INDIVIDUAL VARIATION.--None of significance. =_M. Flexor Cruris Medialis_= (M. semimembranosus), Figs. 12, 13, 14, 15, 16, 17, 20E _T. pallidicinctus_ GENERAL DESCRIPTION AND RELATIONS.--Most posterior muscle on medial surface of thigh; long and strap-shaped; bounded anteriorly by M. adductor profundus; posteroproximal corner of latter medial to anteroproximal part of M. flexor cruris medialis; bounded laterally by Mm. caudofemoralis (proximally) and flexor cruris lateralis (distally); anteroproximal corner adjacent to posteroventral corner of M. flexor ischiofemoralis and lateral to extreme posteroproximal corner of M. adductor superficialis; distal end tendinous, extending into proximal part of shank; bounded medially by M. gastrocnemius pars interna and laterally by Mm. gastrocnemius pars media and plantaris. ORIGIN.--The muscle arises by a wide flat tendon from a narrow line on the lateral surface of the ischium dorsal to the ventral ischiatic tubercle. INSERTION.--The wide flat tendon attaches to a narrow line on the medial surface of the proximal part of the tibiotarsus a short distance anterior to the proximal part of M. plantaris and deep to M. gastrocnemius pars interna; the proximal end attaches immediately anterior to the distal end of the medial collateral ligament. Part of the common tendon of Mm. flexor cruris lateralis and femorocruralis fuses with the lateral surface of the tendon of M. flexor cruris medialis, inserting in common with it. INNERVATION.--A branch of the middle tibial division of the sciatic nerve passes deep to both heads of M. caudofemoralis and enters the anterior part of M. flexor cruris medialis. INDIVIDUAL VARIATION.--In several legs, the anterior edge of the proximal part fits into a deep longitudinal groove in the posterior edge of the proximal part of M. adductor superficialis; the two muscles fuse slightly at this point. _T. cupido_ INDIVIDUAL VARIATION.--In two legs, the extreme posterior end of the origin is from the pubis. In two others, the proximal end is separated by a slight gap from M. adductor superficialis. The nerve arises from the posterior (rather than middle) tibial division in one leg. _P. p. jamesi_ DIFFERENCES FROM TYPICAL _T. pallidicinctus_.--The origin is wider; the posterior third to half of the origin is fleshy. The entire origin is from a strongly curved line, the middle part of which attaches to the ventral edge of the ischium posterior to the ventral ischiatic tubercle. The insertion is wider. The insertional tendon attaches posterior (rather than anterior) to the distal end of the medial collateral ligament; the proximal end of the insertion attaches to the articular capsule (fig. 20E). The insertional tendon is shorter; as a result, the common tendon of Mm. flexor cruris lateralis and femorocruralis fuses with the distal end of the fleshy belly (instead of the tendon) of M. flexor cruris medialis.