ET BR RY

New York State Veterinary College

ITHACA, NEW YORK

Hopkins, Grant Sherman

A guide to the dissection of the blood
vessels and nerves of the pectoral and pelvic
limbs of the horse.

DATE DUE

Se

a

GAYLORD PRINTEDINU

A GUIDE

<i

_ Dissection an the Blood Vestls
ie and | Ne ae

OF: THE

SOE.

: A Guairk SHERMAN Horxins, | :
: New York State Vetetinasy College at Cornell University,
A -‘Trmaca. NwY... :

24

TO THE ? | eed

oll

THIS BOOK IS THE GIFT OF

Dr GS. Horkins.

A GUIDE

TO THE

Dissection of the Blood Vessels
and Nerves

OF THE

PECTORAL AND PELVIC
LIMBS

OF

THE HORSE

BY

GRANT SHERMAN HOopkINs,
New York State Veterinary College at Cornell University,

Irwaca, N. Y.

COPYRIGHT I914
BY GRANT SHERMAN HOPKINS

Cornell University

Library

The original of this book is in
the Cornell University Library.

There are no known copyright restrictions in
the United States on the use of the text.

http://www.archive.org/details/cu31924001090483

PREFACE

Every teacher who has had experience with classes in Anatomy appre-
ciates the difficulties that confront the student in his attempt to dissect
any portion of the body with only his text-book of Descriptive Anatomy,
for a guide. The present ‘‘Guide’’ has been prepared in the hope of assist-
ing students in the dissection of the blood-vessels and nerves of the pec-
toral and pelvic limbs. A knowledge of the muscles is presupposed. In
our experience, we have found it most desirable that, upon the completion
of a part, the student should demonstrate his dissection to the instructor
in charge. By no other means can the student be brought to realize
more clearly the vast difference between studying and knowing the actual
object itself and the mere memorizing the description of it as given in

his text-book.
G. S. H.

Dissection of the Blood-Vessels and Nerves of
the Arm or Pectoral Limb

Cut the skin along the median line from the xiphoid cartilage to a point
15 or 20 cm. cephalad of the presternum; also cut at a right angle to this
along the middle of the proximal half of the antebrachium and reflect the
skin from the pectoral muscles. Note the large vein (V. cephalica) and the
small artery lying in the groove formed by the anterior superficial pectoral
muscle and the adjoining border of the M. mastoido-humeralis. Transect
the two superficial pectorals close to their sternal attachments. Now
dissect up the cervical panniculus, transect it a short distance from its
attachment to the sternum and turn it aside. Beneath this portion
of the panniculus is a mass of fatty tissue in which are numerous lymph
nodules—the Prescapular or superficial cervercal lymph gland. The full
extent of this gland may be seen when the M. mastoido-humeralis is turned
aside. Transect the mastoido-humeralis a little above (cephalad) the °
point of the shoulder and turn it aside sufficiently to expose the underlying
prescapular portion of the anterior deep pectoral muscle and the prescapular
lymph gland. Do not disturb unnecessarily the gland for beneath it
are an artery and vein of some surgical importance. Trace the large
vein (V. cephalica) and the small artery (a branch of the A. cervicalis
inferior) that cross the anterior deep pectoral muscle in the groove between
this muscle and the mastoido-humeralis, in so far as the vessels are at
present accessible. Ligate and cut the vessels. Abduct the arm somewhat
and identify the two deep pectoral muscles. Transect the latter muscles close
to their attachment to the sternum. Abduct the arm a little and dissect
between the deep pectoral muscles and the thoracic wall until the large A.
and V. Axillaris are exposed. Carefully clean up the V. Axillaris noting
meantime the lymph glands, Posterior cervical or prepectoral, that he
just cephalad or anterior to the V. Axillaris. Cut the vein in order clearly
to expose the A. Axillaris which lies immediately dorsal to it. Clean up
the A. Axillaris taking care not to cut any of its branches or the nerves that
cross the ventral surface of the artery a short distance (4 to 6 cm.) from the
first rib. Cut the artery close to the rib. Occasionally a large vein lies
just anterior to the A. Axillaris; if so, this also should be cut.

A. cervicalis inferior arises from the axillaris nearly opposite the first rib.
Near the ventral border of the M. scalenus it divides into two nearly equal
branches—a ventral and a dorsal branch. The ventral branch crosses

6

the superficial surface of the anterior deep pectoral and then runs in the
groove formed by this muscle and the mastoido-humeralis, as already seen,
and terminates in the mastoido-humeralis. Small branches are supplied
to the posterior cervical lymph glands, the cervical panniculus, the sterno-
mandibularis, sterno-thyrohyoideus, anterior superficial pectoral and a
small branch to the region of the presternum. The dorsal branch extends
antero-dorsally along the anterior border of the anterior deep pectoral
muscle. It passes beneath the prescapular lymph gland and between the
muscles subscapulo-hyoideus and mastoido-humeralis to the latter of which
it is principally distributed. It also gives off branches to the anterior
deep pectoral muscle and to the posterior cervical and prescapular lymph
glands.

The ventral portion of the M. scalenus intervenes between the axillary
blood-vessels and the nerves that form the brachial plexus. The brachial
plexus is formed by the ventral divisions of the 6th, 7th and 8th, cervical
and the 1st and 2d thoracic nerves, as will be demonstrated later. Cut
the dorsal branch of the A. cervicalis inferior and carefully remove the
connective tissue that surrounds the large nerve trunks of the brachial
plexus.

N. phrenicus or diaphragmatic nerve originates from the ventral divisions
of the 6th and 7th cervical nerves; occasionally it receives a small branch
from the 5th cervical also. The two or three radicals of the phrenic
nerve extend obliquely across the superficial face of the M. scalenus and at
its ventral border unite to form a single trunk, just as the nerve enters the
thorax, or a short distance within the thoracic cavity. Dissect up from the
surface of the scalenus the two or three radicals of the N. phrenicus. Im-
mediately after crossing the A. cervicalis inferior the N. phrenicus receives
a small communicating branch from the inferior cervical ganglion of the
sympathetic nerve. The course of the phrenic nerve through the thoracic
cavity to the diaphragm will be studied when the thoracic portion of the
vagus and sympathetic nerves are traced.

Exposure of the brachial plexus and removal of the thoracic limb.

Expose as follows, the ventral divisions of the nerves that form the
brachial plexus, viz., the 6th (not constant), 7th and 8th cervical and the
Ist and 2d thoracic. Cut the N. phrenicus at the first rib. Remove a
section of the ventral portion of the M. scalenus opposite the 6th, 7th, and
8th intervertebral foramina. Cut the skin and the Mm. panniculus
and latissimus, some distance (30 to 50 cm.) posterior to the scapula; cut
the skin and both portions of the trapezius close to the ligamentum nuchae;

7

also cut the serratus magnus, and rhomboideus close to their attach-
ments to the scapula thus leaving the arm attached to the body only by
the nerves of the brachial plexus. Before attempting to expose farther the
ventral divisions of the 6th, if present, 7th and 8th cervical and the
Ist and 2d thoracic nerves, first note on a skeleton the relation of the first
two ribs to the 6th, 7th and 8th cervical and the 1st and 2d thoracic inter-
vertebral foramina, through which the above mentioned nerves emerge from
the spinal cord. Now place the arm in such a position that the whole of
the thoracic portion of the M. serratus magnus is exposed. Carefully
remove the small portion of the M. scalenus that lies dorsal to the brachial
plexus taking care not to cut any of the nerves. The large nerve to the
thoracic portion of the serratus magnus arises from the 7th and 8th cervi-
cals (or from the 8th only) and extends posteriorly on the surface of the
serratus magnus to which it is distributed. This nerve, more or less covered
by connective tissue, may emerge from between the dorsal and ventral
portions of the scalenus, or it may pass through the small dorsal portion of
the muscle. After tracing the nerve, cut it 15 to 20 cm. from its origin.
The ventral divisions of the 7th and 8th cervical nerves are readily exposed;
the 1st and 2d thoracic nerves however, are covered by the ribs of which
the first one must be cut in order to expose the nerves. Remove enough
of the serratus magnus to expose the first rib. Cut the rib a little ventral
to the A. Axillaris, also cut it close to the tuberosity of the rib and remove
the detached portion. The A. cervicalis inferior should now be traced to
its place of origin from the A. Axillaris. With a little care the ventral
divisions of the first two thoracic nerves may be found and cut close to
the intervertebral foramina; the 7th and 8th cervical nerves also should
be cut close to the vertebrae and the arm removed.

Nn. pectorales. Before attempting to demonstrate the nerves to the
pectoral muscles first carefully remove the connective tissue andfat from
the nerves of the brachial plexus using for this purpose the forceps, the back
of the scalpel, or some other non cutting instrument. The origin of the
pectoral nerves vary somewhat in different individuals. The following
disposition however, is common. The most cephalic or anterior of the
pectoral nerves originates from the 7th and 8th cervicals and is distributed
wholly to the anterior deep pectoral muscle (Pl. I, 27). The nerve enters
the muscle a little dorsal to the cephalic vein where it crosses the anterior
deep pectoral. A communicating branch between this nerve and the
phrenic is quite commonly present. The nerves to the superficial pectoral
muscles arise from the loop or arch formed by the N. musculo-cutaneous
(Pl. I, 29) and the N, medianus (Pl. I, 32) immediately beneath the A. axil-

8

laris and from the brachial plexus, in common with the N. medianus (PI. I,
30, 31). Carefully dissect up the overlying posterior portion or sternal
extremity of the anterior deep pectoral and trace the nerves to their respec-
tive places of distribution in the superficial pectoral muscles. The two or
more nerves to the posterior deep pectoral and the panniculus are readily
found. They arise from the brachial plexus apparently in common with
the Nn. medianus and ulnaris. The smaller and more anterior of the
two nerves (in the present specimen) soon divides into three or four
branches which enter the muscle near its humeral end along with the
artery and vein supplied to the muscle. The larger and more posterior
nerve also divides into several branches some of which are distributed to
the posterior deep pectoral and some to the panniculus; note particularly
the large branch which accompanies the large V. thoracica externa which
runs along the dorsal margin of the posterior deep pectoral and is continued
posteriorly in the panniculus.

A. suprascapularis arises from the A. axillaris near the anterior border of
the tendon of the subscapularis, and close to the N. musculo-cutaneous
where it crosses the A. axillaris. About one centimeter from its origin
the A. suprascapularis divides into two branches, of which one is distributed
to the subscapularis, anterior deep pectoral and the supraspinatus; the
other branch is distributed to the anterior deep pectoral, supraspinatus,
the shoulder joint, and the proximal tendon of the biceps. The artery is
accompanied by the V. suprascapularis.

N. suprascapularis (Pl. I, 28; Pl. II, 21) originates from the 7th and 8th
cervical nerves but principally from the 7th; occasionally some fibres
originate from the 6th cervical nerve also. This large nerve passes between
the adjacent borders of the supraspinatus and subscapularis. Carefully
dissect the supraspinatus from the adjoining subscapularis, on one side
of it, and the infraspinatus, on the other, and transect the muscle opposite
the N. suprascapularis. Reflect the muscle sufficiently to expose the
two or three large branches of the nerve to the supraspinatus, which branches
are given off just as the nerve crosses the anterior border of the scapula.
Trace the nerve across the supraspinus fossa and note its width, 1 to 2 cm.
opposite the spine of the scapula. Just as the nerve enters the M. infra-
spinatus it divides into 5 or 6 branches, all of which are distributed to this
muscle.

Nn. subscapulares (Pl. I, 47). There are usually two or more of these
nerves. They pass directly to the M. subscapularis but before reaching

it they divide into numerous branches which diverge somewhat like the
rays of a fan.

9

The nerve to the M. latissimus arises from near the middle of the brachial
plexus, most of its fibres coming from the 8th cervical (Pl. I, 48). It
passes obliquely across the deep face of the Mm. subscapularis and teres
major and is distributed wholly to the latissimus.

Nerves to the M. teres major (Pl. I, 7). There are from 1 to 3 small nerves
supplied to this muscle. They arise from the N. axillaris or rather are
branches of it, and pass directly to the muscle, close to its anterior border.

N. axillaris (Pl. I, 46) arises from the 7th and 8th cervical nerves. It
passes through the triangular space formed by the Mm. subscapularis,
teres major, and the caput longum tricipitis. To demonstrate the distri-
bution of the nerve first remove the skin and the panniculus from the
lateral or external surface of the scapular region. Dissect up the borders
of the M. deltoideus and transect it about 15 to 18 cm. from its attachment
to the deltoid tuberosity. Carefully reflect the humeral portion of the
muscle in order to expose the N. axillaris which enters the deep face of the
muscle directly opposite the above mentioned triangular space (PI. II, 22).
Beneath the muscle, the nerve divides into several branches which are
distributed as follows: several branches enter the deltoideus; one large
branch passes obliquely across the superficial surface of the teres minor
(near its humeral end) to the anterior face of the brachium and enters the
mastoido-humeralis several centimeters below (distal to) the point of the
shoulder (Pl. I, 24); another large branch crosses the superficial surface
of the caput laterale tricipitis or sometimes, is embedded in the substance
of this muscle, and emerges from beneath the posterior border of the M.
deltoideus at the level of the deltoid tuberosity where it becomes subcutane-
ous (PI1.II,23); from here, this subcutaneous branch extends to the antero-
internal aspect of the antebrachium where it breaks up into several cutaneous
branches some of which extend nearly to the carpus. One branch of the
N. axillaris is distributed to the teres minor. This branch may be readily
demonstrated by transecting the muscle, a little proximal to the N. axillaris,
and drawing aside the muscle. One or more branches are supplied to
the teres major, one branch to the subscapularis and a very small filament
to the M. capsularis. The branches to the subscapularis and the capsularis
may arise from the main nerve trunk either separately or by a common
branch.

Clean up the V. axillaris and the several veins from the pectoral, pannicu-
lus, and latissimus muscles also clean up the portion of the V. subscapularis
that lies in the space between the Mm. subscapularis and teres major.
Demonstrate the axillary lymph gland (Pl. I, 49), which lies on the tendon

ice)

of the teres major in the angle formed by the Vv. subscapularis and
brachialis. Now slit the posterior superficial pectoral longitudinally near
its middle. Turn aside the anterior portion of the muscle, together with
the posterior deep pectoral, in order to expose the Mm. coraco-brachialis
and the biceps brachit.

N. musculo-cutaneous (PI. I, 29, 29') is a large nerve and originates from the
7th and 8th cervical nerves. Immediately after crossing the lateral face of
the A. axillaris (Pl. I, 21) a large portion of the nerve joins the N. medianus
by a large short branch that passes beneath the A. axillaris and with the
N. medianus forms a loop around it. Occasionally this nerve loop is
entirely wanting. From the loop thus formed, one or more branches are
given off to the superficial pectoral muscles as already demonstrated. The
larger portion of the N. musculo-cutaneous however, passes through the M.
coraco-brachialis (Pl. I, 13, 29"), the overlying portion of which should be cut
just proximal to the nerve, and drawn aside. As the nerve enters the
coraco-brachialis it supplies a branch to it. Trace the main nerve through
the coraco-brachialis to its termination in the biceps brachii near to the
proximal end of the fleshy portion of the muscle (Pl. I, 29"). Theconnective
tissue and aponeurosis covering the vessels and nerves on the medial face
of the brachial region should now be removed. Note that here the vessels
and nerves have the following relations, viz., the N. medianus lies most
anteriorly and is followed in order by the A. brachialis, V. brachialis, N.
ulnaris, and finally, in the proximal part of the brachium, the large N.
radialis. Note also the small mass of lymph glands lying on the artery
and vein near the distal third of the brachium (PI. I, 49°).

N. radialis (Pl. I, 40) lies posterior to the Nn. medianus and ulnaris and is
the largest nerve of the brachial plexus. It originates from the 7th and 8th
cervical and the Ist thoracic nerves, but principally from the 8th cervical
and ist thoracic. The nerve passes into the triangular space formed by
the tendon of the teres major and latissimus, the caput longum tricipitis
and the proximal end of the brachialis. An artery and vein also enter this
space and should be left intact. As the N. radialis enters the above men-
tioned triangular space it gives off several branches which are distributed
as follows: (a) one branch to the tensor fasciae antebrachii (Pl. I, 44).
To demonstrate this branch, transect the tensor fasciae antebrachii near
its distal third and turn the muscle aside but do not injure the nerve (a
branch of the N. ulnaris) which runs along the anterior border (PI. I, a),
or sometimes crosses obliquely, the superficial surface of the distal
halt of the muscle. Sometimes a small communicating branch passes from

II

the N. ulnaris to this branch of the N. radialis supplied to the tensor fasciae
antebrachii. (b) A large fasciculus composed of several branches, some
of which recurve slightly around the tendon of the teres major and latis-
simus; all the branches of this fasciculus are distributed to the caput
longum tricipitis (Pl. I, 41). (c) Branches to the caput laterale tricipitis,
caput mediale tricipitis, and anconeus. Of these branches the small one
to the caput mediale is readily found and traced to its muscle; the branches
to the caput laterale and anconeus, however, are more or less completely
hidden by the caput longum and caput laterale and often can be satis-
factorily demonstrated only after the caput laterale has been dissected
as follows: Turn aside the skin and the panniculus from the outer surface
of the triceps. The posterior surface of the caput laterale may now be
freely separated from the caput longum, but in dissecting up the anterior
border of the muscle care should be taken not to cut the cutaneous nerve
(a branch of the N. radialis) which emerges from beneath the muscle at,
or close to, its anterior border (6 to 8 cm. distal to the cutaneous branch
of the N. axillaris, or 8 to 10 cm. from the posterior edge of the M. deltoideus,
Pl. II, c). Transect the caput laterale a little distal to its middle and
freely reflect the distal portion of the muscle; the proximal portion of the
muscle can be turned aside only a little distance as the nerve and blood-
vessels to the muscle enter its deep or anterior face. Trace this nerve and
also the cutaneous branch to their origin from the N. radialis. Now trace
the main trunk of the N.radialis inits course along the musculo-spiral groove
to the point where it passes beneath the M. extensor carpi radialis at its
origin, near the proximal end of the external epicondyle of the humerus
(Pl. II, 11,25). Remove the skin of the antebrachium as far as to the carpus.
Trace the cutaneous branches of the N. axillaris and the N. radalis, the
former to the antero-internal side of the antebrachium and the latter to
the antero-external side of the antebrachium. Both of these cutaneous
branches may readily be traced to near the carpus. The M. extensor carpi
radialis should now be dissected as follows: Transect it near the middle
and freely turn aside the distal portion, but in turning aside the proximal
part of the muscle care must be exercised to avoid cutting or breaking
the nerves and blood-vessels that enter the deep face of the muscle (near
the posterior border of the distal end of the M. brachialis). Now trace the
N. radialis beneath the proximal portion of the extensor carpi radialis
taking care not to cut the branches of this nerve, usually three in number,
that enter the deep face of the muscle (Pl. II, d). The main nerve now
passes beneath the extensor digitalis communis, near the origin of the
muscle. Transect the extensor digitalis communis near the middle of the
antebrachium and as the proximal portion is reflected avoid breaking the

I2

blood-vessels and the two or three branches of the N. radialis supplied to
the muscle (Pl. II, e). Beneath this muscle the N. radialis gives off a small
branch to the extensor carpi obliquus (P1.II,f); this branch lies directly upon
the anterior-lateral face of the radius, at the side of the A. radialis anterior,
and beneath the deep face of the extensor digitalis communis which must
be turned aside sufficiently to expose the extensor carpi obliquus. Shortly
before the N. radialis passes beneath the extensor digitalis lateralis, close
to its origin, it gives off a small branch to this muscle (Pl. II, g).
Slit open the aponeurotic sheath of the muscle and trace the branch some
little distance. Now transect the muscle at the level of the N. radialis
and trace the latter into the flexor carpi externus where the nerve terminates
(Pl. II, h). It will be seen from the above that the N. radialis supplies
the following muscles; the triceps (caput longum, laterale and mediale),
the tensor fasciae antebrachii, the anconeus, the extensor carpi radialis,
the extensor digitalis communis, the extensor digitalis lateralis, the extensor
carpi obliquus, and the flexor carpi externus, and one or more cutaneous
branches to the skin of the antebrachium.

Blood-vessels of the Brachial Region

The large V. axillaris and several of the vessels opening into it, viz.,
V. thoracico-dorsalis from the deep pectoral muscles; the V. suprascapu-
laris, the V. thoracico-externa together with the branches from the latissi-
mus and panniculus that communicate with the V. thoracico-externa a
short distance from its termination, have already been exposed. Additional
veins should be noted as they are uncovered in the further dissection.

A. axillaris (Pl. I, 21). Upon emerging from the thorax the A. axillaris
crosses the tendon of origin of the coraco-brachialis and the insertion of
the subscapularis, at the postero-internal side of the scapulo-humeral
joint. From here the artey is continued by the A. brachialis (Pl. I, 23)
which extends obliquely across the middle of the humerus to the antero-
internal side of the distal third of the shaft of the bone where it divides
into two terminal branches—the A. radialis anterior and the A. radialis
posterior.

Branches of the A. axillaris,

A. cervicalis inferior.
A. suprascapularis.
A. subscapularis.
The A. cervicalis inferior and the suprascapularis have already been
traced, pp. 5, 8. The large A. subscapularis (Pl. I, 22) arises from the

13

axillaris at the posterior border of the M. subscapularis. Before exposing
the A. subscapularis first trace the branch, A. thoracico-dorsalis, that arises
from the subscapularis 1 to 2 cm. from its origin (Pl. I, immediately below
22). This artery extends obliquely across the inner face of the teres major
supplies small branches to it and to the axillary lymph gland and terminates
in the latissimus and panniculus. Transect the M. teres major near the
middle and turn it aside. Now trace the A. subscapularis between the
Mm. subscapularis and teres major across the inner surface of the caput
longum tricepitis to the posterior angle of the scapula. The A. subscap-
ularis gives off the following branches:

(1) A. thoracico-dorsalis already dissected. See above.

(2) A. circumflexa humeri posterior arises 1 to 2 cm. peripheral to
the A. thoracico-dorsalis. It accompanies the N. axillaris to the deep face
of the M. deltoideus and is distributed to this muscle and also to the caput
longum, the caput laterale, the brachialis, the teres minor and a small twig
to the capsule of the scapulo-humeral joint.

(3) A. circumflexa scapulae arises from the subscapularis 5 to 8cm.
peripheral to the A. circumflexa humeri posterior and extends directly to
the posterior border of the scapula; here it divides into two branches of
which one passes to the outer and the other to the inner surface of the
scapula. The outer branch crosses, at nearly a right angle, the outer face
of the scapula, a little below the spine, and is distributed to the infra and
supraspinati and the teres minor. The inner branch is distributed to the
subscapularis. The general course of these vessels is indicated by the
vascular grooves of the scapula. (See cleaned scapula.)

(4) Rami musculares. Numerous small branches of the A. sub-
scapularis are supplied to the Mm. subscapularis and teres major. Two
or more large branches of the A. subscapularis are given off to the caput
longum, the tensor fasciae antebrachii, the infraspinatus and the deltoideus.
The V. subscapularis accompanies the artery.

A. circumflexa humeri anterior arises from the brachialis 1 to 4 cm. periph-
eral-to the subscapularis. It passes between the humerus and the M.
coraco-brachialis, supplies a branch to this muscle and terminates in the
biceps brachii and mastoido-humeralis. (The biceps may now be tran-
sected.) It gives off a branch which extends towards the scapulo-humeral
joint and is distributed to the biceps brachii and its synovial tendon sheath.
Occasionally the A. circumflexa humeri anterior is a small vessel supplying
only the coraco-brachialis.

16

external flexors of the carpus and to the artery and vein. Five to eight
centimeters from the carpus the nerve divides into two branches of which
one pierces the aponeurosis and passes, subcutaneously, across the tendon
of the flexor carpi externus and divides into numerous branches which extend
obliquely to the antero-lateral face of the carpus and metacarpus (PI. ITI,
25'; Pl. II, 26). The other terminal branch of the N. ulnaris unites with a
branch of the N. medianus, below the supracarpal arch, and thus forms the
N. volaris lateralis (Pl. III, 26).

A. radialis anterior (Pl. II, 19) is the smaller of the two terminal branches
of the A. brachialis. It passes obliquely downward and outward between
the anterior face of the humerus and the Mm. biceps brachii and the
brachialis. Transect the brachialis where it crosses the external surface of
the tendon of the biceps. Beneath the brachialis and the extensor carpi
radialis, the artery supplies branches to these muscles. Beneath the exten-
sor digitalis communis the A. radialis anterior gives off two or three small
branches to this muscle; it also sends a branch to the extensor digitalis
lateralis and to the flexor carpi externus. The A. radialis anterior is
continued as a small branch which extends along the antero-internal
aspect of the radius to the carpus where it joins the rete carpi dorsalis.

A. radialis posterior (Pl. I, 26) is the direct continuation of the A. brachialis
and is the larger of its two terminal branches. The artery crosses the
antero-internal face of the humero-radial joint and is here covered by
the skin, the aponeurosis and the posterior superficial pectoral muscle.
Note that in this region the N. medianus, as it passes from the posterior
to the anterior side of the artery and vein, lies superficially to the blood-
vessels (Pl. I). A little below the humero-radial joint the A. radialis
posterior, accompanied by the N. medianus, passes under the flexor carpi
internus (Pl. I, 16) which should be transected and turned aside. Beneath
this muscle it extends to the distal third of the shaft of the radius and is then

continued by the large A. digitalis communis and the two metacarpal
arteries.

Branches of the A. radialis posterior.

(1) One or more small branches to the humero-radial joint.

(2) Muscular branches to the flexor carpi internus and medius and
to the flexor perfortus and perforans.

(3) A. interossea communis, is a large branch that arises from the
radialis posterior near the level of the radio-ulnar arch through which the
interossea communis passes. In the interosseous space it gives off the
nutrient artery of the radius. After passing through the interosseus space

17

the artery gives off one or more branches to the flexor carpi externus,
anastemoses with the radialis anterior, and is continued along the antero-
external face of the radius, beneath the common digital extensor, to the
carpus where it anastemoses by a fine branch with the radialis anterior
and also commonly joins the rete carpi dorsalis. Near the proximal third
of the radius it gives off a small branch which runs along the extensor digi-
talis lateralis, supplies twigs to this muscle and to the extensor carpi obliquus.
One or two centimeters distal to the interossea communis the A. radialis
posterior may give off another branch nearly as large as the A. interossea
communis. This second branch (in the present specimen) crosses at a
right angle the posterior face of the radius then turns towards the carpus
and is distributed by numerous branches to the flexor perforans and flexor
pertoratus.

N. medianus (Pl. I, 32) arises from the 8th cervical and 1st thoracic nerves.
Immediately below the A. axillaris the nerve usually receives a large branch
from the N. musculo-cutaneous thus forming with it a loop through which
the artery passes (Pl. I). Near the middle of the brachium the N. medianus
gives off a large branch which extends very obliquely beneath the biceps,
rarely sending a small filament to it, and divides into two branches (PI. I,
34, 35) of which one is distributed to the brachialis; the other branch
winds very obliquely across the lateral face of the biceps, near the distal
end, to the antero-internal face of the antebrachium where it divides into
two principal branches which accompany the two respective subcutaneous
veins, i.e. the cephalic and accessory veins, on the inner surface of the
antebrachium (Pl. I, 34"). The vein should of course, be dissected along with
the nerves. The larger of the two subcutaneous branches of the nerve may
be traced to the middle of the metacarpus. The main trunk of the N.
medianus and the artery and vein radialis posterior, after crossing the
humero-radial joint, pass beneath the flexor carpi internus as already
demonstrated (Pl. I, 16). Note very carefully the relation of the nerve,
artery and vein to each other and to the posterior superficial pectoral
muscle and to the internal tuberosity of the radius. Median neurectomy
is performed in this region and also the pulse may here be readily felt.
A little before the N. medianus passes beneath the flexor carpi internus it
gives off two or three branches which are distributed as follows: One or
two branches, to the flexor carpi internus (Pl. I, 36); a much larger branch
which soon divides into two parts both of which are distributed to the
humeral portion of the flexor perforans (Pl. I, 37); and finally a small nerve
which also divides into two branches (Pl. I, 38) one of which extends into
the radio-ulnar arch and is distributed principally to the periosteum; the

18

other branch extends along the posterior face of the radius to the radial
head of the flexor perforans to which it is distributed. Continue the dis-
section of the N. medianus in its course beneath the flexor carpi internus.
Near the distal third of the antebrachium the nerve (PI. III, 24) divides
into two terminal branches one of which unites with a branch of the N.
ulnaris as already seen, and with it forms the N. volaris lateralis (Pl. III,
26); the other terminal branch of the N. medianus forms the N. volaris
medialis (Pl. III, 27).

N. volaris lateralis, as already stated, is formed by the union of two branches,
one from the N. ulnaris and the other from the N. medianus. The N.
volaris lateralis, accompanied by a small artery (A. metacarpea volaris
lateralis) and vein, crosses the carpus at the medial side of the pisiform
bone, in a special channel in the carpal sheath. At the proximal end of
the metacarpus the nerve gives off a large branch to the suspensory ligament;
before tracing this branch however, follow the N. volaris lateralis as far
as to the fetlock noting the branch of considerable size from the N. volaris
medialis that joins it a little proximal to the distal end of the rudimentary
metacarpal (Pl. III, 28). Transect the two flexor tendons near the middle
of the metacarpus taking care not to injure the N. volaris medialis and the
large artery and vein at the medial side of the tendons (Pl. III). Reflect
the proximal portion of the tendons and carefully trace the branch from
the N. volaris lateralis to the suspensory ligament to which it supplies
more small branches and also two branches that accompany the respective
two or arteries metacarpea volaris medialis and lateralis.

A. retis carpi volaris is a small vessel which arises from the A. radialis
posterior near the distal third of the antebrachium and descends to the
posterior surface of the carpus where it divides into several small branches
which help to form the rete carpi volare.

A. metacarpea volaris lateralis. This is the smallest of the three branches
that continue the A. radialis posterior. It arises from the lateral side of
the A. radialis posterior, crosses the medial face of the pisiform bone, with
the N. volaris lateralis, and continues to the proximal end of the meta-
carpus. Here it is connected with the A. metacarpea volaris medialis
usually by two transverse branches, thus forming the arcus volaris pro-
fundus. The larger of the two transverse branches lies between the sub-
carpal or inferior check ligament of the perforans tendon and the suspensory
ligament: the other transverse branch, not always present, lies between
the suspensory ligament and the large metacarpal bone. Cut the suspen-
sory ligament near the middle and draw it aside. Below the deep vascular

19

arch, the A. metacarpa volaris lateralis runs in a flexuous course on the
posterior face of the large metacarpal bone, close to the lateral rudi-
mentary metacarpal. Near the distal third of the metacarpus the artery
unites with the A. metacarpea volaris medialis to form a short trunk which
joins the A. digitalis lateralis close to the origin of the latter.

A. metacarpea volaris medialis (P1. III, 17) arises from the radialis posterior,
usually a little proximal to the metacarpea volaris lateralis, and is con-
siderably larger than that artery. It passes across the postero-internal
face of the carpus with the large vein of the same name, imbedded in the
carpal sheath or posterior annular ligament. At the proximal end of the
internal rudimentary metacarpal it is connected with the A. metacarpea
volaris lateralis, usually, by two transverse branches (arcus volaris pro-
fundus) as mentioned above. It then continues in a flexuous course, on
the posterior internal face of the large metacarpal, to near the distal third
of the metacarpus where it unites with the metacarpea volaris lateralis
to form a short common trunk which joins the A. digitalis lateralis. The
nutrient artery of the large metacarpal bone is a branch of the metacarpea
volaris medialis.

A. metacarpea dorsalis lateralis and A. metacarpea dorsalis medialis are
two very small arteries that have a variable origin. Sometimes they arise
from the A. metacarpea volaris, of the same side, at the level of the deep
vascular arch. They extend anteriorly across the heads of the rudimentary
metacarpals, descend in the grooves between the large and small metacarpal
bones, and anastamose with the corresponding A. metacarpea volaris.
Sometimes these two small arteries arise from the rete carpi dorsalis and
in other cases, they arise in part from the rete carpi dorsalis and in part
from the A. metacarpea volaris lateralis and the A. metacarpea volaris
medialis.

A. digitalis communis (Pl. III, 18) is the largest and most direct continua-
tion of the A. radialis posterior. It extends through the carpal canal at
the medial side of the flexor tendons, in company with the N. volaris
medialis. Slit open the carpal canal and trace the artery and the large
metacarpal vein that, in the metacarpal region, accompanies the artery
along the medial side of the flexor tendons to near the fetlock where the
artery divides into the A. digitalis lateralis and the A. digitalis medialis.
Remove the hoof or horn capsule.

N. volaris medialis (Pl. III, 27) is formed by one of the terminal branches of
the N. medianus. It passes through the carpal canal in close company with

20

the large A. digitalis communis and both artery and nerve are in close
relation with the flexor tendons. Note that near the middle of the meta-
carpus the nerve gives off a large branch which crosses very obliquely the
posterior face of the flexor tendons and joins the N. volaris lateralis a little
above the distal extremity of the rudimentary metacarpal (Pl. III, 28).
At the level of the sesamoid bones of the fetlock, the nerve divides into
two, sometimes three, branches, viz., an anterior, a middle, if present, and a
posterior branch (PI. III, 30, 31, 32). These branches are of very unequal
size, the posterior being much the largest and the most important. This
branch is the one that is cut in the operation of low neurectomy. The anter-
ior branch descends in front of the vein and is distributed to the skin on the
anterior face of the digit and to the coronary band or matrix. The middle
branch is small and irregular; it descends between the artery and vein and
is generally formed by the union of several small branches which cross over
the artery before uniting. This branch terminates in the coronary band
or matrix and the sensitive laminae. The posterior branch lies close behind
the artery, except at the fetlock, where the nerve is more superficial than the
artery. This posterior branch accompanies the digital artery and will be
traced with it. It is distributed to the sensitive laminae, sole and frog.

A. digitalis lateralis and A. digitalis medialis are formed by the bifur-
cation of the digitalis communis near the distal third of the metacarpus.
Each artery passes over the outer surface of the corresponding sesamoid
bone at the fetlock, and descends parallel to the borders of the deep flexor
tendon to the volar foramina of the third phalanx; in the semilunar canal
of this bone the two arteries anastomose with each other. Expose the
artery of one side, as follows:: remove the lateral cartilage and the anterior
or apical two-thirds of the plantar cushion; remove also, the portion of
the deep flexor tendon that is exposed by the removal of the anterior part
of the plantar cushion, 1.e. the portion of tendon in relation to the navicular
bone and the semilunar crest of the third phalanx. Each digital artery is
accompanied by a vein and the two or three branches of the volar nerves.
Proximal to the fetlock the artery lies deeply. and is covered by the vein
and nerve; at the fetlock the three structures lie at the same level, the vein
being anterior and the large posterior branch of the nerve back of the artery.
The anterior branch of the volar nerve crosses obliquely the digital
artery and vein at, or a little below, the fetlock (Pl. III, 30). The vessels
and nerves are crossed obliquely by a small ligamentous band extending
from the ergot to the fascia at the side of the first interphalangal or pastern
soi CPL. TE, 13).

21

Branches of the A. digitalis lateralis.

(1) Numerous small branches to the ergot, joints, tendons and tendon
sheaths.

(2) A. phalangis primae. (Artery of the first phalanx). This is a
short trunk which arises at a right angle near the middle of the first phalanx
and divides almost immediately into an anterior and a smaller posterior
branch. The anterior branch divides into an ascending and a descending
portion both of which are distributed on the anterior face of the first phalanx.
A branch passes between the extensor tendon, which should be cut, and the
first phalanx and anastamoses with the corresponding artery of the oppo-
site side. The small posterior branch of the A. phalangis primae divides
into several branches of which one passes between the infrasesamoidean
ligaments and the first phalanx and anastomoses with the opposite artery;
the other branches are distributed to the structures on the posterior face
of the first. phalanx.

(3) <A. toricae phalangis tertia (artery of the plantar cushion) arises
at a right angle from the digitalis, at the proximal border of the lateral
cartilage. It extends postero-distally and is distributed to the plantar
cushion and to the matrix of the frog.

(4) A. dorsalis phalangis secundae (dorsal or anterior artery of the
second phalanx). This artery arises at a right angle from the digitalis,
near the middle of the second phalanx, and under cover of the lateral
cartilage. It extends anteriorily beneath the lateral cartilage and the
extensor tendon and anastomes with its fellow of the opposite side. Just
as it passes beneath the extensor tendon it gives off a branch to the coronary
band or matrix; it also supplies small branches to the tendon and to the
joint capsule. A branch of the volar nerve accompanies the artery.

(5) A. volaris phalangis secundae (ventral or posterior artery of the
second phalanx) is smaller than the preceding opposite to which it arises.
It passes above the proximal border of the navicular bone and anastomoses
with its fellow of the opposite side.

(6) A. dorsalis phalangis tertiae (dorsal artery of the third phalanx) arises
from the digitalis at the inner or medial side of the wing of the third phalanx.
In company with the posterior branch of the N. volaris, it passes through
the notch (or foramen) of the wing of this bone and extends anteriorly in
the vascular groove on the lateral surface of the bone. It gives off a pos-
terior branch to the plantar cushion.

The branches of the A. digitalis medialis are the same as those of the

A. digitalis laterales.

PLATE I
MEDIAL OR INNER VIEW OF THE PECTORAL LIMB

Posterior superficial pectoral.

Anterior superficial pectoral.

Posterior deep pectoral.

Anterior deep pectoral.

M. supraspinatus.

M. subscapularis.

M. teres major.

M. latissimus dorsi.

M. panniculus.

Aponeurotic tendon of panniculus.

10, 10’.. Tensor fasciae antebrachii.

11. M. caput longum tricipitis.

12. M. caput mediale tricipitis.

13. M. coraco-brachialis.

14. M. biceps brachii.

15. ‘Aponeurotic tendon-slip from biceps brachii.

16. M. flexor carpi internus.

17. M. flexor carpi medius.

. Ulnar head of flexor carpi medius.

18. Ulnar head of flexor perforans.

19. M. flexor perforatus.

20. M. flexor perforans.

21. A. axillaris.

22. A. subscapularis.

23. A. brachialis.

24. A. profunda brachii.

25, 25’. A. ulnaris.

26. A. radialis posterior.

VII, VIII, I, I], = 7th - 8th cervical and 1st and 2d thoracic nerves.

27. Nerve to anterior deep pectoral.

28. N. suprascapularis.

29, 29’. N. musculo-cutaneous.

30, 30’.. Nn. to anterior and posterior superficial pectorals.

31. Nn. to posterior deep pectoral.

32, 32’. N. medianus.

33. Nerve filament to biceps brachii (very rarely present).

34, 34’.. Cutaneous branch of N. medianus.

35. Branch of N. medianus to M. humeralis obliquus.

36. Branch to M. flexor carpi internus.

37. Branch to flexor perforans.

38. Small branch to radial head of flexor perforans and to the radio-ulnar arch.

39, 39’. N. ulnaris (a) cutaneous branch; (b) branch to M. flexor carpi medius; (c) branch to flexor
perforatus; (d) branch to ulnar head of flexor perforans; (e) branch to ulnar head of flexor per-
foratus.

40. M. radialis.

41. Branch to caput longum tricipitis.

42. Branch to caput longum, laterale, mediale and anconeus.

43. Portion of N. radialis that continues along the spiral groove to the extensors of the metacarpus and
phlanges.

44. Branch of N. radialis to the M. tensor fasciae antebrachii.

45. Nerve to the panniculus and posterior deep pectoral.

46. N. axillaris.

47. Nn. subscapulares.

48. Nerve to the M. latissimus dorsi.

49. Axillary lymph gland.

Lymph gland.

ro]

OO WN ANE WN

PLATE II
LATERAL OR EXTERNAL VIEW OF THE PECTORAL LIMB

M. supraspinatus.
3, 3’. M. deltoideus (transected and turned aside).
M. teres minor.
M. caput longum tricipitis.
. M. tensor fasciae antebrachii.
6’. M. caput laterale tricipitis (transected and the distal portion turned back).
M. anconeus.
M. biceps brachii. ;
M. mastoido-humeralis.
1o. M. brachialias.
11, 11’. M. extensor carpi radialis (transected and the distal portion turned aside).

12. Radius.
13, 13’. M. extensor digitalis communis (extensor pedis) a portion of the muscle has been removed.
14. M. extensor carpi obliquus.
15. Ulnar head of M. flexor perforans.
16. M. flexor carpi externus.
17. M. extensor digitalis lateralis.
18. M. flexor perforans.
19, 20. A. radialis anterior.
21. N. suprascapularis.
22. N. axillaris.
23. Cutaneous branch of N. axillaris.
24. Branch of N. axillaris to M. mastoido-humeralis.
25, 25’. N. radialis.
. a’. Branch of N. radialis to caput laterale tricipitis.
. Branch to M. anconeus.
Cutaneous branch of N. radialis.
Branches of N. radialis to M. extensor carpi radialis.
Branches to M. extensor digitalis communis.
Branch to M. extensor carpi obliquus.
. Branch to M. extensor digitalis lateralis. j
. Termination of N. radialis in the M. flexor carpi externus.+*' > '

26. Cutaneous branches of N. ulnaris.

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20.
21, 2

29.
30, 3
33-

PLATE IIT
MEDIAL OR INNER VIEW

Radius.

". Principal and medial metacarpal bones.
Lateral cartilage.

M. extensor carpi radialis.

M. extensor carpi obliquus.

M. flexor carpi internus.

M. flexor perforatus.

M. flexor carpi medius (turned aside).

M. interosseus medius.

M. lumbricalis medius.

Portion of carpal sheath or annular ligament.
Suspensory or suprasesamoid ligament.
Ligament of ergot.

Cut edge of antebrachial aponeurosis (not clearly shown in figure).
A. radialis posterior.

Supracarpal arch.

A. metacarpea volaris medialis.

A. digitalis communis.

A. digitalis medialis.

A. ulnaris.

2. V. radialis posterior.

V. ulnaris.

N. medianus.

. Branch of N. medianus to the N. ulnaris.

N. ulnaris.

. Cutaneous branch of N. ulnaris.

N. volaris lateralis.

N. volaris medialis.

Anastomosing branch from N. volaris medialis to the N. volaris lateralis.
Small branch to region of ergot.

1, 32. Anterior, middle and posterior branches of the N. volaris medialis.
Coronary band of matrix.

Dissection of the Blood-Vessels and Nerves of
the Leg or Pelvic Limb

Remove the intestines and transect the body immediately caudal to
the last pair of ribs. In the male, find the spermatic veins and the much
smaller spermatic arteries near the peritoneal or vaginal ring through
which they, together with the ductus deferens or spermatic duct, pass to
the testes. Trace the right spermatic vein to the posterior vena cava,
and the left one to the left renal vein (or to the posterior vena cava, close
to the renal vein); also trace the spermatic arteries to their respective
places of origin—the right spermatic artery, from the A. mesenterica
posterior and the left one from the aorta a little cephalad of the preced-
ing; sometimes both of these arteries arise from the aorta close to the A.
mesenterica posterior. Inthe female the utero-ovarian arteries correspond
to the spermatic arteries but are much shorter. Each artery passes in a
tortuous manner between the two peritoneal layers of the anterior part
of the broad ligament of the uterus and divides into two branches of
which one is distributed to the ovary and the other to the cornu of the
uterus. Clean up the aorta (and vena cava) taking care not to remove the
lumbar lymph glands which lie near the place where the aorta divides into
the Aa. iliaca externa and interna, (sometimes spoken of as the terminal
branches of the aorta) (Pl. V, 30, 34). Note the size, number and location
of the lumbar lymph glands. The posterior portion of the body should
now be divided into halves by a sagittal section through the lumbar and
sacral vertebrae, the pelvic symphysis and the pelvic organs. Identify
each lumbar and sacra vertebra. Identify also the trunk of the sympa-
thetic nerve which, in this region, lies on the ventro-lateral face of the
bodies of the vertebrae and is covered by the aorta and the posterior vena
cava (Pl. V, 45). This nerve trunk and its connections with each of the
lumbar and sacral nerves, by the rami communicantes, should be noted
as the dissection of the lumbo-sacral nerve plexus proceeds.

A. circumflexa iliaca (Pl. V, 29) usually arises from the A. iliaca externa,
close to its origin, but sometimes directly from the aorta. It extends
laterally across the ventral surface of the psoas muscles and divides into
an anterior and a posterior branch shortly before it reaches the pos-
terior border of the M. transversus abdominis. Transect the transversus
abdominis near the middle of its fleshy portion and turn it aside. Note
the location and size of the external iliac lymph glands (Pl. V, 64) which

28

are situated near the bifurcation of the A. circumflexa iliaca. Dissect up
the peritoneum cephalad of the peritoneal or vaginal ring and note very
carefully the relation of this ring and the spermatic cord, to the posterior
edge of the M. obliquus internus. Do not confuse the M. cremasteric
externa with the obliquus internus. Transect the obliquus internus a little
dorsal to the peritoneal ring. Now trace the anterior branch of the A.
circumflexa iliaca. At, or near, its origin it may give off one or two small
branches to the psoas magnus and iliacus. About 5 cm. from its origin
this anterior branch divides into two branches which are distributed to
the Mm. transversus, abdominis obliquus internus and obliquus externus.
The posterior branch of the A. circumflexa iliaca, 5 to 8 cm. from its origin,
also divides into two branches of which one goes to the obliquus internus
and the other, after perforating the abdominal wall near the external angle
of the ilium, runs downward on the inner face of the M. tensor fasciae latae,
about 5 cm. from its anterior border, and is distributed to the panniculus,
the precrural or subiliac lymph gland and to the inner face of the tensor
fasciae latae. To demonstrate this latter branch reflect the skin in the
region of the flank and dissect between the abdominal wall and the inner
face of the tensor fasciae latae. Find the artery (and vein) on the inner
surface of the tensor fasciae latae, 5 to 8 cm. from its anterior border, and
trace it in both directions.

Internal inguinal ring.

The internal inguinal ring should not be confused with the small peri-
toneal or vaginal ring of the male. The internal inguinal ring is from 10
to 12cm. inlength, measured from the prepubic tendon to the dorsal margin
of the peritoneal ring. The anterior boundary of the internal inguinal
ring is formed by the posterior edge of the M. obliquusinternus; the pos-
terior boundary is formed by the inguinal ligament. In the male the follow-
ing structures pass through the inguinal canal, viz., the evaginated peritoneum
of the spermatic cord, the ductus deferens or spermatic duct, the spermatic
nerves, artery and vein and lymph vessels, the A. pudenda externa and
the M. cremasteric externa. The skin in the region of the external inguinal
ring should now be carefully turned aside in order to expose the superficial
inguinal lymph gland, the external inguinal ring and the structures which
pass through it. The superficial inguinal lymph gland forms a large mass,
8 to 10 cm. long, which lies anterior to the external inguinal ring. Inthe male
the gland extends along the course of the A. abdominalis subcutanea on
either side of the penis; in the female the gland is situated between the
mammary gland and the abdominal wall. Now turn aside the portion of
the M. obliquus internus that forms the anterior boundary of the internal

29

inguinal ring and note that the space (i.e. the inguinal canal) occupied by
the spermatic cord is bounded posteriorly by the inguinal ligament and
anteriorly, by the M. obliquus internus; note also that the length of the
canal from the external inguinal ring to the level of the peritoneal ring,
measured along the spermatic cord, is about 10 cm.

A. iliaca externa (Pl. V, 30) arises from the aorta at the level of the 5th
lumbar vertebra and extends obliquely ventrally, at the side of the pelvic
inlet, to the level of the anterior edge of the pubis where it is continued
as the A. femoralis. Remove the overlying peritoneum and fascia. Note
that the large V. iliaca externa is immediately posterior to the artery. The
termination of the A. iliaca externa and the beginning of the A. femoralis
is indicated by the truncus pudendo-epigastricus or prepubic artery.

Truncus pudendo-epigastricus or prepubic artery (PI. V, 31) is only6 to 8 cm.
in length. It arises from the A. iliaca externa near the level of the anterior
border of the pubis. The artery crosses the dorsal or free edge of the
inguinal ligament and extends for a short distance along the abdominal or
anterior face of the ligament to the internal inguinal ring where it divides
into two branches—A. epigastrica caudalis or posterior abdominal and A.
pudenda externa or external pudic. °

(1) A. epigastrica caudalis (or posterior abdominal).

This branch of the pudendo-epigastric trunk extends cephalad along
the lateral border of the M. rectus abdominis to which it is principally dis-
tributed; small twigs however, are also supplied to the transversus ab-
dominis and the obliquus internus. The artery is accompanied by a vein.

(2) A. pudenda externa (or external pudic).

This artery and its branches may be readily exposed by dissecting,
en masse, the sheath and penis from the abdominal wall as far back as to
the external inguinal ring taking care not to cut the artery as it emerges
from the ring at the postero-internal commissure.

The A. pudenda externa is from 4 to 6 cm. inlength. Immediately after
it passes through the external inguinal ring it divides into two branches--
the A. abdominalis subcutanea and the A. dorsalis penis. Trace the former
cephalad, along the side of the sheath, to which and to the superficial inguinal
lymph gland it is distributed. The dorsal artery of the penis passes to the
dorsum of that organ and terminates at the glans penis. It gives off col-
lateral branches to the corpus cavernosum one of which usually passes
posteriorly and anastomoses with a branch of the A. obturatoria. In the

‘female the mammary artery takes the place of the dorsal artery of the penis.
Note that the enormous venous plexus on the dorsal and lateral sides of the

30

penis, (or the mammary glands) is drained mainly by the large V. pudenda
externa (Pl. V, 42), which lies in the subpubic groove of the pelvis.

A. pudenda interna (Pl. V, 37).

Care must be exercised in tracing this artery especially its distal half, not
to injure its numerous small branches or the neighboring nerves; the adjoin-
ing veins however, may be cut if desired. The urocyst and all of the other
pelvic organs should be turned dorsally. The A. pudenda interna arises
from the A. iliaca interna near the origin of the latter vessel. It extends
posteriorly across the lateral wall of the pelvic cavity, lying close to the
dorsal border of the iliac portion of the M. obturator internus. Opposite
the superior ischiatic spine the artery is covered by the M. retractor ani
which should be transected and turned aside (Pl. V, 21 and 21"). Near the
lesser sacro-sciatic foramen the artery either passes through the sacro-
sciatic ligament i.e. from its inner to its outer surface, or is imbedded in the
substance of the ligament. Trace the artery peripherally as far as can
be done readily (to the posterior border of M. retractor ani) and then
proceed as follows: make a circular cut in the skin of the anal region at a
little distance, 4 to 6 cm., from the anal orific; also cut the large bundle of
muscle fibres (recto coccygeal, Pl. V 23) that attaches the terminal part of
the rectum to the coccygeal vertebrae. Cut also, the M. retractor penis
(Pl. V, 22). Now carefully remove the connective tissue from the side of
the anus until the artery and nerves are exposed. The main trunk of the
artery terminates in the erctile tissue at the root of the penis.

Branches of the A. pudenda interna.

(1) A. umbilicalis (Pl. V, 39) arises from the pudenda interna 2 to 3 cm.
from the origin of that vessel and passes directly to the urocyst. Before
birth the A. umbilicalis is a very large vessel and carries the foetal blood
to the placenta. After birth the vessel extends only to the urocyst and is
very much smaller than in foetal life.

(2) A. haemorrhoidalis media (or vesico-prostatic). This small artery
in the male, arises from the pudenda interna about 8 cm. from the origin
of the latter (or about half way between the origin of the A. pudenda
interna and the anterior edge of the M. retractor ani) and runs posteriorly.
It supplies small twigs to the rectum, urocyst, prostate gland, and seminal
vesicle. Near the ischial arch the A. pudenda interna gives off a small
branch—A. perinei—which passes somewhat dorsally at the side of the
anus which it supplies; the A. pudenda interna also gives off twigs to the M.
bulbo-cavernosus and the skin of the perineum. In the female the corres-
ponding artery is much larger and gives off the A. uterina caudalis. This

31

runs cephalad on the side of the vagina to which it gives branches and

ramifies on the body of the uterus, anastomosing with the anterior and
middle uterine arteries.

N. femoralis (Pl. V, 46, Pl. VII, 14) originates from the ventral divisions of
the 3d, 4th, 5th and 6th lumbar nerves; very commonly however, the branch
from the 6th lumbar nerve is wanting. Turn aside or remove the iliac
fascia from the ventral surface of the sublumbar muscles. The proximal
portion of the N. femoralis is covered by the M. psoas parvus. Transect
this muscle a little caudal to the A. circumflexa iliaca and turn its distal
portion toward the median plane. The large N. femoralis will now be
seen to have the same general direction ventro-caudally, as the A. iliaca
externa. Transect the psoas magnus at the same level as the psoas parvus;
separate the two muscles from each other sufficiently to trace the N. femoral-
is to its respective places of origin from the 3d, 4th, 5th, and 6th, if present,
lumbar nerves (Pl. V, m1, Iv, v). Near its origin the N. femoralis lies at
about the same level as the A. iliaca externa. At the ventral border of the
tendon of the psoas parvus where the nerve passes under the anterior end of
the M. sartorius (Pl. V, 11), the nerve lies just anterior to the artery but is
separated from it by the tendon of the psoas parvus which lies between the
artery and the nerve (PI. V, 8°).

Branches of the N. femoralis.

The first branch of the N.-femoralis is given off a little peripheral to
the place of junction of the ventral divisions of the 3d, and 4th lumbar
nerves. It is a small branch supplied to the psoas magnus. The next
branch, much larger than the preceding, leaves the N. femoralis a little
peripheral to the junction of the 4th and 5th lumbar nerves. This second
branch extends laterally between the psoas magnus and the iliacus and
divides into several branches which are distributed to the M. iliacus; one
or more small filaments may go to the psoas magnus. The remaining
portion of the N. femoralis may be exposed as follows: Cut the femoral
aponeurosis near its attachment to the M. obliquus externus and remove it.
With the fingers, principally, dissect between the muscles of the thigh and the
posterior face of the inguinal ligament, leaving the ligament intact. Identify
the M. sartorius and note its relation, together with that of the iliacus and
the psoas magnus, to the inguinal ligament. Free the sartorius from its
attachment to the iliac fascia. Dissect between the sartorius and the
M. gracilis taking care not to injure the nerve and blood-vessels that
emerge from between these two muscles near the middle of the thigh.
Transect the sartorius near the middle of the thigh. Draw aside the

Ke

proximal portion of the muscle taking care not to cut the small nerve
branches it receives from the N. saphenus internus (Pl. V, 47, 48) (a branch
of the N. femoralis) which lies immediately beneath the proximal half of
the sartorius; also do not disturb the deep inguinal lymph gland which
lies in the interstice between the sartorius and the pectineus (Pl. V, 63).
As the N. femoralis crosses the tendon of the psoas magnus it gives off the
large branch just mentioned, N. saphenus internus, which runs beneath
the sartorius for about one-half the length of the muscle, supplies small
branches to it, as just stated. It then emerges with the A. and V. saphena
interna, from between the adjacent borders of the sartorius and gracilis,
near the middle of the thigh, where it breaks up into several large sub-
cutaneous branches which are distributed to the inner and anterior faces
of the thigh and leg. The longest of these branches accompanies the
A. and V. saphena interna to the flexor side of the tarsus. Frequently the
N. saphenus internus is divided into two parallel branches. After giving
off the N. saphenus internus the main trunk of the N. femoralis, together
with a large artery and vein, passes between the rectus femoris and the
vastus internus into the quadriceps femoris group of muscles. Dissect
between the vastus internus and the rectus femoris; transect the rectus
femoris Io to 15 cm. from its attachment to the patella and reflect the
ends. The vastus internus also may be partially transected, if desired.
Now trace the N. femoralis to its termination in the rectus femoris, vastus
internus, vastus externus, and vastus intermedius. The small M. capsu-
laris is not supplied by this nerve but by one of the gluteal nerves as
mentioned later.

Exposure of the A. iliaca interna, the A. sacralis lateralis and the sacral
nerves (Pl. V, 34, 35, 52, 54, 55, 56, 57, 60).

Turn the rectum and other pelvic organs ventrally and find the small
nerves (Pl. V, 58) 2 to 4 in number, which lie between the peritoneum and
the sacro-sciatic ligament and extend from the 2d, 3d, and 4th or from the
3d and 4th only, sacral nerves towards the lateral side of the pelvic organs
where, in connection with branches of the sympathetic nerve, they form
an intricate network of nerves known as the hypogastric or pelvic plexus
(Pl. V, 51). (If put on the stretch these two or more small nerves will
stand out as more or less tense bands.) Great care must be exercised in
exposing the A. (and V.) sacralis lateralis and the sacral nerves, because
of their intimate relation to each other and to the sacro-sciatic ligament.
Cut the ligament along the ventral mid surface of the V. sacralis lateralis
and carefully turn it from the vein. It will now be seen that the largest
of the sacral nerves, N. ischiadicus, 5 to 8 cm. in width (Pl. V, 54), originates
from the 5th and 6th lumbar and the Ist and 2d sacral nerves. This large

33

nerve trunk lies on the outer or lateral surface of the sacro-sciatic ligament
and is not very liable to be mutilated. Two smaller nerves however, the N.
pudendus (Pl. V, 57) and the N. haemorrhoidalis (Pl. V, 60) which originate
from the 2d, 3d, and 4th or from the 3d and 4th, only, sacral nerves lie on
the inner or pelvic surface of the sacro-sciatic ligament or else are imbedded
in its substance. Each of these two nerves is from one-half to one centi-
meter in width but is so thin, and in color so closely resembles the liga-
ment that it is liable to be overlooked and removed along with the
ligament.

A. iliaca interna (Pl. V, 34) is a very large vessel and arises from the aorta
close to the intervertebral disc between the 5th and 6th lumbar vertebrae.
It runs under the wing or transverse process of the sacrum, then turns
ventrally and extends along the pelvic surface of the shaft of the ilium to
near the psoas tubercle of the ilium, where the vessel divides into its two
terminal branches—the A. circumflexa femoris lateralis (iliaco-femora!
artery) and the A. obturatoria. To demonstrate this, remove a portion
of the overlying V. iliaca interna.

Branches of the A. iliaca interna.

(1) The last one of the six lumbar arteries arises from the dorsal side
of the A. iliaca interna and passes into the spinal canal through the inter-
vertebral foramen between the last lumbar vertebra and the sacrum.

(2) A. pudenda interna (Pl. V, 37), already described. See p. 30.

(3) A. sacralis lateralis (Pl. V, 35). Remove the overlying V. sacralis
lateralis. The A. sacralis lateralis arises from the iliaca interna close to
the lumbo-sacral articulation. It extends along the sacrum ventral to the
sacral foramina and the nerves that emerge from them. At the third
sacral vertebra the artery divides into two branches—A. coccygeus lateralis
and the much larger A. glutea posterior. Trace the A. coccygeus lateralis
some distance along the tail to which it is distributed. The dissection
of the A. glutea posterior must be deferred until the gluteal nerves are
dissected. See p. 38.

(4) A. iliolumbalis arises at a right angle from the lateral side of the
iliaca interna, crosses the ventral surface of the ilium beneath or dorsal to
the Mm. psoas magnus and iliacus to which it gives small branches. Tran-
sect the M. iliacus opposite the artery. Draw aside the iliacus and the
psoas magnus and trace the artery to where it crosses the external border
of the ilium a little behind the externalangle. Its terminal branches which
will be demonstrated later, enter the gluteus medius and the tensor fasciae

latae.

34

(5) A. glutea anterior is the largest branch of the iliaca interna. It
arises nearly opposite the iliolumbalis, passes through the greater sacro-
sciatic foramen and immediately enters the gluteal muscles by several
branches. These branches cannot be demonstrated until the gluteal
muscles have been dissected. Frequently one of the radicals of the N.
obturatoria (from the 6th lumbar, Pl. VII, 16) crosses the ventral face of
the A. glutea anterior, close to its origin from the iliaca interna.

(6) A. circumflexa femoris lateralis (iliaco-femoral artery) is one
of the terminal branches of the iliaca interna. To expose the vessel, draw
aside the distal portion of the psoas magnus; transect the iliacus and draw it
aside. The artery crosses the shaft of the ilium a little dorsal to the in-
sertion of the psoas parvus and enters the quadriceps femoris group of
muscles between the rectus femoris and the vastus externus. It supplies
branches to the psoas magnus and iliacus, rectus femoris, tensor fasciae
latae, vastus externus and medius and the superficial and middle gluteal
muscles. The artery is accompanied by two large veins.

(7) A. obturatoria (Pl. V, 38) is the inner terminal branch of the A.
iliaca interna. It passes posteriorly on the inner or pelvic surface of the
shaft of the ilium along the ventral border of the iliac portion of the M.
obturator internus. The obturator vein and nerve accompany the artery.
At the anterior border of the obturator foramen the artery, vein and nerve
dip beneath the M. obturator internus (Pl. V, 18'). Cut the overlying
portion of this muscle close to its origin and turn it aside. In its course
beneath the M. obturator internus the artery gives off small twigs to it;
also a larger branch which passes through the obturator foramen and is
supplied to the hip joint. At the very posterior part of the obturator
foramen the obturator artery gives off a small branch which passes posteri-
orly on the dorsal surface of the ischium, to the ischial arch, where it anasto-
moses with a branch of the A. obturatorius that extends along the ventral
face of the ischium; it also anastomoses by a small branch with the A.
pudenda interna. The extrapelvic portion of the A. obturatoria is deeply
covered by the muscles of the inner side of the thigh and can be only par-
tially exposed at present. First dissect the M. gracilis, beginning at its
posterior border; free it from the underlying muscles and at the same time
transect it a little below its middle. Turn back the proximal portion
of the muscle noting the blood-vessels and nerves that enter it. Now
beginning at its posterior border, cut the muscle about two-thirds of the
way across, close to its attachment to the pelvis, in order to expose clearly
the origin of the adductor magnus. (The adductor magnus as here used
includes the adductor parvus of some writers). Note the deep inguinal
lymph gland 12 to 15 cm. in length, that lies in the space between the

35

sartorius and the pectineas (Pl. V, 63). Note the relation of this gland
to the large artery (A. femoralis) beneath it and to the inguinal ligament.
Dissect between the pectineus and the adductor magnus, on one side, and
the deep inguinal lymph gland and the A. and V. femoralis, on the other.
Transect the pectineus a little below its middle and draw aside the distal
portion. Carefully remove any connective tissue or fat from the space
between the pectineus and the adductor magnus and find the small nerves
that enter each of these muscles. Dissect between the adductor magnus
and the semimembranosus; transect the adductor magnus close to its
pelvic attachment and draw up the muscle sufficiently to expose the M.
obturator externus which is directly beneath the proximal portion of the
adductor magnus. Find the A. obturatoria (and large vein) where it emerges
from beneath the posterior border of the M. obturator externus, close to
the ventral surface of the ischium. The posterior portion of the M.
obturator externus must now be cut close to its origin and drawn.aside in
order to expose the A. obturatoria, after it passes through the obturator
foramen. About 5 cm. from the posterior edge of the foramen the artery
gives off a large branch which runs along the ventral surface of the ischium
to the ischial arch where it divides into several branches, of which one goes
to the crus penis close to its attachment to the ischium. The extrapelvic
portion of the A. obturatoria also gives off a branch to the ventral surface
and one to the dorsal surface of the penis. About 5 cm. peripheral to these
two branches a much larger branch is given off to the semimembranosus.
Further dissection of the obturator artery must be deferred until the over-
lying muscles have been dissected.

N. obturatorius (P1.V, 49; P1,VII, 16) originates from the 4th and 5th lumbar
nerves; frequently however, it receives a branch from the 6th lumbar
nerve. The nerve extends directly to the anterior part of the obturator
foramen. It lies just beneath the peritoneum and for some distance accom-
panies the obturator artery and vein; the nerve and blood-vessels then
diverge from each other, the nerve passing through the anterior part of
the obturator foramen and the blood-vessels through the posterior part.
Reflect the proximal portion of the M. gracilis and the large branch of the
N. obturatoris that supplies it will be seen on the proximal portion of the
muscle extending transversely toward its posterior border. Upon drawing
aside the proximal portion of the M. pectineus the branches of the N.
obturatorius to it and to the adductor magnus may be seen. Upon
drawing the adductor magnus from the obturator externus the branch
of the obturator nerve that passes through the M. obturator externus,
near its anterior border, and enters the adductor magnus, may be seen.

36

Turn aside or remove a portion of the obturator externus and trace the
respective branches supplied to it and to the adductor magnus, the gracilis,
and pectineus to their respective places of origin from the obturator nerve.
It will now be seen that N. obturatorius divides into two branches one of
which is distributed to the gracilis and pectineus and the other to the
adductor magnus and obturator externus.

N. pudendus (PI. V, 57, 57‘) originates from the 2d and 3d sacral nerves, or in
some cases from the 3d only. It extends posteriorly, at first on the inner or
pelvic surface of the sacro-sciatic ligament, but gradually passes into the
substance of the ligament. Near the lesser sciatic foramen the nerve
crosses the lateral surface of the A. pudenda interna, (Pl. V, 37), and
inclining inwards, turns around the ischial arch and gains the dorsal surface
of the penis along which it continues as the N. dorsalis penis. Shortly
before the nerve crosses the A. pudenda interna it gives off the N. haemor-
rhoidalis medius, or perinaeo-anal nerve (Pl. V. 57'') which is distributed
by numerous branches to the muscles of the urethra and penis, including
the ischio—-cavernosus muscle, and to the terminal portion of the rectum.
The communicating branch of the posterior ventral gluteal nerve (Pl. V, 55)
to the N. pudendus joins the latter at the place of origin of the perinaeo-anal
nerve. In the female the N. pudendus is distributed to the labia, clitoris,
and the constrictor muscles of the vulva and anus and to the perineum.

N. hemorrhoidalis (Pl. V, 60) is formed from the 3d and 4th sacral nerves
or from the 4th only. It passes posteriorly on the inner or pelvic face
of the sacro-sciatic ligament to the anal region where it divides into a
number of branches which are distributed to the retractor and sphinctor
muscles of the anus and to the skin of the perineal region.

A. profunda femoris arises either in common with the truncus pudendo-
epigastricus (or prepubic) or a little peripheral to it. It passes caudo-
ventrally between the pectineus and the terminal tendon of the iliacus
and psoas magnus. Draw aside the pectineus and demonstrate the one
or more small branches supplied to it. Beneath the adductor magnus the
artery gives off a very large branch which is distributed to this muscle, and
to the gracilis and the semimembranosus. It also supplies twigs to
the deep inguinal lymph gland. The remaining portion of the A. profunda
femoris is covered by muscles and cannot be traced at present. A large
vein accompanies the artery.

A. femoris anterior (P1.V, 32) arises from the A. femoralis about 2 cm. peripheral
to the femoris profunda, from the opposite side of the A. femoralis. It passes

OF

anteriorly and enters the precural group of muscles between the rectus
femoris and vastus internus. It supplies branches to the iliacus and the
quadriceps femoris muscles.

Exposure of the gluteal vessels and nerves.

Remove the skin from the gluteal and femoral regions. Dissect be-
tween the biceps femoris and the adjoining muscles, viz., the gluteus superfi-
cialis and vastus externus, anteriorly, and the semitendinosus, posteriorly.
Also dissect between the semitendinosus and the semimembranosus. Tran-
sect the semitendinosus opposite the ischial tuberosity and draw aside the
proximal portion just enough to expose the nerve and blood-vessels that
enter it immediately dorsal to the ischial tuberosity (Pl. IV, 25). Transect
the biceps femoris at the level of the external small trochenter and also at the
level of the nerve, just exposed, to the semitendinosus, i.e. immediately
dorsal to the ischial tuberosity. In this latter transection one of the large
nerve branches to the biceps femoris will probably be cut; the other large
nerve branch to this muscle lies more deeply and may be seen readily if the
proximal portion of the muscle be drawn aside. Trace both of these
large branches peripherally for some distance. Upon drawing aside the
proximal portion of the biceps femoris it will be seen that the two or three
large branches just mentioned (and the A. and V. glutea posterior) emerge
from beneath the gluteus medius and are distributed to the biceps femoris
and also one small branch to the posterior border of the gluteus super-
ficial is (Pl. IV, 23). These large nerve branches cannot be traced at present
to their place of origin from one of the posterior gluteal nerves. Now
dissect between the tensor fasciae latae and the gluteus superficialis taking
care not to cut the nerve or blood-vessels that emerge from beneath the
anterior edge of the gluteus superficialis near its middle, and enter the
adjoining borders of the tensor fasciae latae and the gluteus superficialis
(Pl. IV, 22). Transect the gluteus superficialis a little proximal to the
nerve just exposed, turn it aside somewhat, and note the small nerves and
blood-vessels supplied to its anterior edge. The gluteus medius should
now be transected a little proximal to the two above mentioned nerves
that emerge from beneath the respective anterior and posterior borders
of the muscle, i.e. the nerve to the tensor fasciae latae and the nerve to
the biceps femoris (Pl. IV, 22, 23). The deep face of the gluteus medius is
indicated by these two nerves and they should be kept in view while transect-
ing the muscle; this may be done if while transecting it, the proximal portion
of the muscle be freed largely from its attachment to the iliac fossa and the
sacrum and turned back. Note the vein and artery—A. iliolumbalis—
that cross the external border of the ilium from 5 to 8 cm. ventral to the

38

external angle of the ilium and are distributed to the gluteus medius and
tensor fasciae latae. See p. 33.

A. glutea anterior. The distribution of the A. glutea anterior to the mid-
dle and deep gluteals may now be demonstrated. The artery will have
been cut when the gluteus medius was turned back. Clean up the artery
in so far as it can be traced. See p. 34.

A. glutea posterior or ischiadicus (continued, see p. 33). The distribu-
tion of the A. glutea posterior to the biceps femoris, the semitendinosus
and, in this specimen, to the internal part of the gluteus superficialis, may
now be demonstrated.

Nn. glutei. There are 5 or 6 of these nerves which are usually described
as the anterior and posterior gluteal nerves.

Nn. glutei anterior. There are three or four nerves in this group. They
pass through the great sciatic foramen and are distributed to the gluteal
and other muscles as follows: one large nerve lying at the anterior side
of the N. ischiadicus passes postero-laterally across the dorsal surface of
the shaft of the ilium and between the middle and deep gluteal muscles
and is distributed to the tensor fasciae latae and the gluteus superficialis as has
been already demonstrated (Pl. IV, 22). Sometimes this nerve sends a
small branch to the gluteus medius. A short distance from its origin it
frequently gives one or more short branches to the gluteus profundus;
a branch from this nerve is also sent to the M. capsularis. The other large
anterior gluteal nerves have a very short course before entering the gluteus
medius; they arise from the lateral side of the plexus but are so completely
hidden from view by the great N. ischiadicus that they are liable to be
overlooked. They accompany the A. glutea anterior through the great
sciatic foramen and immediately enter the gluteus medius.

Nn. glutei posterior (Pl. V, 55, 56). There are two large nerves in
this group, a dorsal or superior, and a ventral or inferior nerve, both of
which apparently arise from the dorso-caudal side of the N. ischiadicus.
The one first given off, the posterior dorsal gluteal (Pl. V, 56), really has
its origin from the 6th lumbar and the Ist and 2d sacral nerves; only a few
fibres however come from the 6th. The nerve extends posteriorly between
the sacro-sciatic ligament and the gluteus medius and upon emerging from
beneath the latter muscle it extends between this muscle and the biceps
femoris to which it is distributed as has already been demonstrated (Pl. IV,
23). One small branch from this nerve is sometimes supplied to the gluteus

39

medius and one to the posterior edge of the gluteus superficialis. The
second posterior gluteal nerve, posterior ventral gluteal, originates from the
Ist and 2d sacral nerves but to a very slight extent however, from the rst
sacral. This nerve also passes posteriorly between the sacro-sciatic liga-
ment and the M. gluteus medius. Eight or ten centimeters from its origin
it divides into two branches of which one enters the semitendinosus im-
mediately dorsal to the ischial tuberosity as already demonstrated (Pl. IV,
25). This branch of the posterior gluteal nerve gives off a filament that
unites with the N. pudendus as already demonstrated. The other branch
of the posterior ventral gluteal nerve emerges near the middle of the outer
surface of the ischial tuberosity and may be seen between the biceps femoris
and the semitendinosus, upon turning aside the latter muscle (Pl. IV, 25");
it is distributed subcutaneously to the region just below the ischial tubero-
sity. In addition to the gluteal nerves already mentioned there is given
off from the N. ischiadicus another small nerve which extends nearly par-
allel to the N. ischiadicus and is distributed to the M. gluteus profundus.
Sometimes this small nerve originates from the gluteal nerve that supplies
the tensor fasciae latae and the gluteus superficialis.

A. profunda femoris (continued).

Draw out the middle one of the three portions into which the biceps
femoris has been cut and note the large A. profunda femoris (and veins)
that enters the muscle a Jittle above the level of the external small tro-
chanter (PI].1V). Cut the vessels, turn back this portion of the muscle as
far as possible and trace the artery to its distribution in the biceps femoris
principally; small twigs are supplied to the gluteus medius, the quadratus
femoris and the adductor magnus.

A. obturatoria (continued).

Remove piecemeal a portion of the semimembranosus and trace the
artery to this muscle; one or more branches go to the semitendinosus and
one to the biceps femoris.

Nerves to the Mm. gemelli, obturator internus and quadratus femoris.

Place the specimen with the gluteal region uppermost, clean up the
N. ischiadicus (Pl. IV, 26) and identify the following muscles—the gemelli,
the tendon of the obturator internus and the quadratus femoris. The
one or two small nerves that supply these muscles originate from the deep
or internal face of the N. ischiadicus at nearly the same level as the posterior
ventral gluteal nerve and lie between the N. ischiadicus and the sacro-
sciatic ligament so that in order to see them the N. ischiadicus must be

40

drawn aside. Near the posterior border of the M. gluteus profundus the
small nerve to the gemelli, etc., (in cases where only one nerve is present),
gives off a small branch which passes through the lesser sciatic foramen
into the pelvic cavity where it divides into two branches one of which
extends anteriorly along the surface of the iliac portion of the M. obturator
internus to which it is distributed; the other branch supplies the other
head of the obturator internus (Pl. V, 50). The main nerve itself crosses
the deep or internal face of the gemelliand the tendon of the obturator internus,
supplies branches to the gemelli and may be seen again at the posterior
border of this muscle where it enters the adjoining quadratus femoris (PI.
IV, 27). Demonstrate this by carefully separating the adjoining borders
of the gemelli and quadratus femoris in order to expose the nerve. The
gemelli and the tendon of the obturator internus may now be transected
in order to expose completely the nerve and its branches as above men-
tioned.

N. ischiadicus (Pl. V, 54; Pl. IV, 26) arises from the 5th and 6th lumbar
and the Ist and 2d sacral nerves; occasionally it receives a branch from the
3d sacral nerve. It passes through the great sacro-sciatic foramen and
between the sacro-sciatic ligament and the M. gluteus medius, crosses a
portion of the gluteus profundus, the gemelli and the tendon of the obturator
internus and the quadratus femoris. Near the level of the gemelli the
N. ischiadicus divides into two terminal branches—peronaeus communis
and N. tibialis (Pl. IV, 29, 34). (It should be kept in mind that the N.
ischiadicus and its branches are named differently by different authors.
The names here given are the names used in the more recent text books of
anatomy and are the terms recommended by the various National Ana-
tomical Societies.) In the femoral region the Nn. peronaeus communis
and tibialis are surrounded by the biceps femoris, the adductor magnus
and the semimembranosus. Near the level of the gemelli there is given off,
either from the N. ischiadicus or from the N. tibialis, a large fasciculus
which extends somewhat posteriorly and supplies the biceps femoris, semi-
tendinosus and semimembranosus (Pl. IV, 28). Demonstrate, by dissect-
ing between the biceps femoris and the semitendinosus and between the
semitendinosus and the semimembranosus. Transect the semitendinosus
at the level of the 3d trochanter and trace the nerve branches to their
respective muscles.

N. peronaeus communis (Pl. IV, 29). The distal portion of the biceps
femoris must now be turned aside, noting the blood-vessels, which must
be cut, that enter the muscle and also the small nerve—peronaeal cutaneous
(Pl. IV, 30, 30')—a branch of the N. peronaeus communis. This small

41

branch appears to go to the biceps femoris but in reality it passes through
the muscle and is distributed subcutaneously to the external face of the
tibial region. The large N. peronaeus communis is given off from the
N. ischiadicus at the level of the gemelli muscle; it lies at the side of the
N. tibialis until it reaches the M. gastrocnemius where it diverges from the
N. tibialis and passes between the external head of this muscle and the
biceps femoris (Pl. IV, 29). Beginning at the posterior border of the biceps
femoris slit the tibial aponeurosis lengthwise the tibia and turn aside the
aponeurosis and the distal end of the biceps femoris (Pl. IV, 10’, 11°).
Now trace the N. peronaeus communis to the place where, between the
M. peroneus (or lateral digital extensor) and the extensor pedis, it dips into
the anterior tibial group of muscles. Shortly before the nerve enters these
muscles it divides into two terminal branches—the N. peronaeus super-
ficialis and the N. peronaeus profundus (Pl. IV, 32, 33). The N. peronaeus
superficialis is much the smaller of the two and is for the most part sub-
aponeurotic. Near its origin it gives off a muscular branch to the M.
peroneus or lateral digital extensor (Pl. IV, 32"). Trace the superficial or
subaponeurotic portion of the nerve (Pl. IV, 32") to its place of distribu-
tion near the middle of the metatarsus. Note the relation of the nerve to
the extensor pedis, peronaeus and to the tibial aponeurosis.

N. peronaeus profundus (Pl. IV, 33). Just as this nerve passes between
the extensor pedis and peroneus it divides into several branches of which
all but one are distributed to the extensor pedis and the tibialis anterior
(Pl. VI, 34). Cut the extensor pedis below the middle of the tibia and draw
it aside. The remaining branch of the peronaeus profundus lies deeply
between the extensor pedis and the tibialis anterior (Pl. VI, 34"). In
tracing this branch to its termination in the digital region the tendons of
the extensor pedis and peroneus may be cut near the middle of the metatar-
sus and drawn aside. As the nerve crosses the tarsus it gives off several
small branches to this region and to the M. extensor digitalis brevis. At
the tarsus the nerve divides into two main portions of which one accompanies
the A. metatarsea dorsalis (lateralis) to the region of the fetlock (Pl. VI,
35); the other portion of the nerve extends obliquely across the anterior
face of the large metatarsal bone and may be traced as far as the fetlock

and often even beyond that joint.

N. saphenus externus arises from the N. tibialis at the level of the third
trochanter (Pl. IV, 35; Pl. VI, 36). It extends along the postero-external
part of the gastrocnemius, accompanied by a vein, to near the beginning
of the tendo Achillis. At this point it occasionally receives a small

42

accessory branch from the N. peronaeus communis (Pl. VI, 31). TheN.
saphenus externus then gains the interval between the tendo Achillis
and the M. perforans and extends the length of this space, immediately
beneath the tibial aponeurosis, accompanied by the V. saphena externa.
Trace the nerve to its subcutaneous distribution at the outer face of the
tarsal and phalangeal regions (Pl. VI, 36).

Demonstrate the popliteal lymph gland, 6 cm. long by 2 cm. wide, in
the space between the biceps femoris and semitendinosus immediately
posterior to the gastrocnemius.

N. tibialis is the larger of the two terminal branches of the N. ischiadicus
(Pl. IV, 34; Pl. VI, 29). It lies beneath the biceps femoris until it reaches
the gastrocnemius. Just as it passes between the two heads of the gastroc-
nemius it gives off, anteriorily, a large fasciculus to the muscles on the
posterior side of the tibia (Pl. VI). To demonstrate the branches of this
fasciculus carefully dissect up the external head of the gastrocnemius and
transect it a little below the middle of its fleshy portion taking care not to
cut the flexor perforatus which 1s partially embedded in the gastrocnemius
(Pl. VI, 11, 11’, 12). The Nn. saphenus externus and peronaeus communis
should also be left intact. The several branches of the fasciculus just
mentioned should now be traced to their respective muscles, viz., one branch
to the external head and one to the internal head of the gastrocnemius;
a somewhat smaller branch to the flexor perforatus. Transect the perfora-
tus a little below the nerve supplied to it and draw aside the proximal part
of the muscle. Trace the remaining branches of the fasciculus to the
popliteus and flexor perforans (Pl. VI). The N. tibialis passes between the
two heads of the gastrocnemius and for a short distance runs along the
posterior surface of the flexor perforatus; it then gradually crosses the
inner face of this muscle and accompanied by a small artery, descends to
the tarsus in the space at the inner side of the leg, between the tendo Achillis
and the flexor perforans. Place the leg with its inner or medial surface
uppermost and expose the N. tibialis in this part of its course taking care
not to injure the one or more small arteries that accompany the nerve.
At the tarsus the N. tibialis divides into two terminal branches—the N.
plantaris medialis and the N. plantaris lateralis. Note very carefully the
relation of the N. tibialis to the internal saphena vein and artery and to the
tibial aponeurosis.

Nn. plantaris medialis and lateralis. These two nerves are the terminal
branches of the N. tibialis. They follow the tendon of the flexor perforans
through the tarsal sheath and, diverging somewhat from each other, descend

43

the metatarsal region on either side of the perforans tendon. Each nerve
is accompanied by a slender artery (A. metatarsea plantaris superficialis)
and by a vein. The N. plantaris lateralis gives off a branch of consider-
able size to the proximal portion of the suspensory ligament. Near the
middle of the metatarsus, the N. plantaris medialis gives off a branch that
runs obliquely across the posterior face of the flexor tendons and joins
the plantaris lateralis alittle above the distal end of the rudimentary
metatarsal bone. At the fetlock each plantar nerve divides into two or
three branches which are identical with those of the thoracic limb.

A.saphena. This small artery was noted when the N. saphenus internus
(p. 32) was dissected. The artery arises from near the middle of the A.
femoralis. It extends along the inner or medial face of the thigh and leg
to near the tarsus where it anastomoses (usually) with a small recurrent
branch of the A. tibialis posterior. The artery is accompanied by the large
V. saphena.

A. femoralis. Turn aside the M. gracilis leaving intact the A. and V.
saphena. Transect the semimembranosus a hand’s breadth (10 cm.) from
its attachment to the epicondyle of the femur and turn back the distal
portion of the muscle. Now trace the A. femoralis from its origin at the
level of the anterior border of the pubis to its termination just before it
passes between the two heads of the gastrocnemius where it is continued
by the A. poplitea. Note the muscles that are related to the artery, viz.,
the sartorius, pectineus, vastus internus and adductor magnus. Note
also its relation to the deep inguinal lymph gland.

Branches of the A. femoralis.

(1) Pudendo-epigastricus or prepubic, see p. 29.

(2) <A. profunda femoris, see p. 36.

(3) A. femoris anterior, see p. 36.

(4) Rami musculares, to the vastus internus, sartorius, gracilis, adduc-
tor magnus and semimembranosus.

(5) A. saphena, see above.

(6) A. nutritia femoris enters the nutrient foramen of the femur.

(7) A. genu (articular branch). This small branch arises from the
A. femoralis a little before the latter passes through the adductor magnus.
It runs near the posterior border of the vastus internus to the inner or
medial surface of the femoro-tibial joint where it ramifies. It also gives
small twigs to the vastus internus and the adductor magnus.

(8) A. femoris caudalis (or A. femoris posterior), is a large vessel which
arises from the caudal or posterior face of the A. femoralis, just before the

44

latter passes between the two heads of the gastrocnemius. Two or three
centimeters from its origin the A. femoris caudalis divides into two branches
as may be seen upon turning aside the biceps femoris. (The external head
of the gastrocnemius may be partially transected close to its origin from
the femur.) One of the branches of the A. femoris caudalis passes upwards
or proximally, a short distance (4 to 6 cm.) between the semimem-
branosus and the biceps femoris and is distributed principally to the latter
muscle; it also gives off two branches, in this specimen, to the vastus
externus. The other and larger branch of the A. femoris caudalis extends
downward and backward close to the posterior margin of the internal
head of the gastrocnemius and is distributed principally to the biceps
femoris and semitendinosus; small branches are also supplied to the gastroc-
nemius and to the popliteal lymph gland. In the present specimen, about
I cm. peripheral to the A. femoris caudalis a small artery arises which passes
between the two heads of the gastrocnemius, immediately posterior to the
flexor perforatus, gives small branches to that muscle and to the perforans
and is continued as a slender vessel which accompanies the N. tibialis.
It unites with a small recurrent branch of the A. tibialis posterior a short
distance above the tarsus. In the present specimen, two additional arteries
originate from the A. poplitea about 4 cm. peripheral to the A. femoris cauda-
lis. The smaller of these twoarteries goes to the external head of the gastroc-
nemius; the larger one is distributed to the distal portion of the biceps
femoris and the vastus externus. The A. poplitea also gives off a small
branch to the internal head of the gastrocnemius. All the above arteries
are accompanied by veins.

A. poplitea is the direct continuation of the A. femoralis. It runs between
the tibia and the Mm. popliteus and flexor perforans as far as to the proximal
part of the tibio-fibular or interosseous space where it divides into the A.
tibialis posterior and the A. tibialis anterior. Cut the M. popliteus a short
distance from its origin on the external epicondyle of the femur and draw
aside the muscle. Dissect between the M. peroneus and the flexor per-
forans. Insert the finger beneath the portion of the flexor perforans that
originates from the external tuberosity of the tibia and the adjoining portion
of the fibula and identify the tibio-fibular space (see skeleton). Taking
care not to injure the underlying artery, cut the perforans close to the
external tuberosity of the tibia and the adjoining portion of the fibula;
draw back the muscle and demonstrate the A. poplitea as mentioned above.
It gives off a branch that enters the intercondyloid space of the femur and
supplies the femoro-tibial joint.

A. tibialis posterior is the smaller of the two terminal branches of the A.
poplitea. Begin the dissection of this artery near its peripheral end, i.e. at

45

its S shaped curve on the medial side of the leg, anterior to the tuber calsis.
Turn back or remove the covering aponeurosis taking care not to cut the
A. and V. saphena, draw aside the small internal head of the flexor perforans
(M. flexor digitalis longus or flexor acessorius) and trace the artery as far
as possible, without cutting muscles, towards its origin. Now returning
to the origin of the artery, draw aside, and at the same time cut the flexor

perforans from its attachment to the posterior face of the tibia sufficiently
to expose the artery.

Branches of the A. tibialis posterior.

(1) Rami musculares to the Mm. popliteus and perforans.

(2) A. nutritia tibiae enters the nutrient foramen of the tibia.

(3) A. tarsea lateralis is a small branch which arises at the first flexure
of the sigmoid portion of the tibialis posterior. It runs between the tibia
and the flexor perforans and is distributed by several small branches to the
tendon and the lateral surface of the tarsus.

(4) One or more small branches from the convexity of the first curve
of the sigmoid portion of the artery to the medial surface of the tarsus.

(5) A. tibialis recurrens is a small artery which arises from the second
convexity of the sigmoid curve of the A. tibilias posterior. It extends
proximad along the N. tibialis and anastomoses with either the A. saphena
or with a branch from the A. femoris caudalis that accompanies the N.
tibialis.

(6) A branch given off from the second convexity of the sigmoid curve
passes between the tendo Achillis and the flexor perforans and is distributed
to the tendon and the region of the tuber calsis. The A. tibialis posterior
ends in two small terminal branches—the A. plantaris medialis and the
A. plantaris lateralis.

A. tibialis anterior. Dissect between the M. peroneus and the tibialis
anterior and draw aside the latter muscle. The A. tibialis anterior is the
larger of the two terminal branches of the A. poplitea. It passes through
the proximal part of the tibio-fibular arch and descends, with two large
veins, on the antero-lateral face of the tibia beneath the M. tibialis anterior.
At the tarsus the artery gives off the A. tarsea perforans which passes
through the tarsal canal and anastomoses with the two plantar arteries
or sometines with only the plantaris externus to form the arcus plantarus or
plantar arch. The trunk of the A. tibialis anterior is continued along the
metatarsus as the A. metatarsea dorsalis (lateralis). The A. tibialis
anterior supplies branches to the Mm. extensor pedis, tibialis anterior, and
several branches to the tarsal joint. Near its middle the A. tibialis anterior
gives off a variable branch—A. peronea—which descends along the fibula

46

under the M. peroneus to which it supplies small branches; it also gives
off a cutaneous branch.

A. plantaris medialis and A. plantaris lateralis.

These two small terminal branches of the tibialis posterior vary some-
what in different specimens. The following disposition however is common.
Each plantar artery descends with the respective plantar nerves, on either
side of the perforans tendon, to the proximal part of the metatarsus where,
between the flexor tendon and the suspensory ligament, they unite with the
A. tarsea perforans to form the arcus plantaris or plantar arch. The flexor
tendons should be cut and turned aside. Sometimes the A. plantaris
medialis does not join the plantar arch but is continued as the small satel-
lite vessel of the N. plantaris medialis. Four plantar metatarsal arteries
originate from the plantar arch. The two small superficial arteries, meta-
tarsea plantaris superficialis medialis and lateralis accompany the plantar
nerves on either side of the flexor tendons and unite with the A. metatarsea
dorsalis or with the corresponding digital arteries. Sometimes, as men-
tioned above, one of the superficial plantar metatarsal arteries is the direct
continuation of the A. plantaris medialis. Transect and draw aside the
suspensory ligament.

The two deep plantar metatarsal arteries, Aa. metatarsea plantaris
profundus medialis and lateralis, descend between the suspensory ligament
and the corresponding rudimentary metatarsal bones and unite near the
fetlock with the A. metatarsea dorsalis. Of the two deep metatarsal
arteries the medial or internal one is much the larger and supplies the
nutrient artery to the large metatarsal bone.

A. tarsea perforans arises from the A. tibialis anterior, passes through the
tarsal canal and unites with the plantar arteries or with the external one
only, to form the plantar arch.

A. metatarsea dorsalis (lateralis) is the direct continuation of the A. tibialis
anterior. It crosses the anterior surface of the tarsal joint and descends,
at first, in the oblique vascular groove on the lateral face of the proximal
part of the principal metatarsal bone and then in the groove formed by
the principal and the lateral rudimentary metatarsal bones. Near the
distal end of the rudimentary metatarsal the artery passes between the
two bones and divides on the posterior face of the principal metatarsal,
between the two divisions of the suspensory ligament, to form the A. digitalis
medialis and the A. digitalis lateralis. These two arteries and their branches
are similar to those of the thoracic limb.

PLATE IV

LATERAL SURFACE

External angle of ilium.
Tuber ischii.
External small or third trochanter,
Lateral epicondyle of femur.
M. obliquus abdominis externus.
6. M. tensor fasciae latae with posterior edge drawn aside. ;
M. gluteus superficialis; (the gluteal apopeurosis has been removed).
M. gluteus medius.
g. M. gluteus profundus (in part.)
10, 10’, 11, 11’.. M. biceps femoris.
12,12’. M. semitendinosus.
13. M. semimembranosus.
14. Mm. gemelli.

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15. M. quadratus femoris.

16. M. vastus externus.

17. M. gastrocnemius.

18. M. soleus.

19. M. peroneus or extensor digitalis lateralis.

20. M. extensor pedis or extensor digitalis longus.
21. M. flexor perforans.

22. One of the anterior gluteal nerves.

23. Gluteal nerve to M. biceps femoris.

24. Sacro-sciatic ligament.

25, 25’. Posterior ventral gluteal nerve.

26. N. ischiadicus.

27. Nerve to the Mm. gemelli, obturator internus and quadratus femoris.
28. Nerve fasciculus to the Mm. biceps femoris, semitendinosus and: semimembranosus.
29. N. peronaeus communis.

30, 30’. N. peroneal cutaneous.

31. Small filament to the femoro-tibial joint.

32. N. peronaeus superficialis.

32’. Nerve branch to M. peroneus.

32’’. Superficial or subcutaneous branch of N. peronaeus superficialis.

33. N. peronaeus profundus.

34. N. tibialis.

35. N. saphenus externus.

36. Nerve filament to M. soleus.

SSEVQy

PLATE V
MEDIAL VIEW.

1-6. Lumbar vertebrae.
1’-5’. Sacral vertebrae.
1-6", Coccygeal vertebrae.
7. Pelvic symphysis.
8, 8’. M. psoas parvus.
9. M. psoas magnus.
Io. M. iliacus.

11,11’. M. sartorius.
12. M. obliquus abdominis internus.
13. M. transversus abdominis.
14. M. rectus femoris.
15. M. vastus internus.
16. M. gracilis.
7. Portion of prepubian tendon.

T7,

18, 18’. M. obturator internus.
19. M. sacro-coccygeus.

20, 20’. M. compressor coccygeus.
23, 21’. M. retractor ani.

22. M. retractor penis.

23. M. recto-coccygeus.

24. M. sphincter ani externus.
25. M. sphincter ani internus.
26. Sacro-sciatic ligament.

27. Aorta.

28. A. mesenterica posterior.

39. A. circumflexa iliaca.

20. A. iliaca (of right side).

30’ Cut end of left A. iliaca.

31. Truncus pudendo-epigastricus (prepubic artery).

. obturatoria.
. femoralis.
42. Large vein in subpubic groove.
43. V. pudenda externa.
XVIII. Last thoracic nerve. I-VI. Lumbar nerves.
I’-IV’. Sacral nerves. :
44. Posterior mesenteric ganglion of the sympathetic nerve (just below 44).
45. Sympathetic nerve trunk.
46, 46’. N. femoralis.
47. N. saphenus internus. :
48. Branch of N. saphenus internus to M. sartorius.
49. N. obturatorius. :
50. Small nerve to the M. obturator internus.
51. Pelvic plexus. . oon
52. Anterior gluteal nerve to the Mm. tensor fasciae latae and gluteus superficialis.
53. Nerve to the M. gluteus profundus.
54. N. ischiadicus.
55- Posterior ventral gluteal nerve.
56. Posterior dorsal gluteal nerve.
57,57’. N. pudendus. ; ' ;
57”. N. dorsalis penis (of the left side) a continuation of the N. pudendus.
58. Small nerves to the pelvic plexus. ;
59. Branch of N. haemorrhoidalis to the M. retractor ani.
-60. N. haemorrhoidalis.
61. Branch of N. haemorrhoidalis to the M. compressor coccygeus.
62. Nerve branch to rectum.
63. Deep inguinal lymph gland.
64. External iliac lymph glands.

32. <A. femoris anterior.
33. <A. femoralis.
34. A. iliaca interna.
35. A. sacralis lateralis.
36. A. glutea anterior.
37. A. pudenda interna.
38. A. obturatoria.
39. A. umbilicalis.

rus

Vv

PLATE VI
LATERAL VIEW OF PELVIC LIMB

External small or third trochanter.
Lateral epicondyle of femur.
Os calsis.
Lateral rudimentary metatarsal.
. Principal metatarsal.
5’. M. vastus externus.
M. adductor magnus.
M. semimembranosus.
M. semitendinosus.
9, 10. M. biceps femoris (turned aside). . .
11, 11’. Lateral or external head of M. gastrocnemius (transected and the distal portion turned aside).
11’. Medial or internal head of M. gastrocnemius.

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12. M. flexor perforatus (a short section has been removed).
13. M. popliteus.

14. M. flexor digitalis longus.

15. M. soleus.

16. M. flexor perforans.

17. M. peroneus or extensor digitalis lateralis.

18. M. tibialis anterior.

19. M. extensor pedis or extensor digitalis longus.
20. M. extensor brevis.

21. M. interosseus lateralis.

22. M. lumbricalis lateralis.

23, 23’, 23”. Tibial and metatarsal aponeurosis.

24. Suspensory or suprasesamoid ligament.

25. Ligament of ergot.

26. A. metatarsea dorsalis (lateralis).

27. A. digitalis lateralis.

28. V. digitalis lateralis.

29. N. tibialis.

30. N. peronaeus communis.

31. Small branch from N. peronaeus communis to N. saphenus externus.

32, 32’. N. peronaeal cutaneous.

33. N. peronaeus superficialis. ws

33’, 33”. Muscular and cutaneous branches of N. peronaeus superficialis.

34, 34’. N. peronaeus profundus. : ;
35. Branch of N. peronaeus profundus accompanying the A, metatarsal dorsalis (lateralis).
36, 36’. N. saphenus externus.

37. N. plantaris lateralis. cs : .

38. Communicating branch for the N. plantaris medialis to the plantaris lateralis.

39, 40, 41. Anterior, middle and posterior branches of N. digitalis lateralis.

42. Portion of N, digitalis in the dorsal groove of third phalanx.

PLATE VII
DIAGRAM OF THE LUMBO-SACRAL NERVE PLEXUS

1-6. Lumbar vertebrae.

1-5’. Sacral vertebrae.
1-6". Coccygeal vertebrae.
I-VI. Ventral branches of lumbar nerves.
I’-V’. Ventral branches of sacral nerves.
I’’-V’"". Ventral branches of coccygeal nerves.
7. Gangliated nerve-trunk of the sympathetic nerve.
8. Ramus communicans.
g. N. ilio-hypogastricus.

10. N. ilio-inguinalis.

11. N. spermaticus externus.

12. N. cutaneous femoris lateralis.

13. Branch to M. psoas parvus.

14. N. femoralis.

15. Branch to M. iliacus.

16. N. obturatorius.

17-20. Nn. glutei anterior.

21. N. ischiadicus.

22. Posterior ventral gluteal nerve.

23. Posterior dorsal gluteal nerve.

24. N. pudendus.

25. Small nerves to the pelvic plexus.

26. Nerve to the M. retractor ani.

27. N. haemorrhoidalis.

28, 29. Fourth and fifth sacra] nerves.

30. First coccygeal nerve.

31. Nerve trunk formed by branches of the coccygeal nerves.

32-36. Coccygeal nerves.

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