The =posterior gluteal nerve= (N. glutæus caudalis) is derived mainly
from the sacral roots of the lumbo-sacral plexus (Figs. 451, 526). It
divides into two trunks which emerge above the great sciatic nerve. The
upper nerve passes backward on the sacro-sciatic ligament and divides
into branches which enter the two heads of the biceps femoris; it
supplies a branch to the posterior part of the middle gluteus, and a
nerve which turns around the posterior border of the latter and enters
the posterior head of the superficial gluteus. The inferior nerve runs
downward and backward on the sacro-sciatic ligament and divides into the
=posterior cutaneous nerve= and muscular branches which supply the
semitendinosus. The former (N. cutaneus femoris caudalis) passes through
the biceps femoris, emerges between that muscle and the semitendinosus a
little below the level of the tuber ischii, and ramifies subcutaneously
on the outer and posterior surfaces of the hip and thigh (Fig. 525).
[Illustration: