MUSCULAR SYSTEM OF THE RED HOWLING MONKEY 131 



the axis, pass in front of the articular capsule, reinforce it and are 

 attached to the anterior aspect of the lateral tibial condyle in front of 

 the insertion of m. biceps (fig. 39). 



M. vastus medialis occupies the medial side of the ventral com- 

 partment of the thigh , separated by the median intermuscular septum 

 from the adductor group of muscles. It arises from the whole extent 

 of this aponeurotic partition and on the femiu" from the linea aspera 

 over the upper half of its medial lip up to the intertrochanteric line, 

 where its origin extends a little onto the anterior face of the bone (fig. 

 40). The fibers of the vastus medialis are oriented distolaterally. Those 

 close to the femoral axis are inserted directly on the medial edge of the 

 deep terminal tendon of the rectus femoris, while fibers further away 

 from that axis become tendinous and pass in front of the articular 

 capsule to end on the ventral border of the medial tibial condyle and 

 the patellar tendon (fig. 37). 



M. vastus intermedins is entirely covered by the other three 

 components of the quadriceps. Origin is from the entire ventral surface 

 of the femur, except on those areas from which the other two vasti 

 arise (fig. 40). Its fibers run distally and are partially split at their 

 distal third by an incomplete and frontaUy arranged cleavage. In this 

 manner those arising from the proximal two-thirds of the bone cover 

 those coming from the distal third. Both portions remain connected 

 along their medial borders where the cleavage plane is not well defined. 

 I regard the covered portion as the m. articularis genu. The vastus 

 medialis attaches to the whole upper border of the patella deep to the 

 terminal tendons of the rectus femoris. Its deeper fibers are continuous 

 with the fibrous ones of the articular capsule. The findings of Sirena 

 (1871) in Aloualta jusca call for no special comment. 



Nerve supply: The vasti are innervated by the femoral nerve. Its 

 branch to vastus lateralis is particularly large. 



Function : Extension of the knee. 



Comparative anatomy of the prepelvic coxofemoral group. — 

 Accessible information about this group of muscles in the five cebids 

 under consideration is found only in Hill's work (1960, 1962). There 

 seem to be little differences among them. The sartorius muscles of the 

 woolly (Hill, 1962), woolly spider (Hill, 1962) and capuchin monkey 

 (Hill, I960) appear to be similar to that of Alouatta. Hill (1962) 



Figure 40. — Muscular attachments of the femur (1, m. iliopsoas; 2, m. quadratus femoris; 

 3, m. vastus medialis; 4, m. adductor longus; 5, m. adductor brevis; 6, m. ischiofemoralis; 

 7, m. ischiocondyloideus; 8, m. gastrocnemius, caput mediale; 9, m. gastrocnemius, 

 caput laterale; 10, m. biceps femoris, caput breve; 11, m. vastus intermedius; 12, m. 

 vastus lateralis; 13, m. pectineus; 14, m. gluteus maximus; 15, m. scansorius; 16, m. 

 gluteus minimus; 17, m. gluteus medius; 18, m. piriformis; 19, fossa trochanterrca; 20, m. 

 popliteus). 



