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 vertebre. The 
first is the largest; it joins the lumbosacral cord to form the 
great sciatic nerve (N. ischiadicus) (2) and the superior (2) and 
inferior (7) 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 (7), 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, 7; Fig. 163, 7).-—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 (6) and gluteus minimus (5) and ventrad 
of the latter, and reaches the medial surface of the tensor fasciz 
late, which it innervates. In its course it sends branches to 
the gluteus medius, gluteus minimus (5), and gemellus 
superior. 
2. N. gluteus inferior (Fig. 162, 7; Fig. 163, 7).—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, 2). 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). 
