THE EADIAL NERVE. 



711 



RADIAL NERVE. 



In the axilla it lies behind the axillary artery, and in front of the subscapularis, 

 teres major, and latissimus dorsi muscles. 



In the arm, in the proximal third, it lies to the medial side of the humerus, behind 

 the brachial artery, and upon the long head of the triceps. In the middle third of 

 the arm it courses obliquely laterally and distally in the radial groove of the 

 humerus, along with the profunda brachii artery, separating the long, lateral, and 

 medial heads of the triceps muscle (Fig. 619, p. 708). In the distal third of the arm, 

 piercing the proximal part of the intermuscular septum at the lateral border of the 

 triceps muscle, it passes to the bend of the elbow in front of the lateral epicondyle 

 of the humerus, in the interval between the brachio-radialis and brachialis muscles. 

 Under cover of the former muscle, in the hollow of the elbow, it divides into its 

 two terminal branches, the superficial and deep rami. 



The collateral branches are in three sets, arising (a) on the medial side, (6) 

 on the back, and (c) on the lateral side of the humerus 

 (Fig. 620). 



1. Branches arising medial to the Humerus. 

 1. N. cutaneus brachii posterior (O.T. upper internal 

 cutaneous branch of musculo-spiral). The posterior 

 cutaneous nerve of the arm, arising in common with 

 one of the following, or independently, pierces the 

 fascia on the medial side of the arm near the axilla. 

 It supplies the skin of the posterior surface of the arm 

 in the proximal third, proximal and posterior to the 

 area supplied by the medial nerve of the arm (O.T. 

 lesser internal cutaneous) (Fig. 618, p. 707). This 

 nerve varies in size, according to the bulk of the last- 

 named and the intercosto-brachial nerves. 



2. Rami Musculares. The muscular branches are 

 in two sets. One series supplies the long head 

 of the triceps muscle near its origin ; the other series 

 enters the medial head of the muscle. One of the 

 latter, separating itself from the rest, accompanies the 

 ulnar nerve in the middle third of the arm, and sup- 

 plies the distal part of the muscle. This is sometimes 

 called the collateral ulnar nerve. 



II. Branches arising on the Posterior Surface 

 of the Humerus. Muscular branches arise from the 

 nerve in the radial groove for the supply of all 

 three heads of the triceps muscle. The branch 

 which enters the medial head of the muscle, besides 

 supplying it, passes through the muscle and behind 

 the lateral epicondyle of the humerus, to terminate in 

 the anconseus. 



III. Branches arising at the Lateral Side of the 

 Humerus. 1. The dorsal cutaneous nerve of the forearm 

 consists of two branches, proximal and distal. Arising 



from the radial nerve before it pierces the lateral intermuscular septum, these 

 branches pierce the deep fascia close together on the lateral side of the arm in 

 its distal half. Passing distally over the back of the lateral epicondyle, the 

 proximal branch supplies the skin of the lateral side and posterior surface of the 

 arm in its distal third, and the dorsal surface of the forearm in its proximal half. 

 The distal branch supplies an area of skin on the dorsal surface of the forearm 

 in the proximal two-thirds, medial to the area innervated by the inusculo-cutaneous 

 nerve (Fig. 618, p. 707). 



'. Muscular Branches. The radial nerve, as it lies in the interval between 

 the brachialis and brachio-radialis muscles, supplies a small branch to the brachialis 

 (which in some cases is not present) and nerves to the brachio - radialis and 

 extensor carpi radialis longus. It may also provide the nerve to the extensor 

 carpi radialis brevis. 



46 & 



DORSAL 



CUTANEOUS N. 

 OF FOREARM 



JOINT 



TO ANCONAEUS 



THE RADIAL NERVE. 



