Comparison.—No significant differences noted among the species studied.
Musculus semimembranosus (Figs.[ 3],[ 4],[ 5]).—This straplike muscle passes along the posteromedial surface of the thigh. The origin is semitendinous along a line on the ischium, from a point dorsal to the middle of the ischiopubic fenestra to the posterior end of the ischium, and from a small area of the abdominal musculature posterior to the ischium. The insertion is by means of a broad, thin tendon on a ridge on the medial surface of the tibia immediately distal to the head of this bone. The tendon of insertion passes between the head of the pars media and pars interna of the m. gastrocnemius and is fused with the tendon of the m. semitendinosus.
Action.—Flexes crus.
Comparison.—No significant differences noted among the species studied.
Musculus biceps femoris (Fig.[ 2]).—Long, thin, and somewhat triangular, this muscle lies on the lateral side of the thigh just underneath the m. iliotibialis. Its origin is from a line along the anterior and posterior iliac crests underneath the origin of the m. iliotibialis. Anterior to the acetabulum the origin is aponeurotic, and the edge of this aponeurosis passes over the proximal end of the femur. The origin posterior to the acetabulum is fleshy. The most anterior point of origin is difficult to ascertain but it lies near the center of the anterior iliac crest. The most posterior point of origin is immediately dorsal to the posterior end of the ilioischiatic fenestra. Behind the knee the fibers of this muscle converge to form the strong tendon of insertion which passes through the biceps loop, under the tendon of origin of the m. flexor perforatus digiti II, and inserts on a small tubercle on the posterolateral edge of the fibula at the point of the tibia-fibula fusion.
The biceps loop is tendinous and the distal end attaches to a protuberance on the posterolateral edge of the femur at the proximal edge of the external condyle. The proximal end attaches to the anterolateral edge of the femur immediately proximal to the distal end of the loop, which extends posterior to the femur. The distal arm of this loop is connected with the tendon of origin of the m. flexor perforatus digiti II by a strong tendon.
Action.—Flexes crus.
Comparison.—No significant differences noted among the species studied.
Musculus ischiofemoralis (Fig.[ 3]).—Short and thick, this muscle arises directly from the lateral surface of the ischium between the posterior iliac crest and the ischiopubic fenestra. The area of origin extends to the posterior edge of the ischium. The insertion is tendinous on the lateral surface of the trochanter opposite the insertion of the m. iliotrochantericus medius.
Action.—Moves femur posteriorly and rotates it in this direction.