1037 



pierces the deep fascia with the basilic vein, about the middle of the limb, and, 

 becoming- cutaneous, divides into two branches, anterior and posterior. 



The anterior branch, the larger of the two, passes usually in front of, but occa- 

 sionally behind, the median basilic vein. It then descends on the, anterior surface 

 of the ulnar side of the forearm, distributing filaments to the integument as far 

 as the wrist, and communicating with a cutaneous branch of the ulnar nerve 

 (Fig. 760). 



The posterior branch passes obliquely downward on the inner side of the basilic 

 jrein. passes in front of, or over, the internal condyle of the humerus to the back 

 of the forearm, and descends on the posterior surface of its ulnar side as far as 

 the wrist, distributing filaments to the integument (Fig. 761). It communicates, 

 above the elbow, with the lesser internal cutaneous nerve, the lower external 

 cutaneous branch of the musculospiral, and above the wrist with the posterior 

 cutaneous branch of the ulnar nerve. The cutaneous areas supplied by the 

 internal cutaneous nerve are indicated in Figs. 762 and 763. 



The Lesser Internal Cutaneous Nerve, or the Nerve of Wrisberg (n. cutaneusbrachii 

 medialis} (Figs. 759 and 764), is distributed to the integument on the inner side 

 of the arm. It is the smallest of the branches of the brachial plexus, and, arising 

 from the inner cord, receives its fibres from the first thoracic nerve. It passes 

 through the axillar^ space, at first lying behind, and then on the inner side of, the 

 axillary vein, and communicates with the intercostohumeral nerve. Tt descends 

 jilong the inner side of the bfachial artery to the middle of the arm, where it 

 "pierces the deep fascia, and \l distributed to the integument of the back of the 

 lower third of the arm, extending as far as the elbow (Figs. 761 and 762), where 

 some filaments are lost in -the integument in front of the inner condyle, and 

 others over the olecranon. It communicates with the posterior branch of the 

 internal cutaneous nerve. 



In some cases the nerve of Wrisberg and the intercostohumeral nerve are con- 

 nected by two or three filaments which form a plexus at the back part of the 

 axilla. In other cases the intercostohumeral is of large size, and takes the place 

 of the nerve of Wrisberg, receiving merely a filament of communication from the 

 brachial plexus, which filament represents the latter nerve. In other cases this 

 filament is wanting, the place of the nerve of Wrisberg being supplied entirely by 

 the intercostohumeral. 



The Median Nerve (/?,. medianus) (Figs. 758 and 764 s ) extends along the middle 

 of the arm and forearm to the hand, lying between the ulnar and musculospiral 

 nerves, and the ulnar and the radial nerves. It arises by two roots, one from tlie" 

 ^uter and one from the inner cord of the brachial plexus; these embrace the lower 

 part of the axillary artery, uniting either in front or on the outer side of that vessel. 

 The median nerve receives filaments from the sixth, seventh, and eighth cervical 

 and the first thoracic nerves, and sometimes from the fifth cervical as well. As it 

 descends through the arm, it lies at first on the outer side of the brachial artery, 

 crosses that vessel in the middle of its course, usually in front, but occasionally 

 behind it, and lies on its inner side to the bend of the elbow, where it is situated 

 beneath the hicipital fascia, and is separated from the elbow-joint by the Brachialis 

 anticus muscle. In the forearm it passes between the two heads of the Pronator 

 teres muscle and crosses the ulnar artery, but is separated from that vessel by the 

 deep head of the Pronator teres. It descends beneath the Flexor sublimis muscle, 

 lying on the Flexor profundus muscle, to within two inches (5 cm.) above the 

 annular ligament, where it becomes more superficial, lying between the tendons 

 of the Flexor sublimis and Flexor carpi radial is muscles, beneath, and rather to 

 the radial side or under the tendon of the Palmaris longus, covered by the integu- 

 ment and fascia. It then passes through the carpal canal (canalis carpi] beneath 

 the annular ligament into the palm of the hand. In its course through the fore- 



