196 THE MUSCLES. 



Action. — Abducts the thigh ai;cl 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, f). 



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, /') about five millimeters broad. The tendon 

 curves proximad and passes beneath the gracilis tendon (Fig. 



91, /') 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, t), the integument, a mass of fat, and distad with the gas- 

 trocnemius (Fig. 92, J) and popliteus (Fig. 92, /'). Caudal 

 surface with the integument. Medial su^^face with the semi- 

 membranosus (Fig. 90, /) and distad with the integument of 

 the lower leg. 



Action. — Flexor of the shank. 



M. semimembranosus (Figs. 90 and 91, /; Fig. 92, h). — 

 A thick prismatic muscle lying along the ventral (or cautlal) 

 side of the thigh between the semitendinosus {j) and the gracilis 

 (Fig. 91, b). 



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, Ji and //'), one of which (//) lies laterad and caudad of the 

 other. The two portions pass to the medial side of the knee. 

 The caudal portion {Ji) 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 insertion 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. 



