MUSCULAR SYSTEM OF THE RED HOWLING MONKEY 123 



Alouatta, and the spider monkey as observed by Straus (unpublished), 

 but I cannot be sure of this due to Robertson's rather unclear descrip- 

 tion of these muscles. Straus (unpubUshed) studied them in the left 

 side of one juvenile Cebus malitiosus (= Cehus albifrons). He found 

 four dorsals and four ventrals. Of the last, the one on the radial 

 side of the second intermetacarpal space he regards as merely a 

 subdivision of the second dorsal. Only the first and the third dorsal 

 are bicipital and the fourth ventral has an additional proximal origin 

 from the hamate process and the transverse carpal ligament. All 

 the interossei contribute definite expansions to the extensor 

 aponeurosis. 



Muscles of the Lower Extremity 



Dorsal Musculature 

 Coxofemoral Group 



PREPELVIC 



M. iliopsoas: This muscle is formed by the iliacus and the psoas 

 major, each with a separate origin but with a common insertion 

 (fig. 20). 



M. psoas major is a fleshy thick column extending along the side 

 of the lumbar spine, across the pelvis major to the lesser trochanter 

 of the femur. The muscle arises by a series of fleshy arcades anchored 

 to all of the intervertebral disks of the lumbar region. In all specimens 

 the more caudal fibers invariably originate also from the body of the 

 last lumbar vertebrae. The costal processes of the third to the fifth or 

 sixth vertebrae contribute fleshy digitations to the dorsal surface of 

 the psoas major. The large fusiform belly lies in the angle formed 

 by all the lumbar bodies and their costal processes. It has two frontal 

 cleavages; the ventral and cranial one allows for the formation and 

 passage of the lateral femorocutaneous nerve, the dorsal and distal 

 is traversed by the femoral nerve and its roots. 



M. iliacus is formed by abundant fleshy fascicles coming from 

 the entire iliac fossa and inner lip of the crest. Its bundles converge 

 toward and join the dorsal surface of the psoas major. The combined 

 iliopsoas fibers end on a strong tendon which begins within the muscle 

 while it is still in the pelvis. The tapering musculotendinous belly 

 forms the lateral floor of Scarpa's triangle and curves dorsally under 

 the neck of the femur to a robust tendinous attachment on the tip of 

 the trochanter minor. Sirena (1871) states that the origin of psoas 

 major extends up to the body of L 1. 



Nerve supply: The iliopsoas receives branches from L IV and 

 L V (fig. 35). 



275-199 O - 68 - 9 



