subarticular cartilage of the third interphalangeal joint. INNERVATION.--The posterior division of the tibial nerve sends a branch into the posterior edge of the medial head, then passes between the latter and the medial head of M. flexor perforatus digiti III; as it extends distally it gives off twigs to the medial surface of the medial head, to the deep surface of the lateral head, and to the deep surface of the anterolateral head. INDIVIDUAL VARIATION.--In one leg, an additional branch arises from the tibial nerve at the level of origin of the posterior division and enters the posterior surface of the medial head; a twig from this branch anastomoses with the first twig of the posterior division to the same head; a branch of the medial division joins the posterior division distal to the origin of the twigs to the medial head but proximal to the origin of the twigs to the other heads. _T. cupido_ INDIVIDUAL VARIATION.--None of significance. _P. p. jamesi_ INDIVIDUAL VARIATION.--In four legs, a tiny vinculum connects with the tendon of M. flexor digitorum longus (which see). =_M. Flexor Perforatus Digiti III_=, Figs. 13, 14, 15, 16, 17 _T. pallidicinctus_ GENERAL DESCRIPTION AND RELATIONS.--Divided into two widely separated heads--medial and anterolateral--with completely separate bellies but with common insertional tendon; small _anterolateral head_ on lateral aspect of thigh deep to M. flexor perforans et perforatus digiti II and posterior to M. flexor digitorum longus; fleshy part of head distolateral to belly of M. flexor perforatus digiti IV; fleshy part fused to lateral edge of belly of M. flexor perforatus digiti II; proximal part of head a slender ossified tendon fused to anterior edge of both fleshy and tendinous parts of anterolateral head of M. flexor perforatus digiti IV and to lateral edge of anterolateral head of M. flexor perforatus digiti II; this tendon passing deep to tendon of insertion of M. extensor iliofibularis and to peroneal nerve; large _medial head_ on posteromedial surface of thigh anterior to medial edge of M. gastrocnemius pars externa, lateral to M. gastrocnemius pars media, and medial to M. flexor perforatus digiti IV; fused to medial surface of medial head of latter and to medial edges of Mm. flexor perforatus digiti II and flexor hallucis longus; proximal end of head tendinous. ORIGIN.--The _medial head_ attaches tendinously to the medial part of the popliteal area in common with the medial head of M. flexor perforatus digiti II and with the medial edges of Mm. flexor perforatus digiti IV (medial head) and flexor hallucis longus; and is also fused to the articular capsule. The _anterolateral head_ arises in common with the anterolateral heads of Mm. flexor perforatus digiti II and flexor perforatus digiti IV (see account of latter).