370 NEUROLOGY, OR ANATOMY OF NERVOUS SYSTEM 



The muscular branch to the obturator intcrnus crosses the 

 spine of the ischium and enters the small sciatic foramen to 

 the inner surface of the muscle. It also supplies the superior 

 gemeUus. That to the quadratus femoris runs beneath the 

 tendon of the obturator internus, and supplies also the inferior 

 gemellus and hip-joint. Lastly, the pyriformis receives several 

 filaments from the sacral nerves previous to the formation 

 of the plexus. 



The superior gluteal emerges above the pyriformis, through 

 the great sciatic notch, and divides into an upper branch, 

 to the gluteus medius, and a lower, larger branch, which sup- 

 plies both the medius and minimus, piercing the latter to end 

 in the tensor vaginae femoris. It arises from the lumbosacral 

 cord and first sacral nerve. 



The inferior gluteal emerges below the pyriformis, dividing 

 into numerous branches for the gluteus maximus. It sends 

 a branch to join the small sciatic. It arises from the lumbo- 

 sacral cord and first and second sacral nerves. 



The small sciatic is purely sensor; it appears below the 

 pyriformis, and runs beneath the gluteus maximus upon the 

 great sciatic nerve, thence beneath the fascia lata, which it 

 pierces just below the knee. It communicates with the external 

 saphenous nerve. It arises from the second and third sacral 

 nerves. 



Branches. Cutaneous, to the calf of the leg, to the inferior 

 gluteal region, and to the back and inner part of the thigh 

 (femoral cutaneous)', and the inferior pudenda! nerve, derived 

 below the tuber ischii, to the scrotum or labium majus and 

 the skin of the upper and inner part of the thigh. 



The perforating cutaneous nerve, from the fourth sacral 

 nerve, pierces the great sciatic ligament and turns over the 

 lower border of the gluteus maximus to supply the skin over 

 its lower part. 



The pudic nerve emerges between the coccygeus and pyri- 

 formis, and crosses the ischial spine to re-enter the pelvis by 

 the lesser sacrosciatic foramen. It divides, in the ischiorectal 

 fossa, into the inferior hemorrhoidal, perinea], and dorsal nerve 

 of the penis or clitoris. 



The inferior hemorrhoidal supplies the external sphincter 

 (in part) and the skin of the back part of the perineum, com- 

 municating with the pudendal and perineal nerves. 



