GENERAL DESCRIPTION AND RELATIONS.--Short and broad; posterior to distal part of femur; deep to Mm. extensor iliofibularis and vastus lateralis pars postica; bounded posteriorly by M. flexor cruris lateralis, medially by Mm. adductor superficialis and adductor profundus, and distally by M. gastrocnemius pars media; fused to a variable degree with the latter (in some cases these two muscles fused firmly together, appearing as single muscle); distal and medial to proximal end of M. flexor perforatus digiti IV. ORIGIN.--The muscle arises fleshily (thin proximally, thick distally) from the posterior surface of approximately the distal half of the femur between the posterior and posterolateral intermuscular lines. The ventral end is continuous with the origin of M. gastrocnemius pars media, adjacent (medial) to the origin of M. vastus lateralis pars postica, and adjacent (lateral) to the insertions of Mm. adductor superficialis and adductor profundus. INSERTION.--The attachment is to the tendinous raphe in common with M. flexor cruris lateralis (which see). INNERVATION.--One or two tiny branches come off the tibial nerve near the distal end of the main trunk of the sciatic nerve, pass anteriorly deep to the peroneal nerve, and penetrate the lateral surface. INDIVIDUAL VARIATION.--In two legs, the branch of the medial division of the tibial nerve which supplies M. gastrocnemius pars media sends a twig to the lateral surface of the distal end of M. femorocruralis (in addition to the usual innervation). _T. cupido_ INDIVIDUAL VARIATION.--None of significance. _P. p. jamesi_ DIFFERENCES FROM TYPICAL _T. pallidicinctus_.--The muscle is much wider, extending farther proximally on the femur. INDIVIDUAL VARIATION.--None of significance. =_M. Gastrocnemius_=, Figs. 12, 13, 15 _T. pallidicinctus_