162 U.S. NATIONAL MUSEUM BULLETIN 2 73 



stout, is attached to the peroneal process of metatarsale V together 

 with m. peroneus brevis (m. abductor ossis metatarsi V), the other 

 tendon, less powerful but long, crosses the fifth metatarsophalangeal 

 articulation, pierces the flexor digiti quinti and ends on the fibular 

 base of the first phalanx of toe V. Sirena (1871) found it to be a slender 

 muscle on whose tendon many fibers of the flexor digiti quinti ended. 

 He did not describe an abductor ossis metatarsi V. 



Nerve supply: Lateral plantar nerve. 



Function: Abducts the fifth toe. 



SUPERFICIAL SERIES, DEEP LAYER 



Mm. lumbricales: They are four round, small, but long muscles. 

 The first originates from the tibial side of the perforating tendon to 

 toe II the second, third, and fourth lumbricals arise from the adja- 

 cent sides of the perforating tendons to the four lateral toes. The 

 increasingly reduced fleshy bellies form fine tendons which cross on 

 the plantar side of the deep transverse metatarsal ligaments and then 

 end by fusing with the tibial half of the dorsal expansions of their 

 respective toes. This blending takes place over the jjroximal half of 

 the first phalanx. The lumbricales are essentially the same in Alouatta 

 fusca except that an additional attachment to the proximal phalanx 

 of each of the last four toes is indicated (Sirena, 1871). 



Nerve supply: The first lumbrical was innervated by the first 

 common digital branch of the medial plantar nerve in both sides of 

 the female, and in two of the males. Lumbricales to the third, fourth, 

 and fifth toe were supj^lied by the deep branch of the lateral plantar 

 nerve in these three specimens. All four lumbricales were innervated 

 by the deep branch of the lateral plantar nerve in the remaining male. 



Function: Flexion of the metacarpophalangeal joint. 



DEEP SERIES, SUPERFICIAL LAYER 



This layer is invariably represented by an adductor to the hallux 

 and contrahentes to the second, fourth, and fifth toes. 



M. adductor hallucis: This is a massive and roughly triangular 

 muscle in the central compartment of the foot (fig. 48). Its base lies 

 along the central axis and corresponds to its origin. The belly thickens 

 considerably toward the insertion. 



Caput obliquum arises from the third cuneiform and the proximal 

 half of a sagittal aponeurotic septum attached along the middle of 

 the third metatarsal. Fibers from the cuneiform are initially fibrous 

 and oriented distomedially, those from the septum are fleshy and 

 increasingly transverse in direction. This head is fused along its 

 dorsomedial border with the fibular head of the flexor hallucis, the 

 two muscles having a firm common and fleshy insertion on the fibular 



