THE PERIPHERAL NERVOUS SYSTEM. 393 



radialis longus. It supplies the supinator and extensor 

 muscles of the forearm (brachioradialis, suphiator, 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). 



II. N. ulnaris (Fig. i6o, n). — 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, a) 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 {d). 



The dorsal cutaneous branch (r) 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 (<■/) sends a twig to the integument on the flexor 

 surface of the arm near the wrist, and then divides into deep 

 palmar [c) 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. 



Tiic deep palmar branch {e) 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 



