144 U.S. NATIONAL MUSEUM BULLETIN 2 73 



fascia between it and the other two muscles of the compartment, the 

 extensor hallucis longus forms a fusiform belly between them and is 

 covered by the extensor digitorum longus and tibialis anterior. It 

 follows the latter into the superior extensor retinaculum where its 

 fleshy fibers give rise to a long and narrow tendon which runs on the 

 dorsum of the foot medial to the belly of m. extensor hallucis brevis 

 (fig. 45). It now crosses superficially over the two tendons of the 

 tibialis anterior before entering its own compartment of the inferior 

 extensor retinaculum. On reaching the metatarsophalangeal joint of 

 the hallux, the tendon sends dorsal tendinous expansions at each side 

 toward the plantar aspect of the foot, the rest continues as a single 

 tendon to be inserted on the dorsal base of the last hallucal phalanx. 

 Sirena (1871) calls it m. extensor hallucis proprius and says it is as in 

 man. 



Nerve supply : A muscular ramus of n. peroneus profundus. 



Function: It extends the two phalanges of the hallux. 



M. extensor digitorum longus: This long muscle of the anterior 

 crural compartment is bound medially by both the tibialis anterior 

 and the extensor hallucis longus, laterally by the anterior inter- 

 muscular septum and the fibula. It arises from most of that septum, 

 the crural fascia, and the intermediate two quarters of the medial 

 fibular surface, very near the anterior margin of the bone, as most 

 of this surface is taken up by the origins of the muscles in the posterior 

 compartment of the leg. Additional fibers come from the interosseous 

 membrane and in large number from the tendinous fascia which 

 develops between the extensor digitorum longus and the tibialis 

 anterior. The muscle runs distally on the lateral side of the latter, 

 and the two almost completely cover the extensor hallucis longus. It 

 changes into two strong tendons when approaching the superior 

 extensor retinaculum under which they pass together with the other 

 two members of the anterior division (fig. 45). The paired tendons 

 cross the lateral and proximal part of the foot where they are held 

 down by a powerful tendinous retinaculum. They now run toward 

 the dorsum of the foot and expand as four flat bands united by fibrous 

 tissue and contained within a division of the deep dorsal fascia which 

 covers the bellies of the extensor digitorum brevis. Upon reaching the 

 metatarsophalangeal joints of the last four toes each band sends an 

 expansion along both sides of the corresponding articulation. These 

 reach the transverse intermetatarsal ligaments with which they fuse 

 and receive distally the insertions of the interossei and lumbricals. 

 The rest of the band proceeds distally over the toe, intimately con- 

 nected to the underlying interphalangeal capsules before ending on 

 the dorsal base of the corresponding last phalanx. There are no differ- 

 ences with the muscle described by Sirena (1871) in Alouatta Jusca. 



