196 THE MUSCLES. 
Action.—Abducts the thigh and helps to extend the shank. 
M. semitendinosus (Fig. 90, 7).—A long slender muscle 
on the ventral (caudal) border of the thigh, between the semi- 
membranosus (z) and the biceps femoris (Fig. 68, 2). 
Origin from the apex of the tuberosity of the ischium 
beneath the origin of the biceps femoris. The muscle passes 
to the medial side of the shank and ends in a thin but strong 
tendon (Fig. 92, 2’) about five millimeters broad. The tendon 
curves proximad and passes beneath the gracilis tendon (Fig. 
91, 8) to its 
Insertion into the crest (dorsal border) of the tibia one or 
two centimeters from its proximal end. 
Relations.—Lateral surface with the biceps femoris (Fig. 
68, 2), the integument, a mass of fat, and distad with the gas- 
trocnemius (Fig. 92, 7) and popliteus (Fig. 92, 2). Caudal 
surface with the integument. Medial surface with the semi- 
membranosus (Fig. 90, z) and distad with the integument of 
the lower leg. 
Action.—Flexor of the shank. 
M. semimembranosus (Figs. 90 and 91, z; Fig. 92, 2).— 
A thick prismatic muscle lying along the ventral (or caudal) 
side of the thigh between the semitendinosus (7) and the gracilis 
(Fig. 91, 4). — 
Origin by short tendon-fibres from the caudal border of the 
tuberosity and the ramus of the ischium. The muscle mass is 
divided throughout most of its length into two portions (Fig. 
92, # and h’), one of which (Z’) lies laterad and caudad of the 
other. The two portions pass to the medial side of the knee. 
‘The caudal portion (2’) ends in a strong flat tendon five milli- 
meters broad, the 
Insertion of which is into the medial surface of the femur 
on the medial epicondyle, at the middle of its distal border and 
into the adjacent medial surface of the tibia behind the lateral 
ligament. 
The dorsal part has its zzser¢éon into the distal one and 
one-half to two centimeters of the ridge which is continued 
from the medial epicondyle of the femur onto the shaft; and 
nto the sesamoid bone of the medial epicondyle. 
