THE PERIPHERAL NERVOUS SYSTEM. 403 
plantar surface of the heel, and divides into two branches, the 
medial and the lateral plantar nerves. 
(1) N. plantaris medialis. — The medial plantar nerve 
passes along the medial border of the flexor brevis digitorum 
and divides into two branches. One passes to the medial 
(second) digit, supplying both sides; the other supplies the 
third digit in the same way. Both send branches to the fibrous 
pad on the sole of the foot. 
(2) N. plantaris lateralis.— The lateral plantar nerve 
passes laterad across the tendon of the flexor longus digitorum 
to its lateral edge. At about the proximal end of the metatarsi 
it divides into two branches. The lateral branch passes distad 
to the ventral surface of the fifth digit. The medial branch 
passes beneath the tendon of the flexor longus digitorum and 
transversely across the interossei; it divides into numerous 
tendons which innervate the interossei and other short muscles 
of the sole of the foot. 
4. N. pudendus (Fig. 162, /; Fig. 112, 8, page 265).— 
This arises (Fig. 162, 7) from the sacral plexus caudad of the 
great sciatic nerve. It has two roots, one from the second 
sacral, one from the third, and it may also receive a small 
accession from the great sciatic nerve (#) three or four centi- 
meters caudad of the origin of the latter. It passes at first 
dorsolaterad, laterad of the coccygeus muscle, then curves 
mediad toward the anus. It divides into two branches: one 
passes to the base of the penis, sends twigs into the compressor 
urethra muscle, and passes onto the dorsal surface of the penis. 
This branch is N. dorsalis penis; it extends with the artery of 
the same name to the glans. The second branch of N. puden- 
dus (N. hemorrhoidalis medius) passes to the anus and inner- 
vates the muscles and other structures about the caudal end of 
the rectum. In the female, branches of N. pudendus supply 
the urogenital sinus and adjacent structures (Fig. 112, 8). 
5. N. cutaneus femoris posterior (Fig. 162, 4; Fig. 
163, £).—This arises from the sacral plexus, its roots coming 
chiefly from the second and third sacral nerves, and passes 
caudodorsad, at first in close connection with N. pudendus. 
It then accompanies the posterior gluteal artery and vein, sends 
