel sulcus, 752.
Para-rectal fossa, 377.

vesical fossa, 378.
Parietal lobe, 747, 750.

lobules, 750.
Parieto-occipital fissute, 747, 753.
Parotid arteries, 606,

fascia. See Fascia,
gland, 559.

lymphatic glands, 561.
nerves. See Nerves,
Parovarium, 424.
Passage, anal, 387,
Patellar nerve, 141, 161.

plexus, 141,
Pecten of Reil, 774.
Pectineus muscle, 162.
Pectoralis. See Muscle.
Peduncle of the cerebellum, inferior, 725,

781.
middle, 781.
superior, 771,
780.

IXDKX.

Peduncle of the cerebrum, 725, 741.
of the corpus callosum, 744.
oHvary, 737.
Peduncular fibres, 773.
Pelvic colon, 304.
Pelvis, dissection of, 376.

muscles and ligaments of, 425.
of ureter, 357.
vessels and nerves of, 395.
viscera of, female, 390, 418.
male, 384.
Pelvic cavity, 376.

diaphragm, 381.
fascia, 376.
plexus, 404,
Penis, 253.

integument of, 252.
structure of, 415.
vessels of, 416.
Perforated space, anterior, 726, 744.
posterior, 725, 743.
Perforating arteries. See Artery,
cutaneous nerve, 112.
Pericardium, 449.
Perilymph, 816.
Perineum, female, 255.

male, 236.
Perineal artery, superficial. See Artery,
transverse. See Artery,
fascia, deep. See Fascia.

superficial. See Fascia,
nerves. See Nerves.
Periosteum of the orbit, 640.
Peritoneal prolongation on the cord, 276.
Peritoneum, 276, 293, 307.

of female pelvis, 390.
of male pelvis, 376.
Peroneal artery. See Artery.

nerve. See Nerve.
Peroneus. See Muscle.
Peroneo-tibial articulations. See Articula-
tion.
Perpendicular fissure. See Fissure,
muscle of tongue. See

Muscle.
Pes hippocampi, 761.
Petit, canal of, 801.
Petrosal ganglion. See Ganglion,
nerves. See Nerve,
sinuses. See Sinus.
Peyer's glands. See Glands.
Pharynx, 654.

interior of, 658, 661.
muscles of, 655.
openings of, 658.
Pharyngeal, ascending, artery. See

Artery,
nerves. See Nerves,
tonsil, 665.
veins. See Veins.
Pharyngeo-glossus muscle. See Muscle.
Phrenic arteries. See Artery,
nerve. See Nerve,
plexus. See Plexus.
Pia mater of the brain, 717.

of the cord, 541.
Pigmentary layer of retina, 799.
Pillars of the abdominal ring, 267.

Pillars of diaphragm, 359.

of the fornix, 760, 770.
of the iris, 793.
of the soft palate, 661.
Pineal body, 772.
stria, 769.
Pinna, or auricle of the ear, 569.
Pituitary body, 743.

membrane. See Membrane.
Plantar aponeurosis or fascia, 198.
arch of artery. See Artery,
arteries. See Artery,
ligament. See Ligament,
nerves. See Nerves.
Plantaris muscle. See Muscle.
Platysma myoides muscle. See Muscle.
Pleura, 442.
Pleuro-colic fold, 312.
Plexus of nerves : —

aortic, 319.

brachial, 25, 596.

cardiac, deep, 472.

superficial, 457.

carotid, 518.

cavernous, 518.

cervical, 678, 598.

coeliac, 337.

coronary of heart, 457.

of stomach, 337.

cystic, 338.

diaphragmatic, 337.

epigastric, 336.

guise, 472.

liaemorrhoidal, 404.

hepatic, 337.

hypogastric, 319, 395, 404.

infraorbital, 563.

lumbar, 110, 371, 372.

mesenteric, inferior, 319.
superior, 318.

ovarian, 405.

pancreatico-duodenal, 338.

patellar, 141.

pelvic, 404.

pharyngeal. See Nerves.

phrenic, 337.

prostatic, 405.

j)ulmonary, 472.

pyloric, 337.

renal, 337.

sacral, 402.

solar, 336.

spermatic, 282, 319.

splenic, 337.

suprarenal, 337.

tympanic, 812.

uterine, 405.

vesical, 405.

vertebral, 639, 707.
Plexus of veins : —

alveolar, 616.

basilar, 514.

choroid, 717, 763, 783.

dorsal, of hand, 56.

hfemorrhoidal, 400.

ovarian, 367.

pampiniform. See Spermatic.

prostatic, 384.

I2CDEX.

845

Plexus of veins : —

pteiTgoid, 615.
spennatic, 277, 282, 367.
uterine, 400.
vaginal, 400.
vesical. 400.
Plica fimbriata, 683.

semilunaris, 569.
Pueumo-gastrie nerve. See Nerve.
Pomum Adami, 572.
Pons Varolii, 725, 731, 738.
Popliteal arterv, 126.
glands, 130.
nerves, 129.
space, 125.
vein, 129.
Popliteus muscle. See Muscle.
Portal fissure, 347.

vein. See Veins.
Portio dura, 729.

intermedia, 729.
mollis, 729.
Porus opticus, 799.
Posterior column of cord, 547.
commissure, 772.
pyramid, 733.
triangle of the neck. See

Triangle.
Postcentral sulcus. See Sulci Cerebrum,
Poupart's ligament, 143, 267.
Pouch, larjTigeal, 694.

recto-uterine, 376.
vesical, 376.
vesico-uterine, 391.
Praecentral sulcus, 749.
Praeputium clitoridis, 255.
Prepuce, 252.
Prevertebral muscles, 704.
Processus vaginalis, 289.
Profunda arterj-. See Artery.
Promontorj', 805.
Pronator. See Muscle.
Prostate gland, 388, 406.

relations, 388.
sheath of, 389.
structure, 406.
Prostatic part of urethra, 389, 412.
plexus, of nerves, 405.

of veins, 384.
sinus, 413.
Psoas magnus muscle, 167, 368.
Psoas parvus muscle, 369.
Pterygoid arteries. See Ar'.eries.
muscles. See Muscle,
nerves. See Nerve,
plexus of veins, 615.
Pterygo-maxillary ligament. See Liga-
ment,
region, 607.
palatine artery. See Artery.
Pubes, 260.
Pubic part of fascia lata, 142.

region of the abdomen, 298.
symphysis, 429.
Pubo femoral ligament, 170.
Pudendal, inferior, nerve. See Nei"^e.
Pudendum, 255.
Pudic arteries. See Arterv.

Pudic nerve. See Nerve.
Pulmonary artery. See Artery,
nerves. See Nerve,
orifice and valve, 461.
veins. See Veins.
Palvinar, 770.
Puncta lachrymalia, 566.
Pupil, 796.
Pylorus, 340,

Pyloric arterv. See Artery,
orifice, 339.
plexus, 337.
vein. See Vein.
Pyramid, anterior, 725, 731.
decussation of, 731.
of the cerebellum, 779.
of the thyroid body, 586.
of the tympanum, 807.
Pyramidal masses of kidney, 355.

tract, 734, 740.
Pyramidalis. See Muscle.
Pyramids of Malpighi, 355.
Pyriformis muscle, 118.

fascia of. See Fascia.

Quadrate lobe of cerebellum, 777,
of liver, 347.
lobule of cerebrum, 754.
Quadratus. See Muscle.
Quadriceps extensor cruris, 155,
Quadrigemiual bodies, 771.
Quadrilateral space, 35.

Radial artery, 62, 80, 90.
ner\-e, 57, 63, 67,
veins, 63.

veins, cutaneous, 56,
Radio-carpal articulation, 98.

ulnar articulations, 97, 100.
Ranine artery. See Artery,

vein. See Vein.
Raphe of the corpus callosnm, 756,

of the medulla oblongata, 737.
of the palate, 666.
of the perineum, 237.
of the pons, 740.
of the to igue, 682.
Receptaculum chyli, 371.
Recto-uterine ligaments, 391,
pouch, 376.
vaginal pouch, 376.
vesical fascia, 380, 383.
pouch, 376,
Rectus. See Muscle.
Rectum, relations of, in the female, 392.

in the male, 304, 386.
structure, 417.
Recurrent arteries. See Artery.

nerve. See Nerve.
Red nucleus, 743.
Regions, of abdomen, 297.
Reil, covered band of, 756.
island of, 748, 752.
pecten of, 774.
sulci of, 748.
Reissner, membrane of, 879.
Renal artery. See Artery.

846

INDEX.

Kenal impression on liver, 347,

plexus. See Plexus.

vein. See Vein.
Respiratory glottis, 693.

region of nose, 672.
Restiform body, 725, 738.
Eete testis, 280.
Reticular formation, 737, 740.
Retina, 798.

Retinaeula of ileo-csecal valve, 325.
Retrahens aurem. See Muscle.
Retro-colic fold, 313.
Rhomboid ligament. See Ligament.
Rhomboidei muscles, 8.
Rima glottidis, 693.

of the vulva, 255.
Ring, abdominal, external, 266, 288.
internal, 275, 288.

crural or femoral, 146.
Risorius muscle. See Muscles.
Riviuus, ducts of. See Ducts.

notch of, 808.
Rolando, funiculus of. See Funiculus,
sulcus of, 747.
tubercle of, 732.
Roof-nucleus of cerebellum, 780.
Root of the lung, 448.
Roots of the nerves, 542.
Rosenmiiller, organ of, 424.
Rostrum of corpus callosum, 744.
Rotatores dorsi. See Muscle.
Round ligament. See Ligament.

Saccule of the ear, 821.
Sacculus laryngis, 694.
Saccus endolymphaticus, 821.
Sacral arteries. See Artery.

ganglia, 404.

nerves. See Nerve.

plexus. See Plexus.
Sacro-coccygeal articulation, 427.

genital fold, 377.

iliac articulation, 429.

lumbalis muscle. See Muscle.

sciatic ligaments, 124.
Salpingo-pharyngeus muscle. See Muscle.
Santorini, cartilages of, 700.
Saphenous nerves. See Nerve,
opening, 142.
veins. See Vein.
Sartorius muscle, 152.
Scala tympani, 819.

vestibuli, 819.
Scaleni muscles. See Muscles.
Scapular arteries. See Artery,
ligaments, 37.
muscles, 34, 37.
Scapulo-humeral articulation, 92.
Scarpa, fascia of, 146.

triangle of, 146.
Schneiderian membrane, 671.
Sciatic artery, 118.

nerves. See Nerve.
Sclerotic coat of the eye, 791.
Scrotum, 252.
Second nerve. See Nerve.

Secondary membrane of the tympaliUhi,

808.
Semicircular canals, 815.

membranous, 820.
Semilunar cartilages, 218.

fold of Douglas, 274.
ganglia, 337.
Semi-bulbs of vestibule, 257.
Semimembranosus muscle, 132.
Seminal ducts, 389.
Seminiferous tubes, 280.
Semispinalis muscle. See Muscle.
Semitendinosus muscle, 132.
Septum cochleae, 818.

crurale, 146, 293.
intermuscular, of the arm, 52.

of the leg, 177, 185,
188, 192.
of the sole, 198.
of the thigh, 159.
lucidum, 760.
narium, 668.
nasi, 668.
pectiniforme, 416.
posterior median of spinal cord,

546.
intermediate, 549.
posticum of arachnoid, 541.
scroti, 252.
of the tongue, 683.
Serratus. See Muscle.
Seventh nerve. See Nerve.

nucleus of, 729, 784.
Sheath, axillary, 20.
crural, 143.
of the fingers, 71.
of the prostate, 406.
of the rectus, 273.
of the toes, 199.
Shoulder- joint, 92.
Sigmoid artery. See Artery.
Sinus, of the aorta, 466.
basilar, 514.
of the bulb, 413.
cavernous, 513.
circular, 513.
circularis iridis, 792.
coronary, 456.
frontal, 670.
intercavernous, 513.
of the kidney, 353.
lateral, 511.

longitudinal, inferior, 511.
superior, 508.
occipital, 511.
petrosal, inferior, 513, 629,

superior, 513.
pocularis, 412.
prostatic, 413.
sphenoidal, 671.
straight, 511.
of Valsalva, 462.
venosus, 457.
Sixth nerve. See Nerve.

nucleus of. See Nucleus.
Slender lobe of cerebellum, 777.
Small intestine, 321.
omentum, 310.

INDEX.

847

Socia parotidis, 560.

Scemmering's enumeration of the cranial

nerves, 726.
Soft commissure, 766.
palate, 661.

muscles of, 662,
Solar plexus, 318.
Sole of the foot, dissection of, 197,
Soleus muscle. See Muscle.
Solitary glands, 323.
Spermatic artery. See Artery,
cord, 276.
' fascia, 267,

plexus of nerves. See Plexus,
veins. See Veins,
Sphenoidal sinus. See Sinus.
f Spheno-ethmoidal recess, 671,
I palatine artery. See Artery,

ganglion. See Ganglion,
nerves. See Nerves,
Sphincter. See Muscle.
Spigehan lobe, 347.
Spinal accessory nerve. See Nerve,
nucleus, 730.
arteries. See Artery,
column, movements of, 497.
cord, 638, 545.

membranes of, 539.
structure of, 547.
vessels of, 545.
nerves. See Nerves.

posterior branches of. See

Nerves,
roots of. See Root,
veins. See Vein.
Spinalis dorsi muscle. See Muscle.
Spiral ganglion. See Ganglion,
ligament. See Ligament,
tube of the cochlea, 817.
Splanclinic nen^es. See Nerve.
Spleen, 306.

relations of, 306.
structure of, 343.
Spleniculi, 343.
Splenic artery, 332.

flexure of colon, 302.
plexus of nerves. See Nerves,
vein. See Vein.
Splenium of corpus callosum, 756.
Splenius muscle. See Muscle,
Spongy bones, 669.

part of the urethra, 390, 413.
Stapedius muscle. See Muscle,
Stapes bone, 810.

Stellate ligament. See Ligament,
Stenson's duct, 560.
Sternal arteries. See Arteries.

cutaneous nerves. See Nerves.
Stemo-clavicular articulation. See Articu-
lation,
cleido-mastoid muscle. See Muscle,
hyoid muscle. See Muscle,
mastoid artery. See Artery,
thyroid muscle. See Muscle.
Stomach, form and divisions of, 338.
relations of, 300, 330.
structure of, 339,
Straight sinus. See Sinus.

Striate body, 766.

Striae longitudinales of corpus callosum,

756.
Stylo-glossus muscle. See Muscle.

hyoid ligament. See Ligament,
muscle. See Muscle,
nerve. See Nerve,
mastoid artery. See Artery,
maxillary ligament. See Ligament,
pharyngeus muscle. See Muscle.
Subarachnoid space of the brain, 716.
of the cord, 541.
Subclavian artery, left. See Artery,
right. See Artery,
vein. See Vein.
Subclavius muscle, 21,
Subcostal muscles, 488.
Subcrureus, 159.
Subdural space, 508, 716,
Sublingual artery. See Artery.

gland, 625,
Submaxillary ganglion, 624.
gland, 619.
lymphatic glands. See

Glands,
region, 619.
Submental artery See Artery.
Suboccipital lymphatic glands. See

Glands,
nerve. See Nerve,
triangle, 535.
Subpeduncular lobe, 778.
Subperitoneal fat, 276, 293.
Subpubic ligament. See Ligament.
Subscapular artery, 24.
nerves, 27.
Subscapularis muscle, 36.
Substantia ferruginea, 783,
gelatinosa, 737,
nigra, 742.
Sulci of cerebrum, 745.

of spinal cord, 546.
Sulcus spiralis, 819.

Superficial cervical artery. See Artery,
fascia of the abdomen, 261,
of the perineum, 244,
of the thigh, 136.
volar artery. See Artery.
Supinator. See Muscle.
Supra-acromial nerves, 31.
Supraclavicular fossa, 572.

nerves. See Nerves..
Supramarginal convolution, 751,
Supramaxillary nerves. See Nerves.
Supraorbital artery. See ArteTj.

nerve. See Nerve.
Suprarenal capsule, 357.

impression on liver, 347-
plexus, 337.
Suprascapular artery, 9, 38.
ligament, 37.
nerve, 9, 38.
vein. See Vein.
Supraspinatus muscle, 37.
Suprasternal fossa, 572.
Supratrochlear nerve. See Nerve.
Suspensory ligament. See Ligament.
Sylvius, aqueduct of 773

848

INDEX.

Sylvius, fissure of, 745.
valley of, 744.
Sjrmpathetic nerve. See Nerve.
Symphysis pubis, 429.

Taenia hippocampi, 761.-

semicircularis, 769
Tarsal artery. See Artery.

articulations. See Articulations,
fibrous plates, 568.
glands. See Glands,
ligaments of eyelids, 568.
Tarso-metatarsal articulations. See Articu-
lation.
Tarsus of eyelid, 568.
Teeth, 666.
Tegmen tympani, 807.
Tegmentum, 742.
Temporal aponeurosis, 506.

arteries. See Artery,
fascia, 506.
muscle. See Muscle,
nerves. See Nerve,
veins. See Vein.
Temporo-facial nerve. See Nerve,
malar nerve. See Nerve,
maxillary articulation. See

Articulation,
vein. See Vein,
sphenoidal lobe, 748, 752.
Tendo Achillis, 190

palpebrarum, 568.
Tendon, infrapatellar, 158.
suprapatellar, 157.
Tensor. See Muscle.
Tenth nerve. See Nerve.
Tentorium cerebelli, 610.
Teres muscles, 35.
Testes, 277.

of brain, 771.
Thebesian foramina, 459.

valve, 459.
Thigh, dissection of, back, 130.
front, 136.
Third nerve. See Nerve.

nucleus of, 728.
ventricle, 764.
Thoracic arteries. See Artery,
duct, 371, 485, 595.
ganglia, 470.
nerves. See Nerve.
Thorax, boundaries of, 437.
parietes of, 436, 488.
upper aperture of, 639.
Thymus body, 446.

Thyro-arytenoid ligaments. /S^^; Ligament.
muscle. See Muscle,
epiglottidean ligament. See

Ligament:
muscle. See Muscle,
hyoid membrane. See Membrane,
muscle. See Muscle.
Thyroid arteries. See Artery,
axis, 594.
body, 586.
cartilage, 698.
veins. See Vein.

Tibial arteries. See Artery,
nerves. See Nerve,
veins. See Vein.
Tibialis. See Muscle.
Tibio-tarsal articulation, 222.
Tongue, 682.

muscles of, 684.
nerves of, 688.
structure of, 683.
vessels of, 688.
Tonsil, 665.
Tonsillar artery. See Artery.

nerves, 665.
Torcular Herophili, 508.
Trabeculse carnese, 460.
Trabecular structure of penis, 415.

of spleen, 343.
Trachea, relations of, 477, 606.

structure of, 703.
Tracheal nerves, 704.
Trachelo-mastoid muscle. See Muscle.
Tract, direct cerebellar, 736.
lateral, 732, 736.
olfactory, 744.
optic, 727, 772.
pyramidal, 734, 740.
Tragus, 569.

muscle of, 570.
Transverse articles of po is. See Artery,
carpal articulation, 101.
cervical artery, 9.
colon, 302.

facial artery. See Artery,
fissure of the cerebrum, 762.

of the liver, 347.
ligament. See Ligament,
muscle. See Muscle,
perineal artery. See Artery,
tarsal articulation, 228.
vesical fold, 378.
Transversalis or transversus muscle. See

Muscle,
fascia, 275.
Transverso-spinales muscles. See Muscle.
Trapezius muscle, 4.
Trapezoid ligament, 36.
Triangle of Hesselbach, 290.

of the neck, anterior, 580.

posterior, 574.
of Scarpa, 146.
suboccipital, 535.
Triangular fascia, 268.

fibro-cartilage of wrist, 100.
ligament of the urethra, 248.
space of the thigh, 146.
surface of the bladder, 389.
Triangularis sterni muscle. See Muscle.
Triceps extensor cubiti, 51.
Tricuspid valve, 461.

Trifacial or trigeminal nerve. See Nerve.
Trigonum vesicas, 411.
Trochlea, 643.

Trochlear nerve. See Nerve.
Tube, of the cochlea, 817.

Eustachian, 660, 808.
Fallopian, 394, 424.
Tuber cinereum, 726, 743.
valvules, 779.

INDEX.

849

Tubercle, amygdaloid, 762.
of epiglottis, 700.
of Lower, 457.
olfactory, 745.
of optic thalamus, 769.
of Rolando, 732.
Tuberculum cinereum, 726.
euneatum, 733.
Tubuli recti, 280.

seminiferi, 280.
Tunica albuginea testis, 279.
propria of spleen, 343.
Ruyschiaua, 795.
vaginalis, 278.

oculi, 790.
vasculosa testis, 279.
Turbinate bones, 669.
Twelfth cranial nerve. See Nerve,
dorsal nerve. See Nerve.
Tympanic artery. See Arteiy.

membrane. See Membrane,
nerve. See Nerve.
Tympanum, 805.

arteries of, 812.
lining membrane of, 811.
nerves of, 812.
ossicles of, 809.

Ulnar artery, 64, 71.

nerve, 17, 49, 58, 65, 66, 73.
veins, 65.

cutaneous, 56.
Umbilical hernia, 291.

region of the abdomen, 298.
vem. See Vein.
Umbilicus, 260.
Uncinate convolution, 755.
Uncus, 755.
Ureter, 356, 395.
Urethra, female, orifice of, 39o.

relations of, 395.
structure of, 425.
male, interior of, 425.
relations of, 389.
structure of, 390, 411.
Uterine arteries. See Artery.

plexus of nerves. See Plexus,
veins and sinuses, 400.
Uterus, 392.

interior of, 421.
ligaments of, 392.
relations of, 392.
structure of, 421,
Utricle of the ear, 820.

of the urethra, 412.
Uvea iridis, 796.
Uvula cerebelli, 778.
palati, 661.
vesicae, 411.

Vagina, relations, 394.

structure and form, 419.
Vaginal arteries. See Artery.

ligaments, 71.

nerves, 405.

veins, 400.

D.A.

Vagus nerve. See Nerve.

nucleus, 730, 784.
Vallecula of cerebellum, 777.

Sylvii, 726, 744.
Valsalva, sinuses of. See Sinuses.
Valve, aortic, 473.

Eustachian, 459.
ileo-colic, 325.
mitral, 463.
pulmonary, 461.
of Thebesius, 459.
tricuspid, 461.
of Vieussens, 771, 781.
Valvulae conniventes, 322.
Vas aberrans, 282.

deferens, 277, 281, 389, 408.
Vasa aberrantia, 47.
brevia, 332.
efferentia testis, 280.
recta testis, 280.
vorticosa, 798.
Vastus extemus muscle, 156.
intemus muscle, 156.
Vein or Veins : —

alveolar, 616.
angular, 503.
ascending lumbar, 483.
auditory, 822.

auricular, posterior, 503, 60b.
axiUarv, 17, 24.
azvgos, large, 371, 375, 483.
' smaU, 371, 375.

superior left, 483.
basilic, 41.
bracliial, 48.
brachio-cephalic, 469.
bronchial, 480, 483.
cardiac, 456.
cava, inferior, 320, 367, 469.

superior, 468.
cephalic, 16, 42.
cerebellar, 724.
cerebral, 724.
choroid, 764.
ciliary, anterior, 798.
posterior, 798.
circumflex iliac, 139, 285.
coronary of the heart, 456.

of the stomach, 334.
of the corpus cavernosum, 416.

striatum, 766.
cystic, 333.
deep cervical, 533.
diaphragmatic, inferior, 368.
dorsal, of the penis, 253, 400.
dorsal spinal, 533.
emissary, 503.
emulgent, 367.
epigastric, deep^84

superficial, loy.
facial, 559, 605, 629.

deep, 559, 605, 616.
femoral, 149.
frontal, 503.
of Galen, 764.
gastro-epiploic, left, 335.

right, 333.
hsemorrhoidal, 400.

3 I

550

INDEX.

Vein or Veins : —

hepatic, 350, 368.
iliac, common, 367.
external, 366
internal, 399.
ilio-lumbar, 397.
infraorbital, 653.
innominate, 469.
intercostal, 483.

highest, 484.
superior, 484.
interlobular, 350.
intralobular, 350.
intraspinal, 550.
jugular, anterior, 584.
external, 574.
internal, left, 629.

right, 600, 629.
laryngeal, 697.
lingual, 623, 629.
longitudinal, of the spine, 550.
lumbar, 368, 375, 533.
mammary, internal, 441.
maxillary, internal, 615.

anterior, internal, 559.
median, of the forearm, 41, 56.
basilic, 41.
cephalic, 41.
mesenteric, inferior, 318.
superior, 316.
oblique, of heart, 456.
occipital, 503, 533, 605.
ophthalmic, 648.
ovarian, 367.
palpebral, 559.
pancreatic, 335.
perineal, superficial, 245.
pharyngeal, 630, 665.
phrenic, inferior, 368.
popliteal, 129.
portal, 335.

profunda of the thigh, 166.
pterygoid plexus, 615.
pubic, 399.
pudic, external, 139.

internal, 119, 251, 400.
pulmonary, 469, 480.
pyloric, 335.
radial, 63.

cutaneous, 56.
ranine, 623.
renal, 356, 367.
sacral, middle, 400.
saphenous, external, 176, 187,

internal, 139, 176, 187.
spermatic, 277, 282, 367.
spinal, posterior, 550.
of the spinal cord, 545.
splenic, 335, 343.
subclavian, 595.
sublingual, 623.
sublobular, 350.
supraorbital, 603.
suprarenal, 368.
suprascapular, 38, 622.
temporal, 603, 605.
temporo-maxillary, 561, 603, 606.
thyroid, inferior, 687.

Vein or Veins : —

thyroid, middle, 587, 629.

superior, 587, 604, 629.
tibial, anterior, 184.
posterior, 196.
transverse cervical, 622.
ulnar, 65.

cutaneous, 66.
umbilical, 348.
uterine, 400.
vaginal, 400.
vertebral, 533, 594, 707.
anterior, 707.
of the vertebrae, 550.
vesical, 400.
Velum interpositum, 717, 767.

pendulum palati, 661.
Vena cava, inferior, 320, 367, 469.
superior, 468.
portae, 335.
Venae cavae hepaticae, 350, 368.
Venous arch of the foot, 176.
Ventricles of the brain, 758.

fifth, 760.
fourth, 781.
lateral, 758.
third, 764.
of the heart, 455.

left, 463.
right, 459.
structure of, 473.
of the larynx, 694.
Vermiform appendix, 302, 324.

processes, 776, 779, 781.
Vermis, 776.
Vertebral aponeurosis, 524.

artery. See Artery,
plexus, 707.
veins, 707.
Verumontanum, 412.
Vesica urinaria. See Bladder.
Vesical arteries. See Artery.

plexus of nerves. See Plexus,
veins. See Veins.
Vesico-uterine ligaments, 391.

pouch, 391.
Vesicula prosta-tica, 412.
Vesiculae seminales, relations of, 389.
structure of, 407,
Vestibule of the ear, 814,

artery of. See Artery,
nerves of. See Nerves,
of the mouth, 666.
of the nose, 671.
of the vulva, 255.
Vestigial fold of pericardium, 451.
Vibrissae, 672,
Vidian artery. See Artery.

nerve. See Nerve.
Vieussens, annulus or isthmus of, 458.
ansa of, 638.
valve of. See Valve.
Villi, intestinal, 321.
Vincula accessoria, 75.
Vitreous body, 800.
Vocal cords, 696,

glottis, 693.
Vulva, 255.

INDEX.

8.^1

Wharton's duct, 625.

White commissure of the cord, 548.

line of pelvic fascia, 383.
Willis, circle of, 724.
Windpipe. See Trachea.
Winslow, foramen of, 309, 311.
Wirsung, canal of, 342.
Worm of cerebellum, 776.

Wrisberg, ne^^'e of, 13, 16, 17, 42, 49.

Wrist-joint, 98.

Yellow spot of eyeball, 799.

Zonule of Zmn, 800.
Zygomatic muscles.

See Muscles.

THE END.

BRADBURY, AGNEW, & CO. LD., PRINTERS LONDON AND TONBRIDGE.

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