INTERNAL CUTANEOUS NERVE. 



641 



Fig. 351. Cutaneous Nerves of 

 Rijrht Upper Extremity. Poste- 

 rior View. 



fascia, accompanies that vessel to the back of the wrist. It communicates with 

 a branch from the radial nerve, and distributes filaments to the integument of 

 the ball of the thumb. 



The posterior branch is given off about the middle of the forearm, and passes 

 downwards, along the back part of its radial side to the wrist. It supplies the 

 integument of the lower third of the forearm, 

 communicating with the radial nerve, and the 

 external cutaneous branch of the musculo-spiral. 



The Internal Cutaneous Nerve (Fig. 352) is one 

 of the smallest branches of the brachial plexus. 

 It arises from the inner cord, in common with 

 the ulnar and internal head of the median, and, 

 at its commencement, is placed on the inner side 

 of the brachial artery. It passes down the inner 

 side of the arm, pierces the deep fascia with the 

 basilic vein, about the middle of the limb, and, 

 becoming cutaneous, divides into two branches. 



This nerve gives off, near the axilla, a cuta- 

 neous filament, which pierces the fascia, and sup- 

 plies the integument covering the Biceps muscle, 

 nearly as far as the elbow. This filament lies a 

 little external to the common trunk from which 

 it arises. 



The anterior branch, the larger of the two, 

 passes usually in front of, but occasionally be- 

 hind, 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. 



The posterior branch passes obliquely down- 

 wards on the inner side of the basilic vein, winds 

 over the internal condyle of the humerus to the 

 back of the forearm, and descends, on the poste- 

 rior surface of its ulnar side, to a little below the 

 middle, distributing filaments to the integument. 

 It anastomoses above the elbow, with the lesser 

 internal cutaneous, and above the wrist, with the 

 dorsal branch of the ulnar nerve (Swan). 



The Lesser Internal Cutaneous Nerve (nerve of 

 Wrisberg) (Fig. 352), is distributed to the in- 

 tegument on the inner side of the arm. It is the 

 smallest of the branches of the brachial plexus, 

 and usually arises from the inner cord, with the 

 internal cutaneous and ulnar nerves. It passes 

 through the axillary space, at first lying behind, 

 and then on the inner side of the axillary vein, 

 and communicates with the intercosto-humeral 

 nerve. It then descends along the inner side of 

 the brachial artery, to the middle of the arm, 

 where it pierces the deep fascia, and is distri- 

 buted to the integument of the back part of the 

 lower third of the arm, extending as far as the 



elbow, where some filaments are lost in the integument in front of the inner 

 condyle, and others over the olecranon. It communicates with the inner 

 branch of the internal cutaneous nerve. 



In some cases the nerve of Wrisberg and intercosto-humeral are connected 

 41 



