JNO. T. SHARE-JONES, F.R.C.V.S.

LECTURER IN CHARGE OF THE DEPARTMENT OF VETERINARY ANATOMY IN

THE UNIVERSITY OF LIVERPOOL ; FORMERLY TUTOR IN SURGERY

AND DEMONSTRATOR OF ANATOMY AT THE ROYAL

VETERINARY COLLEGE, LONDON, ETC.

LONDON
WILLIAMS AND NORGATE

14 HENRIETTA ST., COVENT GARDEN

Printed by Ballantyne &* Co. Limited
at the Ballantyne Press, London

Owing to the greater surgical importance of the limbs in veterinary
practice, consecutive treatment has been dealt with a little more fully
in this volume than in Part I., otherwise precisely similar lines have been
followed.

To the Vice-Chancellor of the University of Liverpool the author
desires again to express his gratitude for the ever-ready advice and kindly
help, of which it has been the author's good fortune to avail himself.

The onerous task of revising and correcting the proofs has been
kindly undertaken by the author's friend and former colleague, Professor
Macqueen, many of whose views upon matters appertaining to the purely
surgical part of the work have been adopted. Although these have been
frequently acknowledged throughout this volume and were referred to in
the General Preface to Part I., the author feels it his duty to make
reference to them here, for to have had the collaboration of one with the
ripe experience of Professor Macqueen cannot fail to add materially to
the practical value of the work.

The kind reception accorded the first volume by the majority of the
critics and by practitioners generally in this country, and especially by
his fellow veterinarians in France and America has been most gratifying
to the author, and has convinced him that his opinion of the necessity
which existed for a work of the kind, as expressed in the Preface to
Part I., was well founded.

It was pointedly remarked by one esteemed reviewer, presumably a
member of our sister profession, that "since 1832. when William

Percival produced the first work exclusively devoted to the anatomy of
the horse, considerable advances have been made in the methods of
teaching veterinary anatomy ; but it cannot be said that the production
of anatomical literature has been correspondingly abundant in this
country. The veterinarian has not had his time too heavily taxed by
the examination of frequent new publications." The justice of this soft
impeachment is best known to the members of the veterinary profession,
and the intended mission of the writer will therefore be amply fulfilled if
the effort be considered by his fellow workers to be a useful contribution
to this unfortunately too inadequate supply of veterinary literature.

To the judgment of practitioners, who are best qualified to know
their own wants, and at whose hands the first part of this work was
so charitably received, without further remark this volume is now
committed.

Department of Veterinary Anatomy,

The University of Liverpool.

PART II�-THE FORE LIMB

I. SUPERFICIAL EXAMINATION........ i

II. SUPERFICIAL DISSECTIONS........ 9

III. THE LIMB IN SECTION......... 31

IV. THE BONES�FRACTURES AND EXOSTOSES . . . .40

V. THE JOINTS............ 72

VI. THE TENDONS, LIGAMENTS, TENDON SHEATHS, AND

BURS.E............ 117

VII. THE NERVES............ 138

VIII. THE BLOOD AND LYMPH VESSELS....... 167

MUSCLES OF FORE LIMB......... 186

IV. Superficial Dissection of Fore Limb, Outer Aspect .
V. Superficial Dissection of Fore Limb, Outer Aspect (continued')
VI. Superficial Dissection of Fore Limb, Inner Aspect

VII. Superficial Dissection of Fore Limb, Inner Aspect (continued)

VIII. Longitudinal Section......

IX. Transverse Section just below Seat of Median Neurectomy
XXI. Transverse Section across Knee .....

⁵XXX. Seat of Median Neurectomy Dissected ....

I. Outer Aspect of Shoulder and Arm
II. Right Fore Limb. Outer Aspect
III. Inner Aspect of Right Fore Limb
X. Transverse Section across Left Metacarpus
XI. Transverse Section across Fetlock of Left Fore Limb
XII. The Scapula

XIV. Left Radius and Ulna
XV. Left Radius and Ulna

XVI. Carpal and Metacarpal Bones
XVII. Os Suffraginis and Os Corona
XVIII. Long and Short Pastern Bones (showing Exostoses)

This Plate has been placed so, in order that it may be near the text to which it relates.

facing
plate page

XIX. The Scapulo-Humeral Articulation (Outer Aspect) ... 74

XX. The Elbow Joint (Outer Aspect)�The Bones ..... 80

XXII. Tendons Playing over Front of Knee ...... 88

XXIII. Cherry's Operation (Slightly Modified)...... 98

XXIV. Transverse Section of Pastern Joint showing Articular Surfaces,

Ligaments, Tendons and Complementary Cartilage . . .112
XXV. Outer Aspect of Right Knee showing Distended Sheaths (Semi-
Schematic) ........... 120

XXVI. A.�The Subcarpal Ligament. B.�Seat of Tenotomy of the

Flexors of the Digit, etc. . . . . . . . .130

XXVII. Right Fore Limb. Outer Aspect showing Sheaths at Fetlock. . 132

XXVIII. The Sesamoidean Ligaments ........ 136

XXIX. A �First Rib of Left Side�Outer Aspect. B.�First Rib of Left
Side�Inner Aspect. C.�First Rib of Left Side�Showing
Seat of Fracture "A" . . . . . . . . . 148

XXXI. Seat of Ulnar Neurectomy with Ulnar Nerve Exposed . . 152

XXXII. Seat of Ulnar Neurectomy�the Seat in Section . . . 154

XXXIII. A. �A Common Seat of " Speedy-Cutting." B.�Seat of Internal

Plantar Neurectomy. C�Seat of Digital Neurectomy.

D.�Seat of Internal Plantar Neurectomy in Section . .164

XXXIV. The Carpal Arterial Arches and the Veins of the Fore Limb . 176

Page 3, line 15, for "liable " read "likely."

� 4, � 15, insert "external" after "splints."
� 6, fourth line from bottom,for "plantar nerve"

read " digital artery."
� 20, line 16, after " elbow " add "and extensor of shoulder.
� 28 (facing), for " Plate VI " read " Plate VII."
� 32, line 13, for " attachment " read "attachments."
� 51, � 1, for "solar " read " plantar."
� 122, line 11 delete " further "

Plate XXI, 12, delete "internal."

SUPERFICIAL EXAMINATION

The student should first examine the outer aspect of the region of the
shoulder, and endeavour as near as possible to locate the outline of the
scapula. Having done this, it will be observed that running obliquely
downwards and forwards over the area enclosed by the imaginary outline
drawn, there are four elevations, which are formed by the following
muscles :

The most superior or anterior elevation indicates the position of the
supraspinatus muscle, which lies in the supraspinous fossa and is attached
inferiorly to the anterior divisions of both tuberosities at the proximal
end of the humerus. Between the two tendons of insertion of this muscle
the tendon of origin of the biceps emerges. The second elevation is
formed by the infraspinatus muscle. This muscle has two tendons of
insertion also, one of which is attached to the inner side of the
convexity (i.e., the more posterior of the two divisions of the external
tuberosity), whilst the other tendon plays over the outer aspect of the
convexity and is inserted into the upper extremity of the deltoid ridge.
A small synovial bursa is placed between this tendon and the outer
surface of the convexity. Between the two muscles named, the tubercle
of the spine of the scapula may be easily located. It is important to
note that the tendons of the supraspinatus and infraspinatus muscles by
their disposition materially assist in keeping the head of the humerus in

Plate I.�Outer Aspect of Shoulder and Arm

i. Elevation formed by caput muscles. 2. Point of elbow (summit of olecranon process ot
ulna). 3. Position of elbow articulation. 4. Elevation formed by flexor metacarpi externus
muscle. 5. Elevation formed by extensor pedis. 6. Elevation formed by extensor metacarpi
magnus. 7. Groove between brachialis anticus and mastoido-humeralis. S. Point of
shoulder. 9. Groove in front of or above supraspinatus muscle.

2 THE SURGICAL ANATOMY OF THE HORSE

the glenoid cavity of the scapula. These muscles are affected in supra-
scapular paralysis, and it will be seen that when this affection has
advanced to such a degree that the muscles become atrophied, the long
axes of the muscles and their tendons become considerably increased in
length on account of the diminution in width of the bellies. This
increased length causes a relaxation of the parts, with the result that we
have one of the diagnostic symptoms of suprascapular paralysis, viz., free
external rotation of the head or the humerus. Internal rotation is
prevented by the tendon of the subscapularis muscle, which is not affected
in this paralysis. The two posterior elevations are formed by the
underlying deltoid muscle, which arises from the posterior border of the
scapula and is inserted into the deltoid tubercle of the humerus. The
appearance of two elevations is due to a false septum in the muscle
caused by a dipping inwards of the scapular fascia which binds this
muscle to the preceding one and to the underlying bone.

The point of the shoulder is formed by the coracoid process of the
scapula. This should be carefully palpated, since it is a common seat of
fracture, particularly in young animals, the fracture being usually due to
the shoulder being caught in a doorway or narrow gateway. Running
over the shoulder joint and spreading out as it descends is the mastoido-
humeralis muscle. Inferiorly to the shoulder this muscle again
becomes narrower, and runs to its insertion into the outer lip of the
musculo-spiral groove. Near the upper border of the mastoido-humeralis
and just in front of the point of the shoulder is the common seat of
" shoulder tumour " or " abscess."

The long axis of the scapula runs downwards and forwards, and meets
the long axis of the humerus, which runs downwards and backwards
forming an acute angle at the shoulder joint. The triangle, of which
these two bones form the antero-superior and antero-inferior sides, is
filled by a large muscular mass which is indicated on the exterior by a
well-marked convex bulging of distinct outline. This mass is formed
by the triceps extensor cubiti or caput muscles, which are inserted into

Plate II.�Right Fore Limb. Outer Aspect

i. Position of elbow articulation. 3. Flexor metacarpi externus. 3. Elevation caused by
pisiform bone. 4. External small metacarpal bone. 5. Edge of tendon of flexor perforans.
6. Level of bases of sesamoid bones. 7. Situation of pastern joint. 8. Os suffraginis.
9. Position of fetlock articulation. 10. Large metacarpal bone. 11. Edge of radius.
13. Elevation formed by belly of extensor pedis. 13. Elevation formed by belly of extensor
metacarpi magnus.

SUPERFICIAL EXAMINATION 3

the summit of the olecranon process, and are the great extensors of the
elbow. The marked convexity of these muscles should be observed, since
in advanced cases of radial paralysis or " dropped elbow," in place of the
convexity we have a marked depression, due to the fact that these muscles
have become atrophied.

What is commonly known as the " point " of the elbow corresponds
to the position of the summit of the olecranon process of the ulna. The
elbow joint is placed from three to four inches downwards and forwards
from this point, varying, of course, according to the size of the animal,
and is indicated externally by a slight depression. It will be observed
that there is an almost entire absence of muscular tissue en the outer
aspect of the joint, which is here therefore very badly protected, a fact
which renders it necessary to treat wounds in the neighbourhood of the
joint with great care ; otherwise an open arthritis of the joint is a very
liable complication.

Passing the hand down the front of the forearm, a very prominent
and well-defined elevation is felt. This raised surface corresponds to the
bellies of two muscles, the more anterior of which is the extensor meta-
carpi magnus, whilst the other is the extensor pedis. Behind the
extensor pedis is placed the flexor metacarpi externus muscle, which is
indicated externally by a slight and elongated elevation. Between these
two muscles is situate the extensor sufFraginis muscle, which does not
provide any superficial marking, since it is wedged in somewhat tightly
between the two muscles named. The tendons of the extensor pedis
and extensor metacarpi magnus run over the front of the knee after
having passed through the two vertical grooves on the anterior aspect of
the inferior extremity of the radius, whilst that of the extensor sufFra-
ginis passes through a groove on the outer side of the inferior extremity
of this bone. The tendon of the flexor metacarpi externus will be found
to terminate just above the knee and on its postero-external aspect, where
we feel a well-marked, hard ridge. This ridge corresponds to the upper
border of the pisiform bone, and it should be remarked that this edge of

Plate III.�Inner Aspect of "Off" Fore Limb

i. Edge of posterior superficial pectoral muscle. 2. Median nerve exposed. 3. Elevation
formed by flexor metacarpi internus. 4. Elevation formed by extensor metacarpi magnus.
5. Chestnut. 6. Ridge of the Radius. 7. Position of ridge of pisiform bone. 8. Internal
plantar nerve exposed. 9. Digital nerve exposed.

4 THE SURGICAL ANATOMY OF THE HORSE

the pisiform is almost immediately subcutaneous�a point which is of
considerable surgical importance in dealing with affections of the knee
which require tight bandaging for any considerable length of time. In
such cases the pressure of the bandage should be taken off the edge of
the pisiform bone by applying a roll of cotton wool or tow on either
side ; otherwise the continuous pressure on the skin over the sharp edge
of the bone will lead to a serious complication in the form of the bone
making its appearance through the skin.

The outermost bones of the two rows of the carpus, namely the
cuneiform and the unciform, should next be felt, and below the unciform
the head of the outer small metacarpal or " splint " bone will be detected,
from which without any difficulty the finger may be passed along the
groove which corresponds to the line of apposition of the large and outer
small metacarpal bones. This groove indicates the most common situa-
tion of splints, and particular familiarity should be made with it imme-
diately below the knee, for here we find what are known as " knee
splints," which are the most troublesome form of this affection.

Between the knee and the fetlock it will be found that the anterior
aspect of the large metacarpal bone is immediately subcutaneous, but
towards the outer side of this aspect the tendon of the extensor pedis
muscle may be easily felt, and externally to that again the tendon of the
extensor suffraginis muscle. At a point which is distant from two
and a half to three and a half inches below the knee and immediately
behind the small metacarpal bone there will be felt a slight thickening,
which indicates the position where the subcarpal or check ligament
unites with the tendon of the deep flexor of the digit, and which
thickening must not be mistaken for fibrous enlargement due to a
chronic sprain of the tendon. By taking up the foot and flexing the
knee, the edge of the ligament becomes much more evident to the
touch.

The next step is carefully to manipulate the skin over the back
tendons, namely, those of the flexor perforatus and flexor perforans

Plate IV.�SUPERFICIAL DISSECTION.

Fore Limb (right), Outer aspect.�I. Cartilage of prolongation. 2. Spine of scapula. 3. Dorsal angle

scapula. 4. Tubercle of spine. 5. Infraspinatus muscle. 6. Supraspinatus. 7. Caput magnum. 8. Tendon

infraspinatus. 9. Deltoid muscle. 10. Outer tendon of supraspinatus. II. Insertion of deltoid. 12. Anterior

^'vision °[ external tuberosity of humerus [i.e., the summit). 13. Upper portion of deltoid ridge. 14. Tendon of

j'^lg'ⁿ ^of biceps. 15. Caput medium. 16. Biceps muscle. 17. Brachialis anticus. 18. Insertion of mastoido-humeralis.

21 i^⁸⁶¹¹"¹⁰¹¹ °f caput muscles into summit of olecran

� r lexor metacarpi externus. 22. Extensor pedis.

SUPERFICIAL EXAMINATION 5

muscles. These tendons should be felt as far as possible throughout
their length, beginning at the knee, immediately below which they
will be found at the spot where they leave the carpal arch. Just
above the fetlock the tendon of the deep flexor will be found to
disappear, for it here enters the fibrous ring formed for its passage by
the perforatus tendon. The perforans, however, will be felt to make
its reappearance just below the joint, where it emerges from the
fibrous tube mentioned.

Careful manipulation of the outer side 01 the fetlock will reveal
the presence of a hard, flat band which runs downwards and forwards
to the anterior aspect of the limb, where it joins the tendon of the
extensor pedis muscle. This band is the external division of the
suspensory ligament, which has divided just above the fetlock after
traversing the channel formed by the large and two small metacarpal
bones. This slip of the suspensory ligament will be found to broaden
out and to become much less apparent to the touch as we descend to
its insertion. It is sometimes ruptured, particularly in young animals.
Near where the suspensory ligament divides the small metacarpal bone
will be found to terminate in a small rounded nodule. This is known
as the " button" or the splint bone, and must not be mistaken for
a splint.

The upper part of the inner aspect of the limb is best examined
on a dead specimen. The limb should be disarticulated at the shoulder
joint, and the inner cutaneous incision should be made as high up
as possible in the armpit. The first point we notice is the curve
indicating the inferior border of the posterior superficial pectoral
muscle. This in most animals may be distinctly seen, but in all it may
be easily felt. Extending vertically, and almost in the middle line of
this aspect, will be felt an osseous ridge. This is the inner edge of the
radius. Behind this ridge is a vertical groove, and posterior to the groove
again we have a vertically elongated elevation which corresponds to the
position of the belly of the flexor rnetacarpi internus muscle.

Plate V.-SUPERFICIAL DISSECTION {continued).

Fore Limb (Right), Outer aspect.�21. Flexor metacarpi extermis muscle. 22. Extensor pedis. 23. Ulnar
accessorius. 24. Extensor metacarpi obliquus. 25. Extensor suffraginis. 26. Tendon of extensor metacarpi magnus.

/� Interosseous artery of forearm. 28. Tendon of extensor pedis. 29. Cutaneous branches of ulnar nerve.
3°- Tendon of extensor suffraginis with reinforcing band. 31. Tendon of perforatus leaving carpal sheath. 32. External
metacarpal vein. 33. Perforans tendon leaving carpal sheath. 34. Suspensory ligament. 35. Small artery descending
with plantar nerve. 36. External digital vein. 37. External plantar nerve. 38. Button of external small metacarpal

one 39. Body of ditto. 40. Anterior digital nerve. 41. Branch connecting the two plantar nerves. 42. Middle
/iff n ^nerve' . 43- External digital artery. 44. Outer division of suspensory ligament. 45. Posterior digital nerve.
4 � Os suffraginis. 47. Perpendicular artery of pastern. 48. Plexus of veins.

6 THE SURGICAL ANATOMY OF THE HORSE

Just above the lower edge of the posterior superficial pectoral
muscle and in a line with the ridge of the radius, if a little pressure
be applied, the posterior radial artery may be located in the living
subject by its pulsation, which may be more easily felt if the limb
be drawn a little forward. This is a very popular seat for the taking
of the pulse. It is also the seat of neurectomy of the median nerve,
which will be referred to later.

Anterior to the ridge of the radius we see the inner aspect of
the elevation formed by the extensor metacarpi magnus, to which
reference has already been made. In the inferior third of the fore-
arm we have the " chesnut," a horny excrescence which upon
manipulation will be found to be confined to the skin. The inner
surface of the scaphoid and trapezoid, the innermost bones of the two
rows of the carpus, should now be felt, and the faint depression
between them noted.

Below the knee the tendons of the perforatus and perforans make
their appearance, and may be felt as they are leaving the carpal
arch. It is scarcely necessary here to impress the student with the
importance of making himself quite familiar with these tendons,
particularly where the check ligament joins the perforans, again
immediately above the fetlock, and lastly just below this joint, where
the perforans is leaving the ring formed by the perforatus, since at
these situations the tendons are most commonly sprained. If the knee
be flexed and the flexor tendons pushed aside, the suspensory ligament
may be felt in the channel formed by the large and small metacarpal
bones.

By the application of pressure with the palmar aspect of the medius
finger to the outer or inner side of the most prominent part of the
fetlock, the plantar nerve may be rolled beneath the finger about half
an inch posteriorly to the middle line. This should be practised, since
it is of utility in deciding the seat of plantar neurectomy. The most
prominent point at the back of the fetlock presents another horny

Fore Limb (right), Inner aspect.�r. Subscapulars muscle. 2. Cartilage of prolongation. 3. Supraspinatus muscle. 4. Teres
major. 5. Subscapular nerve. 6. Nerve to latissimus dorsi. 7. Brachial plexus. 8. Subcutaneous thoracic nerve, 9. Suprascapular
artery. 10. Subscapular artery (branch of) 11. Suprascapular nerve. 12. Nerve to teres major. 13. Anterior root of median nerve.
14 Circumflex nerve. 15. Posterior root of median nerve. 16. Musculo-spiral nerve. 17. Cut end of axillary artery lying in loop
connecting the two roots of the median nerve. 18. Artery to latissimus dorsi. 19. Inner tuberosity of humerus. 20. Axillary artery
continued inferiorly as the brachial. 21. Median nerve. 22. Scapulo-ulnaris muscle (the upper end has been removed to display the
structures beneath it). 23, Nerve to the biceps muscle. 24. Brachial vein. 25. Prehumeral artery and vein. 26. Deep humeral artery
and vein. 27. Coraco-humeralis muscle. 27A. Musculo-cutaneous branch of median nerve. 28. Ulnar nerve (slightly displaced, see below).
29. Biceps muscle. 29A. Artery to biceps. 30. Ulnar artery. 31. Cut end of basilic vein (the vein has pierced the posterior superficial
pectoral muscle and unites with the posterior radial and ulnar veins to form the brachial vein). 32. Ulnar vein. 33 and 33A. Posterior
radial vein and artery with median nerve between them. 34. Summit of olecranon process of ulna. 35. Flexor metacarpi internus.
36. Flexor metacarpi medius, 37. Extensor metacarpi magnus.

The brachial plexus has been pinned down to secure it in position. It is thus flattened out, with the result that the ulnar nerve (which
has been drawn slightly backwards with the scapulo-ulnaris muscle) runs down behind, instead of in front of, the musculo-spiral.

SUPERFICIAL EXAMINATION 7

excrescence called the " ergot," surrounded by a tuft of long hairs.
Subjacent to the skin and tendons in this position are the two sesamoid
bones, the location of which may be decided by the fact that they
move slightly towards the middle line upon the application of pressure
to the outer surface of each with the thumb and finger.

Immediately below the sesamoid bone on either side of the limb
is a depression in which the edge of the perforans tendon may be felt,
and which is the seat of inferior plantar, or more correctly digital,
neurectomy.

The region of the pastern should next be grasped with the hand,
in order that the observer may familiarise himself with the conformation
of the long pastern bone or os suffraginis.

It will be found helpful if, whilst making this examination, the
student has a dried bone near, in order that he may compare the buttress-
like processes at the upper extremity of the bone with the elevations
formed by them in the limb. The palmar aspect of the hand should
be passed over this region several times, until the student has quite
satisfied himself by comparison with the dried bone that these elevations
are normal. The next point of importance is the position of the pastern
joint, which will be found about an inch to an inch and a half above
the line of junction of the skin and hoof. This joint is covered
anteriorly by the flattened-out tendon of the extensor pedis. There is
no anterior common ligament, so that the tendon is next the joint and
gives support to the synovial membrane. Posteriorly the joint is well
protected by the fibro-cartilaginous pad which projects upwards from
the superior extremity of the back of the os coronas. According to
Hunting's classification of ringbones, this joint is the seat of the class
designated by the term "high," the " low ringbones " being those which
affect the corono-pedal joint. The so-called false ringbones are placed
on the sufFraginis or corona?, but do not affect the joints. By carefully
manipulating the top of the hoof, the upper borders of the lateral
cartilages will be felt. These cartilages, so far as they project above

Plate VI.�SUPERFICIAL DISSECFION (continued).

Fore Limb (right), Inner aspect.�33 and 33A. Posterior radial vein and artery with median nerve between them. 34. Summit
of olecranon process of ulna. 35. Flexor metacarpi internus, 36. Flexor metacarpi medius. 36A. Flexor accessorius. 37. Extensor
metacarpi magnus. 38. Radius. 39. Posterior radial artery. 40. Branch of median to assist in forming external plantar nerve.
41. Large metacarpal artery. 42. Artery to supracarpal arch. 43. Small metacarpal artery. 44. Ulnar branch to external plantar nerve.
45. Internal metacarpal vein, which is cut through, since its upward continuation is more superficially placed. 46. Tendon of extensor
metacarpi obliquus. 47. Tendon of extensor metacarpi magnus. 48. Perforatus tendon leaving carpal sheath. 49. Dorsal interosseous
artery. 50. Plantar nerve (internal). 51. Suspensory ligament. 52. Large metacarpal artery. 53. Large metacarpal bone. _ 54. Perforans
tendon. 55. Internal small metacarpal bone. 56. Communicating branch to external plantar nerve. 57 and 58. Internal digital vein and
artery. 59. Anterior digital nerve. 60. Posterior digital nerve. 61. Inner division of suspensory ligament. 62. Ring formed by perforatus.
63. Tendon of extensor pedis. 64. Tendon of perforans. 65. Middle digital nerve. 66. Plexus of veins.

N.B,�Lines 48 and 54 should terminate slightly behind the white line (50) indicating the nerve.

8 THE SURGICAL ANATOMY OF THE HORSE

the hoof, should be traced out, and it should be noted that the
greater part of the cartilage is placed within the hoof. If the foot
be taken up in the living animal and the cartilages placed between
the thumbs, the palmar aspect of the hands being applied to the wall
of the hoof, a little pressure will distinctly reveal their elasticity.

Plate VIII.�Longitudinal Section of " Off " Fore Limb, from Knee downwards, showing Bones, Tendons,
Ligaments, etc.�i. Radius. 2. Skin. 3 and 6. Sheath of extensor pedis tendon. 4. Annular band of deep fascia. 5. Anteiior
common ligament of knee. 7. Tendon of extensor pedis. 8. Os magnum. 9. Synovial bursa. 10. Large metacarpal bone.
"' Anterior common ligament of fetlock. 12. Synovial bursa. 13. Tendon of extensor pedis. 14. Os suffraginis. 15. Os corome.
16. Pyramidal process. 17. Os pedis. 18. Skin. 19. Tendon of flexor perforatus. 20. Tendon of flexor perforans. 21. Tendon of flexor
metacarpi medius. 22. Pisiform bone. 23. Semilunar bone. 24. Carpal sheath. 25. Posterior common ligament of knee. 26 and
28. buspensory or superior sesamoidean ligament. 27. Subcarpal or check ligament. 29. Metacarpophalangeal or great sesamoidean
sheath. 30. Sesamoid bone. 31. Fibro-fatty tissue. 32. Deep division of inferior sesamoidean ligament. 33. Middle division of ditto.
34. Uuter half of ring formed by perforatus tendon for passage of perforans. 35. Superficial division of inferior sesamoidean ligament.
30. Complementary cartilage of pastern joint. 37. Perforatus tendon running to its insertion into OS suffraginis. 38. Tendon of flexor
pertorans. 39. Navicular bone. 40. Plantar cushion.

SUPERFICIAL DISSECTIONS

OUTER ASPECT OF LIMB
Such a dissection is represented in Plates IV. and V., and the
structures exposed are as follows :

Near the upper end of the limb, the spine of the scapula (2)
is seen running obliquely downwards and forwards. Towards its
middle it shows the prominence called the tubercle of the spine (4),
which g_lVes attachment to the trapezius muscle. This muscle has
been dissected away to expose the muscles lying beneath it. The
summit or anterior portion of the outer tuberosity of the humerus
(12) is visible, and to it the outer tendon of the supraspinatus
muscle (6) is attached. Extending downwards and backwards from
the summit is the deltoid ridge (13), which terminates inferiorly
in the well-marked deltoid tubercle. The ridge is partially concealed
by the insertion of the infraspinatus muscle (5).

Taking an oblique course downwards and backwards along the
line of direction of the deltoid ridge, we arrive at the summit of
the olecranon process of the ulna, which forms a marked and well-
defined prominence (19).

The bones of the forearm are almost completely clothed by the
extensor and flexor muscles of the metacarpus and digit. The

Plate IX.�Transverse Section of "Near" Forearm, Two Inches below the Seat of
Median Neurectomy.� I. Extensor metacarpi magnus. 2. Extensor pedis. 3. Anterior radial
artery. 4. Musculo-spiral nerve. 5. Anterior radial vein. 6. Interosseous vein of forearm. 7. Internal
subcutaneous vein of forearm. 8. Interosseous artery of forearm. 9. Radius. 10. Extensor suffraginis.
11. Median nerve. 12. Flexor metacarpi externus. 13. Posterior radial vein. 14. Ulnar nerve.
15. Posterior radial artery. 16. Ulnar vein. 17 and 19. Posterior radial veins. 18. Ulnar artery.
20. Flexor metacarpi internus. 21. Ulna. The muscular mass between the internal and external flexors
of the metacarpus is formed by the flexor metacarpi medius and the superficial and deep flexors of
the digit (see descriptive text).

io THE SURGICAL ANATOMY OF THE HORSE

inferior extremity of the radius will, however, be found to be imme-
diately subcutaneous between the tendon of the extensor pedis (22)
and that of the extensor suffraginis (25).

Between the knee and fetlock almost the whole of the outer
surface of the external small metacarpal bone (32) is represented, as
is also the shaft of the large metacarpal, excepting that portion
which is concealed by the tendons of the extensor pedis and
extensor suffraginis muscles.

Below the fetlock we see the os suffraginis (46), the greater
part of the front and lateral aspect of this bone being visible,
together with the external prominence at its lower extremity.

Only two ligaments are shown in the plates representing this
aspect of the limb.

The Superior Sesamoidean or Great Suspensory Ligament (44).�This
first makes its appearance about four inches below the knee. It is
visible owing to the body of the outer splint bone having become
so much thinner than it is above this point.

The ligament runs down the limb in the channel formed by the
large and two small metacarpal bones. Just above the fetlock it
splits into two parts. The outer division is plainly represented (44).
It runs round the outer lateral aspect of the fetlock, and gives off
a slip of insertion to the sesamoid bone of its side. It then runs
obliquely downwards and forwards across the shaft of the first
phalanx to the front of the limb, where it terminates by uniting
with the tendon of the extensor pedis.

The Subcarpal or Check Ligament.�This is placed behind the
suspensory ligament just below the knee. Like the former ligament,
its upper portion is concealed by the greater thickness of the upper
extremity of the small metacarpal bone. It is the downward con-

Plate X.�Transverse Section Across Left Metacarpus

I. Internal dorsal interosseous artery. 2. Tendon of extensor pedis. 3. Internal small
metacarpal bone. 4. Tendon of extensor suffraginis. 5. Internal palmar interosseous
artery. 6. Large metacarpal bone. 7. Deep metacarpal vein. 8. External dorsal inter-
osseous artery. 9. Internal metacarpal vein. 10. External small metacarpal bone.

II. Large metacarpal artery. 12. External palmar interosseous artery. 13. Internal plantar
nerve. 14. Suspensory ligament. 15. Tendon of flexor perforans. 16. External metacarpal
vein. 17. Tendon of flexor perforatus. 18. Small unnamed artery descending from sub-
carpal arch. 19. Communicating bianch between internal and external plantar nerves.
20. External plantar nerve.

SUPERFICIAL DISSECTIONS

tinuation of the posterior common ligament of the knee, and becomes
united to the tendon of the flexor perforans about three and a half
inches below the carpus. Along its outer edge is seen to run the
external metacarpal vein (32).

The Muscles and Tendons

The Supraspinous Muscle (6).�This occupies the whole of the

fossa in front of, or above the spine of the scapula, which bears the

same name. Its outer tendon of insertion, which is attached to the

summit of the external tuberosity of the humerus, is represented in

^e Pl^ate (12). The muscle is a powerful extensor of the shoulder

joint, and is supplied by the suprascapular nerve.

The Infraspinatus Muscle (5).�Occupies almost the whole of the

m raspmous fossa. The outer surface of the muscle presents a

F - ion which runs obliquely downwards and forwards, and

is somewhat deceptive in suggesting the possession of two
bellies.

^1S inserted by an inner tendon into the convexity of the

external tuberosity of the humerus and by an outer broad tendon (8),

which is represented in the plate, into the upper portion of the

eltoid ridge. This muscle is an abductor and outward rotator of

tne humerus, and is supplied by the suprascapular nerve.

The Deltoid Muscle (9).�This muscle is also traversed obliquely
downwards and forwards by a depression in which the scapular fascia
dips. It arises from the dorsal angle and part of the posterior
border of the scapula, and also from the scapular fascia. It is
inserted into the deltoid tubercle. Its action is similar to that of
the infraspinatus, and it is supplied by the circumflex nerve.

The Biceps (16).�In front of the upper half of the humerus we
find the biceps muscle, which is seen to arise from the coracoid
process. Its tendon passes through the bicipital groove between the

Plate XI.�Transverse Section Across Fetlock of " Near " Fore Limb

l. Skin. 2. Subcutaneous fascia. 3. Tendon of extensor pedis. 4. Anterior common
ligament of fetlock. 5. Tendon of extensor suffraginis. 6. Lateral ligament of fetlock.
7. Large metacarpal bone. 8. Inner sesamoid bone. 9. Outer division of suspensory
ligament. 10. Intersesamoidean ligament. 11. Outer sesamoid bone. 13. Tendon of flexor
perforans muscle. 13. Fibro-cartilage. 14. Anterior division of plantar nerve (anterior
digital nerve). 15. External digital vein. 16. Internal plantar nerve. 17. External digital
artery. 18. Sheath of flexor tendons. 19. Tendon of flexor perforatus muscle. 20. Fibro-
fatty tissue.

12 THE SURGICAL ANATOMY OF THE HORSE

tendons of insertion of the supraspinatus muscle. The biceps is
inserted into the bicipital tuberosity of the radius.

The upper part of the biceps is visible owing to the fact that
the mastoido-humeralis has been almost completely removed. Two
or three inches of the last-named muscle are, however, represented
near its insertion into the external lip of the musculo-spiral
groove (18).

Behind this piece of the mastoido-humeralis is noticed part of the
Brachialis Amicus Muscle (17), which arises at the back, of the upper
extremity of the humerus. It then winds round the outer side of the
bone in the musculo-spiral groove, where it is represented in the plate
(17). Its tendon of insertion, which is not visible, passes inwards
beneath the internal lateral ligament of the elbow to be inserted into
the radius and ulna.

The Triceps Extensor Cubiti.�-Two divisions of this muscle are repre-
sented here, namely, the large and middle heads (7 and 1 5).

The Caput Magnum (7) arises from the dorsal angle and glenoid edge
of the scapula, and is inserted into the summit of the olecranon process
of the ulna. This muscle fills up the greater part of the triangle of
which the scapula (inferior border) and humerus form two of the sides.
It is a powerful extensor of the elbow and a flexor of the shoulder.

The Caput Medium (15).�This division arises from the curved
roughened line which runs upwards on the back of the humerus from
the deltoid tubercle to the articular head. The upper part of the origin
of the muscle is concealed by the deltoid. It is inserted with the large
head, and is an extensor of the elbow.

Both these divisions of the triceps extensor cubiti are supplied by the
musculo-spiral nerve.

In the region of the forearm quite a number of muscles are repre-
sented.

The Extensor Metacarpi Magnus (20).�This is the most anterior of
the muscles here shown. Its belly, together with that of the extensor

Plate XII.�The Scapula

A. �INNER OR VENTRAL ASPECT

I. Cervical angle. 2. Vertebral edge. 3. Roughened area for attachment of lavator anguli
scapula and serratus magnus. 4. Dorsal angle. 5. Coracoid edge. 6. Roughened area for
attachment of serratus magnus. 7. Subscapular fossa. 8. Glenoid edge. 9. Coracoid process.
10. Glenoid cavity. 11. Tubercle for attachment of tendon of coraco-humeralis.

B. � OUTER OR DORSAL ASPECT

X. Vertebral edge. 2. Cervical angle. 3. Dorsal angle. 4. Fossa for supraspinatus muscle.
5- Fossa for infraspinatus muscle. 6. Tubercle of spine. 7. Ridges for attachment of teres
minor. 8. Spine. 9. Glenoid edge. 10. Coracoid process. 11. Glenoid cavity.

SUPERFICIAL DISSECTIONS 13

pedis, forms the bulging mass in front of the forearm, which is so
distinctly visible in the living animal.

It arises from the roughened ridge above the external condyle of the
humerus, and its muscular portion gradually tapers as we descend to
within two or three inches of the knee, where it is succeeded by a
tendon. The latter passes under the extensor metacarpi obliquus and
through the middle groove on the front of the lower extremity of the
radius. It next crosses the knee in a vertical direction, where it lies on
the anterior common ligament, and runs to its insertion into a roughened
area at the front of the upper extremity of the large metacarpal bone.
This muscle is the principal extensor of the knee joint, and its nerve
supply is derived from the musculo-spiral.

The Extensor Pedis (22).�This is placed behind the extensor meta-
carpi magnus. It arises from the small depression which is placed to the
outer side of the coronoid fossa, from the external lateral ligament of the
elbow and from the upper portion of the outer aspect of the radius.

Its muscular portion tapers at both ends, and inferiorlyit is succeeded
by a tendon which plays over the broad origin of the extensor metacarpi
obliquus. It next passes through the outer of the two vertical grooves
on the front of the radius, and crosses the knee under the annular band
of fascia, being superficially placed to the anterior common ligament.

The tendon is divisible into two portions�the outer and smaller of
which joins the tendon of the extensor sufTraginis. The inner and larger
tendon plays over the fetlock and pastern joints and takes the place of an
anterior common ligament of the latter, the synovial membrane of the
pastern joint being supported by the posterior face of the tendon. The
tendon then receives the two divisions of the suspensory ligament, and
becomes inserted into the pyramidal process of the pedal bone. This
muscle extends the knee, fetlock, and inter-phalangeal joints, and is
supplied by the musculo-spiral nerve.

The Extensor Sujraginis (25).�This is a small muscle which is placed
between the extensor pedis in front and the flexor metacarpi externus

Plate XIII.�The Humerus

A.�LEFT HUMERUS, ANTERIOR ASPECT

ancfi^nten°^r ^dlVisi°^no( ^internal tuberosity. 2. Bicipital groove. 3. Internal tubercle (for attachment of teres major

artic ^^tlSS""^US ^d°^rS1>' ⁴' ^RicIS^es ^for attachment of coraco-hunieralis muscle. 5. Coronoid fossa. 6 and 7. Inferior

■ surface. 8. Pit for origin of extensor metacarpi miignus and extensor pedis. 9. Musculo-spiral groove.

� 1 ge for attachment of mastoido-humeralis. n. Deltoid tubercle. 12. Deltoid ridge. 13. Anterior division

isummit) of external tuberosity. 14. Mesial ridge of bicipital groove.

B.�LEFT HUMERUS, POSTERIOR ASPECT

5. Surface for
7. Roughened

ar*i ?^VeXlt> °^f ^external tuberosity. 2. Deltoid ridge. 3. Deltoid tubercle. 4. External condyle.

n_r,L, r * '°ⁿ ^WUh ^s'S^moid cavity of ulna. 6. Pit for attachment of external lateral ligament of elbow

cLiLci lor origin of f\r*

flexor perfor metacarpi externus. 8. Roughened area for origin of flexor perfoi atus and humeral head of

13- Rouble ^T' ⁹ ^OIecranon ^fossa- ^I0- Internal condyle. n. Internal tubercle. 12. Musculo-spiral groove.

iec ridge for attachment of caput medium. 14. Articular head. 15. Posterior division of internal tuberosity.

H THE SURGICAL ANATOMY OF THE HORSE

behind. It arises from the external lateral ligament of the elbow, from
the outer side of the upper end and outer border of the radius, and from
the line of junction of the radius and ulna.

Its thin muscular portion is followed by a tendon which plays
through the vertical groove on the outer aspect of the inferior extremity
of the radius. It then crosses the outer side of the knee, passing
through a synovial sheath. From the fibrous arch of the knee it
receives a reinforcing band, and is joined by the portion of the tendon
of the extensor pedis already referred to. It runs down the limb parallel
to the extensor pedis, and is inserted into the upper extremity of the
anterior face of the os suffraginis.

This muscle extends the knee and fetlock, and is also supplied by the
musculo-spiral nerve.

The 'Extensor Metacarpi Obliquus (24).�-This is a small muscle which
arises from the inferior portion of the outer aspect of the radius. At
its origin the muscle is broad and flat, and it is here crossed by the
extensor pedis.

Its tendon plays over that of the extensor metacarpi magnus, passes
through the oblique groove at the inferior extremity of the radius, and
runs downwards and inwards to be inserted into the head of the inner
small metacarpal bone.

Its action is similar to that of extensor metacarpi magnus,
and like the latter muscle it is supplied by the musculo-spiral
nerve.

The Flexor Metacarpi Externus (21).�This muscle is placed behind
the extensor suffraginis, and arises from the outer condyle of the
humerus. Its muscular portion is succeeded by a thick powerful
tendon, which splits into two divisions. One of these is inserted into
the upper border of the pisiform bone together with the tendon or
insertion of the middle flexor, and the other plays through the groove
on the outer aspect of the pisiform bone and is inserted into the head of
the outer small metacarpal bone.

Plate XIV.�Left Radius and Ulna

A.�ANTERIOR ASPECT



		ILLUSTRATIONS

			COLOURED PLATES

	IV. Superficial Dissection of Fore Limb, Outer Aspect . V. Superficial Dissection of Fore Limb, Outer Aspect (continued') VI. Superficial Dissection of Fore Limb, Inner Aspect VII. Superficial Dissection of Fore Limb, Inner Aspect (continued) VIII. Longitudinal Section...... IX. Transverse Section just below Seat of Median Neurectomy XXI. Transverse Section across Knee ..... ⁵XXX. Seat of Median Neurectomy Dissected ....

HALF-TONE PLATES I. Outer Aspect of Shoulder and Arm II. Right Fore Limb. Outer Aspect III. Inner Aspect of Right Fore Limb X. Transverse Section across Left Metacarpus XI. Transverse Section across Fetlock of Left Fore Limb XII. The Scapula XIII. The Humerus XIV. Left Radius and Ulna XV. Left Radius and Ulna XVI. Carpal and Metacarpal Bones XVII. Os Suffraginis and Os Corona XVIII. Long and Short Pastern Bones (showing Exostoses) This Plate has been placed so, in order that it may be near the text to which it relates.



			/ -

		Plate XVII.�Os Suffraginis and Os Coron^e The os suffraginis showing exostoses (so-called false ringbones) at the attachments of the lateral ligaments of (1) the fetlock, and (2) the pastern.
	� Anterior surface of la^nfenor articular surfac f « T^ea ^f°^r ^attachmente lock. 4. Anterior surface

7- Areas for attachment of lateral ligaments of Pastern. 6. Anterior surface of coronas. 8. Area tor attachment of lateral ligaments of pedal joint. 9- Inferior articular surface of coronje.



	THE SMALL METACARPAL BONES
	THE SMALL METACARPAL BONES	57
		57

THE SMALL METACARPAL BONES These are long bones, the development of which has been aborted. Each consists of a body and a head. The body is a long tapering rod of bone, which presents three surfaces. It is curved in its length. The anterior surface is flattened, and for the greater part is roughened for the attachment of the interosseous ligament which unites this bone to the large metacarpal. For about an inch and a half above the lower extremity this surface is smooth and free, and the small and large meta- carpals are here separated from one another by a slight interval. The inner surface is the least extensive. It bounds outwardly the channel which accommodates the suspensory ligament. This surface is widest at its upper extremity, and becomes gradually narrower as we descend to the inferior extremity of the bone. The outer surface is slightly curved in its length, with the concavity of the curve directed outwards. It is convex in the transverse direction, and is smooth. The head of the bone is placed superiorly, and its upper surface is articular, that of the inner bone presenting two facets, whilst on the outer we have only one. The larger of the two facets on the inner bone is for articulation with the trapezoid, and the smaller for the magnum. The facet on the outer bone is for articulation with the unciform bone. Anteriorly, the head of each small metacarpal bone presents two small, somewhat flattened facets, for articulation with like facets at the back of the upper extremity of the large metacarpal, with which they form synovial joints. Outwardly each head is roughened for the attachment of muscles and ligaments. Each of the small metacarpal bones terminates inferiorly in a small rounded nodular enlargement, which may be readily located in the living animal. This enlargement is frequently termed the " button " of the splint bone, and its position is the more easily detected on account of H



	SPLINTS
	SPLINTS	61

the vertical movements of the inner splint-bone are exaggerated, and the interosseous ligament being thus damaged, subsequently becomes inflamed. The outer interosseous ligament is immune from similar injury, since the unciform does not rest entirely upon the head of the outer small meta- carpal, but articulates also with the large metacarpal, over which the concussion therefore on this side of the limb is distributed, and there is no abnormal tension of the interosseous ligament. This is Havemann's theory, and it is in accordance with the much more frequent occurrence of splints on the inner than on the outer aspect of the limb. Dieckerhoff maintained that splints were due to tension of the fascia of the forearm. This fascia is attached to the periosteum of the metacarpal bones, and during certain movements of the limb the fascia is made very tense, with the result that considerable traction is exerted on the periosteum, leading ultimately, in Dieckerhoff's opinion, to splint formation. Splints have also been attributed to breeding with " weedy " sires or splint-affected dams. Heredity may possibly have some influence on the causation of this affection, but there is little doubt that in the majority of cases splints are due to constant concussion when the animal is worked whilst immature on a hard road or pavement. Occasionally the cause is a blow. Macqueen defines the condition as a bony enlargement which is the result of periostitis and ostitis. An animal affected with splints moves stiffly, the action of the fore- limbs being cramped, confined, and stilty. In some respects the action resembles that of an animal affected with navicular disease. The condition is, however, easily distinguished from navicular disease, since splint lameness is accentuated with exercise, whilst in navicular disease lameness is diminished. Diagnosis should be completed by manipulation. This presents most difficulty when the splint is placed posteriorly, or is very small. Splints on the outer aspect of the limb are sometimes associated with



	THE FIRST PHALANX
	THE FIRST PHALANX	67
		67

THE FIRST PHALANX This bone is frequently referred to as the os suffraginis, and com- monly also as the long pastern bone. It extends obliquely downwards and forwards from the fetlock joint above to the pastern joint below. It belongs to the class of long bones, and possesses a diaphysis and two epiphyses. The anterior surface of the shaft is smooth and slightly convex in the transverse direction. The posterior surface is almost flat. It presents a V-shaped, roughened area which gives attachment to the vertical and two oblique strands of the middle division of the inferior sesamoidean ligament. Near its upper extremity this surface also presents a roughened area on either side. These areas are for the attachment of the crossed bands of the deep division of the inferior sesamoidean ligament. The lateral surfaces are convex in the transverse direction and concave longitudinally. They blend with the anterior surface. Each presents about midway down the shaft a transverse groove for the accommoda- tion of the perpendicular artery of the pastern. Near its upper extremity each of these surfaces presents a " buttress-like " tubercle, which is roughened for the attachment of the lateral ligament of the fetlock and the lateral sesamoidean ligament. At its inferior extremity the lateral surface presents a shallow depression, above which is a tubercle. From the tubercle a ridge extends upwards and terminates about midway up the shaft of the bone. The depression, tubercle, and ridge are roughened for the attachment of the lateral ligament of the pastern joint. The superior surface of the bone is articular and is moulded on to the inferior surface of the large metacarpal. Consequently it presents two shallow depressions separated by a deep antero-posterior groove.



		PREFACE TO PART II Owing to the greater surgical importance of the limbs in veterinary practice, consecutive treatment has been dealt with a little more fully in this volume than in Part I., otherwise precisely similar lines have been followed. To the Vice-Chancellor of the University of Liverpool the author desires again to express his gratitude for the ever-ready advice and kindly help, of which it has been the author's good fortune to avail himself. The onerous task of revising and correcting the proofs has been kindly undertaken by the author's friend and former colleague, Professor Macqueen, many of whose views upon matters appertaining to the purely surgical part of the work have been adopted. Although these have been frequently acknowledged throughout this volume and were referred to in the General Preface to Part I., the author feels it his duty to make reference to them here, for to have had the collaboration of one with the ripe experience of Professor Macqueen cannot fail to add materially to the practical value of the work. The kind reception accorded the first volume by the majority of the critics and by practitioners generally in this country, and especially by his fellow veterinarians in France and America has been most gratifying to the author, and has convinced him that his opinion of the necessity which existed for a work of the kind, as expressed in the Preface to Part I., was well founded. It was pointedly remarked by one esteemed reviewer, presumably a member of our sister profession, that "since 1832. when William



		PREFACE
	vi


Percival produced the first work exclusively devoted to the anatomy of the horse, considerable advances have been made in the methods of teaching veterinary anatomy ; but it cannot be said that the production of anatomical literature has been correspondingly abundant in this country. The veterinarian has not had his time too heavily taxed by the examination of frequent new publications." The justice of this soft impeachment is best known to the members of the veterinary profession, and the intended mission of the writer will therefore be amply fulfilled if the effort be considered by his fellow workers to be a useful contribution to this unfortunately too inadequate supply of veterinary literature. To the judgment of practitioners, who are best qualified to know their own wants, and at whose hands the first part of this work was so charitably received, without further remark this volume is now committed. Department of Veterinary Anatomy, The University of Liverpool. June 1907.



		CONTENTS PART II�-THE FORE LIMB CHAP. PAGE I. SUPERFICIAL EXAMINATION........ i II. SUPERFICIAL DISSECTIONS........ 9 III. THE LIMB IN SECTION......... 31 IV. THE BONES�FRACTURES AND EXOSTOSES . . . .40 V. THE JOINTS............ 72 VI. THE TENDONS, LIGAMENTS, TENDON SHEATHS, AND BURS.E............ 117 VII. THE NERVES............ 138 VIII. THE BLOOD AND LYMPH VESSELS....... 167 MUSCLES OF FORE LIMB......... 186



		x ILLUSTRATIONS facing plate page XIX. The Scapulo-Humeral Articulation (Outer Aspect) ... 74 XX. The Elbow Joint (Outer Aspect)�The Bones ..... 80 XXII. Tendons Playing over Front of Knee ...... 88 XXIII. Cherry's Operation (Slightly Modified)...... 98 XXIV. Transverse Section of Pastern Joint showing Articular Surfaces, Ligaments, Tendons and Complementary Cartilage . . .112 XXV. Outer Aspect of Right Knee showing Distended Sheaths (Semi- Schematic) ........... 120 XXVI. A.�The Subcarpal Ligament. B.�Seat of Tenotomy of the Flexors of the Digit, etc. . . . . . . . .130 XXVII. Right Fore Limb. Outer Aspect showing Sheaths at Fetlock. . 132 XXVIII. The Sesamoidean Ligaments ........ 136 XXIX. A �First Rib of Left Side�Outer Aspect. B.�First Rib of Left Side�Inner Aspect. C.�First Rib of Left Side�Showing Seat of Fracture "A" . . . . . . . . . 148 XXXI. Seat of Ulnar Neurectomy with Ulnar Nerve Exposed . . 152 XXXII. Seat of Ulnar Neurectomy�the Seat in Section . . . 154 XXXIII. A. �A Common Seat of " Speedy-Cutting." B.�Seat of Internal Plantar Neurectomy. C�Seat of Digital Neurectomy. D.�Seat of Internal Plantar Neurectomy in Section . .164 XXXIV. The Carpal Arterial Arches and the Veins of the Fore Limb . 176



			ERRATA

		Page 3, line 15, for "liable " read "likely." � 4, � 15, insert "external" after "splints." � 6, fourth line from bottom,for "plantar nerve" read " digital artery." � 20, line 16, after " elbow " add "and extensor of shoulder. � 28 (facing), for " Plate VI " read " Plate VII." � 32, line 13, for " attachment " read "attachments." � 51, � 1, for "solar " read " plantar." � 122, line 11 delete " further " Plate XXI, 12, delete "internal."



		THE FORE LIMB CHAPTER I SUPERFICIAL EXAMINATION The student should first examine the outer aspect of the region of the shoulder, and endeavour as near as possible to locate the outline of the scapula. Having done this, it will be observed that running obliquely downwards and forwards over the area enclosed by the imaginary outline drawn, there are four elevations, which are formed by the following muscles : The most superior or anterior elevation indicates the position of the supraspinatus muscle, which lies in the supraspinous fossa and is attached inferiorly to the anterior divisions of both tuberosities at the proximal end of the humerus. Between the two tendons of insertion of this muscle the tendon of origin of the biceps emerges. The second elevation is formed by the infraspinatus muscle. This muscle has two tendons of insertion also, one of which is attached to the inner side of the convexity (i.e., the more posterior of the two divisions of the external tuberosity), whilst the other tendon plays over the outer aspect of the convexity and is inserted into the upper extremity of the deltoid ridge. A small synovial bursa is placed between this tendon and the outer surface of the convexity. Between the two muscles named, the tubercle of the spine of the scapula may be easily located. It is important to note that the tendons of the supraspinatus and infraspinatus muscles by their disposition materially assist in keeping the head of the humerus in A



		2 THE SURGICAL ANATOMY OF THE HORSE the glenoid cavity of the scapula. These muscles are affected in supra- scapular paralysis, and it will be seen that when this affection has advanced to such a degree that the muscles become atrophied, the long axes of the muscles and their tendons become considerably increased in length on account of the diminution in width of the bellies. This increased length causes a relaxation of the parts, with the result that we have one of the diagnostic symptoms of suprascapular paralysis, viz., free external rotation of the head or the humerus. Internal rotation is prevented by the tendon of the subscapularis muscle, which is not affected in this paralysis. The two posterior elevations are formed by the underlying deltoid muscle, which arises from the posterior border of the scapula and is inserted into the deltoid tubercle of the humerus. The appearance of two elevations is due to a false septum in the muscle caused by a dipping inwards of the scapular fascia which binds this muscle to the preceding one and to the underlying bone. The point of the shoulder is formed by the coracoid process of the scapula. This should be carefully palpated, since it is a common seat of fracture, particularly in young animals, the fracture being usually due to the shoulder being caught in a doorway or narrow gateway. Running over the shoulder joint and spreading out as it descends is the mastoido- humeralis muscle. Inferiorly to the shoulder this muscle again becomes narrower, and runs to its insertion into the outer lip of the musculo-spiral groove. Near the upper border of the mastoido-humeralis and just in front of the point of the shoulder is the common seat of " shoulder tumour " or " abscess." The long axis of the scapula runs downwards and forwards, and meets the long axis of the humerus, which runs downwards and backwards forming an acute angle at the shoulder joint. The triangle, of which these two bones form the antero-superior and antero-inferior sides, is filled by a large muscular mass which is indicated on the exterior by a well-marked convex bulging of distinct outline. This mass is formed by the triceps extensor cubiti or caput muscles, which are inserted into



		Plate II.�Right Fore Limb. Outer Aspect i. Position of elbow articulation. 3. Flexor metacarpi externus. 3. Elevation caused by pisiform bone. 4. External small metacarpal bone. 5. Edge of tendon of flexor perforans. 6. Level of bases of sesamoid bones. 7. Situation of pastern joint. 8. Os suffraginis. 9. Position of fetlock articulation. 10. Large metacarpal bone. 11. Edge of radius. 13. Elevation formed by belly of extensor pedis. 13. Elevation formed by belly of extensor metacarpi magnus.



		SUPERFICIAL EXAMINATION 3 the summit of the olecranon process, and are the great extensors of the elbow. The marked convexity of these muscles should be observed, since in advanced cases of radial paralysis or " dropped elbow," in place of the convexity we have a marked depression, due to the fact that these muscles have become atrophied. What is commonly known as the " point " of the elbow corresponds to the position of the summit of the olecranon process of the ulna. The elbow joint is placed from three to four inches downwards and forwards from this point, varying, of course, according to the size of the animal, and is indicated externally by a slight depression. It will be observed that there is an almost entire absence of muscular tissue en the outer aspect of the joint, which is here therefore very badly protected, a fact which renders it necessary to treat wounds in the neighbourhood of the joint with great care ; otherwise an open arthritis of the joint is a very liable complication. Passing the hand down the front of the forearm, a very prominent and well-defined elevation is felt. This raised surface corresponds to the bellies of two muscles, the more anterior of which is the extensor meta- carpi magnus, whilst the other is the extensor pedis. Behind the extensor pedis is placed the flexor metacarpi externus muscle, which is indicated externally by a slight and elongated elevation. Between these two muscles is situate the extensor sufFraginis muscle, which does not provide any superficial marking, since it is wedged in somewhat tightly between the two muscles named. The tendons of the extensor pedis and extensor metacarpi magnus run over the front of the knee after having passed through the two vertical grooves on the anterior aspect of the inferior extremity of the radius, whilst that of the extensor sufFra- ginis passes through a groove on the outer side of the inferior extremity of this bone. The tendon of the flexor metacarpi externus will be found to terminate just above the knee and on its postero-external aspect, where we feel a well-marked, hard ridge. This ridge corresponds to the upper border of the pisiform bone, and it should be remarked that this edge of



		4 THE SURGICAL ANATOMY OF THE HORSE the pisiform is almost immediately subcutaneous�a point which is of considerable surgical importance in dealing with affections of the knee which require tight bandaging for any considerable length of time. In such cases the pressure of the bandage should be taken off the edge of the pisiform bone by applying a roll of cotton wool or tow on either side ; otherwise the continuous pressure on the skin over the sharp edge of the bone will lead to a serious complication in the form of the bone making its appearance through the skin. The outermost bones of the two rows of the carpus, namely the cuneiform and the unciform, should next be felt, and below the unciform the head of the outer small metacarpal or " splint " bone will be detected, from which without any difficulty the finger may be passed along the groove which corresponds to the line of apposition of the large and outer small metacarpal bones. This groove indicates the most common situa- tion of splints, and particular familiarity should be made with it imme- diately below the knee, for here we find what are known as " knee splints," which are the most troublesome form of this affection. Between the knee and the fetlock it will be found that the anterior aspect of the large metacarpal bone is immediately subcutaneous, but towards the outer side of this aspect the tendon of the extensor pedis muscle may be easily felt, and externally to that again the tendon of the extensor suffraginis muscle. At a point which is distant from two and a half to three and a half inches below the knee and immediately behind the small metacarpal bone there will be felt a slight thickening, which indicates the position where the subcarpal or check ligament unites with the tendon of the deep flexor of the digit, and which thickening must not be mistaken for fibrous enlargement due to a chronic sprain of the tendon. By taking up the foot and flexing the knee, the edge of the ligament becomes much more evident to the touch. The next step is carefully to manipulate the skin over the back tendons, namely, those of the flexor perforatus and flexor perforans



	Plate IV.�SUPERFICIAL DISSECTION. Fore Limb (right), Outer aspect.�I. Cartilage of prolongation. 2. Spine of scapula. 3. Dorsal angle scapula. 4. Tubercle of spine. 5. Infraspinatus muscle. 6. Supraspinatus. 7. Caput magnum. 8. Tendon infraspinatus. 9. Deltoid muscle. 10. Outer tendon of supraspinatus. II. Insertion of deltoid. 12. Anterior ^'vision °[ external tuberosity of humerus [i.e., the summit). 13. Upper portion of deltoid ridge. 14. Tendon of j'^lg'ⁿ ^of biceps. 15. Caput medium. 16. Biceps muscle. 17. Brachialis anticus. 18. Insertion of mastoido-humeralis.
				metacarpi magnus.

21 i^⁸⁶¹¹"¹⁰¹¹ °f caput muscles into summit of olecran � r lexor metacarpi externus. 22. Extensor pedis.		process Ulnar accessorius.	na. 20. Extensor



		SUPERFICIAL EXAMINATION 5 muscles. These tendons should be felt as far as possible throughout their length, beginning at the knee, immediately below which they will be found at the spot where they leave the carpal arch. Just above the fetlock the tendon of the deep flexor will be found to disappear, for it here enters the fibrous ring formed for its passage by the perforatus tendon. The perforans, however, will be felt to make its reappearance just below the joint, where it emerges from the fibrous tube mentioned. Careful manipulation of the outer side 01 the fetlock will reveal the presence of a hard, flat band which runs downwards and forwards to the anterior aspect of the limb, where it joins the tendon of the extensor pedis muscle. This band is the external division of the suspensory ligament, which has divided just above the fetlock after traversing the channel formed by the large and two small metacarpal bones. This slip of the suspensory ligament will be found to broaden out and to become much less apparent to the touch as we descend to its insertion. It is sometimes ruptured, particularly in young animals. Near where the suspensory ligament divides the small metacarpal bone will be found to terminate in a small rounded nodule. This is known as the " button" or the splint bone, and must not be mistaken for a splint. The upper part of the inner aspect of the limb is best examined on a dead specimen. The limb should be disarticulated at the shoulder joint, and the inner cutaneous incision should be made as high up as possible in the armpit. The first point we notice is the curve indicating the inferior border of the posterior superficial pectoral muscle. This in most animals may be distinctly seen, but in all it may be easily felt. Extending vertically, and almost in the middle line of this aspect, will be felt an osseous ridge. This is the inner edge of the radius. Behind this ridge is a vertical groove, and posterior to the groove again we have a vertically elongated elevation which corresponds to the position of the belly of the flexor rnetacarpi internus muscle.



		6 THE SURGICAL ANATOMY OF THE HORSE Just above the lower edge of the posterior superficial pectoral muscle and in a line with the ridge of the radius, if a little pressure be applied, the posterior radial artery may be located in the living subject by its pulsation, which may be more easily felt if the limb be drawn a little forward. This is a very popular seat for the taking of the pulse. It is also the seat of neurectomy of the median nerve, which will be referred to later. Anterior to the ridge of the radius we see the inner aspect of the elevation formed by the extensor metacarpi magnus, to which reference has already been made. In the inferior third of the fore- arm we have the " chesnut," a horny excrescence which upon manipulation will be found to be confined to the skin. The inner surface of the scaphoid and trapezoid, the innermost bones of the two rows of the carpus, should now be felt, and the faint depression between them noted. Below the knee the tendons of the perforatus and perforans make their appearance, and may be felt as they are leaving the carpal arch. It is scarcely necessary here to impress the student with the importance of making himself quite familiar with these tendons, particularly where the check ligament joins the perforans, again immediately above the fetlock, and lastly just below this joint, where the perforans is leaving the ring formed by the perforatus, since at these situations the tendons are most commonly sprained. If the knee be flexed and the flexor tendons pushed aside, the suspensory ligament may be felt in the channel formed by the large and small metacarpal bones. By the application of pressure with the palmar aspect of the medius finger to the outer or inner side of the most prominent part of the fetlock, the plantar nerve may be rolled beneath the finger about half an inch posteriorly to the middle line. This should be practised, since it is of utility in deciding the seat of plantar neurectomy. The most prominent point at the back of the fetlock presents another horny



				SUPERFICIAL EXAMINATION 7 excrescence called the " ergot," surrounded by a tuft of long hairs. Subjacent to the skin and tendons in this position are the two sesamoid bones, the location of which may be decided by the fact that they move slightly towards the middle line upon the application of pressure to the outer surface of each with the thumb and finger. Immediately below the sesamoid bone on either side of the limb is a depression in which the edge of the perforans tendon may be felt, and which is the seat of inferior plantar, or more correctly digital, neurectomy. The region of the pastern should next be grasped with the hand, in order that the observer may familiarise himself with the conformation of the long pastern bone or os suffraginis. It will be found helpful if, whilst making this examination, the student has a dried bone near, in order that he may compare the buttress- like processes at the upper extremity of the bone with the elevations formed by them in the limb. The palmar aspect of the hand should be passed over this region several times, until the student has quite satisfied himself by comparison with the dried bone that these elevations are normal. The next point of importance is the position of the pastern joint, which will be found about an inch to an inch and a half above the line of junction of the skin and hoof. This joint is covered anteriorly by the flattened-out tendon of the extensor pedis. There is no anterior common ligament, so that the tendon is next the joint and gives support to the synovial membrane. Posteriorly the joint is well protected by the fibro-cartilaginous pad which projects upwards from the superior extremity of the back of the os coronas. According to Hunting's classification of ringbones, this joint is the seat of the class designated by the term "high," the " low ringbones " being those which affect the corono-pedal joint. The so-called false ringbones are placed on the sufFraginis or corona?, but do not affect the joints. By carefully manipulating the top of the hoof, the upper borders of the lateral cartilages will be felt. These cartilages, so far as they project above



		8 THE SURGICAL ANATOMY OF THE HORSE the hoof, should be traced out, and it should be noted that the greater part of the cartilage is placed within the hoof. If the foot be taken up in the living animal and the cartilages placed between the thumbs, the palmar aspect of the hands being applied to the wall of the hoof, a little pressure will distinctly reveal their elasticity.



		CHAPTER II SUPERFICIAL DISSECTIONS OUTER ASPECT OF LIMB Such a dissection is represented in Plates IV. and V., and the structures exposed are as follows : The Bones Near the upper end of the limb, the spine of the scapula (2) is seen running obliquely downwards and forwards. Towards its middle it shows the prominence called the tubercle of the spine (4), which g_lVes attachment to the trapezius muscle. This muscle has been dissected away to expose the muscles lying beneath it. The summit or anterior portion of the outer tuberosity of the humerus (12) is visible, and to it the outer tendon of the supraspinatus muscle (6) is attached. Extending downwards and backwards from the summit is the deltoid ridge (13), which terminates inferiorly in the well-marked deltoid tubercle. The ridge is partially concealed by the insertion of the infraspinatus muscle (5). Taking an oblique course downwards and backwards along the line of direction of the deltoid ridge, we arrive at the summit of the olecranon process of the ulna, which forms a marked and well- defined prominence (19). The bones of the forearm are almost completely clothed by the extensor and flexor muscles of the metacarpus and digit. The



		io THE SURGICAL ANATOMY OF THE HORSE inferior extremity of the radius will, however, be found to be imme- diately subcutaneous between the tendon of the extensor pedis (22) and that of the extensor suffraginis (25). Between the knee and fetlock almost the whole of the outer surface of the external small metacarpal bone (32) is represented, as is also the shaft of the large metacarpal, excepting that portion which is concealed by the tendons of the extensor pedis and extensor suffraginis muscles. Below the fetlock we see the os suffraginis (46), the greater part of the front and lateral aspect of this bone being visible, together with the external prominence at its lower extremity. The Ligaments Only two ligaments are shown in the plates representing this aspect of the limb. The Superior Sesamoidean or Great Suspensory Ligament (44).�This first makes its appearance about four inches below the knee. It is visible owing to the body of the outer splint bone having become so much thinner than it is above this point. The ligament runs down the limb in the channel formed by the large and two small metacarpal bones. Just above the fetlock it splits into two parts. The outer division is plainly represented (44). It runs round the outer lateral aspect of the fetlock, and gives off a slip of insertion to the sesamoid bone of its side. It then runs obliquely downwards and forwards across the shaft of the first phalanx to the front of the limb, where it terminates by uniting with the tendon of the extensor pedis. The Subcarpal or Check Ligament.�This is placed behind the suspensory ligament just below the knee. Like the former ligament, its upper portion is concealed by the greater thickness of the upper extremity of the small metacarpal bone. It is the downward con-



		12 THE SURGICAL ANATOMY OF THE HORSE tendons of insertion of the supraspinatus muscle. The biceps is inserted into the bicipital tuberosity of the radius. The upper part of the biceps is visible owing to the fact that the mastoido-humeralis has been almost completely removed. Two or three inches of the last-named muscle are, however, represented near its insertion into the external lip of the musculo-spiral groove (18). Behind this piece of the mastoido-humeralis is noticed part of the Brachialis Amicus Muscle (17), which arises at the back, of the upper extremity of the humerus. It then winds round the outer side of the bone in the musculo-spiral groove, where it is represented in the plate (17). Its tendon of insertion, which is not visible, passes inwards beneath the internal lateral ligament of the elbow to be inserted into the radius and ulna. The Triceps Extensor Cubiti.�-Two divisions of this muscle are repre- sented here, namely, the large and middle heads (7 and 1 5). The Caput Magnum (7) arises from the dorsal angle and glenoid edge of the scapula, and is inserted into the summit of the olecranon process of the ulna. This muscle fills up the greater part of the triangle of which the scapula (inferior border) and humerus form two of the sides. It is a powerful extensor of the elbow and a flexor of the shoulder. The Caput Medium (15).�This division arises from the curved roughened line which runs upwards on the back of the humerus from the deltoid tubercle to the articular head. The upper part of the origin of the muscle is concealed by the deltoid. It is inserted with the large head, and is an extensor of the elbow. Both these divisions of the triceps extensor cubiti are supplied by the musculo-spiral nerve. In the region of the forearm quite a number of muscles are repre- sented. The Extensor Metacarpi Magnus (20).�This is the most anterior of the muscles here shown. Its belly, together with that of the extensor



		A
		A	B
			B

	Plate XII.�The Scapula A. �INNER OR VENTRAL ASPECT I. Cervical angle. 2. Vertebral edge. 3. Roughened area for attachment of lavator anguli scapula and serratus magnus. 4. Dorsal angle. 5. Coracoid edge. 6. Roughened area for attachment of serratus magnus. 7. Subscapular fossa. 8. Glenoid edge. 9. Coracoid process. 10. Glenoid cavity. 11. Tubercle for attachment of tendon of coraco-humeralis.

B. � OUTER OR DORSAL ASPECT X. Vertebral edge. 2. Cervical angle. 3. Dorsal angle. 4. Fossa for supraspinatus muscle. 5- Fossa for infraspinatus muscle. 6. Tubercle of spine. 7. Ridges for attachment of teres minor. 8. Spine. 9. Glenoid edge. 10. Coracoid process. 11. Glenoid cavity.



		SUPERFICIAL DISSECTIONS 13 pedis, forms the bulging mass in front of the forearm, which is so distinctly visible in the living animal. It arises from the roughened ridge above the external condyle of the humerus, and its muscular portion gradually tapers as we descend to within two or three inches of the knee, where it is succeeded by a tendon. The latter passes under the extensor metacarpi obliquus and through the middle groove on the front of the lower extremity of the radius. It next crosses the knee in a vertical direction, where it lies on the anterior common ligament, and runs to its insertion into a roughened area at the front of the upper extremity of the large metacarpal bone. This muscle is the principal extensor of the knee joint, and its nerve supply is derived from the musculo-spiral. The Extensor Pedis (22).�This is placed behind the extensor meta- carpi magnus. It arises from the small depression which is placed to the outer side of the coronoid fossa, from the external lateral ligament of the elbow and from the upper portion of the outer aspect of the radius. Its muscular portion tapers at both ends, and inferiorlyit is succeeded by a tendon which plays over the broad origin of the extensor metacarpi obliquus. It next passes through the outer of the two vertical grooves on the front of the radius, and crosses the knee under the annular band of fascia, being superficially placed to the anterior common ligament. The tendon is divisible into two portions�the outer and smaller of which joins the tendon of the extensor sufTraginis. The inner and larger tendon plays over the fetlock and pastern joints and takes the place of an anterior common ligament of the latter, the synovial membrane of the pastern joint being supported by the posterior face of the tendon. The tendon then receives the two divisions of the suspensory ligament, and becomes inserted into the pyramidal process of the pedal bone. This muscle extends the knee, fetlock, and inter-phalangeal joints, and is supplied by the musculo-spiral nerve. The Extensor Sujraginis (25).�This is a small muscle which is placed between the extensor pedis in front and the flexor metacarpi externus



		H THE SURGICAL ANATOMY OF THE HORSE behind. It arises from the external lateral ligament of the elbow, from the outer side of the upper end and outer border of the radius, and from the line of junction of the radius and ulna. Its thin muscular portion is followed by a tendon which plays through the vertical groove on the outer aspect of the inferior extremity of the radius. It then crosses the outer side of the knee, passing through a synovial sheath. From the fibrous arch of the knee it receives a reinforcing band, and is joined by the portion of the tendon of the extensor pedis already referred to. It runs down the limb parallel to the extensor pedis, and is inserted into the upper extremity of the anterior face of the os suffraginis. This muscle extends the knee and fetlock, and is also supplied by the musculo-spiral nerve. The 'Extensor Metacarpi Obliquus (24).�-This is a small muscle which arises from the inferior portion of the outer aspect of the radius. At its origin the muscle is broad and flat, and it is here crossed by the extensor pedis. Its tendon plays over that of the extensor metacarpi magnus, passes through the oblique groove at the inferior extremity of the radius, and runs downwards and inwards to be inserted into the head of the inner small metacarpal bone. Its action is similar to that of extensor metacarpi magnus, and like the latter muscle it is supplied by the musculo-spiral nerve. The Flexor Metacarpi Externus (21).�This muscle is placed behind the extensor suffraginis, and arises from the outer condyle of the humerus. Its muscular portion is succeeded by a thick powerful tendon, which splits into two divisions. One of these is inserted into the upper border of the pisiform bone together with the tendon or insertion of the middle flexor, and the other plays through the groove on the outer aspect of the pisiform bone and is inserted into the head of the outer small metacarpal bone.



		Plate XIV.�Left Radius and Ulna A.�ANTERIOR ASPECT i. Beak of ulna. 2. Sigmoid cavity. 3. Coronoid process. 4. Bicipital tuberosity. 5. Anterior surface of shaft of radius. 6. Groove of tendon of extensor metacarpi magnus. 7. Groove for tendon of extensor pedis. 8. Groove for tendon of extensor metacarpi obliquus. B.�POSTERIOR ASPECT 1. Summit of olecranon process of ulna. 2. Inner surface of olecranon process. 3. Posterior order of olecranon process. 4. Radio-ulnar arch. 5. Body of ulna. 6. Posterior surface of aams. 7. Facet for cuneiform. 8. Facet for semilunar bone. 9. Facet for scaphoid.



			SUPERFICIAL DISSECTIONS i₅ As its name implies, this muscle is a flexor of the knee. Its nerve supply is derived from the musculo-spiral. The Ulnar Accessorius (23).�The origin of this muscle from the olecranon process of the ulna is seen. The muscle is placed between that just described and the flexor metacarpi medius. It disappears etween these two muscles and becomes more deeply seated where it joins the two remaining heads of the flexor perforans, to be followed by common tendon, which disappears through the carpal sheath. The endon will be described with the inner aspect of the limb. ^le Flexor Metacarpi Medius.�Only the posterior origin of this uscle which is attached to the olecranon process is represented in the p ate (the anterior head arises from the inner condyle of the humerus). °tn heads unite, and their common tendon is attached to the upper border of the pisiform bone. This muscle is a flexor of the knee, and is supplied by the ulnar nerve.

		The Arteries -No vessels appear in the plate representing the upper half of the ^rnD- Just above the knee joint the interosseous artery of the forearm (27) appears from beneath the extensor pedis muscle. It runs down the inib at first on the extensor metacarpi obliquus and then on the radius, ^eing ultimately distributed superficially on the front of the knee. Running along the edge of the perforans tendon is the outer of the ^w° small unnamed arteries (35), which descends from the subcarpal arch ^r°nt of the plantar nerve. It becomes lost towards the middle of the metacarpus. Ihe ^External Digital Artery (43).�This arises from the division pf tne large metacarpal artery just above the fetlock. It appears between ^tue suspensory ligament and perforans tendon, and runs vertically across ^tne fetlock between the plantar nerve behind and the external digital ^vein in front. It follows the course of the posterior digital nerve, and



			Plate XV.�Left Radius and Ulna

		A.�INNER ASPECT I- Summit of olecranon process. 2. Beak of nlna. 3. Slightly concave inner surface of olecranon. 4. Sigmoid cavity. 5- Body of ulna. 6. Superior articular surface of radius. 7. Radio-ulnar arch. 8. Bicipital tuberosity. 9. Roughened elevations for attachment of supra-carpal band of flexor perforatus. 10. Shaft of radius. 11. Roughened ridge for attachment of posterior common ligament of knee. 12. Groove for tendon of extensor metacarpi obliquus. 13. Facet for articulation with scaphoid. B�OUTER ASPECT i- Summit of olecranon process. 2. Beak of ulna. 3. Convex outer surface of olecranon. 4. Sigmoid cavity. 5. Roughened area for attachment of external arciform ligament. 6. Roughened area for attachment of external lateral ligament of elbow. 7. Radio-ulnar arch. 8. Bicipital tuberosity. 9. Body of ulna. 10. Shaft of radius. 11. Groove for passage of tendon of extensor suffraginis. 12. Groove for tendon of extensor pedis, 13, F'acet for pisiform bone. 14- Roughened area for attachment of external lateral ligament of knee. 15. Facet for cuneiform bone.



		16 THE SURGICAL ANATOMY OF THE HORSE disappears to the inner side of the lateral cartilage, where it divides into the preplantar and plantar (ungual) vessels. About the middle of the os sufFraginis it gives off the perpendicular artery of the pastern, which runs forwards at right angles to the parent vessel to be distributed on the lateral aspect of the first phalanx. The Veins The veins of the foot unite to form the plexuses of the foot. One of these plexuses is seen on the outer aspect of the lateral cartilage (48). From the plexuses the blood is drained by the internal and external digital veins. The latter is represented in the plate. It takes a course upwards in front of the digital artery across the fetlock, above which joint it disappears by dipping inwardly between the suspensory ligament and the perforans tendon. Here is formed a venous arch by the union of the external and internal digital veins. From this arch three veins are given off. One of these, the external metacarpal vein, is shown in the plate (32). It runs directly upwards in front of the plantar nerve and its accompanying artery. At the knee it splits up into a number of vessels, forming a plexus from which the ulnar vein and posterior radial veins (three or four) are given off. The Nerves The Ulnar Nerve.�This nerve emerges from beneath the posterior head of the flexor metacarpi medius. It runs on the back of the fore- arm on the tendon of the flexor accessorius and along the line of apposition of the middle and external flexors of the metacarpus. About four inches above the knee it disappears between the last two muscles, and joins the branch of the median to form the external plantar nerve. Immediately above the knee a cutaneous branch of the ulnar nerve appears between the tendons of the flexor metacarpi medius and flexor



			and Metacarpal Bones d.�pisiform bone of left carpus�anterior aspect i. Facet for radius. 2. Facet for cuneiform. E.�PISIFORM BONE OF LEFT CARPUS�INNER ASPECT i. Facet for radius. 2. Concave and smooth inner surface which forms outer boundary of carpal sheath. F.�SESAMOID BONE�INNER SURFACE i. Roughened area for attachment of intersesamoidean liga- ment. 2. Convex area covered in recent state by fibro-cavtilage. G.�SESAMOID BONE�OUTER SURFACE I. Roughened depression for attachment of slip from suspensory ligament and also the lateral fetlock and lateral sesamoidean ligaments. 2. Articular surface.
		Plate XVI.�Carpal A.�METACARPAL BONES�LATERAL ASPECT I- Small metacarpal bone. 2. Large metacarpal bone. 3. Dif- fused jplint. 4. Button of small metacarpal bone. 5. Nodular splint. ^B-�CARPAL AND METACARPAL BONES�POSTERIOR ASPECT *� Radius. 2. Pisiform. 3. Semilunar. 4. Magnum. 5. Sca- phoid. 6. Unciform. 7. Trapezoid. 8. Outer small metacarpal (body). 9. I_nDer small metacarpal (head). 10. Large meta- carpal bone. 11. Button of small metacarpal bone. 12. Sesa- moid bone. 13. Suffraginis. C-�PISIFORM BONE OF LEFT CARPUS�OUTER ASPECT !� Facet for radius. 2. Convex outer surface. 3. Facet for cuneiform. 4. Groove for tendon of flexor metacarpi externus.



			SUPERFICIAL DISSECTIONS i₇ metacarpi externus muscles. This branch ramifies on the external and anterior aspects of the knee (29). The 'External Plantar Nerve (37).�Below the knee this nerve is seen on the edge of the perforans tendon. It follows the course or the tendon down the limb, behind the vein and artery already described. Just above the level of the button of the splint bone it receives a communicating branch from the internal plantar nerve which winds round to the outer side behind the tendon of the flexor perforatus (41). At the fetlock the nerve gives off its anterior digital branch (40), which crosses the digital artery and vein, and runs obliquely downwards and forwards alongside the corresponding branch of the suspensory igament. It i_s distributed to the coronary cushion. ^e Plantar nerve then divides into the middle and posterior digital nerves T^v» c ¹ ^ne former crosses the digital artery and is distributed to the y cushion and sensitive lamina?, whilst the latter continues ward course, to be ultimately distributed to the sensitive ^amin* ^an<* the pedal bone.

		INNER ASPECT OF LIMB (Plates VI. and VII.) The Bones At the inner aspect of the shoulder joint the anterior and posterior divisions of the inner tuberosity of the humerus are visible. Owing to the flexion of the elbow, the coraco-humeralis and biceps muscles are displaced slightly forwards, with the result that a considerable portion of the inner lateral aspect of the shaft of the humerus is visible, along which numerous vessels and nerves are seen to run. The anterior part of the internal condyle of the humerus is exposed and the posterior part is concealed by the origin of the flexor muscles of the metacarpus and digit.



		18 THE SURGICAL ANATOMY OF THE HORSE The inner edge of the radius (38) is represented throughout its extent. Near the upper extremity of this bone is seen the insertion of the biceps muscle into the bicipital tuberosity. The inner small metacarpal bone (55) is visible throughout its extent excepting a small portion of its head, which is concealed by the insertion of the extensor metacarpi obliquus (46) and by the fibrous band connecting the pisiform bone with the internal lateral ligament of the knee. The inner half of the large metacarpal bone (53) is represented, as is also the greater part of the lateral aspect of the os suffraginis, excepting that part which is covered by the inner division of the suspensory ligament. The Ligaments The edge of the subcarpal or check ligament is much more distinct than on the outer aspect. It appears between the internal metacarpal vein and the large metacarpal artery, the latter having been drawn slightly backwards. The inferior portion of the suspensory ligament is plainly represented, as is also its inner branch (61). This ligament has already been described. The Muscles and Tendons The Subscapulars (1).�This muscle covers almost the whole of the deep face of the scapula. It lies in the subscapular!s fossa, from the whole extent of which it arises. Above the muscle is the cartilage of prolongation (2), which is attached to the vertebral edge of the scapula. The muscle is inserted into the posterior division of the inner tuberosity of the humerus. In front of the muscle we have the supraspinatus (3), and behind it the teres major (4). The subscapularis is an adductor of the shoulder, and is supplied by the subscapular nerve.





			B



		Plate XVIII.�Long and Short Pastern Bones (Showing Exostoses) A, C, and D. Long pastern bones showing exostoses near attachments of ligaments. B. Exostosis on os suffraginis extending round back of flexor tendons. E. True ringbone extending upwards on suffraginis and downwards on coronas under extensor pedis tendon. F. Os coronas showing true ringbone bulging laterally at edges of extensor pedis tendon.



		INNER ASPECT OF LIMB i₉ The Teres Major (4).�The origin of this muscle is from the dorsal angle of the scapula. It is also united to the subscapularis by a fibrous aponeurosis. It is a well-defined muscle, and its anterior border follows closely the glenoid edge of the scapula. It is inserted with the tendon of the latissimus dorsi muscle into the internal tubercle of the humerus, the tendon of the latissimus dorsi forming a twist round that of the teres major. This muscle is a flexor and an inward rotator of the shoulder, and its nerve-supply, as is seen in the plate, comes direct from the brachial plexus. The Scapulo-ulnaris (22).�Only part of this muscle is represented. he upper and anterior portions have been cut away to expose the vessels, muscles, and nerves which lie beneath it. It is a thin, flat muscle, arising from the glenoid border of the scapula. It rests on the teres major and triceps muscles, and is inserted by a thin aponeurotic tendon into the olecranon process and into the fascia of the forearm. It extends the elbow joint, is a slight flexor of the shoulder, and makes tense the fascia of the forearm. The scapulo-ulnaris is supplied by the musculo-spiral nerve. The Triceps Extensor Cubiti.�The caput magnum is visible on this aspect of the fore limb also. It has already been described. The Caput Parvum.�A small portion of this muscle is represented. The remainder is covered by the scapulo-ulnaris. It arises from the shaft of the humerus below the insertion of the teres major and latissimus dorsi, and it is inserted into the olecranon process. The Coraco-humeralis (27).*�The whole of this muscle is seen. It arises from the small tubercle which is placed on the inner aspect of the coracoid process. It has two insertions into the front of the humerus, one above the internal tubercle and the other into a roughened line which extends vertically downwards from the tubercle. Between these two insertions the prehumeral vessels with their accompanying nerve, pass.