164 U.S. NATIONAL MUSEUM BULLETIN 2 73 



fibers from tlie plantar surface of cuneiforme I. These shortly become 

 fleshy and pass distally along the i)eroneal side of metatarsale I. The 

 bell}' is covered here by the caput tibiale and by the oblique adductor, 

 with which it appears to form a single body. Insertion is by fleshy 

 fibers together with the oblique head of the adductor hallucis on the 

 lateral side of the first metatarsophalangeal capsule. The fibular head 

 is fixed to the first metatarsal by fleshy fibers attached all along the 

 shaft of this bone. Sirena (1871) states that the flexor hallucis brevis 

 in Alouatta fusca is just like that of man. 



Nerve supply: Both heads of the muscle are innervated by the 

 medial plantar nerve. 



Function: Flexion of the first metatarsophalangeal joint and 

 adduction of the metatarsal. 



Mm. inter ossei pedis: These are arranged into four dorsal and 

 three plantar muscles (fig. 45). The former have a double origin from 

 the adjacent metatarsals between which they lie; each of the latter 

 arises only from the metatarsal of the toe upon which it acts. The 

 caput tibiale of the first dorsal interosseous is small and its fleshy 

 fibers come from the base of the first metatarsal on its fibular side. It 

 soon joins the larger caput fibulare which has a more extensive origin 

 from the entire tibial side of the base and shaft of metatarsale II. The 

 muscular belly forms a tendon over the tibial side of the second meta- 

 tarsophalangeal joint. It lies here covered by the fibers of the dorsal 

 extensor expansion that reach the capsule of the joint. Insertion takes 

 place by joining that expansion and partly on the tibioplantar base of 

 the first phalanx of II. The origin of the second dorsal interosseous is 

 from the proximal half of the dorsal border in the shaft of metatarsale 

 II and the entire tibial half of the shaft and base of metatarsale III. 

 The tendon formed by its belly at the tibial side of the third metatarso- 

 phalangeal joint is also largely joined to the overlying dorsal extensor 

 expansion ; the rest is inserted on the tibioplantar base of the proximal 

 phalanx of III. For the third dorsal interosseous the origin is from 

 most of the dorsal border of metatarsale III. Insertion is by a trans- 

 versely compressed tendon on the fibuloplantar base of the first phalanx 

 in toe III and by most of its fibers on the corresponding dorsal e.\- 

 tensor expansion of III. The fourth arises from the proximal half of 

 the dorsal border of metatarsale V and the entire fibular half of the 

 shaft and base of metatarsale IV. Insertion takes place partially on 

 the fibuloplantar base of the first phalanx of toe IV and into the 

 dorsal expansion. 



Origin of the first plantar interosseous is from the peroneal half of 

 the shaft and base of metatarsale II. Its fleshy fibers run distally and 

 form a transversely flattened tendon wliose insertion is on the fibular 

 half of the base in the first phalanx of toe II deep to the ending of m. 

 contrahens II. At this point its tendon fuses with those fibers of the 



