150 U.S. NATIONAX, MUSEUM BULLETIN 2 73 



form thick muscular bundles ^^hich pass behind the iliofemoral 

 articular capsule and are inserted at the bottom of the trochanteric 

 fossa (fig. 40). 



Nerve supply: It is supplied by the same nerve as the gemellus 

 superior. 



M. quadratus femoris: This muscle, about twice as large as either 

 of the two gemelli, is found deep in the limit between the ghiteal 

 and dorsal regions of the thigh (fig. 44). It arises by fleshy fibers 

 from the femoral surface of the ischial body deep to the common 

 origin of the biceps and semitendinosus (fig. 36). The quadratus 

 femoris passes laterally covering the trochanter minor and is inserted 

 by fleshy fibers over a triangular area of the proximal part of the 

 femoral shaft bound by the lesser trochanter, the intertrochanteric 

 crest, and the insertion of m. gluteus maximus on the outer line 

 of the linea aspera (fig. 40). It is entirely covered by the long head 

 of the biceps which is here associated \vith the semitendinosus as 

 these two muscles leave the ischial tuberosity on their way to the 

 back of the leg. The sciatic trunk and its long branch for the ham- 

 string muscles pass distally between the biceps and semitendinosus 

 superficially and the quadratus femoris on a deeper plane. The 

 caudal border of the muscle is related to the upper border of the 

 adductor brevis. 



Nerve supply: It is mnervated by the cootinuation of the same 

 nerve which supplies the two gemelli. 



Function: These four muscles are lateral rotators and abductors 

 of the femur. 



M. biceps femoris: This muscle has a long and a short head. The 

 second belongs, on the basis of its innervation, with the postpelvic 

 group of the dorsal muscles supplied by the n. peroneus communis, 

 but I consider it here for topographical reasons. The robust caput 

 longum is found on the superficial and lateral aspect of the dorsum of 

 the thigh extending between ischium and tibia (fig. 44). The caput 

 breve lies below the middle of the thigh under cover of the long com- 

 ponent of the muscle (fig. 44). The caput longum arises in common with 

 the semitendinosus by a large fleshy mass whose fibers are fixed to the 

 femoral surface of the ischial body behind the origin of the quadratus 

 femoris and the complex of the ischiocondyloideus and semimem- 

 branosus (fig. 36). The sciatic trunk and the nerve supply of the ham- 

 string muscles separate this head from the underlying structures. A 

 Httle beyond the middle of the thigh the fibers of the biceps form a 

 transversely flat tendon which expands as it approaches the leg by 

 passing behind the knee when this is in the normal flexed position of 

 the limb. This tendon is inserted on the anterior aspect of the lateral 

 tibial condyle (figs. 38, 39) after gliding over the head of the fibula. 



