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http://www.archive.erg/d ails/C31924000364822

Croso.

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The Bdinburgh Veterinary Series

General Hditor—
0. CHARNOCK BRADLEY, M.D., D.Sc, M.R.C.V.S.

THE LIMBS OF THE HORSE

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THE

TOPOGRAPHICAL ANATOMY

OF THE

LIMBS OF THE

BY

HORSE

O. CHARNOCK BRADLEY

M.D., aie bese
L, ies CK) V:
IPARATIVE

EDINBURGH

» >
randoie, UNIVERSITY OF EDINBURGH

W. GREEN & SON, LIMITED

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PREFACE.

WERE it not that the conventional preface affords a means by which
an author may convey his grateful thanks to those from whom he has
received advice and assistance, the present book would have been sent
forth without the usual preamble. Seeing, however, that the illus-
trations form a highly important, helpful, and essential part of the
book, it would be worse than ungrateful to neglect this opportunity
to thank Mr. James T. Murray for the infinite care he has bestowed
upon the drawing of the various dissections. The publishers were
indeed fortunate in securing the services of one whose long experience
in the illustration of works on anatomy has given him knowledge
that, combined with an artistic skill it would be impertinence in me
to praise, places him in the forefront of anatomical illustrators. It
is greatly to be deplored that the labour difficulties of peace have not
spared the workshop of the blockmakers, but have resulted in the
frequent neglect of Mr. Murray’s instructions respecting the reduction
in size of his drawings. Some of the figures have been reduced beyond
the carefully determined scale indicated on the originals, and some
companion figures have not been reduced to scale. Unfortunately,
these errors could have been rectified only at much expense and after
long delay.

To Dr. E. B. Jamieson, of the University of Edinburgh, thanks
are due for help in the revision of the footnotes in which the derivation
of anatomical terms is indicated. It is hoped that these brief notes
will lead the student—and possibly others—to realise that terms are
more than mere collections of letters.

Finally, I cannot abstain from thanks to the publishers, who have
been most generous in meeting all suggestions, and in permitting the

free use of illustrations.
0. C. B.

November 1919.

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CONTENTS.

THoracic Limp . ‘ ‘ : ; ; 1
Tye Hoor anp 17s ConrEents . ‘ . : : : 78
ARTERIES oF THORACIC Limp . 5 : ‘ 93
Nerve anp Bioop Suppiy oF tHE MusciEs oF THE THoRacic Limp 94
Petvic Limp F ; : ; ‘ 2 96
ARTERIES OF PELvic Limp P 3 : : . 164
NERVE AND Bioop SuprLy oF THE MuscLes oF THE PeEtvic Lime . 165
INDEX. ; : : ‘ F F . 167

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LIST OF ILLUSTRATIONS.

. Cutaneous nerves of the thoracic limb

. Lateral wall, floor, and contents of the axilla

. Superficial dissection of the shoulder and arm

. Dissection of the region of the shoulder ;

. Lateral aspect of the scapula and scapular cartilage, “with areas of

muscular attachment

. Medial aspect of the scapula and duapulee cantilonty with areas of

muscular attachment

. Glenoid cavity of the scapula, with: areas of sincera aiiaehmenta in ite

neighbourhood .

. Deep dissection of the shoulder andl arm

. Dissection of the medial aspect of scapular region doen

. Deep dissection of the medial aspect of the arm

. Diagram of the arteries of the thoracic limb

. Diagram of the veins of the thoracic limb .

. Lateral aspect of the humerus, with areas of muscular attachment

. Anterior aspect of the humerus, with areas of muscular attachment
. Medial aspect of the humerus, with areas of muscular attachment

. Posterior aspect of the humerus, with areas of muscular attachment
. Proximal end of the humerus, with areas of muscular attachment

. Distal end of the humerus, with areas of muscular attachment

. Evolution from pentadactyl to monodactyl condition in the manus of

the horse

. Dissection of the lateral aspect of the forearm and carpal region :

. Dissection of the medial aspect of the forearm and carpal region .

2, Lateral aspect of the radius and ulna, with areas of mnuaerilay attachment
23. Anterior aspect of the proximal part of the radius and ulna, with areas

of muscular attachment

. Medial aspect of the proximal part of the sites and itina, swith areas

of muscular attachment

. Posterior aspect of the radius and ulna, with areas of eee attachment
. Lateral aspect of the carpus, etc., with areas of muscular attachment
. Dorsal (anterior) aspect of ave carpus, ad with areas of muscular

attachment

. Medial aspect of the carpus, Co with areas of muscular attachment
29.

Volar (posterior) aspect of the carpus, etc., with areas of muscular
attachment

. Key-outline of the ‘herale limb to indent the Tove ae the bramisy eee

sections illustrated in subsequent figures

. Section across the forearm at the level indicated by A in Fig. 30
. Section across the forearm at the level indicated by B in Fig. 30
. Section across the forearm at the level indicated by C in Fig. 30
. Section across the forearm at the level indicated by D in Fig. 30
. Section across the forearm at the level indicated by E in Fig. 30
. Section across the most distal part of the forearm at the level indibated

by Fin Fig. 30+ nicitized by Microsoft®

PAGE

23

LIST OF ILLUSTRATIONS

. Medial aspect of the carpus, metacarpus, and digit
. Lateral aspect of the skeleton of the digit with areas of cnnadiilen

attachment

. Volar (posterior) aspect of the skeleton of the digit ‘with areas of

muscular attachment

. Section across the metacarpus at the level indicated by Gi in Fig. 30

. Section across the metacarpus at the level indicated by H in Fig. 30

2. Section across the metacarpus at the level indicated by I in Fig. 30

. Section across the distal end of the metacarpus as indicated by J in Fig. 30
. Section across the first phalanx at the level indicated by K in Fig. 30

. Section across the first phalanx at the level indicated by L in Fig. 30

. Lateral aspect of the shoulder joint : : j

. Medial aspect of the shoulder joint

. Anterior aspect of the elbow joint .

. Medial aspect of the elbow joint

. Lateral aspect of the carpal articulations

. Dorsal (anterior) aspect of the carpal pieulakians:

. Medial aspect of the carpal articulations

. Lateral aspect of the matrix of the hoof

. Volar aspect of the matrix of the hoof A

. Outline of the volar and plantar aspects of the hoof of the thoracic and

pelvic limbs

. Inner surface of the hoof

. Volar aspect of the hoof

. Longitudinal section of the digit

. Key-outline to indicate the position of the sections ‘Nusrat 4 in Figs.

60 and 61

. Transverse section of the foot at the level indiuated by jive Ain Fig. 59
. Transverse section of the foot at the level indicated by line B in Fig. 59
. Lateral aspect of the phalanges and the cartilage of the third phalanx, to

show the position of the joint and cartilage relative to the surface of
the limb and the border of the hoof

. The tendons and ligaments of the lateral aspect of the digit

. Ligaments of the volar (posterior) aspect of the digit

: Superficial dissection of the medial aspect of the thigh (female)

. Dissection of the medial aspect of the thigh after removal of the sartorius

and gracilis muscles (imale)

. Deep dissection of the medial aspect of the ‘thigh .

. Diagram of the arteries of the pelvic limb .

F Diagram of the veins of the pelvic limb :

. Ventral aspect of the hip bone, with areas of muscular éthacinant

. Cutaneous nerves of the pelvic limb

. Superficial dissection of the gluteal region and lateral Banas of the thigh
. Deep dissection of the gluteal region and lateral aspect of the thigh

. Lateral aspect of the hip bone, sacrum, and associated ligaments, with

areas of muscular attachment

. Lateral aspect of the femur, with areas of cineca and ligamentous

attachment

. Anterior aspect of the fees with areas ‘of muscular and ligamentous

attachment

. Medial aspect of the enter, ath areas of siteaeula and ligamentous

attachment

. Posterior aspect of the fetus with areas of mogseulan dina ligamentous

attachment

. Proximal end of the Reantiry with areas of mneetln attachument

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PAGE

116

118

119
120

ria.

. Distal end of the femur, with areas of muscular and ligamentous

106.
107.
108.
109.
110.
111.
112.
113.
114.
115.

LIST OF ILLUSTRATIONS

attachment

. Key-outline of the pelvic inh to indicate the level of the famavanes

sections illustrated in subsequent figures

. Section across the thigh at the level indicated by M in Fig: 81
. Anterior aspect of the hip joint é

. Medial aspect of the hip joint

- Superficial dissection of the medial aspect a the leg and vor

. Superficial dissection of the lateral aspect of the les and tarsus

. Deep dissection of the popliteal region

. Lateral aspect of the proximal part of the tibia and fibula, wit, areas of

muscular and ligamentous attachment

. Anterior aspect of the proximal part of the tibia and fibula, with areas

of muscular and ligamentous attachment

. Medial aspect of fis tibia and fibula, with areas of muscular and

ligamentous attachment

. Posterior aspect of the tibia and fibula, with areas of itieientlar nied

ligamentous attachment

2. Dissection of the dorsal (anterior) aspect of the tarsal region
. Section across the pelvic limb at the line indicated by N in Fig. 81
. Section across the proximal part of the leg at the level indicated by

O in Fig. 81

. Section across the leg at the level indivated by Pi in Fig. 81
. Section across the lea at the level indicated by Q in Fig. 81
. Section across the les at the level indicated by R in Fig. 81
. Section across the most distal part of the leg at the level indicated by

Sin Fig. 81

. Section across the tarsus at the level indicated by T in Fig. 81
100.
101.
102.
103.
104.
~ 105.

Section across the tarsus at the level indicated by U in Fig. 81

Lateral aspect of the tarsus, with areas of muscular shéaehment : P

Dorsal (anterior) aspect of the tarsus, with areas of muscular attachment

Medial aspect of the tarsus, with areas of muscular attachment .

Plantar (posterior) aspect of the tarsus, with areas of muscular attachment

Section across the proximal end of the metatarsus at the level indicated
by V in Fig. 81.

Section across the metatarsus at the level indicated by Wi in Fig. 81

Section across the metatarsus at the level indicated by X in Fig. 81

Lateral aspect of the femoro-patellar and femoro-tibial articulations

Anterior aspect of the femoro-patellar and femoro-tibial articulations

Posterior aspect of the femoro-tibial articulation

Proximal end of the tibia, with areas of ligamentous piscine

Proximal end of the tibia, with the ligsments and menisci attached thereto

Lateral aspect of the tarsal articulations

Dorsal (anterior) aspect of the tarsal arrionlabigna

Medial aspect of the tarsal articulations

4

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134

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16L
162

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THORACIC LIMB.

BECAUSE it affords the greatest convenience to the dissectors of other
parts of the body, the dissection of the thoracic limb should begin with
the animal on its back. In this position the pectoral region offers
itself for examination.

The dissector should note the rounded prominence, formed by
the superficial pectoral muscle, extending from the cranial end
of the sternum to the limb. The prominence is bounded laterally
by the lateral pectoral groove, which marks the line of contact of
pectoral and brachiocephalic muscles. In the middle line, between
the pectoral prominences, is the shallow median pectoral groove, which
bifurcates at the manubrium of the sternum, the two limbs of the
groove diverging, each to join the lateral pectoral groove in the
shallow supraclavicular fossa.

The position of the caudal border of the superficial pectoral muscle
is marked by a distinct fold of skin, but the limits of the deep pectoral
muscle cannot be defined on the surface of the body.

Dissection.—Make an incision through the skin in the middle line
of the body extending the full length of the sternum. A second
incision, transverse in direction, should then be carried from the
sternum to the level of the elbow joint. The two flaps of skin thus
marked out must be raised from the underlying pectoral mass of
muscles. As this is being done, note must be taken of small cutaneous
nerves and vessels which pierce the pectoral muscles close to their
sternal attachment. Larger cutaneous nerves, derived from the sixth
cervical spinal nerve (n. supraclavicularis), will be seen crossing the
surface of the superficial pectoral muscle.

Clean the surface of the superficial pectoral, taking care to preserve
a vein of some size (v. cephalica) and a small artery (a. transversa scapule)
which will be found at its cranial border.

The thin fascia (fascia pectoralis) which covers the surface of the
pectoral muscles furnishes a layer that passes on to the lateral face
of the triceps muscle, and thence becomes continuous with the scapular
fascia. <

M. PECTORALIS SUPERFICIALIS.—The superficial pectoral’ muscle is
generally described as divisible into two parts. The more cranial is

DiGitedls by wnt Bseiepon’

2 TOPOGRAPHICAL ANATOMY OF

known as the clavicular portion (pars clavicularis), on the assumption
that it corresponds to that part of the pectoral which arises from. the
clavicle! in those animals in which this bone exists. In the horse,
where the clavicle has disappeared, the muscle has shifted its origin
to the nearest bone, namely, the sternum. The caudal or sternocostal ?
part (pars sternocostalis) of the muscle is more extensive and composed
of bundles of fibres converging somewhat as they proceed towards the
elbow joint.

It is not altogether easy to separate the clavicular and sterno-
costal parts of the pectoral muscle; nor is it of much profit to do so,
If the dissector desires to make the separation he should look care-
fully for a very indistinct groove at no great distance from the
cranial border of the muscle, and, in effecting the separation, he
should bear in mind that the sternocostal portion of the muscle
overlaps the clavicular.

The origin of the superficial pectoral muscle is from the sternum
from its cranial end to a level with the sixth rib-cartilage. It will
be noticed that some of the fibres spring from a fibrous partition
between the muscles of the two sides of the body. Its insertion is
into the crest of the greater tubercle of the humerus and to the
fascia lining the inner aspect of the forearm.

Dissection.—The superficial pectoral muscle is to be reflected by
making a longitudinal incision through it at a short distance from
its sternal attachment. Care should be taken to avoid injury to the
underlying deep muscle, as the two pectorals are generally intimately
associated with each other close to the sternum. As the superficial
muscle is being raised and turned outwards, its nerve of supply should
be noted, as it pierces the narrow interval between the two parts of
the deep muscle.

The surface of the deep pectoral muscle must be cleaned and its
borders defined. In doing this, an examination should be made of a
‘triangular space bounded by the pectoral and brachiocephalic muscles
and a strong band of the cutaneous muscle attached to the extremity
of the sternum. In examining the contents of the space the dissector
of the limb should work along with those who are dissecting the head
and neck. The triangle contains a group of lymph glands, the cephalic
vein, and the transverse scapular artery. Deep down in the space is
the jugular vein.

The definition of the caudal border of the deep pectoral must be
conducted with care, for it is overlapped by the cutaneous muscle, and
associated with it are the external thoracic vein and the caudal pectoral
nerve.

1 Clavicula (L.], dim. of clavus, a nail, or of clavis, key ; probably from «dels
[Gr.], key or bolt, collar-bone. The clavicle of the horse has disappeared, and is
“now represented by a fibrous line in the brachiocephalic muscle. In the dog it
is a rudimentary bone embedded in that muscle.

? Sternum [L.], orépvov (sternon) [Gr.], breast or chest. Costa [L.], rib.

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THE LIMBS OF THE HORSE 3

From cervical nerves.

5
|
'
1
|
!
'
,
‘
|
'
!

*h

From thoracic nerves

Se SS
- SSS
es SS

sa

“SS
SAG,
SAA

IS,

From thoracie
nerves.

~~
ww

\

a
— —

—~

- - —- From the sixth
cervical nerve
(n. supraclay-
icularis).

N. cutaneus brachii
~~ lateralis.
~ ---.N. cutaneus antibrachii
dorsalis.

From intercostal nerves.

,
‘

From n. pectoralis caudalis. N p

\

Ramus cutaneus volaris ofn. ulnaris. — — -

N. cutaneus antibrachii
lateralis.

’

Ramus superticialis of n. ulnaris.- — --- -

N, volaris lateralis. - --_ -. _} 44)

Communicating branch from n. volaris-- - - - - - N
medialis. :

Fic. 1.—QutangowsNewyr eyed the Di@acic Limb,

4 TOPOGRAPHICAL ANATOMY OF

M. PECTORALIS PROFUNDUS.—The deep pectoral muscle is readily
separated into two distinct parts, the prescapular! and humeral (pars
praescapularis: pars humeralis).

The prescapular part takes origin from the sternal end of the
first four rib-cartilages and the immediately adjacent part of the
sternum. Its insertion cannot be determined at the present time,
because the muscle disappears by sweeping in a dorsal direction along
the cranial border of the scapula under cover of the brachiocephalic
muscle. It will ultimately be found on the surface of the supra-
spinous muscle,

The humeral part has a much more extensive origin, part of it
being visible before the superficial pectoral muscle was reflected. Some
of the bundles of the deep pectoral spring from the elastic covering
of the oblique and straight abdominal muscles. Others arise from
the sternal ends of the rib-cartilages from the eighth (sometimes the
ninth) to the fifth inclusive, and from the adjacent part of the sternum.
From this widespread origin the bundles converge with a varying
degree of obliquity, and the muscle is inserted mainly into the lesser
tubercle of the humerus. In addition, some of the fibres are attached
to the tendon of origin of the coracobrachial muscle and the fascia
overlying the tendon of the biceps.

Dissection.—Cut across both portions of the deep pectoral muscle
about midway between the limb and the sternum. When the cut ends
have been turned aside, the axilla and its contents are exposed to view.
The contents are numerous, and must be cleaned by the careful removal
of the loose tissue that surrounds them.

AXILLA—The axilla® is largely an artificial space produced by dis-
section. In the living animal it is merely a narrow interval between
the limb and the side of the thorax filled with very loose tissue that
allows of freedom of movement. When the dissection is completed,
the space has considerable dimensions, and may be described as possess-
ing fairly definite boundaries. The lateral wall is formed by the
prescapular part of the deep pectoral, and the subscapular, teres major,
and latissimus dorsi muscles. The medial wall is formed by the
wall of the chest, with the associated intercostal, ventral serratus,
and transverse thoracic muscles. The lateral and medial walls meet
at a very acute angle dorsally, but separate somewhat as they are
followed in a ventral direction. Ventrally the axilla is closed by the

1 Scapule [L.], shoulder-blades, back of shoulders ; cKardyvy (scapané) [Gr.],
a digging tool.
2 Axilla [L.] (dim. of ala, wing), arm-pit.

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THE LIMBS OF THE HORSE 5

M., latissimus dorsi
M., teres major.
M. rhomboideus thoracalis.
M. serratus ventralis.

A. transversa colli :
N. thoracalis II. -

N. thoracalis I. oe,

N. cervicalis VIII.
N. cervicalis VII.
N. cervicalis VI.

LY U

UN

“TMs

\
M. subscapularis.
Ti

N. thoracalis longus. -

N. thoracodorsalis. -
Nn, subscapulares. i Ye LT]
N. musculocutaneus.

N medianus,

N. pectoralis caudalis.
N. axillaris.
N. ulnaris,

A. thoracoacromialis.
A. axillaris, - -

N. radialis.

A. transversa scapule.- -
N. pectoralis cranialis. -

V. axillaris. -
A, thoracica externa. -

Lymphogl4nidule axillares. ~
M. pectoralis superficialis. -~
M. pectoralis profundus ~

(pars praescapularis).
A. thoracodorsgalis,

V. thoracodorsalis. ”

,
M. tensor fasciee antibrachii. ’

rd
V. thoracica externa. /

M. pectoralis profundus

(pars humeralis).

Fic. 2,—Lateypd able Booryrersewents of the Axilla.

6 TOPOGRAPHICAL ANATOMY OF

deep pectoral muscle. Caudally the space is bounded by the latissimus
dorsi and cutaneous muscles, while cranially its limits are not very
precise, but merge into the triangular interval that corresponds in
position to the supraclavicular fossa on the surface of the body.

V. AXILLARIS.—The axillary vein is the largest and most ventral
vessel now exposed. It forms the continuation of the brachial vein,
and, running to the border of the first rib, ends by joining the jugular
vein. Its tributaries are the external thoracic, subscapular, and
thoraco-acromial veins.

A. AXILLARIS.—The axillary artery is a continuation of the sub-
clavian, and is arbitrarily considered to begin at the border of the
first rib. Crossing the axilla obliquely, it ends on a level with the
distal border of the teres major muscle, and is continued onwards in
the arm by the brachial artery. The branches of the axillary artery
are (1) the omocervical trunk ; (2) the external thoracic artery ; (3) the
thoraco-acromial artery; and (4) the subscapular artery. Only the
first two demand examination at this stage of the dissection.

TRUNCUS OMOCERVICALIS.—The omocervical! trunk varies greatly
in length. Arising from the axillary close to the border of the first
rib, it soon divides into two branches. One of these, the ascendiny
cervical artery (a. cervicalis ascendens), turns into the neck between
the omohyoid and brachiocephalic muscles, and need not be followed
further by the dissector of the limb.

The other branch of the omocervical trunk is the transverse scapular
artery (a. transversa scapule), which lies at first under brachiocephalic
and deep pectoral (prescapular part) muscles. It soon gains the lateral
pectoral groove, where it has already been found between the brachio-
cephalic and superficial pectoral (clavicular part).

A. THORACICA EXTERNA.—The external thoracic artery leaves the
caudal border of the axillary close to the first rib. Coursing in a
caudal direction along the deep face of the deep pectoral muscle, it
supplies this as well as the overlying superficial pectoral.

V. THORACICA EXTERNA.—The so-called external thoracic vein is
not, strictly speaking, a satellite of the artery of the same name,
though a small branch of the artery may be found alongside the vein
in the later part of its course. Beginning underneath the skin in
the region of the flank, the vein pierces the cutaneous muscle and
gains the lateral border of the deep pectoral muscle, where it is
related to the caudal pectoral nerve. Gaining the axilla, where it
is often joined by thoracodorsal vein, it generally ends by opening
into the axillary vein, but may terminate in the brachial.

16 Smos) [Gr.], sl . Cornea (L. kK.
Spos OHhteed By MicTosOHe® > Bee!

THE LIMBS OF THE HORSE 7

Dissection.—It will facilitate the examination of the brachial plexus of
nerves if the axillary vein and artery are cut across close to the first rib.

In cleaning the brachial plexus the dissector will be well advised to
work solely from the trunk towards the limb. This will diminish the
chance of a false division of nerves.

PLEXUS BRACHIALIS.—The brachial plexus! is the broad band of
nerves that appears between the two parts of the scalenus muscle,
and is formed by the ventral divisions of the sixth, seventh, and eighth
cervical, and the first and second thoracic nerves. The seventh and
eighth cervical and the first thoracic contribute most to the plexus;
only comparatively slender contributions are furnished by the sixth
cervical and second thoracic nerves.

From the narrow interval between the two portions of the scalenus
muscle, where its caudal border is in contact with the first rib, the
plexus sweeps in a caudal and ventral direction into the axilla and divides
into the following branches :—Suprascapular, subscapular, musculo-
cutaneous, axillary, radial, median, ulnar, thoracodorsal, pectoral, and
long thoracic nerves.

With the exception of the three last-named, these nerves are
distributed to the limb. At the present time it will suffice to identify
them and leave their fuller examination until later.

‘N. rHoracoporsaLis.—The thoracodorsal nerve pursues an oblique
course across the medial face of the scapular region, and ends in the
latissimus dorsi muscle.

Nw. PECTORALES.—The pectoral nerves may be divided into two
groups :—(1) The cranial nerves (nn. pectorales craniales) are three
or four in number, and supply the cranial part of the pectoral mass of
muscles as well as a part of the brachiocephalic muscle. (2) A caudal
pectoral nerve (n. pectoralis caudalis) furnishes twigs to the remainder
of the pectoral mass and the cutaneous muscle. It has already been
seen in company with the external thoracic vein at the border of the
deep pectoral muscle.

N. THORACALIS LONGUS.—The long thoracic nerve is somewhat
isolated from the rest of the branches of the brachial plexus, inasmuch
as it clings closely to the surface of the ventral serratus muscle, of
which it is the nerve of supply.

M. SERRATUS VENTRALIS.—The extensive ventral serratus * muscle
may be regarded as taking origin from the rough triangular
areas on the costal surface of the scapula and the adjoining part
of the scapular cartilage. From this origin the fibres diverge, with
the result that the muscle has a triangular or fanlike outline. The

1 Plexus [L.], plaiting, from plecto, to plait, braid, or interweave.

2 Serratus [L.], sieshigely seprAdrdeamite@'re, a saw.

8 TOPOGRAPHICAL ANATOMY OF

insertion of the muscle is to the transverse processes of the last four
or five cervical vertebrae, and the first eight or nine ribs in the
neighbourhood of the junction of the rib-bone and the rib-cartilage.
The serrated character of the border of the muscle is best marked
at its insertion into the fifth to ninth ribs. In this region it will
be observed that the precise outline of the muscle is somewhat
obscured by an overlapping of the yellow, elastic tunic that clothes
the abdominal muscles.

M. LATISSIMUS DORSI.—This extensive muscle cannot be completely
examined at this stage of the dissection, but its identity should be
established.

M. oMOHYOIDEUS.—Being a muscle of the neck, only the origin of
the omohyoid'—from the fascia over the subscapular muscle near the
shoulder joint—need be examined by the dissector of the limb.

Dissection.—The brachial plexus should be severed close to the point
at which it appears between the two parts of the scalenus muscle. Next
cut through the serratus ventralis a short distance from its scapular
attachment. The origin of the omohyoid muscle should also be freed.

The body must now be turned into such a position as will permit
the dissection of the lateral scapular region. Though all the muscles
(with the exception of the latissimus dorsi) now to be examined are
attached to the scapula, their origins are very widespread. The
trapezius and rhomboid extend far into the neck, while the latissimus
dorsi has part of its origin as far distant as the loins. It is advisable,
therefore, to make an extensive surface examination before beginning
to turn aside the skin. The spine of the scapula can generally be
identified and palpated. Cranial to it is a sloping, elongated pro-
minence, produced by the supraspinous muscle and the prescapular
portion of the deep pectoral, bounded by a shallow groove that marks
the junction of the neck and shoulder. Caudal to the scapular spine
is a broader area corresponding to the infraspinous and deltoid
muscles. An oblique groove indicates the border of the latter muscle,
and ventral and caudal to it is a distinct swelling, reaching to the
region of the olecranon, caused by the triceps.

Dissection.—A longitudinal incision should be made along the mid-
dorsal line from the level of the epistropheus to the lumbar region.

A vertical incision is now carried from tbe interscapular region (withers)

to well beyond the shoulder joint. The two flaps of skin thus demar-

cated are now to be turned aside. Immediately under the skin is the

cutaneous muscle, which, over the scapula, is very thin, but becomes
thicker as it is followed over the wall of the thorax. Its dissection from

1 Guos (Gmos) [Gr.], shoulder. toecdijs [Gr.], U-shaped, from the resemblance of

the human hyoid bone to Padwiked by Microsoft®

THE LIMBS OF THE HORSE Y

wv

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F y Y Y Uy Y/, Yy ‘\
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are De LLZZLS Ze fy \\ =,
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g aw AMIN WV
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| JT Muafar del mo
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10 TOPOGRAPHICAL ANATOMY OF

the surface of the latissimus dorsi should be performed with some
degree of care, and note must be taken of a thin tendinous band that
passes within the humerus to end at the lesser tubercle of this bone.

Cutaneous nerves from a variety of sources must also be noted.
Dorsal branches from the first few thoracic nerves appear in the inter-
scapular region, and sweep for a short distance over the scapular
muscles. In the region of the shoulder joint branches from the sixth
cervical nerve (n. supraclavicularis) lie on the surface of the brachio-
cephalic muscle. Curving round the caudal border of the triceps
muscle and spreading out over its surface, are nerves derived from
the caudal pectoral with which branches from the second and third
intercostal nerves are connected.

M. TrapEzius.—The trapezius! muscle forms a thin, irregularly tri-
angular sheet over the scapular region, and extending well into the
neck. ‘Two parts, a thoracic and a cervical, are to be distinguished.

The cervical trapezius consists of fibres running in a caudal and
ventral direction, and some difficulty is experienced in clearing its
surface of a thin, closely adherent fibrous investment with strands
running at right angles to the fibres of the muscle. The origin of the
cervical trapezius is from the ligamentum nucne from the level of the
epistropheus to the third thoracic vertebra, and its insertion is partly
into the spine of scapula and partly into the fascial aponeurosis that
“ covers the scapular muscles and is continued into the arm.

The thoracic trapezius has a much more definite outline. From an
origin extending from the fourth to about the ninth thoracic spinous
processes (supraspinal ligament) the fibres of the muscle pass in a
cranial and ventral direction, to be inserted into the spine of the
scapula and more particularly into its tubercle.

Dissection.--Cut through both parts of the trapezius muscle close to
their origin and turn them downwards. In doing so, seek for the dorsal
branch of the accessory nerve that travels down the neck to end in the
trapezius.

This dissection exposes the rhomboid muscles.

The surface of the latissimus dorsi should be cleaned. Considerable
care must be exercised when working over its broad, thin, and
aponeurotic tendon of origin.

M. RHOMBOIDEUS CERVICALIS.—The cervical rhomboid ? muscle has its
origin from the cordlike part of the ligamentum nuche from the level
of the epistropheus. The muscle is narrow and oblique in direction,
and its insertion is to the medial surface of the scapular cartilage, where
it is confused with the origin of the most cranial part of the ventral
serratus muscle.

M. RHOMBOIDEUS THORACALIS.—The thoracic rhomboid is not clearly

1 Trapezium [L.], from rpamé(rov (trapezion) [Gr.], a small table. From the

four-sided outline of the muscles of the two sides of the body taken together.

2 Rhombus [L.], popBos Diguzeo byl i. pio etdos (eidos) [Gr.], form.

THE LIMBS OF THE HORSE 11

\\ ae \ Sr 7
a Oh \, me oe/ --- -- M. pectoralis pro-
, = cian \\X \ \ iz fundus (pars
\\ \ \ i\ WW p i
\ \\ \e
| Ree \\ Nt i" =---- -M. supraspinatus
a
. hy ---—---M. deltoideus
y) \\. W
Y }
UY biceps brachii

Uf _ —— on
| Y

Pa . brachialis.
gy Z A
22222 .
ZZ LE 4
ZZ
‘ 1 ae Mina get \ |
| 1 \ :
! ' \ \
; \ H a’
oo we 4
{ ; ! / \
' f we we \ne
M. trice
M_ triceps brz
N. thoraralis lon

le).
V. thoracica externa.

Fie, 4.—Dissection of the Region of the Shoulder,

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12 TOPOGRAPHICAL ANATOMY OF

defined where it meets the cervical muscle of the same name. Thin,
and with parallel fibres, it arises from the spinous processes of the
third to seventh thoracic vertebre, and is inserted into the medial
surface of the scapular cartilage.

The nerve to the rhomboid muscle is derived from the sixth cervical,

Scapular cartilage.

M. teres major, — - — ---
M. triceps brachii
(caput longum).

AM. supraspinatus.
¥f- M. trapezius.

M. infraspinatus, ~ —~-

- ---Spine.

M. teres minor. - -— -

RQ

M. triceps brachii (caput longum).
~\- Coracoid process.

-/ M. bice achii.
M. teres minor. - 4 DBE rs: DEenE

/
Glenoid cavity.

Fic. 5.—Lateral Aspect of the Scapula and Scapular Cartilage, with Areas
of Muscular Attachment.

and will be found piercing the cervical part of the ventral serratus
muscle.

M. LATISSIMUS DoRSI.'—This muscle merits its name. An extensive,
thin, and aponeurotic tendon connects it with the spinous processes
of all the vertebree from the fourth thoracic to the last lumbar. Its
lumbar spinal connection is effected by the mergence of its aponeurosis
into the lumbodorsal fascia. The fleshy part of the muscle begins at
a curved line approximately on a level with the twelfth rib. At the

1 Latissimus [L.], superlatiy ot, l BS, pyoad, siete Dorsum [L.], the back.

THE LIMBS OF THE HORSE 13

present stage of the dissection the insertion (into the medial surface of
the humerus) cannot be examined, since the muscle disappears under the

M,. rhomboideus.

M. serratus ventralis.

-- M. teres major.

Coracoid process.

-— -M. triceps brachii (caput longum).

M. biceps brachii. ---—- - ‘ i %
~~M. capsularis.

M. ednieabrachiatlss Glenoid cavity.
Fic. 6.—Medial Aspect of the Scapula and Scapular Cartilage, with Areas of Muscular
Attachment.
border of the triceps. It should be noted that the most cranial fibres
of the latissimus dorsi playisvewthe/exndaliGdrsal angle of the scapula.

14 TOPOGRAPHICAL ANATOMY OF

N. accessorius.—The dorsal branch of the accessory or eleventh
cerebral nerve passes down the neck partly under cover of the brachio-
cephalic muscle. Nearing the scapula, its course becomes more
horizontal and lies between the trapezius muscle, which covers the
nerve, and the ventral serrate, prescapular part of the deep pectoral
and the supraspinous muscles, which are crossed in succession. The
accessory nerve comes to an end in the thoracic part of the trapezius.

M. BRACHIOCEPHALICUS.—By far the greater part of the brachio-
cephalic! muscle belongs to the neck; but the dissector of the limb
should examine its connection with the line continuing the crest of
the greater tubercle of the humerus beyond the deltoid tuberosity

M. biceps brachii.

.Glenoid cavity.

M. teres minor.~

Fic. 7.—Glenoid Cavity of the Scapula, with Areas of Muscular Attachment in its
Neighbourhood.

and the strong fascia on the lateral aspect of the arm. Just cranial
to the level of the shoulder joint the muscle is pierced by a branch of
the sixth cervical nerve that is distributed to the skin of this region.
M. PECTORALIS PROFUNDUS (PARS PRAESCAPULARIS).—If the brachio-
cephalic muscle be divided on a level with the shoulder joint and the

cut ends turned aside, the prescapular part of the deep pectoral will
be seen running along the edge of the scapula, to be attached to the
surface of the supraspinous muscle.

Dissection.—If the rhomboid and latissimus dorsi muscles be now
divided, the limb can be removed from the trunk. The dissector should
then direct his attention to the structures on the medial aspect of the
scapular region and the arm. The axillary vessels and their branches
are to be cleaned and the fibrous tissue adherent to those nerves that
supply the limb is to be removed, beginning at the most proximal part
7 ee nerve. Finally, such muscles as are visible must be defined and
cleaned.

LYMPH GLANDS OF THE ARM.—In clearing away the fibrous tissue
from the vessels and nerves that cross the distal part of the teres

1 Brachium [L.], Bpayéwv (brachion)(Gr.], the arm (above the elbow). Cephalicus
[L.], kepaAckos (cephalicos) [Gr.], pertaining to the head (xepaA7).
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THE LIMBS OF THE HORSE 15

major muscle, the small mass of axillary lymph glands (lymphoglandule
axillares) will be discovered. A second group of lymph glands, the
cubital (lymphoglandule cubitales), lie on the brachial vessels close
to the origin of the collateral ulnar artery, that is, a short distance
proximal to the elbow joint.

M. suBscAPULARIS.—The flat and triangular subscapular muscle
occupies the homonymous fossa of the scapula, from the whole of
which it takes origin. The fibres of the muscle, intermixed with
tendinous tissue, converge to a stout insertion, partly fleshy, partly
tendinous, into the tuberculum minus of the humerus. This insertion
may be regarded as functionally equivalent to the presence of a medial
collateral ligament of the shoulder joint. It is usual to find a small
synovial bursa interposed between the tendon of insertion and the
tubercle of the humerus.

M. TERES MAJoR.—An elongated, flattened, and almost entirely
fleshy muscle placed immediately caudal to the foregoing, the teres?
major takes origin from the angle separating the axillary and vertebral
borders of the scapula, and from the subscapular muscle. Its insertion
is in common with that of the latissimus dorsi to an imprint on the
crest of the lesser tubercle of the humerus about the junction of the
proximal and distal thirds of the bone.

It will be noted that the latissimus dorsi is at first lateral to the
teres major, but the tendon of the former muscle so curves round the
border of the latter as to be medial to it at their common insertion.

M. BICEPS BRACHII—The powerful biceps? muscle runs parallel to
and in front of the humerus. The strong tendon of origin begins on
the coracoid process of the scapula. From this point it crosses the
front of the shoulder joint and traverses the intertubercular groove
of the humerus. The tendon is closely moulded on the groove and
hence, when viewed from its deep aspect, presents a groove flanked by
a ridge on each side. As is customary where a tendon plays over
a bony surface, the intertubercular groove is clothed and rendered
smooth by a layer of fibrocartilage. Friction is further diminished
by the presence of a synovial bursa. A band of fascia, with which
some fibres of the humeral part of the deep pectoral muscle are
connected, crosses the tendon as it lies in the groove.

The elongated, fusiform belly of the biceps is rendered strong by
admixture of tendinous tissue, which divides into two portions in the
distal part of the muscle.

1 Teres [L.], rounded (long and round).
2 The name “biceps” has been translated from human anatomy, but in none of

the domestic mammals is thigtirecte sy aherdess HO provided with a double origin.

16 TOPOGRAPHICAL ANATOMY OF

The insertion of the biceps, partly concealed by the medial
collateral ligament of the elbow joint, with which some of its fibres
are blended, is into the tuberosity of the radius. It will be observed
that a stout, flattened tendinous band passes from the biceps to the
surface of the radial extensor of the carpus and the fascia of the
forearm..

M. CORACOBRACHIALIS.—The coracobrachial + muscle is comparatively
small. Its long narrow tendon of origin begins on the projection on
the medial surface of the coracoid process of the scapula, and appearing
between the supraspinous and subscapular muscles crosses the insertion
of the latter and gives place to a fusiform fleshy belly. A small
synovial bursa is interposed between the tendon of origin of the
coracobrachialis and the tendon of insertion of the subscapular
muscle.

The insertion of the coracobrachialis is into the medial surface of
the humerus both proximal and distal to the common insertion of the
latissimus dorsi and teres major.

M. TENSOR FASCIA ANTIBRACHIL—The flattened tensor of the anti-
brachial? fascia has an extensive and very thin membranous tendon of
origin attached to the axillary border of the scapula and intimately
connected with the origin of the long head of the triceps and the
tendon of insertion of the latissimus dorsi. The fleshy portion of the
tensor, placed medial to the triceps mass, is inserted into the posterior
border of the olecranon and the fascia of the forearm. In raising the
tensor from the triceps upon which it rests, the dissector should begin
at the posterior border of the muscle where it is thickest. This will
prevent accidental destruction of the thin tendon of origin.

Dissection.—Cut across the tensor of the antibrachial fascia about
the middle of its length and turn the cut ends aside in order to
expose the triceps muscles.

M. TRICEPS BRAcHIIL—The triangular gap between the scapula and
the humerus is occupied by the powerful triceps* muscle. As its name
indicates, three parts of the muscle are to be distinguished; but only
two of them—caput longum and caput mediale—can be dissected at
this stage. The third head must be left until the lateral aspect of the
arm is examined.

Caput longum.—The long head of the triceps is a thick, triangular

1 xdpag (corax) [Gr.], raven. The coracoid process is so called from its resem-
blance, in man, to the beak of a raven. Brachium (L.], Bpayiwv [Gr.], the arm.

? Objections have been raised to the use of the term anti-brachium.
tended, with reason, that the prefix should he ante.

3 Tres [L.], three. Caput [L.], head.

Digitized by Microsoft®

It is con-

THE LIMBS OF THE HORSE 17

M. rhomboideus thoracalis.

ny

SE:
a iy \S - - M. serratus ventralis.

NN
TN

|
Z = 2 \ |
-_ i

ri,

OWA
Caney

| it Fr iig (in ea
tet Ul praescapularis).
/ Dds E \ | ea 4 M. supraspinatus.
. ; / Ce e ) | My 77 M. infraspinatus.
vogue of Ly EN
ee wi NDA! |
A. circumflexa —- ~ —/- TH i Y, res o YL. | —- M. teres minor,
humeri posterior, fal | | |; 4 “LY fl ( \\W Y
, / Y,
y cae? ‘ a yy
ar ee ; EZ 4 _- — N. cutaneus brachii
| i fy lateralis.
Yf/ ---- M. brachio-
Y/ cephalicus.

Y

: } uh HN A
N. radialis, -— —-- =<

A. profunda brachii. — — — a Y G Sh bieepabiaant:
\ =" £
w7 AN
Ws NY — LA eC at extensor carpi radialis.
a Ve pase \\\|Il||| Za iali
Ray Wel a = WH ne ot M. brachialis,
“Ey i= A .
Z, a = a ) | i |
uae ee aN \) | | 3
oo ‘ |
M. triceps brachii~~ \ Nb 41) IE ----—---— A. collateralisradialis.
(caput laterale) Nz
4 Ne =
R cutan 1 fn. wl \ \\ \\ Jee M. extensor digitorum
\7 communis,
M. exten ‘pi ul: M. extensor carpi radial:

Fie, 8.—Deep Dissection of the Shoulder and Arm.

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18 TOPOGRAPHICAL ANATOMY OF

muscle springing from the axillary border and angle and the lateral
surface of the neck of the scapula, and ending in a strong, partly
tendinous insertion into the olecranon. A small synovial bursa lies
underneath the insertion.

Some of the fibres of origin of this muscle, it should be observed,
spring from the surface of the deltoid.

An aponeurosis, particularly noticeable over the distal third of the
muscle, covers the surface of the long head of the triceps.

Caput mediale—This is the smallest of the three heads of the
triceps. From a fleshy origin from the middle of the medial surface
of the humerus, immediately distal to the common insertion of the
latissimus dorsi and teres major, the fibres converge to a double
insertion. One of these is to the anterior and proximal projection on
the medial surface of the olecranon. The second is in line with the
first but farther back, i.e. about midway between the two projections
that occur on the medial aspect of the olecranon.

M. capPsuLARIS.—If search be made between the subscapular and
teres major muscles immediately behind the shoulder joint, the very
small, narrow, and slender capsular muscle will be found. As its name
indicates, it is applied to the capsule of the joint, and extends from
the scapula just beyond the edge of the glenoid cavity to the posterior
surface of the humerus, a short distance distal to the head.

N. SUPRASCAPULARIS.—The fairly large suprascapular nerve dis-
appears into the narrow interval between the subscapular and supra-
spinous muscles. After crossing the cranial border of the scapula,
branches are contributed to the supraspinous and infraspinous muscles.

A fibrous band crosses the nerve as it bends round the border of
the scapula.

NN. SUBSCAPULARES.—Two or three slender subscapular nerves end
in the subscapular muscle.

N. THORACODORSALIS.—As previously noted, the thoracodorsal
nerve is expended in the latissimus dorsi muscle.

N. AXILLARIS.—The axillary nerve soon leaves the present dissection
by sinking into a quadrilateral space bounded by the subscapular, teres
major, long head of the triceps, and brachial muscles. Crossing the
back of the shoulder joint, but separated from the joint capsule by the
capsular muscle to which a small branch is furnished, it supplies the
teres major, deltoid, teres minor, and brachiocephalic muscles, and ends
as the lateral cutaneous nerve of the arm (n. cutaneus brachii lateralis)
in the skin over the anterior part of the elbow and forearm.

N. MUSCULOCUTANEUS.—The musculocutaneous nerve leaves the

more cranial part of the brachial plexus. By a connection that it
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THE LIMBS OF THE HORSE 19

establishes with the median nerve, a loop is formed through which
the axillary artery passes. The musculocutaneous nerve pierces
the insertion of the coracobrachial muscle along with the anterior
circumflex artery, supplies the muscle in passing, and ends in the
biceps. It also furnishes a cranial pectoral nerve to the pectoral

Nerve to m. teres major.

N. subscapularis. -

N. suprascapularis, _
N, axillaris.

N. radialis.

M. supraspinatus.

A. axillaris, _

A. thoracoacromialis.
N. musculocutaneus.

M. subscapularis.

-N. pectoralis caudalis.
A. thoracodorsalis.

'F=- V. subscapularis.

Lymphoglandulee
axillaris.
. thoracica externa.

M. medianus, ._

M. pectoralis profundus
(pars humeralis). si
M. coracobrachialis.

A. brachialis.
M. biceps brachii.
= tensor ful anti-

Neg a

ww SN /--Ramus cutaneus volaris
NY :

Lymphoglandule -— ---- --\&
cubitales. \

of n. ulnaris.

A.mediana. - Ne

iY

fT] 7 M. flexor carpi ulnaris.

} 7M. flexor carpi radialis.
##- V. cephalica antibrachii.

N. medianus. -
N. cutaneus antibrachii lateralis. -
V. cephalica accessoria. -R3 i} 4

Fic. 9.—Dissection of the Medial Aspect ce Scapular Region and Arm,

muscles, and may contribute a branch that joins the cutaneous part
of the median nerve.

N. mepianus.—The median is:generally the largest nerve derived
from the brachial plexus, though the radial may be as large or possibly
larger. After its connection with the musculocutaneous, the median
passes down the arm along the anterior border of the axillary and
brachial arteries, and enters the forearm in company with the median

artery. Digitized by Microsoft®

20 TOPOGRAPHICAL ANATOMY OF

Only one branch leaves the median nerve while it is in the arm.
This arises about the middle of the arm and at once sinks between
the coracobrachial and biceps muscles. It then continues obliquely
between the brachialis and biceps, supplying branches to the former
muscle, crosses the flexor aspect of the elbow joint, and thus gains the

_7A. circumflexa scapule.

tS ARRAS LC

_-A. subscapularis.

~~ \| Ne _-A. thoracodorsalis.

: PX __- N. radialis.
A. thoracoacromialis._ ptt " ae Ye 7
ANG = Aeon ‘s
M. supraspinatus. - I a ot SAN \ eee A. circumflexa humeri
M. subscapularis. -}4L an oN posterior.
| AS *< a — M. teres major.
N. musculocutaneus. ---hhi +A

----M. triceps brachii
(caput longum).

M. coracobrachialis. . (WW --- A. profunda brachii.

N. medianus.. - \N

M. biceps brachii.- - &

M. brachialis.-

\Wi7 N. ulnaris.

- M. triceps brachii
(caput mediale).
A. collateralis ulnaris.

Va
Whips
‘Wa
7f--- -~ ~M. flexor carpi ulnaris.

--- --- M, flexor carpi radialis.

if} Weis
EY
Fic. 10.—Deep Dissection of the Medial Aspect of the Arm.

forearm, where it will be seen later as one of the cutaneous nerves of
the region (n. cutaneus antibrachii lateralis). Although, for the sake
of convenience and because of its obvious origin, this nerve is here
described as a branch of the median, there is reason for assuming that,
morphologically, it is part of the musculocutaneous nerve. The fibres
composing it apparently become separated from the other components
of the musculocutaneous during the temporary fusion of this nerve

ith the median. ;
wai tne menan Digitized by Microsoft® :

THE LIMBS OF THE HORSE 21

N. RADIALIS.—Nearly or quite as large as the median, the radial?
nerve leaves the more caudal part of the brachial plexus, accompanies
the ulnar nerve, and, about the middle of the arm, disappears between
the long and medial heads of the triceps. Before disappearing from
the present dissection, the nerve furnishes a branch to the tensor of
the antibrachial fascia; and it is generally possible to see the origin
of the nerves to the long and medial heads of the triceps.

N. ULNaRIs.—Smaller than the radial or the median, the ulnar?
nerve passes into the arm between the axillary vessels and the radial
nerve. About the middle of the arm it forsakes the vessels and runs
obliquely between the triceps and the tensor of the antibrachial fascia,
to enter the forearm between the olecranon and the medial epicondyle
of the humerus. About the middle of the arm it also gives off a
cutaneous branch (ramus cutaneus volaris), which crosses the surface
of the tensor fascize antibrachii to supply the skin on the flexor aspect
of the forearm.

A. AXILLARIS.—The commencement of the axillary artery at the
cranial border of the first rib and its course in the axilla have
already been examined. It is now found crossing the medial aspect
of the shoulder joint obliquely, passing over, in succession, the
insertion of the humeral part of the deep pectoral muscle, the
coracobrachial muscle, and the insertions of the subscapularis and
teres major. On a level with the distal border of the last-named
muscle, the axillary artery becomes the brachial. The portion of
the vessel at present under examination has the median nerve
along its anterior border, and the ulnar nerve running down the
opposite border.

The branches of the axillary are the omocervical trunk, and the
external thoracic, thoraco-acromial, subscapular, and anterior circumflex
humeral arteries. The first two have been examined in the axilla;
the rest belong to the limb proper. ~

A. THORACO-ACROMIALIS.—The thoraco-acromial® artery leaves the
axillary shortly before this vessel arrives at the leve’ of the shoulder
joint. Running in a dorsal direction, it supplies }vanches to the
prescapular and humeral parts of the deep pectoral muscle. Another
branch enters the cleft between the supraspinous and subscapular
muscles to which it furnishes twigs.

A. SUBSCAPULARIS. — The subscapular artery is by far the largest

1 Radius [L.], a staff or rod, a spoke of a wheel.
2 Ulna [L.], dA€vy (Glené) [Gr.], the elbow.
3 Thorax [L.]; Odpagé (thorax) [Gr.], the chest ; dxpov (acron) [Gr.], summit or

point ; Sos (omos) [Gr], He shoals sy, Microsoft® ;

22 TOPOGRAPHICAL ANATOMY OF

branch of the axillary. Arising opposite the cleft between the
subscapularis and teres major, it immediately disappears between
these muscles. In order that the course of the artery may be followed,
it is necessary to detach the greater part of the teres major from its
origin, When this has been done, the artery can be traced along
nearly the whole of the axillary border of the scapula. It ends in the

A. circumflexa scapul. .
i

A. axillaris... @
A. thoracoacromialis. -

A. subscapularis. ; y 7 .
P po Tere —A. circumflexa humeri posterior.

_- A. profunda brachii.
A. circumflexa humeri-- ‘
anterior. 4
A. brachialis.-----\-- Was | A. nutritia humeri.
\ ,

_A. collateralis ulnaris.

A. retis carpi volaris. - =
u A. metacarpea volaris

-----—~ lateralis.

-----— A. digitalis communis.
--.---~A. metacarpa volaris
medialis.

Fig. 11.—Diagram of the Arteries of the Thoracic Limb.

infraspinous muscle, which is reached by bending round the border
of the scapula.

The branches of the subscapular are as follows :—

1, A. thoracodorsalis—Arising close to the commencement of the
subscapular, the long thoracodorsal artery crosses the medial surface
of the teres major and ends in the latissimus dorsi and cutaneous
muscles. Small twigs are furnished to the axillary lymph glands.

2. A. circwmflexa humeri posterior. — The posterior circumflex
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THE LIMBS OF THE HORSE 23

humeral artery accompanies the axillary nerve round the back of
the shoulder joint. In the dissection of the lateral aspect of the
shoulder it will be found under the deltoid muscle.

3. A. cireumflexa scapule.—tThe circumflex artery of the scapula
leaves the subscapular a short distance beyond the point of origin
of the posterior circumflex. A branch is given to the subscapular

V. circumflexa scapule.

V. jugularis.

V. axillaris, .§

nae f _.V. subscapularis.
V. thoracoacromialis. -4 oo P

_- V. circumflexa humeri posterior.

V. cephalica brachii. -}
e=- V. thorocodorsalis.

\ —=—=-V. thoracica externa.

V. cireumflexa humeri —\

anterior. fe 2 Soe eae V. profunda brachii.

—---------- V. brachialis.

AN (ea -—-.V. collateralis ulnaris.
V. collateralis radialis....._ __% oN \ \

V. cephalica accessoria,- -_-~ __.___}
V. cephalica antibrachii.- - -- —~ - ---

w------ V. mediana.

Hh ----- V. metacarpea volaris lateralis.
i --- V. metacarpea volaris profunda.
H----.— V. digitalis communis.

Fic. 12.—Diagram of the Veins of the Thoracic Limb.

muscle, after which the artery pierces the origin of the long head
of the triceps and bends round the axillary border of the scapula
to enter the infraspinous fossa. Rami supply the infraspinous, teres
minor, and supraspinous muscles, and terminal twigs reach the skin
in the acromial region. The nutrient artery of the scapula is furnished
by the circumflex scapular.

4, A number of inconstant muscular branches (rami musculares)
are supplied to the subscapular, teres major, and triceps muscles.

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24 TOPOGRAPHICAL ANATOMY OF

A. CIRCUMFLEXA HUMERI ANTERIOR.—The anterior humeral circum-
flex artery leaves the axillary as this vessel lies upon the teres major.
Piercing the coracobrachial muscle, to which it supplies branches, the
artery is chiefly expended in the biceps. A feeble anastomosis with
twigs from the posterior circumflex may be demonstrated.

A. BRACHIALIS.—From its origin at the distal border of the teres
major, the brachial artery follows a course that causes it to cross the
line of the humerus very obliquely and approach the flexor aspect
of the elbow joint, where it ends in the median artery.

In its course the artery lies in a groove formed at first by the
coracobrachial muscle and the medial head of the triceps, and later by
the biceps and the humerus. The median nerve follows the anterior
border of the artery, while the brachial vein lies behind it. The medial
surface of the brachial artery is in contact in succession with the
humeral part of the deep pectoral and the sternocostal part of the
superficial pectoral.

The following are the collateral branches of the brachial artery :—

1. A. profunda brachit.— The deep artery of the arm arises
opposite the edge of the teres major, ¢.e. immediately the axillary
artery becomes the brachial. Several large branches are at once dis-
tributed to the triceps and the tensor of the antibrachial fascia; while
one branch accompanies the radial nerve between the long and medial
heads of the triceps, and will be examined at a later stage of the
dissection.

It is not rarely the case that the deep artery of the arm is double.

2. Ramus muscularis—A muscular branch, which may be double,
enters the distal part of the biceps.

3, A. collateralis ulnaris.—The collateral ulnar artery arises from the
brachial just as this vessel reaches the distal border of the medial head
of the triceps. Following the border of this muscle, under cover
of the tensor fasciz antibrachii, it passes into the forearm in company
with the ulnar nerve.

4. A, nutritia humert.— The nutrient artery of the humerus
springs either from the brachial close to its termination or from the
collateral ulnar near its commencement. It immediately enters the
nutrient foramen of the humerus.

5. A. collateralis radialis——The collateral radial artery leaves the
brachial at an acute angle a short distance proximal to the elbow joint.
It lies at first between the humerus and the biceps, and then between
the bone and the brachialis muscle, where it comes into relation with
the radial nerve. The two structures, with one or, possibly, two veins,
enter the forearm by crossing the flexor aspect of the elbow joint.

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THE LIMBS OF THE HORSE 25

Vv. BRACHIALIS ET AXILLARIS.—Generally speaking, the veins of
the region receive tributaries corresponding to the like-named arteries.
Some differences, however, may be noted. The brachial vein is fre-
quently double near the elbow, in which case the artery is flanked
by a vein on each side. In the same region the brachial receives
a strong communicating branch from the cephalic vein.

The external thoracic vein may join the brachial instead of the
axillary, and frequently it receives the thoracodorsal vein.

The external thoracic vein is not really a satellite of the artery
of the same name. Beginning superficially in the lateral wall of the
abdomen (flank), it pierces the cutaneous muscle, to reach the lateral
border of the deep pectoral muscle, along which it travels into the
axilla.

The main veins of the arm lie behind the corresponding arteries
until the region of the shoulder is reached. Here the axillary vein
crosses the medial face of the artery, so that, by the time the
vessels have arrived at the first rib, the vein is the more ventral
of the two.

Dissection.—Proceed now to the examination of the lateral aspect
of the shoulder and arm. Though not strictly necessary, it makes for
convenience if the remains of the trapezius muscle be removed. In
cleaning the surface of the scapular muscles, look for the terminal twigs
of the circumflex scapular artery a little proximal to the shoulder joint

‘ and in line with the spine of the scapula.

A branch (n. cutaneus brachii lateralis) of the axillary nerve appear-
ing from underneath the deltoid muscle, and running across the lateral
head of the triceps and down the front of the brachialis muscle into the
forearm, should also be secured.

M. sUPRASPINATUS. —The supraspinous! muscle fills the whole
of the supraspinous fossa of the scapula from which it takes most
of its origin. Some of its fibres, however, spring from the scapular
cartilage, and some arise from the common septum between the supra-
spinous and subscapular muscles. At the coracoid process the muscle
splits into two parts, which form an arch over the biceps tendon,
and are inserted into the anterior portion of the greater and lesser
tubercles of the humerus. On a superficial examination both inser-
tions appear to be wholly fleshy. Deeper investigation, however,
reveals a core of tendinous tissue. It should also be noted that
both parts of the insertion are closely connected with the joint-
capsule. Not infrequently a synovial bursa lies between the supra-
spinous muscle and the coracoid process of the scapula.

M. vELrowsrus.—The deltoid? muscle occupies the angle formed

1 Supra [L.], above. Spina, see footnote, p. 27. z
2 Deltoides [L.], triangular; AeAra [Gr.], the letter A, or delta; e?Sos (eidos

[Gr.], shape. Digitized by Microsoft®

26 TOPOGRAPHICAL ANATOMY OF

by the scapula and the humerus. It has a partly fleshy, partly
tendinous, origin from the. axillary border of the scapula close to the
caudal angle, and a broad, aponeurotic origin from the spine of the
scapula. The tendinous aponeurosis can be raised from the under-
lying infraspinous muscle in the more distal part only. Elsewhere

M. infraspinatus, M. supraspinatus.

M. triceps brachii-
(caput laterale).

M. brachialis..__

-—-M. deltoideus.

M. anconzus. ~—-

-—~-M. extensor digitorum
communis.

Mm. flexores digitorum. MW
sublimis et profundus,

‘
M. extensor carpi ulnaris.

Fic. 13.—Lateral Aspect of the Humerus, with Areas of Muscular Attachment,

the origin of the deltoid and the aponeurotic covering of the infra-
spinous are so intimately blended as to be one structure.

The insertion of the deltoid is into the deltoid tuberosity of
the humerus.

An imperfect division of the deltoid into two parallel portions
might lead to the assumption that in the horse, as in the dog and
the ruminants, the muscle consists of scapular and acromial parts.
There is, however, little justification for this assumption. It is more

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THE LIMBS OF THE HORSE 27

on to regard both portions as representing the pars scapularis
only.

___ Dissection—Cut across the deltoid within a short distance of its
insertion and turn it aside as far as possible without, however,
endeavouring to remove its tendinous origin from that part of the
infraspinous muscle to which it is closely adherent. This dissection
exposes the teres minor muscle, the origin of the lateral head of the

M. supraspinatus. M. pectoralis profundus.
‘ '

, M. supraspinatus.

i} M. subscapularis.

M. infraspinatus. - -—-

~-M. brachialis.

M. teres minor. - --+

M. deltoideus. -

|. Mm. teres major
et latissimus dorsi.

M. brachiocephalicus. ---—- -M. coracobrachialis.

M. extensor carpi radialis. _

SRS Mm, extensor digitorum
communis et extensor
carpi radialis,

Fie. 14.—Anterior Aspect of the Humerus, with Areas of Muscular Attachment.

triceps, and the axillary nerve as it appears, along with the posterior
circumflex vessels, from the narrow, triangular space bounded by the
long and lateral heads of the triceps and the teres minor.

M. INFRASPINATUS.—The infraspinous! muscle occupies the fossa
of the same name. Its origin is from the whole of the fossa, and
also from the aponeurotic origin of the teres minor muscle. As

1 Infra [L.], beneath. Spina [L.], a low wall dividing the circus lengthwise.
In man the muscle lies beneath the spine of the scapula.

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28 TOPOGRAPHICAL ANATOMY OF

the scapular spine fades away distally, the infra- and supra-spinous
muscles become intimately connected.

The muscle has a double insertion—(1) A strong, flattened tendon
plays over the smooth, convex area of the greater tubercle of the
humerus, to be attached to a distinct impression on the crista tuberculi

M. supraspinatus. M. subscapularis,
ri rd

M. pectoralis profundus. -

~---—M. brachialis,

Jeeeees Mm. teres major et
latissimus dorsi.

-_-—_—~—-M. triceps brachii
(caput mediale).
M. coracobrachialis. —-~— -

—---M. anconzus.

%
a a

M., flexor carpi radialis..4.------

i
M. flexor carpi ulnaris. Mm. flexores digitorum
sublimis et profundus,

Fic. 15,—Medial Aspect of the Humerus, with Areas of Muscular Attachment.

majoris. It should be observed that the tendon, as it crossés the bony
convexity, is retained in its place by a transverse band of fibres. If
this tendon be now severed about its middle, the second insertion can be
displayed. At the same time it must be observed that, as is commonly
the case where a tendon plays over a bony surface, the convexity is
made smooth by a veneer of fibro-cartilage, and friction is still further
reduced by the presence of a synovial bursa. (2) The second insertion
is mainly fleshy and is into the medial aspect of the convexity of the

greater tubercle, in close relation to the joint-capsule.
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THE LIMBS OF THE HORSE 29

Just as the insertion of the subscapular muscle may be regarded

8s functioning as a medial collateral ligament, so may the strong
idle insertion of the infraspinous muscle be regarded as render-
ing the presence of a lateral collateral ligament unnecessary.

M. TERES MINOR.—The teres minor muscle lies on the flexor side of

AML, supraspinatus. M. supraspinatus.

M. subscapularis, ~ -M. infraspinatus.

M. capsularis. --— --M. teres minor.

M. brachialis. -~— — -
- --M. triceps brachii
(caput laterale).

—~M. deltoideus.

M. triceps brachii — ——
(caput mediale).

SS oe eee M. anconzus.

M. flexor carpi radialis. - ¥

—-— M. extensor carpi ulnaris.

M. flexor carpi ulnaris. Mm. flexores digitorum sublimis et profundus.

Fie. 16.—Posterior Aspect of the Humerus, with Areas of Muscular Attachment.

the shoulder joint, between the triceps and the deltoid and infraspinous
muscles. To see the origin of the muscle it is necessary to remove a
part of the infraspinous.
The teres minor has a tendinous origin from the greater part of the
axillary border of the scapula and an oblique line in the distal part of
‘the infraspinous fossa, and a fleshy origin from a tubercle close to the
margin of the glenoid cavity. The insertion is to the proximal part of

the crest of the greater ia Pea Ay of t the hur erus.

30 TOPOGRAPHICAL ANATOMY OF
M. TRICEPS BRACHII.—Two heads—the long and the medial —
of the triceps have already been examined. It will be noticed that
the long head is included in both the medial and lateral aspects
of the arm.

Caput laterale—The four-sided lateral head arises from the posterior
face of the crest of the greater tubercle and the deltoid tuberosity of

M. supraspinatus.

——-M. supraspinatus.

AI, subscapularis, - —~- ‘A - M. infraspinatus.

~ p

Fic. 17,—Proximal End of the Humerus, with Areas of
Muscular Attachment.

the humerus. Some fibres are connected with the fascial investment of

the arm. The insertion is partly to the lateral face of the olecranon
and partly in common with the insertion of the long head.

Mm. flexores digitorum |
sublimis et profundus.

M. extensor carpi ulnaris.

Egil
At
M. flexor carpi ulnaris. - £.°5 oe s
M. flexor carpi radialis. - W/

AK yes

Fic. 18.—Distal End of the Humerus, with Areas of Muscular Attachment,

Dissection.—lf the lateral head of the triceps be now reflected, the
brachial and anconeus muscles will be exposed. Some little difficulty
may be experienced in separating the anconeus from the triceps.

The radial nerve, and the branch of the deep brachial artery that
accompanies it into the forearm, will also be displayed.
M. BRACHIALIS.—The brachial muscle is almost entirely fleshy, and
occupies the spiral groove (sulcus nervi radialis) that traverses the
lateral surface of the humerus. Its origin is from the posterior surface
of the humerus close to the head of the bone. It will be seen that the
muscle crosses the flexor aspect of the elbow joint and enters the fore-
arm, but its ultimate insertion into the radius and ulna cannot yet be

demonstrated.

M. ancon.£us.—The fleshy anconeus! muscle lies under cover of

1 @yxov (ancdn) [Gr.], the elbow.
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THE LIMBS OF THE HORSE 31

the triceps, with the lateral head of which it is very closely associated.
Its fibres arise from the distal part of the posterior surface of the
humerus, and its insertion is to the lateral surface of the olecranon.
The deeper fibres of the muscle are adherent to the capsule of the
elbow joint.

N, RADIALIS.—At a previous stage of the dissection, the radial nerve
was noted as passing down the proximal part of the arm in company
with the ulnar nerve which separated it from the axillary vein. About
the middle of the arm the radial nerve dipped between the medial and
long heads of the triceps muscle, giving off a branch to the tensor
fascie antibrachii as it did so. More of the course of the nerve is now
open to examination.

The nerve runs obliquely downwards and in a lateral direction along
with a branch of the deep humeral artery, in that spiral groove of the
humerus which is mainly occupied by the brachialis muscle. Laterally
the nerve is crossed by the lateral head of the triceps and the radial
extensor of the carpus. An oblique and somewhat spiral course brings
it to the flexor aspect of the elbow joint, where it will be encountered
at a later stage in the dissection.

From that part of the radial nerve which is now visible arises
a cutaneous branch (n. cutaneus antibrachii dorsalis) that either
passes through the lateral head of the triceps or emerges from beneath
the distal border of the muscle, and is distributed over the lateral and
anterior part of the forearm.

In his examination of the rest of the limb, the dissector should
constantly bear in mind that he is dealing with an animal in which
evolution has produced profound modifications. Inasmuch as the digits
have been reduced in number to one only, the horse is as far removed
as he conceivably can be from the typical pentadactyl mammal. In
association with the disappearance of all the digits except one, the
metacarpal bones have been modified. The first and fifth metacarpals
have disappeared entirely. The second and fourth are represented by
comparatively slender and tapering rods, which fail to stretch the full
length of the metacarpal region. At the distal end of each rudimen-
tary bone it seems probable that sometimes, at least, there may be
imperfect representatives of phalanges; but these are very variable
in size, and always firmly blended with the metacarpal bone to which
they belong. The third metacarpal bone has been transformed in
the opposite direction. It has increased in length and strength, and,
like the phalanges it carries, has attained a considerable volume.

As these bony changes any pking place. and as the manus as

32 TOPOGRAPHICAL ANATOMY OF

a whole was increasing in length, its relation to the ground became
gradually altered and more and more restricted. Not only has the
single remaining digit developed in such a way as to be now capable
of sustaining the whole weight of the body; it does so by contact
with the ground by its extreme end only. That is, the modern horse
is no longer digitigrade: he is unguligrade.

The bones of the forearm have also undergone a striking change.
While the radius has increased in size and strength, the ulna has been
reduced to a proximal extremity and a tapering shaft that does not
reach much beyond the middle of the radius. The disappearance of

A. B. Cc, Dz. E.

Carpus. ‘

Carpus.’,

Fic. 19.—Evolution from Pentadactyl to Monodactyl Condition in the Manus of the Horse.
The lower part of the figure shows the human hand for comparison.

A, = Pentadactyl, hypothetical ancestral stage. B. = Tetradactyl, Protohippus stage.
C. = Tetradactyl-tridactyl, Epihippus stage (three digits touching the ground, one
slightly raised). D. = Tridactyl, Mesohippus stage. HE. = Monodactyl, Equus stage ;
modern horse. (After H. F. Osborn.)

part of the shaft has caused the detachment of the distal end of the
ulna, which has fused with the distal end of the radius. These modifi-
cations in the bones of the forearm have been accompanied by their
intimate bony union with each other, and the consequent loss of any
possibility of movement between them. The limb, therefore, has been
fixed permanently in the position of pronation.

The above. alterations in the bony skeleton have, naturally, been
accompanied by great modification in the muscular apparatus. Some
muscles, for example the supinators, have lost their function and have
disappeared. Some, of which the abductor of the pollex is an illustra-
tion, have been compelled to change their attachments. Other muscles
have assumed a different structure and a different function, as is
exemplified in a remarkable manner by the interosseous muscle of
the metacarpus. Naturally, also, the blood-vessels and nerves of the
manus have been simplified. In short, it must always be remembered

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THE LIMBS OF THE HORSE 33

that in the dissection of the limbs of the horse one is dealing with
an extreme departure from the typical mammalian architecture.

Before proceeding to remove the skin, the dissector should examine
the surface of the forearm. In the anterior, lateral, and posterior
regions the bones are buried under muscular masses, which present
considerable resistance to palpation owing to the stoutness of their
fascial investment. Of bony prominences, the most obvious are those
produced by the olecranon of the ulna and the projection at the
posterior and lateral part of the carpus, due to the accessory carpal
(pisiform) bone. The medial border of the radius can be followed
throughout the whole of its length. Of the lateral border, however,
only the distal portion can be felt through the skin. The position of
the rest of the border is indicated by a shallow groove, which becomes
deeper towards the carpus, where it is complicated by a ridge formed
by the edge of the extensor digiti quinti muscle.

The outstanding rounded mass in front of the forearm is formed
by the fleshy portion of the radial extensor of the carpus and the
common extensor of the digits.!

The resisting muscular mass at the back of the forearm is formed
by flexors and one extensor.

A flattened, oval, horny callosity, popularly known as the “ chestnut,”
occurs on the skin in the distal third of the medial face of the fore-
arm. The prominence and size of the callosity is subject to much
variation, and is related to the “fineness” of the skin over the body
generally. In the average animal its greatest (vertical) diameter
is about 50 mm. The exact location of the callosity is also variable;
and, while one can say that it lies over the radial flexor of the carpus,
it is impossible to give any useful indication respecting its distance
from the radiocarpal joint. A similar callosity occurs in the pelvic
limb in connection with the skin of the medial surface of the tarsus.

Conflicting views are held respecting the homology of these callosi-
ties. Authorities have regarded them variously as representing the
rudiment of a digit, modified skin glands such as are present in the
carpal region of certain mammals, degenerate carpal sense-organs, and
even as altered foot-pads. It is safest to conclude that the question
is still open.

Dissection.—The skin must now be removed from the entire forearm
and carpus, and from the proximal part of the metacarpus. In doing

1 Though the horse possesses but one functional digit, the plural is used here
and throughout in order that it may be clear that the muscle (in the main)

corresponds to the commar SHSBEPD pF Ashes Banynals. .

o4 TOPOGRAPHICAL ANATOMY OF

this the cutaneous nerves and the superficial veins must be preserved.
The nerves are branches of the ulnar, radial, axillary, and median, and,
with one exception, their origins from the parent nerves have already
been observed.

(1) The volar cutaneous branch (ramus cutaneus volaris) of the ulnar
nerve spreads out over the posterior border of the forearm. (2) The
dorsal cutaneous nerve (n. cutaneus antibrachii dorsalis) is that branch
of the radial which becomes superficial at the distal border of the lateral
head of the triceps, and is distributed over the lateral aspect of the
forearm. (3) The lateral cutaneous nerve (a. cutaneus brachii lateralis)
is derived from the axillary, appears from beneath the deltoid, and
divides into two branches for the skin of the lateral and anterior part
of the forearm. (4) The lateral cutaneous nerve of the forearm (n.
cutaneus antibrachii lateralis) left the median about the middle of the
arm, and is now seen to be distributed over the anterior and medial
aspects of the forearm, carpus, and metacarpus. It divides into two
main branches, which follow the cephalic and accessory cephalic
veins. (5) The only cutaneous nerve of the forearm that does not
proceed from the arm is the superyicial branch (ramus superficialis) of the
ulnar. This becomes subcutaneous immediately proximal to the acces-
sory carpal (pisiform) bone. Some of its filaments are distributed over
the lateral aspect of the carpus, but the greater part of the nerve is
continued into the metacarpal region.

The superficial veins of the forearm are the cephalic and accessory
cephalic.

V. CEPHALICA ANTIBRACHII—The cephalic vein of the forearm is the
direct continuation of the median volar metacarpal vein. Lying at first
in the groove between the radial flexor of the carpus and the radius, it
crosses the medial aspect of the forearm very obliquely and becomes
continuous with the cephalic vein of the arm. This latter, ascending
the groove formed by the brachiocephalic and superficial pectoral
muscles, enters the triangular space at the root of the neck and ends
by uniting with the jugular. A considerable communicating branch
connects the cephalic vein of the forearm with the brachial about the
insertion of the biceps.

V. CEPHALICA ACCESSORIA.—The accessory cephalic vein begins in a
network of vessels on the dorsal aspect of the carpus and the distal
part of the radius and runs up the forearm, following the median border
of the radial extensor of the carpus, to join the cephalic vein close to
the elbow.

Dissection.—The loose and scanty superficial fascia into which the

superficial pectoral muscle is inserted, must be removed, in order that a
clear view of the dense and definite deep fascia may be obtained.

Fascia OF THE ForEARM.—The glistening antibrachial fascia ! (fascia
antibrachii) forms a complete investment to the muscles of the forearm
and is firmly connected with those parts of the radius and ulna that
are not covered with muscles. In the neighbourhood of the carpus

1 Fascia [L.], a band, a surgical bandage, swathe, girth.
a ba panead by Microsone “

THE LIMBS OF THE HORSE 35

there is no difficulty in showing that it blends with the ligaments and
the periosteum of the bone.

The tensor fascize antibrachii is mainly inserted into the fascia, with
which also certain fibres of the brachiocephalic and biceps muscles are
connected.

A definite compartment for the extensor digiti quinti is formed by
the fascia sinking in between this muscle and its immediate neighbours
to form intermuscular septa. Similar septa will be found elsewhere, as,
for example, between the radial extensor of the carpus and the common
extensor of the digits, and between the radial and ulnar flexors of the
carpus. Furthermore, the deep fascia is strengthened by transverse
fibres to form the dorsal carpal ligament (ligamentum carpi dorsale)
that retains the extensor tendons in the grooves at the distal end
of the radius.

But the most conspicuous thickening of the fascia occurs over the
volar aspect of the carpus where the strong transverse carpal ligament
(ligamentum carpi transversum) forms a stout bridge from the accessory
carpal (pisiform) bone to the medial collateral ligament and the proximal
end of the second metacarpal bone. The transverse ligament con-
stitutes the volar boundary of a short canal in which are contained the
flexor tendons with their synovial sheaths, the common digital artery,
and the medial volar nerve.

Dissection.—Remove the deep fascia over the extensor muscles and
proceed with their examination.

The extensor muscles in front and on the lateral aspect of the fore-
arm are arranged in two layers, superficial and deep. The superficial
layer contains the extensor carpi radialis, extensor digitorum communis,
extensor digiti quinti, and extensor carpi ulnaris—in this order from
the radial to the ulnar border of the limb. The deep layer in the horse
contains one muscle only, namely, the m. abductor pollicis longus.

M. EXTENSOR CARPI RADIALIS.—In man and in the dog the radial
extensor of the carpus! is divisible into two portions—long and short;
but in the horse no such division is possible. A powerful muscle with
a prominent and distally tapering belly, the radial extensor takes its
main origin from the lateral epicondyle of the humerus. In addition,
part of its tendinous origin is from the coronoid fossa in common with
the common extensor of the digits. It will be observed that the muscle
at its origin has some of its fibres disposed in a curved manner as
a consequence of their attachment to a strong fascia overlying the
brachialis muscle. Note also the strong tendinous slip (lacertus”

1 Carpus [L.], kapmés (carpos) [Gr.], the wrist.
2 Lacertus [L.], thergumsfeomyphashoul dente the elbow ; a lizard.

TOPOGRAPHICAL ANATOMY OF

'
'

1
sand
a
oO
=
=
2
n

A!
a
3
a
ac}
si
a

ond
S)
=
s
a
a
ay
3
5
wey
3
a
x
Do
LS

“NM. brachialis.

Lig. collaterale laterale. -4

nsor digitorum communis.

~----A. collateralis radialis.

M. extensorjcarpi ulnaris

--- M. extensor digitorum communis.

---- Muscle of Phillips.

= SSS
Ss

NY, EE glo
Y ye 5 z =
GO = Ye ———— : =
= My ——————— =) =
* HAC F ‘4
\ a ee 5 et
BA : Se A ae
\ \, 4 Z Beret SS ASR ® =
S = i =

M. extensor digiti quinti. --___

M. flexor digitorum profundus, ____

~--—.. M. abductor pollicis.

A. interossea dorsalis. _____

Rete carpi dorsalis,

f/
5 see
th

Superficial branch oft. ulmaris. ______._ ___ | M ae ob

M. flexor digitorum sublimis.

M. flexor digitorum profundus. —

Dissection of the Lateral Aspect of the Forearm and Carpal Region.

Fie. 20.—

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THE LIMBS OF THE HORSE 37

fibrosus) that leaves the biceps near its insertion and merges into the
surface investment of the radial extensor. In the distal third of the
forearm the tapering fleshy part of the muscle gives place to a strong,
flattened tendon that, traversing a groove at the distal end of the
radius and crossing the dorsal aspect of the carpus, is inserted into the
muscular imprint on the dorsal (anterior) medial part of the base of the
third metacarpal bone. The tendon is bound down in the grocve on
the radius by the dorsal carpal ligament, and here, as well as over the
carpus, is surrounded by a synovial sheath.

M. EXTENSOR DIGITORUM COMMUNIS.—Smaller than the preceding,
and lateral to it in position, the common extensor of the digits arises
from the anterior and most distal part of the lateral epicondyle of the
humerus, the coronoid fossa (in common with m. extensor carpi radialis),
the lateral collateral ligament of the elbow joint, the lateral aspect of
the proximal part of the radius, and the adjacent part of the ulna.
Some fibres also arise from the intermuscular septum between this
muscle and the radial extensor of the carpus.

Commonly, the most lateral part of the muscle can be isolated as the
muscle of Phillips, and occasionally another and smaller bundle of fibres,
medial to the preceding, may be separated from the main muscle—the
muscle of Thiernesse. If the last-named is separable, it is provided with
a thin tendon which soon joins the main tendon of the muscle. The
tendon of the muscle of Phillips accompanies the main tendon into the
metacarpus and there joins that of the extensor digiti quinti.

The main tendon of the common extensor leaves the tapering distal
part of the muscle, plays down a groove at the distal end of the radius,
crosses the extensor aspect of the carpus and enters the metacarpus.
At a later stage of the dissection it will be followed to the extensor
process of the third phalanx.

Like the tendon of the radial extensor, that of the common digital
extensor is secured in a groove on the radius by the dorsal carpal
ligament, and is provided with a synovial sheath here and over the
carpus. Since this arrangement is common to the extensor tendons of
the region, the tendon sheath should be slit open and an examination
made of the mode of disposition of its synovial lining. The sheath may
be regarded as a closed bag closely applied to the surface of the tendon
as well as to the wall of the fibro-osseous canal in which the tendon lies.
The layer upon the tendon is connected with that lining the canal by a
thin membrane known as the mesotenon.

To establish the strict homology of the three parts of the horse’s
common extensor is not without difficulty. There are those who see in

the muscle of Phillips Pagiaseerayenhi of thatypart of the dog’s common

38 TOPOGRAPHICAL ANATOMY OF

extensor which provides tendons for the fourth and fifth digits. There
can be little question that the main tendon in the horse is the homo-
logue of that tendon of the dog’s common extensor which ends in the
third digit. The greatest difficulty arises with the muscle of Thiernesse
—assuming that it is really something apart from the main mass of the
muscle. Its suggested homology with the m. extensor indicis proprius
of man gives ground for debate.

M. EXTENSOR DIGITI QUINTI.—Though here named the extensor of
the fifth digit, it is conceivable that this muscle may represent a
combination of the extensors of the third, fourth, and fifth digits of the
dog, and, to avoid difficulties of homology, it is frequently called the
lateral extensor of the digit. The muscle is narrow and semipenniform,
and is enclosed in its own compartment of antibrachial fascia. Its
position is along the lateral aspect of the forearm, insinuated between
the common extensor of the digits and the ulnar extensor of the carpus.

The origin of the muscle is from the lateral collateral ligament, the
back of the projection on the head of the radius, and a narrow area of
both bones of the forearm bounding the lateral line of their union. In
the distal part of the forearm the muscle gives place to a tendon that
traverses a groove on the lateral part of the distal end of the radius,
then travels down the corresponding aspect of the carpus partly
embedded in ligament, and enters the metacarpus, where it will be
examined subsequently. Like the preceding extensors, its tendon is
surrounded by a synovial sheath.

M. EXTENSOR CARPI ULNARIS.—Though morphologically an extensor
and in receipt of a nerve supply (radial) like that of the other extensors,
this muscle in the horse is doubtless physiologically a flexor. Unlike
its fellow-extensors, it is placed behind the lateral border of the radius.

The origin of the muscle is from the distal part of the lateral
epicondyle of the humerus. Its insertion is double. A strong tendon
connects it with the proximal edge of the accessory carpal (pisiform)
bone; while a narrow, rounded tendon runs somewhat obliquely along a
groove on the lateral face of the accessory bone and across the lateral
border of the carpus (embedded in ligament) to reach the base of the
fourth metacarpal bone. The second tendon is provided with a synovial
sheath.

M. ABDUCTOR POLLICIS LONGUS.!—This thin, triangular muscle arises
from the lateral border and adjacent area of the dorsal (anterior)
surface of the middle third of the radius. At first the muscle is
beneath the common extensor of the digits, but its narrow tendon

1 This muscle, in all probability, represents the short extensor as well as the long

abductor of the pollex. Pollex [L.], the thumb.
, Digi bed by Microsoft®

THE LIMBS OF THE HORSE 39

crosses that of the radial extensor of the carpus to reach the base of the
second metacarpal bone to which it is inserted. The insertion affords
a good example of the shifting of a muscular attachment rendered
necessary by modification of the skeleton. In the dog the insertion
is into the first metacarpal bone. In consequence of the disappear-
ance of this bone in the horse, the insertion has been transferred to
the nearest available bony point.

Dissection.—In order to expose the nerves and blood-vessels of the
front of the forearm it is necessary to reflect the radial and ulnar
extensors of the carpus. Cut across each muscle about the middle of its
fleshy belly, bearing in mind that the collateral radial artery is closely
applied to the deep surface of the radial extensor.

It may be necessary to reflect the biceps also, but it is better to
avoid doing this if possible.

N. RADIALIS.—In the dissection of the arm the radial nerve was
observed to follow the brachial muscle round the humerus, accompanied
by a branch of the deep artery of the arm. The continuation of the
nerve will now be found in front of the elbow joint between the
brachialis and the radial extensor of the carpus. Branches to the
following muscles should be demonstrated: brachialis, extensor carpi
radialis, extensor digitorum communis, extensor digiti quinti, and
extensor carpi ulnaris. A thin branch continues down the forearm
between the radius and the common extensor of the digits to end in
the m. abductor pollicis longus.

A. PROFUNDA BRACHII.—The terminal division of the deep artery of
the arm was disclosed by reflection of the lateral head of the triceps.
All that now remains to be noted is that a twig from the artery enters
the radial extensor of the carpus, while another passes underneath
the ulnar extensor to join the recurrent interosseous artery. An
anastomosis is also effected with the collateral radial artery.

A. COLLATERALIS RADIALIS (DISTALIS)—Immediately on its origin
from the brachial the collateral radial artery disappears between the
humerus and the biceps. The present dissection shows that the artery
next lies between the brachialis muscle and the humerus, and then
crosses the flexor aspect of the elbow joint, between the brachialis and
radial extensor, where it comes into contact with the radial nerve.
Branches from the artery supply the radial extensor, the common
extensor, and the long abductor of the pollex; and an anastomosis 1s
established with the dorsal interosseous artery. The small terminal
branch of the vessel joins the dorsal rete of the carpus.

A, INTEROSSEA DORSALIS.—The dorsal interosseous artery arises from
the common interosseous at the back of the forearm and enters the

ion by traversing the opening between the radius and the
extensor region by tan fitized by Microsor®

40 TOPOGRAPHICAL ANATOMY OF

ulna. Thereupon it runs in a distal direction following the extensor
digiti quinti closely, and ends near the carpus in the rete carpi dorsale.
It furnishes branches to the adjacent muscles, and gives origin to two
named arteries. (1) A. nutritia radii (the nutrient artery of the
radius) arises as the interosseous artery passes between the two bones
of the forearm and immediately disappears into the radius. (2) A.
interossea recurrens (recurrent interosseous artery) is very small and
sometimes difficult to demonstrate. It has its origin close to the gap
between the radius and the ulna, runs upwards on the lateral surface of
the ulna, and anastomoses with branches of the deep artery of the arm
and the collateral ulnar artery.

RETE CARPI DORSALE.—The dorsal rete! of the carpus consists of a
network of small arteries lying over the distal end of the radius and
the dorsal surface of the carpus. It is formed by branches from the
collateral radial and dorsal interosseous arteries, and from it arise
the two dorsal metacarpal arteries (a. metacarpea dorsalis medialis:
a, metacarpea dorsalis lateralis) that follow the grooves between the
metacarpal bones and anastomose with the volar metacarpal arteries.

Before leaving this region the dissector should take the opportunity
to examine the insertion of the biceps and brachialis muscles. The
strong tendon of the biceps is attached to the tuberosity of the radius,
but a slender continuation can be followed under the medial collateral
ligament as far as the edge of the ulna.

The brachial muscle is inserted mainly to the border of the radius
at a point just distal to the tuberosity. Some tendinous fibres pass
underneath the medial collateral ligament and blend with the trans-
verse ligament that joins the ulna to the radius.

Dissection.—The dissector must now turn his attention to the struc-
tures lying behind the radius, and, of these, the muscles should be
examined first. So far as position is concerned, the extensor carpi
ulnaris could legitimately be included in the group of muscles which now

fall to be examined ; but, for morphological reasons, and because it is
supplied by the radial nerve, this muscle has already been dissected.

The muscles lying behind the radius may be considered as disposed
in three strata: (1) The most superficial, enumerated from the radial
to the ulnar border of the limb, are: Mm. flexor carpi radialis, flexor
carpi ulnaris, flexor digitorum profundus (caput ulnare), extensor carpi
ulnaris. (2) The second layer consists of mm. flexor digitorum sub-
limis, flexor digitorum profundus (caput humerale). (3) The third
layer is of limited extent and formed solely by the radial head of the
deep flexor of the digits. :

1 Rete (L.], a net.

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THE LIMBS OF THE HORSE 41

M. FLEXOR CARPI RADIALIS.—The radial flexor of the carpus runs
parallel with the medial border of the radius. Its origin is from the
medial epicondyle of the humerus close to the articular margin and
immediately behind the point of attachment of the medial collateral
ligament. In the distal third of the forearm a rounded tendon replaces
the elongated fusiform fleshy belly of the muscle. The tendon, enclosed
in a synovial sheath, traverses a canal in the ligament at the medial
border of the carpus and is inserted to the base of the second meta-
carpal bone.

M. FLEXOR CARP] ULNARIS.—The ulnar flexor of the carpus possesses
two heads: (1) The humeral head (caput humerale) is strong and
arises from the medial epicondyle of the humerus behind the origin
of the radial flexor with which it is intimately connected. (2) The
ulnar head (caput ulnare) is weak, flattened, and narrow, and springs
from the medial surface of the olecranon of the ulna. The two heads
unite in the proximal third of the forearm.

The strong tendinous insertion of the muscle is to the accessory
carpal (pisiform) bone.

Dissection.—In order to obtain a satisfactory view of the flexors of
the digits, it is necessary to reflect the ulnar flexor of the carpus.

M. FLEXOR DIGITORUM SUBLIMIS.—The superficial flexor is a strong,
largely tendinous muscle of irregularly triangular outline in section.
Its origin is from the medial epicondyle of the humerus in common
with the deep flexor. Near the carpus a powerful tendon begins, and,
passing down the groove-like volar (posterior) surface of the carpus
under cover of the transverse ligament, is continued into the meta-
carpus. The further course of the tendon will be followed later.

From an impression on the volar (posterior) surface of the radius,
at about the junction of the middle and distal thirds and close to the
medial border of the bone, a strong tendinous band (caput tendineum)
arises and joins the tendon of the superficial flexor about the level of
the radiocarpal articulation.

M. FLEXOR DIGITORUM PROFUNDUS.—The deep flexor is by far the
largest and most powerful muscle in the region now being examined.
Three heads can readily be distinguished :

1. Caput ulnare—The ulnar head belongs to the most superficial
layer of muscles behind the radius, where it will be found along the
posterior border of the ulnar extensor of the carpus. Arising from the
medial surface and posterior border of the olecranon, the fleshy portion
of the ulnar head about the middle of the radius gives place to a

narrow, rounded tendomyhichypasspsdowartbe forearm under the edge

42 TOPOGRAPHICAL ANATOMY OF

V. brachialis.- — \Q~---—------ X \ §. A M. triceps prachii.
\: -\ WYRE iN SS ht _N. ulnaris.
i

\ d
WN WI _A. and V. collateralis

M. biceps brachii. — — - - -\ +
ulnaris.

V. cephalica. _

M. flexor carpi ulnaris (caput

a ra aa iN ys i Wf Mi HM \ TT Mf i. ML oo carpi radialis.
SG a antibrachii -_—----.- a f Ye | Uy _ Ramus cutaneus volaris of
ateralis. ail YA

nf n. ulnaris.

Ligamentum collaterale -—- - -
mediale

V. mediana,.——-------

A. mediana.-_---—--— __M. flexor carpi ulnaris.
V. cephalica accessoria. _--__.--

M. extensor carpi radialis.

__N. ulnaris.

V. cephalica antibrachii.

. A. digitalis communis.

N. volaris medialis.
A. metacarpea dorsalis

medialis. _ Tendon of m. flexor digitorum sublimis.

A. metacarpea volaris _

medialis. Communicating branch to n. volaris lateralis.

V. digitalis communis.

Fig, 21.—Diseection of the Medial Aspect of the Forearm and Carpal Region.

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THE LIMBS OF THE HORSE 43

of the extensor carpi ulnaris to join the main tendon of the deep flexor
close to the carpus.

2. Caput hwmerale—The massive humeral head can be divided

M. triceps brachii (capites
longum et Jaterale). M. anconeus.

M. tensor
fascie

M. biceps brachii
antibrachii.

M. extensor digiti quinti. .\--___

M. extensor digitorum — —
communis.

M. extensor digiti quinti.— -

M. extensor digitorum — -
comin) 1nis,

cyt Cave! obhg ows =
M. abduetor-pollicis. —---+-

Fre, 22.—Lateral Aspect of the Radius and Ulna, with Areas of Muscular Attachment.

into three parts, one of which, in the proximal part of the forearm,
comes to the surface between the ulnar head and the superficial flexor
of the digits. This head has its origin from the medial epicondyle of

the humerus in common with, ft pF the superficial flexor. Near the

44 TOPOGRAPHICAL ANATOMY OF

carpus the fleshy belly is continued distalwards by a very dense,
flattened tendon.

M. anconeus. ---—- - M. flexor digitorum profundus.

M. biceps brachii.

M. extensor digitorum
communis.

4-- M. brachialis.

Fic. 23.—Anterior Aspect of the Proximal Part-of the{Radius and Ulna, with
Areas of Muscular Attachment.

M. triceps brachii (caput mediale),
-M. triceps brachii (capites

longum et laterale).
M., flexor digitorum profundus. ~ ~

f}

4M. flexor carpi ulnaris.

M. biceps brachii.-

M. brachialis.— -

Fic. 24.—Medial Aspect of the Proximal Part of the Radius and|Ulna, with Areas
of Muscular Attachment.
3. Caput radiale—tThe radial head of the deep flexor constitutes

the only member of the deepest layer of the flexor group. It is feeble
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THE LIMBS OF THE HORSE 45

and flattened, and sometimes can scarcely be said to exist. Its origin
is from the volar (posterior) surface of the radius immediately distal

{i

f M, triceps brachii (capites longum
M. triceps brachii ZX ! ie (cap 8

et laterale).

(caput mediale).
\
M. tensor fasciz antibrachii,-—-4 —
M. flexor digitorum profundus. — — CWS

M, extensor digiti{quinti.

M. brachialis,

M. extensor digitorum
communis.

M. flexor digitorum — -4—-—
protundits: |... M. extensor digiti quinti.

M. abductor pollicis.

M. flexor digitorum — 4
sublimis.

Fic. 25.—Posterior Aspect of the Radius and Ulna, with Areas of
Muscular Attachment.

to the middle of the bone. The tendon of the radial head joins the
main tendon in the neighbourhood of the carpus.

The very powerful and dense common tendon of the deep flexor
traverses the canal Algitiheovolatiiespesti@t the carpus and will be

46 TOPOGRAPHICAL ANATOMY OF

followed later down the rest of the limb to its ultimate insertion into
the flexor area of the third phalanx.

Accessory carpal bone (pisiform).

M. extensor carpi ulnaris. —--\|- Radius.

M. flexor carpi
ulnaris.

Intermediate carpal bone
(lunar).

Ulnar carpal bone ie

(cuneiform) . ___.. _ Third carpal bone
(magnum).

Fourth carpal bone - ~—-

(unciform).

~ — -M. extensor carpi radialis.
M. extensor carpi ulnaris. _.—

Radius.

Intermediate carpal bone

(lunar). = Raat carpal bone
Ulnar carpal bone- (scaphoid).
(cuneiform).

_ Second carpal bone

Fourth carpal bone. — (trapezoid).
(unciform). .. Third carpal bone
(magnum).

_ . Second metacarpal bone.
M,. extensor carpi ulnaris. —-

M. extensor carpi,radialis.

Fourth metacarpal bone. ---—- Third metacarpal bone.

Fic. 27.—Dorsal (Auterior) Aspect of the Carpus, etc., with Areas of Muscular Attachment.

The tendons of the superficial and deep flexor muscles are enclosed

in a common synovial sheath (vagina carpe) that extends upwards
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THE LIMBS OF THE HORSE 47

for some distance proximal to the radiocarpal joint and downwards
to near the middle of the metacarpus.

Poesecud Radius.
accessory carpal bone (pisiform).

M., extensor carpi wlnaris.

Radial carpal bone___
(scaphoid).

f
M., flexor carpi ulnaris.

Third carpal bone __ _. Second carpal bone (trapezoid).

(magnum).

M. extensor carpi
vadialis.

ext

‘
Second metacarpal bone.

Third metacarpal bone. ___

_ Radius.

Accessory carpal bone
_--. (pisiform).
..-- M. flexor carpi ulnaris.

Ulnar carpal bone

, (cuneiform).

Intermediate carpal bone
(lunar).

Radial carpal bone.
(scaphoid).

__ Third carpal bone

Second carpal bone _ (magnum).

(trapezoid).
First carpal bone. _. Fourth carpal bone
(trapezium). (unciform).

M. abductor pollicis longus.-

M., flexor carpi radialis. __

Fic. 29.—Volar (Posterior) Aspect of the Carpus, etc., with Areas of Muscular Attac} at

N. ULNARIS.—In the dissection of the arm the ulnar nerve was
i dial epicondyle of the
followed as far as the-jat erval ata veen theme ial epicondy

48 TOPOGRAPHICAL ANATOMY OF

humerus and the olecranon of the ulna, where it lies on the origin
of the superficial flexor of the digits and under cover of the tensor of
the antibrachial fascia. In the proximal half of the forearm the nerve
lies medial to the ulnar head of the deep flexor which it follows very

Fic. 30.—Key-outline of the Thoracic Limb to Indicate the Level of the Transverse
Sections Illustrated in Subsequent Figures.

closely. Beyond the middle of the radius it occupies a narrow interval
between the ulnar flexor and ulnar extensor muscles. Throughout the
greser part of its course in the forearm the nerve is superficial. Close
to the carpus it divides into a superficial and a deep branch. The
ramus superficialis bends round the tendon of the ulnar extensor,

pierces the deep fascia, and has already been noted as a cutaneous
Digitized by Microsoft®

THE LIMBS OF THE HORSE 49

nerve distributed over the lateral and dorsal surface of the carpus and
metacarpus. The ramus profwndus, under the tendon of thé ulnar
flexor of the carpus, unites with the lateral volar nerve, one of the
terminal branches of the median.

M. extensor carpi radialis. —

.

_ M. extensor digi-
torum communis.

N. cutaneus _
antibrachii

lateralis, |. A. collateralis

radialis.

M. brachialis.

N. radialis.

Vicephalica, FSB OM I Qa eS eS

M. biceps & :
brachii. = | \ i ees — Radius.

— M. extensor digiti

quinti,

ae _ M. extensor digi-
\ - torum communis.
Rams SSS a ~ A, interossea

: dorsalis.

Lig. collaterale
mediale.

V. mediana.

‘.medianus. “E\r Y\ for NRR. ow CON SOG EE -- - -- = - -- ~ Una.

ulnaris.

Riis C

revere

ye NM " Me sy 4
AN : on, M. extensor carpi

A. mediana.

Vv; imeniaine Sy

M. flexor carpi radialis. .

__M. flexor digitorum
profundus (caput
humerale).

2 fs
Z

‘
NS

Pid
x # f

M. flexor coe uwluaris.
M. flexor digitorum sublimis.

ra ——M. flexor digitorum
: profundus (caput
M. pectoralis :

superticialis. ulnare).

M. flexor carpi ulnaris : V collateralis nluaris.
(caput ulnare). . A. collateralis ulnaris.
N. ulnaris.

Fic. 31.—Section across the Forearm at the Level indicated by A in Fig. 30.

Collateral branches leave the ulnar nerve in the proximal part of
the forearm and are distributed to the flexor carpi ulnaris, flexor digi-
torum sublimis, and the ulnar head of the flexor digitorum profundus.

A. COLLATERALIS ULNARIS (PROXIMALIS)—On its origin from the
brachial the collateral ulnar artery follows the distal border of the

dial head of the triceps towards the elbow joint. Under cover of
een Dipitized by Microsoft® ’ 4

50 TOPOGRAPHICAL ANATOMY OF

the tensor of the antibrachial fascia the artery meets the ulnar nerve
and the two travel down the forearm in close company.

The collateral wlnar artery furnishes branches to the adjacent
muscles, the elbow joint and the skin, and ends by joining the lateral

Derse!

M. extensor carpi radialis... |

A. collateralis radialis.

ZG
a \
N. cutaneus anti- ; : eee
brachii lateralis. ~~~ _ El ‘e\_ M. extensor digitorum
V.cephalican EQ @Q@ '° Sf leer TT communis.
. ae a aa .
aa > —_—~. Zt. radialis.
V. cephalica ; ; eee.
: Ber Sa a ks 2 Me
antibrachii. ~~ a OD a ; _UIna.

Latere |

A. mediana. ___

N. medianus M. extensor digiti
NN. ala =

quinti. her laa Ca
V. mediana, heite

M, flexor carpi F| _ M. extensor carpi
radialis. : ulnaris.
vias sy Letecalis

_ M.Iflexor digitorum
profundus (caput
humerale).

—~-— — M. flexor digitorum{profundus

IEW ae
M. flexor carpi ulnaris.,” LER (exput winare).
2 4 ‘Ne
i ' <
M. flexor digitorum sublimis. N. ulnaris. V. collateralis ulnaris.

Fic. 32,.—Section across the Forearm at the Level indicated by B in Fig. 30.

volar metacarpal artery underneath the tendon of the ulnar flexor
of the carpus.

V. COLLATERALIS ULNARIS.—The collateral ulnar vein is a companion
of the like-named artery and ends by pouring its blood into the brachial
vein. At the carpus it is connected with the lateral volar fietacarpal vein.

N. MEDIANUS.—The median nerve has been followed in the arm
where it lies along the anterior border of the brachial artery. The
nerve, running in the groove between the biceps and the medial col-
lateral ligament, follows the median artery into the forearm where the

first part of its course is superficial; soon, however, the nerve as well
Digitized by Microsoft®

N. cutaneus antibrachii
lateralis. ’
Y. cephalica accessoria. ——

N. cutaneus antibrachii
lateralis.
V. cephalica antibrachii.

M. flexor carpi radialis. -

THE LIMBS OF THE HORSE 51

as the artery buries itself between the radius and the flexor carpi
radialis muscle, and, later, between this muscle and the deep flexor of
the digits. In some instances the nerve becomes again superficial just
as it is about to terminate in the distal third of the forearm in the
depression bounded by the flexor carpi ulnaris and flexor carpi radialis.

The exact relation of the median nerve and artery at the level of

M. extensor carpi radialis.

_ M. extensor digitorum
communis.

Radius. _N. radialis.

M. abductor pollicis.

M. extensor digiti

A. mediana, . _quinti.

V. mediana.
N. medianus.

- M. extensor carpi
ulnaris.

M. flexor digitorum
profundus (caput
humerale).

M. flexor carpi wnaris,~~ (caput ulnare).

X “ f
i \V. collateralis,ulnaris.
\
M, flexor digitorum sublimis, N. ulnaris.

Fic. 33.—Section across the Forearm at the Level indicated by C in Fig. 30.

the elbow joint and in the most proximal part of the forearm is subject
to variation—a circumstance that must be kept in mind in connection
with operations in this region. Commonly, the nerve passes obliquely
over the medial face of the artery, as the elbow joint is being crossed.
It may, however, run for a distance upon (that is, superficial to) the
artery. Or it may follow ‘the anterior (dorsal) border of the artery
throughout.

The median nerve ends by dividing into the medial and lateral
volar nerves. The collateral branches are all given off a short distance

jai the. flexor i radialis and the
beyond the elbow Jpiniraad SyRicrosone =" CP: Taal

A. interossea dorsalis.

~M. flexor digitorum profundus

L

Gt,

52 TOPOGRAPHICAL ANATOMY OF

humeral and radial heads of the deep flexor. A very minute inte7-
osseous nerve (n. interosseous) passes through the gap between the
radius and the ulna and ends in the periosteum.

A. MEDIANA—The median artery, the direct continuation of the
brachial, follows the median nerve very closely. As the two structures
cross the line of the elbow joint, it is customary for the nerve to
traverse the medial face of the artery obliquely and thereafter follow its

M. extensor carpi radialis.

N. cutaneus antibrachii A. collateralis radialis.

lateralis S
V. cephalica accessoria. _

Radius, ._
_M. extensor digitorum
communis.

M. abductor pollicis.

B= i Dorsal interosseous

N. cutaneus antibrachii-
lateralis.

V. cephalica antibrachii. -

ar =; vessels.
M. flexor digitorum pro-— : iit
fundus (caput radiale). ee digiti

A, mediana.-

V. mediana.—

M. flexor digitorum
profundus (caput
humerale).

N. medianus. —
M. flexor carpi radialis..§

-.M. extensor carpi
ulnaris.

j 7. 7 7 ”
M. flexor carpi ulnaris.-~ e (} S* M. flexor digitorum profundus
(caput ulnare),
~-WN, ulnaris.
%
\ ‘“.N, collateralis ulnaris.

- %
M. flexor digitorum sublimis. V. collateralis ulnaris.

Fic. 34.—Section across the Forearm at the Level indicated by D in ig. 30.

posterior border for a variable distance, but other relations are possible,
as mentioned above.

In the space between the radial and ulnar flexors the artery ter-
minates, after giving off the medial and lateral volar metacarpal
arteries. by becoming the common digital artery.

In addition to articular, muscular, and cutaneous branches, the
median furnishes the common interosseous artery and the artery of the
volar rete of the carpus.

A. INTEROSSEA COMMUNIS.—The common interosseous artery arises
opposite the space between the radius and the ulna. In the dog and
pig it divides into volar and dorsal interosseous branches, but in the

horse the volar is verypgmpallarapaepto sdnethis animal, therefore, the

THE LIMBS OF THE HORSE 53

common interosseous may be regarded as being continued between the
radius and ulna as the dorsal interosseous artery, the course of which
has already been followed in the anterior radial region.

A. RETIS CARPI VOLARIS.—In the distal third of the forearm a small
vessel leaves the median artery and passes down to the volar aspect
of the carpus, where it assists the volar metacarpal arteries in the
formation of a network of small vessels, the rete carpi volaris.

M. extensor carpi radialis. A. callateratis radialis.
/ fi i v

_M. abductor pollicis.

- M. extensor digitorum

Radius. communis.

a , aS -
SEA are AAR
ND

.- M. flexor digitorum pro-
tundus (caput radiale).

V. cephalica antibrachii. M. extensor digiti quinti.

M. tlexor carpi radialis.
_ M., flexor digitorum pro-

V. mediana. fundus (caput humerale).

A. mediana. -
V. mediana. ~

N. medianus.

- M. flexor digitorum pro-

M. flexor digitorum ~~
i fundus (caput ulnare).

sublimis.

M. flexor carpi ulnaris. V.collateralis =< A, collateralis ulnaris.
ulnaris. N. ulnaris.

Fie. 35.—Section across the Forearm at the Level indicated by E in Fig. 30.

Vv. mepran#.—As a rule there are two median veins, one following
each border of the median artery, radicles of which are contributed by
each of the three metacarpal veins. A common interosseous vein (v.
interossea communis) joins the posterior median, as does also a large
vessel that drains the deep flexor muscle of the digits.

The metacarpal region and the digits as far as the margin of the hoof
must next be examined. The “foot” can be satisfactorily dissected only
in a specimen that has been specially prepared so as to allow of the
removal of the hoof without injury to the soft structures contained
therein, and this is not possible in the preserved limb upon which the
dissection, so far, has been performed.

Before the removal Siothed by EbERBIRS by sight and touch the

| MM. extensorcarpi ulnaris. igure el

a4 TOPOGRAPHICAL ANATOMY OF

position of the metacarpal bones and the first phalanx. A large amount
of the anterior (dorsal) surface of the third metacarpal bone can be felt
through the skin. The tendons of the digital extensors, however, over-
he it in part, and their position should be determined by palpation.
The small second and fourth metacarpal bones should be followed
from the vicinity of the carpus to the distal third of the meta-

M. extensor carpi radialis. M. extensor digitorum communis.

_ Radius

M. abductor
puliicis.

-M. extensor digiti
quinti. LbE

Lig. collaterale

. essory carpal
mediale. Accessory cary

bone (pisiform).

M. flexor carpi

radialis. EL Sy —.M. extensor carpi
Z INE S ulnaris.
V. cephalica antibrachii. .~ ev eo oe & UL.

x
~~ M. flexor digitorum

Mm o.
A. metacarpea volaris -“ .”
x profundus.

medialis. ;
A. digitalis communis. 7
N. volaris medialis. ’

~- N, ulnaris (ramus

superficialis).
M. flexor digitorum sublimis. N. volaris : N. ulnaris (ramus profundus).
lateralis. A. metacarpea volaris lateralis.

Fic. 36.—Section across the Most Distal Part of the Forearm at the Level indicated by F
in Fig. 30.

carpal region, where commonly their expanded distal ends can be
detected.

The prominent line of the flexor tendons can be followed with ease.
Between them and the metacarpal bones is a groove on each side of the
limb, and herein a gradually increasing ridge—formed by the middle
interosseous muscle—can be determined.

Over the prominence corresponding to the sesamoid bones of the
first phalanx is a tuft of long hairs (their length varies with the breed
of horse) among which a horny callosity, the “ergot,” will be found
resting upon a fibrous cushion. It is generally accepted that the
“ergot” is the homologue of the large central foot-pad of the dog;
and it is assumed that, though now rudimentary and vestigial, it
was of considerable functional importance in those ancestors of the

horse that were digitigyade.e d by Microsoft®

THE LIMBS OF THE HORSE 55

Roughly on a level with the middle of the first phalanx there is
a depression bounded by the bone and the flexor tendons. Lastly, the
region adjoining the hoof on each side of the digit should be manipulated

to detect the presence of normally resilient cartilaginous extensions of
the third phalanx.

Dissection.—Having made a careful examination of the surface, now
remove the skin, and in doing so exercise caution lest the vessels and
nerves of the region should be injured. Pay particular attention to the
disposition of the deep fascia.

In cleaning the surface of the flexor tendons do not remove the
lumbrical muscles that lie along the side of the tendons in the distal
part of the metacarpus.

FASCIA OF THE METACARPUS AND DIGIT.—The deep fascia of the
metacarpus and digit (fascia metacarpea et digitalis) demands special
attention because of its notable strength and characteristic disposition
on the volar aspect of the limb.

In the proximal part of the metacarpus a strong sheet, continuous
with the transverse carpal ligament, crosses from the second to the
fourth metacarpal bone and closely invests the flexor tendons. On the
volar aspect of the digit are well-marked transverse bands that form
sheaths for the flexor tendons and retain them in position. Opposite
the metacarpo-phalangeal joint a volar annular ligament assists the
sesamoid bones, to which it is attached, in the formation of a fibro-
osseous canal through which the flexor tendons play. Immediately
distal to this is a four-sided sheet of fascia, adherent to the surface
of the superficial flexor tendon and fixed by bands to the ends of the
medial and lateral borders of the first phalanx. This is the vaginal
ligament of the flecor tendons.

A third annular band, only partially visible at the present stage of
the dissection, is associated with the terminal part of the deep flexor
tendon, between which and the digital torus the greater part of it is
interposed. In general outline the band is crescentic, the horns of the
crescent being represented by strong fascial strands attached about the
middle of the borders of the first phalanx. Connected with each side
of this part of the tendon sheath is the so-called digament of the ergot,
which, beginning as a comparatively narrow band in the fibrous basis of
the “ergot,” crosses the digital artery and nerve obliquely, widens at the
side of the joint between the first and second phalanges, and merges
into the third annular band of fascia.

M. EXTENSOR DIGITORUM COMMUNIS.—The tendon of the common
extensor has been followed over the distal end of the radius and the
dorsal face of the carpus. It continues along the front or dorsal surface

of the metacarpus andy digit aay, ends at, Abe extensor process of the

56 TOPOGRAPHICAL ANATOMY OF

A mediana. __ : 4 yyy -A. and Vv. collateralis ulnaris.
Pu av / Weox e
Radius. _____- Para Sf / - N. winaris.
: \ f , ~ -M. flexoridigitorum sublimis.

~ - --A. inetacarpea volaris lateralis.

. flexor carpi a
Pender of wh Aes i _ —_-N.wnaris (ramus superficialis),

radialis.
N. volaris lateralis.

- -- Tendon of m. flexor carpi ulnaris.

Tendon of m. abductor __

i - ~A. digitalis communis.
pollicis.

A. metacarpes volaris ____¥
medialis.

A. metacarpea dorsalis ____
medialis.

Communicating branch to n, volaris
lateralis.

Second metacarpal bone. _. __

| -.. ..-- -— ~ ‘lendon of m. fiexor digitorum

Third metacarpal bone. sublimis.

}-----~---- V. digitalis communis.

M. interosseus, ---- |

Dorsal branch of n. volarig _
medialis.

Volar branch of n. volaris
medialis.

a

Tendon of m. extensor ____
digitorum communis.

Fic. 87.—Medial Aspect of the Carpus, Metacarpus and Digit.

Digitized by Microsoft®

THE LIMBS OF THE HORSE 57

-

third phalanx. At the proximal end of the metacarpus the tendon is
placed decidedly lateral to the middle line of the limb. This position,
however, is gradually changed until, by the time the metacarpo-
phalangeal joint is reached, the tendon is equidistant from the two
borders of the limb. In the neighbourhood of this joint, also, as well
as in the digit, the tendon is wider and thinner than elsewhere. It is
intimately connected with the capsules of the several joints associated
with the phalanges, but a synovial bursa of limited extent is placed
between the tendon and the capsule of the metacarpo-phalangeal
articulation.

In the proximal third of the metacarpus a strong fascial band from
the lateral aspect of the carpus is connected with the extensor tendon,
and about the middle of the first phalanx each border of the tendon is
joined by a strong oblique offset from middle interosseous muscle.

M. EXTENSOR DIGITI QuinTI—After passing through the liga-
mentous canal at the lateral border of the carpus, the tendon of this
muscle pursues an oblique course along the dorsal-lateral part of the
metacarpal bone and is inserted to the proximal part of the dorsal
(anterior) surface of the first phalanx.

Soon after its entry into the metacarpal region the tendon is
joined by the thin tendon of the muscle of Phillips and a strong fascial
band from the lateral part of the carpus. Compact hitherto, the tendon
now broadens, and not infrequently divides into more or less isolated
bundles of fibres. A small synovial bursa lies beneath the tendon as it
crosses the head of the third metacarpal bone and the joint between
this bone and the first phalanx. ;

M. FLEXOR DIGITORUM SUBLIMIS.—The tendon of the superficial
digital flexor demands careful examination. In the first place it will be
noticed that it passes through fascial sheaths—lined by synovial tendon
sheaths—at the carpus and in the region of the metacarpo-phalangeal
joint.

The tendon leaves the forearm by running through the roughly
triangular passage or canal bounded by the carpus in front, the accessory
carpal (pisiform) bone laterally, and the transverse ligament of the
carpus on the volar side. In its passage through the canal the flexor
tendon is enclosed in a synovial investment (vagina carpea) the extent
of which is to be determined by dissection.

In the digital region the tendon traverses the canal formed by the
phalanges (and the superposed ligaments) and the specialised fascial
bands (fibrous tendon sheaths) already noted, and is surrounded by a
second synovial or mucous sheath.

Turning now to the, dendop, tage, dk wall be found that until it

58 TOPOGRAPHICAL ANATOMY OF

arrives at the distal part of the metacarpus it is only slightly flattened.
From this point onwards the flattening becomes more and more pro-
nounced. In the distal fourth of the metacarpus the tendon of the
superficial flexor has an annular appendage through which the tendon
of the deep flexor passes. At about the middle of the first phalanx
the superficial tendon splits into two limbs that are inserted to the
proximal part of the volar aspect of the second phalanx and to the
immediately adjacent parts of the first phalanx.

M. FLEXOR DIGITORUM PROFUNDUS.—The tendon of the deep flexor
accompanies the superficial tendon down the back of the carpus—-where
the two structures are enclosed in a common synovial or mucous sheath
—metacarpus and digit. In the distal fourth of the metacarpus the

/ Ch- M. extensor digiti quinti. Lah iB Gee

M. flexor digitorum
sublimis.

) M. extensor digitorum
- communis.

Fic. 38.—Lateral Aspect of the Skeleton of the Digit, with Areas of Muscular Attachment.

tendon traverses the ring provided by the superficial tendon and then
plays over the groove-like surface formed by the two sesamoid bones
and the cartilage that clothes their volar face. Then, passing between
the two limbs into which the superficial tendon finally divides, it
crosses the sesamoid bone of the third phalanx and is inserted to
the flexor area of the third phalanx. The ultimate insertion cannot
be examined as yet, inasmuch as it is buried within the hoof.
Careful note should be made of the extensive synovial or mucous
sheath associated with the deep and superficial tendons beginning in
the distal fourth of the metacarpus and continued to the middle of the
second phalanx, where it comes into contact with a similar sheath
clothing the deep tendon as it plays over the sesamoid bone of the

third phalanx.
Digitized by Microsoft®

THE LIMBS OF THE HORSE 59

A strong reinforcing tendinous band (caput tendineum) of some
physiological importance passes from the back of the carpus, where it
is connected with the volar carpal ligament, and joins the deep flexor
tendon about the middle of the metacarpus.

There can be little question that the tendinous heads of the super-
ficial and deep flexors serve the purpose of mechanical stays to the limb
and so relieve the fleshy part of these muscles from strain when the
standing posture is long maintained.

THE SYNOVIAL SHEATHS (VAGINA:! MUCOSM) OF TENDONS.—At this
stage of the dissection it is advisable to make a general review of the

bi. AI. interosseus.

_, M. flexor digitorum sublimis.

: 4 M. flexor digitorum profundus.

Fic. 39.—Volar (Posterior) Aspect of the Skeleton of the Digit, with Areas of
Muscular Attachment.

synovial or mucous sheaths, connected with the extensor and flexor
tendons, in the carpal, metacarpal, and digital regions.

Each extensor tendon is furnished with an independent sheath as
it plays through the groove provided for it at the distal end of the
radius. All the sheaths begin, roughly speaking, on a level with the
upper edge of the accessory carpal (pisiform) bone. The sheath of
the extensor carpi radialis ends close to the insertion of the muscle.
The sheath of the extensor carpi ulnaris belongs to that tendon of the
muscle which lies in the oblique groove on the lateral surface of the
accessory carpal bone, and terminates near the insertion of this tendon
into the fourth metacarpal bone.

The synovial sheaths of the extensor digitorum communis and
extensor digiti quinti end in the proximal fourth of the metacarpus;

DigitiZaeh VierOsene@

60 TOPOGRAPHICAL ANATOMY OF

a short diverticulum from the sheath of the common extensor follows
the thin tendon of Phillips’ muscle for a distance towards its union
with the tendon of the extensor digiti quinti. There is, however, no
union between the synovial sheaths of the two tendons.

The slanting abductor pollicis has a sheath that ends close to the
insertion of the tendon into the base of the second metacarpal bone.

A small synovial bursa lies under the tendon of each of the
extensors of the digits as it crosses the joint between the third meta-
carpal bone and the first phalanx.

The tendon of the flexor carpi ulnaris has no sheath. The radial
flexor has a sheath very similar in extent to that provided for the
radial extensor. The most proximal limit of this sheath is, roughly,
7 to 8 cm. above the radiocarpal joint, and the sheath is continued
almost to the insertion of the tendon into the second metacarpal bone.

Two common sheaths enclose the tendons of the superficial and
deep flexors of the digit. One of these begins about 8 to 10 cm. above
the radiocarpal joint and ends near the middle of the metacarpus.
The second sheath extends from the distal fourth of the metacarpus
to the middle of the second phalanx.

The tendon of the deep flexor muscle has, in addition, a third
sheath (to be examined later), where it plays over the sesamoid bone
of the third phalanx.

Mm. LUMBRICALES.—In the distal part of the metacarpus a pale,
weak, and variable lumbrical! muscle will be found attached to each
border of the deep flexor tendon. The slender tendon of each is lost
in the fibrous basis of the “ergot.” These muscles cannot be regarded
as of functional value, but are of interest as being vestiges of structures
that formerly served a definite purpose.

Mm. INTEROSSEI—Like the lumbricals, the interosseous muscles
have been profoundly affected by the marked modifications that have
taken place in the manus during the evolution of an animal with only
one functional digit. Three interosseous muscles are represented in
the modern horse, but, of these, two, which may be named medial and
lateral, are rudimentary. They have a slender, pale fleshy belly arising
from the base of the second or fourth metacarpal bone as the case may
be. Very attenuated tendons end variously in the neighbourhood of
the metacarpo-phalangeal joint.

The middle interosseous muscle (m. interosseous medius) has,
during its evolution, increased considerably in size—in conformity with
the great increase in the size of the digit with which it is associated—
and has so changed in structure that it is now almost entirely tendinous.

! Lumbricus [L.}, an earthyorm, n the shape of the muscles in man.
"Digitized by } WharoscRe

THE LIMBS OF THE HORSE 61

Some few scattered bundles of muscular tissue, more obvious in the
young than in the old, still remain as a record of its ancestral history.
The strong, flattened tendinous band into which the muscle has been
transformed lies between the flexor tendons and the groove-like space
formed by the three metacarpal bones. Its origin, confused with the
volar carpal ligament, is from the posterior surface of the distal row
of carpal bones and the neighbouring part of the third metacarpal.

In the distal third of the metacarpus the band divides into two
limbs, each of which is attached to a sesamoid bone. <A continuation
of each limb passes obliquely across the border—medial or lateral, as

Third metacarpal bone. M. extensor digitorum communis.

ys A. metacarpea dorsalis
o lateralis.

MEDIAL

A. metacarpea dorsalis.
medialis.

_ Fourth metacarpal bone.

LATERAL

-M. extensor digiti

Second metacarpal inti
an quinti.

bone.

eee ,M. interosseus.
A. metacarpea volaris medialis.:~

V. digitalis communis. **

M. flexor digitorum profundus (caput
tendineum). ae
A. digitalis communis.

N
‘<.V. metacarpea volaris
a lateralis.

q A. metacarpea volaris lateralis,

vi: \._N. volaris lateralis.

N. volaris medialis. ~ ‘M. flexor digitorum profundus.
i

M. flexor digitorum sublimis.

Fig. 40. —Section across the Metacarpus at the Level indicated by G in Fig. 30.

the case may be—of the first phalanx to reach the dorsal aspect of this
bone and here join the tendon of the common extensor of the digit.

The strong tendinous structure representing the middle interosseous
muscle obviously serves as a mechanical stay when the weight of the
body is sustained by the limb, and thus prevents over-extension of
the metacarpo-phalangeal joint, while, at the same time, removing strain
from the flexor muscles.

ARTERIES OF THE METACARPUS AND DIGIT.—As has been seen, the
median artery terminates as the common digital, and, at the same
point, contributes the medial and lateral volar? metacarpal arteries.

The medial volar metacarpal artery (a, metacarpea volaris medialis)
follows the tendon of the flexor carpi radialis very closely in its course
down the medial posterior part of the carpal region. Having distri-
buted twigs to the rete carpi dorsalis, the artery sinks into the cleft

1 Vola [L.], the palm.
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62 TOPOGRAPHICAL ANATOMY OF

between the second metacarpal bone and the middle interosseous
muscle. It follows the medial margin of the deep face of the modified
muscle, supplies the nutrient artery of the third metacarpal bone, and

Third metacarpal bone.

i M. extensor digitorum
communis.

M. extensor digiti © D E

Second metacarpal bone, _ quinti.

~... Fourth metacarpal

<=
Jey bone.
@ 3 .V. metacarpea volaris lateralis.
3 A. metacarpea volaris lateralis.
(\=-- N. volaris lateralis.
Q M. flexor digitorum profundus.

M. flexor digitorum sublimis.

M. interosseus. ..
V. digitalis communis. -..-§
N. volaris medialis.

A. digitalis communis. *

Fic. 41.—Section across the Metacarpus at the Level indicated by H in Fig. 30.

ends in the distal third of the metacarpus by uniting with the slender
termination of the lateral volar metacarpal artery. The union of the

M, extensor digitorum communis.

Third metacarpal one.

M. extensor digiti quinti. LOE

M. interosseus. - M. interosseus.

A. digitalis volaris medialis. _ not

A. digitalis volaris lateralis. { ¢ ec? \
V. digitalis lateralis.’
-N, volaris lateralis.

LH. volaris medialis. -

!

V. digitalis medialis. ~

o
M., flexor digitorum profundus.~

Fic. 42.—Section across the Metucarpus at the Level indicated by I in Fig. 30.

two vessels results in the formation of a small artery that, passing
between the two limbs of the interrosseous muscle, joins either the
common digital or the lateral volar digital artery.

The lateral volar metacarpal artery (a. metacarpea volaris lateralis)
is smaller than the medial vessel of the same name. Under cover of
the tendon of the flexor carpi ulnaris it unites with the terminal part

of the collateral ulnar artery. After passing the carpus along the
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THE LIMBS OF THE HORSE 63

lateral edge of the flexor tendons, it enters the narrow interval between
the fourth metacarpal bone and the middle interosseous muscle, and

M. extensor digitorum communis. 7 _ ML. extensor digiti quinti.

_ Third metacarpal bone.

Lig. collaterale mediale.- Lig. collaterale lateral
g. evale laterale,

M. interosseus.-

— Sesamoid.

~.V. digitalis lateralis.

. N. volaris lateralis (ramus
dorsalis).
~~. A. digitalis volaris lateralis.

N. volaris medialis ~~
(ramus dorsalis).

A. digitalis volaris medialis,.~7

N, volaris medialis (ramus volaris)
V. digitalis medialis.-”

» N, volaris lateralis (ramus
volaris).

~ M. flexor digitorum sublimis.

M. flexor digitorum profundus. .~

Fie, 43.—Section across the Distal End of the Metacarpus as indicated by J in Fig. 30.

thereafter pursues a course comparable to that of the medial artery

of the same name.
In the proximal part of the metacarpus transverse vessels unite

, M. extensor digitorum communis.
First phalanx. , 7
thy

M. interosseus.~_

M. interosseus.

V. digitalis medialis.

N. volaris medialis (ramus
dorsalis). tens

A. digitalis volaris medialis.

~V. digitalis lateralis.

N. volaris medialis (ramus ~

volaris). ~SN. volaris lateralis (ramus

dorsalis).

*,
~ N. volaris lateralis (ramus

2 /
Lig. sesamoideum obliquum./ 7

“a hed volaris).
Pd vi
Lig. sesamoideum rectum. : : A. digitalis volaris lateralis.
M. flexor digitorum prafindiis. Lig. sesamoideum obliquum.

M. flexor digitorum sublimis.

Fre. 44.—Section across the First Phalanx at the Level indicated by K in Fig. 30.

the two volar metacarpal arteries by crossing the limb deep and
superficial to the middle interosseous muscle. These communicating

vessels constitute the eee i polar ards jsereles volaris profundus).

64 TOPOGRAPHICAL ANATOMY OF

Very slender dorsal metacarpal arteries (aa. metacarpea dorsalis
medialis et lateralis) will be found in the shallow grooves at the line
of junction of the second and third and third and fourth metacarpal
bones. These vessels arise from the rete carpi dorsalis, and are con-
nected with the volar metacarpal arteries by small communicating
vessels that cross the surface of the second and fourth metacarpal
bones close to their bases.

The dorsal metacarpal arteries can often be followed to a union
with the volar arteries in the distal third of the metacarpus.

M. extensor digitorum communis.

First phalanx, ._

Lig. sesamoideum rectum.

V. digitalis lateralis.

V. digitalis medialis. a? Poe
2 M. flexor digitorum sublimis.

N. volaris medialis

(ramus dorsalis),~ N. volaris lateralis (ramus

dorsalis).

me x
A. digitalis volaris medialis. ~ a “A. digitalis volaris lateralis.

,

N. volaris medialis M. flexor digitorum N. volaris lateralis (ramus
(ramus volaris), profundus. volaris).

Fie, 45.—Section across the First PhaJanx at the Level indicated by L in Fig. 30.

The common digital artery (a. digitalis communis) is the direct
continuation of the median, and follows the medial border of the flexor
tendons behind the carpus and metacarpus. As the level of the
sesamoid bones is approached, the artery gains (approximately) the
middle line of the limb by sinking between the middle interosseous
muscle and the tendon of the deep flexor. Immediately proximal
to the sesamoids the common digital divides into the medzal and
lateral volar digital arteries (aa. digitalis volaris medialis et lateralis).

Each volar digital artery follows the appropriate border of the
flexor tendons, passes under the cartilaginous appendage of the third
phalanx, and finally enters the volar foramen of the third phalanx.
Both arteries contribute similar branches to the digit. Some of these
are distributed on the dorsal, some on the volar aspect. Like
branches of the two arteries anastomose with each other in the
middle line of the limb, and thus produce a series of vessels that
encircle the digit at different levels. Small twigs ave also furnished
for joints, tendons, “ergot,” and skin,

The named branches of the digital arteries are as follows:—
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THE LIMBS OF THE HORSE 65

(1) Rami dorsales phalangis prime—On a level with the middle
of the first phalanx a dorsal branch arises from each digital artery
and passes between the common extensor tendon aud the bone.
(2) Rami volares phalangis prime.—At the same level as the fore-
going, volar branches take origin and encircle the digit beneath the
flexor tendons. Not infrequently the dorsal and volar rami arise from
a short common trunk, the artery of the first phalanx (a. phalangis
prime). (3) Aa. torice phalangis terticc—Shortly distal to the pre-
ceding, small branches are given off by the digital arteries to be
distributed mainly in the digital torus. The remaining branches of
the digital arteries can only be examined properly during the dissection
of the contents of the hoof. They are:—(4) Rami dorsales phalangis
secunde ; (5) ramt volares phalangis secunde: ; (6) aa. coronales phalangis
tertie ; and (7) aa. dorsales phalangis tertin.

DiciTaL veINS.— When the contents of the hoof come to be
examined, it will be found that the veins therein form a rich and
close-meshed network. From this spring two veins (vv. digitalis
medialis et lateralis) that accompany the digital arteries. It should
be noted that each digital vein is dorsal to (ze in front of) the
corresponding artery.

Between the flexor tendons and the middle interosseous muscle,
and immediately proximal to the sesamoid bones, there is an anasto-
motic union of veins known as the volar venous arch (arcus venosus
volaris). Connected with the arch are the digital veins on the one
hand, and the veins of the metacarpus on the other.

VEINS OF THE METACARPUS.—(1) Beginning at the volar venous
arch, the common digital (or medial metacarpal) vein (v. digitalis
communis) is a companion of the lke-named artery. At the
carpus, however, its chief connection is with the origin of the
cephalic vein of the forearm, though it is also connected with the
median vein. (2) The lateral volar metacarpal vein (v. metacarpea
volaris lateralis) accompanies the artery of the same name to the
carpus. In this region it is connected with both the median and
the collateral ulnar veins. (3) The deep volar metacarpal vein (v.
metacarpea volaris profunda) is variable. Lying between the third
metacarpal bone and the interosseous muscle, its main connection
is with the median vein.

NERVES OF THE METACARPUS. AND DIGIT.—At a variable point in
the distal half of the forearm the median nerve divides into two
terminal branches — the medial and lateral volar nerves. The
medial volar nerve (n. volaris medialis) follows the common digital

artery along the medial, border, af the flexor tendons down the back

5

66 TOPOGRAPHICAL ANATOMY OF

of the carpus and through the metacarpal region. At the carpus
the relative positions of the nerve and artery do not remain con-
stant; but in the metacarpus the nerve lies behind the artery.
In the metacarpus, therefore, the common digital vein, the common
digital artery, and the medial volar nerve lie together in the order
in which they are here enumerated, the vein being the most anterior
of the three structures. About the middle of the metacarpus an
oblique communicating branch from the medial volar nerve crosses
the flexor tendons superficially to join the lateral volar nerve.

The lateral volar nerve (n. volaris lateralis) crosses the surface
of the superficial flexor tendon obliquely in order to gain a more
lateral position, and, under cover of the tendon of the flexor carpl
ulnaris, is joined by the deep or terminal branch of the ulnar nerve.
After this union, the volar nerve passes down the back of the carpus,
partly embedded in the transverse ligament, and, on reaching the
metacarpus, follows the lateral border of the flexor tendons, where
it bears the same relations to the lateral volar metacarpal vein and
a small branch of the lateral volar metacarpal artery as does the
medial nerve to the common digital vessels. For surgical reasons it
is necessary to remember that, while the medial volar nerve is
accompanied by a large artery, the lateral nerve is related to a
small one; and it is further to be noted that the medial nerve is
forsaken by the common digital artery when this vessel sinks
towards its termination just proximal to the sesamoid bones.

A deep branch of the lateral volar nerve arises behind the carpus,
and terminates in numerous filaments that supply the three inter-
osseous muscles. This nerve is of some moment inasmuch as it is
responsible for the sensibility of the middle interosseous muscle
(suspensory ligament); and apparently, like the volar nerve from
which it arises, it contains fibres derived from both the ulnar and
median nerves.

On a level with the metacarpo-phalangeal joint each volar nerve
divides into two branches: (1) The volar branch (ramus volaris), the
larger of the two, follows the posterior border of the digital artery,
and will be found again during the examination of the contents of
the hoof. (2) The smaller dorsal branch (ramus dorsalis) crosses the
digital artery superficially, and runs along the side of the digit
between the artery and its companion vein. This branch distributes
filaments to the skin in front of the digit, and to the coronary
matrix of the hoof.

It is worthy of observation that, at the middle of the first phalanx,

there are commonly three nerves with an artery and vein in close
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THE LIMBS OF THE HORSE 67

relation. Enumerated from behind forwards, these structures are as
follows:—The volar ramus of the volar metacarpal nerve; the digital
artery; the dorsal ramus of the nerve; the digital vein; a branch
of the dorsal ramus of the nerve.

In the consideration of this region from the surgical point of
view it is also necessary to remember that the volar and dorsal rami
of each nerve are connected by anastomotic filaments, with the

Scapula. Coracoid process. Origin of m. biceps brachii.
' Z , M. supraspinatus.

2
Penney Lem

_ Greater tubercle of
Z humerus.

‘\\\ NK
a :
1D _M. biceps brachii,
hae

Insertions of m. infraspinatus.

\V, SSE ~ :
Toint capsule. \ \ ah \\\ ee rr Crest of greater
aN i, tubercle.
M. capsularis. \\
»~" \
\\, ,
: —»_-L__ -__~ .Deltoid tuberosity

Humerus. - - -— --}--.-_.

Fic. 46.—Lateral Aspect of the Shevstear Joint.
The red line indicates the extent of the synovial bursa between the

lateral tendon of insertion of m. infraspinatus and the convex area

of the greater tubercle of the humerus.
result that their areas of distribution are ill-defined and overlap
each other. This confusion of territory is, however, more pronounced
in front of the digit than behind; so that division of the volar
ramus destroys sensation in the more volar structures contained
within the hoof.

Dissection.—The dissector must now examine the articulations of the
limb, with the exception of those between the three phalanges of the
digit which will be dissected in connection with the contents of

the hoof.

THE SHOULDER JOINT (articulatio humeri)—The bony surfaces
entering into the formation of the shoulder joint are the glenoid
cavity of the scapula and the head of the humerus. It is note-
worthy that the glenoid cavity has scarcely more than half the area

of the humeral head. pjgitized by Microsoft®

68 TOPOGRAPHICAL ANATOMY OF

The necessity for many and powerful ligaments in connection with
the joint is obviated by the presence of the numerous strong muscles
that closely surround the articulation and hold the bones in their
place. As has been previously noted, the thick insertions of the
subscapular and infraspinous muscles act functionally as collateral
ligaments; while the supraspinous, biceps, and triceps have bony
attachments within a short distance from the joint. A further factor
in retaining the bones in apposition is atmospheric pressure; for,

Origin of m.
M, supraspinatus. biceps brachii. 4 g

---. Seapula.

M. biceps brachii.

She 3-=----5< M. coracobrachialis.
A ¢ Wwe Oo Joint capsule.
i we SSS CM. capsularis.

___ —M. subscapularis.

i
|
+-~--f—- ~~ Humerus.

Fie. 47.—Medial Aspect of the Shoulder Joint.

1,=The line of attachment of synovial bursa of m. biceps brachii.
2,=The line of attachment of synovial bursa of m. coracobrachialis.

though the bony surfaces are separated with difficulty so long as
the joint capsule is intact, if an opening is made into the capsule
the bones may be separated to the extent of 2 or 3 cm.

The only ligament connected with the joint is a capsule (capsula
articularis) attached 1 or 2 cm. from the margins of the glenoid
cavity of the scapula and the head of the humerus. The capsule
is strengthened by elastic fibrous bands, notably so by one that
springs from the base of the coracoid process of the scapula,
and splits into two limbs that are attached to the greater and
lesser tubercles of the humerus. On opening the capsule it will be
observed that its synovial lining is not, in the horse, in any way
connected with the synovial (mucous) sheath of the biceps tendon.

Although movement at the shoulder joint is possible in all

directions, flexion and_extension alone are of any marked degree of
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THE LIMBS OF THE HORSE 69

freedom. Adduction and abduction are restricted by the sub-
scapular and infraspinous insertions, and rotation and cireumduction
are limited by the other muscular attachments about the joint.

THE ELBOW JOINT (articulatio cubiti)—The term “elbow joint,”
strictly speaking, includes three joints, namely, the humero-radial

Lig. collaterale laterale. —

=

2 | att [. brachiali
/, < ! Wi --~ M. brachialis.
Ma 0
Dy)

RaditShas anaes see --_ ---~ ~Lig. collaterale mediale

(long).

Fic. 48.—Anterior Aspect of the Elbow Joint.
The red line indicates the line of attachment of the synovial lining of the joint capsule.

articulation (articulatio humeroradialis), the hwmero-ulnar articula-
tion (articulatio humeroulnaris), and the prowimal radio-ulnar articula-
tion (articulatio radioulnaris proximalis). In describing the joint of the
horse it is convenient to include the union between the shafts of the
racius and ulna as well.

The opposed bony surfaces of the humerus and the radius and ulna
are so moulded and adapted to each other as to convince the dissector
that movement in the joint can take place in one plane only. The
presence of strong collateral ligaments contributes to the limitation
of movement to flexion and extension.

The joint capsule (capsula articularis), attached to the articular

margins of all threen bones, is, sfrongesharn the extensor (anterior)

70 TOPOGRAPHICAL ANATOMY OF

aspect of the joint, where it is reinforced by oblique fibres; but behind,
where it is supported by the anconeus and triceps muscles, it is much
weaker and more membranous. The capsule is very firmly adherent
to the tendons of the various muscles that are inserted to the
proximal end of the radius, and to those that take origin from the
distal end of the humerus; and its synovial lining is continued for
a short distance along the tendons of origin of the flexors of the

Medial epicondyle of humerus. Olecranon.

1
'
!
1
'
'
'
'
|
+

eiererioe fot i oe

M. biceps
brachii. ‘

_f_____. . lig. collaterale
mediale (short).

QQ

_ _Lig. transversum.

sas

saan Ws AKL

M. brachialis, +---*§g ie .

Ad

Lig. collaterale - ~ fe
mediale (long).

Fic. 49.—Medial Aspect of the Elbow Joint.

The red line indicates the line of attachment of the synovial lining of the joint capsule.

carpus and digit, as well as into the small articulations between the
head of the radius and the ulna.

The medial collateral ligament (ligamentum collaterale mediale)
springs from the depression and prominence close to the articular
margin of the humerus, and is divisible into two parts. The longer
and more superficial (and more anterior) portion is attached to the
medial border of the shaft of the radius; while the shorter, stronger,
deeper, and more posterior part of the ligament ends on the prominence
at the medial part of the head of the radius. The most distal fibres
of the tendon of insertion of the brachialis muscle pass between the

two parts of the ligament.
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THE LIMBS OF THE HORSE TL

The lateral collateral ligament (ligamentum collaterale laterale) is
by far the stronger—as it is also the shorter—of the two ligaments.
It arises from a depression on the humerus, and ends on the prominence
at the lateral part of the head of the radius,

The firm union of the radius and ulna is effected by interosseous and
transverse ligaments.

The interosscous ligament (ligamentum interosseum) connects the two
bones closely and occurs both proximal and distal to the interosseous
space. It corresponds to the interosseous membrane of those animals
in which movement (supination and pronation) between the radius
and ulna is relatively free. ‘The horse has lost the power of supina-
tion, and the limb being in a permanent condition of pronation, the
fibres of the membrane (ligament) are consequently very short and
undergo a process of ossification as age advances. Distal to the inter-
osseous space, ossification is generally complete by the time adult
life is reached; but proximal to the space, osseous union of the radius
and ulna is rare except in very advanced age. It is obvious that,
because of the shortness of the fibres of the interosseous ligament,
there is at no time appreciable movement between the horse’s radius
and ulna: clearly ossification of the ligament abolishes all possibility
of movement.

The transverse ligaments (ligamenta transversa) consist of short
fibres that pass from the medial and lateral surfaces of the ulna to
the adjacent parts of the radius.

THE PROXIMAL RADIO-ULNAR ARTICULATION (articulatio radioulnaris
proximalis) is formed by the two small, smooth areas at the back of the
head of the radius and corresponding facets on the opposed part of the
ulna, and is included within the joint capsule of the elbow.

In the adult horse there is little or no trace of a DISTAL RADIO-ULNAR
ARTICULATION (articulatio radioulnaris distalis), because the distal end
(head) of the ulna, having become detached from the rest of the bone,
has fused with the distal end of the radius.

THE CARPAL ARTICULATIONS (articulatio carpi)—The carpal joint
is a complex collection of articulations between the distal end of the
radius, the individual carpal bones, and the bases of the three meta-
carpal bones. In consequence, the whole joint may be divided as
follows: (1) The radtocarpal articulation (articulatio radiocarpea), (2)
the intercarpal articulation (articulatio intercarpea) between the two
rows of carpal bones, (3) interosseous articulations (articulationes inter-
osseee) between the members of the same row of carpal bones, and (4)
the carpometacarpal articulation (articulatio carpometacarpea).

Before examining Oe eea Ry Mes ind the bones together, the

72 TOPOGRAPHICAL ANATOMY OF

dissector should satisfy himself as to the range and nature of the
possible movements. Obviously the arrangement itself of the bones
points to the hinge-like character of the combined articulations. The
most free movement is clearly one of flexion and extension; but this,
it must be remembered, is the result of the sum of the movements
between the radius and the carpus, and between the two rows of
carpal bones—the former contributing more than the latter. Between
the distal row of bones and the bases of the metacarpals there is no

Radius. - -

Accessory carpal bone
(pisiform). i

---- Lig. collaterale laterale.

= aed,
Intermediate carpal bone

(unciform).

(lunar).
~~ -~ Ulnar carpal bone (cunei-
‘ form).
244
, == .4- ---- 5.
3.0 AN J f J) -}- -. — Fourth carpal bone

Seosag Third metacarpal bone.

Fourth metacarpal. _ ___
bone.

Fic. 50.—Lateral Aspect of the Carpal Articulations,

Ligament from accessory carpal bone to radius.

Dorsal ligament from accessory carpal to ulnar carpal bone.

Ligament from accessory carpal to fourth carpal and fourth metacarpal bones.

Dorsal ligament connecting ulnar and intermediate carpal bones.

Dorsal ligaments connecting third and fourth carpal bones.

Dorsal ligaments connecting third and fourth carpal bones to third and fourth
metacarpals,

weed

ee)

Boe oO

movement of a nature that would add to flexion and extension, liga-
ments being so disposed as to prevent more than a limited amount of
gliding of one bone over another.

The movement of flexion is accompanied by the gliding of one
carpal bone over its neighbour; especially is this the case between the
different members of the proximal row.

Under normal conditions it is doubtful if there is any movement of
abduction and adduction in the carpal articulations themselves ; though,
owing to the form of the bony surfaces, the distal part of the limb is

slightly abducted during flexion, by Microsoft®

THE LIMBS OF THE HORSE 13

The ligaments of the carpal joint may be classified as (1) those
common to the whole series of articulations, (2) those joining two or
three bones together, and (3) those particularly connected with the
accessory (pisiform) bone.

The common ligaments consist of a joint capsule and two collaterals.

Joint capsule (capsula articularis).—The fibrous layer of the capsule
is of considerable thickness, especially on the volar aspect of the carpus.
It is attached to the radius close to its articular margin, the dorsal and

Saiseiecicinddee ss Radius.

Intermediate carpal bone.
(lunar).

qs
Lig. collaterale laterale.. KN ‘{__Radial carpal bone

(scaphoid).

Ulnar carpal bone_

(cuneiform), ee , |
7 ns // ;
i _.. Third carpal bone

Apatite ---Lig. collaterale mediale.

Fourth carpal bone-+-ky
(unciform). iN
9 \ easter:

AS =! Wy 1 ! (magnum).
OOM Zp Hy 8:
me se
Fourth metacarpal bone, _ \ 4 afl
Nine Eee
eon __ . Secondymetacarpal bone.

Third metacarpal bone. _ _

asi Soese

Fic. 51.—Dorsal (anterior) Aspect of the Carpal Articulations.

1.= Dorsal ligaments connecting the bones of the proximal row.
2. =Dorsal ligament connecting the third and fourth carpal bones.
3. = Dorsal ligaments connecting the third carpal and third metacarpal bones.

volar surfaces of the carpal bones and their associated short ligaments,
and the bases of the metacarpal bones. On the extensor (dorsal) aspect
of the carpus the capsule is connected with the fascia of the forearm,
and helps to bind down those extensor tendons that cross the carpus.
In accordance with the range of movement in the radiocarpal and
intercarpal articulations, the capsule is roomy on this face of the
carpus.

On the flexor (volar) aspect of the joint the capsule assists the
transverse carpal ligament in the formation of a short canal in which
the flexor tendons are contained, and is, consequently, covered by the
synovial (mucous) sheath of the tendons. It should be noted that the
great strength of this portion of the capsule is important as a check to
over-extension of the joint. Its connection with the tendinous head of

the deep flexor is also qhjspipe mhysiglogicalamoment.

74 TOPOGRAPHICAL ANATOMY OF

The synovial lining of the joint capsule is divided into three parts
in agreement with the three articulations over which the capsule
extends. Its radiocarpal part is most extensive, lubricates the radio-
carpal joint, and is continuous with the articulations of the accessory
carpal (pisiform) bone. It also lubricates the articulations between
the neighbouring bones of the proximal row above the interosseous
ligaments. The intercarpal part of the synovial lining lubricates the

emeceeahe comes and Radius.

Accessory carpal bone (pisiform).

(scaphoid).
Lig. collaterale mediale._ _ _

Third carpal bone _
(magnum).

} |
AA sou WE oy
4
4

Fie, 52.—Medial Aspect of the Carpal Articulations,

1.=Ligament from accessory carpal bone to radius.
2, =Ligament from accessory bone to fourth carpal and fourth metacarpal bones.

articulations between the two rows of bones, and extends between the
individual bones of a row as far as the interosseous ligaments. The least
extensive part (carpometacarpal) of the synovial lining is that con-
nected with the carpometacarpal articulation, the intermetacarpal
articulations, and the small joints between the members of the lower
row of carpal bones distal to the interosseous ligaments. The interior
of the intercarpa4l and carpometacarpal sacs intercommunicate by a
small passage between the third (magnum) and fourth (unciform)
carpal bones.

Lateral collateral ligament (ligamentum collaterale laterale)—The
fibres of the lateral collateral ligament spring from the projecting
lateral part of the end of the radius, and are attached to the ulnar
carpal bone (cuneiform), fourth carpal bone (unciform), and the base
of the fourth metacarpal bone. A few of the more superficial fibres

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THE LIMBS OF THE HORSE io

end on the third metacarpal bone. The ligament is pierced by a short
canal containing the tendon of the extensor digiti quinti.

Medial collateral ligament (ligamentum collaterale mediale).—The
medial collateral ligament has a concentrated origin from the projection
on the medial side of the end of the radius. By somewhat divergent
fibres it is attached to the radial carpal bone (scaphoid), first, second
and third carpal bones (trapezium, trapezoid, and magnum), and the
bases of the second and third metacarpal bones. The variable and
inconstant first carpal bone (trapezium) may be entirely embedded in
the ligament.

The medial collateral ligament is continuous with the transverse
ligament of the carpus, and assists in the formation of a canal for the
tendon of the flexor carpi radialis.

Of the short carpal ligaments the following are the most readily
dissected :—

Dorsal ligaments (ligamenta intercarpea dorsalia) connect each
carpal bone to its neighbour in the same row. In addition, a double
band passes obliquely from the third carpal (magnum) to the third
metacarpal bone. This is of some importance in connection with the
absence of flexion in the, carpometacarpal joint.

Volar ligaments (ligamenta intercarpea volaria)—On the volar
(flexor) aspect of the joint there are four ligaments that are not
difficult to demonstrate. (1) From the radius to the radial carpal
bone (scaphoid). (2) From the radius to the intermediate carpal bone
(lunar). (3) From the radial carpal (scaphoid) to the second and third
carpal bones (trapezoid and magnum). (4) From the ulnar carpal
(cuneiform) to the third and fourth carpal (magnum and unciform)
bones.

Interosseous ligaments (ligamenta intercarpea interossea) are attached
to the depressed areas on the opposed surfaces of the bones in the same
row; and two of them connect the bones of the distal 1ow with the
three metacarpals.

The accessory carpal (pisiform) bone is held in position by four
ligaments. (1) A band from the radius. (2) A dorsal ligament
attached to the ulnar carpal (cuneiform) bone. (3) A strong ligament
divided into two limbs and connected with the fourth carpal (unciform)
and fourth metacarpal bone. (4) A volar band attached to the ulnar
carpal (cuneiform) and intermediate carpal (lunar) bones.

THE INTERMETACARPAL ARTICULATION (articulatio intermetacarpea).
—The bases of the three metacarpal bones are provided with small,
smooth areas lubricated by the secretion of the synovial layer of the

carpal joint capsule. ve the, Be higescne and fourth bones are

76 TOPOGRAPHICAL ANATOMY OF

closely united to the third metacarpal by <interosseous ligaments
(ligamenta interossea), the short fibres of which generally become
ossified as age advances.

THE METACARPOPHALANGEAL ARTICULATION (articulatio metacarpo-
phalangea).—The head of the third metacarpal bone possesses an
articular surface composed of two convexities separated by an antero-
posterior ridge. These three parts together form a continuous smooth
area the width of which increases towards the back (volar part) of the
joint. The proximal end of the first phalanx is closely moulded upon
the head of the metacarpal bone. At the back of the joint the two
sesamoid bones (of the first phalanx) together form a continuation of
the articular surface of the first phalanx; but it should be remembered
that, in the horse, there is no direct contact between the sesamoids and
the phalanx.

The joint capsule (capsula articularis) in front of the joint is supported
by and connected with the tendons of the digital extensors. On the
flexor aspect of the joint it is attached to the articular margins of the
third metacarpal and sesamoid bones, and has a pocket-like extension
insinuated between the modified interosseous muscle and the third
metacarpal bone. If the capsule becomes pathologically distended,
the support afforded by tendons and ligaments is so disposed that a
bulging can only take place through the interval between the two
limbs of the interosseous muscle. From the circumstance that the
flexor tendons lie superficial to this interval, it follows that more
marked distension must of necessity make itself manifest on each side
of the limb, between the flexor tendons and the interosseous muscle
immediately proximal to the sesamoid bones.

The lateral and medial collateral ligaments (ligamentum collaterale
laterale: mediale) are stout bands springing from the depressions at the
side of the head of the third metacarpal bone. Each ligament is com-
posed of superficial fibres attached close to the articular margin of
the first phalanx, and a deep and stronger set of fibres inserted
to the sesamoid bones and the angular projection at the base of
the phalanx.

On cleaning the surface of the collateral ligaments, the dissector
will observe that a sheet of oblique fascial fibres covers them and the
joint capsule on the dorsal face of the joint.

An exceedingly dense 2nter-sesamoid) ligament (ligamentum inter-
sesamoideum) binds the two sesamoid bones together, and extends

1 Sesumum [L.], ojoopov (sésamon) [Gr.], sesame (the plants Sesamum indicum
and S. orientale carry oil-yielding seeds). «iéos (eidos) [Gr.], form. The sesamoid
bones of the smaller mammals resemble sesame seeds.

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THE LIMBS OF THE HORSE VW

beyond their proximal limit. The surface of the ligament and the
adjoining surfaces of the sesamoids are covered by a veneer of fibro-
cartilage, and thus form a smooth, oval, groove-like area over which the
deep flexor tendon plays. ,

The lateral and medial sesamoid liyaments (ligamentum sesamoideum
laterale: mediale) are partly covered by the lateral and medial collateral
ligaments and the limbs of the interosseous muscle. When these have
been reflected, the sesamoid ligaments are disclosed as short bands
passing from the sesamoid bones to the third metacarpal bone and the
first phalanx.

The straight sesamoid ligament (ligamentum sesamoideum rectum)
is a strong band springing from the bases of the two sesamoid bones,
and, narrowing somewhat, running down the volar aspect of the first
phalanx to be attached to the complementary cartilage of the second
phalanx between the two limbs of the tendon of the superficial flexor
with which it is intimately connected. The straight ligament must be
cut across, and raised from the oblique ligaments which it partly
covers, and with which some of its fibres are blended.

The oblique sesamoid ligaments (ligamenta sesamoidea obliqua) are
attached to the bases of the sesamoid bones and to the V-shaped line
on the volar surface of the first phalanx.

If the oblique ligaments are reflected, the cruciate sesamord ligaments
(ligamenta sesamoidea cruciata) are brought into view. Each of these
is flattened, and consists of short fibres running from the base of a
sesamoid bone to the back of the proximal part of the first phalanx,
crossing the fibres of the fellow ligament in the middle line of
the digit.

Still deeper ligamentous fibres (ligamenta sesamoidea brevia) may
be revealed on examination of the joint from within. These are few
in number and oblique in direction, and are attached to the sesamoids
and the first phalanx close to the articular margin.

From the character of the bony surfaces and the disposition of
the ligaments, it is evident that the movements in the metacarpo-
phalangeal joint are limited to flexion and extension. The dissector
cannot fail to observe that, when the weight of the body is borne by
the limb, the long axes of the metacarpus and the first phalanx are not
in the same line, and that the condition of the joint might be described
as one of over-extension. He will also notice that a greater degree of
over-extension is prevented by the attachments of the structurally
modified interosseous muscle to the sesamoid bones, and the morpho-
logical extension of the muscle to the first and second phalanges by the

ligaments distal to the sesemaidsyidasdrer the interosseous muscle

78 TOPOGRAPHICAL ANATOMY OF

has taken on both a ligamentous structure and a ligamentous function
—a modification to be associated with the circumstance that the horse
walks on the tip of the third digit.

THE Hoor AND ITS CONTENTS.

Seeing that, without considerable injury to soft structures, it is
well-nigh impossible to remove the hoof from a limb that has been
prepared for dissection as a whole, the dissector should obtain a special
specimen in which the hoof has already been removed.

During the whole of his dissection the student should keep certain
facts clearly in view. The “foot,” as the hoof and the structures
contained therein are commonly comprehensively named, is the distal
part of the digit, and all the component parts thereof have been
modified for two purposes. In the first place, the extremity of the
digit is protected from injury by a dense, horny covering—the hoof
—which is merely a specially thickened portion of the epidermis.
Secondly, the hoof and everything in it (except vessels and nerves)
are capable of absorbing and diminishing shock.

The skeleton of the “foot” consists of part of the second phalanx,
the whole of the third phalanx with its cartilaginous appendages
(ungual cartilages), and the sesamoid bone of the third phalanx.
These, with the elastic digital torus, form a basis to which modified
skin is attached. The skin, here as elsewhere, consists of a highly
vascular corium or dermis and epidermis. The greatly thickened
epidermis forms the hoof or ungula, for which the corium provides
a matrix.

Although the name matrix is applied to the corium in the foot,
this should not lead the student into the error of supposing that
it plays any part, except that of providing nourishment, in the forma-
tion and growth of the hoof. The hoof, being epidermis, grows from
its own deepest layer, or stratum germinativum, in the same manner
as the epidermis in any other region of the body.

The dissector will do well to begin his examination with the
corium or matrix.

THE MATRIX (matrix ungule+)—The highly vascular matrix of the
hoof differs from the corresponding stratum of ordinary skin in several
respects. It contains no sebaceous glands, and sweat glands are
comparatively few and of limited distribution. Its papille are large,
and, in one region, modified so as to form ridges. Subcutaneous

! Matric [L.], the womb, the form or mould in which something is shaped, from

mater, mother. Ungurs [L. nal d by Mi A®
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THE LIMBS OF THE HORSE ; 79

tissue, such as is present beneath the skin in general, is absent,
with the result that the matrix is firmly adherent to the skeleton

Marginal matrix.

Ahn’

ee
{a ee ed
} vee

Coronary matrix.
%

\
Laminar matrix, Outline of hoof.

Fic. 53.—Lateral Aspect of the Matrix of the Hoof.

of the digit. From custom and convenience the matrix is divided
into certain regions.
1. The marginal matrix (margo' matricis ungule) forms a narrow

:\ Solar matrix.

Fie, 54.—Volar Aspect of the Matrix of the Hoof.

band, about 5 mm. wide, at the junction of the matrix and the
ordinary skin of the digit. Each end of the band is continuous with
the matrix covering the digital torus, and its surface is studded
with papille that are smaller than those of the adjacent part of
the matrix.

2. The coronary matrix (corona® matricis ungule) is immediately
adjacent to the foregoing, from which it is separated by a shallow

1 Margo [L.], an edge or border.
2 Corond figikiaewoiyp, /prmebhingerown-like.

80 TOPOGRAPHICAL ANATOMY OF

and narrow groove only. In the form of a bulging band, this part
of the matrix encircles the digit almost completely. Broadest and
most convex at the middle line of the digit, it becomes narrower
and flatter as it is traced to the volar surface, where it ends indefinitely
by merging into the cuneate matrix. The whole surface of the coronary
matrix is beset with large papille, 4 to 5 mm. long, which form a soft,
velvet-like pile.

3. The laminar matrix (latus! matricis ungule) is the most
modified part of the corium of the digit, and covers the dorsal surface
of the third phalanx and a small part of the ungual cartilages. It
is also continued on to the volar aspect of the digit in the form of
two elongated triangular areas. On the laminar matrix papille are
replaced by a large number (about six hundred) of parallel ridges or
laminze which run from the coronary matrix to the edge of the digit,
where each ends in a number of papille similar to those of the
adjoining solar matrix. The lamin are lowest close to the coronary
matrix, from which point they gradually increase in height until
a maximum is reached about the middle of their length. If the
lamine are examined microscopically, it will be seen that the surface
of each carries a considerable number of smaller ridges or secondary
lamine.

4, The solar (volar) matrix (latus volare matricis ungule) covers
the volar surface of the third phalanx, to which it is firmly attached.
Its surface is covered by large papillee some 4 or 5 mm. long.

5. The cuneate matriz (cuneus matricis ungule) is adherent to the
surface of the digital torus. It can be distinguished from the neigh-
bouring solar matrix by its paler colour and the smaller size (1-2 mm.
long) and closer packing of its papille.

THE Hoor (ungula).—The hoof follows the general disposition of the
matrix, upon which it is closely moulded and to which it is firmly
adherent. For descriptive purposes the hoof is artificially divided into
three parts—the wall, the sole, and the “frog.”

1. The wadl (paries ungulz) is that part of the hoof which is visible
when the limb is in a state of rest, and has tapering continuations
(“bars”) inflected on to the volar aspect of the digit. For topographical
reasons it is convenient to divide the wall into “toe” (paries ungule
dorsalis), “quarters” (paries ungule medialis: lateralis), and “heels”
(paries ungule volaris s, plantaris); but this division has no morpho-
logical foundation.

If the wall could be flattened out it would present a crescentic
outline, the horns of the crescent being represented by the abruptly
1 Latus [L.], the side (exposed part).

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THE LIMBS OF THE HORSE 81

inflected parts or “ bars.” The wall, therefore, presents two surfaces and
two borders for consideration. The outer surface is convex from side to
side, and, in the natural condition, is crossed horizontally by a number
of incremental lines that run parallel to each other and parallel to
the proximal border of the hoof. The curve of the convexity is wider
at the lateral than at the medial “quarter,” and the general conformity
of the hoof is different in the thoracic and pelvic limbs.

The angle described by the slope of the wall and the ground plane
is obviously different at the “toe” and the “heels.” It is greater,
ae, the slope is steeper, on the medial than on the lateral aspect, and

Fic. 55.—Outline of the Volar and Plantar Aspects of the Hoof of the Thoracic (I.) and
Pelvic (II.) Limbs.

A.=‘‘toe.” B.=lateral ‘‘ quarter.” ©. =medial ‘ quarter.”

also differs in the hoof of the thoracic and pelvic limbs, as is indicated
in the following averages given by Lungwitz :—

Thoracic limb. Pelvie limb.
“Toe” . : 47°26° 54-1°
Lateral “heel” 101°37° 961°
Medial “ heel” . 101°57° 96°5°

It must be borne in mind that these figures do not necessarily
apply to any particular specimen. There is a notable variation in the
general form and angles of the hoof of apparently perfectly normal feet.

The length of the wall, 2.2. the distance between the two borders,
at the “toe,” “quarter,” and “heel,” may be indicated by the ratios
3:2:1 for the hoof of the thoracic limb, and 2:14:1 for the hoof of
the pelvic limb.

In the neighbourhood of the coronet the outer surface of the hoof
is covered by a thin layer of very elastic horn (limbus ungule)—con-
nected with the marginal matrix—polished and glistening when dry,
but whitish, swollen, and fibrous when moist.

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82 TOPOGRAPHICAL ANATOMY OF

The inner surface of the wall is laminated in conformity with the
lamination of that part of the matrix to which it is applied. In the
natural state the lamin (cristee ungule) of the hoof occupy the
intervals between the laminze of the matrix. Though to the naked
eye the lamin appear simple, under magnification each surface of
every lamina is found to carry secondary lamin which interdigitate
with corresponding secondary ridges of the laminar matrix.

The coronary border (margo occultus) of the wall gradually thins
away, because of the presence of a groove into which the coronary

Coronary groove,
‘

- ....Limbus ungulie
(periople).

Coronary border of z

the wall. .. "
\ -- Laminee of wall.

Surface view
of lamina.

We

Layer of pale
horn (‘‘ white
line’’).

Limbus ungulee, _

Fic. 56.—Inner Surface of the Hoof.

matrix is received. The groove is closely punctated with small holes
into which the papille of the matrix are received.

The free border (margo liber) in the unshod animal comes into
contact with the ground, and has a more or less ragged appearance due

“to destruction of the hoof by friction and attrition. The thickness of
the border is greatest at the “toe” (about 10 mm.), and gradually
becomes less towards the “heel,” where it is barely half that of the
“toe.” The free border is connected with the margin of the sole of
the hoof by a definite line of pale and relatively soft horn.

The inflected part (pars inflecta, “bar”) of the wall forms a
gradually tapering ridge on the volar aspect of the digit, between the
sole and the cuneus (“frog”).

2. The sole (solea ungulz) is a strong plate of horny tissue applied
to the solar (volar) matrix, and indented by a deep triangular notch
into which are fitted the inflected parts of the wall and the “ frog.”
Speaking generally, therefore, the sole may be said to have a crescentic

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THE LIMBS OF THE HORSE 83

oO

outline, and may be divided into a body and two rami or cornua. Its
convex or greater border is connected with the wall by the compara-
tively soft and elastic layer of horn to which reference is made above.

The free surface of the sole is more or less concave, the degree of
concavity depending in some measure on the breed of the animal; but
the hollow always contains flakes of horn that are in process of being
shed. The inner surface is pitted with small holes for the reception of
the papillee of the solar matrix, and is convex in form with the highest
point of the dome close to the apex of the “frog.” The curvature of
the sole is greater in the pelvic than in the thoracic limb.

Wall. ___

ee |

ny
‘a Mig
~S ek

Layer of pale horn_ eN _ Apex of cuneus.
uviting wall and sole. 6

Inflected part of
wall (“bar”),

Cruro-parietal groove. —- _-Crus oftcuneus.

Intercrural groove. ——— th

Fic. 57.—Volar Aspect of the Hoof.

3. The cuneus? or “ frog” (cuneus ungule) may be best described as
having four surfaces. The inner or upper surface presents two BrOoveN,
converging and meeting in front, with an abruptly sloping projection:
or spine (spina cunei ungule) between them. The whole of this
surface is pitted with minute holes into which the papille of the
cuneate matrix are received.

The free surface of the cuneus is triangular in form, and co
two ridges or crura (crura cunei ungule) that converge aay meet in
front at the apex (apex cunei ungule). Between the Crore a5 uhe deep
intercrural groove (sulcus intercruralis) corresponding in porn: x
the spine on the upper surface, and, therefore, deepest posteriorly, with
a rapidly shelving anterior part. The medial and lateral surfaces are
partly connected with the sole and the inflected parts of the wall, and
partly free where they help to bound the cruro-parietal grooves (sulci

J, a wedge.
Digites By Maosone

.

84 TOPOGRAPHICAL ANATOMY OF

cruro-parietales). The base of the cuneus is posterior and forms
two eminences separated from each other by a continuation of the
intercrural groove.

The dissector should make sections of the hoof by means of a saw
in order that he may compare the thickness of the different parts. The
same method will permit him to determine the strata of the wall.

Three layers can be distinguished in the wall. (1) The most super-
ficial is the thin, incomplete, glistening layer already described as
being present at the limbus ungule. Because of its density and glassy
or varnish-like appearance it has been called the vitreous layer.
(2) The second layer forms the dense and hard portion of the wall,
which is only little affected by moisture and offers great resistance to
the. knife. (3) The innermost layer is much softer and paler, and is
composed of the horny laminz that fit between the soft laminz of
the matrix. The ridges are low at the edge of the coronary groove,
but gradually increase in height as they proceed distalwards. They
terminate in the white line between the wall and the sole, where they
are mixed with horny tubules connected with the terminal papille of
the laminz of the matrix.

The thickness of the wall varies considerably in different individuals,
and is not the same in all parts of the wall of the same hoof. The
difference in different regions has been expressed by saying that the
thickness of the wall at the “toe,” “quarters,” and “heels” is as
4:3:2 in the hoof of the thoracic limb, and as 3:24:2 in the hoof
of the pelvic limb.

The thickness of the sole may range from 7 to 10 mm.; while that
of the “frog” is from 10 to 15 mm.

The relative density and rigidity of the hoof in different regions are
of moment from the physiological point of view. The oldest horn,
ie. that at the extreme end of the “toe,” is most rigid and least
yielding; whereas pliability, though nowhere very great, increases in
all parts of the wall as the coronary border is approached. The horn
of the sole is less rigid than that of the wall, and the “ frog” is
composed of the softest and most pliable horn of the whole digit. The
presence of a layer of comparatively flexible horn at the junction of
the sole and the wall permits a certain amount of movement at this
place.

THE DIGITAL TORUS (torus digitalis)—The digital torus! is a
pyramidal mass of fibrous and elastic tissue placed between the “frog”
and the tendon of the deep flexor muscle. Each side of the base of
the torus is intimately connected with one of the cartilages of the

! Torus [L.], a bulge, protuberance, or prominence.

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THE LIMBS OF THE HORSE 85

third phalanx. Its deep (dorsal) surface slopes from above downwards
and forwards in conformity with the obliquity of the deep flexor
tendon close to its insertion. Between the torus and the tendon

M. interosseus. +—

1 ep

=
M. flexor digitorum _ H
sublimis.

Sesamoid bone. .

M_ flexor digitorum _
profundus.

Ereot,” 2

Ligg. sesamoidea obliyua. -

Lig. sesamoideum rectum, ____ s\ WN
AN
Ds es eerie EN
\ Second phalanx.

--- 8%,

a ere Third phalanx,
Stelios Wall of hoof.
: -—-—- Laminar matrix.
SUAAN :

+ Terminal arch of
digital vessels.

Sole.

NN

SN)

Cuneus (‘‘ frog”). Ss |
(

Cuneate matrix. Digital torus. Solar matrix.
Fie. 58.—Longitudinal Section of the Digit.

land 1’, 2 and 2’, 3 and 3’.=Joint capsules of the metacarpo-phalangeal, proximal
interphalangeal, and distal interphalangeal articulations respectively. 4.=Synovial sheath
of the flexor tendons. 5,=Synovial sheath of the deep flexor tendon.

there is a fascial sheet that is proximally connected with the first
phalanx,

The more superficial (volar) surface of the torus is almost horizontal
when the weight of the body rests on the limb. It is covered by the
cuneate part of the matrix, and upon this surface the cuneus (“frog”)
is moulded. Two diverging ridges bound a cleft into which the spine
of the “frog” fits. The ridges blend in front, and behind they end in
two rounded eminences that constitute the base or bulbs of the torus.

The apex of the torus_is firmly adherent to the insertion of the deep
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86 TOPOGRAPHICAL ANATOMY OF

flexor tendon and the periosteum of the third phalanx immediately in
front of the semilunar crest.
The structure of the torus is not uniform throughout. Towards the

es

Fic. 59 —Key Outline to Indicate the Position of the Sections Illustrated in Figs. 60 and 61.

apex it 1s composed almost entirely of white fibrous tissue of some
density; but towards the base, not only is the tissue looser, but it

M. extensor digitorum communis.

Lig. collaterale mediale. ._ _- Second phalanx.

Cartilage of third
Sesamoid (navicular),-~ phalanx.

-Wall of hoof.

A. digitalis volaris. Volar branch of

n. volaris lateralis

M. flexor digitorum --
profundus,

Digital torus.-~~

Fie. 60.—Transverse Section of the Foot at the Level Indicated by Line A in Fig. 59.

contains a considerable amount of fat. The presence in it of moditied
skin-glands seems to indicate that the torus is subcutaneous tissue

specially thickened and structurally adapted to absorb shock.
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THE LIMBS OF THE HORSE 87

Dissection.—The digital torus should be removed entirely, and the
two surfaces of the ungual cartilages exposed and cleaned. In conduct-
ing this operation the dissector must preserve the arteries and nerves of
the region, and, at the same time, observe the venous plexuses from
which the digital veins take their origin.

THE CARTILAGES OF THE THIRD PHALANX (cartilagines phalangis
tertia)— These, the ungual cartilages as they are sometimes called, are
attached to the angles of the third phalanx, and thus, in a manner,
increase the area to which the matrix and other soft parts of the digit
are adherent. In the young animal the greater part of the cartilage
composing them is of the hyaline variety ; but as age advances a fibrous

Wall of hoof.
\

Laminar matrix. _

Terminal arch of
a. digitalis.

Digital torus.

Inflected part _
of wall (‘‘bar’”’).

Cuneus (‘‘ frog”).

Fic. 61.—Transverse Section of the Foot at the Level Indicated by Line B in Fig. 59.

development ensues, beginning at the periphery and gradually spreading
inwards, until almost the whole structure is converted into fibro-
cartilage. Pathologically a considerable extent of the cartilage may be
converted into bone; and some amount of bone formation in that part
of the cartilage next to the third phalanx may be regarded as the
natural accompaniment of age.

The superficial surface of each cartilage is convex and smooth and
covered with a venous plexus from which vessels pierce the cartilage
to gain its deeper face. It is important to note that, while the lower
part of this surface gives attachment to matrix and is therefore
enclosed within the hoof, the upper part is beyond the border of the
hoof and can consequently be felt through the skin.

The deep surface of each cartilage is concave and intimately

t to the digital tor osteriorly, while anteriorly it covers
pee Ae nee Bigitized by Microsof® -

88 TOPOGRAPHICAL ANATOMY OF

part of the joint between the second and third phalanges. The upper
(proximal) border is convex and thin. The lower (distal) border is
thicker and connected with the third phalanx and the digital torus.
Short ligamentous fibres pass between the contiguous edges of the

cartilage and phalanx.
The anterior end of each cartilage reaches the edge of the tendon of

Third metacarpal bone.

Sesamoid. _

First phalanx.

a II. WN oe pee Second phalanx.

Cartilage of third phalanx, _
Line of border of hoof. _
Sesamoid. --_

Third phalanx.

—

Fic. 62.—Lateral Aspect of the Phalanges and the Cartilage of the Third Phalanx, to show
the Position of the Joint and Cartilage relative to the Surface of the Limb and the
Border of the Hoof.

the common extensor muscle, and blends with the collateral ligament
of the joint between the second and third phalanges. The posterior
end forms a blunt in-curved angle reaching a considerable distance
beyond the angle of the third phalanx.

Ligamentous bands should be defined and demonstrated as con-
necting the cartilages to the first and second phalanges.

A short ligament passes from the anterior end of each cartilage to
the anterior (dorsal) surface of the second phalanx. An ill-defined
elastic band stretches from the deep surface of each cartilage to the
side of the distal end of the first phalanx. In addition, a short, strong
ligament connects the extremity of the sesamoid bone with the nearest

point on the neighbouring cartilage; and a band connects the anterior
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THE LIMBS OF THE HORSE 89

part of each cartilage with the common extensor tendon near its
insertion.

AA. DIGITALES VOLARES.—During the dissection of the limb in
general some of the branches of the volar digital arteries were examined,
but some could not be followed until the contents of the hoof had been
dissected.

1. The dorsal and 2. volar branches of the first phalanx have been
dissected. The following remain for examination :—

3. Aa. torice phalangis tertie—These leave the digital arteries
about the level of the proximal border of the cartilages of the third
phalanx, and are distributed mainly on the surface (in the matrix) of
the torus.

4. Rami dorsales phalangis secundw.—The dorsal rami of the second
phalanx run round the digit proximal to the distal interphalangeal
joint and under cover of the cartilages of the third phalanx and the
common extensor tendon.

5. Rami volares phalangis seewnde.—The volar rami arise opposite
the foregoing and, by anastomosis, form a transverse connection
between the two digital arteries just proximal to the sesamoid bone.

6. Aa. coronales phalangis tértic.—The coronal arteries are incon-
stant in their origin. They frequently arise from the dorsal rami of
the second phalanx. Whatever their origin, the arteries supply the
coronary matrix.

7. Aa. dorsales phalangis tertice.—The dorsal arteries of the third
phalanx pass through the notch or foramen at the angle of the bone
and are distributed in the laminar matrix.

8. The terminal branch of each digital artery enters the volar
foramen of the third phalanx and, in the semilunar canal in the interior
of the bone, anastomoses with its fellow vessel to form the terminal
arch (arcus terminalis), from which numerous small arteries arise and
pierce the foramina on the dorsal surface and at the distal border of
the phalanx.

The insertion of the deep flexor tendon may now be examined.
The tendon widens as it crosses the surface of the sesamoid bone—
where it is provided with a synovial (mucous) sheath—and is inserted
to the flexor area of the third phalanx.

THE PROXIMAL INTERPHALANGEAL ARTICULATION (articulatio phalangis
secunde).—The opposed surfaces of the first and second phalanges are
accurately adapted to each other. This, and the presence of strong
collateral ligaments, limits the movement to flexion and extension.
The articular area of the second phalanx is extended posteriorly

by a aC ae | ee off®

90 TOPOGRAPHICAL ANATOMY OF

The joint capsule (capsula articularis) has the customary attachment
to the articular margins of the two bones that enter into the forma-
tion of the joint. The dorsal part of the capsule is the strongest, and
is supported by the tendon of the common extensor muscle. On each
side it ig connected with a collateral ligament; and behind, where it is
thin, the straight sesamoidean ligament, the volar ligaments, and the
insertion of the superficial flexor tendon afford support.

Fourth metacarpal bone. - ++ —.--—< -,M. extensor digitorum communis.

+---- --~-M. extensor digiti quinti.

M. interosseus.

+--—-~-,Third metacarpal boue.
Lig. sesamoideum laterale. ---

Lig. sesamoideum rectum.

Lig. sesamoideum obliquum. - -

Ligamenta volaria. —.-{"~ Ni \
eas yh

M. flexor digitorum sublimis, -~—----
Lig. collaterale laterale.__ -- ~~ -

Lig. collaterale
laterale.

_-.Third phalanx.

Fic. 68.—The Tendons and Ligaments of the Lateral Aspect of the Digit.

The short, but very strong, collateral ligaments (ligamentum
collaterale mediale: laterale) are attached to the sides of the distal
extremity of the first phalanx and to the adjoining parts of the
second phalanx.

There are four volar ligaments (ligamenta volaria), all of which arise
from the posterior (volar) surface of the first phalanx, about the middle
of this bone and close to the attachment of the oblique sesamoidean
ligament. The two central ligaments join the glenoidal fibro-cartilage
of the second phalanx, where they blend with the straight sesamoidean
ligament and the insertion of the superficial fexor tendon. The most
medial and most lateral of the four ligaments are attached to the
proximal end of the second phalanx. :

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THE LIMBS OF THE HORSE 91

THE DISTAL INTERPHALANGEAL ARTICULATION (articulatio phalangis
tertia).—The joint between the second and third phalanges is one in
which movement is limited to flexion and extension. Movement,
moreover, is not very free owing to the inclusion of the joint in the
hoof. The dissector will observe that the articular surface of the third
phalanx is not, in itself, sufficiently extensive to accommodate the

M. interosseus, ...__ _--. Third metacarpal bone.

Second metacarpal bone, ---~- ee a ee Fourth metacarpal bone.

Lig. intersesamoideum. .

=- Lig. sesamoideum laterale.

..Lig. sesamoideum obliquum.

Lig. sesamoideum rectum,

Ligamenta volaria.

_--M. flexor digitorum sublimis.
Glenoidal lip. ._

Lig. collaterale mediale.

4 __Lig. sesamoideum collaterale
Jaterale.

Sesamoid.
Lig. phalangosesamoideum. 2
3} Third phalanx.

Fie. 64.—Ligaments of the Volar (Posterior) Aspect of the Digit.

whole of the distal end of the second phalanx. The sesamoid bone
completes the articular cavity. Between the ligamentous border of the
sesamoid and the immediately adjacent part of the third phalanx, short,
but strong, fibres form a phalango-sesamoidean ligament (ligamentum
phalangosesamoideum) that, while permitting a certain measure of
movement, retains the sesamoid firmly in position.

The joint capsule (capsula articularis) is attached to the articular
margin of the three bones which enter into the formation of the joint.
In front (dorsal) it is intimately connected with the common extensor
tendon and the ie cps pL eter a the joint the capsule is

92 TOPOGRAPHICAL ANATOMY OF

thinner and more roomy, and extends for some distance between the
second phalanx and the deep flexor tendon. For surgical reasons it is
important to note that there is a small diverticulum of the joint
capsule, in contact with the deep surface of each cartilage of the third
phalanx immediately behind a collateral ligament.

The stout collateral ligaments (ligamentum collaterale mediale:
laterale) pass from the distal end of the second phalanx to the
depressions on each side of the extensor process of the third
phalanx.

Strong, but elastic, collateral sesamoidean ligaments (ligamentum
sesamoideum collaterale mediale: laterale) arise mainly from the
borders of the second phalanx, but some fibres (blended with the
collateral ligament of the preceding joint) can be traced to the distal
end of the first phalanx. The collateral ligaments end on the upper
(proximal) border of the sesamoid bone; some fibres being attached
to the deep face of the cartilage of the third phalanx and to the angle
of the phalanx itself,

Digitized by Microsoft®

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Digitized by Microsoft®

94

NERVE AND BLOOD

Nerve Supply.
Accessory i |

6th and 7th cervical .

Thoraco-dorsal .

From brachial plexus

Long thoracic.

Suprascapular

Axillary

Subscapular

Musculo-cutaneous

Radial

TOPOGRAPHICAL ANATOMY

OF

SUPPLY OF THE MUSCLES oF THE THORACIC LIMB.

M. trapezius.

Mm. rhomboidei.
M. latissimus dorsi.

Mm. pectorales.

. serratus ventralis.

. supraspinatus.
[. infraspinatus.
. deltoideus.

. teres minor.

. teres major.

. capsularis.

. subscapularis.
. coraco-brachialis.

M. biceps brachii.

a brachialis.
M. tensor fascize anti-

brachii.

M. triceps brachii.

M. anconeus.

M. extensor
radialis.

carpi

M. extensor digit-
orum communis.

M. extensor digiti
quinti.

M. extensor

carpi
ulnaris.

M. abductor pollicis.
Digitized by Mic.

Blood Supply.
Deep cervical, and intercostals.

Deep cervical, and transverse artery
of the neck.

Subscapular, intercostals, and
lumbars.
Internal and external thoracic,

intercostals, transverse scapular,
anterior circumflex, and thoraco-
acromial.

Deep cervical, transverse artery of
the neck, vertebral, and inter-
costals.

Posterior circumflex, circumflex
scapular, and thoraco-acromial.

Subscapular, and circuniflex scapular.

Subscapular, and posterior circum-
flex.

Subscapular, and circumflex scapular.

Subscapular, and thoraco-dorsal.

Posterior circumflex.

Subseapular, circumflex
and thoraco-acromial.

scapular,

Anterior circumflex, and thoraco-
acromial.
and

Brachial, collateral radial,

anterior circumflex.

Brachial, collateral radial, and deep
brachial.

Subscapular, collateral ulnar, and
deep brachial.

Subscapular, deep brachial, posterior
circumflex, and collateral ulnar.

Deep brachial.

Collateral radial, and deep brachial.

Collateral radial, and dorsal inter-
osseous.

Dorsal interosseous, and collateral
radial.

Common _ interosseous, collateral

ulnar, and median.

Dorsal interosseous, and collateral
radial

rosoft®

THE LIMBS OF

THE HORSE 95

Nerve Supply.
Median

Ulnar and median

M. flexor carpi
radialis.

(M. flexor carpi
ulnaris.

M. flexor digitorum
sublimis.

M. flexor digitorum
profundus.

Mm. lumbricales.

Mm. interossei.

Llood Supply.
Median.

Collateral ulnar and median.

Median.

Collateral ulnar, median, and com-
nion interosseous.

Volar metacarpals.

Volar inetacarpals.

Digitized by Microsoft®

PELVIC LIMB.

Ir is convenient to begin the dissection of the pelvic limb with the
examination of the structures on the medial aspect of the thigh; but
if the subject is a male, the dissector of the limb cannot start his work
until the external genital organs have been examined by the dissectors
of the abdomen.

Comparatively little of the anatomy of the inner aspect of the thigh
can be determined before reflexion of the skin. The position of the
saphenous vein may be visible, but only if it happens to be filled with
blood. If it is possible to follow the vein with the eye, it will be
noted that it disappears before actually reaching the groin. Palpation
at the point of disappearance discloses a groove formed by the adjacent
margins of two muscles, the gracilis and sartorius; and deep palpation
of the groove should permit the dissector to determine the presence of
the deep inguinal lymph glands.

Dissection.—In the male an incision should be made from the proximal
third of the leg to the incision already made by those who have dissected
the external genital organs. In the female a second incision along the
line of the pelvic symphysis will be necessary. It must be remembered
that the skin of this region is thin, and that, therefore, the incisions
must not be deep. Two triangular flaps of skin are now turned aside
from the underlying structures.

The dissector must now isolate the saphenous vein, artery, and nerve
and demonstrate the fascia of the region and its connection with the
wall of the abdomen. The surface of the gracilis and sartorius must

then be cleaned.

A. SAPHENA: V. SAPHENA: N. SAPHENUS.—The saphenous! artery,
vein, and nerve appear from the narrow cleft between the gracilis and
sartorius muscles, and run down the medial surface of the thigh into
the leg, where their subsequent course will be followed in a later
dissection.

The artery lies in front of the vein, and, at the point where they
first become superficial, the nerve is in front of the artery. Before its

1 Saphena [L.], capyvys (saphéenés) [Gr.], manifest ; from the prominence of the
vein in the living animal.

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THE LIMBS OF THE HORSE 97

appearance at the present stage of the dissection the nerve has already
divided into several (3 or 4) branches, which separate as they proceed
down the thigh.

Not infrequently the saphenous vein, instead of sinking into the

A. <ter i
pudenda externa. Veins of mammary gland.

ay,
‘

Nau
Py eo , a
io Qa oe << S S
= a my” hy i] My
; ee wt i - i Se eS =

Deep inguinal lymph = ge \ \ WW \

glands. ae Si Y Le _— M. pectineus.
M. tensor fascize late. ceri x2 \ Hf yj

_M. semimembranosus.

x \\
A. circunflexa ilium Wy
_profunda. ea | \\\ a
N. cutaneus femoris - QQ \\\

lateralis. NN)

al \K\
Subiliae 1 1 “coh
ubiliac lymph glands.

M. gracilis.

A. femoralis.

M. sartorius --- -
__ Saphenous vessels
F and nerve.

M. rectus femoris._-_-____

M. vastus medialis

ti
\
wy

us

LS

Fic. 65.—Superficial Dissection of the Medial Aspect of the Thigh. (Female.)

narrow cleft between the sartorius and the gracilis, continues its super-
ficial course and ends by joining the external pudendal vein.

M. craciuis.—The gracilis! is a broad, flat muscle covering the
greater part of the medial aspect of the thigh. Its origin is from the
pelvic symphysis, the tendon of insertion of the straight abdominal
muscle where this is attached to the pecten of the pubis, and the accessory
ligament of the hip joint. Some fibres arise from a tendinous septum

1 Graciles [L.], thin, sleahenee By Rhy Bs BRS es of the human muscle.
7

98 TOPOGRAPHICAL ANATOMY OF

that separates the muscles of the two limbs. At the distal part of the
thigh the fleshy portion of the muscle merges into an aponeurotic tendon,
which is connected with a similar tendon of the sartorius. The inser-
tion of the muscle is to the most medial of the three patellar ligaments,
the medial surface of the tibia, and the deep fascia of the leg.
M. sarrorius.—The narrow and comparatively thin sartorius*

muscle takes its origin from the iliac fascia and the tendon of the psoas
minor muscle. The origin, therefore, cannot be determined at the
present stage of the dissection. In the groin, the muscle appears under
the inguinal ligament (of Poupart), and thence follows the anterior
border of the gracilis. The insertion of its thin tendon is to the most
medial of the patellar ligaments in common with part of the insertion
of the gracilis.

Dissection.—Reflect the gracilis and sartorius muscles by cutting
across them about the middle of their length. In turning aside the
proximal portion of each muscle the nerve of supply should be secured.
The nerve to the gracilis is derived from the obturator; that of the
sartorius is a branch of the saphenous.

The elongated group of deep inguinal lymph glands (lymphoglandulee
inguinales profunde), which occupy the space between the sartorius
and pectineus muscles and overlie the femoral vessels, must be examined
and then removed.

The structures now to be dissected are the femoral vessels in the

greater part of their course, and the medial vastus, pectineus, adductor,
and semimembranosus muscles.

, M. vastus MEDIALIS.—The medial vastus” is one of a group of four
powerful muscles clothing the anterior surface of the femur known
‘collectively as the quadriceps muscle (m. quadriceps femoris). The
origin of the medial vastus is from the neck and nearly the whole of
the medial surface of the femur. Its insertion is to the patella and its
complementary cartilage.

M. PectinEus.—The rounded tapering pectineus? muscle lies medial
to the vastus and largely under cover of the gracilis. Its origin is from
the pecten of the pubis, the tendinous pubic attachment of the straight
abdominal muscle, and the accessory ligament of the hip joint. The
narrow tendinous insertion is to a muscular impression close to the
nutrient foramen of the femur.

M. appuctor.—The strong adductor is entirely covered by the
gracilis. The origin of the muscle is from an elongated area on the
ventral surface of the pubis and ischium, close to the pelvic symphysis,

' Sartor (L.], a tailor. The muscle is said to be well developed in tailors, owing
to the special attitude assumed when sewing.

2 Vastus (L.], great, vast, immense.

5 Pecten [I.], a comb ; from the connection of the muscle with the pecten of the
pubis.

Digitized by Microsoft®

THE LIMBS OF THE HORSE 99

some fibres in addition springing from the tendinous origin of the
gracilis, Its insertion is to the posterior surface of the femur, from
near the third trochanter to the medial epicondyle, and to the medial
collateral ligament of the femoro-tibial joint. Sometimes fibres are

N. obturatorius. Obturator vessels.
: é M., obturator internus.

Symphysis of ischium.
J

A. iliaca externa.

V.iliaca externa.

Truncus pudendo-
epigastricus.

N. femoralis.
A. profunda femoris.

i V. pudenda externa.

Depression for root of
penis.

—-M. pectineus.

Lig. accessorium.
Anteriorfemoral vessels.

Vb
YY 4
N. saphenus. WILY Mp fs < Y-.Nerve to m. gracilis.
Femoralarteryand vein. _ yy / yy,

A.saphena. __

fl ig i’
y,
IN

M. rectus femoris.

M, vastus medialis.

A. genu suprema.

M. semiitendinosus,

M. gastrocnemius.

~ Ns \ ——-M. popliteus.

yf) Uy

Fic. 66.—Dissection of the Medial Aspect of the Thigh after Removal of the Sartorius
and Gracilis Muscles. (Male. )

continued to the tibia itself. Distal to the middle of the femur, ie.
immediately distal to the insertion of the pectineus, the insertion is
pierced by the femoral vessels.

Occasionally the most proximal part of the muscle can be isolated
from the rest. If this portion is regarded as equivalent to the m. adductor
longus of the human body, the rest of the muscle must be considered as

representing the m. ad@jcton duets aiicraxopdductor magnus. So seldom

°

100 TOPOGRAPHICAL ANATOMY OF

is a satisfactory separation possible in the horse that it appears
unnecessary to describe the muscle as other than a single structure.

M. sEMIMEMBRANOSUS.—This is the largest and most posterior of
the muscles at present being examined. Its main origin is from the
ventral and medial part of the sciatic tuber and the ventral surface of
the ischium adjoining the sciatic arch. A slenderer head, arising from

A. profunda femoris.
Lig. accessorium.
V. pudenda externa.
: M. obturator externus.
: Symphysis of ischium.
/

V. iliaca exteran, ——~—-—---
A. iliaca externa, ———--~--

Truncus pudendoepigastricus, - -- — ———

A
N. femoralis. —— eee 6S :
se ih

i \TAN Nt ae g Z a x ai
Auterior femoral vessels,-—-~—~—-- hb 1! , oe Z a N tom. gracilis.

Ge Al eee P te WM. iliopsoas.
Femoral artery and vein. -. Z { Hs A VY if

M. rectus femoris. .—
A. saphena. _____

M, pectineus, ----

M. vastus medialis, ___ SL 9 2 Hy i'\'\\ Wy = —.N. peronzus communis.

A. genu suprema, _ y

Posterior femoral vessels.

y

| — _M. gastrocnemius.

= M. semitendinosus.
M. adductor.

Wig 77
qi Wragg
M. semimembranosus. ..\4 3

M. popliteus.

Fic. 67.—Deep Dissection of the Medial Aspect of the Thigh.

the transverse process of second (possibly also the first) coccygeal
vertebra and the edge of the sacro-tuberous ligament, passes over the
sciatic tuber, beyond which it joins the larger main head. A synovial
bursa may intervene between the muscle and the tuber.

The short tendon of insertion of the semimembranous is attached to
the medial epicondyle of the femur and the medial collateral ligament
of the femoro-tibial joint, along with part of the insertion of the
adductor, while beyond this it becomes continuous with the fascia of
the leg.

The term femoral triangle (trigonum femorale) is appliel to a space
Digitized by Microsoft® ‘

THE LIMBS OF THE HORSE 101

bounded by the inguinal ligament of Poupart, which forms its base,
and the sartorius and pectineus muscles. The narrow apex of the
triangle is distal. Owing to the extensive development of the gracilis
muscle in the horse the triangle is not completely exposed until this
muscle has been reflected. The triangle contains the deep inguinal
lymph glands, the femoral vessels, and the saphenous nerve.

A. FEMORALIS: V. FEMORALIS.—The femoral artery is the direct
continuation of the external iliac, the arbitrary dividing line between
the two vessels being taken as occurring on a level with the pecten of
the pubis. From its origin the femoral artery, so far as it is at present
visible, pursues a course in the thigh that is represented by a line
crossing the long axis of the femur very obliquely and extending from
the border of the ilium, where this bone enters into the formation of
the acetabulum, to the vascular groove that indents the medial lip of
the linea aspera. The artery lies at first on the terminal part of the
ilio-psoas muscle, and later on the medial vastus muscle. It is covered
anteriorly by the sartorius, and posteriorly it is in contact with the
pectineus and adductor muscles. While in the femoral triangle the
artery is related medially to the gracilis. The termination of the vessel,
after it has pierced the insertion of the adductor muscle, cannot be seen
at present, but will be revealed at the next stage of the dissection.

The femoral vein is a close satellite of the artery, lateral and slightly
posterior to which it lies in the whole of its course except where the
two vessels are disappearing beneath the inguinal hgament of Poupart.
At this point the vein is wholly posterior to the artery.

The following are branches of the femoralartery. The vein receives
corresponding tributaries.

(1) Rami musculares—Branches of varying size are furnished by
the femoral artery to the muscles in the neighbourhood.

(2) A. femoris anterior—The anterior femoral artery leaves the
parent vessel close to the inguinal ligament, and follows an oblique
course, underneath the sartorius muscle, to enter the cleft between
the medial vastus and rectus femoris muscles, with the supply of which
it is mainly concerned.

(3) A. saphena—The thin saphenous artery has already been
examined as it lies under the skin of the thigh. Its origin within the
femoral triangle is now disclosed.

(4) A. genu suprema.—tThe articular branch of the femoral is small,
and follows the groove of contact between the medial vastus and
adductor muscles, to terminate on the medial aspect of the femoro-
tibial joint.

: Frangoisyoyparts Byenppnatopyst, 1661-1709.

A. poplitea

TOPOGRAPHICAL ANATOMY OF

A, iliaca externa. ._ A. obturatoria.

ae i i teea

—Trancus pudendoepigastricus.

A. femoris anterior. _
ces

A. femoralis.. . __ _

A. genu’suprema,- — —
An

. A.saphena.

so)

A. tibialis anterior

A. tarsea lateralis. .

‘AL dorsalis pedis. -- _-\\

A tarsea perforans. - ~~

re -y at

Ametatarsea dorsalis lateralis. .— -

Aa, metatarsez plantares.__ _

Fic. 68.—Diagram of the Arteries of the Pelvi

Digitized by Microsoft®

a bree Om

a pen ee Vi 4 ’ ZA __—— A. femoris profu
4 C335 Lp 9 f thie

pty

A. femoris posterior.
7 ar

wee

A. tibialis posterior.

— Aa. plantares.

[ite 4,

po.

¢ Limb.

pond, aa

nda

cme

ae. .

et

Common trunk formed by vv. femoris
profunda and pudenda externa, 7

V. poplitea

THE LIMBS OF THE HORSE

V. obturatoria.

V, iliaca externa, — --

VY. femoris anterior. - onef

Y. femoralis.

V. saphena. _

———Y. tarsearecurrens.

V. tibialis anterior. —— ——-VY. recurrens tibialis.

,

q wm — V. metarsea
7 ears 2 plantaris
V. metatarsea plantaris profunda, -———_] superficialis

1 lth lateralis.
Me

Fic. 69.—Diagram of the Veins of the Pelvic Limb.

Digitized by Microsoft®

104 TOPOGRAPHICAL ANATOMY OF

(5) A. nutritia femoris—The nutrient artery of the femur leaves
the femoral as this vessel pierces the adductor muscle.

(6) A. femoris posterior—At the present stage of the dissection
the posterior femoral artery is hidden by the semimembranosus muscle.
It will be exposed shortly.

N. FEMORALIS.—The femoral nerve arises from the lumbar plexus.
Its termination alone is demonstrable at present, and will be found
between the deep face of the sartorius and the ilio-psoas. It accom-
panies the anterior femoral artery as this vessel sinks between the
medial vastus and the rectus femoris muscles, and is the nerve of
supply to the quadriceps mass of muscles.

The origin of the saphenous nerve, one of the branches of the
femoral, will be found underneath the sartorius muscle, and the nerve
can be followed along the anterior border of the femoral artery. The
superficial part of its course has already been examined, so far as it
lies in the thigh.

Dissection.—The pectineus, adductor, and semimembranosus muscles
must now be cut across about their middle and the cut ends turned
aside. In reflecting the pectineus and adductor, the dissector must
note the branches of the obturator nerve that supply them. He must
also look for branches from the sciatic nerve to the semimembranosus
muscle.

Ji the subject has been well preserved, it is possible that the
adductor and semimembranosus muscles may be too stiff to permit the
dissection to be conducted with ease. In this case the middle part of
each muscle should be cut away entirely.

The distal part of the femoral artery is now exposed as it lies
between the femur on the one hand and the adductor and semimem-
branosus muscles on the other.

On the deep face of the biceps muscle the tibial and common
peroneal nerves will be observed ; but their full consideration is better
postponed until an examination of the thigh is made from the lateral
aspect, when their origin from the sciatic nerve can be determined.

The other structures now exposed are branches of the obturator
nerve and vessels, the deep femoral artery and its companion vein,
the insertion of the ilio-psoas muscle, and the external obturator and
quadratus femoris muscles.

M. QUADRATUS FEMORIS.— The quadrate! muscle is slender and
narrow, and has the outline of an elongated triangle. From its origin
near the centre of the ventral surface of the body of the ischium the
muscle passes obliquely to its insertion into the proximal third of the
posterior surface of the femur near the lesser trochanter.

M. OBTURATOR EXTERNUS.—The triangular or fan-shaped external
obturator® muscle arises from the ventral surface of the ischium and
pubis in the neighbourhood of the obturator foramen. The converging,

1 Quadratus [L.], squared or square ; from the outline of the human muscle.
2 Obturo [L.], to stop up, to close.
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THE LIMBS OF THE HORSE 105

coarse fibres of the muscle cover the foramen, and are inserted into the
trochanteric fossa.

M. IL10-psoas.—The insertion of the ilio-psoas! muscle into the
lesser trochanter of the femur is now exposed. Its components (m. psoas
major and m. aiaeus), and their origins, will be examined in the dis-
section of the abdomen and pelvis.

N. opturatorius.—Two branches of the obturator nerve pierce the
external obturator muscle. The cranial branch furnishes nerves to the

M. rectus femoris. M. pectineus.

-—M. gracilis.

.—M. obturator externus.

Mm, gemelli..----- k j__ M.fadductor.

M. quadratus femoris,._ ——~

M., biceps femoris._ ___,

M., semitendinc sus. M. semimembranosus.

Fic. 70.—Ventral Aspect of the Hip Bone, with Areas of Muscular Attachment.

adductor, pectineus, and gracilis muscles. The shorter caudal branch
supplies the adductor only.

A. OBTURATORIA.—The obturator may be regarded as the terminal
branch of the hypogastric artery. It traverses the obturator foramen
obliquely in company with the homonymous vein and nerve. Con-
tinuing between the ischium and external obturator muscle, it appears
at the caudal border of the muscle, and divides into a considerable
number of branches. These end in the biceps, semitendinosus, semi-
membranosus, adductor, and quadratus femoris muscles. In addition,
the obturator furnishes the deep artery of the penis (a. profunda penis).
Anastomoses are established with the deep femoral and _ posterior

femoral arteries.
The obturator vein (v. obturatoria) is a satellite of the artery.

1 Tia (L.she Pay byl RriGpered Hes] the loin.

106 TOPOGRAPHICAL ANATOMY OF

A. PROFUNDA FEMORIS.—The deep femoral artery leaves the external
iliac just before this vessel merges into the femoral. Generally the
deep femoral arises in common with the pudendo-epigastric trunk,
but often its origin is independent. It runs between the pectineus
muscle and the hip joint, and, at the proximal border of the insertion
of the quadratus femoris, furnishes a large branch, the medial circumflex
femoral artery (a. circumflexa femoris medialis), which curves round the
back of the femur to end in the biceps muscle. Branches of the deep
femoral anastomose with the obturator artery.’

A. FEMORIS POSTERIOR—The terminal part of the femoral artery,
now exposed, extends from the point at which the vessel pierces the
adductor muscle to its disappearance between the two heads of the
gastrocnemius. Just as it is about to end the femoral gives origin to
the posterior femoral artery, which, after a short horizontal course in a
backward direction, divides into ascending and descending branches.
The ramus ascendens runs in a proximal direction, and supplies small
arteries to the biceps, semitendinosus, semimembranosus, and lateral
vastus muscles. A small and inconstant twig often passes along the
tibial nerve and anastomoses with the obturator artery. Though this
twig may be absent, a large vein, which serves as a connecting link
between the obturator and posterior femoral veins, is always present,
and serves as a guide to the possible position of the artery.

The ramus descendens passes along the surface of the lateral head
of the gastrocnemius muscle. A twig from it accompanies the tibial
nerve, and ends by joining the recurrent tibial artery.

Five or six popliteal lymph glands (lymphoglandule poplitese) form
a small group about the division of the posterior femoral artery.

N. 1scH1apicus.—A more complete examination of this nerve will
be possible during the dissection of the gluteal region. In the mean-
time its two terminal branches should be noted. Of these, the more
medial—the tibial nerve—is the larger, and leaves the present dis-
section by disappearing between the two heads of the gastrocnemius
muscle. Muscular branches (rami musculares proximales) pass from
the tibial nerve to the semimembranosus, semitendinosus, and biceps.

The smaller branch of the sciatic—the common peroneal nerve—enters
the leg between the biceps and the lateral head of the gastrocnemius.

_ Dissection.—The gluteal and hip region and the lateral aspect of the
thigh must now be examined. Before the skin is removed, certain

1 Because the point of origin of the deep femoral artery is subject to variation,
and because the origin may occur distal to the border of the pubis, some writers
describe the vessel as a branch of the femoral artery. The specimen from which
Figs. 66 and 67 were drawn illustrates a distal origin independent of the pudendo-
epigastric trunk.

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THE LIMBS OF THE HORSE 107

bony points should be located. There will be no difficulty in deter-
mining the position of the projecting angle of the ilium (coxal tuber),
but careful and deep palpation will be necessary if the true position of
the sciatic tuber and great trochanter is to be ascertained. If the
subject is thin, grooves marking the lines of apposition of the gluteal
and biceps and the biceps and semitendinosus muscles may be recognised,
and a projection caused by the sacral tuber of the ilium may be
noticeable.

_An incision is to be made through the skin round the root of the
tail and along the line of the vertebral spinous processes as far as the
level of the last rib. In all probability dissectors of other regions have
already removed the skin from the loins. If this has not been done,
a transverse incision must be made from the point at which the first
incision ends. The skin is now removed from the whole of the hip and
thigh and about half of the leg.

CUTANEOUS NERVES OF THE HIP AND THIGH.—Cutaneous nerves are
numerous in this part of the limb. (1) Three, derived from the dorsal
branches of the lumbar nerves, appear a short distance from the middle
line of the body in the area bounded by the line of the last rib and a
transverse line on a level with the coxal tuber. (2) Five cutaneous
nerves are the terminations of the dorsal branches of sacral nerves.
Four of them become superficial in a line with the lumbar cutaneous
nerves, and one of them (the first) appears close to the coxal tuber.
(3) The terminal branches of the postervor cutaneous nerve of the thigh
appear between the biceps and semitendinosus muscles distal to the
level of the hip joint. (4) About the same point a cutaneous branch
of the sciatic nerve appears. (5) The lateral cutaneous nerve of the
thigh pierces the abdominal wall close to the coxal tuber, and is
distributed over the lateral and anterior aspects of the thigh. (6) A
short distance cranial to the foregoing a cutaneous branch of the ilio-

inguinal nerve pierces the wall of the abdomen and passes downwards ,
to the patellar region. (7) Cutaneous branches of the tibial nerve, ee
emerge from the biceps muscle close to its insertion, 9/24 64, aoe

FASCIA OF THE HIP AND THIGH.—After removal of the comparatively
loose and fat-laden superficial fascia the very strong deep fascia is
exposed. In the gluteal region (fascia glutez) it is closely adherent to
the underlying muscles, and affords origin to some of their fibres. The
gluteal fascia is attached to the spinous processes of the sacrum, the
short sacro-iliac ligament, and the coxal and sacral tubers of the ilium.
Cranially it is continuous with the lumbo-dorsal fascia, and behind
with the fascia of the tail.

Over the lateral aspect of the thigh is spread the stout fascva lata,
into which a muscle—the tensor of the fascia lata—is inserted. [ound
the front of the thigh this fascia is continuous with that already
examined on the medial aspect of the limb. A prolongation of it

passes underneath the cranial houlenpe the bisers, to become connected

108 TOPOGRAPHICAL ANATOMY OF

with the tendon of insertion of the superficial gluteal muscle. Distally
the fascia lata is continuous with the fascia of the leg, and is attached

N. cutaneus femoris lateralis.

From sacral nerves. ¥Frora lumbar nerves.

From coccygeal nerves.

t
1
1
ses * rt i)
N. cutaneus femoris posterior. 1
i}

¥
“~~ From n, tibialis. } N. ilioinguinalis.

—-~---—~~—.-N. cutaneus sure posterior.

)

---— —--.------N. peroneus superficialis.

Fic. 71.—Cutaneous Nerves of tne Pelvic Limb.

to the surface of the patella and blended in part with the patellar
ligaments.
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THE LIMBS OF THE HORSE 109

Dissection.—The removal of the deep fascia is tedious, and more
particularly so over the gluteal muscles. The dissector will be well
advised to begin its removal just distal to the level of the hip joint
and work in a proximal direction. The fascia lata should not be
interfered with until its tensor muscle has been examined.

M, TENSOR FASCLE LAT#.—The tensor of the fascia lata has a com-
paratively restricted origin from the coxal tuber of the ilium; but, in
addition, some fibres spring from an intermuscular septum that is
adherent to the lateral border of the ilium, and from which some of
the fibres of the superficial gluteal muscle arise. From this origin the
fibres of the muscle spread out in fan-like manner, to merge into the
fascia lata and the fascia of the leg. Through its fascial connections
the muscle may be regarded as having indirect insertions to the patella,
the most lateral of the three patellar ligaments, and the crest of
the tibia.

Dissection. —The fascia lata should now be cut across about the middle
of the thigh and transverse to the long axis of the limb. Its tensor
should then be turned forwards as far as possible.

M. GLuTaus SUPERFICIALIS.{The superficial gluteal? muscle consists
of two fleshy parts that converge and blend towards the insertion of
the muscle into the third trochanter of the femur.’ The lateral portion
of the muscle arises from the coxal tuber of the ilium in common with
the tensor fasciz late, from the lateral border of the ilium in the
neighbourhood of the coxal tuber, and from the intermuscular septum
between the gluteal muscle and the tensor fasciz late. The medial part
takes origin from the gluteal fascia not far from the sacral tuber of
the ilium.

M. BICEPS FEMORIS.—The very powerful and thick biceps muscle has
a double origin. One head arises from the spinous processes of the third,
fourth, and fifth sacral segments, the short dorsal sacro-iliac ligament,
the coccygeal and gluteal fasciz, and the sacro-tuberous ligament. The
other head is tendinous, and has origin from the sciatic tuber. The two
heads combine to form a single muscular mass that soon divides into
three parts. (1) The most anterior portion is the strongest, and, by
means of an aponeurotic tendon, is inserted into the patella and the
most lateral of the three bands that represent the patellar ligament. It
is also connected, by a flattened tendinous band, with the femur behind
and immediately distal to the third trochanter, where a synovial bursa
lies between the tendon and the bone. (2) The aponeurotic tendon of
the middle portion of the muscle is attached to the crest of the tibia
and the fascia of the leg. (3) The posterior part of the biceps also is
connected with the fascia of the leg, and, by means of a stout band

1 yAourdés(gloutos) [Gr.], the buttock.
ss Bighbed By Wiicfosone

v

a

ML. semitendinosus. : superiicialis. medius. sacral nerves.

110 TOPOGRAPHICAL ANATOMY OF

(tendo accessorius), which accompanies the tendon of Achilles, with the
tuber of the calcaneus.

Cutaneous branches of Cutaneous of lumbar

M. biceps femoris. M. gluteus M. gluteus
' : nerve.

I,
\ \ i
i

\y
"

‘i

\ \

SAN
an\\\
\

\

State
WW
RTA

\

i

a

he

\
ra \
mh

Ni

:

Z
.

i:

Reins he

{

: Last intercostal nerve.
N. iliohypogastricus.

M. obliquus abdominis externus.

: N. ilioinguinalis.

M. tensor fascize late.

M. vastus lateralis.

WN
" . t W * M. biceps femoris,
/

Fic. 72. —Superficial Dissection of the Gluteal Region and Lateral Aspect of the Thigh.

Though the biceps muscle is described above as having a two-headed
origin, it must be remembered that the two heads do not correspond
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ol

THE LIMBS OF THE HORSE 111

to the double origin of the muscle in man and many other mammals
(eg. the dog). The name “biceps” was originally given to the muscle
in man, because in him it arises by two heads, one from the ischium,
and one from the femur; that is to say,in the horse the two heads
of the human and canine muscle are represented by one head only.
That head of the horse’s muscle which is attached to the sacrum is
apparently not a part of the biceps proper, but represents a gluteal
muscle (part of the superficial gluteal ?) that has become continuous with
the biceps. Hence it has been suggested that the resultant combined
muscle should be called m. glutceo-biceps.

M. SEMITENDINOSUS.—The semitendinous muscle forms the greater
part of the posterior border of the thigh, where it lies between the
biceps and the semimembranosus muscles. It has two heads of origin.
One arises from the spinous process of the last sacral segment, the
transverse processes of the first and second coccygeal vertebre, the
aponeurotic fascia of the tail, the edge of the sacro-tuberous ligament
where it is blended with the origin of the biceps, and the intermuscular
septum shared by the biceps. The other uead springs from the ventral
surface of the sciatic tuber and the ridge that runs forwards from this
tuber. The aponeurotic tendon that succeeds the fleshy belly of the
muscle is partly attached to the crest of the tibia and partly blended
with the fascia of the leg. Its connection with the tendo-accessorius
of the biceps, and its consequent indirect attachment to the tuber of
the calcaneus, should also be noted.

As with the biceps, so also with the semitendinosus of the horse, it
appears probable that the sacral origin represents portion of a gluteal
muscle. In man, ruminants, and the domestic carnivora the muscle

Hig ieacda

had only one origin, namely, from the sciatic tuber.

~” Dissection.—Cut through the sacral origin of the biceps and
semitendinosus muscles a short distance from the sacrum. Do the
same with their origin from the sciatic tuber. Then cut across the

muscles about half-way down the thigh and remove the intervening |

portions. In doing this dissection, note the nerve supply (from the

caudal gluteal and sciatic) of the two muscles.

. A small lymph gland should be looked for under the biceps and on |

ie ‘the course of the caudal gluteal artery.

~~ The sheet of fascia that continues the fascia lata underneath the ~

-* ' biceps and is connected with the sciatic tuber and the sacro-tuberous
_ ligament must be examined and removed. Observe the continuity of

- this fascia with the tendon of the superficial gluteal muscle.
~~ Next liberate both origins of the superficial gluteal muscle and thus

‘order to reach the superficial gluteal.
M. aLurmus MEDIUS.—The middle gluteal muscle is the thickest

and strongest muscle of bRedsbals Paro obtentirely covers the surface

va expose the middle member of the group. Note that a branch of the |
| caudal gluteal nerve bends round the edge of the piriformis muscle in ©

112 TOPOGRAPHICAL ANATOMY OF

of the ilium and overlaps the longissimus dorsi muscle, gradually
thinning away until it reaches the level of the last rib. Tle origin of

M. biceps femoris.

Caudal gluteal vessels. —: N. gluteus caudalis. «
: : Cranial gluteal vessels and nerve.
, :

M. semitendinosus.

SM. tensor
fascive late.

Shot Spe vo Lateral circum-
flex vessels,

Synovial bursa
of m. glutius

Proximal muscularramus _ _ _ a 1 medius,
of n. tibialis. dh N f NAAR AY MM. rectus
\ femoris,
M. semitendinosus. -—— Tl Medial
( H y UL IAIN) Na ANT Ue edial circum-
Jbturator vessels. \ flex vessels.
N. tibialis. -— - -M. vastus
N lateralis,
M, adductor, —_— _ _
N. peronzeus communis. ___ _ \
M.semimembranosus, _ _ _ \

N. cutaneus sure posterior. ~ —- —-
©P MM. gastroc-

nemius.

Posterior femoral vessels.. - } Ye ; KK . \
Ne i i <A
oP a \ ¥ ; {M. biceps femoris.

} . 2
;
Ve =
sah
Y il)
id /
f/ si
et a
(ee: oe
a fe
/ sy :
, 7% /%
PAG SF 3
S A wf,
: Z Z

Fic. 73.—Deep Dissection of the Gluteal Region and Lateral Aspect of the Thigh.

the muscle is from the aponeurotic covering of the longissimus dorsi,
the gluteal surface and both tubers (coxal and sacral) of the ilium, the
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THE LIMBS OF THE HORSE 113

long and short dorsal sacro-iliac ligaments, and the gluteal fascia.
Several tendinous strata occur in the substance of the muscle, the
strongest of these being attached to the gluteal line of the ilium, thus
dividing the muscle into superficial and deep portions.

The insertion of the middle gluteal is double: (1) The greater
(superficial) part is inserted to the highest and most posterior part of
the great trochanter of the femur. (2) The deeper part ends in a stout,
flattened tendon that plays over the convex, anterior portion of the
great trochanter, and is attached to a special ridge immediately distal
venes between the tendon and the bone. According to some authorities,
the deeper part of the middle gluteal muscle should be regarded as a
separate m. gluteus accessorius.

M. pirirormis.—The piriformis! muscle lies along the posterior
border of the middle gluteal, with which it is so blended as to lead the
dissector to regard the two muscles as one, unless warned to the
contrary.

The origin of the piriformis (inseparably blended with the middle
gluteal muscle) is from the edge of the sacrum, and its insertion is to
the inter- trochanteric crest of the femur.

Dissection.—The whole of the middle gluteal muscle, except its
insertion, must now be removed. This must be done with care, other-
wise there is danger that the underlying deep gluteal muscle may be
injured. The removal of the middle gluteal permits the dissector to
determine that its deeper portion (m. gluteus accessorius) is attached to
the gluteal line of the ilium and to that area of the bone that is lateral
to the line. Examination of the trochanteric bursa also is now possible.

M. GLUTZUS PROFUNDUS.—The short but strong deep gluteal muscle
arises from the rough lateral surface of the sciatic spine, a portion of
the adjacent surface of the ilium, and a narrow area of the sacro-spinous
ligament where this is attached to the sciatic spine, and is inserted into
the margin of the convex portion of the great trochanter. As will be
seen later, some of its fibres are connected with the capsule of the
hip joint.

Mm. GEMELLI—Though generally named in the plural, there is some
justification for regarding the gemelli® of the horse as constituting
a single muscle, divisible into two strata except along its cranial border.
Both strata arise from the lateral border of the ischium opposite the
lesser sciatic foramen. The superficial stratum is inserted into the
trochanteric fossa close to the insertion of the internal obturator
muscle. The more extensive deep stratum is inserted within the inter-

1 Pirum [L.], a pear. Forma [L.], shape.
3 ‘Lus,[ Le |y twin».
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114 TOPOGRAPHICAL ANATOMY OF

trochanteric crest, immediately lateral to the insertion of the external
obturator.

“MM. oprurator: INTERNUS.—In the present dissection only the
flattened terminal part of the internal obturator musclé is visible.
Leaving the interior of the pelvis by the lesser sciatic foramen, where
there is a synovial bursa between the muscle and the bone, the flattened
tendon lies on the surface of the gemelli muscles, and is inserted into
the proximal part of the trochanteric fossa.

Mm. semitendinosus : : :
et biceps femoris. M. biceps femoris. M. gluteus medius.

Mm. semitendinosus —-——~——
et semimembranosus.

M. gluteus AML. tensor
profundus. : fascice lati.
M. iliacus. f
M. gluteus superficialis.
M. biceps...
femoris.
M. capsularis.

' M. rectus femoris.
Mn. gemelli.

M. adductor...
M., obturator externus.

Fic, 74.—Lateral Aspect of the Hip Bone, Sacrum, and associated Ligaments, with Areas
of Muscular Attachment.

M. vasTUS LATERALIS.—The lateral vastus muscle arises from the
greater part of the lateral and anterior surfaces of the femur. Its
insertion is to the patella in common with the rectus femoris.

A. GLUTHA CRANIALIS.—The cranial gluteal artery is one of the
branches of the hypogastric. Its origin will be disclosed during the
dissection of the pelvis, and it will then be seen that the vessel
quickly divides into a number of branches, which leave the pelvis by
the greater sciatic foramen, and are exposed in the present dissection.
They supply the gluteal muscles. '

A. GLUT&A CAUDALIS.—The caudal gluteal artery is a vessel of some
size. A branch of the lateral sacral artery, it pierces the sacro-tuberous
ligament close to the border of the sacrum, and terminates in branches

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THE LIMBS OF THE HORSE 115

that supply the biceps, semitendinosus, semimembranosus, superficial
gluteal, and coccygeus muscles. Branches also anastomose with the
obturator and deep femoral arteries.

N. GLUTAUS CRANIALIS.—As will be seen in the dissection of the
pelvis, the cranial gluteal nerve arises by roots derived from the sixth
lumbar and first sacral nerves. As a single nerve-trunk it can scarcely
be said to exist, for it almost immediately divides into three, four, or
five branches, which the dissector of the gluteal region will find travers-
ing the greater sciatic foramen along with the cranial gluteal vessels
and the sciatic nerve. These branches supply the gluteal muscles, and
one runs between the middle and deep gluteal to end in the tensor of
the fascia lata.

N. GLUTHUS CAUDALIS.—Of the two nerves that run backwards
(caudalwards) on the surface of the blended sacro-spinous and sacro-
tuberous ligaments, the more dorsal is the caudal gluteal. Its origin
from the sacral nerves will be revealed during the dissection of the
pelvis. At the present time the dissector has to note the exit of
the nerve from the greater sciatic foramen and its distribution in
the middle gluteal, piriformis, and biceps muscles, One of its branches
—to the superficial gluteal muscle—has been previously observed as it
bends round the border of the piriformis muscle.

N. CUTANEUS FEMORIS POSTERIOR.—The posterior cutaneous nerve
of the thigh leaves the pelvis by the greater sciatic foramen along with
the sciatic nerve, with which it is connected for a longer or shorter
distance. The nerve runs along the surface of the sacro-spinous and
sacro-tuberous ligaments in the direction of the sciatic arch. After
giving a communicating branch to the pudendal nerve it divides into
two branches. The more dorsal of these ends in the semitendinosus
muscle! The ventral branch is mainly cutaneous in its distribution.
After passing over the lateral aspect of the sciatic tuber it runs between
the biceps and semitendinosus muscles to gain the surface of the limb,
where it is distributed to the skin of the lateral and posterior part of
the thigh.

N. iscurapicus.—The sciatic nerve leaves the pelvis by the greater
sciatic foramen in company with the gluteal nerves and vessels. Asa
broad band of nerve fibres it passes backwards (caudalwards) obliquely
to the level of the hip joint, where it ends by dividing into two branches
of unequal size—the tibial and common peroneal nerves. The exact
point of division of the sciatic is variable, being occasionally so early
as to be close to the greater sciatic foramen.

In its course the nerve lies in succession on the sacro-spinous

1 Some writers regaDicihischran hypo martgothe caudal gluteal nerve.

116 TOPOGRAPHICAL ANATOMY OF

ligament, the deep gluteal muscle, the extra-pelvic part of the
internal obturator, the gemelli, and (possibly) the quadratus femoris
muscles. It is covered by the middle gluteal, piriformis, and biceps
muscles.

Only one small collateral branch leaves the sciatic nerve. This is

ge --; M. gluteus medius.
t
H
f

M. piriformis. ~~

---- M. vastus lateralis

M, gluteus superficialis.~--4

M. gastrocnemius
(caput laterale).

Lig. collaterale fibulare.

M. liteus.
popliteus. \----4\ Ze PF a Mm. peroneus tertius et ex-
tensor digitorum longus.

Fic. 75,—Lateral Aspect of the Femur, with Areas of Muscular and
Ligamentous Attachment.

distributed to the internal obturator, gemelli, and quadratus femoris
muscles. The twig to the internal obturator enters the pelvis by the
anterior part of the lesser sciatic foramen.

N. Trpiais.—The tibial nerve is the larger and more posterior of
the two nerves into which the sciatic divides. It runs down the back
of the thigh between the biceps (lateral) and the adductor and semi-
membranosus muscles (medial), to disappear from the present dissec-

tion by entering the gap between the two heads of the gastrocnemius
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THE LIMBS OF THE HORSE Lit

muscle. Its subsequent course will be followed in the dissection of
the leg.

While in the thigh, the tibial nerve gives off two branches. (1) The
proximal muscular ramus (ramus muscularis proximalis) is large,
and leaves the tibial close to the level of the hip joint. It very soon
divides into nerves that are distributed to the biceps, semimembranosus,

M. gluteus medius. |

M. gluteus profundus. _ |
M, vastus lateralis. _____— ~M. vastus medialis.

M. glutieus superficialis. -

M. gastrocnemius (caput laterale), -----_ 1]

___Mm. adductor et semimembranosus.

) Lig.{collaterale tibiale.

]

Lig. collaterale fibulare..

Mm. peronzeus tertius et extensor :
digitorum longus.

Fic. 76.—Anterior Aspect of the Femur, with Areas of Muscular and
Ligamentous Attachment.

and semitendinosus muscles. (2) The posterior cutaneous sural’ nerve
(n. cutaneus sure posterior (medialis)) is a small branch that leaves
the tibial just before it passes between the two heads of the gastro-
cnemius muscle. Leaving the thigh by following the lateral face of
the gastrocnemius, the sural nerve will be examined later in the
dissection of the leg.

N. PERONZUS COMMUNIS.—The common peroneal? nerve travels down

1 Sura [L.], the calf of the leg.
2 repdvn (perongyEGEdthy pinghadbrageh or buckle (fibula).

118 TOPOGRAPHICAL ANATOMY OF

the back of the thigh in company with, and immediately anterior to,
the tibial nerve. Arriving at the gastrocnemius muscle, the two nerves
part company, the peroneal running over the lateral head of the
gastrocnemius, under cover of the biceps, to reach the region of the

4 _-.M. gluteus ,medius.

--Mm. gemelli.
—--M. obturator internus.

—~--M. obturator externus.

}... M. quadratus femoris.

-~--M. pectineus.

----M gastrocnemius (caput mediale).

_ Mm. adductor et semimembranosus.

Lig. collaterale tibiale.

Fic. 77.—Medial Aspect of the Femur, with Areas of Muscular and
Ligamentous Attachment.

head of the fibula, where it divides into the superficial and deep
peroneal nerves.

The collateral branches of the common peroneal nerve are three
in number. (1) A small nerve to the biceps muscle. (2) A small
filament (occasionally absent) that arises about the middle of the
thigh and joins the posterior cutaneous sural nerve. (3) The anterior
cutaneous sural nerve (n. cutaneus sure anterior (lateralis)), which,
dividing into two or three branches, pierces the distal part of the biceps
and is distributed to the skin of the lateral surface of the leg.

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THE LIMBS OF THE HORSE 119

Dissection.—The deep gluteal muscle must b 1
ssection. glu e reflected in order that
the origin of the rectus femoris and capsularis muscles may be thoroughly
exposed. Care must be taken not to injure the capsule of the hip joint,
with which the deep gluteal muscle is intimately associated.
nee tes epee fascia connects the tensor of the fascia lata with
order o é illum, and covers the lateral i ili
muscle. This must be cut away. oe

M. gluteus medius.

M. gluteus profundus.

- piriformis.

. gluteus medius.

\ == Mm. i.
M. obturator externus,----}------ pin ene

M. iliopsoas. ___

M. quadratus femoris. ___\ -#\ .M. biceps femoris

- M. glutieus superficialis.

Sch, M. adductor.

M. gastrocnemius (caput
laterale).

M. plantaris.

M, gastrocnemius (caput mediale). ____

Mm, adductor et semi ES
membranosus” “+. on CER _- Lig. cruciatum anterius.

Lig. collaterale tibiale. ._¢

-M. popliteus.

Lig. cruciatum posterius.
Fic. 78.—Posterior Aspect of the Femur, with Areas of Muscular and
Ligamentous Attachment.

* = Area of attachment of one of the ligamentous bands of the lateral meniscus.

M. QUADRICEPS FEMORIS.—Although named the quadriceps, only

three heads can be satisfactorily demonstrated. These are the two
vasti muscles (m. vastus medialis and m. vastus lateralis), already
dissected, and the straight muscle of the thigh (m. rectus femoris), now
to be examined. The fourth head (m. vastus intermedius) is so much
blended with the medial vastus as to be, to all intents and purposes,

part of this muscle.

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120 TOPOGRAPHICAL ANATOMY OF

M. rectus femoris—The rectus femoris muscle is the middle
member of the quadriceps group, and arises by two short tendons from
depressions on the ilium just in front of the acetabulum: there is a
mucous (synovial) bursa between the lateral tendon and the ilium.
Its insertion is into the patella along with the other parts of the

quadriceps.
M. gluteus profundus.

Fig, 79, Proximal End of the Femur, with Areas of Muscular Attachment.

M. capsuLaris.—The capsular is a narrow, elongated strip of
muscle lying close against the hip joint, and running between the
lateral vastus and rectus femoris. Its origin is from the ilium close
to the lateral origin of the rectus, and its insertion is into a slight ridge
on the anterior surface of the proximal third of the femur.

Mm. peronzeus tertius et extensor __
digitorum longus.

Lig. coilaterale fibulare. .. >
Gi. Lig. collaterale tibiale.

M. popliteus. - \

/
Lig. cruciatum anterius. Lig. cruciatum posterius.

Fic. 80.—Distal End of the Femur, with Areas of Muscular and Ligamentous
Attachment.

A. CIRCUMFLEXA FEMORIS LATERALIS.—The lateral circumflex artery
of the thigh is a branch of the obturator, and, in the present dissection,
appears between the ilium and the iliacus muscle. Branches are
furnished to the superficial and middle gluteal muscles and the tensor
of the fascia lata. The main continuation of the artery disappears

between the rectus femoris and the lateral vastus muscles, in which it
is expended,

Dissection.—Cut across the sciatic nerve a short distance from the
greater sciatic foramen and the femoral vessels on a level with the hip
joint. Remove the remains of those muscles that are attached in close

proximity to the hip joint, and clean the outer surface of the joint
capsule.

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THE LIMBS OF THE HORSE 121

Fic. 81.—Key Outline of the Pelvic Limb to Indicate the Level of the Transverse
Sections illustrated in Subsequent Figures.

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129 TOPOGRAPHICAL ANATOMY OF

THE HIP JOINT (articulatio coxw)—The joint capsule (capsula
articularis) of the hip joint is in the form of a roomy, double-mouthed

M. rectus femoris. -————

M. vastus medialis.-—-—~

f.\

A-- M. vastus lateralis.

AM. sartorius.-——-

Saphenous vessels and
nerve.

SedeQees 4 Femur.

A. femoralis. ____

M. adductor. ___

Nn. tibialis et peronus _
communis.

M. gracilis. -

Joeeos M. semitendinosus.

Fie. 82.—Section across the Thigh at the Level indicated by M in Fig, 81.

sac, one end of which is attached to the margin of the acetabulum and
the transverse ligament thereof. The femoral attachment is to the
neck of the bone, a very short distance from the articular margin,
except at the lateral part of the joint, where 2 or 3 cm. of the neck

is included within the capsule. The eae part of the capsule is
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THE LIMBS OF THE HORSE 123

lateral and anterior, where an oblique band of fibres passes from the
ilium to the femur and represents the iio-femoral ligament (ligamentum
ilio-femorale) of the human joint. The capsule is closely supported

++ --_-llium.

M. rectus femoris,

Lig. iliofemorale.

Lig. transversum

Greater trochanter. acetabuli.
; ‘

oe
<a
TAs
ay.
a
Ty

i Lig. accessorium.

/ d
a Pubis.
/

Third tro-. _§_ — ~--44
chanter.

Fic. 83.—Anterior Aspect of the Hip Joint.

The line of attachment of the synovial lining of the joint capsule is indicated in red.

by muscles (external obturator, deep gluteal, and capsular) except
posteriorly, where it is overlaid by a cushion of fat.

Dissection.—Open the joint capsule and examine its contents.

The hip joint is formed by the acetabulum and the head of the
femur; but it must be remembered that the whole of the acetabulum

is not articular, inasmysh Asis PMS dalf contains a depressed non-

124 TOPOGRAPHICAL ANATOMY OF

articular fossa acetabuli! Nor is the whole of the head of the femur
articular, for it carries an extensive fovea to which ligaments are
attached.

Surrounding the acetabular margin is a ring of fibro-cartilage, the
labrum glenordale? continued across the incisura acetabuli by a liga-.

Lig. teres. Lig. transversum acetabuili.
Lig. accessorium. ; : hi
: : : lum.

Pubis. F : : Obturator foramen. Isc m

g q \ &
oe // \ mm fi |
a lk ee Y , bs
a if < Zins iy ws +
M. rectus femoris. i) . i My t
ue \ yy, |
aa. yyy Y
( fh ‘ w ! :
fl. Greater trochanter. ‘Sciatic tuber.
fr f) :
it
HIN

Head of femur.
Fic. 84.—Medial Aspect of the Hip Joint.

The line of attachment of the synovial lining of the joint capsule is indicated in red,

mentous bridge, the transverse ligament (ligamentum transversum
acetabuli).

Passing from the fossa acetabuli, close to the acetabular notch, to
the fovea on the head of the femur is the short, strong round ligament
(ligamentum teres). In the hip joint of the Equide a ligamentous
band, the accessory ligament (ligamentum accessorium), springs partly
from the pubic insertion of the straight abdominal muscle and partly

* Fossa (L.], a ditch or trench. Acetabulum [L.], a vessel for vinegar (from

acetum, vinegar). C. Plinius Secundus applies the name to the socket of the
hip bone.

* Labrum (L.], a lip or vim. yAxjvy (glen) [Gr.], a cavity or pit. «70s (eidos)
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THE LIMBS OF THE HORSE 125

from an oblique groove on the ventral surface of the pubis, and enters
the joint cavity through the acetabular notch dorsal to the transverse
ligament, to blend with the femoral attachment of the round ligament.

The articulation between the acetabulum and the head of the femur
being of the nature of a ball-and-socket joint, the range of movement
in it is considerable. Flexion and extension, abduction and adduction,
circumduction, and rotation are all possible, but not in like degree.
The movements of flexion and extension are most free, while abduction
is limited by the round and accessory ligaments, and adduction is
similarly restricted by the close association of the gluteal muscles with
the joint.

Dissection.—The anterior, lateral, and posterior aspects of the leg are
occupied by a thick layer of muscles closely invested by stout fascia.
In consequence, it is impossible to distinguish the boundaries of the
various muscles by palpation in the proximal half of the leg. The
medial surface, on the contrary, carries no muscles, with the result that
the flat surface of the tibia can readily be felt through the skin.

As the tarsus is approached, the tendons of some of the muscles
become sufficiently obvious to permit of ready recognition. For
example, the tendon of Achilles (gastrocnemius and plantaris tendons)
is visible in its relation to the tuber of the calcaneus, a hollow on each
side of the limb giving it greater prominence. A sbarp fold of skin on
the flexor aspect of the tarsus is also a prominent feature of the super-
ficial anatomy of the limb, and marks the position of the tendons of
the peroneus tertius, long digital extensor, and anterior tibial muscles.

A horny callosity (“chestnut”), similar to that present in the distal
part of the forearm, projects from the skin over the distal part of the

medial surface of the tarsus.
The skin should be removed from the whole of the leg and tarsus,
and as far in a distal direction as the junction of the proximal and

middle thirds of the metatarsus. ;
Care must be taken not to injure the superficial veins and the

cutaneous nerves.

V. sAPHENA.—The origin of the saphenous vein as the medial dorsal
vein of the metatarsus is now exposed. The vein crosses the flexor
aspect of the tarsus, and then runs up the medial aspect of the leg
and thigh in order to reach the apex of the femoral triangle. Near
the tarsus the saphenous vein is connected with the anterior tibial,
and in the proximal third of the leg it is joined by the recurrent
tibial vein.

V. RECURRENS TIBIALIS.—The recurrent tibial begins at the tarsus
as the continuation of the lateral plantar metatarsal vein. Near its
origin it is connected with the posterior tibial and recurrent tarsal
veins. It follows the medial border of the tendon of Achilles and the
medial head of the gastrocnemius muscle to join the saphenous vein

in the proximal part Bigith® ol BY ye mign-ayith either the posterior

126 TOPOGRAPHICAL ANATOMY OF

M. adductor,

“/ yi f ‘
Yi i Vtg »
hn \
A. saphena. . ihe aes \
V7,
a
2 i
eH
V. saphena. oA
M. popliteus,__—_____—~— 2

‘M. flexor digitorum longus. AY . x \

M. tibialis anterior. \\

era N. tibialis.

. M. plantaris.

M. flexor hallucis. —-——-~—-—-.- :
—. Tendo accessorius
of biceps.
— A.recurrens tibialis.
A. tibialis posterior, —————

A. tarsea medialis.

A
\ | \ *

Nn. plantares.

‘*Cunean’ tendon of m, tibialis anterior. -——

V. metatarsea dorsalis medialis. —__

Fie. 85.—Superficial Dissection of the Medial Aspect of the Leg and Tarsus.

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THE LIMBS OF THE HORSE 127

femoral or the popliteal vein is established through an anastomotic
vessel of some size.

V. TARSEA RECURRENS.—The recurrent tarsal vein follows the lateral
border of the tendon of the gastrocnemius, and ends by uniting with
the posterior femoral vein, which it gains by passing between the
biceps and the lateral head of the gastrocnemius. In the region of the
tarsus it communicates with the lateral metatarsal and recurrent
tibial veins.

N. sapHENUS.—The skin over the medial aspect of the leg and
tarsus is supplied by branches of the saphenous nerve.

N. CUTANEUS SUR POSTERIOR (MEDIALIS).—-As has been seen already,
the posterior cutaneous sural nerve is a branch of the tibial. It
accompanies the recurrent tarsal vein along the lateral head of the
gastrocnemius and the lateral border of the tendon of this muscle, and
supplies the skin over the posterior and lateral face of the leg, tarsus,
and metatarsus.

N. CUTANEUS SUR ANTERIOR (LATERALIS).—The anterior cutaneous
sural nerve, a branch of the common peroneal, pierces the biceps close
to the aponeurotic tendon of this muscle, and is distributed to the skin
over the lateral surface of the leg.

N. PERONZUS SUPERFICIALIS.—The superficial peroneal, the smaller
of the two terminal branches of the common peroneal nerve, pierces
the fascia about the middle of the tibial region, and supplies the skin
over the anterior and lateral aspect of the leg, tarsus, and metatarsus.
Its muscular branch—to the long peroneal muscle—will be disclosed
at a later stage of the dissection.

FAscIA OF THE LEG AND TARSUS.—The strong fascia of the leg
(fascia cruris) can be resolved into several layers, but whether to do
this is worth the while of the dissector is open to question. It is
probably sufficient to note that there is little difficulty in distinguishing
three layers. The most superficial layer is a continuation of the fascia
lata and the fascia of the medial surface of the thigh; while the middle
layer is connected with the expanded tendons of the tensor fascia
latee, biceps femoris, gracilis, sartorius, and semitendinosus muscles.
These two layers are closely associated with each other, and together
form a common investment for the muscles of the leg. They are firmly
attached to the tibia and blend with the ligaments of the patella, and,
distally, they are continuous with the fascia of the tarsus and meta-
tarsus. In addition, they are connected with the calcaneal attachment
of the biceps and semitendinosus muscles.

The deepest layer of the fascia of the leg forms intimate sheaths

for the muscles, and Saynishesynbermusgaiar septa from which, not

128 TOPOGRAPHICAL ANATOMY OF

infrequently, fibres of the muscles have origin. As a consequence of
the attachment of the septa to the tibia the muscles of the leg are
grouped within three fascial compartments: (1) Tibialis anterior and
extensor digitorum longus; (2) peronzeus longus; (3) flexor digitorum
longus, flexor hallucis longus, tibialis posterior, and popliteus. Strictly
speaking, the popliteal muscle should be regarded as occupying a special
compartment of its own.

The tarsal fascia (fascia tarsi) is attached to the various bony
prominences in the region of the tarsus, and blended with the neigh-
bouring ligaments. At the back of the tarsus it is particularly strong,
forming a bridge from the medial collateral ligament on the one hand
to the tuber calcanei and the plantar ligament on the other. The
bridge converts the groove formed by the tarsus into a short canal,
through which the deep flexor tendon and the plantar vessels and
nerves pass to gain the metatarsus. As it passes through the canal,
the tendon is provided with a mucous (synovial) sheath.

In front of the tarsus also the fascia is strong, and here it is
connected with the tendon of the long extensor muscle. In this
region there are three fascial bands (transverse ligaments), which will
be examined in connection with the tendons of the anterior and lateral
tibial muscles.

Dissection.—The fascial investment of the muscles must now be
removed. It is well to begin this dissection at the back of the leg. In
the hollow bounded posteriorly by the tendon of the gastrocnemius
considerable care must be exercised to avoid injury to small vessels.
On the medial aspect of the limb in this region the small recurrent
tibial artery must be secured as it runs in a proximal direction close to
the edge of the gastrocnemius tendon. Risk of destruction of the vessel
will be minimised by first disclosing the medial tarsal artery from which
it arises. Over the lateral surface of the tuber of the calcaneus the
very small lateral tarsal artery is distributed.

As the dissection proceeds, it will be found necessary to remove the
fascial insertions of the biceps and semitendinosus muscles.

M. GASTROCNEMIUS.—The strong, tendinous gastrocnemius! muscle
takes origin from the femur by two heads, each definite and flattened.
The lateral head (caput laterale) arises from the margin of' the plantaris
fossa, while the medial head (caput mediale) springs from a rough
elevated area on the medial lip of the linea aspera at the same level
as the fossa. Through the gap between the two heads the popliteal
vessels and the tibial nerve gain the leg. The two heads soon join to
form a common fleshy belly, which tapers to a strong rounded tendon
about the junction of the proximal and middle thirds of the tibia.

The tendon of the gastrocnemius (tendo calcaneus Achillis) is very

vastip (gastér) [Gr.], belly. xvijpn (enémé) [Gr.), the leg.
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THE LIMBS OF THE HORSE 129

intimately related to that of the plantaris muscle. At first the plan-
taris tendon is the deeper of the two; but, twisting spirally round the
medial edge of the tendon of the gastrocnemius, it becomes the more
superficial before the summit of the tuber of the calcaneus is reached.
An extensive synovial bursa intervenes between the two tendons from
the point where the twist begins to about the middle of the tarsus. A
strong but narrow fascial band springs from the femur close to the
origin of the lateral head of the gastrocnemius, and, running down the
surface of this muscle, is blended with its tendon, as well as that of the
plantaris.

The insertion of the gastrocnemius is to a transversely disposed
depression on the summit of the tuber of the calcaneus, a small
synovial bursa intervening between the tendon and the anterior convex
area of the tuber.

M. soLeus.—The narrow, thin soleus! muscle lies along the lateral
border of the gastrocnemius. Its origin is from the head of the fibula,
and its slender tendon joins that of the gastrocnemius. .

Dissection.—Cut across the gastrocnemius muscle just where the two
heads are about to join. The reflexion of the lateral head is made a

little difficult by its close connection with the underlying plantaris
muscle.

M. pLantaris.2—The rounded plantaris ® muscle possesses a strength
out of all proportion to its volume, from the circumstance that it is
mainly composed of tendinous tissue among which are scattered
muscular fibres. The origin of the muscle is from the depths of the
plantaris fossa, where it is closely connected with the lateral head of
the gastrocnemius. As has been already noted, its powerful, rounded
tendon curves spirally round that of the gastrocnemius, and flattens out
over the summit of the tuber of the calcaneus, to which it is attached
by a medial and a lateral slip. As previously stated, a large synovial
bursa is interposed between the plantaris and gastrocnemius tendons
and between the plantaris tendon and the bone.

From the tuber of the calcaneus, the plantaris tendon appears to be
continued into the metatarsus; but there is reason for regarding this
apparent continuation as a modified short flexor of the digit (m. flexor

digitorum brevis).

1 Solea [L.], a sole fish (in a borrowed sense, from the outline of the fish having a
resemblance to the sole of the human foot). The name is given to the human

muscle on account of its shape. _ 7
2 This muscle is often termed the superficial flexor of the digit—m. flexor digi-

éorum (pedis) sublimis.
3 Plantaris [L.] (from planta, the sole of the foot), of or belonging to the sole of

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130 TOPOGRAPHICAL ANATOMY OF

Posterior femoral vessels.

N. tibialis, os=-- =-4Q=4

M. semimembranosus. - --~-----

M. biceps femoris,

N. peronzus communis. ---\--—-- ; } — g ‘ patellaris laterale.

M. semitendinosus. -—----+

— Lateral meniscus.
M. gastrocuemius. —-—-- }
' Mm. peronzus tertius et

N. peronzus superficialis. — extensor digitorumflongus,

rae F N. peronieus profundus,
M. tibialis posterior. - — H Seal? 4

M. flexor digitorum longus. -———1#

1) 7
WY H % Pa fi f fet ig -- M. extensor digitorum longus.

N. cutaneus sure posterior. __

M. flexor hallucis —~—-~
longus.

V. arsea recurrens.

A. tarsea lateralis.
al
N. peronzus profundus,

V. tibialis anterior.

_ A. dorsalis pedis.
__ M. extensor digitorum brevis. ‘

\

v W

Fic. 86.—Superficial Dissection of the Lateral Aspect of the Leg and Tarsus.

1, 2, 8, 4= Transverse ligaments that retain the extensor tendons in position.

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THE LIMBS OF THE HORSE 131

N. TIBIALIS.—The tibial! nerve, the larger of the two divisions of
the sciatic, has already been followed down the back of the thigh to the
point where it disappears between the two heads of the gastrocnemius
muscle. The rest of its course is now revealed. Between the heads of
the gastrocnemius the nerve comes into relation with the plantaris
muscle, the medial border of which it follows closely until the level of
the summit of the tuber calcanei is reached. At this point it divides
into the medial and lateral plantar nerves, which, passing down the

Posterior femoral vessels. M. plantaris.

)
Ny tibialis, --<<=--—5 t SWwelbe SN
Y ey a SV ® ie

M. semitendinosus,—\--+'\

M. gastrocnemius -—— a e.5,
(caput mediale). \ Se

aes | Lig. temoro-patellaris
Wi laterale.
Bi — Popliteal artery and
/ all)
A if eae Lig. collaterale fibulare.
F i —- Ligamenta patell.

li -- Lateral meniscus.

me = ; if

— Mm. peronzeus tertius et ex-
f tensor digitorum longus

M. tibialis posterior.——

M, gastrocnemius.-—

AM. soleus..—_—
Fic, 87.—Deep Dissection of the Popliteal Region.

short canal at the back of the tarsus, will be traced in the metatarsus
in a later dissection. In its course down the leg the tibial nerve is
related to a small artery (and its companion vein) that forms an anas-
tomotic link between the posterior femoral and recurrent tibial arteries.

The collateral branches of the tibial nerve are the proximal and
distal muscular rami, and the posterior cutaneous sural nerve. The
prozimal muscular branch (ramus muscularis proximalis) was examined
during the course of the dissection of the thigh. The origin of the
posterior cutaneous sural nerve (n. cutaneus sure posterior (medialis))
was noted as occurring about the middle of the thigh. The nerve
crosses the surface of the lateral head of the gastrocnemius muscle and

1 Trbia [L.|, the shin-bone ; the name was used in a borrowed sense to signify a
musical pipe, or flute, which was originally made of bone.

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132 TOPOGRAPHICAL ANATOMY OF

becomes superficial about the middle of the leg. Its superficial course
has already been examined. The distal muscular branch (ramus mus-
cularis distalis) arises from the tibial nerve as this lies between the
heads of the gastrocnemius muscle. It furnishes filaments to the
gastrocnemius, soleus, plantaris, the flexors of the digit, and the
popliteus.

Dissection.—Reflect the plantaris muscle, and examine the deep
muscles of the leg. These are four in number, three of which (flexor
hallucis longus, flexor digitorum longus, and tibialis posterior) may be
grouped together as the deep flexor of the digit.

M. FLEXOR DIGITORUM PROFUNDUS.—The deep flexor of the digit is
divisible into three muscles, the tendons of which join into one in the
neighbourhood of the tarsus.

(1) AL tibealis posterior—The posterior tibial muscle is the most
superficial of the three component parts of the deep flexor. Its origin
is from the lateral condyle of the tibia and the head of the fibula.
About the junction of the middle and distal thirds of the tibia a
flattened tendon takes the place of the fleshy belly of the muscle and
joins the tendon of the flexor hallucis longus shortly before the end of
the tibia is reached.

(2) M. flexor hallucis! longus,—This head of the deep flexor is much
stronger than the foregoing—with which it is more or less intimately
united—and contains a considerable proportion of tendinous tissue
interspersed among its fleshy bundles. It lies directly upon the tibia,
from the posterior surface and lateral condyle of which it rises, as well
as from the whole length of the fibula and the interosseous ligament.
A strong, rounded tendon, common to this and the foregoing muscle,
traverses the deep groove at the back of the tarsus, and later will be
followed down the metatarsus. It should be noticed that the common
tendon is exceedingly dense and partly cartilaginous where it plays
over the groove formed by the tuber and sustentaculum tali of the
calcaneus.

(3) M. flecor digitorum longus—The slender medial head of the
deep flexor is the most distinct, and lies in the groove between the
foregoing muscles and the popliteus. Its origin is from behind the
lateral condyle of the tibia. A slender, rounded tendon begins about
the middle of the tibia, traverses a groove provided with a synovial
sheath on the medial malleolus of the tibia, and joins the main tendon
of the deep flexor in the proximal third of the metatarsus.

M. popiirEvs.—The triangular popliteal? muscle covers part of the

1 Hallux [L.], the great toe. &ANouat (hallomai) [Gr.], to spring, leap, bound.

2 Poples [L.], the ham or hough. (In the horse, the term hough or hock is used to

indicate the tarsal region, instead of the back of the femoro-tibial joint.)

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THE LIMBS OF THE HORSE 133

flexor aspect of the joint between the femur and the tibia. Its origin
is within the capsule of the joint and beneath the femoral attachment

M. tibialis posterior. M. biceps femoris.

M. flexor digitorum longus. Sf M. tibialis anterior.

fe> M. flexor hallucis longus.

Fic. 88.—Lateral Aspect of the Proximal Part of the Tibia and Fibula, with Areas of
Muscular and Ligamentous Attachment.

*— Ayea of attachment of one of the ligamentous bands of the lateral meniscus.

of the lateral collateral ligament, from the more distal of the two
depressions on the lateral condyle of the femur. The strong tendon of

Ligamenta patelle.

M. tibialis anterior.
/__ Lig. collaterale tibiale.

_..M. gracilis.

M. flexor hallucis longus. --

Fie, 89.—Anterior Aspect of the Proximal Part of the Tibia and Fibula, with Areas of
Muscular and Ligamentous Attachment.

origin is clothed by part of the synovial lining of the joint, and is in
contact with the border of the lateral meniscus of fibro-cartilage.

The fibres of thenjaparacle p SPURAA Cie with different degrees of

134 TOPOGRAPHICAL ANATOMY OF

obliquity, and are attached to the triangular area on the proximal
posterior part of the tibia and the corresponding stretch of the medial
border of this bone.

Dissection.—Reflect the popliteus muscle so that the whole course of
the popliteal vessels may be followed.

A. POPLITEA.—The popliteal is the direct continuation of the femoral

M. semitendinosus. --44

SS iia M. tlexor hallucis
‘i longus.

Fig. 90.—Medial Aspect of the Tibia and Fibula, with Areas of Muscular an
Ligamentous Attachment.

* Area of attachment of one of the ligamentous bands of the medial meniscus.

artery, the line of demarcation being taken as the point at which the
vessel passes between the two heads of the gastrocnemius muscle. The
artery traverses the notch between the two femoral condyles and
comes into close relation with the capsule of the femoro-tibial joint.
During the first part of its course the artery runs parallel to and in
front of the plantaris muscle. It next passes between the popliteus
muscle and the joint capsule, and afterwards between this muscle and

the proximal part of the tibia. It ends, under cover of the popliteus
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THE LIMBS OF THE HORSE 135
muscle, by dividing into two vessels of unequal size, the anterior and
posterior tibial arteries,

The collateral branches jof the popliteal artery are small, and dis-
tributed to the joint and the adjacent muscles.
V. POPLITEA—The popliteal vein lies medial to the artery of which
it is a satellite.

Lig. cruciatum anterius.
; °

/ M. flexor digitorum longus.

D- M. tibialis posterior.

- Lig. collaterale
fibulare.

iM. flexor hallucis
longus.

Fic. 91.—Posterior Aspect of the Tibia and Fibula, with Areas of Muscular and
Ligamentous Attachment.

1 and 2=Areas of attachment of ligamentous bands of the medial and lateral
menisci respectively.

A. TIBIALIS POSTERIOR.—The posterior tibial artery is the smaller
of the two vessels into which the popliteal divides. At first it lies
between the popliteus muscle and the tibia, and afterwards between
the flexor hallucis longus and the flexor digitorum longus. As far as
the middle of the tibia the artery is deep-seated, but, following the
posterior border of the tendon of the long flexor of the digit, it becomes
more superficial as the distal end of the tibia is approached. About
the level of the summit of the tuber calcanei the vessel ends by

dividing into the lateral and medial tarsal_arteries.
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136 TOPOGRAPHICAL ANATOMY OF

The branches of the posterior tibial artery are :—

(1) A. nutritia tibie.—The nutrient artery of the tibia leaves the
parent vessel as this emerges from beneath the popliteus muscle.

(2) Rami musculares—Numerous muscular branches are distributed
to the popliteus and the deep flexor muscles.

(3) A. tarsew lateralis—The lateral tarsal! artery is the smaller of
the two terminal branches of the posterior tibial. Passing between
the tibia and the combined tendon of the flexor hallucis longus and
tibialis posterior it gains the lateral aspect of the tarsus, over which
it ramifies. A slender twig, the recurrent tarsal artery (a. tarsea
recurrens), runs upwards on the lateral border of the tendo calcaneus,
and unites with a branch of the posterior femoral artery.

(4) A. tarsea medialis—The medial tarsal artery is so much larger
than the lateral vessel that it might be regarded as the true continua-
tion of the posterior tibial. Passing backwards from its point of
origin, the artery describes a double curve, with the first convexity
directed distalwards, and the convexity of the second curve looking in
a proximal direction. After the second curve has been formed the
medial tarsal artery follows the combined tendon of the flexor hallucis
longus and tibialis posterior to end, behind the tarsus, in the medial
and lateral plantar arteries.

Small branches of the medial tarsal artery are distributed over the
medial surface of the tarsus. A larger branch, the recurrent tibial
artery (a. recurrens tibialis), leaves the second convexity of the medial
tarsal and runs in a proximal direction along the medial border of the
tendo calcaneus, where it is related to the tibial nerve. It unites with
the saphenous and posterior femoral arteries.

Dissection.—The dissection of the anterior tibial and fibular regions
should be combined with that of the dorsum of the metatarsus and
digit. The combined dissection, while not being too complicated, per-
mits of a connected view of the muscle and tendons of this part of the
limb.

During the removal of the tarsal fascia certain specialised bands
(transverse ligaments) should be retained in position. One of these
will be found a short distance proximal to the end of the tibia. By
the attachments of its extremities to the bone it forms a ring through
which the tendons of the extensor digitorum longus, tibialis anterior,
and peronzus tertius play. Another band crosses the tendon of the
long digital extensor just beyond the joint between the tibia and the
talus. One extremity of this transverse ligament is attached to the
calcaneus; the other blends with the lateral limb of the peronzus
tertius tendon of insertion.

A third very definite transverse ligament has its ends attached to

1 Tarsus [L.], tapos (tarsos) (Gr.], any broad, flat surface ; for example, the
flat of the human foot.
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THE LIMBS OF THE HORSE 137

the third and fourth metatarsal bones, and crosses the tendons of the

extensor digitorum longus and peroneus longus.

A fourth and less definite transverse ligament retains the tendon of
the peroneus longus in the groove on the surface of the lateral
malleolus.

The muscles in the region now being examined are five in number,
namely, extensor digitorum longus, tibialis anterior, peronzeus longus,
peroneus tertius, and extensor digitorum brevis. Two of these—
peronzeus tertius and tibialis anterior—are so blended as to lead the
uninstructed to assume that they form one muscle only.

M. EXTENSOR DIGITORUM LONGUS.—The long digital extensor arises
from the depression on the femur between the patellar surface and the
lateral condyle by a strong tendon that is common to this muscle
and the peroneeus tertius. The tendon of origin traverses the muscular
notch lateral to the tuberosity of the tibia, and is succeeded by an
elongated, spindle-shaped belly’ that extends into the distal third of
the leg. From this point a flattened tendon, held in position by the
three fascial bands (transverse ligaments) mentioned above, crosses the
flexor aspect of the tarsus, where it is provided with a synovial sheath,
and travels along the dorsal aspect of the metatarsus and digit to be
inserted to the extensor process of the third phalanx. In the proximal
third of the metatarsus the tendon is joined by the extensor digitorum
brevis and the tendon of the peronzus longus. Otherwise its con-
nections and general disposition resemble those of the tendon of the
common digital extensor of the thoracic limb (q.v.).

M. PERONaUS LONGUS.—The long peroneal is the most lateral
muscle of the leg, and follows the line of the fibula between the
muscle just described and the flexor hallucis longus. Its origin is from
the lateral (fibular) collateral ligament of the femoro-tibial joint, the
fibula, and the interosseous ligament between the tibia and the fibula.
The tapering fleshy belly gives place to a rounded tendon, which passes
along the groove on the lateral malleolus and through a sheath on the
lateral aspect of the tarsus. About the junction of the proximal and
middle thirds of the metatarsus the tendon joins that of the long
digital extensor at an acute angle.

M. EXTENSOR DIGITORUM BREVIS.—The short extensor of the digit
is a small, pale, flattened muscle occupying the angle formed by the
converging tendons of the long extensor and long peroneal muscles.
Its origin is from the lateral limb of the tendon of insertion of the
peronzus tertius and the lateral (fibular) collateral ligament of the

tarsus.

1 This muscle is also known as the lateral digital extensor, a proceeding which

is permissible on account Hhatagty ppmolesy., ®

138 TOPOGRAPHICAL ANATOMY OF

Dissection.—Reflect the extensor digitorum longus by cutting across
the middle of its fleshy belly. The three transverse ligaments which
hold the extensor tendons in position should also be cut through, in
order that the long extensor tendon may be turned aside from the
flexor aspect of the tarsus. Care must be exercised not to injure the
vessels and nerves related to the extensor longus tendon.

M. PeROoN&ZUS TERTIUS.—Though this is called the third peroneal
muscle, there is some reason to question whether it actually corre-

M. extensor digitorum longus. --- -.+-M. tibialis anterior.

Siren V. saphena,

M. peronieus tertius. -

A. tibialis anterior. . 1,

M., peronzus tertius. =

5 Za MM. tibialis anterior.

Perforating tarsal artery and vein.
A. dorsalis pedis. -
M. extensor digitorum brevis.

w———- V. metatarsea dorsalis medialis.

M. peroneus longus. ---—---

Fic. 92.—Dissection of the Dorsal (Anterior) Aspect of the Tarsal Region.

1, 2, 3=Transverse ligaments that retain the extensor tendons in position.

sponds to the human muscle of this name. Its structure is noteworthy,
inasmuch as it is almost entirely tendinous. Functionally, therefore,
it is reasonable to assume that the muscle serves a purely mechanical
purpose. Doubtless, in conjunction with the largely tendinous plan-
taris muscle at the back of the leg, it acts as a passive mechanical stay,
which relieves the other muscle of the leg of a considerable amount of
strain when the animal is in the standing posture. The peronzus
tertius also causes mechanical flexion of the tarsal joint when the
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THE LIMBS OF THE HORSE 139

femoro-tibial joint is flexed, just as the plantaris muscle effects
mechanically simultaneous extension of these joints.

The origin of the peroneus tertius is common to that of the long
digital extensor, namely, from the depression between the patellar
surface and the lateral condyle of the femur. The common tendon of
origin lies in the notch lateral to the tuberosity of the tibia, being here
furnished with a diverticulum from the synovial lining of the femoro-
tibial joint.

Opposite the extreme distal end of the tibia the tendon splits to
allow the passage of that of the anterior tibial muscle, and then divides
into three limbs that are attached as follows: The lateral limb is
inserted to the calcaneus and the fourth tarsal bone (cuboid), and
with it is associated one end of middle transverse ligament; the
middle limb is connected with the third metatarsal bone; while the
medial limb is attached to the third tarsal bone (lateral cuneiform)
and the proximal end of the second and third metatarsal bones.

M. TIBIALIS ANTERIOR.—The anterior tibial muscle lies between the
long digital extensor and the peronzus tertius on the one hand, and
the tibia on the other. Its origin is from the proximal part of the
lateral surface of the tibia and the adjoining part of the fibula. In the
middle of the leg it is intimately connected with the peronzus tertius.
A strong tendon begins before the tarsus is reached, pierces the cleft
in the tendon of the peronzus tertius, and then divides into two limbs.
The lateral of these ends on the proximal end of the third metatarsal
bone along with the middle slip of the tendon of the peronzus tertius.
The medial limb, commonly called the “cunean tendon” in books
dealing with surgery, takes an oblique course to reach the combined
first and second tarsal bones (medial cuneiform) and the base of the
second metatarsal bone.

THE SYNOVIAL SHEATHS (VAGINS MUCOS#) OF TENDONS. — The
present is a convenient time at which to review the various synovial
burse and sheaths associated with the tendons in the region of the
tarsus. The sheaths and burse in the more distal part of the limb are
similar to those belonging to the tendons of the thoracic limb (9.v.).

An extensive bursa lies between the tendons of the gastrocnemius
and plantaris from the point (about the junction of the third and distal
fourths of the tibia) at which these tendons twist round each other to
the level of the middle of the tarsus. A very much smaller bursa lies
anterior to the point of insertion of the gastrocnemius tendon to the

tuber of the calcaneus.
Where the combined tendon of the flexor hallucis longus and

tibialis posterior lies ju. the, canal, behind the tarsus it is surrounded

140 TOPOGRAPHICAL ANATOMY OF

by a long synovial sheath, which has its proximal limit slightly higher
than the level of the summit of the tuber of the calcaneus (3 to 7 cm.
proximal to the medial malleolus), and its distal limit about the
junction of the first and second fourths of the metatarsus. A sheath

Patella.

M. vastus medialis. --—

Femur. -—

M. sartorius. ——

V. poplitea. -

i)
1
1
Saphenous vessels and } M. biceps femoris.

nerve.

A. poplitea.
M. plantaris.
M.semimembranosus. - =

M. gracilis.

Distal muscular brauch -
of n. tibialis.

. : &
Descending branch of ~
a. femoris posterior.

ee ee N. peronzeus communis.
N. tibialis, - p
M. semitendinogus. N. cutaneus suree posterior. M. gastrocnemius.

Fic. 98.—Section across the Pelvic Limb at the Level indicated by N in Fig. 81.

of very similar extent clothes the tendon of the flexor digitorum longus
as it traverses the canal provided for it by the medial collateral
ligament of the tarsus. Although the two sheaths connected with the
tendons of the deep flexor terminate at the same level and close
together, they are entirely independent of each other. It is noteworthy
also that, close to the medial malleolus, they are separated from each
other by a pouch of the joint capsule of the talo-crural articulation.
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THE LIMBS OF THE HORSE 141

The synovial sheath of the extensor digitorum longus begins slightly
above the lateral malleolus, and extends over the tarsus and into the
proximal third of the metatarsus. A sheath of very similar extent, but
beginning at a rather more proximal point, surrounds the tendon of the
peronzeus longus as it passes down the groove on the lateral malleolus
and obliquely over the tarsus. Since the tendons of the extensor
digitorum longus and peronus longus converge and join, their syno-

Ligamenta patellic.. é

~Yy : :
1 cee
| Bw
‘

_-Mm. peronzeus tertius et
gt extensor digitorum longus.

Lig. collaterale tibiale. hag

4. V. poplitea.
~—-A. poplitea.

Saphenous vessels and.
nerve. ae

_N. peronus communis.

_M. plantaris,

N. tibialis ——
-M. biceps femoris.

M. semitendinosus,____ &

i.
~ N. cutaneus sure
posterior.

.
M. gastrocnemius.

Fre. 94.—Section across the Proximal Part of the Leg at the Level indicated by O in Fig. 81.

vial sheaths necessarily also converge distally; but there is no union
between them.

A synovial sheath of limited extent surrounds the tendon of the
tibialis anterior as it passes between the two limbs of the peronzus
tertius, and a small bursa lies under its medial tendon of insertion.

N. PERON.ZUS COMMUNIS.—The origin of the common peroneal nerve
from the sciatic, and its course down the thigh in company with the
tibial nerve, have already been noted. Its passage between the biceps
and the lateral head of the gastrocnemius brings it to a superficial
position on a level with the head of the fibula, where it divides into

the superficial and deep eroneal nerves. The collateral branches of
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142 TOPOGRAPHICAL ANATOMY OF

the common peroneal nerve are: (1) To the biceps muscle; (2) a
filament which joins the posterior cutaneous sural nerve; and (3) the
anterior cutaneous sural nerve. The last named has been examined
already.

N. PERON.EUS SUPERFICIALIS.—The superficial peroneal nerve is the

M. peroncus tertius.

7
NNN a
\ # iy M., extensor digitorum longus.
ie
7
M. tibialis anterior, S #
Ps x
Y Ie y
S = ie ee
at Z arg
x 7
* , ee
‘ /
“
EX
er"
iy ao ap
ee <e : EE ats _.N. peronus profundus.
Tibia. eee cue eee », ( ee = ~A. tibialistanterior
Tk aoe y » ; -N. peronzus super-
V. tibialis anterior. 3 wth == -----~----- Sy --4 : ficialis.
| OF SI SAN ESTs oS ae a Fibula,
\ » 4 >
A $F .
A . Pes ‘Sa Evens M. pereneeus longus.
s ied
i t ge s j
Ce ee ye eg Ne M. flexo hallucis
longus.
N.saphenus. -
V. saphena. --
A, tibialis posterior. -~
M. soleus.

M. popliteus. -—

N. saphenus. a ;
A. saphena. ~M. tibialis posterior.

M., flexor digitorum longus. ~~

wo qe —— V. tarsea recurrens.

ae
S\N. cutaneus sure
SE / hb \ g posterior.
N, tibialis. ~ y af fy ve A

#
M. plantaris. M. gastrocnemius.

Fig. 95.—Section across the Leg at the Level indicated by P in Fig, 81.

smaller of the two terminal branches of the common peroneal. It
crosses very obliquely the surface of the peroneus longus muscle, to
which it furnishes a branch, runs down the groove between the
peroneeus longus and the extensor digitorum longus, and ends in the
skin over the anterior and lateral surfaces of the leg, tarsus, and

metatarsus,
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THE LIMBS OF THE HORSE 143

N. PERONUUS PROFUNDUS.—The deep peroneal nerve crosses the
proximal part of the long peroneal muscle, sinks into the interval
between this muscle and the extensor digitorum longus, and early
expends a considerable amount of its fibres in the supply of branches
to these muscles and the tibialis anterior. The much reduced continua-
tion of the nerve runs down the groove formed by the lateral border

M. extensor digitorum longus.

M. peroncus tertius. _____A
M. tibialis anterior.— — - //

A. tibialis anterior.
V. tibialistanterior,
N. peroneus profundus.

Fibula.

+ M.[peronccus longus.

- M. flexor hallucis longus.

A. tibialis posterior._ —

V. tibialis posterior.. -—

M. flexor digitorum longus..--~ ~ M. tibialis posterior.

~. V. tarsea recurrens,

tad
V. recurrens tibialis.-~

Me
N, tibialis, ’ .N. cutaneus sure posterior.

aad 2
~~_M. gastrocnemius.

all
M. plantaris. ~

Fic. 96.—Section across the Leg at the Level indicated by Q in Fig. 81.

of the long extensor and the anterior tibial muscles, and then follows
the lateral border of the long extensor to the flexor aspect of the tarsus,
where it divides into medial and lateral branches.

The medial branch (ramus medialis) runs obliquely down the dorsal
surface of the metatarsus, and ends in the skin over the dorsal and
medial aspect of the metatarso-phalangeal joint. The lateral branch
(ramus lateralis) supplies the extensor digitorum brevis, passes under-

neath the tendon of the peronzus longus in company with the lateral
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144 TOPOGRAPHICAL ANATOMY OF

dorsal metatarsal artery, and ends in the skin over the lateral surface
of the first phalanx.

A. TIBIALIS ANTERIOR.—The anterior tibial artery is the larger of
the two terminal branches of the popliteal. By piercing the inter-
osseous membrane between the fibula and the tibia the artery gains
the lateral surface of the latter bone, along which it runs towards the

M. peroneus tertius. M. extensor digitorum longus.

--N. peronzus profundus.

ax
ee A -V. tibialis anterior.

V. tibialis anterior. __£

V. saphena.
\_44
ait Set 4 A. tibialis anterior.
Pal OSB a,
iY
Tibia. :
My ‘crm ee ° - M. peronzeus longus.

SS- —M. flexor hallucis longus.
Y. tibialis posterior.
M. flexor digitorum - ss
longus.

A. tibialis posterior. --EB*— ee Se M. tibialis posterior.

S

N. recurrens tibialis. -- ‘i
ig . tarsea recurrens.

cutaneus sure posterior.

y
A. recurrens tibialis.
N. tibialis.

~~-=~.M. gastrocnemius.

M. plautaris. ~~

Fie. 97.—Section across the Leg at the Level indicated by R in Fig. 81.

tarsus under cover of the anterior tibial muscle. It should be noted
that it is only when the tarsus has very nearly been reached that the
anterior tibial artery and the deep peroneal nerve come into relation
with each other.

The collateral branches of the anterior tibial artery are: (1) A.
peroned, a small and not very constant branch that leaves the parent
early, descends along the fibula, and supplies twigs to the flexor
hallucis longus, peronaeus longus, and tibialis anterior. (2) Rami

musculares are furnished to the muscles on the lateral aspect of the
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THE LIMBS OF THE HORSE 145

tibia. (3) Rami articulares are expended in the ligaments of the
tarsus.

Opposite the joint, between the tibia and the talus, the anterior
tibial artery changes it name to that of the dorsal artery of the pes (a.

M. tibialis anterior. M, peronvcus tertius.
oe

-M. extensor digitorum longus.

ne peropens pro-
gees undus,

Y. saphena.
N

——-V. tibialis anterior,

Tibia —~-A. tibialis anterior,
1 oT

-M. peronzeus longus.

M. flexor digitorum -
longus.

A. tibialis posterior.__

=}--M. flexor digitorum

V. recurrens tibialis, _— profundus.

N. plantaris medialis, -. —

A. tarsea medialis. .-~~

N. plantaris lateralis. --~~

—Calcaneus.

--—M. gastrocnemius.
M. plantaris, --_.--

Fic. 98.—Section across the Most Distal Part of the Leg at the Level indicated
by S in Fig. 81.

The irregular black area behind the tibia is the upward extension of the
talo-crural (hock) joint-cavity.

dorsalis pedis). This vessel crosses the tarsus obliquely, mainly under
cover of the tendon of the extensor digitorum longus, and, on reaching
the base of the third metatarsal bone, becomes the lateral dorsal meta-
tarsal artery. The dorsalis pedis gives off the large perforating tarsal
artery (a. tarsea perforans) that, traversing the canal formed by the
third (cuneiform) and fourth (cuboid) tarsal and the central (scaphoid)

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146 TOPOGRAPHICAL ANATOMY OF

bones, reaches the back of the tarsus, where it will be examined in
connection with the vessels of the metatarsus.

The lateral dorsal metatarsal artery (a. metatarsea dorsalis lateralis)
passes obliquely over the lateral aspect of the base of the third meta-
tarsal bone underneath the extensor digitorum brevis and the tendon
of the peronzeus longus, and then travels along the groove formed by

M, peroneeus tertius. M. extensor digitornm longus.

M. tibialis anterior.~ _

A. dorsalis pedis, —.
V. saphena. ._

Lig. collaterale tibiale.

M. peronzeus
longus.

i Lig. collaterale
fibulare.

+- Talus.

oe —
M. flexor digi- ~
torum longus.

M. flexor digitorum profundus. a
Nn. plantares. -—

=} - — - Lig. tarsi plantare.

SJ. —--M. plantaris.

a
V. metatarsea plantaris. -“
superficialis lateralis.

A. tarsea medialis.

Fic. 99.—Section across the Tarsus at the Level indicated by Tin Fig. 81.

the union of the third and fourth metatarsal bones. Near the distal
end of the latter it passes between the two bones to reach the plantar
aspect of the metatarsus, where it will be met with later under the
name of the common digital artery.

V. TIBIALIS ANTERIOR.—The anterior tibial vein is frequently double,
one vein lying on each side of the homonymous artery. Its main
radicle of origin is the deep medial plantar metatarsal vein, which
accompanies the perforating tarsal artery in its passage through the
tarsus. The anterior tibial and saphenous veins are conneabed by a
large communicating vessel.

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THE LIMBS OF THE HORSE 147

ar Dissection.—The plantar aspect of the pes—tarsus, metatarsus, and
digit—now remains to be examined. After the skin has been removed,
it will be found that the arrangement of the fascia is similar to that of
the thoracic limb (¢.x.).

M. FLEXOR DIGITORUM BREvIS.—In the dissection of the leg the
plantaris tendon was found to be flattened where it plays over the
summit of the tuber calcanei, and to be attached by slips to the sides
of the tuber. From this point the tendon appears to be continued down

M. extensor digitorum longus.

A. dorsalis pedis.
M. tibialis anterior. ¢
Se

Lig. collaterale _

tibiale. _-M. peronzeus longus.

Central tarsal bone_
scaphoid).

-Fourth tarsal bone
(cuboid).

——Lig. tarsi plantare.

oe x
M. flexor digitorum longus, ~ —-~~—.M. flexor digitorum

profundus.

a ' ‘M. plantaris. ae

A. tarsea medialis,

ee

|
Callosity.

Nn. plantares.

Fie. 100.—Section across the Tarsus at the Level indicated by U in Fig. 81.

the back of the metatarsus; but there is good ground for supposing
that the short flexor of the digit has lost its muscular tissue and has
become continuous with the extremity of the plantaris tendon. The
long, flattened continuous tendon thus produced comports itself exactly
as does the metacarpal portion of the superficial flexor tendon of the
thoracic limb (¢.v.).

M. FLEXOR DIGITORUM PROFUNDUS.—<As has been seen, the strong,
rounded tendon produced by the union of the flexor hallucis longus and
tibialis posterior immediately proximal to the end of the tibia traverses
the grooved posterior surface of the calcaneus, where it is bound down
by a stout ligamentous band, and thence continues down the back of the

. In th imal third of this region it is joined by the
metatarsua, ln the prpvoiiced by Microsone> d A

148 TOPOGRAPHICAL ANATOMY OF

rounded tendon of the flexor digitorum longus, and, about the same
level, also by a relatively slender caput tendinewm arising from the
ligaments of the plantar aspect of the tarsus. From this point
onwards the tendon is disposed and terminates in a manner comparable
to that of the deep flexor tendon of the thoracic limb (g.v.).

MM. INTEROSSEI; MM. LUMBRICALES.—The interosseus and lumbrical

M. gastrocnemius.

_ Mm. plantaris, biceps femoris et semi-
tendinosus.

Tuber caleanei. ___
Talus
\

M. peronieus tertius. _______/._._ 7FemR

Fourth tarsal bone (cuboid). ------

--- Third tarsal bone (cuneiform).

-- Mm. peronceus tertius et tibialis
anterior.

Fourth metatarsal bone. ---\-----+

Third metatarsal bone.

Fic. 101. —Lateral Aspect of the Tarsus, with Areas of Muscular Attachment.

muscles are the same in number and disposition as the like-named
structures of the metacarpus.

NERVES OF THE METATARSUS AND DIGIT.—At the distal end of the
leg the tibial nerve divides into the medial and lateral plantar nerves
(nu. plantaris medialis; n. plantaris lateralis). These, at first, lie close
together on the surface of the combined tendon of the flexor hallucis
longus and tibialis posterior; but, before the metatarsus is reached,
the lateral nerve passes obliquely between the superficial and deep
flexor tendons, and thus arrives at the lateral border of the deep

tendon. The medial and lateral nerves follow the medial and lateral
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THE LIMBS OF THE HORSE 149

borders respectively of the deep flexor tendon, and behave in the
Same manner as the volar nerves of the thoracic limb. The oblique
anastomotic branch from the medial to the lateral nerve is always
smaller than that in the metacarpus, and is frequently absent alto-
gether.

ARTERIES OF THE METATARSUS AND DIGIT.—The medial tarsal artery
(a. tarsea medialis), the larger of the two terminal branches of the

M. gastrocnemius.

-~.Mm. plantaris, biceps femoris et semi-
tendinosus.

M. peronzeus tertius. -
~ Central tarsal bone

Fourth tarsal bone (cuboid), -- (scaphoid).

Third tarsal bone (cunei-
form).

_>M. peronzeus tertius.

7 ~ Min. peronieus tertius et tibialis

Third metatarsal bone.
anterior,

w—-4t-}- 4,

Fic. 102.—Dorsal (Anterior) Aspect of the Tarsus, with Areas of Muscular Attachment.

posterior tibial, has already been observed to produce a double curve
on a level with the summit of the tuber calcanei, and the origin
of the recurrent tibial artery from the convexity of the second curve
has also been noted. After the formation of the second curve the
medial tarsal artery proceeds in a distal direction upon the deep
flexor tendon in company with the plantar nerves. Just before the
base of the metatarsal bone is reached the vessel divides into the
medial and lateral plantar arteries (a. plantaris medialis; a. plantaris
lateralis).

Of the two plantar arteries the lateral is the larger, and follows the

lateral plantar nerve (posterior to the nerve) along the border of the
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150 TOPOGRAPHICAL ANATOMY OF

deep flexor tendon. It ends by joining either the common digital
or the lateral plantar digital artery.

The slender medial plantar artery follows the medial plantar nerve,
and ends in the same manner as does the lateral artery. In the
proximal part of the metatarsus it is generally united to the medial
plantar metatarsal artery by a communicating branch.

Occasionally the two plantar arteries unite in the distal part of the

M. gastrocnemius.

Mum. plantaris, biceps femoris et semi- ~—-_~
tendinosus.

ae ; Tuber calcanei.

Sustentaculum tali.

Central tarsal bone (scaphoid). ~___ j Yr-~—- M. tibialis anterior.

. First tarsal bone.

Third tarsal bone. --__
ve ? - Second tarsal bone.

- M. peronus tertius.

Mn .*peroneus te rtius et —-~-|
tibialis anterior.

---- Second metatarsal hone.

Third metatarsal bone, ~-__

Fic. 103.—Medial Aspect of the Tarsus, with Areas of Muscular Attachment.

metatarsus and form a single vessel that joins one of the plantar
digital arteries.

The perforating tarsal artery (a. tarsea perforans) has been seen to
enter a canal formed by the tarsal bones. It reappears on the
plantar aspect of the tarsus about the line of junction of the bases of
the second and third metatarsal bones. Immediately on its reappear-
ance it is joimed to the lateral plantar artery (possibly to the medial
plantar artery also) by a communicating branch. Thus is formed the
proximal plantar arch (arcus plantaris proximalis) from which the

medial and lateral plantar metatarsal arteries arise. The plantar
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THE LIMBS OF THE HORSE 151

metatarsal arteries, of which the medial is the larger, run down the
metatarsus in the depths of the grooves formed by the middle inter-
‘osseous muscle and the small metatarsal bones, and end by uniting
with the common digital artery, thus forming the distal plantar arch
(arcus plantaris distalis). The medial artery furnishes the nutrient
vessel for the third metatarsal bone.

On its passage between the third and fourth metatarsal bones
the lateral dorsal metatarsal becomes the common digital artery

M. gastrocnemius, -— ~~

Tuber calcanei.

=e

Talus. -__

Sustentaculum tali. --.j--{---.

Central tarsai bone _
(scaphoid).

M. tibialis anterior. ((/ __
First tarsal bone. 4 ae

Second tarsal bone. ._

-. Fourth tarsal bone (cuboid).

_-. M. flexor digitorum profundus.

‘

Wire rN
Ny

Second metatarsal bone. ._ ein ~— Fourth metatarsal bone.

—- rt 4- M. interosseus.

Third metatarsal bone. . ee:

J

Fic. 104.—Plantar (Posterior) Aspect of the Tarsus, with Areas of Muscular Attachment,

(a. digitalis communis), which traverses the gap between the two
limbs of the interosseous muscle and, between this and the deep
flexor tendon, divides into the medtal and lateral plantar digital
arteries. The digital arteries have a distribution similar to that
of the corresponding vessels of the thoracic limb.

VEINS OF THE METATARSUS AND Dicit.—The plexuses and veins
of the digit are similar to those of the thoracic limb, the two digital
veins, medial and lateral, being joimed in the formation of a distal
plantar venous arch (arcus venosus plantaris distalis). .

There may be six veins in the metatarsus, but of these three are
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152 TOPOGRAPHICAL ANATOMY OF

small and not always present. The largest of the six is the medial
dorsal metatarsal vein (v. metatarsea dorsalis medialis), which begins at

M, extensor digitorum longus.

A ___M. extensor digitorum
brevis.

M. peronzus longus.

N. peroneus profundus.

A. metatarsea dorsalis
lateralis.

+ - Third metatarsal bone.

Second metatarsal bone. -. Fourth metatarsal bone.

. M. interosseus.
#.- A. plantaris lateralis.
A. tarsea perforans.
M. flexor digitorum longus. ee
N. plantaris medialis. “

A. plantaris medialis. M., flexor digitorum profundus.
Fic, 105.—Section across the Proximal End of the Metatarsus at the Level indicated
by V in Fig. 81.

the venous arch, follows the medial border of the interosseous muscle
for about two-thirds of the length of the metatarsus, and then crosses

M. extensor digitorum longus.
/

Third metatarsal bone.

Second metatarsal bone.-
V. metatarsea dorsalis medialis.-
M. interosseus.

WN. peronieus profundus.
. A. metatarsea dorsalis lateralis.

- Fourth metatarsal bone.

A. plantaris medialis.
N. plantaris medialis. —A. plantaris lateralis.
_ N, plantaris Jateraiis.

+ — M. flexor digitorum profundus.

_— M. plantaris.

Fic. 106,—Section across the Metatarsus at the Level indicated by W in Fig. 81.

the medial aspect of the limb to form the main radicle of the

saphenous vein. The lateral dorsal metatarsal vein (v. metatarsea
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THE LIMBS OF THE HORSE 158

dorsalis lateralis) is small, and may be absent. When present, it is
a satellite of the like-named artery. There is often a small middle
dorsal metatarsal vein (v. metatarsea dorsalis media) that joins either
the medial dorsal metatarsal or the saphenous vein.

The lateral superficial plantar metatarsal vein (v. metatarsea plan-
taris superficialis lateralis) begins at the venous arch, ascends along
the lateral border of the deep flexor tendon in front of the plantar
nerve, and is continued as the recurrent tibial vein. A medial
superficial plantar metatarsal vein (v. metatarsea plantaris superfici-
alis medialis) may be present, but, if so, is very small. It follows
the medial border of the deep flexor tendon, and joins either the
lateral superficial or the deep plantar metatarsal vein.

M. extensor digitorum longus.

Third metatarsal bone.

A. digitalis plantaris
medialis. A. digitalis plantaris
lateralis.

M., interosseus.. 5
M. interosseus.

V. digitalis medialis. -_& V. digitalis lateralis.

N. plantaris lateralis.
N. plantaris medialis. -~

“S~M. flexor digitorum
profundus.

M. plantaris.
Fic. 107.—Section across the Metatarsus at the Level indicated by X in Fig. 81.

The deep plantar metatarsal vein (v. metatarsea plantaris profunda
medialis) begins at the venous arch, passes between the two limbs of
the interosseous muscle, and ascends between this structure and the
third metatarsal bone, to be continued as the perforating tarsal vein
(v. tarsea perforans), which pierces the tarsus along with the homonymous
artery.

Near the proximal end of the metatarsus the deep and lateral
superficial plantar veins are connected by a transverse branch, and thus
the deep plantar arch (arcus plantaris profundus) is formed.

THE FEMORO-PATELLAR AND FEMORO-TIBIAL ARTICULATIONS (articulatio
genu).—These two articulations, taken together, correspond to the knee-
joint of man, and, in the horse, are generally referred to by the collective

name of the “ stifle join py ieddbppebiths adaptation of the bony surfaces

154 TOPOGRAPHICAL ANATOMY OF

is indifferent, the joint, in virtue of the character and number of its
ligaments, is of considerable strength.

Before examining the joint itself the dissector should obtain
specimens of the bones that form it and study the articular surfaces.
If he does this, he will observe that, though the articular face of the
patella is, in general, the reverse of the patellar, surface of the femur,
the opposed surfaces are not capable of accurate and complete applica-
tion. Nor is the transverse diameter of the patella equal to that of the
patellar surface of the femur. In the recent and unmacerated bone,
however, a complementary piece of cartilage is attached to the medial
angle of the base of the patella, and moulded upon the large medial lip
of the pulley-shaped patellar surface of the femur. If the dissector
glides the patella over the patellar surface of the femur he will find
that different portions of the one come into successive contact with
different portions of the other.

The condyles of the tibia are very ill-adapted for the reception of
the condyles of the femur: the opposed bony surfaces are decidedly
incongruent.

Dissection.—Remove the remains of the muscles about the joint, but
leave the tendons of origin of the popliteus, long extensor, and peronzus

tertius muscles. Clean the surface of the joint-capsules, and define the
collateral and patellar ligaments.

THE FeMonro-PATELLAR ! ARTICULATION (articulatio femoro-patellaris).
—The joint-capsule (capsula articularis) is roomy, and attached, on the
one hand, to the margin of the articular surface of the patella and, on
the other, to the femur along a line about 2 or 3 cm. from the edge of
the patellar surface. The distal part of the capsule meets that of the
femoro-tibial joint, and, generally, the two joint cavities communicate
with each other by one or, possibly, two narrow slit-like openings. In
the region where the two capsules meet there is a considerable accumu-
lation of fat. The proximal part of the femoro-patellar capsule is pro-
longed beyond the base of the patella, as a tri-locular diverticulum,
between the extensor quadriceps muscle and the anterior surface of the
femur, a pad of fat separating the muscle from the capsule.

The jemoro-patellar ligaments (ligamenta femoro-patellaris), medial
and lateral, may be regarded as thickenings of the joint-capsule, with
which they are most intimately connected. The lateral band is the
stronger, and passes from the femur to the lateral angle of the base
of the patella. The weaker medial ligament also has one extremity
attached to the femur, the other being connected with the cartilaginous
extension of the patella.

' Patella [L.], dim. of patina or patera, a pan, dish, or plate.
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THE LIMBS OF THE HORSE 155

The three, slightly converging, patellar ligaments (ligamenta patel)
correspond to the single ligament of man and the dog. The lateral and
middle ligaments spring from the lateral and distal angles respectively
of the patella. The medial ligament is connected with the patellar
supplementary cartilage. The distal attachment of each band is to the
tuberosity of the tibia, the middle ligament being fixed to the distal
part of the groove-like depression of the tuberosity.

ie lateral ligament receives one of the insertions of the biceps

Femur.

M. gastrocnemius (caput
laterale).
M. biceps femoris.

Patella.
M. plantaris, _

_.Lig. femoropatellaris
laterale.

Uf. Ligamenta patella.

Wy iy _ Fascia lata.

(hen _. M. biceps femoris (part of insertion).
__ _Mm. extensor digitorum longus
et peronus tertins.

Fic. 108.—Lateral Aspect of the Femoro-Patellar and Femoro-Tibial Articulations,

The lines of attachment of the synovial linings of the joint-capsules are indicated in red.

muscle and part of the fascia lata, while the medial ligament receives
the conjoint aponeurosis of the sartorius and gracilis.)

The patellar ligaments, strictly speaking, represent the tendon of
insertion of the quadriceps muscle of the thigh, the patella being a
sesamoid bone developed therein.

THE FEMORO-TIBIAL ARTICULATION (articulatio femoro-tibialis)—A
roomy joint-capsule (capsula articularis), weak in front but strong behind
is attached to the articular margin of the tibial condyles and about
1 cm. from the margin of the condyles of the femur. Its fibrous layer
is also attached to the convex border of the interarticular cartilages

(medial and lateral mens yand tgyt 2 cruciate ligaments. The synovial

156 TOPOGRAPHICAL ANATOMY OF

layer clothes the cruciate ligaments in such a manner as to be divided
into two sacs. As previously stated, the joint-capsules of the femoro-
patellar and femoro-tibial articulations are in contact with each other
distal to the patella, but it must be noted that a considerable quantity
of fat separates the femoro-tibial capsule from the patellar ligaments.
On opening the joint-capsule it will be found that, because of its
fixation to the margin of the interarticular cartilages, each synovial sac

Femur.

Patella.

Supplementary cartilage
, of patella.

¢- M. adductor.

Y Ligamenta patellie.

_ Lig. collaterale tibiale.

Lig. collaterale fibulare.-Hlf it- - -3edial meniscus.

Mm. extensor digitorum longus yy i _ M. gracilis (part of insertion).

et perovzeus tertius.
M. biceps femoris_
(part of insertion).

Fibula. - -—.

take oe a2 edibles

Fre. 109.—Anterior Aspect of the Femoro-Patellar and Femoro-Tibial Articulations.

*= Ligamentous bands attaching the menisci to the tibia.
The lines of attachment of the synovial linings of the joint-capsules are indicated in red.

is partially separated into two parts communicating with each other
round the concave edge of the meniscus. The lateral sac covers the
tendon of origin of the popliteus muscle, and is continued down the
muscular notch of the tibia underneath the common tendon of origin of
extensor digitorum longus and peronzus tertius.

The medial (tibial) and lateral (fibular) collateral ligaments are
attached by one extremity to the condyles of the femur. The medial
ligament (ligamentum collaterale tibiale) is connected with the medial
meniscus, and ends on the medial condyle of the tibia. The longer and
stronger lateral collateral ligament (ligamentum collaterale fibulare) is

separated from the lateral meniscus by the tendon of the popliteus
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THE LIMBS OF THE HORSE 157

muscle, and ends on the head of the fibula. A small synovial bursa

intervenes between the ligament and the lateral condyle of the tibia.

Dissection.—Make a transverse incision through the femoro-patellar
capsule just proximal to the patella, and longitudinal incisions on each
side of the patella—through the capsule and the femoro-patellar liga-
ments—so that the bone, with its three ligaments intact, may be turned
downwards.

Now dissect away the femoro-tibial capsule and the accumulations
of fat, so that a clear view of the cruciate ligaments and the menisci
may be obtained.

M. gastrocnemius (caput mediale).
\ es

_ M. gastrecnemius

M. adductor. , (caput laterale).

ee M. plantaris.

---- Lig. cruciatum anterius.

VV fit -Lig. collaterale tibulare.
Medial meniscus. ~__ff i Tendon of m. popliteus.

1 Lateral meniscus.

Fic, 110.—Posterior Aspect of the Femoro-Tibial Articulation.

* Two ligamentous bands attaching the lateral meniscus to the femur and tibia.
The lines of attachment of the synovial linings of the joint-capsule are indicated in red.

The anterior cruciate ligament (ligamentum cruciatum anterius)
passes obliquely from the depression on the intercondyloid eminence of
the tibia to the medial face of the lateral condyle of the femur. The
postertor cruciate ligament (ligamentum cruciatum posterius) crosses the
medial surface of the anterior. It arises from the medial part of the
popliteal notch of the tibia and the adjacent part of the posterior inter-
condyloid fossa, An oblique course forwards and upwards carries
it to its point of fixation to the lateral face of the medial condyle of

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158 TOPOGRAPHICAL ANATOMY OF

The poor adaptation of the femoral and tibial condyles is partly
compensated by the presence of two crescentic, cartilaginous pads, the

Ligamenta patellw,

Lig. cruciatum
anterius.

'
Be. Lig. cruciatum posterius.

Fig. 111.—Proximal End of the Tibia, with Areas of Ligamentous Attachment.

1=Avrea of attachment of one of the ligamentous bands of the lateral meniscus.
2 and 2’= Areas of attachments of the ligamentous bands of the medial meniscus.

lateral and medial menasct (meniscus lateralis ; meniscus medialis), The
convex edge of each meniscus is thick ; while the concave border, directed

y7___--Tuberosity of the tibia.

-Lig. cruciatum anterius.

Lateral meniscus.

Intercondyloid eminence. ” 7 *
Lig. cruciatum posterius.

Fic. 112.—Proximal End of the Tibia, with the Ligaments and Menisci attached thereto,
*—Ligamentous bands holding the menisci in position.

towards the intercondyloid eminence of the tibia, is so thin as to be
translucent. The proximal (femoral) surface of each meniscus is concave
for the reception of one of the condyles of the femur. The distal or

tibial surface is flattened. Each meniscus is attached in front by a
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THE LIMBS OF THE’ HORSE 159

ligamentous band to an anterior intercondyloid fossa of the tibia.
Behind, the medial meniscus is fixed to the tibia by a ligament attached
to the posterior intercondyloid fossa. The lateral meniscus has two
posterior ligamentous attachments; one band is attached in the
popliteal notch, the other, crossing the posterior cruciate ligament
obliquely, ends on the medial condyle of the femur.

Dissection.—The articulation between the tibia and the fibula must
next be examined. The remains of all muscles attached to the fibula
and the adjacent part of the tibia must be cleaned away.

THE TIBIO-FIBULAR ARTICULATION (articulatio tibio-fibularis),—In
those animals in which the fibula! is developed throughout the whole
of its length two tibio-fibular joints—a proximal and a distal—are
present, and an interosseous membrane fills the gap between the two
bones of the leg. In the horse, a considerable portion of the fibula fails
to develop into bone, and the distal extremity fuses with the tibia.
A fibrous cord, joining the tapering end of the rudimentary shaft of the
fibula to the lateral malleolus, represents that portion of the bone which
has failed to develop.

A strong, short joint-capsule (capsula articularis) binds the head of
the fibula so closely to the lateral condyle of the tibia as to prevent
anything but the smallest degree of movement. Not infrequently the
capsule ossifies in old age. An interosseous membrane (membrana
interossea cruris) fills the space between the tibia and the fibula with
the exception of a short interval, close to the head of the fibula, through
which the anterior tibial vessels pass.

Dissection.—Remove all tendons, etc.,. from the neighbourhood of
the tarsus.

THE TARSAL ARTICULATIONS (articulationes tarsi)—The articulations
of the tarsus resemble those of the carpus in so far as they are
susceptible of a similar grouping. Unlike the carpal joints, however,
those of the tarsus—with one exception—are capable of very restricted
movement

The joints included in the tarsal articulations are: (1) The talo-
crural? articulation (articulatio talo-cruralis), between the distal end of
the tibia and the trochlea of the talus (tibial tarsal bone); (2) the inter-
tarsal articulations (articulationes intertarsea), between the rows of
tarsal bones; (3) the interosseous articulations (articulationes interossea),

1 Fibula [L.] [contraction of figebula, from figo, to fix or fasten], a clasp, pin,
buckle, or brace.

2 Talus [L.], the ankle-bone of animals ; an oblong die used for gaming (originally

made from the ankle-bone of certain animals), rounded on two sides and marked on

the other four. Crus [L.], the leg or shin. _
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160 TOPOGRAPHICAL ANATOMY OF

between the neighbouring bones of the same row; and (4) the tarso-
metatarsal articulation (articulatio tarso-metatarsea), between the distal
row of tarsal bones and the bases of the three metatarsals.

The ligaments of the tarsal articulations may be classified as (1)
those that are common to the whole series of articulations, and
(2) those that join two or more bones together. The common
ligaments consist of a joint-capsule and two collaterals,

Though it is customary to describe the fibrous layer of the foint-capsule
(capsula articularis) as extending from the distal end of the tibia to the
proximal end of the metatarsus, that portion of it associated with the
talo-crural joint is most definite and spacious. The rest of it is firmly
adherent to the free surfaces of the tarsal bones, and blends most
intimately with the collateral and other ligaments, as well as with
tendons inserted in the immediate neighbourhood. That part of the
capsule attached to the plantar (posterior) surfaces of the tarsal bones
is of great strength, and reinforced by a cartilaginous plate, which assists
in the formation of the smooth groove down which the deep flexor
tendon plays.

The synovial layer of the joint-capsule is divided into four sacs.
(1) The most capacious of these is between the tibia and the talus. On
the flexor (dorsal or anterior) aspect of the joint the membrane forms
a small diverticulum over the end of the tibia; and behind the joint,
that is, on its plantar or extensor aspect, there is a larger diverticulum
extending for a short distance (4 or 5 cm.) upwards between the tibia
and the tendon of the flexor hallucis longus. (2) The second synovial
sac is associated with the joint formed by the tibial tarsal (talus),
fibular tarsal (calcaneus), central (scaphoid), and fourth tarsal (cuboid)
bones. (3) The third synovial membrane belongs to the joint between
the central (scaphoid) and the bones of the distal row; (4) while the
fourth sac belongs to the tarso-metatarsal articulation.

The most powerful ligaments of the tarsus are those that extend
from the tibia to the metatarsus (the two collateral ligaments) and
those that pass from the proximal row of tarsal bones to the
metatarsus (dorsal and plantar ligaments).

The lateral collateral ligament (ligamentum collaterale fibulare
(laterale)) is composed of two strong bands, both of which arise from
the lateral malleolus. The more superficial and longer band is con-
nected with the talus, calcaneus, fourth tarsal (cuboid), and the third
and fourth metatarsal bones. The deeper, short ligament crosses the
foregoing obliquely to be attached to the talus and calcaneus.

The medial collateral ligament (ligamentum collaterale tibiale
(mediale)) has its origin from the medial malleolus, and is also divisible

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THE LIMBS OF THE HORSE 161

into two parts crucially disposed. ‘The long ligament is attached to the
talus, the first, second, and third tarsal (cuneiform), and the second and

Lig. talo-calcaneum posterius.

sTibia.
~ -- Groove for tendon of m.

Fibular tarsal bone- - peronzeus longus
gus.

(calcaneus).
i tuned laneae ~~ ~Lig. collaterale fibulare (deep).
~ ~Tibial tarsal bone (talus).

ee -Lig. collaterale fibulare (superficial),

“~ ~.Central tarsal bone (scaphoid),
~ — -. Third tarsal bone (cuneiform).

Fourth metatarsal bone. ___\--. |
|

Fic. 113.—Lateral Aspect of the Tarsal Articulations.

third metatarsal bones. The short ligament divides into two portions ;
one of which ends on the talus, while the other, somewhat longer, is
attached to the sustentaculum tali of the calcaneus.

Lig. collaterale fibulare (deep).

Lig. collaterale fibulare (superficial). _ ] .- Lig. collaterale tibiale (superficial).
Central tarsal bone (scaphoid). _ ;

Third tarsal bone (cuneiform). __

Fic. 114.—Dorsal (Anterior) Aspect of the Tarsal Articulations,

The dorsal tarsal ligament (ligamentum tarsi dorsale) is triangular

in outline, and consists of fibres diverging from the projection on the
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162 TOPOGRAPHICAL ANATOMY OF

medial surface of the talus. The ligament spreads out over the dorsal
surface of the central (scaphoid) and third tarsal (lateral cuneiform)
bones, to which some of its fibres are attached, and ends on the second
and third metatarsal bones.

The plantar tarsal ligament (ligamentum tarsi plantare) is strong,
and runs down the back of the tarsus under cover of the plantaris
tendon (strictly speaking, the modified flexor digitorum brevis) in the
form of a band that gradually widens and thickens. It begins on the
plantar (posterior) border of the tuber calcanei, is attached to the

4) Fibular tarsal bone
: (calcaneus).

-11-- Sustentaculum tali.

- -Lig. tarsi plantare.

Lig. collaterale tibiale_--~~
(deep).

a

Fic. 115,—Medial Aspect of the Tarsal Articulations,

central and the third and fourth tarsal bones, and ends on the bases of
the third and fourth metatarsals.

The individual tarsal bones are connected by numerous short liga-
ments, few of which can be regarded as of great moment. There are
four ligaments connecting the talus and calcaneus. (1) A proximal or
posterior talo-calcanean ligament (ligamentum talo-calcaneum posterius)
lies at the most proximal point of contact of the two bones. (2 and 3)
Lateral and medial ligaments (ligamenta talo-calcaneum laterale et
mediale) are attached to the lateral and medial surfaces respectively
of the two bones, and are mainly hidden by the collateral ligaments
of the joint. (4) An interosseus ligament (ligamentum talo-caleaneum
interosseum) passes between the two bones, and is attached to the
depressions between their articular facets.

A lateral and a plantar ligament join the calcaneus to the fourth
tarsal bone (cuboid). A dorsal ligament joins the calcaneus to the

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THE LIMBS OF THE HORSE 163

central tarsal bone (scaphoid), and a plantar ligament connects the
calcaneus and the combined first and second tarsal (cuneiform) bones.

The fourth tarsal bone is connected with the fourth metatarsal
bone by lateral, dorsal, and plantar ligaments, and a dorsal ligament
unites it with the central bone (scaphoid).

Dorsal ligaments pass between the central bone and the third
tarsal (cuneiform) bone, the fourth tarsal (cuboid) and the third tarsal
(cuneiform) bone, and between the combined first and second and the
third tarsal bones (cuneiform bones).

The following ligaments join the bones of the distal row to the
metatarsal bones. (1) A medial ligament connects the combined
first and second tarsal bones (medial cuneiform) with the metatarsus.
(2) A dorsal ligament passes from the third tarsal (lateral cuneiform)
bone to the third metatarsal. (3) A plantar ligament binds the com-
bined first and second tarsal bones (medial cuneiform) to the third
metatarsal. (4) An interosseous ligament passes from the third tarsal
(lateral cuneiform) bone to the third metatarsal.

In addition to those already mentioned, interosseous ligaments pass
between the following bones: From the talus and calcaneus to the
central and fourth tarsal bones, from the central to the third tarsal
bone (lateral cuneiform), from the central to the fourth tarsal bone
(cuboid), and from the fourth to the third tarsal bone.

It is clear that the disposition of numerous ligaments prevents
anything more than a small degree of gliding movement between the
individual tarsal bones. Free movement, on the contrary, takes place
in the talo-crural articulation. ‘From the nature of the opposed
articular surfaces of the talus and the tibia, flexion and extension only
are possible; and, because of the obliquity of the ridges on the talus,
the distal part of the limb is abducted to a certain extent during
flexion. >

The joints of the metatarsus and digit are similar to the correspond-
ing articulations of the thoracic limb.

Digitized by Microsoft® [ ARTERIES.

TOPOGRAPHICAL ANATOMY OF

164

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Digitized by Microsoft®

THE LIMBS OF THE HORSE

165

Nerve anD BLoop Suppty or THE Muscies or THE PELVIC Line.

Nerve Supply.

‘M. tensor
late.

‘alis.

Cranial gluteal . :

M. piriformis.

dus.

Caudal

selatic

gluteal and
M.

. gracilis.

. pectineus.

Obturator .

M. adductor.

nus.

Saphenous. ML. sartorius.

Femoral

M. vastus
medius.

M. capsularis.

Sciatic

nus.

| Min. gemelli.

Superficial peroneal

fasciee
M. gluteus supertici-

M. gluteus medius.

M. gluteus profun-
M. biceps femoris.

semitendinosus.

M. obturator exter-

M. rectus femoris.
M. vastus lateralis.

AML. vastus medialis.

inter-

' M. semimembranosus.

M. quadratus femoris.

M. obturator exter-

M. peronzus longus.

Blood Supply.

Civeumflex iliac, ilio-lumbar, and
lateral circuniflex.

Cranial gluteal, caudal gluteal, and
lateral circumflex.

Cranial gluteal, lateral circumflex,
ilio-lumbar, and luinhar.

Cranial gluteal.

Cranial gluteal.

Caudal gluteal, obturator, posterior
femoral, and deep femoral.

Caudal gluteal, obturator, posterior
femoral, and deep femoral.

Femoral, deep femoral, and saphen-
ous.

Femoral, and deep femoral.

Femoral, obturator, deep femoral,
and posterior femoral.

Deep femoral, and obturator.

Femoral, and saphenous.

Femoral, anterior and

lateral circumflex.

femoral,

Lateral circumflex,

and posterior
femoral.

Anterior femoral, femoral, and

articular branch of femoral.

Anterior femoral, and lateral cir-
cumflex.

Lateral circumflex.

Femoral, obturator, caudal gluteal,
and posterior femoral.

Deep femoral, and obturator.

Internal pudendal, and obturator.

Obturator.

Anterior tibial.

Digitized by Microsoft®

166 TOPOGRAPHICAL ANATOMY OF LIMBS OF HORSE
Nerve Supply. Blood Supply.

‘M. extensor digi- Anterior tibial.
torum longus.
M. peroneus tertius. Anterior tibial.
Deep peroneal ‘ ; .
M. tibialis anterior. Anterior tibial.

M. extensor digi- Dorsalis pedis, and lateral dorsal

torum brevis. metatarsal.
M. gastrocnemius. Popliteal, and posterior femoral.
M. soleus. Posterior tibial.
M. plantaris. Posterior femoral, and recurrent
tibial.

|M. flexor digitorum Posterior tibial.
longus.

Tibial M. tibialis posterior. Posterior tibial.

M. flexor hallucis Posterior tibial.

longus.
M. popliteus. Popliteal, and posterior tibial.
Mm. lumbricales. Plantar metatarsals,
Mm. interossei. Plantar metatarsals.

Digitized by Microsoft®

INDEX.

ABDUCTOR pollicis, 38.
Accessory cephalic vein, 34.
Accessory ligament of the hip joint, 124.
Accessory nerve, 14.
Adductor muscle of the thigh, 98.
Anconeus muscle, 30.
Anterior circumflex
humerus, 24.
Anterior cutaneous sural nerve, 118, 127.
Anterior femoral artery, 10i.
Anterior tibial artery, 144.
Anterior tibial vein, 146.
Antibrachial cephalic vein, 34.
Antibrachial fascia, 34.
Arch—
deep plantar venous, 153.
deep volar arterial, 63.
distal plantar arterial, 151.
distal plantar venous, 151.
proximal plantar arterial, 150.
terminal, of digital arteries, 89.
volar venous, 65.
Arteria or Arterize—
arcus plantaris distalis, 151.
arcus plantaris proximalis, 150.
arcus terminalis, 89.
arcus volaris profundus, 63.
axillaris, 6, 21.
brachialis, 24.
cervicalis ascendens, 6.
circumflexa femoris lateralis, 120.
circumflexa femoris medialis, 106.
circumflexa humeri anterior, 24.
circumflexa humeri posterior, 22.
cireumflexa scapula, 23.
collateralis radialis, 24, 39.
collateralis ulnaris, 24, 49.
coronales phalangis tertiz, 89.
digitales plantares, 64, 151.
digitales volares, 64, 89.
digitalis communis, 64, 151.
dorsales phalangis tertiz, 89.
dorsalis pedis, 145.
femoralis, 101.
femoris anterior, 101.
femoris posterior, 104, 106.
genu suprema, 101.
gluteea caudalis, 114.
gluteea cranialis, 114.
interossea communis, 52.
interossea dorsalis, 39.
interossea recurrens, 40.
mediana, 52.

artery of the

167

Arteria or Arterize—continued.
metacarpea dorsalis lateralis, 64.
metacarpea dorsalis medialis, 64.
metacarpea volaris lateralis, 62.
metacarpea volaris medialis, 61.
metatarsea dorsalis lateralis, 146.
metatarsee plantares, 150.
nutritia femoris, 104.
nutritia humeri, 24.
nutritia radii, 40.
nutritia tibice, 136.
obturatoria, 105.
peronea, 144.
phalangis prima, 65.
plantares, 149.
poplitea, 134.
profunda brachii, 24, 39.
profunda femoris, 106.
profunda penis, 105.
recurrens tibialis, 136.
rete carpi dorsale, 40.
rete carpi volare, 53.
saphena, 96, 101.
subscapularis, 21.
tarsea lateralis, 136.
tarsea medialis, 136, 149.
tarsea perforans, 145, 150.
tarsea recurrens, 136.
thoracica externa, 6.
thoraco-acromialis, 21.
thoracodorsalis, 22.
tibialis anterior, 144.
tibialis posterior, 135.
torice phalangis tertiz, 65, 89.
transversa scapule, 1, 6.
truncus omocervicalis, 6.

Arteries of the metacarpus and digit, 61.

Arteries of the metatarsus and digit,

149.

Arteries of the pelvic limb, table, 164.

Arteries of the thoracic limb, table, 93.

Articular artery (of femoral), 101.

Articulation or Articulations—
carpal, 7].
carpo-metacarpal, 71.
distal interphalangeal, 91.
elbow, 69.
femoro-patellar, 153, 154.
femoro-tibial, 153, 155.
hip, 122.
humero-radial, 69.
humero-ulnar, 69.

Digitized by Microseftpa), 71.

168

Articulation or Articulations—continued.
intermetacarpal, 75.
intertarsal, 159.
metacarpo-phalangeal, 76.
proximal interphalangeal, 89.
radio-carpal, 71.
radio-ulnar, 7].
shoulder, 67.
talo-crural, 159.
tarsal, 159.
tarso-metatarsal, 159.
tibio-fibular, 159.

Ascending cervical artery, 6.

Axilla, 4.

Axillary artery, 6, 21.

Axillary lymph glands, 15.

Axillary nerve, 18, 34.

Axillary vein, 6, 25.

Biceps brachii muscle, 15, 40.

Biceps femoris muscle, 109.

Blood supply of the muscles of the pelvic
limb, table, 165.

Blood supply of the muscles of the
thoracic limb, table, 94.

Brachial artery, 24.

Brachial plexus, 7.

Brachial vein, 25.

Brachialis muscle, 30, 40.

Brachiocephalic muscle, 14.

Cauuosity of the forearm, 33.

Callosity of the tarsus, 125.

Capsular muscle (of the arm), 18.

Capsular muscle (of the thigh), 120.

Carpal articulations and ligaments, 71.

Carpo-metacarpal joint, 71.

Cartilages of the third phalanx, 87.

Caudal pectoral nerve, 7.

Cephalic vein, 1, 34.

Cervical artery, ascending, 6.

“Chestnut,” 33, 125.

Circumflex femoral artery, laterai, 120.

Circumflex femoral artery, medial, 106.

Circumflex humeral artery, anterior, 24.

Cireumflex humeral artery, posterior, 22.

Cireumflex scapular artery, 23.

Collateral radial artery, 24, 39.

Collateral ulnar artery, 24, 49.

Collateral ulnar vein, 50.

Common digital artery, 64, 151.

Common digital vein, 65.

Cominon iuterosseous artery, 52.

Common peroneal nerve, 106, 117, 141.

Coracobrachial muscle, 16.

Coronal arteries of third phalanx, 89.

Coronary groove of the hoof, 82.

Coronary matrix of the hoof, 79.

Cranial pectoral nerves, 7.

Cruciate ligaments of
joint, 157.

Cruro-parietal groove of the hoof, 83.

Cubital lymph glands, 15.

Cuneate matrix of the hoof, 80.

Cuneus of the hoof, 83.

femoro-tibial

TOPOGRAPHICAL ANATOMY OF

LIMBS OF HORSE

Cutaneous nerves—
dorsal antibrachial, 31, 34.
forearm, 20, 25, 31, 34.
gluteal and hip region, 107.
lateral antibrachial, 20, 34.
lateral brachial, 25, 34.
leg, 117, 118, 127.
pectoral region, 1.
scapular region, 10.
tarsus and metatarsus, 117, 127.
thigh, 107, 115.

Deep artery of the penis, 105.
Deep brachial artery, 24, 39.
Deep femoral artery, 106.
Deep inguinal lymph glands, 98.
Deep peroneal nerve, 143.
Deep plantar venous arch, 153.
Deep volar arterial arch, 63.
Deltoid muscle, 25.
Digital arteries, common, 64, 151.
Digital arteries, plantar, 151.
Digital arteries, volar, 64, 89.
Digital fascia, 55.
Digital torus, 84.
Digital veins, 65.
Distal interphalangeal joint, 91.
Distal plantar arterial arch, 151.
Distal plantar venous arch, 151.
Dorsal arteries of third phalanx, 89.
Dorsal carpal ligament, 35.
Dorsal cutaneous nerve of the forearm,
31, 34.
Dorsal interosseous artery, 39.
Dorsal ligament of the carpus, 35.
Dorsal metacarpal arteries, 64.
Dorsal metatarsal veins, 152.
Dorsal rete of the carpus, 40.
Dorsal tarsal ligament, 161.
Dorsalis pedis artery, 145.

Epow joint, 69.

Eleventh cerebral nerve, 14.

“ Ergot,” 54.

Evolution of the horse’s limb, 31.
Extensor carpi radialis, 35.
Extensor carpi ulnaris, 38.
Extensor digiti quinti, 38, 57.
Extensor digitorum brevis, 137.
Extensor digitorum communis, 37, 55.
Extensor digitorum longus, 137.
External thoracic artery, 6.
External thoracic vein, 6, 25.

Fascia—

antibrachial, 34.

digital, 55.

gluteal, 107.

lata, 107.

metacarpal, 55.

of leg, 127.

pectoral, 1.

tarsal, 128.
Femoral artery, 101, 106.
Femoral artery, anterior, 101.
Femoral artery, deep, 106.
Femoral artery, lateral circumflex, 120.

Digitized by Microsoft®

INDEX

Femoral artery, medial circumflex, 106.

Femoral artery, posterior, 104, 106.

Femoral nerve, 104.

Femoral triangle, 100.

Femoral vein, 101.

Femoro-patellar joint, 153, 154.

Femoro-patellar ligaments, 154.

Femoro-tibial joint, 153. 155.

Flexor carpi radialis, 41.

Flexor carpi wlnaris, 41.

Flexor digitorum brevis, 129, 147.

Flexor digitorum longus, 132.

eee digitorum profundus, 41, 58, 132,
147.

Flexor digitorum sublimis, 41, 57.

Flexor hallucis longus, 132.

Foot, 78.

Fossa, supraclavicular, 1.

“Frog” of the hoof, 83.

GASTROCNEMIUS muscle, 128.
Gemelli inuscles, 113.
Gluteal arteries, 114.
Gluteal muscle, deep, 113.
Gluteal muscle, middle, 111.
Gluteal muscle, superficial, 109.
Gluteal nerves, 115.
Gracilis muscle, 97.
Groove—
coronary, of the hoof, 82.
cruro-parietal, of the hoof, 83.
intercrural, of the hoof, 83.
pectoral, lateral, 1.
pectoral, median, 1.

Hip Jornt, 122,

Hoof, 80.

Humeral artery, anterior circumflex, 24.
Humeral artery, posterior circumflex, 22.
Humero-radial joint, 69.

Humero-ulnar Joint, 69.

ILIo-FEMORAL ligament, 123.

Tlio-psoas muscle, 105.

Infraspinous muscle, 27.

Inguinal lymph glands, deep, 98.

Intercarpal joint, 71.

Intercrural groove of the cuneus, 83.

Intermetacarpal joint, 75.

Internal obturator muscle, 114.

Interosseous artery, common, 52.

Interosseous artery, dorsal, 39.

Interosseous artery, recurrent, 40.

Interosseous ligament of the elbow joint,
va

Interosseous membrane of tibio-fibular
joint, 159.

Interosseous muscles, 60, 148.

Interosseous nerve, 52.

Interphalangeal joint, distal, 91.

Interphalangeal joint, proximal, 89.

Intertarsal joint, 159.
Jotnts. See Articulations.

Laprum glenoidale of acetabulum, 124.
Lacertus fibrosus, 35.

169

Laminee of hoof, 82.
Laminar matrix, 80.
Lateral circumflex femoral artery, 120.
Lateral cutaneous femoral nerve, 107.
Lateral cutaneous nerve of the arm, 25,
34.
Lateral cutaneous nerve of the forearm,
20, 34.
Lateral dorsal metatarsal artery, 146.
Lateral pectoral groove, 1.
Lateral tarsal artery, 136.
Latissimus dorsi muscle, 8, 12.
Ligament or Ligaments—
accessory, 124.
cruciate, of fermoro-tibial joint, 157.
dorsal carpal, 35.
dorsal tarsal, 161.
feimoro-patellar, 154.
ilio-femoral, 123.
interosseous, of elbow joint, 71.
interosseous, of tibio-fibular joint, 159.
of carpal articulations, 73.
of cartilages of the third phalanx, 88.
of distal interphalangeal joint, 90.
of elbow joint, 69.
of “ergot,” 55.
of femoro-patellar joint, 154.
of femoro-tibial joint, 155.
of hip joint, 122.
of proximal interphalangeal joint, 90.
of shoulder joint, 67.
of tarsal articulations, 159.
patellar, 155.
phalango-sesamoidean, 91.
plantar tarsal, 162.
round, of the hip joint, 124.
sesamoid, 76, 92.
talo-calcanean, 162.
transverse carpal, 35.
transverse, of acetabulum, 124.
transverse, of elbow joint, 71.
transverse, of tarsal region, 128, 136.
vaginal, of flexor tendons, 55.
volar annular, 55,
Limbus ungule, 81.
Long thoracic nerve, 7.
Lumbrical muscles, 60, 148.
Lymph glands—
axillary, 15.
cubital, 15
deep inguinal, 98.
of the arm, 114,
popliteal, 106.

MaRGINAL matrix, 79.

Matrix of the hoof, 78.

Medial circumflex femoral artery, 106.
Medial tarsal artery, 136, 149.
Median artery, 52.

Median nerve, 19, 34, 50.

Median pectoral groove, 1.

Median vein, 53.

Menisci of femoro-tibial joint, 158.
Metacarpal arteries, 61.
Metacarpal fascia, 55.

Metagarpal nerves, 65.

Digitized by Microsoft

170

Metacarpal veins, 65.
Metacarpo-phalangeal joint, 76.
Metatarsal arteries, plantar, 150.
Metatarsal artery, lateral dorsal, 146.
Metatarsal nerves, 148.

Metatarsal veins, 152.

Muscles of the pelvic lim), nerve and

blood supply, table, 165.

Muscles of the thoracic limb, nerve and

blood supply, table, 94.
Musculo-cutaneous nerve, 18.
Musculus or Musculi—
abductor pollicis longus, 38.
adductor, 98.
anconeeus, 30.
biceps brachii, 15, 40.
biceps femoris, 109.
brachialis, 30, 40.
brachiocephalicus, 14.
capsularis (brachii), 18.
capsularis (femoris), 120.
coracobrachialis, 16.
deltoideus, 25.
extensor carpi radialis, 35.
extensor carpi ulnaris, 38.
extensor digiti quinti, 38, 57.
extensor digitorum brevis, 137.
extensor digitorum communis, 37, 55.
extensor digitornm longus, 137.
flexor carpi radialis, 41.
flexor carpi ulnaris, 41.
flexor digitorum brevis, 129, 147.
flexor digitorum longus, 132.
flexor digitorum profundus, 41, 58,

132, 147.
flexor digitorum sublimis, 41, 57.
flexor hallucis longus, 132.
gastrocnemius, 128,
gemelli, 113.
glutzeo biceps, 111.
glutzeus accessorins, 113.
glutzeus medius, 111.
gluteus profundus, 113.
glutzeus superticialis, 109.
gracilis, 97.
ilio-psoas, 105.
infraspinatus, 27.
interossei, 60, 148.
latissimus dorsi, 8, 12.
lumbricales, 60, 148.
obturator externus, 104.
obturator internus, 114.
omohyoideus, 8.
pectineus, 98.
pectoralis profundus, 4, 14.
pectoralis superficialis, 1.
peronzeus longus, 137.
peronzeus tertius, 138.
piriformis, 113.
pla. ris, 129.
popliteus, 132.
quadratus femoris, 104.
quadriceps femoris, 119.
rectus femoris, 120.
rhomboideus cervicalis, 10.
rhomboideus thoracalis, 10.

TOPOGRAPHICAL ANATOMY

OF LIMBS OF HORSE

Musculus or Musculi—continued.

sartorius, 98.
semimembranosus, 100.
semitendinosus, 111.
serratus ventralis, 7.
soleus, 129.
subscapularis, 15.
supraspinatus, 25.
tensor fascize antibrachii, 16.
tensor fascize latae, 109.
teres major, 15.

teres minor, 29.

tibialis anterior, 139.
tibialis posterior, 132.
trapezius, 10.

triceps brachii, 16, 30.
vastus intermedius, 119.
vastus lateralis, 114.
vastus medialis, 98.

Nerve and blood supply of the muscles
of the pelvic hmb, table, 165.
Nerve and blood supply of the muscles
of the thoracic limb, table, 94.

Nerves of the metacarpus and digit, 65.
Nerves of the metatarsus and digit, 148.
Nervus or Nervi—

accessorius, 14.

axillaris, 18, 34.

cutaneus antibrachii dorsalis, 31, 34.

cutaneus antibrachii lateralis, 20, 34.

cutaneus brachii lateralis, 25, 34.

cutaneus femoris lateralis, 107.

cutaneus femoris posterior, 107, 115.

cutaneus sure anterior, 118, 127.

cutaneus sure posterior, 117, 127, 131.

femoralis, 104.

gluteus caudalis, 115.

glutzeus cranialis, 115.

interosseus, 52.

ischiadicus, 106, 115.

medianus, 19, 34, 50.

musculocutaneus, 18.

obturatorius, 105.

pectorales craniales, 7.

pectoralis caudalis, 7.

peroneus communis, 106, 117, 141.

peroneus profundus, 143.

peronzeus superficialis, 127, 142.

plantares, 148.

plexus brachialis, 7.

radialis, 21, 31, 34, 39.

sapheuus, 96, 104, 127.

subscapulares, 18.

supraclavicularis, 1, 10.

suprascapularis, 18.

thoracalis longus, 7.

thoracodorsalis, 7, 18.

tibialis, 106, 116, 131.

ulnaris, 21, 34, 47.

volaris lateralis, 66.

volaris medialis, 65.
Nutrient artery of the femur, 104.
Nutrient artery of the humerus, 24.
Nutrient artery of the radius, 40.
Nutrient artery of the tibia, 136.

Digitized by Microsoft®

INDEX

OBTURATOR artery, 105.
Obturator externus muscle, 104.
Obturator internus muscle, 114.
Obturator nerve, 105.
Obturator vein, 105.
Omo-cervical arterial trunk, 6.
Omohyoid muscle, &.

PaTELLaR ligaments, 155.

Pectineus muscle, 98,

Pectoral fascia, 1.

Pectoral grooves, 1.

Pectoral muscle, deep, 4, 14.

Pectoral muscle, superticial, 1.
Pectoral nerves, 7.

Penis, deep artery of, 105.

Perforating tarsal artery, 145, 150.
Perforating tarsal vein, 153.

Peronzeus longus muscle, 137.
Peronzus tertius muscle, 138.
Peroneal artery, 144.

Peroneal nerve, common, 106, 117, 141.
Peroneal nerve, deep, 143.

Peroneal nerve, superficial, 127, 142.
Phalanges, arteries of, 65, 89.
Phalango-sesamoidean ligament, 91.
Phillips’ muscle, 37.

Piriformis muscle, 113.

Plantar arterial arch, distal, 151.
Plantar arterial arch, proximal, 150.
Plantar arteries, 149.

Plantar digital arteries, 151.
Plantar metatarsal arteries, 151.
Plantar metatarsal veins, 153.
Plantar nerves, 148.

Plantar tarsal ligament, 162.
Plantar venous arch, deep, 153.
Plantar venous arch, distal, 151.
Plantaris muscle, 129.

Popliteal artery, 134.

Popliteal lymph glands, 106.
Popliteal vein, 135.

Popliteus muscle, 132.

Posterior circumflex artery of the hum-

ie

erus, 22.

Posterior cutaneous femoral nerve, 107,
115.

Posterior cutaneous sural nerve, 117,
127, 131.

Posterior femoral artery, 104, 106.
Posterior tibial artery, 135.
Proximal interphalangeal joint, 89.

QuapratTus femoris muscle, 104.
(uadriceps femoris muscle, 98, 114, 119.

RaDIa_ artery, collateral, 24, 39.
Radial nerve, 21, 31, 34, 39.
Radio-carpal joint, 71.
Radio-ulnar joint, 71.

Rectus femoris muscle, 120.
Recurrent interosseous artery, 40.
Recurrent tarsal artery, 136.
Recurrent tarsal vein, 127.
Recurrent tibial artery, 136.
Recurrent tibial vein, 125.

171

Rete carpi dorsale, 40.

Rete carpi volare, 53.

Rhomboideus muscle, 10.

Round ligament of the hip joint, 124.

SAPHENOUS artery, 96, 101.
Saphenous nerve, 96, 104, 127.
Saphenous vein, 96, 125.
Sartorius muscle, 98.
Scapular artery, circumflex, 23.
Scapular artery, transverse, 1, 6.
Sciatic nerve, 106, 115.
Semimembranosus muscle, 100.
Semitendinosus muscle, 111.
Sesamoid ligaments, 76, 92.
Shoulder joint, 67.
Solar matrix, 80.
Sole of the hoof, 82.
Soleus muscle, 129.
Spine of cuneus, 83.
“Stitle-joint,” 153.
Subscapular artery, 21.
Subscapular muscle, 15.
Subscapular nerve, 18.
Superficial peroneal nerve, 127, 142.
Supraclavicular fossa, 1.
Supraclavicular nerve, 1, 10.
Suprascapular nerve, 18.
Supraspinous muscle, 25.
Sural cutaneous nerves, 117, 118, 127,
131.

Surface anatomy—

pectoral region, 1.

scapular region, 8.

forearm, 33.

metacarpus and digit, 53.

thigh, medial aspect, 96.

gluteal and hip region, 107.

leg, 125.
Synovial tendon sheaths, pelvic limb,
139.
Synovial tendon sheaths, thoracic limb,
59.

TALO-CALCANEAN ligaments, 162.
Talo-crural joint, 159.

Tarsal artery, lateral, 136.

Tarsal artery, medial, 136, 149.
Tarsal artery, perforating, 145, 150.
Tarsal artery, recurrent, 136.
Tarsal joints, 159.

Tarsal ligament, dorsal, 161.

Tarsal ligament, plantar, 162,
Tarsal vein, perforating, 153.
Tarsal vein, recurrent, 127.
Tarso-metatarsal joint, 159.

Tendo calcaneus Achillis, 128.
Tendon sheaths of pelvic limb, 139.
Tendon sheaths of thoracic limb, 59.
Tensor fascie late, 109. ice
Tensor of antibrachial fascia, 16. °
Teres major muscle, 15.

Teres minor muscle, 29.

Terminal arch of digital arteries, 89.
Thiernesse’s muscle, 37.

Thoracic artery, external, 6.

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172

Thoracic nerve, long, 7.
Thoraco-acromial artery, 21.
Thoracodorsal artery, 22.

Thoracodorsal nerve, 7, 18.

Tibial artery, anterior, 144.

Tibial artery, posterior, 135.

Tibial artery, recurrent, 136.

Tibial nerve, 106, 116, 131.

Tibial vein, anterior, 146.

Tibial vein, recurrent, 125.

Tibialis anterior muscle, 139.

Tibialis posterior muscle, 132.
Tibio-fibular joint, 159.

Torus, digital, 84.

Torus, digital, arteries of, 65, 89.
Transverse carpal ligament, 35.
Transverse ligament of acetabulum, 124.
Transverse ligaments of elbow joint, 71.
Transverse ligaments of tarsal region, 136.
Transverse scapular artery, 1, 16.
Trapezius muscle, 10.

Triceps brachii muscle, 16, 30.
Trigonum femorale, 100.

Uxwar artery, collateral, 24, 49.
Ulnar nerve, 21, 34, 47.
Ulnar vein, collateral, 50.

VaGINA carpet, 46, 57.

Vaginze mucosee, 59, 139.

Vaginal ligament of the flexor tendons,
55.

Vastus intermedius muscle, 119.

Vastus lateralis muscle, 114. :

Vastus medialis muscle, 98.

Ventral serratus muscle, 7.

Veins of the metacarpus, 65.

Veins of the metatarsus, 151.

Vena or Venze—
arenus plantaris profundis, 153.
arcus venosus plantaris distalis, 151.
arcus venosus volaris, 65.

TOPOGRAPHICAL ANATOMY OF LIMBS OF HORSE

Vena or Venee—continued.
axillaris, 6, 25.
brachialis, 25.
cephalica, 1.
cephalica accessoria, 34.
cephalica antibrachii, 34.
collateralis ulnaris, 50.
digitalis communis, 65.
digitalis lateralis, 65.
digitalis medialis, 65.
femoralis, 101.
medianze, 53.
metacarpea volaris lateralis, 65.
metacarpea volaris profunda, 65.
metatarsea dorsalis lateralis, 152.
metatarsea dorsalis media, 153.
metatarsea dorsalis medialis, 152.
netatarsea plantaris profunda medialis,

153.

metatarsea plantaris —_ supertficialis
lateralis, 153.

metatarsea plantaris — superficialis

medialis, 153.
obturatoria, 105.
poplitea, 135.
recurrens tibialis, 125.
saphena, 96, 125.
tarsea perforans, 153.
tarsea recurrens, 127.
thoracica externa, €, 25.
tibialis anterior, 146.
Volar annular ligament, 55.
Volar arterial arch, deep, 63.
Volar digital arteries, 64, 89.
Volar matrix, 80.
Volar metacarpal arteries, 61.
Volar metacarpal veins, 65.
Volar nerves, 65.
Volar rete of the carpus, 53.
Volar venous arch, 65.

Watt of the hoof, 80, 84.

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