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THE
ANATOMY OF THE HORSE
DISSECTION GUIDE
i
J. M'PADYEAN, M.B., CM., B.Sc,
MEMBER OF THE ROYAL COLLEGE OF VETERINARY SURGEONS,
LECTURER ON ANATOMY AT THE ROYAL (DICK's) VETERINARY COLLEGE, EDINBURGH.
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W. & A. K. JOHNSTON,
EDINBURGH AND LONDON.
AU rights reserved.}                              » »,
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W. AND A. K. JOHNSTON, PRINTERS, EDINBURGH AND LONDON.
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TO
WILLIAM TURNER, M.B., LL.D., F.R.S.,
PROFESSOR OF ANATOMY IX THE UNIVERSITY OF EDINBURGH.
AS A TRIBUTE TO HIS EMINENCE
AS AN ANATOMICAL TEACHER.
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.
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P E E F A C E.
----------o----------
The want of an illustrated topographical treatise on equine anatomy has,
in the experience of the author, been a great barrier to the efficient
teaching of that all-important branch of veterinary education. In this
work the object of the author has been to place in the hands of veterinary
students a dissection guide comparable, in some degree, to the text-books
at the service of the practical student of human anatomy. The order of
dissection laid down is that which the author has found to be most advan-
tageous, and he has attempted to describe with accuracy and moderate
fulness the different organs as they present themselves in that order.
This description is largely supplemented by the illustrations, which are
so complete that almost every organ in the body is delineated. The
majority of these illustations are original, being faithful portraits of the
author's own dissections. It is hoped that they will prove useful to the
student, in the first place, as a plan and a guide in his work, and,
secondly, as a means by which he may afterwards summon up a mental
picture of his own dissections.
While the book is specially designed for use in the dissecting-room,
the author ventures to hope that it may also be serviceable to the
\eterinary practitioner. Special care has been taken in portraying those
regions that possess a surgical interest, and the illustrations furnish a
ready means by which the surgeon may refresh his memory regarding
the objects to be met in the course of an operation.
The greater number of the original drawings were made in the dissecting-
room of the Eoyal (Dick's) Veterinary College, by Mr J. Bayne, artist;
a few were executed by Mr K. S. Eeid, artist; and the remainder by
Mr K. H. Potts, veterinary student. A few of the illustrations were
directly drawn on stone by Messrs W. & A. K. Johnston. To all of
these gentlemen the author is much indebted for the clearness and
fidelity with which they have delineated the various objects.
The source of each of the borrowed illustrations is duly acknowledged
elsewhere, but the author is constrained to make special mention of
those from the systematic text-book of Professor Chauveau, who
generously consented to the copying of as many of his figures as might
be thought useful for this work.
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PREFACE.
To insure accuracy, the author lias been careful to compare the nefcults
of his own dissections with the descriptions of other writers, and more
especially with the works of Percivall, Leyh, and Chauveau, to which he
begs to express his indebtedness.
To Professor Turner the author is under deep obligation for the
revision of the chapters on the brain, the eye, and the ear, and for much-
esteemed suggestions regarding other points.
Finally, the author's best thanks are due to his brothers Gavin and
Andrew, who have carefully revised the entire proof-sheets, and to
Mr. T. Barker, veterinary student, for assistance in making the index.
Royal (Dick's) Veterinary College, Edinburgh,
October, 1884.
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A few words are here necessary in explanation of the system of nomen-
clature used throughout this work. Although reluctant to add to the
confusion already prevailing in the nomenclature of veterinary anatomy,
the author has not conformed to any of the systems in general use.
The system here employed is based on the principle of naming each
object after the homologous object in human anatomy. So far, indeed,
as any of the systems in use can be said to follow a principle, it is that
just stated; but the violations of the principle are numerous, and, in
most cases, appear to have been dictated by the merest caprice. The
most vicious form of departure from the principle is that in which terms
adopted from human anatomy are employed to designate not the actual
homologues, but other parts having, it may be, some faint resemblance
in shape or otherwise to the objects bearing these names in the human
svibject. This method is indefensible, since it tends to produce the
greatest confusion, and, if generally adopted, would render a comparison
of the anatomy of any two animals an impossibility. Many such terms
have long been in use, but it is hoped that they are not ineradicable.
In cases where objects appear to be without homologues in human
anatomy, new names must, of course, be found. In only a few of these
instances, however, has the author employed terms of his own invention,
preferring, in general, to adopt some of those already in use.
The greatest diversity of names, it will be found, exists in the case of
muscles, and the following table of synonyms has been compiled for the
convenience of those already familiar with the terms employed in some
other works.
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TABLE OF SYNONYMS OF MUSCLES.
Leth.
Chauveau.
Percivail.
Posterior pubio-femoralis.
Middle pubio-femoralis.
(part of) Urethral muscle.
Small humero-olecranius.
Sterno-scapularis.
Small sterno-humeralis.
Idem.
Palato-staphylinus.
Coraco-radialis.
Sacro-ischio-tibialis ant.
Humero-radialis.
Idem and molaris.
Great scapulo-olecranius.
i External scapulo-olecranius.
Internal humero-olecranius.
Small kerato-hyoid.
j Idem.
Dorso-occipitalis.
Ischio-coccygeus.
Middle scapulo-humeralis.
Superior external palpebral.
Idem.
Sacro-coccygeus lateralis.
Great adductor of thigh.
Small adductor of thigh.
Bulbo-cavernosus.
Small extensor of fore-arm.
(part of) Deep pectoral.
(part of) Superficial pectoral.
Idem.
Palato-staphyleus.
Long flexor of the fore-arm.
Long vastus.
Short flexor of fore-arm.
Alveolo-labialis.
Chief extensor of the fore-arm.
Short extensor of the fore-arm.
Middle extensor of fore-arm.
Idem.
Idem.
Great complexus.
Ischio-coccygeus.
Idem.
Fronto-palpebral.
Idem.
Sacro-coccygeus lateralis.
! Adductor magnus.
Adductor parvus.
Accelerator urinse.
I Anconeus.
Anterior deep pectoral.
Anterior superficial pectoral.
I Aryteno-pharyngeus.
Azygos uvulse.
I Biceps.
1 Biceps femoris.
Brachialis anticus.
Buccinator.
j
; Caput magnum,
i Caput medium.
j Caput parvum.
Cerato-hyoid.
Cervico-auriculares.
Complexus.
Compressor coccygis.
Coraco-humeralis.
Corrugator supercilii.
Crico-pharyngeus.
Curvator coccygis.
Adductor longus.
Adductor brevis.
■ Idem.
Idem.
Pectoralis parvus.
\ (part of) Pectoralis transversus.
(Not described.)
Circumflexus palati.
Flexor brachii.
Biceps abductor femoris.
Humeralis externus.
Idem and caninus.
Idem.
Idem.
Idem.
Hyoideus parvus.
1 Retrahontes.
Complexus major.
Idem.
Idem.
Levator palpebral superioris.
Constrictor pharyngis posterior.
Idem.
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Table of Synonyms of Muscles—continued.
Chauveau.
Leyh.
Peecivall.
Deep flexor of digit (fore limb).
Deep flexor of digit (hind limb).
Deep gluteus.
Deltoid.
Depressor labii inferioris.
Depressor labii superioris.
Depressor coccygis.
Dilatator naris inferior.
Dilatator naris lateralis.
Dilatator naris superior.
Dilatator naris transversalis.
Erector clitoridis.
Erector coccygis.
Erector penis.
Extensor brevis.
Extensor metacarpi magnus.
Extensor metacarpi obliquus.
Extensor pedis (fore limb).
Extensor pedis (hind limb).
Extensor suffraginis.
External oblique of abdomen.
External pterygoid.
(See flexor pedis perforans.)
Gluteus internus.
Teres minor.
Idem.
Idem.
Idem.
Small ilio-trochanterius.
Great scapulo-trochanterius.
Maxillo-labialis inferior.
Incisive of upper lip.
Long and short sacro-coccygeus
inferior.
Small super-maxillo nasalis.
Great super-maxillo nasalis.
Short muscle of nose.
Idem.
Long abductor of arm.
Maxillo-labialis.
Intermediate anterior.
Sacro-coccygeus inferior.
(part of) Nasalis brevis labii superi- j (part of) Small super-maxillo na-
oris.                                                i salis.
Idem.                                                    j Great super-maxillo nasalis.
(part of) Nasalis brevis labii superi- I (part of) Small super-maxillo na-
oris.                                                         salis.
Dilator naris anterior.                        | Naso transversalis.
Transversus nasi.
Idem.
Sacro-coccygeus superior.
Idem.
Ischio-cavernosus.
(Un-named
.)
Pedal muscle.
Idem.
Anterior extensor of metacarpus.
Idem.
Oblique extensor of metacarpus.
Idem.
Anterior extensor of phalanges.
Idem.
Anterior extensor of phalanges.
Idem.
Idem.
Lateral extensor of phalanges.
Idem.
Idem.
Idem.
Idem.
Oblique flexor of phalanges.
Epitrochlo-
carpeus.
External flexor of metacarpus.
Epicondylo
-metacarpeus.
Internal flexor of metacarpus.
Epicondylo
-carpeus.
Oblique flexor of metacarpus.
Idem.
Idem.
Sacro-coccygeus superior.
Ischio-penial muscle.
(As Chauveau.)
Humero-metacarpeus anterior.
Kadi o-metacarpeus.
Humero-pre-phalangeus.
Femoro -pre-pbalangeus.
Radio -pre-phalangeus.
Costo-abdominalis exterior. .
(part of) Spheno-maxillaris.
Small tibio-phalangeus.
Humero-supercarpeus externus.
Humero-metacarpeus internus.
Humero-supercarpeus internus.
Tibio-j ire-metatarsus,
Flexor accessorius.
Flexor metacarpi externus.
Flexor metacarpi interims.
Flexor metacarpi medius.
Flexor metatarsi.
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Flexor pedis per- ("ulnar head.
forans (fore -s radial head.
limb)                    ( humeral head.
Flexor pedis perforans (bind limb).
Flexor pedis perforates (fore limb).
Flexor pedis perforates (hind limb).
Gastrocnemius.
Gemelli.
Genio-glossus.
Gracilis.
Great hyo-glossus.
Hyoideus transversus.
Iliacus.
Infraspinatus.
Internal intercostal.
Internal oblique of abdomen.
Internal pterygoid.
Interossei.
Intertransversales of neck.
Ischio-urethral.
Lateralis sterni.
Latissimus dorsi.
Levator anguli scapula?.
Levatores costarum.
Levator labii superioris alaaqui
nasi.
Levator labii superioris proprius.
Levator menti.
Levator palati.
Levator rjalpebrse superioris.
Longissimus dorsi.
Longus colli.
Lumbricales.
Masseter.
Ulnaris accessoritis.
Radialis accessorius.
Flexor pedis perforans.
Hexor pedis.
Idem.
Gastrocnemius internus.
Gastrocnemius externus.
Gemini.
Genio-hyo-glossus.
Idem.
Hyo-glossus brevis.
(Not described.)
Idem.
(part of) Postea-spinatus.
Idem and sterno-costales extern
Idem.
Idem.
Lumbrici anteriores.
(Not described.)
Triangularis penis.
Idem.
Idem.
Part of serratus magnus.
Idem.
Idem.
Nasalis longus labii superioris.
Idem.
Stylo-pharyngexis.
Levator palpebral superioris int
nus.
Idem and spinalis dorsi.
Idem.
Lumbrici posteriores.
Idem.
Eadio-phalangeus.
Great tibio-phalangeus.
Humero-phalangeus.
Femoro-phalangeus.
Bi-femoro-calcaneus.
Gemelli of pelvis.
Idem.
Pubio-tibialis.
Hyo-glossus.
Idem.
Great and middle ilio-femoralis.
Posterior spinous.
Idem.
Ilio-abdominalis.
(part of) Spheno-maxillaris.
Idem.
Idem.
Part of urethral muscle.
Transverse muscle of ribs.
Dorso-humeralis.
Traehelo-scapularis.
Idem.
Fronto-labialis.
Maxillo-labialis superior.
Incisive of lower lip and mento- j
labialis.
Stylo-staphylinus.
Superior internal palpebral.
Ilio-spinalis.
Dorso-atloideus.
Idem.
Zygomato-maxillaris.
Deep flexor of phalanges.
Deep flexor of phalanges.
Superficial flexor of phalanges.
Superficial flexor of phalanges.
Gemelli of leg.
Gemelli of pelvis.
Idem.
Short adductor of the leg.
Idem.
Idem.
Iliac psoas.
Subspinous.
Idem,
Idem.
Idem.
Idem.
Idem.
Compressor of Cowper's glands.
Transverse muscle of ribs.
Great dorsal.
Angularis scapulse.
Supercostales.
Supernaso-labialis.
Supermaxillo-labialis.
Intermediate posterior and mento-
labialis.
Peristaphyleus internus.
Idem.
Ilio-spinalis.
Idem.
Idem.
Idem.
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Table of Synonyms of Muscles—continued.
Pekoivall.
Chauveau.
Leyh.
1
Mastoido-auricularis.
(Not described.!
Tympano-auricularis.
1
Idem.
Mastoido-humeralis.
Levator humeri.
Idem.
Common muscle of the arm, neck,
and head.
Middle gluteus.
Gluteus maximus.
Idem.
Great and middle ilio-trochanterius.:
Middle hyo-glossus.
(Not described.)
(Not described.)
Kerato-glossus internus.
Mylo-hyoideus.
Idem.
Idem.
Idem and mylo-glossus.
Obliquus capitis inferior.
Idem.
Great oblique of head.
Axoido-atloideus.
Obliquus capitis superior.
Idem.
Small oblique of head.
Atloido-occipitalis lateralis.
Occipito-styloid.
Stylo-hyoideus.
Idem.
Stylo-hyoideus.
Orbicularis oris.
Idem.
Labialis.
Orbicularis of the lips.
Palato-glossus.
(Not described.)
Pharyngo-glossus.
Pharyngo-glossus.
Palato-pliaryngeus.
Idem (in part).
Pharyngo-staphyleus.
Staphylinus communis.
Parieto-auricularis externus.
Attolens maximus.
Temporo-auricularis externus.
Common muscle of ear.
Parieto-auricularis internus.
Attolens posticus.
Temporo-auricularis internus.
Parieto-auricularis.
Parotido-auricularis.
Abducens vet deprhnens aurem.
Idem.
Idem.
Pectineus.
Idem.
Idem.
Pubio-femoralis anterior.
Peroneus.
Idem.
Lateral extensor of phalanges.
Tibio-pre-phalangeus.
Popliteus.
Idem.
Idem.
Oblique femoro-tibialis.
Posterior deep pectoral.
Pectoralis magnus.
(part of) Deep pectoral.
Great sterno-humeralis.
Posterior superficial pectoral.
(part of) Pectoralis transversus.
(part of) Superficial pectoral.
Sterno-radialis.
Psoas magnus.
Idem.
Idem.
Lumbo-femoralis.
Psoas parvus.
Idem.
Idem.
Lumbo-ilialis.
Pterygo-pharyngeus.
(part of) Palato-pharyngeus.
Idem.
Idem.
Pyriformis.
Idem.
(part of) Obturator internus.
Sacro-trochanterius.
Quadratus femoris.
(Not described.)
Quadrate crural.
Small ischio-femoralis.
Quadratus lumborum.
Sacro-lumbalis.
Idem.
Idem.
Rectus abdominis.
Idem.
Idem.
Sterno-pubialis.
Rectus capitis anticus major.
Idem.
Idem.
Trachelo-occipitalis.
Rectus capitis anticus minor.
Idem.
Idem.
Atloido-occipitalis inferior.
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Atloido-styloideus.
Atloido-occipitalis longusand brevis.
Atloido-occipitalis superior.
Ilio-rotuleus anterior.
Small ilio-femoralis.
Lumbo-costalis.
Cervico-subscapularis and dorso
scapularis.
Ilio-rotuleus internus.
Costo-trachelius.
Idem.
Long scapulo-olecranius.
Idem.
Idem.
Great ischio-femoralis.
Transverse sjiinous.
Sacro-ischio-tibialis post.
Idem.
Costo-scapularis.
Idem.
(Not described.)
Kerato-pharyngeus inferior.
Peroneo-calcaneus.
Sterno-thyroid and sterno-hyoid.
I Kerato-glossus externus.
Great kerato-hyoid.
Idem.
Kerato-pharyngeus superior.
Scapulo-hyoid.
I Obliquus capitis anticus.
i Idem and complexus minor.
j Idem.
Rectus.
I Crureus.
(part of) Obliquus abdominis
internus.
Idem.
I Idem.
Idem.
Idem.
Anterior straight of thigh.
Anterior gracilis.
Rectus capitis lateralis.
Rectus capitis posticus major.
Rectus capitis posticus minor.
Rectus femoris.
Rectus parvus.
Retractor costse.
Rhomboideus.
Idem.
Long adductor of the leg.
Idem.
Small scapulo-humeralis.
Long extensor of the fore-arm.
Idem.
Idem.
Idem.
Transverse spinous.
Transverse spinous.
Idem.
Anterior small serratus.
Idem.
Posterior small serratus.
Idem.
Idem.
Idem.
Sterno-thyroid and sterno-hyoid.
Idem.
(part of) Digastricus
Idem.
Idem.
Idem.
Idem.
Idem.
(part of) Caput magnum.
Anterior conchse.
Posterior conchas.
Adductor magnus.
Idem.
Spinalis colli.
Adductor tibialis.
(part of) Superficialis costarum.
Idem and levator anguli scapulas.
(part of) Superficialis costarum.
(Not described.)
(Not described.)
Plantaris.
Idem.
Hyo-glossus longus.
Hyoideus magnus.
Idem.
Hyo-pharyngeus.
Idem.
See flexor pedis perforatus.
Gluteus externus.
Antea-spinatus.
Idem.
Idem.
Sartorius.
Scalenus.
Scapulo-humeralis gracilis.
Scapulo-ulnaris.
Scuto-auricularis externus.
Scuto-auricularis interims.
Semimembranosus.
Semispinalis of (back and loins).
Semispinalis (colli).
Semitendinosus.
Serratus anticus.
Serratus magnus.
Serratus posticus.
Small hyo-glossus.
Small stylo-pharyngeus.
Soleus.
Sterno-thyro-hyoideus.
Stylo-glossus.
Stylo-hyoideus.
Stylo-maxillaris.
Stylo-pharyngeus.
Subscapulo-hyoid.
Superficial flexor of digit (fore limb)
Superficial flexor of digit (hind limb)
Superficial gluteus.
Supraspinatus.
Temporalis.
Tensor palati.
Ilio-trochanterius externus.
Anterior spinous.
Temporo-maxillaris.
Peristaphylinus externus.
Idem.
Supraspinous.
Idem.
Peristaphyleus externus.
-ocr page 14-
Table of Synonyms of Muscles—continued.
Pekcivall.
Chauveau.
Leth.
Tensor vagina? femoris.
Idem.
Muscle of fascia lata
Ilio-rotuleus externus.
Teres major.
Idem.
Adductor of arm.
Great scapulo-humeralis.
Teres minor.
(part of) Infraspinatus.
Short abductor of arm.
Middle and small scapulo-trochi-
terius.
Trachelo-mastoid.
Idem.
Small complexus.
Dorso-mastoideus.
Transversalis abdominis.
Idem.
Idem.
Costo-abdominalis internus.
Transversalis costarum.
Idem.
Common intercostal.
Common intercostal.
Transversus perinsei.
(Not described.)
Idem.
Idem.
Trapezius.
Idem.
Idem.
Cervico-acromialis.
Triangularis sterni.
Sterno-costales interni.
Idem.
Sterno-costalis.
Vastus externus.
Idem.
Idem.
Femoro-tibialis externus.
Vastirs internus.
Idem.
Idem.
Fcmoro-tibialis internus.
Wilson's muscle.
(part of) Triangularis penis.
Sphincter uretlme.
Prostatic muscle.
Zygomatico-auriciilaris.
Attolens anterior.
Idem.
Temporo-auricularis and fronto-
auricularis.
Zygomaticus.
Idem.
Zygomatico-labialis.
Zygomatico-labialis.
-ocr page 15-
PLATES.
Plate.
1.  Pectoral Region ....
2.   Pectoral Eegion ....
3.   Brachial Plexus ....
4.   Shoulder—Outer Aspect .
B. Shoulder and Arm—Inner Aspect
0. Shoulder, Arm, and Fore-arm—Inner Aspect
7.   Fo. e limb—Outer Aspect .
8.   Shoulder, Arm, and Fore-arm—Outer Aspect
9.   Metacarpus and Digit—Inner Aspect
10.   The Foot.....
11.   Joints and Ligaments of Fore limb
12.  Thigh—Inner Aspect
13.   Thigh—Inner Aspect
14.   Thigh—Inner Aspect
15.   Hip and Thigh         ....
16- Hip and Thigh ....
17.   Leg—Inner Aspect
18.  Leg—Outer Aspect
19- Metatarsus and Digit—Outer Aspect
20.   Chest-wall and Back
21.   Chest-wall and Back
22.  Thoracic Cavity—Lett Side
23.   Heart and Great Vessels-—Left Side
24.   Heart and Great Vessels—Bight Side
25.   Thoracic Cavity—Eight Side
20. Thoracic Cavity—Eight Side
27.   Neck and Intermaxillary Space .
28.  Neck             .
29.   Side of Face             ....
30.   Cavity of the Mouth
31.   Cavity of the Mouth, Pharynx, etc.
32.   Tongue, Pharynx, etc.
•«. Brain—Inferior Aspect
34. Brain—Superior Aspect .
3o. Brain—Lateral and 4th Ventricles, etc. .
36.   Brain—Ganglia of the Base
37.   Male Periiueum ....
38.  Abdominal Wall ....
39.  Abdominal "Wall ....
40.  Abdominal Wall ....
41- Intestines and Anterior Mesenteric Artery
4-- Intestines and Mesenteric Arteries
43.   Cceliac Axis, etc. ....
44.  Abdominal Viscera, etc. .
4o. Sublumbar Eegion and Diaphragm
40. Male Pelvis
47.   Genito-urinary Organs of Male .
48.  Lumbo-sacral Plexus
-ocr page 16-
lb
-ocr page 17-
CONTENTS.
CHAPTER I.
DISSECTION OF THE ANTEKIOR I.IMB.
Pagk.
1
The Foot
35
8
The Shoulder-joint
The Elbow-joint
43
44
10
The Knee
The Fetlock-joint .
46
50
17
The Pastern-joint .
52
19
The Coffin-joint
52
27
chap:
PER II.
The Pectoral Region and the Axilla
The Outer Scapular Region .
Inner Aspect of the Shoulder and
Arm......
Outer Aspect of the Shoulder and
Arm......
The Fore-arm         ....
The Metacarpus and Digit
DISSECTION OF THE POSTERIOR I.IMB.
The Metatarsus and Digit . .77
The Stifle-joint .... 81
The Tarsus.....86
The Tarso-metatarsal articulation . 90
The Inner Aspect of the Thigh .      50
The Hip and Outer Aspect of the
Thigh......      63
The Leg......      70
CHAPTER III.
DISSECTION OF THE BACK AND THORAX.
122
123
129
132
134
130
Examination of the Lung
Dissection of the Heart
Structure of the Heart .
Articulations of the Ribs
Intervertebral Joints and
ments
The Spinal Cord .
The Chest-wall and Back . . 94
The Cavity of the Thorax . . 100
The Lungs.....103
The Pericardium .... 105
The Heart.....106
The Nerves and Vessels of the left
side of the Thorax . . .108
The Nerves and Vessels of the right
side of the Thorax . . .116
Liga
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CONTENTS.
XVU1
CHAPTER IV.
DISSECTION OF THE HEAD AND NECK,
Page.
143
151
158
159
164
168
170
172
176
184
Page.
195
200
202
The Under part of the Neck .
The Upper part of the Neck .
Ligaments and Articulations of the
Neck posterior to the Dentata
The External Ear .
The Parotideal Region .
The Region of the Poll .
The Intermaxillary Space
The Appendages of the Eye .
The Face         ....
The Pterygo-maxillary Region and
the Region of the Guttural Pouch
The Tongue ....
The Hard Palate .
The Soft Palate .
The Pharynx, the Hyoid Bone, and
the Base of the Skull ... 204
TheOrhit.....208
The Occipito - atlantal Articula-
tion ......214
The Atlanto-axial Articulation . 215
The Temporo-maxillary Articulation 215
The Cavity of the Nose . . .216
CHAPTER V.
DISSECTION OF THE LAHYNX.
Cartilages of the Larynx . . 224
Articulations, Ligaments, and Mem-
branes of the Larynx . . . 226
Muscles of the Laryrx
Nerves of the Larynx
Interior of the Larynx
228
230
230
CHAPTER VI.
DISSECTION OF THE BRAIN.
. 233
The Cerebellum
. 236
The Cerebrum
. 238
The Cranial Nerves
. 240
CHAPT,
ER VII.
DISSECTION OF
THE EYEBALL.
Membranes of the Brain
Arteries of the Brain
The Medulla Oblongata .
The Pons Varolii .
240
242
253
Dissection of the Eyeball............257
CHAPTER VIII.
DISSECTION OF THE EAE.
. 267 | The Internal Ear
269
The Middle Ear
CHAPTER IX.
DISSECTION OF THE PERINEUM IN THE MALE.
280
281
ThePerinaeum . . . .274
The Scrotum.....277
The Testicle and Epididymis . . 279
The Prepuce
The Penis
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CONTENTS.                                                                    XIX
CHAPTER X.
ION OF THE ABDOMEN.
3AGB.
Page.
285
Structure of the Liver .
. 330
294
Structure of the Spleen .
. 332
320
Structure of the Pancreas
. 333
328
Structure of the Kidney
. 333
The Abdominal Wall .
The Cavity of the Abdomen
The Sublumbar Kegion .
Structure of the Stomach
CHAPTER XL
DISSECTION OF THE PELVIS.
The Hip-joint and the Ligaments
of the Pelvis . . . .338
The Cavity of the Pelvis . . 340
Reproductive Organs in the Female. 351
The Tail
Joints and Ligaments
Sacrum and Coccyx .
360
of the
363
Pig.                                                                                                                                                             Page.
1.   Dissection of the Metacarpus and Digit, showing the Tendons and their
Synovial Sheaths             .           .            .           .            .           .            .           .33
2.   Muscles of the Tail, deep Muscles of the Hip, and Pelvic Ligaments .            . 68
3.  Flexor Metatarsi Muscle .            .            .            .            .            .            .            .76
4.  Femoro-tibial Ligaments .            .            .            .            .            .            .            .83
5.   Ligaments of the Tarsus .            .            .            .            .            .            .            .87
6.   Diagrams showing Disposition of the Pleura? ..... 101
7.  Floor of the Thorax            ........ 120
8.  Termination of the Air Passages in the Lung ..... 122
9.   Diagram of the two Cavities of the Right Side of the Heart .            .            . 125
10.  Diagram of the two Cavities oi the Left Side of the Heart .            .            . 128
11.   Root of the Common Aorta laid open ...... 129
12.  View of a partial Dissection of the Fibre3 of the Left Wall of the Ventricles in
a Sheep's Heart ......... 131
13.    Two costo-vertebral, and two intervertebral Joints, viewed from below           . 132
14.   Two costo-vertebral, and two intervertebral Joints, viewed from above            . 133
15.  View of the Membranes of the Spinal Cord         ..... 138
16.   Portion of Spinal Cord with the Roots of the Nerves .... 139
17.  Transverse Section of Spinal Cord of Calf             ..... 141
18.  Ligamentum Nucha? and Deep Muscles of the Neck .            .            .            . 156
19.  Auricular Muscles and Nerves of a Mule ...... 161
20.   Cartilages of the Nose .            .            .            .            .            .            .            .176
21.   Hard Palate             ......... 201
22.  Muscles of the Eyeball........209
23.  Muscles of the Eyeball........210
24.  Longitudinal Section of the Head, showing the Cavities of the Mouth, Nose
and Pharynx ......... 217
25.   Transverse Section through the Nasal Chambers             .... 218
26.  Larynx, side view ......... 228
27.  Larynx, side view ......... 229
28.   Larynx, back view ......... 230
29.   Interior of the Larynx, seen from behind             ..... 231
30.  Arteries of the Brain          ........ 236
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CONTENTS.
XX
Page.
31.   Corpus Callosum and inner face of cerebral Hemisphere.            .            .            . 248
32.  View of the Lower Half of Kight Adult Human Eye, divided horizontally
through the middle          .           .            .            .            .            .            .           . 258
33.   Choroid Membrane and Iris exposed by the removal of the Sclerotic and
Cornea .......... 261
34.   Diagram of the membranous Labyrinth ...... 269
35.   Transverse Section through the Tube of the Cochlea .... 271
36.   Vertical Section through the Wall of the Duodenum, showing the Glands of
Brunner .......... 309
37.   Diagrammatic View of a small portion of the Mucous Membrane of the Colon 310
38.   Vertical Section of the Coats of a Pig's Stomach             .... 329
39.   Stomach, Everted and Inflated .           .            .            .            .            .            .330
40.  Longitudinal Section of a Portal Canal, from the Pig .... 331
41.   Transverse Section through the Hepatic Lobules             .... 332
42.   Cut Surface of Horse's Spleen, Trabecular Framework .            .            .            . 333
43.  Vessels of the Kidneys and Uriniferous Tubules              .... 335
44.  Bladder and Intrapelvic portion of the Urethra opened from below .            . 348
45.   Section of the Cat's Ovary.......353
46.   Kight Ovary and Fallopian Tube ....... 354
47.   Generative Organs of the Mare, viewed from above .... 356
48.  Muscles of the Tail, Deep Muscles of the Hip, and Pelvic Ligaments .            . 361
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CHAPTER I.
DISSECTION OF THE ANTEKIOK LIMB.
THE PECTORAL BEGION AND THE AXILLA.
As the first step in the examination of the fore limb, the student should
dissect the structures which pass between the trunk and the ventral
aspect of the limb.
Position.—The subject should be placed on the middle line of its
back, and its limbs should be forcibly drawn upwards and outwards by
ropes running over pulleys fixed to the ceiling. If only one side is
being dissected, the subject may be inclined as in Plate 1. This will put
the muscles and other structures on the stretch, and thus facilitate their
dissection.
Surface-marking.—In the fore part of the pectoral region the student
will notice the well-marked prominence formed by the anterior super-
ficial pectoral muscle. Between this muscle and the lower edge of the
mastoido-humeralis there is' a groove in which will afterwards be
dissected the cephalic vein and a branch of the inferior cervical artery.
Extending inwards from the point of the elbow is a prominent fold of
skin over the hinder edge of the posterior superficial pectoral muscle.
Directions.—An incision through the skin, but not deeper, is to be
made along the middle line of the sternum, from the ensiform cartilage
as far forwards as the cariniform cartilage. From the middle of this
incision another is to be carried transversely outwards, and terminated
a little beyond the elbow-joint. Where this second incision stops,
another is to be made across the inner face of the fore-arm. Beginning
at the point where these incisions meet, the student should raise and
turn outwards the two flaps of skin, so as to denude the superficial
pectoral muscle. In doing this, it may be noticed that here, as in other
unexposed situations, the skin is comparatively thin. Beneath the skin is
the subcutaneous fascia, and search is to be made in it for the cutaneous
nerves of this region.
Cutaneous Nerves. A nerve of considerable size, derived from the
oth cervical nerve (Plate 1), crosses the groove between the mastoido-
nimeralis and the anterior superficial pectoral, and distributes branches
to the skin over the latter muscle and part of the posterior superficial
pectoral. Other small cutaneous twigs, which are branches of the inter-
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PLATE I
Subcutaneous thoracic nerve
Subcutaneous thoracic vein
Panniculus
Post, deep pectoral ;
Ant. subcutaneous vein
Cephalic vei:
Ant. superficial pectoral
Mastoido-humeralis
Post, superficial pectoral
Inf. cervical artery
Cutaneous nerves from 6th cervical-
Ant, deep pectoral-
Sternal band of panniculus
s
Drawn fcFrmlea by V VA K John«ton. Ednjburgn fc London
PECTORAL REGION
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2
THE ANATOMY OF THE HORSE.
costal nerves, appear near the middle line, and are directed transversely
outwards.
Directions.—The surface of the superficial pectoral muscles should
now be carefully cleaned by the removal of the subcutaneous fascia;
and this operation should be conducted by beginning at the anterior or
posterior border of the muscle and working parallel to the direction of
the muscular fibres. When this has been effected, a line will be seen
on the surface of the muscle; and by dissecting carefully down on this
line, the student will be able to separate the anterior from the posterior
part of the muscle. Search is to be made, in the groove already men-
tioned, for the cephalic vein, and the fat is to be carefully removed from
the vein and its accompanying arterial branch.
Superficial Pectoral Muscle (Pectoralis transversus of Percivall).—This
muscle is divided, though not very distinctly, into two portions, which
may be distinguished as the anterior superficial pectoral and the pos-
terior superficial pectoral.
The Anterior Superficial Pectoral (Plate 1) arises from the first
two or three inches of the inferior border of the sternum, its posterior
fibres overlapping the anterior part of the next muscle. It is inserted
into the external lip of the musculo-spiral groove.
The Posterior Superficial Pectoral (Plate 1) arises from the inferior
border of the sternum from within an inch of its anterior end as far
back as a point behind the 6th costal cartilage, and from a fibrous cord
which joins the muscle along the middle line to its fellow of the opposite
side. It is inserted into the superficial fascia which descends on the
inner face of the fore-arm; and a few of its anterior fibres, forming
a band about one inch in breadth, are inserted along with the preceding
muscle into the external lip of the musculo-spiral groove. At the
elbow-joint the muscle covers the posterior radial vessels and the median
nerve, but these are not to be exposed at present.
Action.—The superficial pectoral muscle is an adductor of the limb at
the shoulder, and the posterior division of the muscle is also a tensor of
the fascia of the fore-arm.
Directions.—Both divisions of the muscle are now to be cut across near
their origin, and dissected carefully from the subjacent deep pectoral;
and while this is being done, search is to be made for their nerves, which
come from the brachial plexus by passing between the two divisions of
the deep pectoral muscle. In reflecting the muscle, the dissector will
cut many small branches of the external or internal thoracic vessels.
The reflected muscles are now to be fastened outwards with- chain and
hooks, and the dissection of the deep pectoral is to be undertaken after
the cephalic vein has been examined.
The Cephalic Vein (Plate 1). This is the upward continuation
of one of the divisions of the internal subcutaneous vein of the fore-arm.
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PL A TE IT
Ant. superficial pectoral
Post, superficial pectoral
Post, deep pectoral
Ant. deep pectoi
iAnt. subcutaneous vein
Cephalic vein
*-llf. cervical art.
Brawn & Pnrnti ""jjr "W. &A K Johnston. Edinburgh It London
PECTORAL REGION
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3
DISSECTION OF THE ANTERIOR LIMB.
It ascends in the groove between the anterior superficial pectoral and
the mastoido-humeralis. In the inner third of this groove it lies on the
anterior deep pectoral, in company with a branch of the inferior cervical
artery. It empties itself into the jugular about two inches from the
lower end of that vessel.
Beep Pectoral Muscle.—This consists of two distinct divisions, which
may be distinguished as the anterior deep pectoral and the posterior
deep pectoral.
The Posterior Deep Pectoral {Pectoralis magnus of Percivall) (Plate
2) is a muscle of large size ; and its posterior part, being subcutaneous,
was visible before reflection of the superficial pectoral. It arises from the
abdominal tunic covering the external oblique and the straight muscles
of the abdomen ; from the tips of the cartilages of the 5th, 6th, 7th, and
8th ribs, and from the immediately subjacent lateral surface of the
sternum. It is inserted into the inner tuberosity of the humerus, into
the tendon of origin of the biceps, and into the fascia which retains that
muscle in the bicipital groove. By its deep face the muscle serves to
bound the axillary space ; while its upper border is closely united to the
panniculus, and bordered by the subcutaneous thoracic nerve and vessels.
The Anterior Deep Pectoral (Pectoralis parvus of Percivall) (Plate 2)
arises from the cartilages of the first four ribs, and from the immediately
subjacent lateral surface of the sternum; and, being carried upwards in
front of the supraspinatus nearly as far as the cervical angle of the
scapula, it is somewhat loosely inserted into the fascia covering the last-
named muscle. This insertion is concealed by the mastoido-humeralis,
and will be better seen in the dissection of the muscles on the outer
surface of the scapula (Plate 4). The deep face of the muscle forms
part of the inferior boundary of the axilla.
Action.—The two divisions of the deep pectoral have the same action,
■which is to pull the shoulder-joint, and thus the whole limb, backwards.
When the limbs are fixed, the muscle may to some extent act as
a muscle of inspiration.
Directions.—The deep pectoral muscles are now to be severed care-
fully about midway between their origin and insertion, and the cut
portions are to be turned outwards and inwards. Their nerves,
which come from the brachial plexus, will be found entering their
deep face; and care is to be taken of the external thoracic and
inferior cervical arteries. By the reflection of these muscles, the axilla
is exposed. Owing to the limited power of abduction at the shoulder-
Joint of the horse, the dissection of the space is attended with much
greater difficulty than in man. The best method of procedure is as
follows:—All the pectoral muscles having been cut across, the limb is
to be forcibly separated from the chest-wall; and, to permit this to
a sufficient extent, it may be necessary to cut the mastoido-humeralis in
-ocr page 26-
PLATE III
To levator and serratus
From 8th cervical
From 7th cervical
o levator ang. scap. and rhomboideus
To levator ang. scap.
Upper division > of scalenug
/ lower division t
7
From 6th cervical
From 5th cervical
To latissimus dorsi
Common trunk of circumflex
and nerve to teres major J
To subscapulars —
■To levator and serratus
-To serratus magnus
Suprascapular
To snbscapularis
—To ant. deep pectoral
/Common trunk of circumflex
land nerve to teres major
JTo latissimus dorsi
- Sub cutaneous thoracic
Post, root of median
Ulnar
Ext. thoracic art.
Axillary art.
Median
To biceps and coraco-humeralis
1st rib.
Cariniform cartilage
Suprascapular
To ant. deep pectoral
To biceps and coraco-humeralis
To superf. pectoral
kPn&lrfl V>- "W. iA K Johnston EdmTmr^h k Lor.ior.
BRACHIAL PLEXUS
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4
THE ANATOMY OF THE HORSE.
front of the shoulder. On looking into the space, the dissector will now
see it occupied by a large amount of loose, areolar connective-tissue,
which envelops its contents, and facilitates the play of the shoulder on
the wall of the thorax. This areolar tissue must be cleaned away from
the axillary vessels and the brachial plexus of nerves, but most of the
branches of these will be more conveniently followed after separation of
the limb from the trunk.
The Axilla corresponds to the arm-pit of the human subject, and is
the important space across which the large vessels and nerves for the
supply of the fore limb are transmitted.
Boundaries of the space.—In the natural movements of the limb, and
before dissection, the space can hardly be said to have any existence
except at its lower part; but in the dissected condition it may be
observed to have the following boundaries. On its outer side are the
subscapularis, teres major, and (in part) latissimus dorsi muscles. The
inner side of the space is formed by the anterior part of the chest-wall
covered by the serratus magnus, lateralis sterni, and intercostal muscles.
Inferiorly the space is enclosed by the deep pectoral muscles, and there
the space is most extensive. Superiorly the outer and inner boundaries
meet at the insertion of the serratus magnus into the scapula. The
anterior limit of the space may be taken as formed by the mastoido-
humeralis and the reflected portion of the anterior deep pectoral 5 while
posteriorly the space is closed by the pannicuhis carnosus and skin where
these are carried from the wall of the thorax over the outer aspect of
the shoulder.
The Axillary Artery (Plates 3 and 5) begins within the thorax. On the
left side it arises as one of the terminal branches of the anterior aorta; while
on the right it is a branch of the arteria innominata. It leaves the chest
and reaches the axilla by turning round the anterior border of the first
rib, below the inferior insertion of the scalenus. It crosses the axillary
space, inclining downwards and backwards; and at the anterior border
of the teres major tendon it is directly continued as the brachial artery.
In this course it gives off four vessels, viz., inferior cervical, external
thoracic, suprascapular, and subscapular; but only the first two are to
be followed at present.
The Inferior Cervical Artery (Plates 1 and 2) arises from the front
of the axillary where that vessel turns round the first rib. After a course
of about two inches it bifurcates, its superior branch passing between
the mastoido-humeralis and the subscapulo-hyoideus, while the inferior
division passes into the groove between the mastoido-humeralis and the
anterior superficial pectoral, where it has already been seen in company
with the cephalic vein.
The External Thoracic Artery (Plate 3) arises about the same point
as the preceding, but from the opposite side of the parent vessel; and
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PLATE IV
Splenitis
Levator ang. scapulae
Ant. deep pectoral
Trapezius (cervical part)
Trapezius (dorsal part)
atus anticus
Ant. deep pectoral
Mastoido-humeralis
Supraxpinatus'
Deltoid
Serratus niagnus
Caput magnum
Caput medium
Drnra fcfrimed ty w. SiA.K Johnswn Edinburgh fctondm
SHOULDEK—Outer Aspect
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DISSECTION OF THE ANTERIOR LIMB.                                     5
passing backwards in relation to the axillary surface of the deep pectorals,
it distributes branches to these, and also to the superficial pectorals. A
slender branch from it accompanies the subcutaneous thoracic vein to
the panniculus carnosus.
The Axillary Vein is the upward continuation of the brachial vein, and
is, at its lower part, posterior to the artery; but at the anterior border of
the first rib it is below the artery, and it here joins the jugulars and the
axillary vein of the opposite side, thus forming the anterior vena cava.
Directions.—The axillary vessels may now be cut as they turn round
the first rib, and the limb may be further abducted to facilitate the
dissection of the brachial plexus, which, in its first step, should be
Undertaken by the dissectors of the limb and of the neck conjointly.
The Brachial Plexus (Plate 3) is composed of the nerves for the
supply of the fore limb. It is formed by the inferior primary branches
°f the last three cervical (6th, 7th, and 8th) and first two dorsal nerves.
These, however, do not enter into it in equal proportions. The 6th
cervical sends only a very slender branch to it, while the 7th and
"th, after detaching a communicating filament to the sympathetic,
are wholly expended in it. The 1st dorsal is, with the exception of a
similar communicating filament and a slender intercostal branch, also
entirely expended in it, but the 2nd dorsal gives off, besides the
usual communicating branch, a considerable intercostal nerve before
joining the plexus.
These roots of the plexus converge towards each other, and come out
as a flat fasciculus between the upper and lower portions of the scalenus.
In descending to this point, the dorsal roots of the plexus turn round the
anterior border of the first rib, leaving on it a smooth impression near
:ts upper end. The several roots anastomose in an intricate fashion,
contributing to the formation of the various branches of the plexus, in
Proportions that the student will not be able to trace accurately in the
course of an ordinary dissection.
The manner in which the several roots of the plexus comport themselves is liable to
Khght variation, but the following is probably as common as any other :—
I- The root from the 6th cervical nerve is a slender branch detached from the division
which that nerve sends to aid in the formation of the phrenic. Passing obliquely back-
Wards on the scalenus muscle, it resolves itself into three divisions—or rather its fibres
are traceable in three groups, viz.,—1. To the suprascapular nerve; 2. to the anterior
root of the median; 3. to join branches from all the other roots of the plexus in forming
a broad, flat fasciculus from which arise the subscapular, circumflex, and musculo-spiral
nerves.
II. The root from the 7th cervical nerve gives a branch to the nerve for the serratus
Magnus, and then divides its fibres in three directions, viz.,—1. To the above-mentioned
asciculus giving off the subscapular, circumflex, and musculo-spiral nerves; 2. to the
suprascapular nerve; 3. to the phrenic, anterior root of the median, and nerve for the
anterior deep pectoral muscle.
HI- The root from the 8th cervical nerve gives a branch to the nerve for the serratus
magmis, and then sends its fibres in three directions, viz.,—1. To the before-mentioned
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PLATE V
Subscapular!*
Bupraaplnatufr
latissinius dorsi
Suprascapular
* erve to subscapular!
Aervo r ,
10 latissiimis dursi
Circumflexnei
SuPfascapular artery
«iUary artery-
•Teres major
Nerve to teres niaior
("Artery to
l]atis.-imus dorsi
Subcut. thoracic nerve
Subscapular artery
Musculo-spiral nerve
Deep humeral artery
Caput parvum
.Ulnar nerve
Ulnar artery
Scapulo-ulnaris
0st- deep pectoral
Ant- deep pectoral
Median nerve- '^^^^—
Brachial artery
Biceps
Mastoido-humeralis
Pout, radial artery
Superficial pectoral—
Cutaneous branch of ulnar nerve
8i?nnwd by "W &A K. J°1in«tan. Edinburgh fcLondoi
SHOULDER AND ARM—Inner Aspect
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G
THE ANATOMY OF THE HOUSE.
fiat fasciculus giving off the subscapular, etc.; 2. to join the cord from which arise the
posterior root of the median, the ulnar, and the subcutaneous thoracic nerve; 3. to the
anterior root of the median and the nerve for the anterior deep pectoral muscle.
IV. The roots from the 1st and 2nd dorsal nerves unite to form a common cord which
divides its fibres in two directions, viz.,—1. To join the above-mentioned cord giving off
the posterior root of the median, etc. ; 2. to join the broad fasciculus from which arise
the subscapular, etc.
The following is a list of the branches of the plexus :—
1.   The phrenic or diaphragmatic nerve (in part).
2.   The suprascapular nerve.
3.   Nerves to the pectoral muscles.
4.   The nerve to the subscapularis.
5.   Nerves to the serratus magnus and levator scapulae (cervical
portion of the serratus), the latter only in part.
6.   The circumflex nervo.
7.   Nerves to the teres major and latissimus dorsi.
8.   The musculo-spiral nerve.
9.   The median nerve (two roots).
10.   The ulnar nerve.
11.   The subcutaneous thoracic nerve.
The Phrenic Nehve. This nerve is formed by the union of two, or
sometimes three, branches. The inconstant branch comes from the
5th cervical; the other two come from the 6th and 7th respectively.
The root from the 6th nerve gives off a branch to the brachial plexus,
and then unites on the scalenus with the root from the 5th—when that
is present. The single cord resulting passes obliquely backwards and
downwards, and at the lower edge of the scalenus it joins with the root
from the 7th nerve. This last comes from the fore part of the brachial
plexus. The trunk of the nerve, as thus formed, passes backwards
between the axillary artery and its inferior cervical branch, and enters
the thorax. It is the motor nerve to the diaphragm.
The Nerves to the Levator Anguli Scapula and Ehomboideus.
In Plate 3 two nerves are seen at the upper edge of the scalenus.
They are not, strictly speaking, branches of the brachial plexus;
but come from the inferior primary branch of the 6th nerve, and
pierce the muscle either together or separately. They are distributed
to the levator anguli scapula;, and the posterior of the two is continued
in that muscle to reach the rhomboideus.
The Nerve to the Serratus Magnus is formed by the union of two
branches, which pierce the upper division of the scalenus before uniting.
These are branches of the 7th and 8th nerves respectively. By their
fusion there is formed a broad nerve, which passes backwards on the
surface of the serratus, distributing its filaments upwards and downwards.
Before fusion, the branch from the 7th gives off a nervo which is
distributed to both the levator and the serratus.
-ocr page 32-
PLATE VI
Subscapularis
Suprascapular art.
Suiiraspinatus
Musculo-spiral nerve
Circumdex nerve
Ulnar nerv_
Roots of median nerve
Axillary art,
Nerve to biceps^
and Coraco-humeralis
Coraco-hurueralis
Brachial art.
.Median nerve
M usculo-cutaneoui
Ulnar art.
>Tere8 major
Subscapular art.
Air.. t<> Latissimus dors]
Latissimus dorsi
Caput magnum
lieep humeral art.
Prehumeral art.
Caput pttrvum
Ant. radial art.
Art. to biceps
Post, radial art
Ulnaris accessoriutj
Ulnar head of 1 Flexor metacarpi
Radial head of j medius
Flexor perforans
Ulnar artery
■f----------Ulnar nerve
Flexor perforatus
Flexor meta carpi int
Int. plantar nerve
Large metacarpal art.
Branch of median to ext. plantar nerve
Branch of ulnar to ext. plantar nerve
Ext. plantar nerve
Small metacarpal art.
fcPrinwd tyV7 StA X ,lo>m»ton, Ednibut^h S: London
SHOULDER, ARM, AND FORE-ARM—Inner Aspect
-ocr page 33-
7
DISSECTION OF THE ANTERIOR LIMB.
The Subcutaneous Thoracic Nerve (Plates 1 and 3) derives its fibres
from the dorsal roots of the plexus and from the 8th cervical, but princi-
pally from the former. It accompanies the spur vein to near the flank,
being distributed with perforating intercostal branches on the deep face
of the panniculus carnosus. A branch from it unites with perforating
branches from the 2nd and 3rd intercostal nerves, and turns round behind
the limb, to be distributed to the panniculus over the shoulder and arm.
The Nerves to the Pectoral Muscles have already been referred to.
The nerve to the anterior deep pectoral leaves the fore part of the
plexus deriving its fibres from the 7th and 8th cervical nerves. The
nerve to the superficial pectoral muscle (both divisions) derives its fibres
from both roots of the median. In general, there are two nerves to the
posterior deep pectoral. The first—to the anterior part of the muscle,
comes off with the posterior root of the median, the other—to the
posterior part of the muscle, comes off in common with the subcutaneous
thoracic.
Directions.—The remaining nerves of the brachial plexus can be more
satisfactorily followed after separation of the limb from the trunk, and
the dissector should therefore now proceed as follows :—Pass a cord
round the nerves of the plexus as they emerge from between the two
divisions of the scalenus, and then cut the roots of the plexus as near
their points of origin as possible. Cut also the axillary artery and vein
at the first rib. This will allow the limb to be carried well out from
the trunk, so as to expose the serratus magnus and levator anguli
SQ&pulaa, which are now to be cleaned.
Serratus Magnus and Levator Anguli Scapula.—These muscles are,
ln the horse, not very distinctly marked off from each other, and have
therefore been frequently described as one muscle under the first
uame.
The Serratus Magnus (Plate 4) arises from the outer surfaces of the
eight (or nine) anterior ribs, its eight slips of origin forming a curved,
serrated line which gives to the muscle its name. The posterior four
of these slips inter-digitate with slips of origin of the external oblique
muscle of the abdomen (Plate 39), and are overspread by the abdominal
tunic. It is inserted into a triangular area on the ventral surface of the
8°apula near its dorsal angle, and, in common with the next muscle, into
another triangular area at the cervical angle.
Action.—It pulls the dorsal angle of the scapula downwards and
backwards on the chest-wall, causing the shoulder-joint at the same
time to move upwards and forwards; but when the limbs are fixed, it
°an become a muscle of inspiration, pulling the ribs upwards and for-
wards. In the standing posture of the animal at rest, the chest is, in
a manner, slung on the fore limbs by means of the right and left ser-
ratus muscles.
-ocr page 34-
PLATE VII
v..^-,
mm------Supraspinatus
Infraspinatus
-Teres minor
ircumflex vessels and nerves
Caput magnum
Deltoid
Caput medium
Anconeus-------
Ulnaris accessorius
Ulnar nerve and artery-
Flexor metacarpi ext.'
Biceps
Extensor metacarpi mag.
Deep flexors
Extensor suffraginis
Interosseous artery
Extensor metacarpi obliq.
Band from carpus to extensor \ ": d j j
sutfr. tendon
Subcarpal ligament
Flexor perforatus tendon
Plexor perforans tendon
Suspensory ligament
.Extensor pedis tendon
Extensor suffr. tendon
__Slip from suspensory ligament
to extensor pedis
Drawn ScrriTUed by "W &.A.X Jchn«t4n Edinburgh & -tmdo
FORE-LIMB—Outer Aspect
-ocr page 35-
THE ANATOMY OF THE HORSE.
The Levator Anguli Scapulae (Plate 4) arises from the trans-
verse processes of the last four cervical vertebra ; and its fibres converge
to be inserted into the triangular area on the ventral surface of the
scapula near its cervical angle, in common with the anterior fibres of
the preceding muscle, from which it is not distinct. The two muscles,
taken together, have a well-marked fan-like arrangement, having an
extensive convex border where they take origin, while they converge to
a comparatively narrow point at their insertion.
Action.—The levator anguli scapulas carries the articular angle of the
scapula backwards by pulling the cervical angle forwards; but when
the scapula is fixed, the right and left muscles, acting together, can
raise the cervical portion of the spinal column, or the single muscle can
incline it to one side.
The Subscapulo-hyoid. This muscle, which arises from the sub-
scapular fascia, is described with the dissection of the neck.
THE OUTER SCAPULAR REGION.
Position.—The muscles which pass between the shoulder and the
trunk, on the outer aspect of the former, must next be dissected; and,
to permit this, the subject must be placed in an entirely new position.
The standing posture of the animal is the best for this purpose ; and it
may be imitated by suspending the subject to a stout iron rod provided
with chains and hooks, and capable of being raised or lowered by means
of a system of pulleys or a small windlass.
Surface-marking.—About the centre of the region to be dissected the
student will feel the spine of the scapula, the most prominent part of
which is its tubercle. In a well-nourished, sound horse the spine should
not be very distinctly visible, but in an emaciated animal, or in one
whose scapular muscles are atrophied as an accompaniment of joint-
disease, it forms a very prominent ridge.
Directions.—An incision through the skin is to be made along the
spine of the scapula from the withers to the middle of the arm, where
a transverse incision is to be made from the anterior to the posterior
border of the limb. Another incision is to be carried along the middle
line of the back, and prolonged forwards along the neck by the dissector
of that region, and backwards to the lumbar region by the dissector of
the back. The dissectors of the three regions should here work
together, the skin being turned down as a single flap from the neck and
anterior half of the shoulder, and as another flap from the back and
posterior half of the shoulder. The skin, it will be observed, is thicker
than in the pectoral region, and it has the panniculus carnosus attached
to its inner surface. Care must be taken not to remove this panniculus
with the skin.
The Panniculus Carnosus is the muscle which enables the horse to
-ocr page 36-
PLATE VIII
Infraspinatus
Suprascapular nerve
Supraspinatus
I Branches from subscapular
(         artery
Tores minor
Circumflex nerve
Caput magnum
aput parvum
Deltoid
aput medium
Bicepa
—Brachialis anticns
—Musculo-spiral nerve
—Anconeus
Ulnarts accessorius
Musculocutaneous nerve )
(cutaneous division) J
Extensor metacarpi >
magnus               J
Ant. radial artery
Flexor metacarpi ext.
Extensor suffraginis
Ulnar nerve
Extensor metacarpi)
obliquns             f
Cutaneous branch
Branch to ext. planter nerve
Extensor pedi
Primed by W. &A X JuhTi»t/>n Edinlwar^h klimda
SHOULDER, ARM, AND FORE-ARM—Outkk Aspect {Chaurcau)
-ocr page 37-
9
DISSECTION OP THE ANTERIOR LIMB.
twitch its skin, and thus remove offending insects. It is most extensive
over the thorax and abdomen, but it is here carried over the muscles
covering the scapula and humerus. Before the muscle passes on to
the limb, it sends an aponeurotic layer inwards between the limb and
the chest-wall. At its upper border this layer is provided with a small
tendon, which becomes inserted into the inner tuberosity of the humerus,
and which will be seen when the limb is dissected from the trunk. A
nerve will be seen ramifying in the scapulo-humeral part of the panni-
culus. This turns round the posterior border of the limb; and, as
already seen, it is formed by the union of the subcutaneous thoracic
with some perforating intercostal nerves.
Directions.—The panniculus is now to be dissected away from the
limb; and in doing this in front, care is to be taken of the thin
cervical trapezius muscle, which might be mistaken for a portion of the
Panniculus.
The Trapezius in the horse has its muscular svibstance interrupted
Dy a tendinous portion, and is therefore sometimes described as two
separate muscles, distinguished as the cervical and the dorsal trapezius.
The Cervical Trapezius (Plate 4) arises from the funicular por-
tion of the ligamentum nuchse; and it is inserted into the tubercle on
the spine of the scapula, while its most anterior fibres are continuous
With an aponeurosis covering the scapular muscles. Both the deep and
the superficial face of the muscle have a thin, adherent, fibrous covering,
the direction of whose fibres is at right angles to that of the muscular fibres.
Action.—It draws the scapula forwards and upwards.
The Dorsal Trapezius (Plate 4) is continuous with the preced-
lng by the aponeurotic centre already mentioned. It arises from the
sUnimits of a few of the anterior dorsal spines, and is inserted into the
tubercle on the scapular spine.
■Action.—It pulls the scapula backwards and upwards.
Directions.—Both divisions of the trapezius are now to be severed
close to their origin, and reflected downwards; and while this is being
°-°ne, search is to be made for the branches of the 11th, or spinal
accessory, nerve, which enter their deep face. The muscles which were
covered, wholly or in part, by the trapezius, will now be exposed,
these are : the splenius, the levator anguli scapula;, the supraspinatus,
the infraspinatus, the anterior deep pectoral, the latissimus dorsi, and
the rhomboideus.
It will be remembered that in the dissection of the pectoral region
the anterior deep pectoral could not be followed to its termination.
the reflected portion of the muscle is here seen (Plate 4), but is partly
covered by the insertion of the mastoido-humeralis.
The Latissimus Dorsi (Plate 4). Though neither the origin nor
the insertion of the muscle is found here, attention should be given to
-ocr page 38-
PLATE IX
plexor i
Flexor metacarpi ined.
Branch of median to ext.
plantar nerve
-Art. to supracarpal arch.
Large metacarpal art.
Branch from ulnar to ext.
plantar nerve
Ext. plantar nerve
tetaoarpi int
post. radial art
Int- plantar nerve
Small
metacarpal art.
Ex
ensor metacarpi
oblique
lut. plantar nerve
Large metacarpal art.
Int. metacarpal vein
Flexor perforatus
Flexor perforans
Ant.
interosseous artery
Oblique branch from int.
to ext. plantar nerve
Suspensory ligament
Interosseous muscle
-Lumbricalis
Post, digital nerve
Digital art.
Digital vein
3H                    Extensor pedis
r°ni suspensory ligament
0 extensor pedis
Middle digital nerve
Ant. digital nerve
--Ligament from ergot
K Printed by W. &=A K. Johnston Edinburgh fc London
METACARPUS AND DIGIT—Innek Aspect
-ocr page 39-
10                                   THE ANATOMY OP THE HORSE.
it as it is being exposed by the dissector of the back. It arise; by an
aponeurotic tendon from the series of vertebral spines, beginning about
the 4th dorsal, and extending backwards to the last lumbar. This
tendon is succeeded by a thick muscular portion, which contracts and
passes in between the limb and the trunk, where it will afterwards be
followed to its insertion into the internal tubercle of the humerus. Its
anterior fibres will be noticed to play over the dorsal angle and cartilage
of prolongation of the scapula.
Action.—It is a flexor and an inward-rotator of the shoulder-joint.
The Rhomboideus (Plate 4), like the trapezius, comprises a cervical
and a dorsal portion. The cervical part is an elongated, narrow muscle,
which extends as far forward as the axis, and arises from the funicu-
lar part of the ligamentum nucha). Its fibres take a very oblique
direction downwards and backwards, and are inserted into the anterior
part of the cartilage of prolongation on its inner surface, being there
confounded with the insertion of the levator anguli scapulas. The
dorsal portion consists of fibres which arise from the anterior dorsal
spines, and pass in a nearly vertical direction to be inserted into
the inner surface of the cartilage of prolongation, behind the fibres of
the cervical division. It will be recollected that the nerve to these
muscles passes from the 6th cervical nerve, and reaches its destination
by traversing the levator anguli scapulas.
Action.—To pull the scapula upwards and forwards on the chest-wall.
The Mastoido-humeralis, or Levator Humeri (Plate 4). This
muscle, in the greatest part of its extent, is found in the head and
neck, where it takes its origin from the mastoid crest and the trans-
verse processes of the first four cervical vertebra;; but attention must
here be given to its insertion, which is into the external lip of the musculo-
spiral groove, after covering the shoulder-joint. It receives here some
branches from the circumflex nerve.
Action.—It is an extensor and inward-rotator of the shoulder-joint.
When the limb is fixed, it bends the neck laterally.
Directions.—The limb may now be detached from the trunk by
severing the attachment of the rhomboideus, serratus magnus, levator
anguli scapulas, mastoido-hameralis, and latissimus dorsi, the last being
cut where it plays over the angle of the scapula. Pieces of clean cloth
saturated with some preservative solution should be placed on the outer
aspect of the shoulder where the skin has been removed, while the
dissector proceeds to examine the structures over the inner surface of
the scapula and humerus.
inner aspect of the shoulder and arm.
Directions.—The dissector should now identify the terminal portions
of the muscles already dissected, and cut them off within an inch or
-ocr page 40-
Fig. Ill
Fig. I
Fig. IV
PLATE X
-ocr page 41-
11
DISSECTION OF THE ANTERIOR LIMB.
two of their insertion, except in the case of the latissimus dorsi, which
!s to be left at its present length until its nerve and artery have been
followed. The posterior superficial pectoral should be cut away on a
level with the olecranon, but care is to be taken not to disturb the
vessels and nerves which it covers. The aponeurosis which the
panniculus sends within the shoulder will now be observed, and, at its
upper border, a small glistening band passing to be inserted into the
internal tuberosity of the humerus.
The next step is to dissect out the axillary and brachial vessels, and
the remaining branches of the brachial plexus; and this is an operation
clemanding time and care. While an assistant holds the nerves on the
Wretch, the fat and areolar connective-tissue which surround them and
the vessels, are to be cleaned away piecemeal, always proceeding from
tne main trunks to the branches. In doing this, the dissector will meet
two groups of lymphatic glands.
Brachial Lymphatic Glands. The upper group consists of a cluster
Placed behind the brachial vessels, on a level with the middle of the
humerus. The lower group consists of one or two glands in relation to
the vessels, just above the elbow-joint.
The Axillary Artery (Plates 5 and 6). This vessel has already been
Seen passing in a curved direction from the anterior border of the 1st
riD, across the inner aspect of the shoulder-joint, where it rests above the
terminal insertion of the posterior deep pectoral, and on the tendon of
the subscapulars. It passes on to the teres major, and is continued as
the brachial artery. In this course it gives off four vessels, viz., the
"werior cervical, external thoracic, suprascapular, and subscapular,
the first two have already been dissected in the axilla.
The Suprascapular Artery (Plate 5) is a small, tortuous vessel
spi inging from the upper surface of the axillary artery about the middle
its extra-thoracic course. It passes upwards for a short distance,
aud then divides into branches, the longest of which passes over the
/ubscapularis to reach the anterior deep pectoral. A branch passes
1 between the subscapularis and the supraspinatus, while smaller
ranches are expended in the tendons about the shoulder.
the Subscapular Artery (Plates 5 and 6) is a comparatively large
esSel, and beyond its origin the parent trunk is much reduced in calibre.
arises at the interstice between the subscapularis and teres major
muscles; and, disappearing between these muscles, it ascends behind
ne glenoid border of the scapula, as far as its dorsal angle. It gives
a considerable number of vessels that cannot at this stage be
°ftipletely followed, but near its origin it will be seen to throw off a
.ranch which runs upwards and backwards on the latissimus dorsi
(Plate 5).
-The Brachial Artery (Plates 5 and 6) is the direct continuation of the
-ocr page 42-
PLATE XI
Fig. VI
Fig. V
Fig. IV
Fig. I
Fig. n
Fig. Ill
■ ■
JOINTS AND LIGAMENTS OF FORE LIMB
-ocr page 43-
12                                 THE ANATOMY OF THE HORSE.
axillary, which changes its name when it passes on to the teres major.
It descends in a nearly vertical direction to the lower extremity of the
humerus, where, above the inner condyle, it divides to form the anterior
and posterior radial arteries.* In its course it crosses the direction of
the humerus obliquely, and rests successively on the tendons of the teres
major and latissimus dorsi, the small head of the triceps, and the bone.
In front of it is first the coraco-humeralis, and then the biceps ; but
these are separated from it by the median nerve, which is in close
contact with the vessel. Behind the artery is the satellite vein,
posterior to which is the ulnar nerve. Its collateral branches arc : the
pre-lmmeral, the deep humeral, the ulnar, the nutrient artery of the
humerus (sometimes), and innominate muscular branches.
The Pre-humeral or Anterior Circumflex Artery (Plate 6) arises
at the tendon of the teres major, and passes in front of the humerus,
between the upper and lower insertions of the coraco-humeralis, to
terminate in the biceps or the mastoido-humeralis. Some of its fine
twigs may anastomose with divisions of the posterior circumflex.
The Deep Humeral Artery (Plates 5 and 6) arises at the lower border of
the latissimus dorsi tendon, and soon splits into three or four branches,
the larger of which perforate the large head of the triceps extensor
cubiti, while the smaller supply the small and medium heads of the
same muscle. A branch is continued round behind the humerus, in
company with the musculo-spiral nerve, to the front of the elbow-joint,
where it anastomoses with branches of the anterior radial. This
branch will not be followed at present.
Muscular Branches of the Brachial. The largest and most constant
of these is a vessel of considerable size which penetrates the lower part
of the biceps (Plate 6).
The Ulnar artery and the two terminal branches of the brachial will
be followed in the dissection of the fore-arm.
The Brachial Vein is a large vessel wdiich ascends behind the
artery, and receives branches that for the most part correspond to those
of the artery. It receives also the subcutaneous thoracic or spur vein.
Directions.—As the brachial vein generally contains a large quantity
of blood which exudes from the smaller cut branches, it will contribute
to the neatness and cleanness of the dissection if the dissector will
carefully remove the vein and all its branches before he proceeds to
follow the nerves.
The Brachial Plexus. The mode of formation of the plexus has
already been explained, and the student will recollect that he has
already followed branches from it to the levator anguli scapulas,
serratus magnus, and pectoral muscles, as well as the subcutaneous
* In Plate 6 the termination of the brachial artery has "been pulled slightly forwards iVi order to
show the origin of the anterior radial artery.
-ocr page 44-
T'LA TE XII
Sartorius —
Int. saphena vein
Saphena art._ "
Int. saphenous ne
Vastus interims
Ift-awn fc trotted ty"W tAK JoTiTi«tt.i Edm>UT^h fc-Londoi
THIGH—Innbb Aspect
-ocr page 45-
DISSECTION OF THE ANTERIOR LIMB.                                  13
thoracic nerve, and the filament furnished by the plexus to the phrenic
nerve. He can now easily identify and trace the following branches :—
The Nerve to the Latissimus Dorsi (Plate 5) derives its fibres
from the 8th cervical and the dorsal roots of the plexus.
The Nerve to the Teres Major (Plate 5)—one or more filaments,
generally deriving fibres, in common with the circumflex nerve, from
the 7th and 8th cervical roots (with possibly some fibres from the 6th).
The Nerve to the Subscapularis (Plate 5) derives its fibres from
aU the cervical roots of the plexus.
The Circumflex Nerve (Plates 5 and 6). Its fibres come from the 7th
and 8th cervical roots, and possibly also from the 6th. It turns round
behind the shoulder-joint in company with the posterior circumflex
Artery • and on the outside of the joint it supplies branches to the teres
ttunor, deltoid, mastoido-humeralis, and skin (Plate 7). It gives a twig
to the small scapulo-humeral muscle.
The Suprascapular Nerve (Plate 5), deriving its fibres from the
"th, 7th, and 8th cervical roots, passes into the interstice between the
subscapularis and the supraspinatus. It then turns round the anterior
border of the scapula; and gaining its dorsal surface, is expended in
the supraspinatus and subspinatus muscles (Plate 8).
The Musculo-spiral Nerve (or radial nerve) (Plates 5 and 6) is, at its
0rigin, the thickest of the nerves of the brachial plexus. Deriving its fibres
trorn the 7th and 8th cervical, and from the dorsal roots of the plexus, it
Passes downwards and backwards on the subscapularis and teres major
Muscles, and some little distance behind the axillary vessels, from
which it is separated by the ulnar nerve. On reaching the deep
numeral artery, it disappears in front of the large head of the triceps,
aild is continued round the humerus in the musculo-spiral groove,
v*here it rests on the brachialis anticus (humeralis externus), and, after-
Vards, at the posterior or outer border of that muscle. It reaches the
ront of the elbow-joint, being here deeply placed between the brachialis
' lvticus inwardly, and the origin of the great extensor of the metacarpus
Utwardly. Before the nerve disappears behind the humerus, it gives
lanches to the great and small heads of the triceps, and a long branch
hlch passes backward to divide under the scapulo-ulnaris for the
ttpply of that muscle. Behind the limb it supplies the medium head
of ti •
yie triceps and the anconeus, and furnishes a few cutaneous branches
"lch perforate the caput medium, or emerge at its lower part, to be
aistributed to the skin of the outer side of the fore-arm, below the
oo w. <p|ie termination 0f the nerve will afterwards be followed in
e fore-arm, where it supplies the extensor muscles and the flexor
^etacarpi externus.
■'■he Ulnar Nerve (Plates 5 and 6) derives its fibres from the dorsal
°ts of the brachial plexus. At first it lies close behind the main
-ocr page 46-
PLATE XIII
Gracilis
J Branches of obturator nerve
\\ and deep femoral art.
Femoral art.
Deep femoral artery
Common tendon of
psoas mag. and iliacus
Prepubic art.
Art. to quadriceps
Int. saphenous nerve
Ant. crural nerve
Poupart's ligament
rtorius
Branch of deep femoral art.
Rectus femoris
{Articular branoh
of femoral art.
Vastus intemus
Drawn fcTri-Med tiy V. fcA-K Jchn«wn. EdmbiirfK fcLondon
THIGH—Inner Aspect
-ocr page 47-
14
THE ANATOMY OF THE HORSE.
vessels; but as it passes downwards, it recedes from them, and passing
under cover of the scapulo-ulnaris, it reaches the space between the
olecranon and the inner condyle. Thence it descends to the back of the
fore-arm, where it will subsequently be dissected. At present it is seen
to give off only one branch, which disappears within the superficial
pectoral muscle, and afterwards becomes distributed to the skin of the
fore-arm (Plate 5).
The Median Nerve (Plates 5 and 6) is formed by the union of two roots.
The anterior of these comes from the 6th, 7th, and 8th cervical, while
the posterior is derived from the 8th cervical and the 1st dorsal. These
roots gives off some pectoral twigs, and then unite by forming a loop in
which the axillary artery rests. The nerve then descends in front of
the axillary artery and its brachial continuation, and will afterwards be
seen to accompany the posterior radial artery. The following branches
of the nerve may be found at present:—
The Nerve to the Biceps and Coraco-humeralis comes off close below the
union of the two roots of the median, or from the anterior root above
the point of union. It passes between the upper and lower insertions
of the coraco-humeralis, supplying that muscle and terminating in the
biceps.
Musculo-cutaneous branch.—This is given off from the median about
the middle of the humerus; and passing underneath the biceps, it
divides into a muscular branch for the brachialis anticus, and a cutane-
ous branch for the front of the fore-arm.
Directions.—The muscles of this region should now be examined in
the order of their description.
The Latissimus Dorsi (Plates 5 and 6). The insertion of this muscle
into the inner tubercle of the humerus is here seen. About an inch or
two from its termination the tendon gets a twist which alters the direc-
tion of its surfaces, and brings it to be inserted in front of the termina-
tion of the teres major on the same tubercle.
Action.—The muscle is a flexor and an inward-rotator of the shoulder-
joint.
The Teres Major (Plate 5). It arises from the dorsal angle of the
scapula, and from an aponeurosis between it and the subscapularis. It
is inserted into the internal tubercle of the humerus, its terminal tendon
resting in the twist formed by the tendon of the latissimus dorsi muscle.
Action.—It is a flexor and an inward-rotator of the shoulder.
The Soapulo-Ulnaris (Plate 5). This is a thin, flat muscle which
rests on the inner surface of the triceps, and is provided, in front and
above, with a thin, transparent tendon. It arises from the posterior
border of the scapula, and is inserted into the posterior border of the
olecranon, and into the fascia of the fore-arm. At its lower extremity
the muscle covers the ulnar vessels and nerves.
-ocr page 48-
PLATE XIV
eraoralarf.
on tendfltfof
)syas uaagr^Jitl iWacun
Branches of/>bturator nerve
Obturator art
Drawn ItPmiled by VI. 1A.1C John.wn. Edirftm.-gh fc Louden
THIGH—Inner Aspect
-ocr page 49-
15
DISSECTION OP THE ANTERIOR LIMB.
Action.—To extend the elbow-joint, and tense the fascia of the fore-
arm.
J-he Triceps Extensor Cubiti. This is an immense muscular mass
ich, Ayith the preceding, fills up the angle formed behind the
ulder-joint. ^ *las three divisions or heads, which may be distin-
guished as the caput magnum, the caput medium, and the caput
Parvurn.
the Caput Magnum, or large head (Plate 5), forms a great mass
nch is seen on both the outside and the inside of the limb. It arises
°ni th dorsal angle and glenoid (posterior) border of the scapula ;
' ^ it is inserted into the olecranon, there being a synovial bursa
tween the summit of that eminence and the tendon,
-'■he Caput Parvum, or small head (Plate 5), is, when compared with
e preceding, a very small muscle. It arises from the shaft of the
nierus below and behind the internal tubercle, and it is inserted into
the olecranon.
J-he Caput Medium, which is not now visible, will be dissected with
tJle outside of the shoulder.
Action of the triceps. It is an extensor of the elbow-joint, and acts
a lever of the first order, the joint, which represents the fulcrum,
eiug between the power and the weight. The large head is also a
flexor of the shoulder.
I he Subscapularis (Plates 5 and 6). This muscle is lodged in the fossa
the same name on the ventral surface of the scapula, and it arises from
e ^'hole extent of that fossa. It is inserted into the inner tuberosity
the humerus, a small synovial bursa being interposed between the
llQ-on an(j fckg \Mne_ The tendon is crossed by the origin of the
laco-humeralis, and another small bursa is here interposed, between
e tendons. Above its insertion it is closely related to the capsular
bament of the joint. The muscle is partly united in front with the
Praspinatus, and behind with the teres major.
Action.—It is an adductor of the shoulder.
-j-he Coraco-iiumeralis (or coraco-brachialis) (Plates 5 and 6). This,
. lcn is rather a small muscle, arises from a small tubercle on the inner
. e of the coracoid process of the scapula. It has two insertions, the first
0 the inner surface of the shaft of the humerus above the internal
erele, the second into a line which begins on a level with the
ernal tubercle, and runs down the anterior surface of the shaft near
5 inner border. Between these two insertions, the pre-humeral artery
and fV>
w*6 nerve to the biceps pass. The tendon of origin of the muscle
J ies out between the supraspinatus and subscapularis muscles, and
e posterior border of the muscle is related to the brachial artery.
4ction.— To adduct and flex the shoulder.
he Biceps (Plates 5 and 6). This muscle receives its name in the
-ocr page 50-
PLATE XV
f-i—Middle Gluteus
Ext. angle of Ilium
I-------Superficial gluteus
Tensor vaginae femori-s
— semitendi nosus
Biceps femoris
Urajwn ^Printed l>y"W. IcAX Johniton, Edinburgh feLondo:
HIP AND THIGH
-ocr page 51-
16                                   THE ANATOMY OF THE HORSE.
human subject from its having two heads of origin. It is also known as the
flexor brachii or coraco-radialis. It arises from the whole of the coracoid
process of the scapula with the exception of the tubercle on its inner
side, which is for the coraco-humeralis. Its strong tendon of origin
emerges from between the outer and inner tendons of the supraspinatus,
and passes over the shoulder-joint, a pad of fat separating its deep face
from the capsular ligament of the joint. The tendon, which is of fibro-
cartilaginous consistency, then plays over the bicipital groove of the
humerus, on which its deep face is moulded, and a synovial bursa
facilitates the movements of the tendon in the groove. The central
portion of the muscle, which is thick and fusiform, has numerous
tendinous intersections, and is traversed throughout by a fibrous cord.
It rests on the anterior face of the humerus, and at its lower end
terminates by a tendon which, passing over the anterior ligament of
the elbow-joint (to which it is adherent), is inserted into the bicipital
tuberosity of the radius: The tendon is partly covered by the internal
lateral ligament of the elbow. The muscle has a second insertion, in
the shape of a strong fibrous band, detached from the main tendon to
blend with the sheath of the extensor metacarpi magnus, and deep
fascia on the front of the fore-arm.
Action.—-To flex the elbow-joint, and make tense the fascia of the
fore-arm. In the first of these actions it is a good example of a lever of
the third order, where the power is applied between the fulcrum—
represented by the elbow-joint, and the weight—represented by the
distal portion of the limb. The fibrous cord which traverses the
muscle is a mechanical extensor of the shoulder-joint, as long as the
elbow is kept extended by the triceps extensor cubiti.
Directions.—The teres major from the shoulder upwards should now
be removed, in order to follow more thoroughly the course of the sub-
scapular artery with its branches, and to expose the small scapulo-
humeral muscle, which lies on the capsular ligament behind the joint;
but care should be taken, in dissecting the tendons in the neighbour-
hood of the joint, to preserve the capsular ligament intact.
The Subscapular Artery (Plate 6) springs from the axillary trunk
at the interstice between the subscapularis and teres major muscles,
and disappearing from view, runs upwards at the posterior border of the
scapula. It gives off as its most important branches :—
1.   A Muscular branch of considerable volume which passes backwards
and upwards on the deep face of the latissimus dorsi.
2.   The Posterior circumflex artery, which, turns round behind the
shoulder, passing through a triangular space bounded by the teres major,
caput magnum, and scapulo-humeralis gracilis. At the outer side of
the joint (Plate 7) it appears between the caput magnum, caput medium,
and teres minor, and is covered by the deltoid. It splits into branches
-ocr page 52-
PLATE XVI
Upper post, gluteal nerve
Lower post, gluteal nerve
Bap. ilio-siicnil ligament
Jsuliiatiuart.
(■'"teal arteries
t- gluteal nerves
Int. putlic art.
Great saoro-soiatic ligament
0,)tiii-,te""lnion terldon of the
""°r int. and piriformis
Drawn ft.Fruited by "W. &A.K Johnston, Edinburgh fcLondon
HIP AND THIGH
-ocr page 53-
17
DISSECTION OF THE ANTERIOR LIMB.
which are distributed to these muscles and the supraspinatus (Plate 7).
" ^ accompanied by the circumflex nerve.
•»• Other branches of the subscapular are as follows :—A few inches
above the origin of the posterior circumflex, a vessel is detached which
Passes backwards, and divides to supply the caput magnum. A number
smaller branches come off from the anterior aspect of the vessel, and
ai'e distributed on both surfaces of the scapula. One of these supplies
the nutrient artery of the scapula.
The Scapulo-humeralis Gbacilis is a very slender muscle. It arises
!orn tlu scapula above the rim of its glenoid cavity; and passing over
the capsular ligament of the shoulder, on which some of its fibres seem
to terminate, it insinuates itself between the fibres of the brachialis
a'iticus (humeralis externus), and is inserted into the posterior surface of
the shaft of the humerus. It is supplied by a small nerve from the
circumflex.
Action.—The muscle is too inconsiderable in size to exercise any
appreciable action on the joint over which it passes, and, probably, its
urwtion is to raise the capsular ligament and prevent its injury during
flexion of the joint,
OUTER ASPECT OF THE SHOULDER AND ARM.
Directions.—The limb is now to be turned over, and the muscles and
°ther structures on the outer side of the scapula and humerus are
t0 be dissected.
Scapular Fascia.—This is a strong, glistening, fibrous covering which
*s spread over the muscles on the dorsum of the scapula, affording by
ts inner surface an origin to many of their fibres. When traced
Awards, it is seen to be inserted into the scapula or its cartilage of pro-
rogation; while before, behind, and inferiorly, it becomes less fibrous,
lci is continuous with the fascia covering the muscles on the inner
surface of the scapula and the outer aspect of the arm. It furnishes
'epta to pass between the subjacent muscles, and it is adherent to the
. erele on the scapular spine. If an attempt be made to dissect
°ff these muscles, they will be exposed with a rough surface,
owing that they there take origin from the inner aspect of the
fascia.
J-he Deltoid Muscle (scapular portion) (Plates 4 and 7). This muscle
vas Dy Percivall erroneously termed the teres minor. It is not the
oniologue of either of the teres muscles of human anatomy, but is, most
clearly, the representative of that part of "the deltoid muscle which in
an takes origin from the scapula. A linear depression which traverses
e muscle corresponds to an imperfect division of it into an anterior
cl a posterior portion. It arises by its anterior portion from the
-ocr page 54-
PLATE XVII
Femoral artery
Great sciatic nerve
Ext. popliteal nerve
Int. popliteal nerve
•Ext. saphenous nerve
Femoro-popliteal art-
Popliteal art.
Middle straight patellar") ^
ligament J j
Inner straight patellar ligament
Int. lateral ligament of stifle
Flexor perforatum
Fopliteus
Flexor aucessorius
-Outer head of gastrocnemius
Inner head of gastrocnemius
Flexor perforans
+------Tendon of flexor perforatus
Post, tibial art.
Cutaneous nerve from post, tibial
k Pnnwd by w S..A K Jolm«wp. Edurt>wfh * I.ondoi
LEG—Inner Aspect
-ocr page 55-
18                                   THE ANATOMY OF THE HOUSE.
scapular fascia, and by its posterior portion from the dorsal angle of
the scapula. It is inserted into the deltoid (external) tubercle of the
humerus.
Action.—To abduct the humerus, and rotate it outwards. Acting
with the teres major, it is also a flexor of the shoulder.
Directions.—The last-mentioned muscle should be carefully cut at
the level of the shoulder, and reflected upwards and downwards. This
will expose the divisions of the circumflex vessels and nerve, branches
of which will be seen entering the muscle, and it will at the same time
bring into view the next muscle.
The Teres Minor (Plates 7 and 8). (This small muscle arises from the
posterior border of the scapula, from the rough lines at the lower part
of the infraspinous fossa, and from the small tubercle on the outer rim
of the glenoid cavity. Its tendon, which is crossed by a glistening
band of fascia, is inserted into the lower half of the ridge running
upwards from the deltoid tubercle to the external tuberosity.
Action.—The same as the preceding muscle.
The Infraspinatus (subspinatus, or postea-spinatns) (Plates 7 and 8)
occupies the greater part of the fossa of the same name. It arises from
the whole extent of the fossa, and from the inner surface of the scapular
fascia. It possesses two tendons of insertion, the outer of which passes
over the convexity of the external tuberosity, a synovial bursa being-
interposed, and is inserted into the upper half of the ridge connecting
that tuberosity to the deltoid tubercle. If this tendon be cut where it
plays over the convexity, the synovial bursa will be opened, and,
at the same time, the inner insertion of the muscle into the inside
of the convexity will be exposed. This inner tendon is more fleshy
than the outer, and is in contact with the capsular ligament of the
shoulder.
Action.—It abducts the humerus, and rotates it outwards.
The Supraspinatus (antea-spinatus) (Plates 7 and 8) fills the whole of
the fossa of the same name, and takes origin from it as well as from
the scapular fascia. It is bifid inferiorly, having an inner tendon
inserted into the internal tuberosity at its highest point, and an outer
tendon inserted into the corresponding point of the external tuberosity.
These two tendons are in contact with the capsular ligament of the
joint, and the tendon of origin of the biceps emerges from between them.
Action.—It is an extensor of the shoulder-joint.
Directions.—The outer aspect of the triceps extensor cubiti is here
seen; and when its surface has been cleaned, a line will be observed
running from the shoulder to the point of the elbow. Careful dissection
downwards into the mass, along this line, will separate the caput mag-
num (already described) from the caput medium, which lies below it.
While the surface of the muscle is being cleaned, some small cutaneous
-ocr page 56-
PLATE XVIII
Rectus femorli
Vastus externus
-Great sciatic nerve
Ext. popliteal nerve
'------Int. popliteal
—Origin of peroneal cutaneous nerve
Outer head of gastrocnemius
Accessory branch to ext. saphenous nerve
Ext. lateral ligament of patella
Anterior tibial nerve
Musculocutaneous nerve
Nerve to soleus
Soleus
Ext. straight patellar ligament
Middle straight patellar ligament
Ext. lateral ligament of stifle
Flexor metatarsi
Extensor pedis—
Peroneus—
-Flexor perforans
-Tendon of gastrocnemius
Ext. saphenous nerve
Tendon of flexor perforatus
Annular bands of hock
Extensor brevis
Drawl fcPnmea *y V J.A K Johnston Edinburgh fcLondan
LEG—Outer Aspect
-ocr page 57-
DISSECTION OF THE ANTERIOR LIMB.                                  19
erves from the musculo-spiral will be found to pierce the muscle, or
merge at its lower edge, and become distributed to the outer side of the
ore-arm. These should, as far as possible, be preserved.
J-he Caput Medium (Plates 7 and 8) arises, by a short aponeurotic ten-
on, from a curved line beginning on the deltoid tubercle and continued
P^ards to the external tuberosity. It is inserted into the olecranon.
Action.—Like the other divisions of the triceps, this muscle is an
extensor of the elbow-joint.
Erections.—By raising the lower edge of the last muscle and dissect-
mg upwards, the anconeus will be partly exposed; but to effect a com-
and natural separation of the two muscles, is a matter of some
difficulty.
the Anconeus (Plates 7 and 8) is a small muscle which lies above the
eci'anon fossa, and there covers the synovial membrane of the joint,
Pad of fat being interposed. It arises from the margin of the fossa,
01 is inserted into the olecranon on its outer and anterior aspect.
Action.—To assist in extending the elbow, and at the same time to
Se the synovial membrane and prevent its injury between the bones.
Erections.—If the caput medium be now severed at its origin, and
ued backwards, the musculo-spiral nerve and some branches of the
P humeral artery will, as already described, be found turning round
e humerus in the musculo-spiral groove, which is mainly filled by the
brachialis anticus muscle.
yie Brachialis Anticus muscle (Plate 8), also known as the humeralis
lcpins or externus, is lodged in the furrow of torsion on the shaft of the
Uierus, The muscle has its origin on the posterior aspect of the shaft
tag humerus i3eiow jts articular head. Its tendon, which cannot be
i °wed at present, passes in front of the elbow-joint, and is afterwards
ected under the internal lateral ligament of the joint, to be inserted
mto the radius and ulna.
Action.—-To flex the elbow-joint.
THE FORE-ARM.
Urface-inarking.—At the elbow-joint the olecranon process of the
a is distinctly seen; but the shafts of the bones of the fore-arm are
hed with muscles, except at the lower third of the inner border of
iadius, where the bone is subcutaneous. On the outer side of the
°i the elbow-joint a large muscular mass is formed by the extensor
acarpi magnus and the anterior extensor of the digit (extensor
ls)- In the livine- animal (in which it is preferable to study these
ace-markings) this is more distinctly visible, and the tendons of these
scfes and that of the lateral extensor (extensor suffraginis) may be
;^c% traced. On the inner side of the elbow-joint one may feel the
on of insertion of the biceps; and just behind the tendon the posterior
-ocr page 58-
PLATE XIX
Flexor perforatus_____A
Gastrocnemius------
Ant. tibial art.
Peroneus
Extensor pedis
Flexor metatarsi
JSxtensor brevis
Peroneus
Extensor pedis
Large metatarsal art.
Lowest annular bandcut and reflected
•H
Flexor perforatus-
Flexor perforans-
Satellite art. of plantar nerve-----1
Int. metacarpal vein-------j-
-Suspensory ligament
- Button' ot splint-bone
Lumbricalis
Slip from suspensory lig.
to extensor pedis
Digital art.
Digital vein
Perpendicular art.
Coronary plexus
I Pr-.Tited by*W IA K Jolmiuin. EJmVjr^h k londoc
METATARSUS AND DIGIT—Outer Aspect
-ocr page 59-
20
THE ANATOMY OF THE HOESB.
radial vessels and the median nerve may be felt as they lie on the bone
under cover of the posterior superficial pectoral, and they may be made
to roll under the finger. This should be practised, as the posterior
radial artery is a convenient vessel at which to feel the pulse. The
internal subcutaneous vein crosses the inner face of the fore-arm
obliquely upwards and forwards; and in the living animal, pressure at
the upper part will distend the vessel and bring it into view. At the
outer side of the carpus the prominence formed by the pisiforni bone
may be seen and felt. On the inner surface of the fore-arm, at its lower
third, the skin presents an oval-shaped, horny callosity, vulgarly termed
the chestnut. This is largest in coarse-bred animals.
Directions.—The skin is now to be carefully removed from the
fore-arm and carpus, and the cutaneous nerves and vessels are to be
sought.
Cutaneous Neeves. (1) At the front of the elbow-joint (Plate 8) the
cutaneous division of the musculo-cutaneous branch of the median appears
from beneath the biceps, and splits into two branches, one accompanying
the anterior, the other the internal, subcutaneous vein; (2) a little way
below the elbow, on its inner aspect, the cutaneous branch of the ulnar
(Plate 5) appears from beneath the insertion of the posterior superficial
pectoral, and divides for the supply of the skin of the back of the fore-arm
on both its outer and its inner side; (3) perforating the caput medium,
or emerging at its lower edge, are some twigs from the musculo-spiral
nerve, which are distributed to the skin of the outer side of the fore-arm
beneath the elbow; (4) on the outer side of the carpus (Plate 8) are the
ramifications of a cutaneous branch of the ulnar, which comes out be-
tween the tendons of the external and oblique flexors of the metacarpus.
Subcutaneous Veins.—1. The Median or Internal subcutaneous vein
begins at the inner side of the carpus, where it continues upwards the
internal metacarpal vein. It crosses the fore-arm obliquely upwards
and forwards, in company with a cutaneous nerve already described,
and divides into the cephalic and basilic veins. The Cephalic vein has
already been seen ascending in the groove between the mastoido-
humeralis and the anterior superficial pectoral to terminate in the
jugular. The Basilic vein pierces the posterior superficial pectoral
to concur in forming the bracnial vein.
2. The Anterior subcutaneous or radial vein is much smaller than the
preceding vessel. It begins at the front of the carpus, and, ascending
on the middle line of the fore-arm, it empties itself into the cephalic or
the median vein.
Directions.—The thin superficial fascia in which these nerves and
vessels are distributed should be removed to show the deep fascia.
Deep Fascia of the fore-arm.—This is spread in the form of a close-
fitting fibrous envelope around the fore-arm. Above it receives an
-ocr page 60-
PLATE XX
Serratus anticus
Kerratus posticus (three ant. slips removed)
Fl
I
W r
i>
Anext. intercostal
Drawn fc.Prrn.u4 tyV 3,. A V. Julmaxon Edrn'out^h feloaaun
CEEST-'WM.L \SUBJlCK.
-ocr page 61-
DISSECTION OF THE ANTERIOR LIMB.                                 21
isertion from the biceps, and another from the scapulo-ulnaris; below
_ continued over the carpus to form sheaths for the tendons; while
y its deep face it furnishes septa to pass between the muscles of the
fore-arm.
■directions.—The dissection of the back of the fore-arm is now to be
. rtaken. The before-mentioned fascia is to be incised along the
nes of separation of the muscles, and these are to be cleaned and
wtecl. The remaining portion of the posterior superficial pectoral
Miscle, which covers the posterior radial vessels and the median nerve
the inner side of the elbow, is to be removed; and care is to be
ven of the ulnar vessels and nerve, which are placed beneath the
Ueep fascia, on the middle line at the back of the limb.
ine Ulnar Artery (Plates 6 and 7) is a collateral branch of the brachial,
°m which it comes off at the lower border of the caput parvum. It
scends parallel to the lower border of that muscle, to the space between
0 °^ecranon and the inner condyle, where it is covered by the scapulo-
oaris. It here places itself in company with the ulnar nerve; and,
' 0SSlng beneath the ulnar origin of the middle flexor of the metacarpus,
descends to the carpus by following the tendon of the ulnar portion of
e deep flexor (ulnaris accessorius), being placed between the external
. oblique flexors of the metacarpus. At the upper limit of the carpus
concurs in the formation of the supracarpal arch, by joining a branch
ached from the large metacarpal artery. In this course it gives off
\l) the nutrient artery to the humerus (sometimes); (2) articular
nches to the elbow-joint; (3) muscular branches in the neighbour-
ed the joint, to the scapulo-ulnaris, caput parvum, and posterior
Perficial pectoral; (4) cutaneous branches to the skin on the inner
Slde of the fore-arm.
ne Ulnar Vein accompanies the artery and nerve, and at the elbow
CUrs in the formation of the brachial vein.
, e Ulnar Nerve (Plates 6 and 8) has already been partly described in
dissection of the arm. At the lower part of that region it crosses
ulnar artery, with which it places itself in company between the ole-
on and the inner condyle. It here gives off branches to the following
,a.' es :'—(1) the anterior head of the middle flexor of the metacarpus ;
\. . e ulnar head of the same muscle ; (3) the superficial flexor of the
«? (perforata); (4) the ulnar origin of the deep flexor (ulnaris
sorius). Iu tne fore-arm it descends in close company with the
s of the same name, and at the carpus it gives off the cutaneous
l Gl au"eady described (page 20). At the upper border of the pisiform
i and beneath the tendon of the middle flexor,* it joins a branch
n the median to form the external plantar nerve.
•^fiction - >iS an^ ^ *^e termination °f the nerve has been pulled slightly forwards to show its
,Vlth ihe branch from the median.
-ocr page 62-
I*£iAT£ XXI
Longissimus dorsi
Serhispinalis
Transversalis costarurn
Middle gluten
Two internal intercostals
An external intercostal
"Dra*rn &. Primed by V. ScA.K Johnston. Edinburgh fc. London
CHEST-WALL AND BACK
-ocr page 63-
22
THE ANATOMY OP THE HORSE.
The Posterior Eadial Artery (Plate 6) is one of the terminal
branches of the brachial. It is so much larger than the other terminal
branch (the anterior radial), that it might be described as the direct
continuation of the brachial, whose direction it prolongs. Beginning
above the inner condyle, it descends on the bone, and then lies over the
internal lateral ligament of the elbow-joint, and posterior to the tendon
of insertion of the biceps. It is here covered by the posterior superficial
pectoral, and is related to the median nerve, which lies close behind it,
and to its satellite veins. At this point it is favourably placed for taking
the pulse, and its situation and relations should be carefully noted.
After crossing the elbow, it inclines forwards and disappears with the
median nerve between the radius and the internal flexor of the meta-
carpus. In this position it descends to within a short distance of the
carpus, where it divides into two terminal branches of unequal size—
the large and small metacarpal arteries. It gives off the following
collateral branches :—
1.   Articular Branches to the elbow-joint.
2.   The Interosseous Artery of the fore-arm, which reaches the outside of
the limb by passing through the radio-ulnar arch. It then descends along
the outer side of the line of junction of the radius and ulna (Plate 7),
where it will be followed in the dissection of the front of the fore-arm.
3.   Muscular Branches to the flexors of the metacarpus and digit.
4.   Cutaneous Branches.
The Posterior Radial Veins. The artery is accompanied by three or
four satellite veins, which surround it and the nerve, and anastomose
freely with each other. They begin at the carpus, where they anasto-
mose with the metacarpal veins, and at the elbow-joint they unite with
the basilic and ulnar veins to form the brachial vein. They receive
branches corresponding more or less exactly to those of the artery.
The Median Nerve in the fore-arm (Plate 6). This nerve has already
been followed in the dissection of the arm, where it was seen descending
in front of the brachial artery. It preserves the same relationship to the
first few inches of the posterior radial arteiw, but at the elbow it crosses
the artery superficially to take up a posterior position. Below the joint
it again changes its position by mounting on the surface of the artery,
or it may even again place itself in front. At a variable point in the
fore-arm it terminates by dividing into two branches, one of which is
continued as the internal plantar nerve, while the other joins the ulnar
to form the external plantar. In the subject from which Plate 6 was
taken, the division took place considerably above the middle of the fore-
arm, but more frequently it occurs in the lower third. Immediately
below the elbow the nerve furnishes a branch to the internal flexor of
the metacarpus, and branches to the deep flexor of the digit (humeral
and radial heads).
-ocr page 64-
Phrenic nerve
Inf. laryngeal nerve
Post aorta
9th intercostal art.
10th nerve
A cardiac nerve,
Trachea
Thoracic duct
(Esophagus
A cardiac nerve,
Left axillary art.
Longus colli
Dorsal art,
Art. innominata
Ant. vena cava,
Sup. cervical art^
Vertebral art.
PLATE XXII
Doraal cord of sympathetic nerve
Great splanchnic nerve
Scalenus
1st rib
Jugular vein
Axillary art.
AciUary vein
Int. thoracic art.
\ (Left lung, collapsed and
) reflected
Pericardium
| Right Inng, seen through
I mediastinal pleura
Diaphragm
Dra*ni It Printed fcy1*. I.A K. Joamtun EdirrtreTgb fcLondw
THORACIC CAVITY—Left Side
-ocr page 65-
DISSECTION OF THE ANTERIOR LIMB.                                  23
Directions.—The muscles on the back of the fore-arm must now be
tearnt. These consist of the three flexors of the metacarpus, and the two
flexors of the digit.
The Flexor Metacarpi Internus (Plate 6). This muscle lies along
the inner edge of the posterior surface of the radius, where it conceals
tne posterior radial vessels and the median nerve. It arises from the
inner condyle of the humerus, just behind the point of origin of the
internal lateral ligament, where it is confounded with the origin of the
middle flexor. It terminates interiorly in a long, slender tendon, which,
after passing through a synovial sheath at the inner side of the carpus,
is inserted into the head of the inner small metacarpal bone.
Action.—It is a flexor at the carpal articulations—i.e., it flexes the
maims on the fore-arm.
The Flexor Metacarpi Medius (Plate 6). This muscle descends in
c°ntact with the posterior edge of the internal flexor. It has two heads
°i origin—an anterior and a posterior. It arises by its anterior head
Just behind the origin of the preceding muscle, and by its posterior
•lead from the upper part of the posterior edge of the olecranon. After
a course of three or four inches these two heads unite, and the single
interior tendon is inserted into the upper border of the pisiform bone.
1 ne ulnar nerve and vessels pass beneath the posterior or ulnar head of
the muscle.
Action.—The same as the preceding muscle.
The Fl exor Metacarpi Externus (Plates 7 and 8) is situated at the
outer side of the back of the fore -arm, having the lateral extensor of the
cugit (extensor suffraginis) in front of it, while behind it is separated from
ine last-described muscle by the ulnar division of the deep flexor of the
"git (ulnaris accessorius). It arises from the lowest point of the outer
!"ge bounding the olecranon fossa. At its lower end it has two inser-
*ow.s, viz., (1) into the upper border of the pisiform bone, whexe it is
c°nfounded with the insertion of the middle flexor; (2) by a cord-like
eudon which, after descending in a synovial sheath formed inwardly by
. e oblique groove on the outer surface of the pisiform bone, is inserted
nto the head of the external small metacarpal bone.
Action.—Like the preceding two muscles.
directions.—The three flexors of the metacarpus surround the flexors
the digit, and they should be cut about their middle and reflected to
bring these latter into view.
I he Superficial Flexor of the Digit (flexor pedis perforatus) (Plate
) arises, by a tendon common to it and the deep flexor, from the
wer extremity of the ridge bounding the olecranon fossa on the inside.
8 muscrdar belly contains much tendinous tissue, and cannot without
itticulty be separated from the deep flexor, on which it rests. At the
wer part of the radius its muscular portion is succeeded by a tendon,
-ocr page 66-
PLATE XXIII
Art. innominata
Sup. cervical art.
Ant. aorta
Trachea
Jugular vein
Common carotid art.
Vertehral art.
Vertebral vei
Thoracic duct.
Inf. cervical art.
Cephalic vein
Ext. thoracic art.
Axillary vein
Int. thoracic art.
Int. thoracic vein
Common aorta
Hth intercostal art.
Post aorta
(.Esophagus
Post, vena cava
Right ventricle
krmuei by7» VA K JuhnsUm EAinbur^h kIonian
H¥iKR,T A^D GTfc'&A.T YBSSEU&—V.W? Sttya
-ocr page 67-
24                                   THE ANATOMY OP THE HORSE.
which, after being reinforced by a fibrous band from the back of the
radius, passes through the carpal sheath behind the carpus, and is
ultimately inserted by a bifid tendon into the second phalanx. The
examination of this and the succeeding muscle, from the carpus down
wards, must be postponed till the dissection of the metacarpus and
digit is undertaken.
Action.—The muscle flexes successively the pastern, fetlock, and
carpal joints.
The Deep Flexor, of the Digit (flexor pedis perforans) (Plate 6).
This muscle is situated in contact with the posterior surface of the
radius, and consists of three divisions, which may be distinguished as
the humeral, the radial, and the ulnar portions. The humeral or main
division arises, in common with the preceding muscle, from the lower
extremity of the ridge bounding the olecranon fossa on the inside. The
radial portion, or radialis accessorius, is deeply placed, and arises from
the back of the radius. The ulnar division, or ulnaris accessorius. is
placed beneath the deep fascia of the fore-arm, where it lies between the
external and oblique flexors of the metacarpus, and is accompanied by
the ulnar nerve and vessels. It arises from the summit and posterior
border of the olecranon. These three divisions unite above the carpus,
and have a common tendon which passes through the carpal sheath,
and is ultimately inserted into the os pedis.
Action.—It flexes successively from below inwards the inter-phalan-
geal joints, the fetlock, and the carpus.
Directions.—The front of the fore-arm must now be dissected; and
here it will be convenient to turn attention in the first place to muscles;
but while these are being isolated, care is to be taken of the interosseous
vessels, which descend along the lateral extensor at the outer side of the
region, and of the tendon of the oblique extensor where it crosses over
the tendon of the extensor metacarpi magnus above the carpus.
The Extensor Metacarpi Magnus (Plates 7 and 8) corresponds to the
long and short radial extensors of the wrist in the human subject. It is
a powerful muscle, having at its upper end a massive muscular belly,
which tapers downwards, and terminates a few inches above the carpus
in a tendon. It arises from the anterior and upper part of the outer
ridge of the olecranon fossa (the outer condyloid ridge), where this ridge
bounds the musculo-spiral groove ; and by a second tendon, in common
with the extensor jiedis, from a depression which is placed external to
the coronoid fossa. Its inferior tendon lies in the largest and most
internal of the vertical grooves at the lower end of the radius ; and after
gliding over the front of the carpus in a synovial sheath, it is inserted
into a special tubercle on the upper end of the large metacarpal bone at
its inner side.
Action.—It extends the manus on the fore-arm.
-ocr page 68-
Common aorta
j Ant. aorta
Ant. vena cava
J Lorso-cervical vein
Art. Innominata
Dorso-cervieal art.
Vertebral vein.
PLATK A'XIV
(Esophageal art. (snp./
I Bronchial trunk dividing
j j Broncho-oasophageal art.
!>th Intercostal art.
.Trachea
-Common carotid art
Vertebral art.
.Jugular vein
Cephalic trunk
Axillary art.
Inf. cervical art.
Axillary vein
Ext. thoracic art.
Post aorta
Right bronchus
(Esophagus -
^^^^^^^^^^^^ Left bronchus
Pulmonary veins
Sinus venosus of right auricle
Post. «na cava
Int. thoracic vein
Int. thoracic art.
—Right auricular appendix
Right ventricle
Left coronary art.
Drawn JcPrinted by"W J*A.X Johnston, F.faiiburgn fcLondoj
HEART AND GREAT VESSELS—Right Side
-ocr page 69-
25
DISSECTION OF THE ANTERIOR LIMB.
J-he Extensor Metacarpi Obliquus (Plates 8 and 9). This is the re-
| es6»tative of the extensor muscles of the thumb in man. It arises from
e outer side of the radius; and its tendon, after passingoblig uely
__ ^ awards and inwards over that of the great extensor, is inserted into
e head of tile inner small metacarpal bone. It lies in an oblique
. 00Ve at the lower end of the radius, where the play of its tendon
acilitated by a small synovial bursa.
rJ:tlon-—Like the preceding muscle.
ihe Extensor Pedis, or anterior extensor of the digit (Plate 7),
presents the extensor communis digitorum of man. At its origin it
^mediately to the outer side of the extensor metacarpi magnus, but
he lower part of the fore-arm the extensor metacarpi obliquus emerges.
^ between the two muscles. It arises, by a tendon common to it
the extensor metacarpi magnus, from a depression external to the
°uoid fossa ; also from the external lateral ligament of the elbow, and
le external tuberosity at the upper end of the radius. It consists of
° parallel portions of unequal size, and these are succeeded by two
«ons which lie close together, but are distinct from each other.
ese tendons pass in common through a vertical groove at the lower
°t the radius, and over the front of the carpus, where they are pro-
eti with a synovial sheath. In the dissection of the metacarpus and
s11! the tendons will be pursued to their insertion, the outer and
auer * joining the tendon of the extensor suffraginis, while the inner
main tendon becomes inserted into the pyramidal process of the os
Pedis.                                                                 .
ction.—This muscle extends in succession the interphalangeal joints,
*etloek, and the carpus.
Qe Extensor Suffraginis, or lateral extensor of the digit (Plates 7
and S\ •                                                                    .                          .
, . /> ls a smaller muscle than the extensor pedis, to the outer side of
11 it lies. It is the homologue of the extensor of the little finger in
Ulan t
it arises from the external lateral ligament of the elbow, from the
. nal tuberosity at the upper end of the radius, from the line of
' Wn of the radius and ulna, and from the outer border of the radius.
. 6n passes first through a vertical groove on the external tuber-
- at the lower end of the radius, then through a synovial sheath at
. uter side of the carpus, and it will subsequently be followed to its
' SeJtion into the first phalanx.
c ion..—it jg au extensor 0f the fetlock and of the carpus.
Sections.—The nerves and bloodvessels on the front of the fore-arm
.f Uext be sought, and in order to fully expose them, some of the
Oomg muscles must be cut. The biceps is to be cut about its
* Th'
of the pre" sometimes termed the muscle of Phillips. Occasionally there occurs, to the inner side
before re, i'.1""' another and smaller fasciculus, with a slender tendon which joins the main tendon
' c "ng the carpus. Tlr.s is the muscle of Thiernesse.
-ocr page 70-
PLATE
Great splanchnic nerve
Post.aorta
ung, collapsed and reflected
Intercostal vessels
Diaphragm
Great vena azygos
Dorsal cord of sympath. nerve
ngus colli
cardiac branch of 10th nerve
0th nerve
.Trachea
orso-cervic&l vein
Dorso-cervical art.
-Vertebral vein
Ant. vena cava
Scalenus
1st rib
Phrenic nerve
Ant. mediastinum
ight auricle
Bight coronary art.
Bight ventricle
X Printed ty "W. &A.K. Jul ■                              - It Landoj
THORACIC CAVITY—Right Side
-ocr page 71-
26                                   THE ANATOMY OF THE HORSE.
middle in order to follow the anterior radial artery; and by dissecting
deeply down in front of the elbow, between the brachialis anticus and
the extensor metacarpi magnus, the artery will be found to meet the
musculo-spiral nerve. The extensor metacarpi magnus is to be cut
about its middle and carefully reflected in order to follow the artery,
which lies in relation to the deep face of the muscle; and the extensor
pedis is to be similarly reflected to trace the termination of the mus-
culo-spiral nerve.
The Anterior Kadial Artery (Plate 8) is the smaller terminal
branch of the brachial. It separates at an acute angle from the pos-
terior radial, and passes forwards beneath the biceps and then beneath
the brachialis anticus. It meets the musculo-spiral nerve in the inter-
space between the brachialis anticus and the extensor metacarpi magnus,
and afterwards descends on the anterior surface of the radius, where it
is covered by the last-mentioned muscle. It terminates at the carpus
by anastomosing inwardly with branches from the posterior radial, and
outwardly with the interosseous artery of the fore-ami. It supplies
articular branches to the elbow, and muscular branches to the muscles
on the front of the fore-arm.
The Interosseous Artery of the fore-arm (Plate 7) is a branch
given off by the median at the back of the fore-arm. It comes out-
wards through the radio-ulnar arch, and descends along the extensor
suffraginis, terminating in slender branches in front of the carpus.
It supplies articular branches to the elbow; the nutrient artery of the
radius; and muscular twigs to the extensor suffraginis, extensor pedis,
and extensor metacarpi obliquus.
The anterior radial and interosseous arteries are, generally, compara-
tively slender vessels, but they are liable to some variation in size and
distribution, and the one may partly supplant the other.
Veins. Satellite veins of the same names run in company with the
foregoing arteries.
The Musculo-spiral Nerve in the fore-arm (Plate 8). In the dissec-
tion of the axilla and arm, this nerve has already been seen as a large
trunk descending from the brachial plexus, and taking a spiral course be-
hind the humerus. It reaches the front of the elbow, where it meets the
radial artery in the interspace between the brachialis anticus inwardly,
and the origin of the extensor metacarpi magnus outwardly. It here
gives off branches to the extensor metacarpi magnus, extensor pedis,
extensor suffraginis, and flexor metacarpi externus; and, much
reduced in size, it descends between the shaft of the radius and the
extensor pedis, and terminates in the extensor metacarpi obliquus. The
nerve to the flexor metacarpi externus is furnished after the branches to
the extensor pedis, and passing outwards between the latter muscle and
the bone, it penetrates its muscle at the radio-ulnar arch.
-ocr page 72-
PLATE XXVI
Pulmonary art., right branch
10th nerve, emitting cardiac branches
Cardiac nerve from mid. cerv. ganglion
Inf. cerv. ganglion
Inf. laryngeal nerve
Mid. cerv. ganglion
Jrachea
Cervical cord of
sympathetic nerve
10th nerve
Common carotid art.
Jugular vein
Vertebral art.
Phrenic nerve
Sup. cervical art.
Axillary vessels
Ext. thoracic art.
Dorso-cervical art.
NArt. innominata
Ant. vena cava
Int. thoracic vessels
Ant. mediastinum
Bight coronary art.
Heart
Cut edges of pericardium
■ nied by W. kA K Johimbin E.lm.-.
Left bronchus
Intercostal vessels,
(Esophageal art.
Sup. oesophageal nerve.
Great splanchnic nervi
Dorsal cord of sympathetic nerve
Post, aorta
Great vena azygos
Diaphragm
Oesophagus
Inf. oesoph. nerve
Left lung
Post, vena cava
Pulmonary veins
Phrenic nerve
THORACIC CA.VITY—Right Side
-ocr page 73-
DISSECTION OF THE ANTERIOR LIMB.                                  27
Sections.—In this stage of the dissection the student will be better
to trace the musculo-cutaneous branch of the median nerve, and the
iq\ °n8 °^ *he biceps and brachialis anticus muscles (see pages 16 and
y)- When these have been examined, he may, as the next step, either
ssect the articulations of the shoulder and elbow (pages 41 and 43), or
nay saturate the parts already dissected with some preservative solu-
n> and postpone the examination of these joints till after the dissec-
>°n of the metacarpus and digit,
THE METACARPUS AND DIGIT.
e distal portion of the horse's fore limb, beyond the lower extremity
the radius, is technically termed the manus, as it corresponds to the
1 of man. The carpus, or,' as it is commonly but erroneously
fted, the knee, of the horse corresponds to the wrist of the human
Ject. The portion of the limb between the carpus and the fetlock,
Presenting the palmar portion of man's hand, is called the metacarpus ;
j e the rest of the limb, beyond the fetlock, is the digit, and is the
omologue of man's middle-finger.
' Urfuce-marhing.—By flexing the carpal and fetlock joints, the splint
es may be felt at the back of the metacarpus. Behind the bones in
same region lie the flexor tendons, the subcarpal ligament, and the
1 Peiisory ligament. These, whose edges may be more or less distinctly
m a well-bred animal, have the relation to each other shown in
„ ' e '■ Behind the fetlock-joint is a tuft of hair in which will be
p         a horny spur or ergot, which is largest in coarse-bred animals.
J Manipulation, the flexible lateral cartilages may be felt above the
°°f> in the region of the heels.
fi li V>ectlons-—The entire remaining portion of skin should now be care-
} removed from the limb. Should it be intended to study from the
e Preparation the parts contained within the hoof, this must, before
removal of the skin, be detached by for ce in the manner described
it i ^6          '^e various structures are now to be defined by dissection
ii . le 01*^ei' of the following description; and while the vessels and
IS are being cleaned, care must be taken of the small lumhricales
r_ ' es, which lie on the tendon of the deep flexor above the fetlock.
A\ P mav arterial arches cannot be fully exposed at this stage of the
re'. ou' hut it is convenient to describe them here, from their
°nshir> to the wssaIs nf the
tap to the vessels of the region. The same applies to the
l
jj Metacarpal artery and the plantar nerves behind the carpus,
'hich can be fully traced in the examination of the carpal sheath
(P;Jge 33).
ai,, e, Large Metacarpal Artery (Plate 9). This is the largest
2 in the part of the limb now exposed, and is, by means of its ter-
-ocr page 74-
PLATE XXVII
Parotido-au ocularis
Submaxillary gland
Parotid gland           SptonilM
Trapezius
M astoido-hu meralis
k
Sternal band of panniculus
Nv^higular vein
Common caftrtid »rt>: "
Subscapulo-hyoideus
Sterno-maxillaris
Submax. lymph, glands
Submaxillary art.
V, ]«buua y.Air.i.unA. ^ Loninn
V.Y.*.VVS. rOtJ.V> Y^YVA*.-^ tOCtt A.JVAOT SSXC*
-ocr page 75-
28
THE ANATOMY OF THE HOUSE.
minal branches, the main vessel of- supply to the digit. It has already
been seen at its origin, as the larger of the two terminal branches of the
posterior radial artery; and, indeed, from its volume and direction, it
might be described as the direct continuation of that vessel. From its
point of origin at the lower end of the radius, it descends in company
with the flexor tendons, by passing behind the carpus and beneath the
carpal arch. Emerging from beneath the last-named structure, it con-
tinues to descend on the inner side of the flexor tendons until a little
above the fetlock, where it sinks slightly inwards to bifurcate into the
digital arteries. From the carpus downwards the artery is related to
the internal metacarpal vein, which ascends in front of it, and to the
internal plantar nerve, which is in contact with it posteriorly. The
relative position of the three structures should be carefully noted in
reference to the higher operation of neurotomy. Only two of its
collateral branches are of sufficient size to merit description, and both
are somewhat irregular in their origin. The first of these comes
off near the origin of the parent vessel, and may come from the
posterior radial itself. It crosses behind the lower extremity of the
radius, and anastomoses with the termination of the ulnar artery to
form the supracarpal or superficial palmar arch. The second is an
un-named vessel which springs from the large metacarpal at or near its
point of bifurcation, and divides into branches that ascend to anastomose
with the interosseous metacarpal arteries.
The Supracarpal or Superficial Palmar Arch is formed behind the
lower extremity of the radius, by the junction of the above-mentioned
branch of the large metacarpal artery with the termination of the ulnar.
The convexity of the arch is turned downwards, and from it there arise
several branches. The largest and most regular of these descends
within the carpal arch, and joins the small metacarpal artery to form
the subcarpal or deep palmar arch, which will be dissected at a later
stage.
The Digital Arteries (Plates 9 and 10) are the terminal branches
of the large metacarpal artery. They separate at an acute angle, the
outer one passing above the fetlock, between the deep flexor and the
suspensory ligament. Each passes over the side of the fetlock-joint, and
descends at the edge of the flexor tendons as far as the inner face of
the basilar process, where it bifurcates to form the plantar and pre-
plantar arteries. Each artery is related in front to the vein of the
same name, and behind to the posterior branch of the plantar nerve.
The anterior branch of the same nerve crosses the vessel at the
fetlock; while other twigs cross over the artery and form the
middle branch, which will be found between the artery and vein, or
resting on the former. Crossing these vessels and nerves obliquely,
is a small glistening ligamentous cord (Plate 9) which stretches
-ocr page 76-
PLA TE XXVIfl
Occipital art
Int. carotid art
Ext. carotid art.
Pth new
Post, auricular art.
Ant. auricular art.
7th nerve
Trans, facial art.
Trapezius
Preseapular glands
Inf. cervical art.
Msatoido-hnmeratu
Jugular vein
Sterno-max illari.s
Division of ext. carotid intO(
superf. temp, and int. max J
Maxillo-musc. art. —i
Submaxillary aft.
12th nerve
~"T
Sternal band
of panniculus
NUrnothyro-hyoideus
!/OituQon carotid art.
Subscapnlo-'hjoideiis
Inf. laryngeal nerve*"**-
(Esophagus
Trachea
Drawn fcPriwed fcy "W ScA.K John»lfln. Edinburgh & Londoi
NECK
-ocr page 77-
DISSECTION OP THE ANTERIOR LIMB.                                  29
'awards and forwards from the horny spur behind the fetlock,
corning attached within the wing of the os pedis. A knowledge of
lese relationships is of importance for the performance of the lower
1 Nation of neurotomy. The collateral branches of the digital
arteries are :—
•   At different levels numerous small branches for the skin, tendons,
| * "dilations. Among these may be included the rameaux echelonnes
. ^ouley (Plate 10). These branches, some of them of considerable
A spring from the posterior aspect of the artery, and anastomose
ss tar back of the digit with corresponding branches from the oppo-
e 8lde, forming arches arranged like the steps of a ladder.
,, ' ^ne Perpendicular Artery, which comes off at a right angle about
middle of the first phalanx, and divides almost immediately into an
ending and a descending set of branches, both of which are distri-
e°- on the front of the first phalanx. Branches from each of those
anastomose with corresponding vessels from the opposite side.
•   -I he Artery of the Plantar Cushion.
•   v essels forming the Coronary Circle.
.„ e last two, as well as the terminal branches of the digital arteries,
Will 1
°e described in connection with the foot.
ne Small Metacarpal Artery (Plate 9). This, the smaller
"inial branch of the posterior radial artery, descends behind the
e and towards its inner side. It is superficially placed to the
., °Us band completing the carpal arch, while the large metacarpal
k beneath that structure. In company with it is the first part of the
ian vein. At the level of the head of the inner metacarpal bone it
ses to the outer side by passing between the suspensory ligament
, the subcarpal ligament, or check-band furnished from the
°i the carpus to the tendon of the deep flexor. It here anasto-
° 8 with a branch already described as descending from the supra-
' rf ai"ch. In this way the subcarpal arch is formed.
ne Subcarpal or Deep Palmar Arch gives off the following two
Pa^ of ai.teries :_
ihe Anterior or Dorsal Interosseous Metacarpal Arteries.—These
for\Sma11 vessels (Plate 9)>
one on each side of the limb, which turn
tv, a round the heads of the small metacarpal bones, and descend in
grooves between these bones and the large metacarpal. They
a t'16 skin an(l subjacent structures on the front of the metacarpus,
anastomose above the fetlock with divisions of the artery springing
the large metacarpal at its point of bifurcation.
•   -l he Posterior or Palmar Interosseous Metacarpal Arteries.—These
end on the edge of the suspensory ligament, each being internally
lit ^° *^e 8maU metacarpal bone of its own side. They anastomose
he preceding, and supply small branches to the suspensory ligament
-ocr page 78-
Parotido-auricularis
I
Maxillo-ruuseular vessels
Parotid gland
7th nerve
Masse ter
PLATE XXIX
Orbital art. from sup. dental
Levator labii sup. proprius
Angular branches of submax. vessels
Zygomaticus
Levator labii sup. alseque nasi
Buccinator
Dilat. naris lateralis
Depressor labii inf.
Orbicularis oris
Submaxillary vein
Submaxillar; art.
N**al branches of vubmax. vessels
Drawn fc Primed bj » UA.K Jonn«oon EdiriVnrtfi It London
SlDte OT ¥AOK
-ocr page 79-
30
THE ANATOMY OF THE HORSE.
and flexor tendons. One of them gives off the nutrient artery of the large
metacarpal bone. They arc of unequal size, the outer being the larger.
The Digital Veins (Plate 9). These are the satellites of the digital
arteries, in front of which they ascend. They drain away the blood
from the venous plexuses within the hoof, and, uniting with one
another above the fetlock, they form an arch between the deep flexor
and the suspensory ligament. From this arch spring the metacarpal veins.
The Metacarpal Veins are three in number:—
1.   The Internal Metacarpal Vein (Plate 9), which is the largest of
the three, ascends in front of the large metacarpal artery, on the inner
edge of the flexor tendons. At the inner side of the back of the
carpus it is continued as the median vein.
2.   The External Metacarpal Vein is similarly disposed on the outside
of the flexor tendons, in company with the external plantar nerve. At
the carpus it divides into several anastomosing branches, which are
continued as the ulnar and posterior radial veins.
3.   The Interosseous or Deep Metacarpal Vein is an irregular vessel
ascending between the suspensory ligament and the inner splint bone.
At the back of the carpus it breaks up into branches that anastomose
with the external and internal metacarpal veins.
The Plantar Nerves (metacarpal nerves of Percivall).—These are the
nerves which confer sensibility on the digit, and which, in their main
trunks, or in one of their terminal branches, are cut in the operation of
neurotomy. They must therefore be dissected with great care, and the
student must make himself thoroughly acquainted with their situation
and relations.
The Internal Plantar Nerve (Plate 7). This is one of the ter-
minal branches of the median nerve. Beginning at a variable point
above the carpus, it passes within the carpal arch, in close company with
the large metacarpal artery, both resting on the side of the deep flexor
tendon. Here the norve crosses beneath the artery, to place itself
behind it. Throughout the metacarpal region the same relationship
is preserved, the nerve lying immediately behind the artery, in front
of which is the internal metacarpal vein. Just above the fetlock the
artery sinks in somewhat more deeply than the vein and nerve, and
thereby allows these to approach each other. In the higher operation
of neurotomy the nerve is cut a little way above the fetlock, and before
it divides. About the middle of the metacarpus it gives off a consider-
able branch which winds obliquely downwards and outwards behind the
flexor tendons, to join the external plantar nerve an inch or more above
the button of the splint bone. At the level of the sesamoid bones the
trunk of the nerve divides into three digital branches, which are
distinguished as anterior, middle, and posterior. These are of very
unequal size, the posterior being much the largest, and also the most
-ocr page 80-
PLATE XXX
Inf. dental vein
Inf. dental art.
Inf. dental nerve
it. pterygoid
Mylo-hyoid nerve
uecal vein
,Great hyo-glossus
tylo-glossus
Lingual nerve
Infra-orbital nerves
.Levator labii sup. proprius
Sublingual gland
ylo-byoideus
Parotid gland
Subscapulo-hyoid
Int. pterygoid'
Genio-hyoideuj
Dr^n kfraiwd \>y W i. A K .lohi>«toii EdmVurpi fc Lon.lw
CANITY OY THE MOTJTH.
-ocr page 81-
DISSECTION OF THE ANTERIOR LIMB.                                  31
1 ortant, as it is tho nervo which is cut in the lower operation of
eurotomy when performed for navicular arthritis. The middle is the
uestartd most irregular, and all three branches are in close relation-
shlP with the digital vessels.
Tl i
18 Anterior branch descends in front of the vein, distributes cutane-
wanches to the front of the digit, and terminates in the coronary
cushion.
he Middle branch, which is small and irregular, descends between
artery and vein. It is generally, as in Plate 9, formed by the
n Of several smaller branches which cross forwards over the artery
re uniting- and it terminates in the sensitive laminae and coronary
cushion.
. i -Posterior branch lies close behind the arteiy, except at the fetlock,
"e the nerve is almost superposed to the artery. It accompanies the
&* al artery into the hoof, and passes with the preplantar branch of
W- Vessel to De distributed to the os pedis and the sensitive lamina).
m the hoof it gives off several branches, which for the most part
' °mPauy the arteries.
_ he External Plantar Nerve (Plate 9). This is formed by the
, a or the termination of the ulnar nerve with one of the terminal
of            °^ *ne median. These two branches unite at the upper border
to i . Plsiform bone, beneath the middle flexor of the metacarpus.
tP                carpus the nerve inclines downwards and outwards, in the
re of the annular ligament that completes the carpal sheath. In
on «. caipal region it occupies, on the outside of the limb, a position
0          nexor tendons analagous to that of the internal plantar nerve
onl ° llls^e- Unlike the latter nerve, however, it is accompanied by
j a single vessel—the external metacarpal vein, which lies in front of
tli n. ln°k or niore above the button of the splint bone it is joined by
ique branch from the internal nerve. In the higher operation
1a, \ 10tonry it is cut at the same point as the inner nerve. At the
sj .. W1e sesamoid bones it divides into three digital branches, exactly
Tv.        those of the internal nerve already described,
tern P antar nerves give filaments to the lumbricales and interossei
sj and to the suspensory ligament,
foil • ow&—The student must now pursue the dissection of the
yjz 8 muscles which have already been dissected in the fore-arm,
limV,        extensor pedis and extensor suffraginis on the front of the
tw'         ^he superficial and deep flexors behind. In addition to these,
to
j, . ne lumbricales and interossei muscles, which entirely belong
°ver, e»10n; and, as they are of small size, and might easily be
Tl ° t tlleir ^is8eoti°n must be first undertaken.
hum,0 i rBRI0ALEs Muscles (Plate 9) receive their name in the
1 net, from their resemblance to a common earthworm. In the
-ocr page 82-
PLATE XXXI
Great coron of hyoid
Buixnl nerve,         Inf. dental nerve
Mylo- hyoid nerve
Guttural pouch
• and temporal
Nerve to int.l
'X Pterygoid/'
Tensor palati
Pterygo-pharyngeus
Lingual nerve
Great hyo-glossus
Stylo-glossus
^            /            Genio-glossus
^wp. ^v        -~^,si»-                 7*--. Wharton's duct
Subzygomatic nerve
Int. maxillary art...
7th nerTev
Superf. temp. artv
Ext. carotid art..
Occipito-styloid.
Stylo-hyoid.
Digastricus, upper belly_
Stylo-maxillaris ..
Submaxillary glands
Crico-pbaryngeus
Thyroid body
Thyro-pharyngeus
Subscapulo-hyoideus
Thyro-hyoideus
Pliaryngeal art.
Submaxillary artJ
Submental art.
CAVITY OF THE MOUTH, PHARYNX, Etc.
Brawn JtPrYtued l>y"W kA K.John«wn, Edmonrgh fc London
-ocr page 83-
32
THE ANATOMY OF THE HORSE.
horse they are of small but very variable size. Frequently they contain
but little muscular tissue, but now and again a subject is met iu which
they are very distinct. They are two in number, one being placed on
each side of the deep flexor tendon, above the fetlock. The fibres of
the small muscular belly arise from the side of the deep flexor, and
terminate in a small tendon which is lost in the tissue beneath the
horny spur of the fetlock.
The Interossei Muscles (Plate 9). These are the representatives
of the muscles which, in the human hand, fill up the interspaces of the
metacarpal bones, and give lateral movement to the fingers. In the
horse they are two in number, and are extremely rudimentary. Each
is to be sought to the inner side of the small metacarpal bone of its
own side, between that bone and the edge of the suspensory ligament.
Each has at its upper end a small muscular belly taking origin from
the neighbourhood of the head of the small metacarpal bone. It is
succeeded by a long, slender, nerve-like tendon, which at the fetlock
blends with the band sent from the suspensory ligament to the extensor
pedis tendon, or with the connective-tissue on the side of the joint.
The interossei and lumbricales muscles are of great interest to the
comparative anatomist, but, from their small si/e, they can have no
appreciable effect on the movements of the digit.
The Tendon of the Extensor Suffraginis (Plate 7) is to be followed
from the point below the carpus to which it has already been dissected.
The flat tendon, after crossing the carpus, descends to the outer side
of the anterior surface of the large metacarpal bone. As it passes over
the fetlock-joint, it becomes somewhat broader, and its play over the
anterior ligament of the joint is facilitated by means of a small synovial
bursa. Immediately below the joint it is inserted into the fore part of
the upper end of the first phalanx. In the region of the metacarpus
the tendon receives on each side a reinforcing band. The outer band
comes from the external side of the carpus; the inner is detached from
the extensor pedis tendon.
Action.—The museie is primarily an extensor of the digit on the meta-
carpus. When contraction is carried beyond this, it extends the meta-
carpus on the fore-arm.
The Tendon of the Extensor Pedis (Plate 7). This tendon, after
throwing off the slip to the extensor suffraginis, descends over the front
of the metacarpus and digit, and lies on the middle line. Its play over
the anterior ligament of the fetlock is facilitated by a small synovial
bursa; while, over the front of the interphalangeal joints, the synovial
membrane is directly supported by the deep face of the tendon, there being
no anterior ligament for these joints. At the middle of the first phalanx
the tendon is joined on each side by a strong band which descends
obliquely over the side of the fetlock from the suspensory ligament-
-ocr page 84-
PLATE XXXII
Ant. auric.art.
Upper end of great conn
Oceipito-styloi<
Occipital art.
Guttural pouch
Transv. facial art.
Post, auric.art.
Int. maxill. art.
Inf. dental art.
Eustachian tube
Levator palati
TenBor palati
Hyo-pharyngeus
Stylo-pharyngeus
Pterygo-pharyngeus
Palato-pharyngeus
Cerato-hyoid
Great hyo-glossus, turned upwards
Sup. laryngeal nerve
Int. carotid art.
10th nerve„
11th nerve
Cervical cord of)
sympathetic nerve •
Palatoglossus
Stylo-gloss\is
Genio-glossug
Genio-hyoidens
Mylo-hyoideus
Mid. hyo-glossus
Inter- cornual joint
Glossal process
Lingual art.
ubmental art.
ubmaxillary art.
Common carotid art.
Ext. carotid art.
Thyroid body
12th nerve
Crico-pharyngeuK
Thyro-pharyngevis
ThTto-hyoideOn
llra-Km It Printed Vy W. tA K Johmton IdinVuT^h fc Louden
TONGUE, PHARYNX, Etc.
-ocr page 85-
DISSECTION OF THE ANTERIOR LIMB.
33
Tl
pedis end°n ^ finally inserted int0 the pyramidal process of the os
Action,.-
Phalanx
-The first action of the muscle is to extend the third
*« second on the first.
d, and then
+ . — —1 the first. When con-
^ a°tion is continued, it produces
uccessively extension of the fet-
lock
and of the carpus.
, ~*reetions.~The tendons on the
ack of the metacarpus and digit
^ Ust next be dissected; and as
arid1*61"11"™17 Step' the oarPal<___
for metaoarP°-phalangeal sheaths
»ied in connection with these
ei«Ions should be examined.
tul 1 °ARPAL Sheath (Fig. l)is the
fle nlar passage through which the
xors of the digit are transmitted
Und the carpus. It is formed
trout by the back of the carpus
covered I 4.1
j.            uy the posterior common
jjf^ent of that joint. Behind it r,
th nded in its outer third by
t\ve P*Slform b°ne, and in its innerR ''"
reD°" h by a stroug fibrous baud S'6
1 resenting the anterior annular
b™^ °f the human wrist This
<* stretches like an arch from
°f «* carpus
ne to the inner side
It is continuous
back Wlth tne deeP fescia on the
may f  the fore-arm, of. which it
DrlJ-          considered a thickened
1 ortion •          lii
thii '    an "elow it becomes
lllei',   and is continued
as the
'asCla
011 the back
car
------ of the meta-
„' 1Us (palmar fascia of man).
Fig. 1
Uo «*pal sheath is
provided with
•1)l
:SSECTION OP
the Metacarpus and Digit, showing the Tendons and their Synovial
Sheaths (Chauveau)
' Syno
S?,?V,ial m«mbranf nf°«the e*t™s°r metacarpi magnus; 2. Superior eul-de-sew, or pouch, of the
Cff^ovia membf        ^rpal sheath ; 2', 2'. Inferior part of the same ; 3. Pouch of the radio-
"ynoviaf"nV'"'?-°arl»l ligament;
jovial mem jbrane of the letl°
sy the reir.ov.,ir'l?!,of tlle metacarpo-phalangeal sheath ; !
p.!bc'»Tal Hai°t the reinforcing sheath of the perforans t........_____„___„„ ,™_,. 0
"• *le-xor perforaaV- F PV S,™301' Vfis ' S' S' SuPerior sesamoidean (suspensory) ligament; F.
-ocr page 86-
PLATE XXXM
Great longitudinal fissure between
hemispheres of cerebrum
Olfactory bulb
-v.            Olfactory Peduncle
Int. olf. tract
Optic (2nd) nerve
Optic chiasm*
Pituitary bod;'
Ext. olf. t"1'1
lnfundibulum
Tuber cinereum.
jrd nerve
4th nerve
J2 int. root \
■j&rt. root>
Mof5threrV«
6th nerve
7th nerve
Cms cerebri
Great oblique
fissure ^B^
Pons Varolii
Trapezium
lateral lobe
of cerebellum
12th nerve
Medulla oblongata
I in natation of pyramids
Inf. pyramid
&PriT.^a V? V LJk X Jol B««                           :.Llondon
BRAIN—Inferior Aspect
-ocr page 87-
34
THE ANATOMY OF THE HORSE.
a synovial membrane, which lines it, and is reflected over the flexor
tendons to facilitate their gliding. If the fibrous band just described be
cut, and a probe be passed upwards and downwards within the sheath,
an idea of the extent of the synovial sac will be gained. It will be
found to extend upwards for two or three inches above the carpus,
and downwards as far as the middle of the metacarpus.
Directions.—The fibrous band should be entirely removed in order to
permit the examination of the tendons, and of the nerves and bloodvessels
which accompany these within the sheath.
The Metacarpo-phalangeal or Great Sesamoid Sheath (Fig. 1). This
is a second synovial apparatus developed in connection with the flexor
tendons. If a vertical incision be made through the superficial flexor just
above the fetlock, and a probe passed into the incision, it will enter the
synovial cavity, and may be pushed upwards for two or three inches
above the fetlock, and downwards as far as the middle of the second
phalanx. The synovial membrane lubricates the pulley-like surface
formed by the sesamoid bones and the inter-sesamoid ligament, and is
reflected on to the tendons. It is supported laterally by a fibrous
expansion which, adhering to the superficial flexor behind, is inserted
in front by three slips on each side, the highest insertion being into the
sesamoid, and the other two into the first phalanx. At its lower extremity
this synovial membrane meets that of the navicular sheath, and in front
of the same point it is separated from the synovial capsule of the coffin-
joint by a kind of partition of yellow fibrous tissue connecting the front
of the perforans tendon to the back of the os corona) (Plate 10, fig. 2).
The Superficial Flexor tendon (Plates 5, 9, 10, and 11). The
tendon succeeds the fleshy portion of the muscle at the lower part of the
fore-arm, and it is there reinforced by a fibrous band which springs from
the back of the radius and is sometimes termed the superior carpal ligament,
in contradistinction to the band which reinforces the tendon of the deep
flexor below the carpus. The tendon passes through the carpal sheath
in company with and behind the deep flexor, and then descends behind
the metacarpus. Having arrived at the fetlock, there is formed in it
a remarkable ring, through which the tendon of the deep flexor plays.
It is in consequence of this arrangement that the superficial muscle is
termed perforates, and the deep one perforans. As already seen, the
tendons are here enveloped by the synovial membrane of the meta-
carpo-phalangeal sheath. At its extremity the tendon is bifid, and
each slip is inserted into the upper extremity of the second phalanx on
its lateral aspect.
Action.—The muscle flexes successively the pastern, fetlock, and
carpal joints.
The Deep Flexor tendon (Plates 5, 9, 10, and 11) is, through-
out its course, closely related to the preceding, in front of which it lies.
-ocr page 88-
PLATE XXXJV
(Jreat longitudinal fissure between
hemispheres of cerebrum
Crucial fissure.
Crucial fissure
•total fi*"
Lateral lobe of
I cerebellum
Middle lobe of
I cerebellum
Medulla oblongata
v Printed oy ^ 1A K Jolmium Edinburgh fc London
Bit AIN—Superior Aspect
-ocr page 89-
DISSECTION OP THE ANTERIOR LIMB.                                    35
* C1 escellding through the carpal sheath, it is joined by a very strong
Us band—the inferior carpal ligament, which is the down ward continua- j
, °* the posterior common ligament of the carpus. This fuses with I
tendon about the middle of the metacarpus, and it is of consider-j
t< lmportance, being frequently involved in what is commonly termed
Plain of the back tendons." In that condition it may be very distinctly
r,, y Manipulating in front of the flexor tendons, just below the carpus,
tendon, as thus reinforced, descends between the suspensory liga-
,. m front, and the perforates tendon behind; and at the fetlock it
b es over the sesamoid palley, and passes through the ring of the
1 einoial flexor. It then passes between the terminal branches of the
-mentioned muscle, glides over the smooth surface on the back of
second phalanx, plays over the navicular bone, and finally becomes
• "> ted into the semilunar crest of the os pedis. The terminal portion
ne muscle, as well as the navicular sheath developed in connection
!t, will be examined with the parts contained within the hoof.
etion.—The muscle flexes successively the interphalangeal joints, the
IetI°ck, and the carpus.
THE FOOT.
Di
the
Sections.—By the term foot, as here applied, is meant the hoof and
parts contained within it. If it is intended to study this in a limb
wnole of which is to be successively dissected, the student must
ed in the following manner. When the dissection of the fore-arm
°een completed, and before the removal of the skin from the nieta-
I us and digit, the hoof must be forcibly removed by the aid of a
^ng-smith's hammer, toe-knife, and pincers. To facilitate this, the
may be heated in a fire, the skin of the digit being swathed in a
th i *° Prevent charring. This is the speediest method of removing
°oi, but it has the double disadvantage of destroying in great
tl + u ^e ^00^ i*self> ar,d also tne injection of the vessels, provided
, as been executed. The following is a preferable method of pro-
,• ■ -^Procure a foot severed a few inches above the fetlock, and
inject tb
j . , ne arteries and veins from the metacarpal vessels. When the
.         °n has solidified, roll the foot in a piece of wet cloth, and bury it
rermenting heap of stable manure. Decomposition will speedily
> and after a week the preparation should be examined at intervals
for 'i °r ee days, the metacarpal bone being fixed in a vice while
eg. e attempts are made to pull off the hoof. When this has been
sat ' ne foot and removed hoof should be immersed for a day in a
s. • .         solution of carbolic acid in water, to which a little methylated
v . may be added. This will speedily remove all odour of decom-
Th °n' and dissection maytnen be proceeded with.
bar. !,           (Plate 10. ngs- 4 and 6). This is made up of the wall, the
m> Resole, and the frog.
-ocr page 90-
PLATE XXXV
Olfactory bulb
Septum lucidum
Corpus callosum
ly of fornix
orpus striatum
Choroid plexus
Taenia hippocampi
ippocampus
Nates
Testes
Ant. ped. of cerebellum
Mid. ped. of cerebellum
Post. ped. of cerebellum
8th nerve
4th ventricle
Medulla oblongata
Cerebellum
IfcPnntM W W. JcA K Johnston Edinburgh IcLondon
BRAIN—LATERAL AND 4TH VENTRICLES, Etc.
-ocr page 91-
THE ANATOMY OF THE HORSE.
3G
The Wall is that part of the hoof which is exposed when the foot
rests in its natural position on a flat surface. It is divided, though
not by any well-defined boundaries, into toe, quarters, and heels. The toe
includes an area on each side of the middle line of the wall in front;
and it passes on each side into the quarter, which comprises the lateral
region of the wall. Posteriorly the wall changes its direction, and
disappears from view, forming an angular part, which is termed the heel.
In reality, the wall does not stop at the heel, and it is this concealed
continuation that is termed the bar. In a well-formed hoof the wall in
the region of the toe slopes at an angle of about 50°.
The External Surface of the wall is, in a state of nature, covered by a
kind of epithelial varnish termed the periople, which is thickest at the
top of the wall, just under the hair. This, which is a natural varnish
provided to check evaporation and consequent cracking of the subjacent
horn, is generally rasped away by the shoeing-smith. The internal sur-
face of the wall is traversed in a vertical direction by the series of horny
lamince. These number about five or six hundred; and before, separa-
tion of the hoof they were interleaved with the sensitive lamina; to be
presently described. The superior border of the wall shows a kind of
gutter, termed the cutigeral groove, which is the mould left by the
coronary cushion. The floor of this groove has a closely punctated
appearance, each minute perforation being the upper end of one of the
horn tubes of the wall, and lodging, in the natural state, one of the
papilla: of the coronary cushion. The inferior border embraces the
sole, and in the unshod animal comes into contact with the ground.
The wall is thicker at the toe than at the quarters or heels; and in
each of these areas, it is thicker on the outside than in the correspond-
ing area on the inside.
The Bars. These are the reflected terminations of the wall behind the
heels; and if the foot be turned up, the continuity will be distinctly seen-
The Outer Surface of the bar, which is here seen, slopes towards the
frog, and bounds outwardly the lateral lacuna of that body. It shows
an inferior border, which runs towards the centre of the sole, but stops
a little behind the point of the frog. The bars are also seen in the
interior of the hoof, where ^hey show an internal surface bearing horn}'
lamina: like those of the wall. The superior border of the bars is
included between the frog and the sole, and blended with them.
The Sole presents an inferior face, which is vaulted, and this inde-
pendently of any paring to which the foot may have been subjected, as
the horn of which it is composed exfoliates so as to give it this con-
figuration naturally. The superior face is somewhat convex, and has
a&punctated appearance similar to that already seen in the cutigeral
<>Toove. The minute holes lodge the papilla of the so-called sensitive
sole which is the horn secreting structure of this region. Anteriorly
-ocr page 92-
PLATE XXXVI
Corpus striatum
"edunole of pineal body,
Body of fornix
Ant. pillar of fornix
Ant. )
Mid. V commissure
Post, j
P ineal body
Nates
Testis
£nV 1 peduncles of the
_&£) cerebeUum
8th nerv.
Floor of 4th ventricle
—Medulla oblongata
-. A K Johnston. Edbibur^h feLondoj
BRAIN—GANGLIA OF THE BASE
-ocr page 93-
DISSECTION OF THE ANTERIOR LIMB.                                    37
e sole presents a convex border, which unites it intimately to the
., r b°rder of the wall, a line of whitish horn marking the junction of
e two structures. Posteriorly it has a deep V shaped indentation,
0 the central point of which the frog penetrates, while behind that on
each side it is related to the bar.
_ «e sole of the hind hoof is distinguished from that of the fore by
Ulg more vaulted, and by being more pointed (less circular) at the toe,
s latter difference affecting also the form of the wall in the same
»ion. The outer edge of the sole is more convex than the inner,
rlcn enables one to readily distinguish between a right and a left hoof.
bs Frog. This is a distinctly elastic mass of horn which, in a state
mature, projects sufficiently to come into contact with the ground,
thus give the animal a secure foothold. Its inferior surface shows
■ eriorly a shallow cleft, or depression, termed the median lacuna,
lateral lacuna? lie at the sides of the frog, the outer boundary of
lacuna being formed by the bar. The superior surface shows,
ically over the median lacuna, a projection termed the frog-stay.
ach side of the frog-stay this surface is depressed, and the whole is
ued on the plantar cushion. This surface is punctated, and the
TV,         °^ *ne Pumtar cushion are received into the minute apertures
Posterior extremity, or base, of the frog consists of two rounded emi-
1         " the bulbs, or glomes—separated from each other by the median
a- The anterior extremity, or point, is wedged into the centre of the
tV,               lateral borders bring the frog into relation with the bars and
„~ ° e> and there is an intimate union with each of these at the point
ot contact.
"& nute Structure of the hoof. The entire hoof is an a»»regation of
e ., a epithelial cells, which here represent the horny layer of the
ex 1I111S" When a thin section across the wall, sole, or frog is
of +m *fte uom substance is seen to be arranged in the form
Co *. • ' cemented together by an mtertubular substance, and
aii ' & within their lumen a quantity of intratubular material.
ui Tc          —tubular, intertubular, and intratubular—are composed of
of h epithelial cells, differing in the three situations in the direction
c . eells, their state of aggregation, or the presence or absence of
par u1Iled P^ent- The tubes of the .vail are straight, and extend
toon *' to the surface, from the coronarv to the inferior edge of the
" ai] Tii                          '                                   "                                    °
ft' ine tubes of the sole have the same disposition, but those of the
ailb1aie lightly flexuous. The upper end of each tube is occupied by
the n*=ate<* vascular papilla, which belongs, in the case of the wall, to
the • 011ai'v cushion ; in the periople, to the perioplic ring; and in
Kl. . e ana- frog, to the sensitive structures of the same names. In the
(wli' 8          tae 1joucl °f connection between these papillated surfaces
iepresent the eorium of the skin) and the corresponding part of
-ocr page 94-
PLATE XXXVII
;.\
Testicle
hf--------Septum scroti
Tunica vag. reflexa
Cremasteric fascia-
/ Dartos
Infundibuliform fascia
Spermatic fascia
Corpus cavernusum
Semimembranosus
\
Erector penis
Int. pudic art.
Sphincter ani ext.
\
\
V
I>ra.HTi ^Printed "by"W. StAl Johnston. Edinburgh fcLondon
MALE PERINEUM
-ocr page 95-
38                                   THE ANATOMY OF THE HORSE.
the hoof, is a stratum of soft protoplasmic epithelial cells by whose
growth and multiplication the hoof-horn is formed. This stratum of
cells represents the deepest cells of the rete mucosum in the skin, and
it is by its ready decomposition that the bond of connection between
the sensitive and insensitive structures is destroyed, permitting the
extremity of the digit to be extracted from its horny investment.
Directions.—The student should next turn his attention to the ex-
tremity of the digit as exposed by the removal of the hoof, and he will
find it to present a configuration not unlike the exterior of the hoof itself
(Plate 10, figs. 1 and 5). And in the first place, let him examine that
part which he will easily recognise as having been separated from the
inner surface of the wall. This is traversed by a series of leaves which,
in contradistinction to those already seen on the inner surface of the
wall, are termed the sensitive lamina?, and sometimes the podophyllous
tissue.
The Sensitive Laminae. Each lamina is fixed by one of its borders to
the periosteum of the os pedis, and extends in a vertical direction from
near the coronary cushion to the sharp edge of the bone, where it
terminates in five or six long papilla). In the natural state the sensitive
and the horny laminae are interleaved, and the former hero represent
the corium, or true skin. The lamina), it will be noticed, become pro-
gressively shorter as they are traced backwards ; and at the end of the
series on each side, and adjacent to the plantar cushion, there is a number
of small leaves that were interleaved with the horny lamina) of the bars.
The Coronary Cushion. This is a projecting, cornice-like structure,
placed above the laminse and below the limits of the skin of the digit.
It fits into the cutigeral groove at the upper border of the wall, and its
surface is closely set with long papilla) which were received into the
apertures found in that groove. These papilla) give the coronary
cushion a velvety pile, which may be rendered very evident by immers-
ing the foot in water. If the coronary cushion be traced backwards, it
will be seen to pass into the plantar cushion. Above the cushion is a
narrow groove separating it from the periopolic ring. Below the cushion
there is a narrow smooth space which runs between the cushion and the
sensitive lamina). The coronary cushion is a modified portion of the
corium, and through the agency of the cells which cover the surface of
its papilla), the wall of the hoof is formed.
The Perioplic King. This ring is composed of papilla) like those of
the coronary cushion, but smaller in size ; and it is by its agency that
the perioplc which covers the exterior of the wall is formed.
The Plantar Cushion. This is a fibro-elastic pad interposed between
the horny frog and the terminal part of the perforans tendon. It
possesses two faces, two borders, a base, and an apex. The lower face
looks backwards as well as downwards when the foot rests on a flat
-ocr page 96-
PLATE XXXVIII
Panniculus oarnosus
Abdominal tunic
.Subcutaneous thoracic (spur) vein
%
5
/
V
Subcutaneous abdominal art
Superficial inguinal glands
y
T'ti. n fc PnnLed by "W fc.A K.JoTra*t'R. Ertuiburgl. I
AKDCMTNA1., WALL.
-ocr page 97-
V
PLATE X.
'ig. I.—The Digit with the Hoof removed, flexed and viewed from behind.
F m, ns*tive sole ; B. Sensitive laminae that were interleaved with the horny laminfe of the bar ;
S;ln # Pyramidal body, or sensitive frog ; L. Lateral lacuna of the same ; M. Median lacuna of the
foi-if ' Fibrous sheath uniting the two branches of the perforatus ; R. Branches of the per-
pei'f l"1)assino to be inserted into the os coronae ; T. Tendon of the perforatus ; T. Tendon of the
Plant'nS ln *tS Pass:iSe between the branches of the perforatus ; V. Reinforcing sheath of the
** aponeurosis ; X. Attachment of the same to the side of the os suffraginis.
Fig. II.—Vertical mesial Section of the Digit.
F. p, ,, S Pedis; B. Coronary cushion; C. Coffin-joint; D. Navicular bone; B. Os coronse;
Boron          J0^ ; H. Branch of the perforatus at its insertion into the lateral aspect of the os
Perfn ■■■ ' Insei'tion of the plantar aponeurosis into the semilunar crest; K. Os suffraginis ; L. The
Perf . US *,ent^on » M. Ligament of yellow fibrous tissue which unites the anterior face of the
ses;i ' s to the posterior face of the os coronae, and separates the inferior cul-de-sac of the great
syUov' \ B"eafck from that of the synovial membrane of the coffin-joint; N. Protrusion of the
0, a, .' membrane of the corono-pedal joint between the navicular bone and the os pedis;
gteft* ■ aesamoid sheath ; P. Synovial membrane of the coffin-joint in contact superiorly with the
°f the' arriol(l sheath, from which it is separated by the yellow transverse ligament M. ; T. Tendon
Perforans ; y. Fetlock-joint.
Fig. III.—Arteries of the Digit.
(rameo ^1*a^ artery; C. Perpendicular artery at its Origin; H. One of the posterior branches
°f tli i ",e^onn^s)i for the perforans tendon ; J. Another of the same ; K. Origin of the artery
^ariie ■ ' ar cushion ; M. Origin of anterior branch of coronary circle ; M.' Posterior branch of the
Pedis f ' Origin of preplantar artery ; S. Plantar artery in the plantar groove and in the os
the H*. .I1Ulne with the opposite artery the semilunar anastomosis ; V. V. Descending branches from
^ttitnnar anastomosis.
Fig. IV.—The Hoof—plantar aspect.
B. ,\ " ^S*0* of the toe ; S. Sole ; L- Frog; A. Line indicating the junction of wall and sole ;
of t*j *™ of inflexion of the wall, showing the continuity of the wall and the bar ; E. Inferior edge
g■"* bar ;F. Lateral 1 acuna of the frog; G. Bulbs of the frog ; Q. Median lacuna of the frog;
egwns of the quarters ; O. Eegions of the heels.
£■ V.—Extremity of the Digit with the Hoof removed—viewed from the side.
• Plantar cushion with its villosities ; D. Groove between the plantar cushion and the
Per
Podo i, n* ' ^' Per'°luic iin? < P- Inferior border of the plantar cushion ; G. Sensitive lamina,
P yllous tissue ; H. Villosities which terminate the laminae.
or
**B- VI—Anteroposterior mesial Section of the Hoof—showing its interior.
l'«rio d""08 °' llorny laminse ; O. Section of the wall; P. Section of the sole ; S. Upper edge of the
1' e above the eutigeral groove ; T. Section of the frog ; X. Cutigeral groove.
-ocr page 98-
PLATE XXXIX
External oblique muscle
-^^                      Serratus magiras
Poupart's ligament
Spermatic cord
Ext. abdominal ring
\ J
(4 Lr*~ a
Aiffbcutaneous abdominal art.
^MSlx. pudic art.
^f^M>t. dorsal art. of penis
Umbilicus
Drwn kPnntei by W &A.K JoTm^ton. Edinburgh fc T.unJoi
ABDOMINAL WALL
-ocr page 99-
40
DISSECTION OF THE ANTERIOR LIMB.
surface; and it is moulded on the upper face of the homy frog, to which
it has a close resemblance in form. The central portion of the cushion
is therefore sometimes termed the sensitive frog, and it is also known as
the pyramidal body. It shows in front a single ridge, which posteriori)7
becomes divided into two by a deep median cleft for the reception of
the frog-stay. This surface has a villous aspect, the papilla? being
imbedded in the foramina seen on the upper surface of the horny frog.
The horny frog is formed by the agency of the cells covering these
papilla;. The upper face looks forwards as well as upwards, and is
applied to the reinforcing sheath of the deep flexor tendon. The
borders, which are right and left, bring the plantar cushion into relation
with the inner surface of the lateral cartilages. The apex lies in front
of the semilunar crest of the os pedis, with whose periosteum the tissue
of the cushion is intimately blended. The base of the cushion consists
of two thick rounded masses termed the bulbs of the plantar cushion.
These are continuous in front with the ridges of the pyramidal body,
and they present the same velvety aspect; while, on each side, the
villous tissue joins the extremities of the coronary cushion.
The Sensitive Sole. The student should next examine that part of
the foot which, before separation of the hoof, came into contact with
the upper surface of the horny sole, and which for that reason is termed
the sensitive sole. It is of a roughly crescentic form, being penetrated
by the pyramidal body behind; and it is co-extensive with the plantar
surface of the os pedis. Its connective-tissue basis is firmly adherent to
the periosteum of the bone, while its free surface bears long papilla)
which penetrate the horn tubes of the sole. The horny sole is formed
by the agency of the cells which clothe the papillae of the sensitive sole.
Directions.—On manipulating the bulbs of the plantar cushion, the
student will feel the .lateral cartilages of the foot; and one of these is
to be exposed and defined by removing one half of the plantar cushion.
The Lateral Cartilages. These are in the main composed of
hyaline cartilage, though often erroneously termed the fibro-cartilar/es of
the foot. As is common with fibro-cartilage in many other regions, it
shows a transitional structure at its periphery, where its matrix becomes
more or less fibrous. Each plate of cartilage possesses two faces, and
four borders separated by four angles. The external face is convex and
covered by a plexus of veins, some of which penetrate the plate and
connect the plexus with another lying beneath it. The internal face is
concave. Behind it is united to the plantar cushion, while anteriorly
it protects the corono-pedal articulation; and a cul-de-sac of the synovial
membrane of the joint lies in direct contact with the cartilage, a fact
which it is important to remember in connection with operations for
"quittor." The superior border is thin and flexible, and may be felt in
the living animal. The digital vessels cross this border in passing into
-ocr page 100-
PLATE XL
Poupart's ligament
Spermatic cord
Ext. pudic artery
Post, abdominal artery (under tendon)
Obliquus abdominis int.
An intercostal nerve
Transversalis abdominis
°riTK*d bj w tA K luhn.wn Y.<\.'
ABDOMINAL WALL
►
----------------
-ocr page 101-
THE ANATOMY OP THE HORSE.                                   41
oot. The inferior border is supported by the wing of the os pedis in
ll, while posteriorly it blends with the plantar cushion. The anterior
(er slopes downwards and backwards, and is blended with the antero-
■*i ligament of the corono-pedal joint. The posterior border is parallel
anterior, and is covered by the plantar cushion. The four borders
a^ *°ur anglesi of which the postero-superior one and the one diago-
y opposite are obtuse, while the other two are acute.
i^        disease termed "Side-bones," the lateral cartilages lose their
_, Vj in consequence of their conversion into bone.
. -fhe Bloodvessels of the Foot (Plate 10, fig. 3). These should be studied
n injected limb from which the hoof has been removed by the method
decomposition described at page S5. The arteries of the foot are
lved from the digital artery, which has already been dissected in its
' cent towards the foot, where, within the wing of the os pedis, it
^ cles into the plantar and preplantar arteries. Some of the collateral
c ches of the digital artery have already been described at page 29; but
e remain for examination the artery of the plantar cushion and the
rnT**y circle, as well as the plantar and preplantar terminal branches.
e Artery of the Plantar Cushion arises from the digital, just as
' "Vessel passes within the upper border of the lateral cartilage, and
• ses obliquely downwards and backwards to its destination. Besides
if 1 Jing the plantar cushion, it gives off a branch which turns forwards
Ucur in the formation of the circumflex artery of the coronary
ri-n
_» e Coronary Circle. Where each digital artery lies under cover
WV' i! eral cartilage, it gives off an anterior and a posterior branch
s          mosculate on the middle line before and behind with the corre-
T] ■ m^ branches of the opposite side, and thus form an arterial circle.
, circle closely embraces the os corona;; and among the largest
ai 'l j furnished by it, are two which emanate from its anterior half,
in ,,esccu^> 011e at each border of the extensor tendon, to aid in form-
rp, e cu'cumflex artery of the coronary cushion,
a si G CDMFLEx Artery of the Coronary Cushion (Chauveau). This is
Avi . er vascular arch placed immediately above the coronary cushion, to
Hie r ltS ^rancnes arc distributed. It is fed in front by the two above-
th- l °Ue vcssels from the coronary circle, and behind, on each side, by
ore-mentioned branch from the artery of the plantar cushion.
0f ,, replantar Artery is the smaller of the twTo terminal branches
°s n i. ^ital- I* passes forwards through the notch in the wing of the
that 18' aUC*tllen a^ouo tne preplantar groove on the laminal surface of
ne, where its branches are expended in the sensitive laminee.
for          lANTab Artery passes along the plantar groove to enter the
Co * 1 ° tnc same name. Within the os pedis it inosculates with the
ponding vessel of the opposite side, forming the plantar arch, or
-ocr page 102-
PLATE XLI
Pelvic flexure
Colon (3rd part)
Colon (2nd part)
Direct colic art,
—Retrograde colic art.
iaphragmatic flexure
Suprasternal flexure
Colon (4th part)
Post, aorta
-1st art. to single colon
/Ant. div. of ant.
(mesenteric art.
j Arteries to small
intestine
Duodenum
Small intestines
Ilio-caecal ait.
Ileum
Art. of the arch
Bight division of ant.Aj
mesenteric art.
Cseeuni
Sup. csecal art.
A m
Great
mesentery
Pnnttd by"W. StA.K. John«wn. EdinVur^h fe Lon3o]
INTESTINES AND ANTERIOR MESENTERIC ARTERY (Chauveau)
-ocr page 103-
42
DISSECTION OF THE ANTERIOR LIMB.
semilunar anastomosis. From this intra-osseous arch a great numler of
branches proceed. An ascending {anterior laminal) set of these leave
the os pedis by the numerous small foramina which cribble its laminal
surface. A descending {inferior communicating) set escape from the
bone by the series of larger foramina which open on the sharp edge
separating its laminal and plantar surfaces. These inferior communi-
cating arteries anastomose right and left with each other, and thus form
the circumflex artery of the toe. From the concavity of this artery
branches pass backwards, and supply the tissue of the sole.
The Veins of the Foot.—Intra-osseous vessels. Within the os pedis
the arterial branches are accompanied by satellite veins. There is
thus a semilunar venous anastomosis, to which small veins converge
from the laminal surface of the bone. The blood from this sinus is
drained away by a larger vessel which passes out by the plantar fora-
men in company with the plantar artery, and joins the posterior part of
the coronary plexus. Extra-osseous vessels. The foot is richly provided
with a superficial system of vessels, which are arranged in the form of a
close-meshed network having little or no communication with the deep
set. This venous envelope of the foot is divided into a solar, a laminal
(podophyllous), and a coronary plexus. Where the solar and laminal
plexuses meet, a composite venous vessel runs in company with the
circumflex artery of the toe. These two plexuses communicate freely
with each other, and with the coronary plexus. This last consists of a
central part, which underlies the coronary cushion, and of two lateral
parts, which on each side ramify on both surfaces of the lateral cartilage.
By the convergence of branches belonging to this cartilaginous division
of the coronary plexus, the digital veins are formed; and these drain
away the blood from both the intra-osseous and extra-osseous systems
of vessels.
Directions.—The terminal portion of the deep flexor tendon, and the
synovial apparatus developed in connection with it, should now be
examined.
The Deep Flexor tendon (Plates 10 and 11), when it reaches the
upper border of the navicular bone, widens out to form what is called the
plantar aponeurosis. This plantar aponeurosis plays over the navicular
bone by means of the navicular sheath, and is covered posteriorly by a
fibrous layer which ultimately blends with it. It becomes inserted into
the semilunar crest of the os pedis, and into the bone behind that crest.
The above-mentioned fibrous layer was first described by Bouley, and
designated by him the reinforcing sheath of the perforans. This expansion
is attached on each side by a slip to the lower half of the first phalanx,
and it serves to maintain the plantar aponeurosis against the navicular
bone.
The Navicular or Small Sesamoid Sheath (Plate 10, fig. 2). This is »
-ocr page 104-
PLATE XLII
Double colon
etrograde colic art.
Direct colic art.
tight fasciculus of ant. mesenteric
Ant. fasciculus of ant. mesenteric
:ft fasciculus of ant. mesenteric
Ant. mesenteric art.
Renal art.
Small intestine
.Colic mesentery
Single colon
Post, mesenteric
artery
Ext. iliac art.
Int. iliac art.
Urinary bladder
P«l
vic flexure-
Printed byV 1.AK Johmtfln EdinVurgh ItLondoi
INTESTINES AND MESENTERIC ARTERIES (Chauveav)
-ocr page 105-
43
THE ANATOMY OP THE HORSE.
' jHovial apparatus developed in connection with the perforans tendon
ere it plays over the navicular bone. It lines the deep face of the
"Clou, and is reflected on to the navicular bone and interosseous liga-
ent. It aiso extends above the navicular bone, where it is in contact
' the synovial membrane of the coffin-joint and that of the metacarpo-
phalangeal sheath.
THE SHOULDER-,) OINT.
"-ais joint is formed between the glenoid fossa of the scapula and the
ot the humerus. It is enclosed by a single capsular ligament
internally by the synovial membrane. The absence of lateral or
ler retaining ligaments in connection with the joint, is compensated
by the numerous tendons which pass from one bone to the other in
, B re^ation to the capsular ligament. These muscles are as follows :—
supraspinatus, infraspinatus, teres minor, biceps, and small scapulo-
oieralig. The last passes over the joint behind, where some of its
es Seem to be inserted into the ligament. In front of the joint the
°n of the biceps is separated from the ligament by a pad of fat.
°\ements.—The joint belongs to the class of enarthrodial or ball-
-socket joints, and the amount of its mobility should be proved by
^UliPulation before the removal of the muscles. If the scapula be kept
> it will be found that the humerus can be carried backwards so as
Wnnish the angle formed by the meeting of the bones. This is a
enient of flexion. Or the humerus can be carried forward in the
Tl ■ p e as in the preceding movement, but increasing the angle.
is
lon either outwards or inwards. When, in the living animal, it
llned inwards, the limb is thrown towards the middle plane of the
y, and is gajd to be adducted. The opposite movement, by which
mb is carried outwards from the middle plane, is termed abduction.
tner movements are permitted in the joint, viz., rotation and
„ i , Auction. In rotation the humerus, without change of place as a
"hole +                                                       •
,        > turns round its own axis. In circumduction the shaft of the
,'Us moves so as to describe the surface of a cone.
a*v_i. 6Se different terms having been here defined at length, their
PPlica+i •
n„ i ' u m the case of the other joints of the body will be readily
Understood)
fr , shoulder-joint of the horse is thus possessed of considerable
the k         m°vement; but still, the range of its mobility, owing to
rrm ■' Sence °f a clavicle, and to the different disposition of the pectoral
> IS much more restricted than in the human arm.
rem %on*-—-The muscles which surround the joint must now be
Th. -i °are '3euiS taken not to cut the capsular ligament.
psular Ligament loosely surrounds the articular ends of the
-ocr page 106-
PLATE XLIII
ight sac of stomach
Left lobe of liver
Pleuro-cesophageal art.
nt. gastric art.
ost. gastric art.
eft sac of stomach
Splenic artery
Left gastro-omental artery
.Gastro-splenic omentum
Spleen
Pyloric art.
Middle lobe of liver
Eight gastro omental art
Right lobe of liver
Duodenal art.
Duodenum
Kidney
Portal vein
Suprarenal capsule
Hepatic art.
Renal artery
Post, vena cava
Urete:
Suprarenal capsule
Kidney
Renal artery
Ant. mesenteric art.
Post, aoi'ta
Circumflex iliac art.
Ext. iliac art.
Int. iliac art.
Prvnt/.d by"W JcAK Johnston Edinburgh & London
CCELIAC AXIS, Etc. (Chauveau)
-ocr page 107-
ii                                  DISSECTION OF THE ANTERIOR LIMB.
bones, and may be conceived as having the form of a double-mouthed
sack, one mouth being attached around the rim of the glenoid cavity,
and the other at the periphery of the head of the humerus. The wall
of this sack is comparatively thin, but in front it is strengthened by
accessory fibres that pass in a divergent manner from the coracoid pro-
cess to the outer and inner tuberosities. These correspond to the
coraco-humcral ligament of man.
Directions.—If, in the removal of the muscles, the ligament has been
preserved perfectly intact, it will be noticed that though a considerable
force be exerted to pull the articular surfaces from each other, they still
remain in contact. If, however, an incision be made in the ligament, the
air will be heard to rush into the joint, while the bones separate to the
extent of half an inch or more. In the shoulder then, as in other joints,
atmospheric pressure is to be included among the agents keeping the
articular surfaces in contact. The capsular ligament is to be slit up so
as to expose the smooth and glistening aspect of the synovial membrane,
and the articular surfaces of the bones covered by articular cartilage.
The Synovial Membrane lines the inner surface of the capsular
ligament. It secretes the synovia, or joint oil, some of which will be
seen escaping from the joint.
THE ELBOW-JOINT (PLATE 11, fig. 1).
This joint is formed by the lower extremity of the humerus and the
upper extremities of the bones of the fore-arm. It possesses two lateral
ligaments, and an anterior ligament which supports the synovial
membrane in front; but behind, there being no ligament, the synovial
sac is directly supported by muscles.
Movements.—This is a ginglymoid joint, the only movements being'
flexion and extension. Inflexion, while the humerus remains fixed, the
bones of the fore-arm are carried forwards until the movement is arrested
by the coronoid process passing into the fossa of the same name. In
this movement the bones of the fore-arm do not move in the plane in
which the humerus lies, but deyiate a little outwards. The opposite
movement is extension, in which the radius and ulna are carried back-
wards until they are arrested by the tension of the lateral ligaments,
and by the passage of the beak of the olecranon into the fossa of the
same name.
Directions.—The anterior and lateral ligaments are to be exposed
and defined by removing the muscles from the front of the joint, but on
the posterior aspect of the joint the muscles should not be removed at
present.
The External Lateral Ligament is a cord-like band which is fixed
superiorly to a depression on the outer side of the lower extremity of
the humerus, and to the ridge which forms the lower boundary of the
-ocr page 108-
PLATE XLIV
Ensiform cartilage
Diaphragm
Falciform lig. of liver
Middle lobe of liver
Left lobe of liver
Right lobe
of liver
Stomach
Ant. gastric art.
Post, gastric art.
.— Spleen
___Splenic vessels
_Suprarenal body
-Ant. mesent. art.
Renal vessels
Left kidney
Poet, aorta
—Ureter
Post, mesent. art.
Circunif. iliac art.
Int. iliac art.
Ext. iliac art.
Artery of cord
— Spermatic art.
—Cremaster m.
Int. abdom. ring
'as deferens
Bight kidney
Post, vena cav;
From last dorsal
Transv. abdom
Aortic plexus
From 1st lumbar nerve
Psoas magnus--------
From 2nd lumbar nerve
From 3rd lumbar nerve-
Int. oblique
Inguinal nerves
yv-v ^
To pelvic plexus
Lateral and inf. ligamon
of bladder
Prepubicart. Rectum
Bladder
Drawn &. Pni.ttd bv V tA K Johnston Edvnonrfh It La
ABDOMINAL VISCERA, Etc.
-ocr page 109-
THE ANATOMY OF THE HORSE.                                          45
isculo-sph-al groove ; while interiorly it passes to be inserted into the
■" ernal tuberosity at the upper end of the radius.
the Internal Lateral Ligament forms a longer but more slender
Cord than the preceding, and passes from a small eminence on the
er side of the lower extremity of the humerus to be inserted into the
art of the radius below the bicipital tuberosity. Some of the anterior
les join the tendon of the biceps or the anterior ligament, while some
ne posterior join the areiform fibres connecting the radius and ulna.
J-he Anterior Ligament is of a membranous form. Its upper border
nxeu to the humerus, its lower border to the radius, while its lateral
orders blend with the lateral ligaments.
Sections.—The anterior and lateral ligaments should now be cut
^nsversely about their middle in order to expose the interior of the joint.
J-he Synovial Membrane will be seen to line the inner face of the
. _J evior and lateral ligaments, but at the back part of the joint there
l0 ligament and the membrane is supported by the muscles. If the
8er be passed backwards and upwards, it will enter a process of the
°vial capsule which extends upwards into the olecranon fossa, where
PM of fat intervenes between it and the anconeus muscle. Just
,, Q(* the external lateral ligament the membrane lines the origin of
,, Hexor metacarpi externus. On the inner side of the joint, behind
Eternal lateral ligament, the membrane lines the tendons of origin
Of fVl                                       O               '                                                                                                  O
. ne middle and internal flexors of the metacarpus, and of the super-
and deep flexors of the digit. This disposition of the synovial
I' ttle will be rendered more evident by cutting the above-mentioned
ies a few inches below the joint, and then turning their tendons of
0n|a upwards.
Sections.—The humerus being now completely severed from the
8 and ulna, the mode of union of these latter bones should be
t-xaniined.
e ^adio-itlnar Articulation.—In the adult animal the bones of
of 1°le"arrn are fused together below the radio-ulnar arch, by ossification
e interosseous fibres which in the young animal are interposed
b + °en *^le kw° bones. Above the arch, however, the fibres interposed
en the bones do not ossify except in a very old animal, but persist
"■ 'interosseous ligament. The union of the two bones is further
amed by areiform fibres passing on each side from the one bone to
u         ei'> and blendiug with the lateral ligaments of the elbow. At the
otl ^ai'^ °^ *neu" opposed surfaces, the two bones respond to each
g . y two small synovial facets, which, however, have no special
ui membrane, but are lubricated by processes from the synovial
'aP^le of the elbow-joint.
gx ement&.—These are inappreciable, the limb of the horse being
m a condition of pronation.
-ocr page 110-
PLATE XLV
Ensiform cartilage
Asternal artery
Foramen dextrum
Phrenic sinus
iCEsophagus in
'foramen sinistrun
-Post, aorta in hiatus
Curiae axis
Left crus of diaphragm
Ant. mesenteric art.
—Renal ait.
Psoas parvus
- A lumbar art.
Spermatic art.
Quadratns lumborum.
- Post, mesenteric art.
An intertransverse muscle
N—Circumflex iliac art.
V——— Ext. iliac art.
Int. iliac art.
Last lumbar art.
—Ant. crural nerve
Iliacus
Psoas magnus
Prepubic art.
Femoral art.
-1—Deep femoral art.
Art. to quadriceps
Int. saphenous nerve
'«ght eras of diaphragm
From last dorsal nerve^J^
Retractor costae___
Post, vena cava -
From 1st lumbar nerve-
Frorn 2nd lumbar nerve
Piom parvus-----
Psoas magnus--------
From 'Srd lumbar nerve-
Inguinal nerve-----
Urinary bladder
BortoriuA-
'•'ddlu lig. of Bladder
«ep inguinal glands
Drawn kPrrnud by "W, kA KJoTin«Lon Edinburgh JcLondoi
SUBLUMBAR REGION AND DIAPHRAGM
-ocr page 111-
46                                  DISSECTION OF THE ANTERIOR LIMB.
THE KNEE, OR CARPUS (PLATE 11, fig'S. 2 and 3).
This is not a simple, but a composite, joint, and entering into its
formation there are the carpal bones, the lower extremity of the radius,
and the upper extremities of the bones of the metacarpus. The carpal
bones are arranged in two rows, or tiers, and the bones of each row are
firmly bound together and converted into a single piece by ligaments
passing between the adjacent bones. A transverse joint is then formed
between the upper and the lower tier. This may be called the inter-
carpal joint, and it is secured by special ligaments passing between the
two rows. Another transverse joint is formed between the lower row
and the heads of the metacarpal bones; and this, which has also got
special ligaments, is termed the carpo-metaearpal articulation. A third
transverse joint is formed between the lower end of the radius and the
upper row. This, which is the radio-carpal joint, is also provided with
special ligaments. Lastly, there are four ligaments which do not belong
specially to any of these articulations, but secure the stability of the
entire composite joint, and are therefore termed common.
Movements.—The movements which take place at the carpus are
flexion and extension, and each of the transverse joints above-mentioned
is a ginglymus. When these movements are executed, however, the
three joints do not participate in them in an equal degree. The largest
share of the movement occurs at the radio-carpal articulation, and the
smallest between the carpus and the metacarpus ; while, as regards the
amount of movement, the inter-carpal transverse joint occupies an inter-
mediate position. When the limb is flexed at the carpus, it will be
noticed that the metacarpus and digit deviate a little outwards from the
plane of the fore-arm. When the limb is fully extended the lateral
ligaments are tightly stretched, and resist any attempts to produce
abduction or adduction ; but these movements can be produced when the
limb is fully flexed, in which position the lateral ligaments are relaxed.
Lateral movement, however, is not executed at this joint in any appreci-
able degree in the living animal. The gliding movement permitted
between adjacent bones in each row is of importance, as tending to
distribute pressure, and obviate the bad effects which would have been
likely to result from concussion had each row7 been a single rigid mass.
Directions.—The tendons which pass in relation to the joint before
and behind should be removed, and the ligaments should be studied
in the order of the following description.
There are four ligaments common to the whole joint, viz., two lateral,
an anterior, and a posterior.
The External Lateral Ligament is a cord-like band composed of &
deep and a superficial set of fibres, which slightly cross each other. 1*
is fixed superiorly to the external tuberosity at the lower end of the
-ocr page 112-
Post, mesenteric! art.
Int. pudic art
Obturator artery
Urinary bladder
Ureter
Rectum
Iliaco-femoral art
Gluteal art.
Lateral sacral art.
PLATE XLVI
Yesiuula semi ualis
(Suspensory ligament of rectum
Retracoyr penis ,
3phini'te>,ani
^-Vesico-prostatic art.
Prostrate gland'
Cowper's glaoA
rt. cf "the corpus iavcrn.osurn
Post, aorta
Ext. iliac art.
I nibilicill art
Erector penii i jijii
j!
Suspensory lig. of the penis
Post, dorsal art. of penis
Ant. dorsal art. of penis
Epididymis
Testicle
Primed by W ,VA K Johnston Edjnb-urgh te London
MALE PELVIS (Chauveau)
-ocr page 113-
(i)
PLATE XL
Fig- I.—Ligaments of the Elbow, seen from behind (Leyh).
A. Ext i +
'liuir-w          Ul B8«mont; B. Int. lateral ligament; C. C. C. Areiform ligaments; D. Radio-
Fig. II.—Ligaments of the Carpus, front view (Ckauv&m).
llietacar i ■ ^gamen*s of upper row ; 2. An ant. ligament of lower row ; 3. 3. Ant. carpo-
Pal 1]gaments ; 4. Int. lateral ligament; 5. Ext. lateral ligament.
s- III.—Ligaments of the Carpus, viewed from the outer side (Chauveau).
llletacar" -          ligaments of upper row; 2. An ant. ligament of the lower row; 3. 3. Ant. carpo-
^Sfttttent laments; 4. An intercarpal ligament; 5. Ext. lateral ligament; 6. A radio-carpal
Fig. iv _T
• LIGAMENTS OF THE FETLOCK, PASTERN, AND COFFIN-JOINTS ; SIDE VIEW (Chauveail).
slil>s of « °lal fascic"luts of the ext. lateral ligament of the fetlock ; 2. 3. Sesamoid and phalangeal
Machine- *i ^ ^isciCIllus of the same ligament; 4. 5.6. Upper, middle, and lower fibrous slips
^* Anter° ^ ^ ou^ll horo -cartilage to the os suffraginis ; 7. Lateral ligament of the pastern-joint;
eia* ligament of the coffin-joint; 9. Posterolateral ligament of the same joint.
*%■ V.-
Back
of the Digit dissected to show the Tendons and Ligaments (Bouley).
A A
*atei'al Koj ateial ligament of the coffin-joint; B. Insertion of extensor pedis tendon ; D. Postero-
^° the Tvto           °^ *^e comn"Joint; E. Divergent fibres of the same ligament passing to be attached
Ug&lUeni f           6 0a Pe<^is an(l inner surface of the lateral cartilage ; F. Slip sent from suspensory
Pei'forHtus° ^XtpnS01 tendon » r- -Branch of bifurcation of th-j suspensory ligament; R. Bi'anch of
the reinfoi-' ■ ' er^orans emerging from between the branches of the perforatus ; Y. Attachment of
S'Sheath of the perforans tendon to the side of the os suifraginis.
**6- VI _j»
' -°ACK of the Digit dissected to show the Tendons and Ligaments (Bouley).
Cai'tilage 0f t, inferior sesamoidean ligament; B. Highest slip attaching the glenoidal fibro-
SeSamoidea 1* l)astei'n-joint to the first phalanax ; O. Branch of perforatus ; P. Middle inferior
s*18ath of f] . ^aillent y S. Insertion of plantar aponeurosis into semilunar crest; T. Reinforcing
* plantar aponeurosis ; X. Perforans tendon.
A ;                Fig- VII.-Back of the Fetlock-joint (Modified from Bouley).
C- Middle b ?loid ^gament; B. B. Lateral bands of the middle inferior sesamoidean ligament;
^anioiiip., ',. c ie same ligament, its upper attachment cut away to show D. the deep inferior
an hgarnent.
-ocr page 114-
PLATE XLVII
Post aorta
Renal artery
Supra-renal capsule
Right kidney
Left kidney
Umbilical art.
Testicle
----Cowper's gland
r-------Crus penis
Retractor puni.s
Prmtrd bjTT. LA.K Jalmau
GENITO-URINARY ORGANS OF MALE (Chadveav)
-ocr page 115-
48
THE ANATOMY OF THE HORSE.
radius; and passing over the outside of the carpus, it furnishes slips to
the cuneiform and unciform bones, and terminates on the head of the
external small metacarpal bone. The ligament is perforated by a thecal
canal in which the tendon of the extensor suffraginis plays.
The Internal Lateral Ligament is fixed superiorly to the internal
tuberosity of the radius, and inferiorly to the heads of the large ana
inner small metacarpal bones, furnishing slips, as it passes over the
carpus, to the scaphoid, magnum, and trapezoid bones.
The Anterior Common Ligament has a flattened, four-sided form. It
is fixed superiorly to the radius, and inferiorly to the large metacarpal
bone, while its lateral borders are united to the lateral ligaments. Its
deep face is partly adherent to the carpal bones or their anterior
ligaments, and partly it is lined by synovial membrane. The tendons
of the extensor pedis and the extensors of the metacarpus play over its
superficial face, where they are provided with synovial bursse. The
ligament is somewhat loose when the joint is extended, and is put ou
the stretch during flexion.
The Posterior Common Ligament is a much stronger ligament than
the preceding. It is fixed above to the radius, and below to the large
metacarpal bone. Its internal border mixes its fibres with the internal
lateral ligament, while its outer border is blended in the same way with
the most external of the intercarpal ligaments. Its anterior or deep
face is very intimately united to the carpal bones, and its posterior face
is smooth and lined by the synovial membrane of the carpal sheath.
The snhcarpal ligament, or fibrous band which reinforces the perforaus
tendon below the carpus, takes origin from the posterior common ligfc"
merit, or may be described as the downward continuation of that
ligament.
Directions.—The anterior and lateral ligaments just described are to
be carefully dissected away, and in removing the first of these, care is
to be taken of the anterior bands connecting the bones in each row.
Eadio-carpal Ligaments.—There are three of these. The strongest
of them is a thick cord that stretches obliquely downwards and inwards
behind the carpus, and connects the radius and scaphoid. It will be
seen, without removing the posterior common ligament, which covers it,
by strongly flexing the joint and looking into it from the front. The
second is a very slender ligament which is fixed to the radius beneath
the preceding, and passes downwards to be attached to the pisiform and
the interosseous ligament uniting the cuneiform and semilunar bones.
The third is situated at the outside of the carpus, where it connects
the radius and the upper border of the pisiform bone, and is partly
covered by the lateral ligament.
The Inter-carpal Ligaments are also three in number. Two of
them are situated behind the joint, under cover of the posterior common
-ocr page 116-
PLATE XLVIII
Int. iliac art.
Lateral sacral art.
From 6th lumbar
From 1st sacral
From 2nd sacral
From 3rd sacral
Ischiatic art.
Lateral coccygeal art.
From 4th sacral
Middle coccygeal art.
From 3rd lumbar
From 4th lumbar
Iliaco-mugcular nerve
From 5th lumbar-
Int. pudic art.
Ant. crural nerve
Obturator nerve
Ilio-lumbar art.
Gluteal art.
Great sciatic nerve
Obturator art.
Iliaco-femoral art.
pper post, gluteal nerve
Lower post, gluteal nerve
Pudic nerve
Hsemorrhoidal nerve
. ■ y W. &-.A H Johnston. Edinburgh fcLondon
LUMBOSACRAL PLEXUS
-ocr page 117-
DISSECTION OF THE ANTERIOR LIMB.                                   49
! »arnent, and will he seen without further dissection on flexing the
nt and looking into it from the front. One of these connects the
scaphoid to the magnum and trapezoid, the other joins the cuneiform
. Magnum. The third is a strong ligament situated at the outer
e °f the joint, where it is blended with the lateral ligament in front,
with the posterior common ligament behind. Its fibres are fixed
Periorly to the pisiform bone, and inforiorly to the unciform and head
ne external small metacarpal bone.
1 bp Carpo-metacarpal Ligaments are four in number—two anterior
two interosseous. One of the anterior ligaments is composed of
separate slips which connect the os magnum and large metacarpal
The other passes from the unciform to the head of the external
. U metacarpal bone, under cover of the lateral ligament. The two
rosseous pass, one on each side, from the point of articulation of the
»e and small metacarpal bones, to join the interosseous ligaments
°nnecting the bones of the lower row.
of /rec^0,w-—Attention may at this stage be given to the disposition
e synovial membranes of the carpus, which are three in number.
jovial Membranes.—1. The radio-carpal synovial membrane not
j facilitates the movements between the radius and the bones of the
• Y r°w, but also descends between the latter bones as far as their
rosseous ligaments. 2. The inter-carpal synovial membrane, in the
e way, belongs to the intercarpal transverse joint; but it is also
"ttated above, between the bones of the upper row as far as their
osseous ligaments, and descends in the same way below, between
o aclJacent bones of the lower row. It communicates with the next.
b
" + le carP°-met(icarpal synovial membrane facilitates the movements
b + 6eU ^le l°wer row and the heads of the metacarpal bones, ascends
,        e" the adjacent bones of the lower row as far as their interosseous
s» ents, and dips down to supply the articulations between the large
an^mall metacarpals.
eedons.—The radio-carpal, inter-carpal, and posterior common
is^l l6n*s should now be cut transversely. The upper row will thus be
nn, as a single piece for the examination of its special ligaments.
■ , e Ligaments of the Upper How are three anterior, and three
sseous j and they are extremely simple. The anterior ligaments
j , tteile(j bands connecting the adjacent bones in front, while the
''seous bands are very short and connect the contiguous surfaces
0f*e bones.
0          -Laments of the Lower Row are two anterior, and two inter-
e . / and they are disposed like those of the upper row. In
th 1U^ *hese, the lower tier of bones must not be separated from
si          acarpusj as that would involve the destruction, in part, of the
Pensory ligament of the fetlock.
-ocr page 118-
50
THE ANATOMY OF THE HORSE.
The Inter-metacarpal Articulations. The head of the large meta-
carpal bone responds to one of the small metacarpals on each side by a
small synovial joint lubricated by a process from the carpo-metacarpal
synovial membrane. Below that point the union of the bones is main-
tained by short interosseous fibres, which, in adult animals, arc very
frequently ossified. The lower extremities of the splint bones, however,
for a short distance above the little knob that terminates them, remain
freely movable, as may be felt by manipulation in the living animal.
In addition to the interosseous fibres, the ligaments of the carpus which
get inserted in common into the heads of both large and small metacarpal
bones, contribute to the union of these bones.
THE FETLOCK-JOINT (PLATE 11, FIGS. 4-7).
This, which is technically termed the metacarpophalangeal articula-
tion, is a ginglymoid joint; and its articular surfaces are furnished by
the lower extremity of the large metacarpal bone, the upper extremity
of the first phalanx, and the two sesamoid bones. It corresponds to the
joint at the knuckles in the human hand.
Movements.—Flexion and extension are, in the natural state, the only
movements executed at the joint; but by manipulation, slight lateral
movements may be produced when the joint is fully flexed. In com-
plete extension the digit is carried beyond the point at which it lies in a
straight line with the metacarpus (over-extension), until the movement is
arrested by tension of the suspensory ligament.
Directions.—The tendons which pass in relation to the joint before
and behind having been carefully removed, the ligaments should be
dissected and studied in the order of their description.
The Superior Sesamoidean or Suspensory Ligament.—The main por-
tion of this ligament is lodged in the channel formed by the three meta-
carpal bones, where it is related by its posterior face to the perforans
tendon and its reinforcing band (subcarpal ligament). It has a double
origin behind the carpus, viz., (1) by a superficial layer from the lower
row of carpal bones, and (2) by a deeper layer from the upper end of
the large metacarpal bone. (In the hind limb it has a similar origin froni
the .tarsus and metatarsus). These two portions blend, and descend be-
hind the metacarpus as a flattened band which bifurcates a few inches
above the sesamoid bones. Each branch passes to the sesamoid bone of
its own side, where a considerable proportion of its fibres become inserted;
while the rest is continued in the form of a band which crosses obliquely
downwards and forwards over the side of the fetlock to join the extensor
tendon on the front of the digit, and be continued with it to the os pedis-
The ligament is composed of white fibrous tissue with a constant admix-
ture of striped muscular tissue. The presence of muscular tissue here,
points to the conclusion (strengthened by other considerations) that the
-ocr page 119-
DISSECTION OF THE ANTERIOR LIMB.                                  51
Pensory ligament is a muscle which, in the evolution of the horse,
undergone retrogressive changes, and lost its original function.*
ne Inferior Sesamoidean Ligaments. These are three in number,
may be distinguished as superficial, middle, and deep. The super-
nt ligament is fixed below to the glenoidal fibro-cartilage developed
lnd the superior articular surface of the second phalanx. It ascends
c flattened band behind the os suffraginis, where it is placed between
middle ligament and the tendon of the deep flexor; and, widening a
e. it is inserted into the base of the sesamoids and the intersesamoid
&ament. By cutting the ligament about its middle, and reflecting it
P vards and downwards, the middle ligament will be brought into view.
e m^ddle ligament consists of a median and two lateral bands. Each
xed to the back of the os suffraginis, and ascends to be inserted into
base of the sesamoids. This should be cut and reflected like the
ceding ligament, in order to expose the next. The deep ligament
sists of a few short fibres disposed like the letter X, and fixed, on the
nand, to the upper part of the posterior surface of the os suffraginis,
' °n the other, into the base of the sesamoid bones. This ligament
i Ports the synovial membrane of the joint.
ne Lateral Ligaments of the fetlock-joint. Each comprises (1) a
P incial fasciculus connecting the lower extremity of the large
acarpal bone to the upper extremity of the first phalanx; and (2) a
P fasciculus attached, on the one hand, to the large metacarpal
atn the preceding, and, on the other, to the sesamoid and upper
extremity of the first phalanx.
Anterior Ligament has a membranous, four-sided form. It
ls the joint in front, and supports the synovial membrane by its
I race; while the extensor pedis tendon passes over its superficial
P °t, a synovial bursa being interposed. It is fixed above to the
lai'ge r
lateral
metacarpal, below to the first phalanx, and on each side to the
"garnent.
lections.—On one side of the joint the lateral ligament and the
P ent from the suspensory ligament to the extensor tendon must be
^°ved to expose the next ligament.
le Lateral Sesamoidean Ligaments. These are not to be con-
with the lateral ligaments of the joint, by which they are
}T covered. Each fixes the sesamoid of its own side to the upper
™xity of the first phalanx.
e Intersesamoid Ligamemt is the name given to the fibro-cartila-
tissue which unites the two sesamoids, and with them forms
«" ey-hke surface for the passage of the deep flexor tendon.
„ Synovial Membrane is supported in front by the anterior
'iganient ' «? Pressor D. J. Cunningham (Reports of the Challenger Expedition, Vol. V.), the
object lie l\ a^tel'ed flexor brevis of the middle digit, the corresponding muscle in the human
g t le 1st plantar interosseous muscle.
-ocr page 120-
52                                   THE ANATOMY OF THE HORSE.
ligament, and on each side by the lateral ligament. Behind the joint
it is supported below the sesamoids by the deep inferior sesamoideau
ligament, but above these bones it is unsupported;. and when the
synovial sac is distended, it bulges upwards between the branches of
the suspensory ligament (Fig. 1, page 33).
THE PASTERN-JOINT (PLATE 11).
This joint, which is technically termed the first interphalangeal
articulation, is formed between the distal end of the os suffraginis and
the proximal end of the os corona). It is a ginglymus, or hinge joint,
and corresponds to the second joint of the human finger.
Movements.—As with the joint last described, the only natural
movements are flexion and extension.
Directions.—The tendon of the extensor pedis, which passes over
the front of the joint, should be cut and reflected downwards. This
will show that the tendon completes the joint in front, where it plays
the part of an anterior ligament, and supports the synovial membrane.
The lateral ligaments are next to be defined, and after these, the
supplementary cartilaginous apparatus placed benind the joint.
The Lateral Ligaments. Each of these stretches from the lower
extremity of the first phalanx on its lateral aspect, to be inserted into
the side of the os coronas, and beyond that point some of its fibres are
continued downwards and backwards as the postero-lateral ligament of
the second interphalangeal joint.
The Glenoidal Fibro-Cartilage. This is a piece of fibro-cartilago
fixed at the posterior edge of the upper articular surface of the os
corona;. It serves to increase that surface, and its anterior face is
moulded on the lower articular surface of the first phalanx, while its
posterior face is smooth for the passage of the perforans tendon. Three
fibrous slips pass from it on each side, and are attached to the first
phalanx. The superficial inferior sesamoidean ligament is inserted into
it, and the terminal insertion of the perforatus tendon is blended with
it on each side.
Synovial Membrane. This is supported in front by the extensor
tendon, and on each side by the lateral ligament. Posteriorly it lines
the glenoidal fibro-cartilage, and is prolonged upwards as a pouch behind
the lower extremity of the first phalanx (Plate 10, fig. 2).
the coffin-joint (plate 11).
This, the second interphalangeal joint, has three bones entering into its
formation, viz., the os coronffi, the os pedis, and the navicular bone. I*
is a ginglymus, and corresponds to the first joint of the human finger.
Movements.—Flexion and extension.
-ocr page 121-
DISSECTION OF THE ANTERIOR LIMB.                                  53
Possesses an interosseous ligament, and two pairs of lateral ligaments,
e Interosseous Ligament is composed of short fibres passing from
e inferior border of the navicular bone to the os pedis behind its artic-
ular surface.
he Antero-Lateral Ligaments. Each of these passes from the side
he os ooronse to be inserted into the excavation at the side of the
Pyramidal process of the os pedis.
e Postero-Lateral Ligaments. These seem to be the downward con-
lations of the lateral ligaments of the pastern-joint. Passing from the
w the os coronse, each is inserted into the upper border of the nav-
of n V ne> and sends slips to the wing of the os pedis and inner surface
*he lateral cartilage.
' 'jovial Membrane. This is supported in front by the extensor
°n' an(^ laterally by the lateral ligaments. A protrusion of it passes on
side between the antero-lateral and postero-lateral ligaments, and
, m relation to the deep face of the lateral cartilage. A third protru-
of         ses upwards posteriorly, between the navicular bone and the back
the os coronse (Plate 10, fig. 2).
Abular view of the muscles of the fore limb in their
action on the different joints.
Shoulder.
( Superficial pectoral.
Adductors < Subscapularis.
(. Coraco-humeralis.
(Deltoid.
I Coraco-humeralis.
Pi
exors
I Latissimus dorsi.
Teres major.
Teres minor.
Scapulo-humeralis gracilis (?)
\Large head of triceps.
■^tensors j SuI>raspinatus.
t Mastoido-humeralis.
Deltoid
Teres minor
Infraspinatus
Rotators
outwards
C Mastoido-humeralis.
. Latissimus dorsi.
Rotators
inwards
Actors |
urs S
X
5eltoit1-.
Teres minor.
{Teres major.
Elbow.
( Triceps extensor cubiti.
Extensors \ Anconeus.
(, Scapulo-ulnaris.
Cahpus.
I Infraspinatus.
Fl
j Flexor brachi.
t Brachialis anticus.
exors
(EJexor metacarpi externus.
f Extensor metacarpi magnus.
J Extensor metacarpi obliquus.
J Extensor pedis.
V Extensor suffraginis.
flexors
Flexors
Plexors
I
; pi
exor metacarpi medius.
exor rnetacarpi interims.
Extensors
(Fjexor perforans.
flexor perforatus.
1 Flexor perforans.
tilexor perforatus.
f Flexor perforans.
( flexor perforatus.
Fetlock.
Extensor pedis.
Extensors
[ Extensor suffraginis.
Pastekn.
I Extensor —Extensor pedis.
Coffin-joint.
Flexor—Flexor perforans.         1 Extensor—Extensor pedis.
-ocr page 122-
Name op Muscle.
Origin.
Insertion.
Source of Nerve.
Anterior superficial pectoral
Posterior superficial pectoral
Anterior deep pectoral
Posterior deep pectoral
Serratus magnus
Levator anguli scapulae
Trapezius (cervical)
Trapezius (dorsal) .
Rhomboideus (cervical)
Rhomboideus (dorsal)
Latissimus dorsi
Mastoido-humeralis
Teres major
Subscapularis .
Humerus, outer lip of musculo-spiral groove .
Humerus (with the preceding) ; and super- {
flcial fascia of fore-arm ...         j
Fascia covering supraspinatus
Humerus, inner tuberosity; biceps tendon
and its retaining fascia ....
j Scapula, two triangular areas on ventral )
(         surface ......         j
Scapula, triangular area on ventral surface,
at cervical angle .....
( Scapula, tubercle of spine ; and aponeurosis ^
\         over outer scapular muscles . .         j
Scapuh, tubercle of spine ....
j Scapular cartilage of prolongation, inner 1
\         surface ......         j
Soapular cartilage (behind the preceding)
Humerus, inner tubercle         ....
Humerus, outer lip of musculo-spiral groove .
Humerus, inner tubercle         ....
Humerus, inner tuberosity
Sternum, first 2 or 3 inches of inferior border
1 Sternum, inferior border; and median fibrous
\         cord         .......
| Costal cartilages, 1st four; and sternum, .)
|         lateral surface ....         j
f Abdominal tunic; side of sternum; and tips of
\         costal cartilages, 5th, 6th, 7th, and 8th.
Ribs, 1st eight or nine .....
( Cervical vertebras, last four, transverse pro-
( cesses .......
Ligamentum nucha?, funicular portion .
f Anterior dorsal spines (or supraspinous liga- )
\         ment) ......         j
Ligamentum nuchas, funicular portion .
j Anterior dorsal spines (or supraspinous liga- \
\         ment)......j
f Vertebral spines, 4th dorsal to last lumbar )
\ (or supraspinous ligament) . . j
( Mastoid process and crest; and cervical ver- {
^         tebrre, 1st four, transverse processes j
i Scapula, dorsal angle ; and intermuscular (
(         septum (between it and subscapularis) J
Scapula, fossa of same name ....
From brachial plexus.
From brachial plexus.
From brachial plexus.
From brachial plexus
(2 branches).
From brachial plexus.
From Oth and 7th
cervical nerves.
Spinal accessory.
Spinal accessory.
Oth cervical.
Oth cervical.
From brachial plexus,
( Cervical nerves and
( circumflex.
Brachial plexus.
Brachial plexus.
-ocr page 123-
/ Ulna, olecranon process; and fascia of fore-arm I Muscnlo-spiral.             j
Vina, olecranon process.....I Musculo-spiral.              I
Scapula, posterior border ....
Scapula, dorsal angle and posterior border )
Humerus, shaft.....(
Humerus, shaft . . . . .         /
Humerus, margin of olecranon fossa . /
j Scapula, above and behind rim of glenoid \
{ cavity......(j
Scapula, coracoid process
Scapula, coracoid process ....
Scapula, dorsal angle; and scapular fascia .
( Scapula, posterior border, lower part of infra-
( spinous fossa, and tubercle on glenoid rim
j Scapula, infraspinous fossa ; and scapular
( fascia .......
f Scapula, supraspinous iussa ; and scapular
\ fascia .......
Humerus, shaft ......
Humerus, inner condyle         ....
j Humerus, inner condyle; and ulna, ole- (
(         cranon process (two heads) . .         j
Humerus, outer condyloid ridge
Humerus, inner condyloid ridge
Ulna, olecranon process ....
Humerus, inner condyloid ridge
Radius shaft ......
( Humerus, outer condyloid ridge, and de- ^
\         pression external to coronoid fossa         j
Radius, shaft.......
^Humerus, depression external to coronoid
s fossa; external lateral ligament of
V elbow ; and radius, upper extremity
iLateral ligament of elbow; radius, upper"!
< extremity; and line of junction of v
(. radius and tilna .... J
Perforans tendon......
Splint bone, head......
j Scapulo-ulnaris
Triceps extensor■/£*£*££*
cubltl- (caput rued
Anconeus
Scapulo-lmmeralis gracilis
Coraco-lmmeralis
Biceps
Deltoid .
Teres minor
Infraspinatus .
Supraspinatus
Brachialis anticus
Flexor metacarpi internus
Flexor metacarpi medius
Flexor metacarpi externus
Flexor perf oratus .
{ulnar head
humeral head
radial head.
Extensor metacarpi magnus
Extensor metacarpi obliqu is
Extensor pedis
Extensor suffraginis
Lumbricales (2)
Interossei (2) .
Circumflex.
Median.
Median (or its anterior
root).
Circumflex.
Circumflex.
Suprascapular.
Suprascapular.
( Musculocutaneous
( (of median).
Median.
Ulnar.
Musculo-spiral.
Ulnar.
Ulnar.
Median.
Median.
Musculo-spiral.
Musculo-spiral.
Musculo-spiral.
Musculo-spiral.
Plantar.
Plantar.
Humerus, shaft......
Humerus, shaft (two insertions)
Radius, bicipital tuberosity; and fascia of
fore-arm.......
Humerus, deltoid (outer) tubercle .
Humerus, ridge between outer tubercle and |
tuberosity......)
Humerus, outer tuberosity and ridge below (
it (two insertions)                                         )
Humerus, outer and inner tuberosities (two 1
insertions).....J
Radius and ulna, inner side ....
Inner splint bone, head.....
Pisiform, upper edge .....
j Pisiform, upper edge ; and inner splint bone;
|         head (two tendons)         ....
Os corona? (bifid tendon)         ....
Os pedis, semilunar crest and surface behind it
Large metacarpal bone, upper extremity
Inner splint bone, head ....
Os pedis, pyramidal process ; and to join
tendon of extensor suffraginis (two
tendons)......
Os suffraginis, upper extremity
Tissue beneath ergot of fetlock
j Suspensory ligament, band sent to extensor
t pedis tendon.....
-ocr page 124-
CHAPTER II.
DISSECTION OF THE POSTERIOR LIMB.
In the male subject, the dissection of the perinseum must be completed
before the dissector of the hind limb can begin his operations.
THE INNER ASPECT OP THE THIGH.
Position.—The animal should be placed on the middle line of its back,
and its hind limbs should be drawn forcibly upwards and outwards by
ropes running over pulleys fixed to the ceiling. This is the position
most convenient for allowing the dissection of both hind limbs to be
23ursued at the same time. If only one limb is being dissected, the rope
may be unfastened from that limb, and the body allowed to incline to
the same side, as in Plate 12.
Surface-marking.—The internal saphena vein ascends on the inner
aspect of the thigh; and a few inches below the upper limit of the region,
it dips in between the sartorius and gracilis muscles. Pressure at this
point in the living animal will produce distension of the vessel, and
render its course much more evident. Venesection is sometimes per-
formed on this vessel. Above the point where the before-mentioned
vessel disappears from view, the deep inguinal lymphatic glands are
situated in the interstice between the sartorius and gracilis muscles.
They here cover the femoral artery, and may be very distinctly felt in a
case of lymphangitis, or "weed."
Directions.—An incision through the skin is to be carried down the
middle line of the thigh, and terminated a few inches below the level of
the stifle-joint. Here another incision is to be made across the inner
aspect of the limb, from its anterior to its posterior border. These
incisions, together with those already made in the dissection of the
perinseum, will enable the dissector to reflect the skin as an anterior and
a posterior flap. The student should then dissect the internal saphcna
vein with its accompanying artery and nerve, and the cutaneous nerves
at the forepart of the region, which are derived from the lumbar nerves.
Thereafter the surface of the sartorius and gracilis is to be cleaned, and
these muscles are to be examined.
The Internal Saphena Vein (Plate 12). This is a large vessel
-ocr page 125-
DISSECTION OF THE POSTEEIOR LIMB.                                  57
on the inner side of the leg by the junction of an anterior and a
rior root, these being the upward continuations of the inner and
metatarsal veins. In the thigh it inclines upwards and forwards
j le 8ui'face of the gracilis, until it disappears between that muscle
Tv, sartorius, to empty itself into the femoral vein.
he Saphena Artery (Plate 12). This artery lies in front of the
, " It is a long and slender vessel given off by the femoral artery
o,. .,. middle of the femur. It conies out between the sartorius and
, lsi or it rnay pierce the edge of one of these muscles. It then
,               m front of the saphena vein, and finally divides into two
Ti 1<3S' Wnich accompany the roots of that vessel.
e Internal Saphenous Nerve (Plate 12) is a branch of the anterior
ural f
At k m wn'ch it is given off a little above the brim of the pelvis.
fe 6 crural arch (Poupart's ligament) it descends in front of the
It tl artery, to which and the sartorius muscle it supplies branches.
th 1 des into two cutaneous branches, which emerge from between
an 1 'rnas and the gracilis, in company with the saphenous artery
vem. The anterior half of the nerve gives off branches for the
J ot the thigh in front of the vein, and is continued downwards
Th 1G ^orePai't of the inner side of the leg, as far as the hock.
ter'         eri°r half sends branches backwards for the supply of the pos-
Part of the thigh, and it then descends behind the anterior half.
at tv> ANEous Branches from the lumbar nerves. These will be found
ace          rePart of the thigh, the largest (from the 3rd lumbar) being
TV, arue<^ by the posterior division of the circumflex iliac artery.
at ,, "Eecrural Lymphatic Glands. These are superficially placed
m ? UlUer side of the front of the thigh, on the track of the above-
°ned branch of the circumflex iliac artery.
ov         A' "^ *ne forepart of the region now exposed, the muscles are
to the read
Dy a strong membranous fascia, which is attached superiorly
Who • on °f the external oblique muscle of the abdomen, at the line
h0rri , ls reflected to form Poupart's ligament. Round the anterior
but vV,           thigh this fascia is continuous with the strong fascia lata ;
Part f ^ ced backwards, it becomes less fibrous, and over the posterior
the f. • re8'i011 it is thin and areolar. When it has been examined,
rpi         ls to be cleaned away from the subjacent muscles.
in        r^EEP In guinal Lymphatic Glands (Plate 45) are ten or twelve
in +}          ' and form a chain connected by areolar tissue, and situated
nil 1 PPer part of the interstice between the gracilis and sartorius
The^S aiUl °Ver the femoral vessels-
at Dr rtokius (Plate 12). This is a somewhat slender muscle which
deseeti 1 • Can ^e dissected only in a part of its course. It is seen
the ab 1 * Deileath Poupart's ligament, from its point of origin within
mal cavity. It there takes origin from the iliac fascia (Plate 45).
-ocr page 126-
58                                   THE ANATOMY OF THE HORSE.
In the thigh it lies in front of the gracilis. About the middle of their
line of apposition the saphena vessels and nerves emerge, but below that
point the muscles are adherent to each other. It is inserted into the
internal straight ligament of the patella.
Action.—To adduct and flex the hip-joint. To a slight extent it may
also rotate the limb inwards at the stifle.
The Gracilis (Plate 12). This muscle does not possess the slender
character from which it is named in human anatomy. It is a large,
somewhat four-sided mass, forming the greater part of what is termed
the flat of the thigh. A linear depression seen on the surface of the
muscle when it is cleaned, is often mistaken by students for the line of
separation between it and the sartorius. It arises from the lower face
of the pubis and ischium close to the symphysis, and it is here united
to its fellow of the opposite side. Inferiorly it has a broad flat tendon;
united in front to that of the sartorius. It is inserted with the sartorius
into the internal straight ligament of the patella, and into a line on the
tibia between its anterior and internal tuberosities. The posterior edge
of its tendon is continuous with the deep fascia of the leg. A large
branch from the external pudic veins traverses the muscle near its
origin, and opens into the femoral vein.
Action.—To adduct the hip, and rotate the limb inwards.
Directions.—The two preceding muscles are to bo carefully cut across
about their middle, and turned upwards and downwards. On reflecting
the proximal half of the gracilis, branches of the obturator nerve and
deep femoral artery will be seen penetrating its deep face; and, in the
same way, twigs from the saphena nerve wdll be found entering the
sartorius. The deep inguinal glands are to bo removed, and the
femoral vessels and anterior crural nerve are to be dissected.
The Femoral Artery (Plate 13) is the main arterial trunk for the
supply of the hind limb. It is the direct continuation of the external
iliac, the brim of the pelvis being selected as the arbitrary line oi
division between the two vessels ; and, in like manner, it is directly con-
tinued by the popliteal artery, the vessel changing its name when l*
passes between the two heads of the gastrocnemius muscle. The lower
third of the vessel, however, will not bo exposed till the next stage °'
the dissection. The part of the vessel now seen begins at the pehTic
brim, where it is seen issuing from beneath Poupart's ligament. *■
there rests on the common termination of the iliacus and psoas magnuSj
having the sartorius in front and the pectineus behind. In the thigh l*
descends obliquely downwards and backwards, resting first on the con*'
mon termination of the iliacus and psoas magnus, and then on the
vastus internus. It has the sartorius in front; while posteriorly it lS
related first to the pectineus, and then to the adductor parvus. In this
course it corresponds to the interstice between the gracilis and sartorius
-ocr page 127-
DISSECTION OF THE POSTERIOR LIMB.                                  59
Muscles
closely
and is covered by the deep inguinal lymphatic glands. It is
related to the femoral vein, which lies beneath and slightly pos-
—-*G_ik. except at the brim of ffie pelvis, where the vein is imme-
J posterior to the artery. In the present stage of the dissection
jj, Lssel disappears between the upper and lower insertions of the
coll °r ma8'nus! where it will subsequently be followed. The following
eral branches of the femoral are here seen :—
0fp ' le Profunda or Deep Femoral Artery. This branch is given
u . er Poupart's ligament at the pelvic brim. At its origin it
j. ' - i°nns a short common trunk with the prcpubic artery. It
foil ^wnwards and backwards under the pectiueus, and will be
en in the next stage of the dissection.
ar-T' Muscular Branches. The largest of these is a vessel of consider-
'ize for the supply of the quadriceps extensor cruris muscle. It
„          °": at about the same level as the profunda, which it generally
Hi) 1 S U1 Vamme j an(l passing over the psoas magnus and iliacus, and
int            sartorius, it penetrates between the rectus femoris and vastus
a , . ' lri company with the anterior crural nerve. Other innominate
°t smaller size enter the vastus internus, pectineus, gracilis,
Cronus, and adductors.
' ^'ie Saphena Artery already described (page 57).
ins '          Nutrient Artery of the Femur is given off at the tendon of
85ei*«>n of the pectineus.
;,.. " u Articular branch, of slender volume, descends between the vastus
mterr-
T)11U8-aUCl adductor magnus to the stifle-joint.
re . Femoral Vein ascends in close company with the artery, and
d            wanches which correspond more or less exactly to those just
c°ntimi
The Ant
erior Crural Nerve (Plate 13) is derived from the lumbo-
Da • "          us' It descends between the psoas magnus and parvus ; and
wj _ * over the common termination of the iliacus and psoas magnus,
is covered by the sartorius, it splits into a bundle of branches
5©tJier penetrate between the vastus internus and rectus femoris
c * ' " the mass of the quadriceps extensor cruris. While under
escr
Si
, . '%ms-—The pectineus, adductor parvus, adductor magnus, and
m , embranosus muscles are now to be cleaned and isolated. These
Son j ■ Succee<^ each other from before to behind in the order named,
tion 1 ' difficulty may be experienced in finding the line of separa-
of 8 Ween the two adductors, but a reference to Plate 13 will prove
Pale • > assistance- Moreover, the fibres of the small adductor are of a
0ur than those of the adductor mairnus.
-ocr page 128-
GO
THE ANATOMY OF THE HOHSE.
The Pectineus (Plate 13). This muscle has a distinctly conical forto-
It lies posterior to the femoral vessels, and the profunda artery disap-
pears beneath it. It arises from the brim and inferior surface of the
pubis, and it is there penetrated by the pubio-femoral ligament, fro'11
which some of its fibres take origin. Its tapering point is inserted into
the shaft of the femur in the neighbourhood of the nutrient foramen.
Action.—It adducts the limb, and flexes the hip.
The Adductor Parvus (Adductor brevis of Percivall) (Plate 13) is Sit*1'
ated between the pectineus and the great adductor. It arises from the
inferior surface of the pubis, and is inserted into the posterior surface ot
the femur about its middle.
Action.-—It is an adductor and outward-rotator at the hip-joint.
The Adductor Magnus (Adductor longus of Percivall) (Plate 13)
arises from the inferior surface of the ischium, and from the tendon °*
origin of the gracilis. It has two insertions, between which the femoral
artery passes. 1. Its deeper fibres are inserted into the posterior surface
of the femur, on a quadrilateral area above the smooth groove in which
the femoral artery rest's. 2. Its more superficial and longer fibres are
inserted into the forepart of the supracondyloid crest.
Action.—It is an adductor at the hip.
The Semimembranosus (Adductor magnus of Percivall) (Plate 13). Tins
is a muscle of large size. It arises from the lower surface of the ischium;
including its tuberosity, and by a small slip from the fascia investing'
the muscles of the tail. It is inserted into the inner condyle of the
femur, behind the tubercle for the attachment of the internal lateral
ligament of the stifle.
Action.—Commonly, it is an adductor and extensor of the hip; but
when the femur is fixed, it acts as a lever of the first order, and assists
in rearing.
Directions.—The foregoing muscles must now be cut and partially
removed as follows :—
The semimembranosus is to be cut transversely, an inch or two above
its insertion. The muscle is then to be raised upwards from the scffU-
tendinosus, on which it rests; and in doing this, branches of nerves
from the great sciatic will be found entering it in front. The central
portion of the muscle may then be removed, leaving a few inches at its
origin. The other muscles must be served in the same way, leaving
only short portions at the origin and insertion, except in the case of the
adductor jjarvus and upper half of the adductor magnus, whose
common insertion into the back of the femur is to be entirely removed'
Care is to be taken of the femoral artery where it rests on the bone, and
in performing the dissection it will be well to refer to Plate 14 as a
guide. In reflecting the upper portion of the great adductor, a branch
of the obturator nerve will be found entering its deep face, after having
-ocr page 129-
DISSECTION OF THE POSTERIOR LIMB.                                  61
ci through the obturator externus muscle. Other branches of the
nerve will be found supplying the small adductor and the pecti-
le Femoral Artery (Plate 14). The remaining portion of this
»          is now exposed as it winds round behind the shaft of the
' having its impress on the bone. It is seen passing in between
iads of the gastrocnemius muscle, at which point it takes the
ot popliteal. In this part of its course it gives off only one vessel
^te—the femoro-popliteal.
• Emoro-popliteal Artery. The point of origin of this branch
s the lower limit of the femoral artery. It passes backwards in a
' ntal direction, and penetrates the semitendinosus. Near its origin
b
ft> » ott a considerable branch which ascends behind the femur, sup-
I => *ne biceps, and anastomosing with the profunda. Other branches
W from it to the gastrocnemius,
tr LITEAL Lymphatic Glands. A few glands will be found on the
hi.          ^le femoro-popliteal artery between the semitendinosus and
°eps fenioris muscles.
e Profunda or Deep Femoral Artery. In the preceding
stage of +1
o ui the dissection this branch of the femoral was seen at its
rif?m t*.
ed                passes downwards and backwards, between the adjacent
. * ' °* the iliacus and obturator externus, and under cover of the
leus and adductor parvus. Above the insertion of the quadratus
to 1S l* orosses behind the femur, where its terminal branches descend
. PPv the biceps. It also furnishes collateral branches to the
ylneus. gracilis, and adductors,
th               ^ne foregoing arteries are accompanied by satellite veins of
J*0* names.
rib C <^XJADKATlJS Femoris (Plates 14 and 16). This is a somewhat slender
in fi. aPe<^ nauscle. It arises from the lower surface of the ischium
0            °f the tuberosity, and it becomes inserted into an oblique line
back of the femur, at the level of the third trochanter.
TV,               ^8 an extensor and outward-rotator at the hip.
fas • B URAT0R Externus (Plate 14). This muscle, which is coarsely
a r ated, covers the obturator foramen, and conceals the obturator
t          aU vessels as they emerge from the pelvis. It is traversed by
°'r + an°nes of the obturator nerve, the posterior of which is for the
of fl ' c*orJ while the anterior splits into branches for the supply
8u „ Iaa" adductor, pectiueus, and gracilis. It arises from the lower
fos '                 pubis and ischium, and is inserted into the trochanteric
j^. •' +t is an extensor and outward-rotator at the hip.
sho li ' l°m' ^he nerves which emerge from the obturator externus
'e traced through the substance of that muscle to their origin
-ocr page 130-
62                                   THE ANATOMY OF THE HOESE.
from the obturator nerve. The muscle itself may then be removed to
expose the obturator vessels and nerve.
The Obturator Artery (Plates 14 and 46). This vessel begins at the
pelvic inlet as one of the terminal branches of the internal iliac. I*
leaves the pelvis by the obturator foramen, in company with a vein and
nerve of the same name. At its point of emergence it is covered by
the obturator externus, and it passes backwards between that muscle
and the bone, and then curves downwards to terminate in the biceps
and semitendinosus. It gives off the artery of the corpus cavernomm.
The Obturator Vein passes into the pelvis by the obturator foramen*
and aids in forming the internal iliac vein.
The Obturator Nerve is a branch of the lumbo-sacral plexus.
Emerging by the obturator foramen, it divides for the supply of the
obturator externus, adductor parvus, adductor magnus, pectineus, and
gracilis muscles.
Directions.—In this stage of the dissection the great sciatic nerve is
seen in its course downwards through the thigh. Its examination is
more conveniently undertaken in the dissection of the hip and outer
aspect of the thigh, but attention may also be given to it here.
The Great Sciatic Nerve, which is a branch of the lumbo-saCr8*
plexus, after passing through the hip (see Plate 16), descends in the
thigh, behind the femur, where it is deeply enclosed between the
biceps and semitendinosus outwardly, and the semimembranosus and
great adductor inwardly. Under the name of the internal popliteal, $
passes in between the two heads of the gastrocnemius. The following
branches whose points of origin are not now visible, being situated i°
the hip, may be identified by reference to Plate 14:—(1) Branches to the
biceps, semitendinosus, and semimembranosus; (2) the external pop'
liteal; (3) the external saphenous. The last two will be again seen in
the dissections of the hip, thigh, and leg.
Directions.—The vastus interims, situated at the front of the thigh
should now be examined. It is a division of the great muscular mass
termed in man the quadriceps extensor cruris, whose other divisions—the
rectus femoris and vastus externus—will be dissected with the outer
aspect of the thigh. The dissection in this position of the limb will he
completed by an examination of the common insertion of the iliacus
and psoas magnus.
The Vastus Internus (and Crureus *) (Plates 13 and 14) is a thick
fleshy muscle whose fibres take origin from the internal surface and inner
half of the anterior surface of the femur, meeting along the front of the
femur the vastus internus, and with it forming a groove in which the
rectus femoris rests. Its fibres are inserted into the inner ligament of
* This is the name given to the fourth division of the quadriceps in human anatomy. The &tei
that represent it in the horse are in no way separable from the inner vastus. Under the same na"ia
Percivall describes (inac