THE PERIPHERAL NERVOUS SYSTEM. 399 



divides into several branches, which innervate the adductor 

 femoris, adductor longus, pectineus, and gracilis. 



D. SACRAL NERVES AND SACRAL PLEXUS (Fig. 162). 

 A large band passes caudad from the sixth and seventh lumbar 

 nerves to connect with the sacral nerves ; this constitutes the 

 so-called lumbosacral cord. The sacral nerves are three in 

 number. Their dorsal rami pass dorsad out of the two pos- 

 terior sacral foramina and the foramen caudad of the sacrum, to 

 the muscles and skin dorsad of the sacrum. The ventral rami 

 pass from the two anterior sacral foramina and from the fora- 

 men between the last sacral and first caudal vertebrae. The 

 first is the largest; it joins the lumbosacral cord to form the 

 great sciatic nerve (N. ischiadicus) (//) and the superior (7) and 

 inferior (/) gluteal, and sends a branch caudad to connect with 

 the second sacral. The second and third sacral nerves are 

 small ; they unite with the connecting branch from the first to 

 form a network from which arises the pudendus (/), cutaneus 

 femoris posterior (), hemorrhoidalis inferior (in), and a small 

 branch to the great sciatic (/z). 



The nerves arising from the sacral plexus are the following: 



1. N. gluteus superior (Fig. 162, i; Fig. 163, /). The 

 superior gluteal nerve arises from the lumbosacral cord and the 

 first sacral nerve ; it passes dorsad in the notch between sacrum 

 and ilium, caudolaterad of the first anterior sacral foramen, 

 curves over the dorsal border of the ilium between the gluteus 

 medius and pyriformis muscles (Fig. 163, 7), passes between 

 the gemellus superior (e) and gluteus minimus (s) and ventrad 

 of the latter, and reaches the medial surface of the tensor fasciae 

 latae, which it innervates. In its course it sends branches to 

 the gluteus medius, gluteus minimus (s), and gemellus 

 superior. 



2. N. gluteus inferior (Fig. 162,7; Fig. 163, z). A small 

 nerve from the lumbosacral cord and the first sacral nerve. 

 It passes dorsocaudad, lying on the dorsal surface of the great 

 sciatic nerve (Fig. 162, //). After leaving the pelvis by the 

 great sciatic notch it divides beneath the pyriformis (Fig. 

 163, 7) into two branches; one goes to M. caudofemoralis (4), 

 the other to M. gluteus maximus (3). 



