MUSCLES OF THE LOWER EXTREMITIES. 221 



aponeurotic obturator membrane, presenting at its 

 upper part the opening for the obturator vessels and 

 nerve. From the inner surface of this membrane 

 arises the obturator internus muscle ; it also arises 

 from the posterior surface of the rami of the ischium 

 and pubes and the margins of the obturator foramen. 



Insertion Passes out of the pelvis by the lesser sacro- 

 sciatic foramen, and is inserted into the upper border 

 of the great trochanter. 



Nerves Small sciatic and sacral plexus. 

 GEMELLUS SUPERIOR. 



Origin A bundle of muscular fibres above the 

 tendon of the obturator internus; arises from the 

 margin of the lesser sacro-sciatic foramen and spine 

 of ischium. 



Insertion Upper border of great trochanter, with 

 tendon of obturator internus. 



Nerve Sacral plexus. 

 GEMELLUS INFERIOR. 



Origin Similarly arranged as the gemellus superior ; 

 arises from tuberosity of ischium. 



Insertion Great trochanter with obturator internus. 



Nerve Sacral plexus. 

 OBTURATOR EXTERNUS. 



Origin Outer surface of obturator membrane, rami 

 of pubes and ischium. 



Insertion Digital fossa. 



Nerve Obturator, from lumbar plexus. 

 QUADRATUS FEMORIS. 



Origin Outer surface of tuberosity of ischium. 



Insertion Quadrate line on femur. 



Nerve Sacral plexus. 

 BICEPS. 



Origin Two heads, the long head from lower facet 



