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., CO VENT GARDEN

Printed by Ballantyne fr Co. Limited
at the Ballantyne Press, London

The method of dealing with consecutive treatment in Volume II. met
with such general approval that I have been led in the present volume
to handle this branch of work at still greater length, in the hope that it
will make the work more useful to the Practitioner and Final Year's
Student. This has slightly increased the size of the volume ; for it has
been done without in any way curtailing the anatomical descriptions of
the parts, in order that this Part may be of no less service than the second
volume to the student of Anatomy. With this exception the lines of
Part II. have been closely followed.

To my friend and former colleague, Professor Macqueen, who once
again undertook the task of revising the proofs as they were passed for
the press, I am indebted for many valuable suggestions. On the wide
experience and sound judgment of my colleague, Mr. Henry Sumner,
M.R.C.V.S., I have freely drawn ; nor have I ever sought for information
concerning the practical points of the work which has not been most
generously given. To both alike I would express my sincere gratitude ;
for whatever merit might be attached to the work it will in great
Measure be due to their generous help.

For the loan of blocks of Plates XV. and XXVII. indebtedness is
expressed to the kindness of Mr. Hunting and the publishers of the

Veterinary Record, who, with characteristic generosity, placed the whole
of the material of that journal at my disposal.

In conclusion I venture to hope that the present volume may
prove both at home and abroad at least as acceptable as the preceding
volume both to students and practitioners in the study and practice
of the important branch of veterinary work to which it relates.

JNO. T. SHARE-JONES.

Department of Veterinary Anatomy,

The University of Liverpool.

PART III�THE HIND LIMB

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

II. SUPERFICIAL DISSECTIONS........ 12

III. THE LIMB IN SECTION......... 28

IV. THE BONES�FRACTURES AND EXOSTOSES .... 41
V. THE JOINTS............ 85

VI. TENDONS, TENDON SHEATHS, LIGAMENTS, AND BURS-fli . 130

VII. THE NERVES............ 157

VIII. THE BLOOD AND LYMPH VESSELS....... 189

MUSCLES OF THE HIND LIMB........ 215

l>~acilt�
t>a%c

S-Outer and Inner Aspects of Limb (Superficial Dissections)

VIII. Transverse Section through Seat of Posterior Tibial Neurectomy
IX. Longitudinal Section of Hock .......

XIX. Transverse Section through Seats of Spavin and Curb
XXVI. Seat of Posterior Tibial Neurectomy ......

I. Outer Aspect of Left Hind Limb, &c.

IT. Hind Quarter viewed from behind

VII. Transverse Section of Left Stifle (showing Bones, Ligaments, the

Popliteal Vessels, Nerves, and Principal Muscles)

X. Transverse Section across Middle Third of Metatarsal Region of

XI. The Innominate Bones ....

XII. Right Femur ......

XIII. Right Tibia.......

XIV. Fractured Femur, Tibia, Patella, &c.
XV. Tarsal Bones of Ambush II.

XVI. Tarsal Bones in Sheather's Case
XVII. The Stifle Joint�Bones, Ligaments, and Cartilages

Facing-
plate Page

XVIII. The Hock............112

XX. Bursas: and Sheaths in Relation to the Bones . . . . -132

XXI. Posterior Tibial Nerve and Cunean Tendon . . . . .152

XXII. Seats of Peroneal Tenotomy and Anterior Tibial Neurectomy . 156

XXIII. Obturator and Anterior Crural Nerves ...... i6₂

XXIV. Anterior Tibial Neurectomy (Upper Seat) . . . . . .182

XXV. Anterior Tibial Neurectomy (Lower Seat) . . . .184

XXVII. Aneurism of External Iliac Artery . .......194

XXVIII. Metatarsal Region, showing Arteries, Tendons, Ligaments, Bones, &c. 200

SUPERFICIAL EXAMINATION

In the region of the hip the first point which strikes an observer is
the marked prominence indicating the position of the underlying
external angle of the ilium. The lower the condition of the animal
the more prominent does this elevation become. It is frequently and
erroneously indicated by laymen as the position of the hip joint, and
owing to its great prominence and exposed situation is the most common
seat of fracture connected with the pelvis. It may be fractured by the
animal falling on its broadside, since in accidents of this kind it is the
part of the body which comes most forcibly into contact with the
ground. Fracture of it is also very commonly due to the animal's being
carelessly led or driven through a doorway.

When fracture occurs the severed piece is usually displaced in the
downward direction, and remains in the position to which it has been
displaced on account of the action of the muscles which are attached
to it, namely, the anterior arm of the superficial gluteal, the tensor
vagina? femoris, and the internal and external oblique muscles of the
abdomen. In this position, however, union to the main portion of
the ilium usually occurs by ossification, but occasionally a false joint
^may be formed by the union taking place through the formation of
fibrous tissue. In the former case the fracture has little effect upon
the action and working ability of the animal, but has a marked effect

Plate I.�Anterior and Outer Aspects of Hind Limb

A.�right hind limb, anterior aspect

crest * ¹⁰p, ^ned ^by ^tend°n of quadriceps muscle. 2. Elevation formed by patella. 3. Position of tibial
Pedis 6⁴' _p .^atlon ^formed by inner subcutaneous surface of tibia. 5. Elevation formed by belly of extensor

°^Sltl0n ^of ^internal malleolus. 7. External malleolus. 8. Depression (seat of bog spavin). 9. Position

Position of pastern joint.

10. Seat of spavin. n. Metatarsal region.

-outer aspect of left hind limb

2. Position of head of fibula.

neurectomy¹¹ °^rmf^d ^by ^belly ^of ^extenso

3. Seat of lower anterior tibial

⁸- Point of h t ^Seat °^f ^UPP6r ^ditt°' ⁵' ^Bend °^f ^h°^ck' ⁶' ^Elevation caused by belly of peroneus. 7. Fetlock.

^oc^ 9. Coronet. 10. Seat of higher plantar neurectomy. 12. Position of pastern joint.

THE SURGICAL ANATOMY OF THE HORSE

upon its conformation in the dropping of the quarter, which becomes
particularly apparent when the animal is viewed by the observer
standing behind him. In the case of fibrous union the action of the
animal is affected to a greater degree, and there is observed a peculiar
jerky movement in the region of the fracture, owing to the part to which
the muscles are attached having lost its rigidity.

Passing the hand upwards from the angle of the haunch, a large
muscular mass is felt : this is the elevation caused principally by the
middle or great gluteus muscle. In well-nourished animals the mass is
rounded, but in subjects which are emaciated the surface is somewhat
flat. Near the spine another osseous elevation is felt : this is the angle
of the croup or internal angle of the ilium.

Taking a line obliquely downwards and backwards from the angle
of the haunch, we feel a hard, upwardly projecting piece of bone which
terminates bluntly at its superior extremity : this is the summit of the
great femoral trochanter, which is over the hip joint, and its distance
from the external angle of the ilium in an animal about fifteen hands high,
is thirteen inches. Two inches downwards and forwards from this the
convexity of the great trochanter may be felt, but much less distinctly.
Careful manipulation will enable the observer to feel a tendon which plays
over the outer side of the convexity. This is the tendon of the middle
gluteus muscle, which runs to be inserted into the ridge of bone on the
outer side of the convexity, and which is called the crest. An imaginary line
should now be drawn from the summit of the great trochanter obliquely
upwards and backwards to a point seven inches below the root of the tail.
The most prominent point here indicates the position of the under-
lying tuberosity of the ischium. It is not immediately subcutaneous,
but is covered by the semitendinosus muscle. Another imaginary line
should be drawn from the summit of the great trochanter, but in this
case downwards and forwards to the front of the stifle joint. This
indicates the direction of the shaft of the femur, and about one-third of
the distance along this line is placed the external or third femoral

Plate II.�The Hind Quarter viewed from behind

i. Croup. ₂. Anus. 3. Angle of haunch. 4. Elevation formed by tuber
ischii. 5. Groove between biceps femoris and posterior arm of superficial
gluteus. 6. Elevation formed by semimembranosus. 7 and 8. Elevations
formed by semitendinosus. 9. Elevation formed by anterior or great head
of biceps femoris. 10. Elevation formed by gracilis. 11 and 13. Elevations
formed by two remaining heads of biceps femoris. 12. Gastrocnemius.

SUPERFICIAL EXAMINATION 3

trochanter. Two slight and elongated elevations are seen to converge
and meet at the third trochanter. These elevations are due to the
underlying arms of the superficial gluteal muscle. Running obliquely
downwards and forwards behind the imaginary line indicating the
direction of the femur are three elevations which are caused by the
bellies of the three divisions of the triceps abductor femoris or biceps
femoris muscle. The most anterior of the three bellies takes a course
which is almost exactly parallel to that taken by the femoral axis, whilst
the remaining two take courses which approach progressively nearer
the vertical direction.

An imaginary line connecting the external angle of the ilium and
the summit of the great trochanter will, with the axis of the femur, form
sides including an angle which is mainly filled by the quadriceps
extensor cruris muscles. The normal bulk of these muscles should be
carefully noted, since there is a marked falling away in this region in
advanced cases of paralysis of the anterior crural nerve. A delicate
sheet-like muscle runs from the angle of the haunch almost vertically
downwards to be inserted into the fascia of the thigh. This is the
tensor vagina? femoris muscle.

Attention should next be directed to the region of the stifle joint,
and the first point which strikes one here is the prominence in front of
the joint caused by the patella. The bone should be carefully manipu-
lated, its outline mapped out, and its vertical movement on the trochlea
of the femur demonstrated to the observer's satisfaction by taking the
limb up and flexing and extending the joint. In this manner also the
lips of the trochlea may be made more apparent to the touch. On the
anterior aspect of the patella a broad flattened tendon should be found.
This is the tendon of the quadriceps or crural muscles, the action of
which is transmitted to the limb through the medium of the straight
ligaments of the patella.

Below the patella is a transverse indentation. This invites most
careful observation, since a symptom of several affections of the stifle

Plate III. Superficial Dissection.
Hind Limb (right), Outer aspect.�i. Quadriceps muscles. 2. Outer condyle of femur. 3. Insertion
01 superior division of biceps femoris. 4. External popliteal nerve. 5. Patella. 6. External saphenous nerve.
7- External lateral ligament of stifle. 7A. Insertion of external straight patellar ligament into anterior tuberosity
or tibia. 8. Communicating branch from external popliteal nerve to external saphenous nerve. 9. Common tendon
01 extensor pedis and tendinous division of flexor metatarsi. 10. Outer belly of gastrocnemius. II. Extensor pedis.
^Jo -tendon of origin of peroneus. 13. Musculo-cutaneous nerve. 14. Anterior tibial nerve. 16. Perforans muscle.
Io. Peroneus muscle. 20. Tendon of gastrocnemius. 22. Tendon of perforatus playing over summit of tuber calcis.

N.B.�The soleus muscle has been removed.

4 THE SURGICAL ANATOMY OF THE HORSE

joint is a filling up of this depression. The external lateral ligament of
the stifle will be found to take a course downwards to the head of the
fibula, which will be felt as a slight hard elevation at a distance of one
inch below the femoro-tibial articulation. The three straight ligaments
are felt below the patella running to their attachments into the anterior
tuberosity of the tibia.

In front of the head of the fibula is a powerful tendon, which if
followed upwards will be found to be inserted between the outer
condyle of the femur and the external lip of the trochlea. This is the
tendon which is common to the extensor pedis muscle and the tendinous
or superficial portion of the flexor metatarsi. The tendon is succeeded
by a prominent belly, which forms a well-marked and rounded elevation
at the front of the tibial region. This elevation is due chiefly to the
underlying extensor pedis muscle, deeply seated to which is the flexor
metatarsi. The outline of the extensor pedis is easily visible, since it
forms a prominent surface marking, and manipulation is not necessary to
define it.

Running in a vertical direction parallel to the elevation formed by
the extensor pedis is another elevation which indicates the course of the
peroneus muscle. This muscle arises from the external lateral ligament
of the stifle, from the head of the fibula, and the aponeurotic septum
between it and the deep flexor of the digit.

The elevation formed by the peroneus muscle is not so prominent as
is that formed by the extensor pedis, as its belly is much less bulky and
is not so well developed. The surface of the extensor pedis is convex in
the longitudinal direction and markedly so from side to side, whereas the
surface of the peroneus is much more flattened.

Between the two elevations just described is a vertical depression into
which the anterior tibial nerve dips. This nerve may be distinctly
felt as it crosses the outer surface of the peroneus muscle obliquely prior
to its disappearing between the two muscles. A little lower down the
musculo-cutaneous branch of the anterior tibial nerve crosses the

Plate IV. Superficial Dissection (continued).
Hind Limb (right) Outer aspect.�15. Superior annular band. 17. Middle annular band. 19. Inferior
annular band. 20. Tendon of gastrocnemius. 21. Large metatarsal artery. 22. Tendon of perforatus playing over
summit of tuber calcis. 23. Tendon of peroneus. 24. Extensor brevis. 25. Branch of large metatarsal artery
26. Perforatus tendon below hock 27. Tendon of extensor pedis. 28. Tendon of perforans. 29. Outer small
metatarsal bone. 30 Suspensory ligament 31. Terminal filament of external saphenous nerve. 32. External
metatarsal vein. 33. Large metatarsal bone. 34. Unnamed artery descending with plantar nerve. 35. Button of
outer small metatarsal bone. 36 and 39. External plantar nerve. 37. External digital artery. 38. Communicating
branch from internal ulantar nerve 40. External digital vein. 41. Anterior digital nerve. 42. Middle digital
nerve. 43. Perpendicular artery of pastern. 44- Posterior digital nerve. 45. Plexus of veins or, external surface
of lateral cartilage. 46. Coronary cushion. 47. Sensitive lamina;.

N.B.� The external metatarsal vein usually emerges from the venous arch near the fetlock slightly lower
down than represented in the plate.

SUPERFICIAL EXAMINATION 5

peroneus muscle. In some animals this nerve may also be felt beneath
the skin and fascia. It takes a direction across the superficial aspect of
the muscle downwards and forwards, which approaches nearer the vertical
than that taken by the anterior tibial nerve. A large branch is given off
by this nerve for the supply of the peroneus muscle, and the nerve, much
reduced in size, continues its downward course along the line of the
^aPposition of this muscle with the extensor pedis. During this part
^of its course, however, the nerve is more deeply seated, is wedged in
between the two muscles, and cannot be felt in an examination such as
We are now making.

The depression just mentioned is of great importance, since it is
the seat of the operation of anterior tibial neurectomy.

The belly of the extensor pedis will be found to be succeeded by
a tendon which passes beneath one of the annular bands at the inferior
extremity of the tibia, and plays over the front of the hock slightly
to the outer side of the middle line. Its subsequent course will be
traced later, as also will the tendon of the peroneus, which runs in a
vertical direction and plays through a groove on the outer side of the
external malleolus of the tibia.

The back of the thigh is very fleshy, owing to the enormous
bulk of the hamstring muscles, which extend to a much lower level
than in man, so that in the horse the back of the stifle is well
protected, and the posterior common ligament of the joint is deeply
seated. The muscles of the hamstring also clothe and protect the great
sciatic nerve with its accompanying vessels.

The inner aspect of the thigh will be found to be very flat, and
the bone is here also clothed by muscles which are the adductors of
the limb. Those which form the superficial layer, and are subcutaneous,
are the sartorius anteriorly and the gracilis posteriorly. The gracilis
occupies about four-fifths of the area described, and its surface is quite
flat, whilst the skin covering the sartorius is slightly raised, since the
muscle forms an elevation which runs downwards and backwards.

Plate V. Superficial Dissection.

Hind Limb (right), Inner aspect.�i. Quadriceps muscles. 2. Sartorius and gracilis. 3. Patella. 4. Gastrocnemius (inner
^l>e'Iy). 5. Internal lateral ligament of stifle. 6. Internal straight ligament of patella. 7. Trochlea of femur (inner lip). 8. Pophteus
muscle. 9. Internal (subcutaneous) surface of tibia. 10. Flexor accessorius muscle. 11. Internal saphena vein. 12. Posterior
tibial nerve. 13. Anterior root of internal saphena vein. 14. Perforatus tendon. 15. Posterior root of internal saphena vein.

16. Posterior tibial artery. 17. Flexor metatarsi (deep or muscular division). 18. Cutaneous branch of posterior tibial nerve.

19. Flexor perforans. 20. Retrograde branch of posterior tibial artery. 21. Tendon of flexor accessorius. 22. Plantar nerves.

23- Sigmoid curve of posterior tibial artery. 24. Summit of tuber calcis covered by perforatus tendon. 25. Superior annular band.

N.B.�The belly and tendon of the gastrocnemius have been drawn slightly backwards in order to display more fully the
posterior tibial nerve.

6 THE SURGICAL ANATOMY OF THE HORSE

Behind the gracilis is another elevated area due to the underlying
semimembranosus muscle.

Running obliquely upwards and forwards across the gracilis is the
internal saphena vein, a vessel of large calibre which is formed by the
union of the upward continuations of the outer and inner metatarsal
veins. It dips in between the sartorius and gracilis about the junction
of the upper and middle thirds of their line of apposition, and empties
itself ultimately into the femoral vein. The application of pressure
will cause the vessel to be raised, when its course becomes much
more evident. It is occasionally adopted as a seat for the operation
of venesection.

In front of the saphena vein is the saphena artery, a long and slender
vessel which follows the course of the vein, and divides into two
branches which accompany the outer and inner roots of the saphena
vein.

Anteriorly placed to the saphena artery again is the internal saphena
nerve. This arises from the anterior crural nerve at the brim of the
pelvis, and emerges from between the sartorius and gracilis with the
artery and vein. It will be further dealt with in the chapter on nerves.

The slight depression which indicates the position of the interstice
between the sartorius and gracilis should be carefully examined,
particularly in its upper part, which is the situation of the deep
inguinal lymphatic glands. In this region the glands cover the under-
lying femoral vessels, and they become very evident in cases of
lymphangitis.

If the hand be now passed down the inner aspect of the limb, it
will be ascertained that the inner surface of the tibia is immediately sub-
cutaneous, and it will also be found that the subcutaneous bone is widest
above and gradually tapers as we descend. Manipulation of this part
is of importance in the diagnosis of deferred fracture, of which particular
injury the shaft of the tibia is the most common seat.

The very important region of the hock is next to be considered.

Superficial Dissection (continued).

Hind Limb (right), Inner aspect.�22. Plantar nerves. 23. Sigmoid curve of posterior tibial artery. 24. Summit of tuber calcis
covered bv perforatus tendon. 25. Superior annular band. 26. Cutaneous branch of posterior tibial nerve passing oyer seat of spavin.
27- Cunean tendon. 28. Tendon of perforans leaving tarsal sheath. 29. Internal metatarsal vein passing upwards to form anterior
root of internal saphena vein. 30. Perforatus tendon. 31. Inferior annular band. 32- Internal plantar nerve. _ _33; Extensor

pedis tendon ₃₄. Unnamed artery descending with plantar nerve. 35- Large metatarsal bone 36. Communicating branch

from internal plantar nerve. ₃₇. Suspensory ligament. 38. Internal digital vein. 39- Internal small metatarsal bone. 40. Internal
digital artery. _4I. Button of small metatarsal bone. 42. Internal plantar nerve. 43- Inner branch of suspensory ligament.

44. Posterior digital nerve. ₄₅. Anterior digital nerve 46 Tendon of perforans leaving ring formed by perforatus. 47. Middle
digital nerve. 48. Os suffraginis. ₄₉. Perpendicular artery of pastern. $0. Sensitive lamina:. 51. Plexus of veins on lateral
cartilage. 52. Coronary cushion.

N.B.�The internal metatarsal vein usually emerges from the venous arch near the fetlock slightly lower down than represented
in the plate.

SUPERFICIAL EXAMINATION 7

Assuming that the " near " hock is the one to be examined, the student
should first stand with his face directed towards the horse's head, and
should pass the palmar aspect of his right hand over the front of the
hock. In this manner the tracing of the tendon of the extensor pedis
^may be made, and the tendon may be caused to stand out prominently
" the hock be flexed. The main portions of the tendons of the flexor
^rnetatarsi muscle may also be traced to their insertion into the anterior
*ace of the upper extremity of the large metatarsal bone, though these
tendons are not quite so evident as is that of the extensor pedis.

On the inner aspect of the joint two prominent elevations are seen,
the upper of which is caused by the internal malleolus of the tibia,
^and the one below it by the well-defined tubercle on the inner surface
°f the astragalus. The tubercle just mentioned varies considerably in
size in different animals. The size of the tubercle is not a matter
°f great consequence, provided both tubercles are alike and well
defined. The tubercle is only in rare and advanced cases involved in
spavin, and when such happens it loses its well-defined outline, and in
its place we have a diffused enlargement.

Running almost vertically across the internal malleolus of the tibia
^1S a faint depression which, when we come to study the deeper
anatomy of the joint, we shall find gives passage to a tendon, namely,
that of the flexor accessorius muscle.

The usual seat of spavin is on the antero-internal aspect of the
inferior third of the joint, and the touch of the fingers should be care-
fully educated to appreciate the exact normal conformation of this area.
■This is only brought about by constant practice, since the difference in
^external contour presented by a normal hock and many hocks affected
^Wlth spavin is so slight that it is only appreciable to a sense of touch
^hich has been cultivated to a considerable degree of delicacy.

Below the elevation caused by the tubercle of the astragalus a slight
ⁿ°^rizontally disposed elevation is found which curves round from the
^anterior to the internal aspect of the joint. This elevation corresponds

Plate VII.�Transverse section of Left Stifle, indicating Bones,
Ligaments, the Popliteal Vessels and Nerves, and Principal

i. Middle straight patellar ligament. 2 and 3. External and internal
ditto. 4. Outer portion of anterior tuberosity of tibia. 5. Adipose tissue.
6. Common tendon of extensor pedis and tendinous division of flexor
metatarsi, with its sheath. 7 and 12. Anterior and posterior coronary
ligaments from internal disc. 8 and 16. Ditto from external disc. 9. In-
sertion of anterior crucial ligament. 10. External tuberosity. 11. Tibial
spine. 13. Internal lateral ligament. 14. External ditto. 15. Tubercle
at back of internal tuberosity. 17. Insertion of posterior crucial ligament.
18. External popliteal nerve, 19 and 20. Popliteal vein and artery.
21. Posterior common ligament. 22. Popliteus muscle. 23. Flexor per-
foratus. 24. Internal popliteal nerve. 25 and 26. Inner and outer heads
of gastrocnemius.

N.B.�See descriptive text, chapters ii., iii. and v. for other muscles,
vessels and nerves.

8 THE SURGICAL ANATOMY OF THE HORSE

to the anterior and inner surfaces of the scaphoid bone. Immediately
below this is a faint depression which runs parallel to the elevation just
described. This depression is situate between the most prominent
portion of the anterior and inner surfaces of the scaphoid above, and the
anterior surface of the cuneiform magnum together with the inner
surface of the cuneiform parvum below. These surfaces of the cunei-
form bones cause another horizontal elevation, which, however, is not so
well-defined as the one already described, being simply a faint upheaval
of the surface. It differs moreover from the first-mentioned elevated
area, inasmuch as it is not continuous, being interrupted by a little
depression which is placed between the two cuneiform bones. This
depression therefore is disposed vertically.

The horizontal elevation corresponding to the two cuneiform bones
forms the superior boundary of a second transverse depression which is
not so apparent as that already described, and which is bounded inferiorly
by the prominent upper extremity of the large metatarsal bone and the
head of the inner small metatarsal bone. This depression is crossed at
right angles by the one which has been mentioned as running vertically,
and the latter is continued in the downward direction between the
prominences which indicate the position of the head of the inner small
metatarsal bone and the large metatarsal bone.

The subjacent osseous structures to which the various elevations
mentioned correspond, and their disposition one to the other will be
easily understood by a reference to Plate XVIII.

Running inwards and slightly downwards from the front of the joint
to the small cuneiform bone is a broad, flat tendon, which can be felt
only when a considerable amount of pressure is applied. This is the
cunean division of the tendon of the flexor metatarsi muscle.

The insertion of the cunean tendon will be found to be in line with
a horny excrescence which is confined to the skin and which is called
the chestnut.

The branch from the superficial tendon of this muscle may be felt,

Plate VIII.�Transverse Section of Right Hind Limb Through Seat of Posterior Tibial Neurectomy.

� flexor Metatarsi. 2. Extensor pedis. 3 & 7. Branches of internal saphena nerve. 4. Musculo-cutaneous nerve.

5- Anterior root of internal saphena vein. 6. Anterior tibial nerve. 8. Anterior tibial veins. 9. Tibia. 10. Anterior tibial

^ar y- ^IT- Perforans muscle. 12. Peroneus muscle. 13. Tendon of flexor accessorius. 14. External saphena vein.

^lS- Posterior root of internal saphena vein. 16. External saphena nerve. 17. Posterior tibial artery with vena? comites.

18. Tendon of gastrocnemius. 19. Posterior tibial nerve. 20. Tendon of flexor perforatus.

SUPERFICIAL EXAMINATION 9

though less distinctly, to run outwards and with a slight downward
inclination to its insertion into the cuboid bone.

The outer aspect of the hock should now be examined. It will be
round that there is no tubercle on the external lateral aspect of the
astragalus, but a faint depression will be felt in the part which corre-
sponds to the position of the tubercle on the inner lateral surface of this
bone.

Below the astragalus and calcis on this side of the joint is the cuboid,
and inferiorly to this bone the head of the external small metatarsal
bone will be easily located; and the observer should make himself quite
iamiliar with its normal size, since an abnormally large head of the small
metatarsal bone frequently leads to considerable confusion and constitutes
the condition designated as false curb.

The outer aspect of the left hock is best examined with the left hand,
with one's back directed towards the patient's head.

If the hand be now passed down the back of the leg the bulging
bellies of the gastrocnemius will be felt, and from them the succeeding
tendon may be traced. From two to three inches above the point of the
hock it will be ascertained that another tendon twists round that of the
gastrocnemius, passing from the deeper aspect of the latter to its inner
side and subsequently being placed superficially to it.

This tendon is that of the superficial flexor of the digit {i.e., the flexor
perforatus), and it will be found to become very much flattened out as
we approach the summit of the calcis which forms what is known as
the point of the hock. This is the seat of the affection known as the
capped hock.

At the middle ot the summit of the calcis the tendon of the
perforatus leaves that of its gastrocnemius, and the latter will be found to
terminate. The perforatus tendon, however, plays over the upper
extremity of the bone, and between it and the bone is interposed a
small synovial bursa, to facilitate the gliding movement of the tendon.

The further course of the perforatus tendon may be traced, and it

Plate IX.�Longitudinal Mesial Section of Left Hock Showing Inner Face of Outer Portion.
i. Extensor pedis muscle. 2. Flexor perforans muscle. 3. Flexor metatarsi (tendinous and muscular divisions). 4. Tendon
of gastrocnemius. 5- Tendon of extensor pedis. 6. Tendon of flexor perforatus 6a. Bursa beneath Perforatus Cap. 7. Superior
annular band. 8. Tuber calcis. 8a. Tarsal sheath. 9. Tibia. 10. Posterior common ligament. II. Anterior common
ligament. 12. Synovial membrane of true hock joint. I2A. Body of calcis. 13. Middle annular band. 14. Scaphoid.
15. Astragalus. 15A. Astragalo-metatarsal ligament (see Text). 16. Tarso-metatarsal ligament. 17. Inferior annular band.
18. Cuneiform magnum. 19. Insertion of flexor metatarsi into large metatarsal bone. 20. Suspensory or superior sesamoidean
ligament. 21. Large metatarsal bone. 22. Subtavsal or check ligament. 23. Tendon of flexor perforans.

io THE SURGICAL ANATOMY OF THE HORSE

will be found to run straight down the posterior border of the tuber
calcis. It should be carefully noted that the surface in this region is
straight, for a slight convexity of the surface of the postero-inferior
aspect of the hock would most probably indicate the presence of a
curb.

Below the hock another tendon makes its appearance, and is easily
felt to be placed immediately in front of that of the perforatus. This is
the tendon of the perforans muscle, and it has resumed its former position
in front of the perforatus after leaving the tarsal sheath, to pass through
which it left the perforatus above the hock.

Immediately below the hock on the antero-external aspect of the
limb two tendons may be clearly detected as being subcutaneous. The
tendon which is the nearer to the middle line is that of the extensor
pedis muscle. The other is the peroneal tendon. If the course of
each tendon be followed in the downward direction they will be
found to become united to one another about four inches below the
hock.

The tendon of the peroneus should next be traced in the upward
direction, when it will be found to run obliquely upwards and back-
wards to gain the outer aspect of the hock joint, where it has already
been followed to the groove on the external malleolus of the tibia.

On the inner and outer surfaces of the metatarsal region a groove is
felt which takes a vertical direction. These grooves are situate between
the large and small metatarsal bones.

Along part of the groove between the large metatarsal bone and
the outer small metatarsal the large metatarsal artery runs, the position
of which may be ascertained by the pulsation of the vessel, which can be
detected without much difficulty. Tracing the vessel upwards, we find
that the peroneal tendon crosses it obliquely in passing from the groove
in the external tibial malleolus to its attachment to the tendon of the
extensor pedis.

A tiny muscle runs in front of, and parallel to the tendon of the

Plate X.�Transverse Section of Middle Third of Metatarsal
Region of I,eft Hind Limb

i. Tendon of extensor pedis muscle. 2. Large metatarsal bone. 3. Large
metatarsal artery. 4. Internal small metatarsal bone. 5. External ditto.
6. Internal plantar interosseous artery. 7. External ditto. 8. Deep meta-
tarsal vein. 9. Suspensory ligament. io and 11. Internal and external
metatarsal veins. 12 and 13. Small unnamed arteries descending with
plantar nerves. 14 and 15. Internal and external plantar nerves.
16. Tendon of flexor perforans. 17. Tendon of flexor perforatus. 18. Branch
of communication between internal and external plantar nerves.

SUPERFICIAL EXAMINATION

peroneus muscle. This is the extensor brevis, and, like the peroneal
tendon, this muscle also crosses the large metatarsal artery.

By tracing the tendons of the extensor pedis and peroneus, and the
large metatarsal artery, upwards from the metatarsal region, it will be
found that they become suddenly lost to the touch at the upper extremity
of the large metatarsal bone, and further manipulation will reveal the
presence of a transverse subcutaneous thickening. This is the most
inferior of the three annular bands which are found at the hock, and
under it the structures named, together with the extensor brevis
muscle, pass.

The subtarsal or check ligament is not so easily felt as the
corresponding structure in the fore limb.

In the inferior two-thirds of the metatarsal region only one tendon
is felt on the anterior aspect of the limb, namely, that of the extensor
pedis muscle. In the fore limb two tendons are present, for, in addition
to the tendon of the extensor pedis, there is the tendon of the extensor
suffraginis running to its insertion on the second phalanx.

Plate XI.�The Innominate Bones

A.�INFERIOR ASPECT

i. Inferior ischiatic spine. 2. Ischiatic symphysis. 3. Obturator foramen. 4. Pubio-femoral groove. 5. Cotyloid cavity. 6. Grooves
for ilio-femoral vessels. 7. Brim of pelvis. 8. Angle of croup. 9. Auricular facet. 10. Grooves for ilio-lumbar vessels. 11. Angle
of haunch.

B.�LATERAL ASPECT (THE BONES INVERTED)

I. Gluteal surface of ilium. 2 Shaft of ilium. 3. Cotyloid cavity 4. Superior ischiatic spine. 5. Ischium. 6. Inferior ischiatic
spine. 7. Tuber ischii. 8. Obturator foramen. 9. Pubio-femoral groove. 10. Brim of pelvis.

SUPERFICIAL DISSECTIONS

OUTER ASPECT OF LIMB

Such a dissection is represented in Plates III. and IV.

Near the upper extremity of the limb, the patella is seen to bulge
prominently forwards (5). To its anterior face is attached the tendon
of insertion of the quadriceps muscles (1) and also the external
straight patellar ligament.

Below the patella is the anterior tuberosity of the tibia, which
is continued downwards into the ridge of bone known as the tibial
crest. The crest disappears as we descend the limb, since it gradually
subsides to blend with the anterior face of the bone.

The external condyle of the femur (2) is placed behind the
patella, and is partially concealed by a flat piece of muscular tissue
which is the inferior extremity of one of the divisions of the biceps
femoris muscle.

Inferiorly placed to this condyle, but separated from it by the
outer semilunar cartilaginous disc, is the external tuberosity of the
tibia, of which only the anterior portion is visible. It is separated
from the anterior tuberosity by a well-marked notch, through which
the tendon common to the extensor pedis and the superficial tendinous
portion of the flexor metatarsi plays.

Descending from this tuberosity in a vertical direction for a

Plate XII.�Right Femur

A.�ANTERIOR ASPECT

1. Summit of great trochanter (insertion of one of tendons of middle gluteus muscle).

2. Insertion of deep gluteus into inner face of convexity. 3. Outer surface of convexity
(seat of synovial bursa beneath tendon of middle gluteus). 4. Articular head. 5. Crest
of great trochanter, into which is inserted tendon of middle gluteus, which pla}-s over
outer suiface of convexity. 6. Sulcus in head. 7. External or third trochanter, to which
is attached tendon of superficial gluteus muscle. 8. Internal or small trochanter, into
which are inserted the psoas magnus and iliacus muscles. 9. Anterior surface (this and
the lateral surfaces are clothed by the quadriceps extensor cruris muscle). 10. Inner
ridge of trochlea. 11. Outer ridge of trochlea. 12. Groove of trochlea.

B.�POSTERIOR ASPECT

I. Summit of great trochanter. 2. Articular head. 3. Trochanteric ridge. 4. Sulcus
in head. 5. Trochanteric fosfa. 6. Internal or small trochanter. 7. Tubercle for
attachment of slip from biceps femoris. 8. Roughening for insertion of quadratus
femoris. 9. Ridges for insertion of adductor muscles. 10. Nutrient foramen.

II. Roughening for insertion of pectineus. 12. Groove for femoral vessels. 13. Supra-
condyloid fossa. 14. Supracondyloid crest. 15 and 16. External and internal condyles.
17. Intercondyloid groove.

SUPERFICIAL DISSECTIONS 13

distance of about twelve inches in the living animal, bone is
again found to be superficially placed, and here we have the ex-
ternal malleolus of the tibia, which presents a well-marked vertical
groove for the passage of the tendon of the peroneus muscle (23).
The outer lateral surface of the astragalus is situate below the
malleolus, and behind these two elevations is the prominent tuber
calcis. This is concealed by the tendon of the perforatus, which is
here very much flattened (22). Inferiorly to the calcis is the cuboid,
and below this again we have the head of the outer small metatarsal
bone (29). Extending obliquely downwards and forwards from the head
is the body of the last-mentioned bone, which gradually tapers from
above downwards. It terminates inferiorly in the rounded nodule
termed the button, which is placed about two inches above the fetlock
joint (35). The button is easily located in the living animal, since
between it and the large metatarsal bone there is a slight interval, and
^tne button springs a little upon the application of pressure.

In front of the small metatarsal bone is a groove down which
the large metatarsal artery runs. The groove is bounded anteriorly
by the large metatarsal bone. The greater part of the lateral surface
°t this bone is visible in the plate, and in the living animal is
immediately subcutaneous (33).

The sesamoid bones are concealed from view by the broadened-
°^ut perforatus tendon and the lateral division of the suspensory
hgament, but below the fetlock a considerable portion of the lateral
surface of the sufFraginis is represented, as is also the tuberous
lateral aspect of its inferior extremity.

*he 'External Straight Patellar Ligament (ya).�This ligament runs

^wnwards in a vertical direction from the anterior surface of the

r ^eHa to the outer division of the anterior tuberosity of the tibia. In

Plate XIII.�The Right Tibia

A.�POSTERIOR ASPECT
I. Spine of tibia. 2 and 3. External and internal tuberosities. 3a. Tubercle for attachment of posterior crucial
ligament. 4. Depression for head of fibula. 5. Depression for accommodation of popliteus muscle. 6. Nutrient
foramen. 7. Tubercle for insertion of popliteus muscle. 8. Ridges for attachment of flexor perforans muscle.
9. Groove for passage of tendon of flexor accessorius. 10. Groove for tendon of peroneus muscle. 11. External
malleolus.

B.�ANTERIOR ASPECT
1. Insertion of anterior crucial ligament. 2. Spine of tibia. 3 and 4. External and internal tuberosities. 5. Notch
for passage of common tendon of extensor pedis and superficial division of flexor metatarsi. 6. Groove in
anterior tuberosity. 7. Articulation for head of fibula. 8. Outer division of anterior tuberosity. 9. Crest of tibia.
10 and n. Internal and external malleoli.

14 THE SURGICAL ANATOMY OF THE HORSE

the Plate the ligament is relaxed and dips inwardly between the patella
and the tibia, owing to the fact that the former is placed at the lower
end of the trochlea since the quadriceps muscles are relaxed.

The External Lateral Ligament of the Stifle (j).�This is repre-
sented as being attached to the external surface of the outer condyle
of the femur above and to the head of the fibula below. The fibres of
the peroneus muscle are seen to arise from this ligament.

At the front of the hock the three transverse fibrous bands are shown
which hold the tendons playing over this part in position (15, 17, and 19).

The Great Suspensory Ligament (30) first becomes visible about three
inches below the head of the small metatarsal bone, the upper portion
of the ligament being concealed by the greater thickness of this bone.

Above the fetlock the ligament divides into two parts, and the outer
division may be followed obliquely across the outer aspect of the fetlock-
joint to the front of the limb, where it becomes united to the tendon of
the extensor pedis, as in the fore limb.

The Muscles and Tendons

The Quadriceps Extensor Cruris (1).�These are the muscles which
clothe the anterior and .lateral surfaces of the shaft of the femur.
Only the outer half of the inferior third of these muscles is shown,
since the limb has been severed across the line of division between
the middle and inferior thirds of the femur. The muscles are inserted
on the anterior face of the patella.

They are the great extensors of the stifle joint, their action being
transmitted to the limb through the medium of the straight ligaments of
the patella.

They are supplied by the anterior crural nerve, and are the muscles
which are affected in crural paralysis.

The Biceps Femoris (3).�This muscle is in three divisions : one is
inserted into the patella, another into the tibial crest, and the third into

Plate XIV.--Fractured Femur, Tiuia, Patella, etc.

A.�Posterior aspect of left tibia showing fracture.


				� '

THE SURGICAL ANATOMY OF THE HORSE

	BY 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.

			PART III

		Review Copy, LONDON WILLIAMS AND NORGATE 14 HENRIETTA ST., CO VENT GARDEN 1908



	THE FEMUR
	THE FEMUR	5¹
		5¹

THE FEMUR This is a long bone which extends obliquely downwards and forwards from the hip joint above to the stifle joint below. It is the most massive bone in the whole body. It possesses a shaft and two expanded extremities. The shaft may be said to present for description four surfaces. The anterior and lateral surfaces are blended with one another, are markedly convex in the transverse direction, and almost straight from above to below. These three surfaces are clothed by the vastus externus, vastus internus, rectus femoris, and rectus parvus muscles, which are collectively called the quadriceps extensor cruris. The posterior surface is widest superiorly where it presents a four- sided, somewhat flattened area. This area extends outwardly into a well-marked depression, which is placed to the inner side of the trochanteric ridge, and hence receives the name trochanteric fossa. In the fossa the obturator externus, obturator internus, pyriformis, and gemelli muscles are inserted. Inferiorly and towards the outer side of the bone, the above-mentioned area extends on to the back of the external or third trochanter. Here is found a roughened elevation with a somewhat circular base, which gives attachment to the femoral slip from the biceps femoris or triceps abductor femoris muscle. Almost in line with this elevation and towards the inner side of the bone is a roughened area to which the quadratus femoris muscle is attached. Below the tubercle to which the biceps femoris is attached, and where the shaft of the bone becomes very much narrowed down, are two or three roughened ridges. These give attachment to the great and small adductor muscles of the thigh. The nutrient foramen is placed in the middle third of the bone and towards its inner edge. The canal into which the nutrient artery passes is disposed at right angles to the surface of the bone. Quite



	FRACTURE OF THE PATELLA
	FRACTURE OF THE PATELLA	59
		59

FRACTURE OF THE PATELLA This is usually due to a blow, such as a kick, or it may be caused by the stifle being flexed to an extraordinary degree. Owing to the manner in which the ligaments and tendons are inserted into the front of the patella, fractures which are due to violent muscular contraction are usually in the horizontal direction. When the fracture is due to a blow, the bone is usually broken into several pieces, and the fracture is of the comminuted variety. The numerous ligaments and tendons which are attached to the patella are more or less connected with one another by a plentiful supply of fibrous tissue in the part. After the infliction of the injury, therefore, this binding structure has the effect of keeping the fractured pieces in position, so that there is rarely any displacement. It will thus be understood that crepitation is not frequently a symptom of fracture of the patella, and on account of the numerous structures which are attached to the bone, there will be inability on the part of the animal to move without being subjected to great pain. The patella is not a bone which lends itself readily to the healing of fractures, and this is particularly so when the fracture concerns the inferior portion of the bone. This is due to the fact that the nutrient vessels of the bone pierce its superior surface and the lower portion is very poorly supplied with blood. Treatment of fractured patella in the human subject by the insertion of ivory connecting pegs or screws of steel or silver, has in recent years met with a considerable amount of success. In equine practice, however, prognosis is usually unfavourable, particularly when the joint is associated with the injury, as is very frequently the case. The animal should be placed in slings, and adhesive strapping applied to the joint to keep the part as still as possible. Further than this, little can be done.



	SPAVIN
	SPAVIN	73
		73

SPAVIN This is one of the most serious and troublesome diseases with which the surgeon has to contend. It is an affection of the antero-internal portion of the hock, and our reasons for treating the disease here will be gathered from the description which follows. It is a disease which is extremely common, and, notwithstanding the great amount of work which has been done in this connection in the past, several phases remain to this day in obscurity. There is scarcely a veterinary writer who has not at some time or other had his attention attracted to it, whilst it is more or less exhaustively dealt with in all surgical text-books. The area affected is usually the inferior third of the antero-internal portion of the joint. The bones of this portion are the cuneiform magnum, cuneiform parvum, scaphoid, the upper end of the inner small metatarsal, together with the inner portion of the proximal extremity of the large metatarsal. These bones form between them a number of synovial joints of the arthrodial class. Movement is, however, restricted in the joint formed between the large and inner small metatarsal bones by the ossifica- tion of the interosseous ligament which unites these bones to one another in the immature animal. There is free movement, however, in the joints formed by the cuneiform bones and the scaphoid, and also between the cuneiform bones and the metatarsals. These joints are all supplied by synovial membranes, and the surfaces of the bones which come into apposition with one another at the joints are clothed, with articular cartilage (for a fuller description see the chapter on joints). From our description of the bones it will be remembered that a roughened ridge extends transversely across the front of the scaphoid, and that this ridge is continued on to the inner edge of the bone. Another ridge, parallel to the one just mentioned, is found on the cuneiform magnum. This latter ridge is slightly the more prominent, and extends on to the inner aspect of the joint. Between these two ridges is a transverse groove, at K



	SPAVIN	81
		81

it is obvious that if the inflammatory process be hastened, the sooner will anchylosis occur, the pain subside, and lameness disappear. The application of counter-irritants has this effect ; consequently blistering the hock is in some cases indicated. But, acting on this principle, pyro-puncturing the hock is considered by many to be the most effective method of treatment, and the author has frequently found this method attended with successful results, particularly in cases in which there is a fairly well-defined exostosis. For the purposes of this operation either a ball-headed iron with a needle, or an iron in which the head is drawn out very gradually to a point, should be utilised. This is i« order that the needle or iron may be pushed well into the exostosis without producing a large cutaneous opening. The position of the internal saphena vein is easily located, and it should, of course, be avoided. One puncture is usually sufficient, though two or three may be made if the exostosis be a large one ; but more than two or three are quite unneces- sary. A blister should then be rubbed well into the part, biniodide ot mercury being preferable, on account of its antiseptic properties. Another method of treatment, with a similar object, is to insert a seton or rowel beneath the skin over the exostosis, the seton or rowel being coated with ointment blister. Line-firing is sometimes adopted, a feather pattern being selected, with the central line running obliquely over the seat. This method, however, is not nearly so effective as that of pyro-puncture. Some operators sever the cunean division of the flexor metatarsi tendon, scrape the parts beneath, subsequently applying a blister. The object in this case is the same as in pyro-puncturing. In performing the operation the tendon is located in the manner described in dealing with cunean tenotomy. The tendon is not exposed, but the blade or the knife is pressed through the skin, and the tendon severed trans- versely. That the tendon is severed will be evident from the fact that the portion which is still attached to the muscle will be found to be relaxed. This may be felt on manipulation. The cutaneous incision L



		PREFACE TO PART III The method of dealing with consecutive treatment in Volume II. met with such general approval that I have been led in the present volume to handle this branch of work at still greater length, in the hope that it will make the work more useful to the Practitioner and Final Year's Student. This has slightly increased the size of the volume ; for it has been done without in any way curtailing the anatomical descriptions of the parts, in order that this Part may be of no less service than the second volume to the student of Anatomy. With this exception the lines of Part II. have been closely followed. To my friend and former colleague, Professor Macqueen, who once again undertook the task of revising the proofs as they were passed for the press, I am indebted for many valuable suggestions. On the wide experience and sound judgment of my colleague, Mr. Henry Sumner, M.R.C.V.S., I have freely drawn ; nor have I ever sought for information concerning the practical points of the work which has not been most generously given. To both alike I would express my sincere gratitude ; for whatever merit might be attached to the work it will in great Measure be due to their generous help. For the loan of blocks of Plates XV. and XXVII. indebtedness is expressed to the kindness of Mr. Hunting and the publishers of the



		vi PREFACE Veterinary Record, who, with characteristic generosity, placed the whole of the material of that journal at my disposal. In conclusion I venture to hope that the present volume may prove both at home and abroad at least as acceptable as the preceding volume both to students and practitioners in the study and practice of the important branch of veterinary work to which it relates. JNO. T. SHARE-JONES. Department of Veterinary Anatomy, The University of Liverpool. June 1908.



		CONTENTS PART III�THE HIND LIMB CHAP- PAGE I. SUPERFICIAL EXAMINATION........ i II. SUPERFICIAL DISSECTIONS........ 12 III. THE LIMB IN SECTION......... 28 IV. THE BONES�FRACTURES AND EXOSTOSES .... 41 V. THE JOINTS............ 85 VI. TENDONS, TENDON SHEATHS, LIGAMENTS, AND BURS-fli . 130 VII. THE NERVES............ 157 VIII. THE BLOOD AND LYMPH VESSELS....... 189 MUSCLES OF THE HIND LIMB........ 215

			b



		x ILLUSTRATIONS Facing- plate Page XVIII. The Hock............112 XX. Bursas: and Sheaths in Relation to the Bones . . . . -132 XXI. Posterior Tibial Nerve and Cunean Tendon . . . . .152 XXII. Seats of Peroneal Tenotomy and Anterior Tibial Neurectomy . 156 XXIII. Obturator and Anterior Crural Nerves ...... i6₂ XXIV. Anterior Tibial Neurectomy (Upper Seat) . . . . . .182 XXV. Anterior Tibial Neurectomy (Lower Seat) . . . .184 XXVII. Aneurism of External Iliac Artery . .......194 XXVIII. Metatarsal Region, showing Arteries, Tendons, Ligaments, Bones, &c. 200



		THE HIND LIMB CHAPTER I SUPERFICIAL EXAMINATION In the region of the hip the first point which strikes an observer is the marked prominence indicating the position of the underlying external angle of the ilium. The lower the condition of the animal the more prominent does this elevation become. It is frequently and erroneously indicated by laymen as the position of the hip joint, and owing to its great prominence and exposed situation is the most common seat of fracture connected with the pelvis. It may be fractured by the animal falling on its broadside, since in accidents of this kind it is the part of the body which comes most forcibly into contact with the ground. Fracture of it is also very commonly due to the animal's being carelessly led or driven through a doorway. When fracture occurs the severed piece is usually displaced in the downward direction, and remains in the position to which it has been displaced on account of the action of the muscles which are attached to it, namely, the anterior arm of the superficial gluteal, the tensor vagina? femoris, and the internal and external oblique muscles of the abdomen. In this position, however, union to the main portion of the ilium usually occurs by ossification, but occasionally a false joint ^may be formed by the union taking place through the formation of fibrous tissue. In the former case the fracture has little effect upon the action and working ability of the animal, but has a marked effect A



		SUPERFICIAL EXAMINATION 3 trochanter. Two slight and elongated elevations are seen to converge and meet at the third trochanter. These elevations are due to the underlying arms of the superficial gluteal muscle. Running obliquely downwards and forwards behind the imaginary line indicating the direction of the femur are three elevations which are caused by the bellies of the three divisions of the triceps abductor femoris or biceps femoris muscle. The most anterior of the three bellies takes a course which is almost exactly parallel to that taken by the femoral axis, whilst the remaining two take courses which approach progressively nearer the vertical direction. An imaginary line connecting the external angle of the ilium and the summit of the great trochanter will, with the axis of the femur, form sides including an angle which is mainly filled by the quadriceps extensor cruris muscles. The normal bulk of these muscles should be carefully noted, since there is a marked falling away in this region in advanced cases of paralysis of the anterior crural nerve. A delicate sheet-like muscle runs from the angle of the haunch almost vertically downwards to be inserted into the fascia of the thigh. This is the tensor vagina? femoris muscle. Attention should next be directed to the region of the stifle joint, and the first point which strikes one here is the prominence in front of the joint caused by the patella. The bone should be carefully manipu- lated, its outline mapped out, and its vertical movement on the trochlea of the femur demonstrated to the observer's satisfaction by taking the limb up and flexing and extending the joint. In this manner also the lips of the trochlea may be made more apparent to the touch. On the anterior aspect of the patella a broad flattened tendon should be found. This is the tendon of the quadriceps or crural muscles, the action of which is transmitted to the limb through the medium of the straight ligaments of the patella. Below the patella is a transverse indentation. This invites most careful observation, since a symptom of several affections of the stifle



		4 THE SURGICAL ANATOMY OF THE HORSE joint is a filling up of this depression. The external lateral ligament of the stifle will be found to take a course downwards to the head of the fibula, which will be felt as a slight hard elevation at a distance of one inch below the femoro-tibial articulation. The three straight ligaments are felt below the patella running to their attachments into the anterior tuberosity of the tibia. In front of the head of the fibula is a powerful tendon, which if followed upwards will be found to be inserted between the outer condyle of the femur and the external lip of the trochlea. This is the tendon which is common to the extensor pedis muscle and the tendinous or superficial portion of the flexor metatarsi. The tendon is succeeded by a prominent belly, which forms a well-marked and rounded elevation at the front of the tibial region. This elevation is due chiefly to the underlying extensor pedis muscle, deeply seated to which is the flexor metatarsi. The outline of the extensor pedis is easily visible, since it forms a prominent surface marking, and manipulation is not necessary to define it. Running in a vertical direction parallel to the elevation formed by the extensor pedis is another elevation which indicates the course of the peroneus muscle. This muscle arises from the external lateral ligament of the stifle, from the head of the fibula, and the aponeurotic septum between it and the deep flexor of the digit. The elevation formed by the peroneus muscle is not so prominent as is that formed by the extensor pedis, as its belly is much less bulky and is not so well developed. The surface of the extensor pedis is convex in the longitudinal direction and markedly so from side to side, whereas the surface of the peroneus is much more flattened. Between the two elevations just described is a vertical depression into which the anterior tibial nerve dips. This nerve may be distinctly felt as it crosses the outer surface of the peroneus muscle obliquely prior to its disappearing between the two muscles. A little lower down the musculo-cutaneous branch of the anterior tibial nerve crosses the



			� 41

		Plate IV. Superficial Dissection (continued). Hind Limb (right) Outer aspect.�15. Superior annular band. 17. Middle annular band. 19. Inferior annular band. 20. Tendon of gastrocnemius. 21. Large metatarsal artery. 22. Tendon of perforatus playing over summit of tuber calcis. 23. Tendon of peroneus. 24. Extensor brevis. 25. Branch of large metatarsal artery 26. Perforatus tendon below hock 27. Tendon of extensor pedis. 28. Tendon of perforans. 29. Outer small metatarsal bone. 30 Suspensory ligament 31. Terminal filament of external saphenous nerve. 32. External metatarsal vein. 33. Large metatarsal bone. 34. Unnamed artery descending with plantar nerve. 35. Button of outer small metatarsal bone. 36 and 39. External plantar nerve. 37. External digital artery. 38. Communicating branch from internal ulantar nerve 40. External digital vein. 41. Anterior digital nerve. 42. Middle digital nerve. 43. Perpendicular artery of pastern. 44- Posterior digital nerve. 45. Plexus of veins or, external surface of lateral cartilage. 46. Coronary cushion. 47. Sensitive lamina;. N.B.� The external metatarsal vein usually emerges from the venous arch near the fetlock slightly lower down than represented in the plate.



		SUPERFICIAL EXAMINATION 5 peroneus muscle. In some animals this nerve may also be felt beneath the skin and fascia. It takes a direction across the superficial aspect of the muscle downwards and forwards, which approaches nearer the vertical than that taken by the anterior tibial nerve. A large branch is given off by this nerve for the supply of the peroneus muscle, and the nerve, much reduced in size, continues its downward course along the line of the ^aPposition of this muscle with the extensor pedis. During this part ^of its course, however, the nerve is more deeply seated, is wedged in between the two muscles, and cannot be felt in an examination such as We are now making. The depression just mentioned is of great importance, since it is the seat of the operation of anterior tibial neurectomy. The belly of the extensor pedis will be found to be succeeded by a tendon which passes beneath one of the annular bands at the inferior extremity of the tibia, and plays over the front of the hock slightly to the outer side of the middle line. Its subsequent course will be traced later, as also will the tendon of the peroneus, which runs in a vertical direction and plays through a groove on the outer side of the external malleolus of the tibia. The back of the thigh is very fleshy, owing to the enormous bulk of the hamstring muscles, which extend to a much lower level than in man, so that in the horse the back of the stifle is well protected, and the posterior common ligament of the joint is deeply seated. The muscles of the hamstring also clothe and protect the great sciatic nerve with its accompanying vessels. The inner aspect of the thigh will be found to be very flat, and the bone is here also clothed by muscles which are the adductors of the limb. Those which form the superficial layer, and are subcutaneous, are the sartorius anteriorly and the gracilis posteriorly. The gracilis occupies about four-fifths of the area described, and its surface is quite flat, whilst the skin covering the sartorius is slightly raised, since the muscle forms an elevation which runs downwards and backwards.



		6 THE SURGICAL ANATOMY OF THE HORSE Behind the gracilis is another elevated area due to the underlying semimembranosus muscle. Running obliquely upwards and forwards across the gracilis is the internal saphena vein, a vessel of large calibre which is formed by the union of the upward continuations of the outer and inner metatarsal veins. It dips in between the sartorius and gracilis about the junction of the upper and middle thirds of their line of apposition, and empties itself ultimately into the femoral vein. The application of pressure will cause the vessel to be raised, when its course becomes much more evident. It is occasionally adopted as a seat for the operation of venesection. In front of the saphena vein is the saphena artery, a long and slender vessel which follows the course of the vein, and divides into two branches which accompany the outer and inner roots of the saphena vein. Anteriorly placed to the saphena artery again is the internal saphena nerve. This arises from the anterior crural nerve at the brim of the pelvis, and emerges from between the sartorius and gracilis with the artery and vein. It will be further dealt with in the chapter on nerves. The slight depression which indicates the position of the interstice between the sartorius and gracilis should be carefully examined, particularly in its upper part, which is the situation of the deep inguinal lymphatic glands. In this region the glands cover the under- lying femoral vessels, and they become very evident in cases of lymphangitis. If the hand be now passed down the inner aspect of the limb, it will be ascertained that the inner surface of the tibia is immediately sub- cutaneous, and it will also be found that the subcutaneous bone is widest above and gradually tapers as we descend. Manipulation of this part is of importance in the diagnosis of deferred fracture, of which particular injury the shaft of the tibia is the most common seat. The very important region of the hock is next to be considered.



			Superficial Dissection (continued).
		Plate VI.	Superficial Dissection (continued).
		Plate VI.

	Hind Limb (right), Inner aspect.�22. Plantar nerves. 23. Sigmoid curve of posterior tibial artery. 24. Summit of tuber calcis covered bv perforatus tendon. 25. Superior annular band. 26. Cutaneous branch of posterior tibial nerve passing oyer seat of spavin. 27- Cunean tendon. 28. Tendon of perforans leaving tarsal sheath. 29. Internal metatarsal vein passing upwards to form anterior root of internal saphena vein. 30. Perforatus tendon. 31. Inferior annular band. 32- Internal plantar nerve. _ _33; Extensor
pedis tendon ₃₄. Unnamed artery descending with plantar nerve. 35- Large metatarsal bone 36. Communicating branch from internal plantar nerve. ₃₇. Suspensory ligament. 38. Internal digital vein. 39- Internal small metatarsal bone. 40. Internal digital artery. _4I. Button of small metatarsal bone. 42. Internal plantar nerve. 43- Inner branch of suspensory ligament. 44. Posterior digital nerve. ₄₅. Anterior digital nerve 46 Tendon of perforans leaving ring formed by perforatus. 47. Middle digital nerve. 48. Os suffraginis. ₄₉. Perpendicular artery of pastern. $0. Sensitive lamina:. 51. Plexus of veins on lateral cartilage. 52. Coronary cushion. N.B.�The internal metatarsal vein usually emerges from the venous arch near the fetlock slightly lower down than represented in the plate.



		SUPERFICIAL EXAMINATION 7 Assuming that the " near " hock is the one to be examined, the student should first stand with his face directed towards the horse's head, and should pass the palmar aspect of his right hand over the front of the hock. In this manner the tracing of the tendon of the extensor pedis ^may be made, and the tendon may be caused to stand out prominently " the hock be flexed. The main portions of the tendons of the flexor ^rnetatarsi muscle may also be traced to their insertion into the anterior ace of the upper extremity of the large metatarsal bone, though these tendons are not quite so evident as is that of the extensor pedis. On the inner aspect of the joint two prominent elevations are seen, the upper of which is caused by the internal malleolus of the tibia, ^and the one below it by the well-defined tubercle on the inner surface °f the astragalus. The tubercle just mentioned varies considerably in size in different animals. The size of the tubercle is not a matter °f great consequence, provided both tubercles are alike and well defined. The tubercle is only in rare and advanced cases involved in spavin, and when such happens it loses its well-defined outline, and in its place we have a diffused enlargement. Running almost vertically across the internal malleolus of the tibia ^1S a faint depression which, when we come to study the deeper anatomy of the joint, we shall find gives passage to a tendon, namely, that of the flexor accessorius muscle. The usual seat of spavin* is on the antero-internal aspect of the inferior third of the joint, and the touch of the fingers should be care- fully educated to appreciate the exact normal conformation of this area. ■This is only brought about by constant practice, since the difference in ^external contour presented by a normal hock and many hocks affected ^Wlth spavin is so slight that it is only appreciable to a sense of touch ^hich has been cultivated to a considerable degree of delicacy. Below the elevation caused by the tubercle of the astragalus a slight ⁿ°^rizontally disposed elevation is found which curves round from the ^anterior to the internal aspect of the joint. This elevation corresponds



		8 THE SURGICAL ANATOMY OF THE HORSE to the anterior and inner surfaces of the scaphoid bone. Immediately below this is a faint depression which runs parallel to the elevation just described. This depression is situate between the most prominent portion of the anterior and inner surfaces of the scaphoid above, and the anterior surface of the cuneiform magnum together with the inner surface of the cuneiform parvum below. These surfaces of the cunei- form bones cause another horizontal elevation, which, however, is not so well-defined as the one already described, being simply a faint upheaval of the surface. It differs moreover from the first-mentioned elevated area, inasmuch as it is not continuous, being interrupted by a little depression which is placed between the two cuneiform bones. This depression therefore is disposed vertically. The horizontal elevation corresponding to the two cuneiform bones forms the superior boundary of a second transverse depression which is not so apparent as that already described, and which is bounded inferiorly by the prominent upper extremity of the large metatarsal bone and the head of the inner small metatarsal bone. This depression is crossed at right angles by the one which has been mentioned as running vertically, and the latter is continued in the downward direction between the prominences which indicate the position of the head of the inner small metatarsal bone and the large metatarsal bone. The subjacent osseous structures to which the various elevations mentioned correspond, and their disposition one to the other will be easily understood by a reference to Plate XVIII. Running inwards and slightly downwards from the front of the joint to the small cuneiform bone is a broad, flat tendon, which can be felt only when a considerable amount of pressure is applied. This is the cunean division of the tendon of the flexor metatarsi muscle. The insertion of the cunean tendon will be found to be in line with a horny excrescence which is confined to the skin and which is called the chestnut. The branch from the superficial tendon of this muscle may be felt,



		SUPERFICIAL EXAMINATION 9 though less distinctly, to run outwards and with a slight downward inclination to its insertion into the cuboid bone. The outer aspect of the hock should now be examined. It will be round that there is no tubercle on the external lateral aspect of the astragalus, but a faint depression will be felt in the part which corre- sponds to the position of the tubercle on the inner lateral surface of this bone. Below the astragalus and calcis on this side of the joint is the cuboid, and inferiorly to this bone the head of the external small metatarsal bone will be easily located; and the observer should make himself quite iamiliar with its normal size, since an abnormally large head of the small metatarsal bone frequently leads to considerable confusion and constitutes the condition designated as false curb. The outer aspect of the left hock is best examined with the left hand, with one's back directed towards the patient's head. If the hand be now passed down the back of the leg the bulging bellies of the gastrocnemius will be felt, and from them the succeeding tendon may be traced. From two to three inches above the point of the hock it will be ascertained that another tendon twists round that of the gastrocnemius, passing from the deeper aspect of the latter to its inner side and subsequently being placed superficially to it. This tendon is that of the superficial flexor of the digit {i.e., the flexor perforatus), and it will be found to become very much flattened out as we approach the summit of the calcis which forms what is known as the point of the hock. This is the seat of the affection known as the capped hock. At the middle ot the summit of the calcis the tendon of the perforatus leaves that of its gastrocnemius, and the latter will be found to terminate. The perforatus tendon, however, plays over the upper extremity of the bone, and between it and the bone is interposed a small synovial bursa, to facilitate the gliding movement of the tendon. The further course of the perforatus tendon may be traced, and it



		io THE SURGICAL ANATOMY OF THE HORSE will be found to run straight down the posterior border of the tuber calcis. It should be carefully noted that the surface in this region is straight, for a slight convexity of the surface of the postero-inferior aspect of the hock would most probably indicate the presence of a curb. Below the hock another tendon makes its appearance, and is easily felt to be placed immediately in front of that of the perforatus. This is the tendon of the perforans muscle, and it has resumed its former position in front of the perforatus after leaving the tarsal sheath, to pass through which it left the perforatus above the hock. Immediately below the hock on the antero-external aspect of the limb two tendons may be clearly detected as being subcutaneous. The tendon which is the nearer to the middle line is that of the extensor pedis muscle. The other is the peroneal tendon. If the course of each tendon be followed in the downward direction they will be found to become united to one another about four inches below the hock. The tendon of the peroneus should next be traced in the upward direction, when it will be found to run obliquely upwards and back- wards to gain the outer aspect of the hock joint, where it has already been followed to the groove on the external malleolus of the tibia. On the inner and outer surfaces of the metatarsal region a groove is felt which takes a vertical direction. These grooves are situate between the large and small metatarsal bones. Along part of the groove between the large metatarsal bone and the outer small metatarsal the large metatarsal artery runs, the position of which may be ascertained by the pulsation of the vessel, which can be detected without much difficulty. Tracing the vessel upwards, we find that the peroneal tendon crosses it obliquely in passing from the groove in the external tibial malleolus to its attachment to the tendon of the extensor pedis. A tiny muscle runs in front of, and parallel to the tendon of the



			B
		A	B
		A

	Plate XI.�The Innominate Bones A.�INFERIOR ASPECT i. Inferior ischiatic spine. 2. Ischiatic symphysis. 3. Obturator foramen. 4. Pubio-femoral groove. 5. Cotyloid cavity. 6. Grooves for ilio-femoral vessels. 7. Brim of pelvis. 8. Angle of croup. 9. Auricular facet. 10. Grooves for ilio-lumbar vessels. 11. Angle of haunch.

B.�LATERAL ASPECT (THE BONES INVERTED) I. Gluteal surface of ilium. 2 Shaft of ilium. 3. Cotyloid cavity 4. Superior ischiatic spine. 5. Ischium. 6. Inferior ischiatic spine. 7. Tuber ischii. 8. Obturator foramen. 9. Pubio-femoral groove. 10. Brim of pelvis.



		CHAPTER II SUPERFICIAL DISSECTIONS OUTER ASPECT OF LIMB Such a dissection is represented in Plates III. and IV. The Bones Near the upper extremity of the limb, the patella is seen to bulge prominently forwards (5). To its anterior face is attached the tendon of insertion of the quadriceps muscles (1) and also the external straight patellar ligament. Below the patella is the anterior tuberosity of the tibia, which is continued downwards into the ridge of bone known as the tibial crest. The crest disappears as we descend the limb, since it gradually subsides to blend with the anterior face of the bone. The external condyle of the femur (2) is placed behind the patella, and is partially concealed by a flat piece of muscular tissue which is the inferior extremity of one of the divisions of the biceps femoris muscle. Inferiorly placed to this condyle, but separated from it by the outer semilunar cartilaginous disc, is the external tuberosity of the tibia, of which only the anterior portion is visible. It is separated from the anterior tuberosity by a well-marked notch, through which the tendon common to the extensor pedis and the superficial tendinous portion of the flexor metatarsi plays. Descending from this tuberosity in a vertical direction for a



			B
	A		B
	A

		Plate XII.�Right Femur

A.�ANTERIOR ASPECT 1. Summit of great trochanter (insertion of one of tendons of middle gluteus muscle). 2. Insertion of deep gluteus into inner face of convexity. 3. Outer surface of convexity (seat of synovial bursa beneath tendon of middle gluteus). 4. Articular head. 5. Crest of great trochanter, into which is inserted tendon of middle gluteus, which pla}-s over outer suiface of convexity. 6. Sulcus in head. 7. External or third trochanter, to which is attached tendon of superficial gluteus muscle. 8. Internal or small trochanter, into which are inserted the psoas magnus and iliacus muscles. 9. Anterior surface (this and the lateral surfaces are clothed by the quadriceps extensor cruris muscle). 10. Inner ridge of trochlea. 11. Outer ridge of trochlea. 12. Groove of trochlea. B.�POSTERIOR ASPECT I. Summit of great trochanter. 2. Articular head. 3. Trochanteric ridge. 4. Sulcus in head. 5. Trochanteric fosfa. 6. Internal or small trochanter. 7. Tubercle for attachment of slip from biceps femoris. 8. Roughening for insertion of quadratus femoris. 9. Ridges for insertion of adductor muscles. 10. Nutrient foramen. II. Roughening for insertion of pectineus. 12. Groove for femoral vessels. 13. Supra- condyloid fossa. 14. Supracondyloid crest. 15 and 16. External and internal condyles. 17. Intercondyloid groove.



		SUPERFICIAL DISSECTIONS 13 distance of about twelve inches in the living animal, bone is again found to be superficially placed, and here we have the ex- ternal malleolus of the tibia, which presents a well-marked vertical groove for the passage of the tendon of the peroneus muscle (23). The outer lateral surface of the astragalus is situate below the malleolus, and behind these two elevations is the prominent tuber calcis. This is concealed by the tendon of the perforatus, which is here very much flattened (22). Inferiorly to the calcis is the cuboid, and below this again we have the head of the outer small metatarsal bone (29). Extending obliquely downwards and forwards from the head is the body of the last-mentioned bone, which gradually tapers from above downwards. It terminates inferiorly in the rounded nodule termed the button, which is placed about two inches above the fetlock joint (35). The button is easily located in the living animal, since between it and the large metatarsal bone there is a slight interval, and ^tne button springs a little upon the application of pressure. In front of the small metatarsal bone is a groove down which the large metatarsal artery runs. The groove is bounded anteriorly by the large metatarsal bone. The greater part of the lateral surface °t this bone is visible in the plate, and in the living animal is immediately subcutaneous (33). The sesamoid bones are concealed from view by the broadened- °^ut perforatus tendon and the lateral division of the suspensory hgament, but below the fetlock a considerable portion of the lateral surface of the sufFraginis is represented, as is also the tuberous lateral aspect of its inferior extremity. The Ligaments *he 'External Straight Patellar Ligament (ya).�This ligament runs ^wnwards in a vertical direction from the anterior surface of the r ^eHa to the outer division of the anterior tuberosity of the tibia. In



			B

		Plate XIII.�The Right Tibia A.�POSTERIOR ASPECT I. Spine of tibia. 2 and 3. External and internal tuberosities. 3a. Tubercle for attachment of posterior crucial ligament. 4. Depression for head of fibula. 5. Depression for accommodation of popliteus muscle. 6. Nutrient foramen. 7. Tubercle for insertion of popliteus muscle. 8. Ridges for attachment of flexor perforans muscle. 9. Groove for passage of tendon of flexor accessorius. 10. Groove for tendon of peroneus muscle. 11. External malleolus. B.�ANTERIOR ASPECT 1. Insertion of anterior crucial ligament. 2. Spine of tibia. 3 and 4. External and internal tuberosities. 5. Notch for passage of common tendon of extensor pedis and superficial division of flexor metatarsi. 6. Groove in anterior tuberosity. 7. Articulation for head of fibula. 8. Outer division of anterior tuberosity. 9. Crest of tibia. 10 and n. Internal and external malleoli.



		14 THE SURGICAL ANATOMY OF THE HORSE the Plate the ligament is relaxed and dips inwardly between the patella and the tibia, owing to the fact that the former is placed at the lower end of the trochlea since the quadriceps muscles are relaxed. The External Lateral Ligament of the Stifle (j).�This is repre- sented as being attached to the external surface of the outer condyle of the femur above and to the head of the fibula below. The fibres of the peroneus muscle are seen to arise from this ligament. At the front of the hock the three transverse fibrous bands are shown which hold the tendons playing over this part in position (15, 17, and 19). The Great Suspensory Ligament (30) first becomes visible about three inches below the head of the small metatarsal bone, the upper portion of the ligament being concealed by the greater thickness of this bone. Above the fetlock the ligament divides into two parts, and the outer division may be followed obliquely across the outer aspect of the fetlock- joint to the front of the limb, where it becomes united to the tendon of the extensor pedis, as in the fore limb. The Muscles and Tendons The Quadriceps Extensor Cruris (1).�These are the muscles which clothe the anterior and .lateral surfaces of the shaft of the femur. Only the outer half of the inferior third of these muscles is shown, since the limb has been severed across the line of division between the middle and inferior thirds of the femur. The muscles are inserted on the anterior face of the patella. They are the great extensors of the stifle joint, their action being transmitted to the limb through the medium of the straight ligaments of the patella. They are supplied by the anterior crural nerve, and are the muscles which are affected in crural paralysis. The Biceps Femoris (3).�This muscle is in three divisions : one is inserted into the patella, another into the tibial crest, and the third into



		SUPERFICIAL DISSECTIONS 15 the fascia of the leg. Only about three inches of the insertion of the first-mentioned part are represented, the rest of the muscle having been removed to display the parts beneath it. The Gastrocnemius (10).�This muscle has two heads : the outer is represented in the Plate, and it arises from the outer lip of the supra- condyloid fossa. The two heads unite, forming the prominent bulging mass which corresponds to the calf in the human leg. This mass is succeeded by a powerful tendon, which descends in a vertical direction ^to the summit of the tuber calcis, where it obtains insertion in the depression separating the two elevations on this bone. The gastroc- nemius is a powerful extensor of the hock joint, and is also a slight flexor of the stifle. It is supplied by the internal popliteal nerve. The Flexor Perforates (22 and 26).�Deeply seated to the gastroc- nemius is the flexor perforatus, which is therefore concealed from view. It arises from the depth of the supracondyloid fossa, and runs down the lirnb in front of the gastrocnemius. At the summit of the calcis its tendon is superposed to that of the latter muscle and forms a cap. It gives ofF a slip of insertion to the tuber calcis on either side and takes a course straight down the back of the calcis, where it is concealed by the thick layer of fascia represented in the Plate. Below the hock the tendon is plainly visible, and its edge has been displaced slightly backwards to display more effectively the structures which lie in front of it. At the fetlock it forms the tube through which the tendon of the flexor perforans passes, and it ultimately obtains insertion into the os coronas. This muscle is an extensor of the hock, and a flexor of the fetlock and pastern joints. It is supplied by the internal popliteal nerve. The Flexor Perforans (16).�On this aspect of the limb a con- siderable portion of this muscle is visible. It is placed between the peroneus muscle in front and the gastrocnemius behind, occupying most of the space between these two muscles from the stifle to the hock. It arises from the external tuberosity and posterior surface of the shaft of



			Plate XV �Tarsal Bones of Ambush II.

		A.�RIGHT TARSUS I. External malleolus of tibia. 2. Calcis. 3. Cuboid. 4. External small metatarsal bone. 5. Large metatarsal. 6. Internal malleolus of tibia. 7. Tubercle of astragalus. 8. Ridge on scaphoid. 9. Transverse groove between scaphoid and two cuneiform bones. 10. Ridge on cuneiform magnum, n. Transverse groove between cuneiform bones above and large and inner small metatarsal bones below. B.�LEFT TARSUS 1. Internal malleolus of tibia. 2. Astragalus. 3. Tubercle of astragalus. 4. Ridge of scaphoid. 5. Groove between scaphoid and two cuneiform bones 6. Ridge on cuneiform magnum. 7. Groove between cuneiform bones above and large and inner small metatarsal bones below. 8. Large metatarsal bone. 9. External malleolus of tibia. 10. Calcis. n. Cuboid. 12. External small metatarsal.



		16 THE SURGICAL ANATOMY OF THE HORSE the tibia, from the head of the fibula, and from the tibio-fibular inter- osseous membrane. The muscular portion keeps in close relationship to the peroneus throughout its course, and its tendon disappears through the tarsal sheath, where it glides over the supero-posterior aspect of the body of the calcis to the inner side of the tuber. The tendon again makes its appearance below the hock as it leaves the sheath. It is plainly visible owing to the slight displacement of the tendon of the per- foratus (28). It continues its course down the limb between the suspensory ligament in front and the perforatus tendon behind, and along its edges run the plantar nerves and vessels. It next plays through the ring formed by the perforatus, leaves the ring below the fetlock, and becomes ultimately inserted into the semilunar crest of the pedal bone. The perforans is an extensor of the hock and a flexor of the fetlock, pastern, and corono-pedal joints. It is supplied by the internal popliteal nerve. The Peroneus Muscle (18).�This muscle arises from the external lateral ligament of the stifle, from the outer tuberosity of the tibia, and from the head of the fibula. The tendon of origin is plainly visible, and is succeeded by a well-defined elongated muscular belly, which is represented throughout its extent. Its inferior tendon commences above the hock. It then passes along the groove on the external malleolus, over the large metatarsal artery, and under the most inferior of the three annular bands to become united to the tendon of the extensor pedis from three to four inches below the hock (23). The peroneus muscle assists the extensor pedis, and is supplied by the musculo-cutaneous division of the external popliteal nerve. The Extensor Pedis (11).�This muscle is also represented from its origin to its insertion : it arises in common with the tendinous division of the flexor metatarsi from the pit which is placed between the external femoral condyle and the outer lip of the trochlea.



		Plate XVI.�The Bones of the Hocks in Sheather's Case A. Left hock (inner aspect). B. Right hock (inner aspect). C. Right hock (outer aspect). D. Left hock (outer aspect). Reproduced, with permission, from The Veterinary Record



		SUPERFICIAL DISSECTIONS 17 The tendon passes through the deep notch between the anterior and external tuberosities of the tibia, and is immediately succeeded by the belly of the muscle. The latter is even better defined than is that of the peroneus, and forms a prominent fusiform mass, which causes a well- marked elevation of the skin in this region. The inferior tendon commences just above the hock, and passes beneath all three annular bands. It then takes a course down the limb, slightly to the outer side of the middle line. It is joined below the hock by the tendon of the peroneus and below the fetlock by both branches of the suspensory ligament. As it passes over the fetlock it is related to the anterior common ligament, but at the pastern-joint it takes the place of the anterior liga- ment and gives support by its deep face to the synovial membrane of the joint as in the fore limb. This muscle is a flexor of the hock and an extensor of the fetlock and inter-phalangeal joints. It is also a slight extensor of the stifle. It is supplied by the anterior tibial nerve. The 'Extensor Brevis (24).�This small muscle is placed between the tendons of the peroneus and extensor pedis. It arises from the astragalus and os calcis, and is inserted into the tendon of the extensor pedis, near where the peroneal tendon becomes united to the latter. It assists the extensor pedis, and is supplied by the anterior tibial nerve. THE BLOOD-VESSELS The Arteries No vessels are represented in the upper half of the limb. Below the hock the Large Metatarsal Artery (21) makes its appearance after having passed beneath the extensor brevis and the tendon of the peroneus. It runs down the limb in the groove between the large metatarsal and outer small metatarsal bones. Just above the c





			Plate XVII.�The Stifle-Joint�Bones, Ligaments and Cartilages A.�POSTERIOR ASPECT

		i. Supracondyloid crest. 2. Supracondyloid fossa. 3. Inner condyle of femur. 4. Outer lip of supracondyloid fossa. 5. Femoral coronary ligament. 6. Outer condyle. 7. Posterior crucial ligament. 8. Anterior ditto. 9. Inner semilunar cartilage. 10. External lateral ligament. n. Internal ditto. 12. Outer semilunar cartilage. 13. Special tubercle, to which internal crucial ligament is attached. 14. Posterior coronary ligament of outer cartilage. 15. Tubercle for insertion of popliteus muscle. 16. Head of fibula. 17. Nutrient foramen of tibia. 18. Depression for accommodation �of popliteus muscle. 19. Ridges from which perforans muscle arises. B.�ANTERIOR ASPECT 1, 3, and 4. External, middle, and internal straight patellar ligaments. 2. Patella. 5. External condyle. 6. Inner lip of trochlea. 7. Outer ditto. 8 and 9. Inner and outer semilunar cartilages, 10 and 11. Internal and external lateral ligaments. 12. An- terior tuberosity of tibia. 13. Head of fibula. 14. Crest of tibia.



		18 THE SURGICAL ANATOMY OF THE HORSE button of the small metatarsal it disappears through the interval between this bone and the large metatarsal to gain the back of the limb, where it divides between the two divisions of the suspensory ligament into the external and internal digital arteries. The External Digital Artery (37).�This appears behind the outer division of the suspensory ligament and takes a vertical course across the outer aspect of the fetlock-joint, being behind the digital vein, and in front of the plantar nerve on the outer edge of the perforans tendon. Near the middle of the os suffraginis it gives off the perpendicular artery (43) of the pastern, which runs forwards along this bone and divides into ascending and descending branches. The digital artery divides on the inner aspect of the lateral cartilage into the plantar and preplantar (ungual) arteries. The Veins The External Digital Vein (40).�This is formed by the union of vessels which drain the plexuses of the foot. One of these plexuses is represented, namely, that on the outer aspect of the external lateral cartilage (45). This plexus communicates with that on the deep face of the cartilage through the cartilage itself. The vein thus formed runs upwards in front of the corresponding digital artery, crossing the anterior and middle digital nerves. Above the fetlock it disappears from view, since it dips in between the suspensory ligament and perforans tendon, to assist in the formation of the venous arch which is here placed. From this arch three veins are given off, namely, the external, middle, and deep metatarsals. The External Metatarsal Vein (32) leaves the arch, runs outwards, and appears on the edge of the perforans tendon. It takes an upward course on the tendon in front of the small unnamed artery (34), which descends from the tarsal arterial arch, and disappears with the tendon through the tarsal sheath.





		Plate XVIII.�The Hock A.�ANTERO-INTERNAL ASPECT OF LEFT HOCK�SUPERFICIAL MARKINGS I. Tendo-Achill.es. 2. Elevation formed by internal malleolus. 3. Summit of tuber calcis. 4. Position of ridge on scaphoid. 5. Position of groove between scaphoid and cuneiform magnum. 6. Position of groove between cuneiform magnum and large metatarsal bone. 7. Ridge on cuneiform magnum. 8. Tubercle or inner aspect of astragalus, g. Depression (seat of bog spavin). 10. Elevation formed by external malleo.us. B.�THE RIGHT HOCK�BONES AND LIGAMENTS�ANTERO-INTERNAL ASPECT i Tibia. 2. External malleolus. 3. Internal malleolus. 4. Inner ridge of astragalus. 5. Internal lateral ligament. 6. Mesial ridge at inferior extremity of tibia. 7. Inner surface of astragalus. 8. Mesial furrow on astragalus, g. Tubercle of astragalus. 10. Outer ridge of astragalus. 11. Ridge formed by scaphoid. 12. Astragalo-metatarsal ligament. 13. Cuneiform parvum. 14. Groove between scaphoidand cuneiform magnum. 15 Groove between cuneiform magnum and cuneiform parvum. 16. Ridge on cuneiform magnum. T7. Head of inner small metatarsal bone. 18. Groove between cuneiform magnum and large metatarsal bone. ig. Ridge at upper extremity of large metatarsal bone. C.�BONES OF LEFT HOCK�INNER ASPECT i. Summit of tuber calcis. 2. Tibia. 3. Groove on tuber calcis forming outer boundary of tarsal sheath. 4. Internal malleolus. 5. Body of calcis. 6. Inner ridge of astragalus. 7. Cuboid. 8. Tubercle of astragalus, g. Cuneiform parvum. 10. Scaphoid. 11 and 13. External and internal small metatarsal bones. 12. Cuneiform magnum. 14. Large metatarsal bone.



		SUPERFICIAL DISSECTIONS 19 Above the hock it will be seen on the inner aspect of the limb, where it forms the smaller of the two roots of the internal saphena vein.

			The Nerves The External Saphena Nerve (6).�This is a branch of the great sciatic nerve. It is given off from the latter at a point which varies from two to six inches from the place where it dips between the two heads of the gastrocnemius muscle. It passes along the external aspect of the outer head of the muscle named, and receives a reinforcing branch (8) from the external popliteal nerve. This branch leaves the external popliteal above the stifle, and runs downwards and backwards across the gastrocnemius muscle. The external saphena nerve continues its course down the limb in front of the tendo-achilles, and gives off cutaneous branches, which are distributed on the outer lateral aspect of the hock. The nerve usually terminates in the skin about midway between the hock and fetlock, but occasionally it is continued much lower down the limb, to be distributed to the skin covering the phalanges. The External Popliteal Nerve (5).�This nerve is a branch of the great sciatic, from which it is given off almost immediately after the latter leaves the pelvic cavity. It runs obliquely downwards and forwards, and passes between the biceps femoris and the outer head of the gastrocnemius. The former muscle having been removed, the nerve is first visible in the Plate where it lies on the gastrocnemius. Immediately below the point of detachment of the communicating branch to the external saphena nerve, this nerve gives off its peroneal- cutaneous branch. The latter nerve runs along the inferior border of the biceps femoris, and splits up into a number of branches, which are distributed to the skin in front of the stifle and the leg. The peroneal- cutaneous nerve being more superficially placed, is not represented in the Plate.