THE PERIPHERAL NERVOUS SYSTEM. 393 
radialis longus. It supplies the supinator and extensor 
muscles of the forearm (brachioradialis, supinator, extensor 
carpi radialis longus, extensor carpi radialis brevis, extensor 
communis digitorum, extensor digitorum lateralis, extensor 
indicis, extensor brevis pollicis). The dorsal interosseous 
and radial nerves thus supply all the extensor muscles of 
the forearm and upper arm and the supinators (modified 
extensors). 
11. N. ulnaris (Fig. 160, 7).—The ulnar nerve arises from 
the eighth cervical and first thoracic and accompanies the 
brachial artery (g) and median nerve (e¢) through the upper 
arm. It does not pass through the supracondyloid foramen, 
but curves over the dorsal end of the medial epicondyle of the 
humerus within the short division of the medial head of the 
triceps, and reaches the dorsal border of the forearm. In the 
forearm (Fig. 161, @) it lies beneath the flexor carpi ulnaris. 
It supplies muscular branches to the flexor carpi ulnaris and 
the first or ulnar head of the flexor profundus digitorum. Near 
the middle of the forearm it divides into two branches, dorsal 
cutaneous (c) and palmar (2). 
The dorsal cutaneous branch (c) curves about the ulnar 
side of the wrist to the dorsum of the hand and divides into 
twigs which supply the dorsal part of the ulnar side of the fifth 
digit and of the contiguous sides of the fourth and fifth. The 
palmar branch (7) sends a twig to the integument on the flexor 
surface of the arm near the wrist, and then divides into deep 
palmar (¢) and superficial palmar (/) branches. 
' The superficial palmar branch (/) passes into the palm 
and supplies the ventral portion of the integument on the ulnar 
side of the fifth digit, and on the contiguous sides of the fifth 
and fourth. 
The deep palmar branch (ce) passes into the palm, beneath 
the ligament of the pisiform bone. Just distad of the pisiform 
bone it curves toward the radial side and breaks up into a 
number of small branches which are distributed to the short 
muscles in the palm. 
B. THoracic NERVES. 
Dorsal Rami.—-The dorsal rami of the thoracic nerves are 
