182 
ANATOMY OF THE HORSE. 
Action .—The two divisions of this muscle will operate dif¬ 
ferently. The anterior or superior one will assist the rectus and 
vasti in extending* the thigh; but the posterior one will contri¬ 
bute towards its flexion. They w ill both co-operate in abducting 
the limb; also in rotating* it inwards — the hock at the time 
turning outw r ards. 
SEMITENDINOSUS. 
SEMIMEMBRANOSUS. 
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ADDUCTOR TIBIALIS. 
Isckio-tibialis Internus . 
Situation .—Posterior side of the haunch and thigh. 
Attachment .—Superiorly, to the postero-lateral part of the spine 
of the sacrum; to the two or three uppermost bones of the coccyx ; 
and to the antero-inferior side of the tuberosity of the ischium. 
Inferior!y, to the superior and antero-internal part of the tibia; 
directly opposite to the attachment of the lower head of the biceps 
abductor and tibial aponeurosis. 
Relations .—Posteriorly, with the faschia and skin; anteriorly, 
with the tuberosity of the ischium, os femoris, and gastrocne- 
mii; externally, w ith the biceps; internally, with the adductor 
tibialis. 
Structure .—This is a long cylindroid muscle, composed of 
two parts, one coming from the sacrum, the other from the 
ischium; both of which are united below the tuberosity. The 
superior attachments are both fleshy and tendinous. From the 
inferior proceeds an aponeurotic expansion, contributing towards 
the tibial faschia. 
MUSCLES OF THE THIGH AND LEG. 
These muscles are invested and confined down in their places 
by the crural or tibial faschia, which is in part an extension from 
the faschia lata, and in part a production from those femoral 
muscles whose tendons or aponeuroses descend upon the leg; 
such as the adductor magnus, biceps, and adductor tibialis. 
The muscles themselves (those now under consideration), being 
collected together in two packets or parcels, separate and dis¬ 
tinct from each other, the crural faschia admits of an anterior 
and a posterior portion ; one investing the muscles in the ante¬ 
rior crural region, the other in the correspondent posterior re¬ 
gion. The former has for its principal places of attachment the 
patella ; the upper and lower ends, tubercle, and spine of the 
tibia ; and the anterior annular and lateral ligaments of the 
hock; in front of which it is continuous with the tendinous va¬ 
ginae, formed for the passage of the extensor tendons: on the 
outer side this faschia sends a broad process inward, between 
the extensor pedis and peroneus, which is fixed to the body of 
