INDIVIDUAL VARIATION.--In two thirds of the legs, the proximal part of the insertion is fleshy rather than tendinous. In one leg, the middle part of the insertional tendon splits into two sheets, one attaching anterior to and one attaching posterior to the distal end of the medial collateral ligament. The nerve may arise from the posterior tibial division (two legs), from the middle tibial division (one leg), or as an independent division of the tibial nerve (three legs). In one leg, the nerve perforates the lateral part of M. flexor ischiofemoralis. =_M. Caudofemoralis_= (M. piriformis), Figs. 12, 13, 14, 15, 16, 20J _T. pallidicinctus_ GENERAL DESCRIPTION AND RELATIONS.--Posterior to proximal part of shaft of femur and deep to M. extensor iliofibularis; posterior part deep to M. flexor cruris lateralis; bounded medially by Mm. flexor ischiofemoralis (dorsally), flexor cruris medialis (posteriorly), and adductor superficialis (anteroventrally); anterior end distal to anterior end of M. flexor ischiofemoralis; two distinct heads--pars iliofemoralis and pars caudifemoralis; _pars iliofemoralis_ dorsal to pars caudifemoralis; posteroventral corner of former overlapped by latter; pars iliofemoralis wider and much shorter than pars caudifemoralis; extreme posterior end of pars iliofemoralis fused to overlying posteroproximal aponeurosis of M. extensor iliotibialis lateralis; small part of ventral edge sometimes fused with underlying tendinous posteroproximal corner of M. flexor cruris medialis; entirely fleshy except for small triangular tendinous area along dorsal margin at point where branch of middle tibial division of sciatic nerve passes deep to muscle; _pars caudifemoralis_ long, thin, narrow, and strap-shaped; overlapping posteroventral corner of ischium; posterior end of fleshy belly narrowed and forming long slender tendon passing into caudal musculature; anterior end forming short narrow tendon fused to deep surface of ventral edge of pars iliofemoralis relatively near insertion; tendon continuous to insertion; fleshy anterodorsal corner of pars caudifemoralis slightly overlapped by ventral edge of pars iliofemoralis; some form of connection usually present between anterior part of M. caudofemoralis pars caudifemoralis and dorsal end of raphe between Mm. flexor cruris lateralis and femorocruralis, most often consisting of narrow weak tendon.