THE CERVICAL NERVES 943 



digital branch for the ulnar side of the little finger, and a common volar digital 

 branch which gives a communicating twig to the median nerve and divides into 

 two proper digital nerves for the adjoining sides of the little and ring fingers (Fig. 

 811). The proper digital branches are distributed to the fingers in the same 

 manner as those of the median. 



The deep branch (minus profundus) accompanied by the deep branch of the ulnar 

 artery, passes between the Abductor digiti quinti and Flexor digiti quinti brevis; 

 it then perforates the Opponens digiti quinti and follows the course of the deep 

 volar arch beneath the Flexor tendons. At its origin it supplies the three short 

 muscles of the little finger. As it crosses the deep part of the hand, it supplies all 

 the Interossei and the third and fourth Lumbricales; it ends by supplying the Ad- 

 duct ores pollicis and the medial head of the Flexor pollicis brevis. It also sends 

 articular filaments to the wrist-joint. 



It has been pointed out that the ulnar part of the Flexor digitorum profundus 

 is supplied by the ulnar nerve; the third and fourth Lumbricales, which are con- 

 nected with the tendons of this part of the muscle, are supplied by the same 

 nerve. In like manner the lateral part of the Flexor digitorum profundus and 

 the first and second Lumbricales are supplied by the median nerve; the third 

 Lumbricalis frequently receives an additional twig from the median nerve. 



The Radial Nerve (n. radialis; musculospiral nerve) (Fig. 818), the largest branch 

 of the brachial plexus, is the continuation of the posterior cord of the plexus. Its 

 fibres are derived from the fifth, sixth, seventh, and eighth cervical and first thoracic 

 nerves. It descends behind the first part of the axillary artery and the upper part 

 of the brachial artery, and in front of the tendons of the Latissimus dorsi and Teres 

 major. It then winds around from the medial to the lateral side of the humerus in 

 a groove with the a. profunda brachii, between the medial and lateral heads of the 

 Triceps brachii. It pierces the lateral intermuscular septum, and passes between 

 the Brachialis and Brachioradialis to the front of the lateral epicondyle, where 

 it divides into a superficial and a deep branch. 



tThe branches of the musculospiral nerve are: 

 Muscular. Superficial. 



Cutaneous. Deep. 



The muscular branches (rami musculares) supply the Triceps brachii, Anconseus, 

 Brachioradialis, Extensor carpi radialis longus, and Brachialis, and are grouped as 

 medial, posterior, and lateral. 



The medial muscular branches supply the medial and long heads of the Triceps 

 brachii. That to the medial head is a long, slender filament, which lies close to the 

 , ulnar nerve as far as the lower third of the arm, and is therefore frequently spoken 

 of as the ulnar collateral nerve. 



The posterior muscular branch, of large size, arises from the nerve in the groove 

 between the Triceps brachii and the humerus. It divides into filaments, which 

 supply the medial and lateral heads of the Triceps brachii and the Anconaeus 

 muscles. The branch for the latter muscle is a long, slender filament, which descends 

 in the substance of the medial head of the Triceps brachii. 



The lateral muscular branches supply the Brachioradialis, Extensor carpi radialis 

 longus, and the lateral part of the Brachialis. 



The cutaneous branches are two in number, the posterior brachial cutaneous 

 and the dorsal antibrachial cutaneous. 



The posterior brachial cutaneous nerve (n. cutaneu-s brachii posterior; internal 

 cutaneous branch of musculospiral) arises in the axilla, with the medial muscular 

 branch. It is of small size, and passes through the axilla to the medial side of 

 the area supplying the skin on its dorsal surface nearly as far as the olecranon. 

 In its course it crosses behind, and communicates with, the intercostobrachial. 





