NERVES OF THE ARM. 255 



an arch across the back of the humerus with a branch of the superior pro- 

 fun da. 



In front of the elbow joint the anastomotic branch sends an offset to 

 the pronator teres muscle: this joins the anterior ulnar recurrent branch. 



Vasa aberrantia. Occasionally long slender vessels connect the bra- 

 chial or the axillary trunk with the radial artery; the accessory vessel 

 very rarely ends in the ulnar artery. 



The BRACHIAL VEINS (tig. 78, d) accompany the artery, one on each 

 side, and have branches of communication across that vessel; they receive 

 contributing veins corresponding with the branches of the arteries. Su- 

 periorly they unite into one, which joins the axillary vein near the sub- 

 scapular muscle. 



NERVES OF THE ARM (fig. 78). The nerves on the front of the arm 

 are derived from the terminal cords of the brachial plexus. Few of them 

 furnish offsets above the elbow, but they are continued, for the most part 

 without branching, to the forearm and the hand. The cutaneous brandies 

 of some of them have been referred to (p. 250). 



Fig. 78. 



MUSCLES AND DEEP VESSELS AXD NERVI s OF THE ARM. (Illustrations of Dissections.) 



Muscles : Nemes : 



A. Pectoralis major. 1. Median. 



B. Biceps. 2. Internal cutaneous, 

 c. Coraco-brachialis. 3. Nerve of Wrisbei'K. 

 D and E. Latissimus and teres. 4. Ulnar. 



F. Long head of the triceps. 5. Muscular to the triceps. 



. Inner head of triceps. 6. Internal cutaneous from the 



H. Brachialis anticus. niusculo-spiral. 



The median nerve (' ) arises from the brachial plexus by two roots, one 

 from the outer, and the other from the inner cord (p. 236). Its destina- 

 tion is to the palm of the hand; and it accompanies the brachial artery 

 to the forearm. Beginning on the outer side of the artery, the nerve 

 crosses over or under it about the middle of the arm, and is placed on the 

 inner side a little above the elbow. It does not give any branch in the 

 arm; but there may be a fasciculus connecting it with the musculo-cuta- 

 neous nerve. Its connections with muscles are the same as those of the 

 artery. 



The ulnar nerve ( 4 ), derived from the inner cord of the brachial plexus, 



