Relations.—Outer surface with the superficial fascia and a few fibres of the cutaneus maximus; distad with the biceps femoris ([Fig. 68], t). Cranial border with the gluteus maximus; caudal border with the biceps femoris. Inner surface with the tenuissimus ([Fig. 90], g), the gluteus maximus, the abductor caudæ internus, and with the obturator internus ([Fig. 90], e); distad with the vastus lateralis.
Action.—Abducts the thigh and helps to extend the shank.
M. semitendinosus ([Fig. 90], j).—A long slender muscle on the ventral (caudal) border of the thigh, between the semimembranosus (i) and the biceps femoris ([Fig. 68], t).
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], i′) about five millimeters broad. The tendon curves proximad and passes beneath the gracilis tendon ([Fig. 91], b) 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 gastrocnemius ([Fig. 92], j) and popliteus ([Fig. 92], k). Caudal surface with the integument. Medial surface with the semimembranosus ([Fig. 90], i) and distad with the integument of the lower leg.
Action.—Flexor of the shank.
M. semimembranosus ([Figs. 90] and [91], i; [Fig. 92], h).—A thick prismatic muscle lying along the ventral (or caudal) 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], h and h′), one of which (h′) lies laterad and caudad of the other. The two portions pass to the medial side of the knee. The caudal portion (h′) ends in a strong flat tendon five millimeters 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.