MUSCULAR SYSTEM OF THE RED HOWLING MONKEY 163 



side of the capsule of the first metatarsophalangeal joint. There is a 

 sesamoid bone near this ending Avithin the fibers of the combined 

 bundles. 



The caput transversum begins by fleshy fascicles from the distal 

 half of the same sagittal septum and the deep transverse metatarsal 

 ligament of the second interspace. They run transversely toward 

 their insertion along the fibular side of the two hallucal phalanges. 

 Sirena notes the strong development of the muscle, particularly the 

 transverse head. 



Nerve supply: A branch from the deep ramus of the lateral plantar 

 nerve. 



Function: Abduction of the hallux. 



Mm. contrahentes digitorum pedis: Three such muscles are present 

 (fig. 48). Those for toes IV and V are lateral to the axial origin of 

 m. adductor hallucis; that of the fourth toe is covered proximally by 

 the belly of contrahens V and that of the second toe entirely by the 

 adductor hallucis. These three muscles arise from the sagittal septum 

 of metatarsale III by aponeurotic fibers whose fleshy continuations 

 form their respective fusiform and plantarly flattened beUies. The 

 origin extends proximally to the fibrous sheath of the peroneus longus 

 and in the lateral half of the tarsus to the lateral cuneiform bone. 

 Insertion is on the medial base of the proximal phalanx in toes IV and 

 V, and on the lateral side in toe II. Sirena (1871) describes contra- 

 hentes to toes II, IV, V and an adductor to the haUux with comparable 

 origins and insertions to those described here. 



Nerve supply: The deep branch of the lateral plantar nerve 

 travels deep to the three muscles and sends branches which enter 

 them on their deep surface. 



Function: They adduct the lateral and medial toes toward the 

 third digit. 



DEEP SERIES, DEEP LAYER 



M. flexor hallucis hrevis: Caput tibiale (fig. 48) is a well-developed 

 muscle arising by long tendinous fibers from the plantar surface of 

 the second cuneiform and the sheath of the long peroneal tendon. 

 They pass medially toward the base of the first metatarsal and give 

 origin to the fleshy fibers of the muscular belly. This runs distaUy 

 over the plantar and tibial side of metatarsale I covered by the tendon 

 of the abductor hallucis, to which some of its fibers are attached. 

 Insertion takes place together with that tendon on the tibial base of 

 the first hallucal phalanx. Its fibers are closely connected to the 

 underlying capsule of the first metatarsophalangeal joint. 



Caput fibulare is entirely associated with the oblique head of the 

 adductor hallucis, of which it appears to form a third part (fig. 48) 

 differen liable only by its nerve supply. The origin is by tendinous 



