

NERVES OF THE ARM. 



fascia, to be distributed to the integuments about the 

 elbow. It communicates with filaments of the internal 

 cutaneous and musculo-spiral nerves, and in the axilla 

 with the first intercosto-humeral nerve^ 



The external cutaneous, (Fig. 239,) called also musculo- 

 cutaneous, or perforans Casserii, comes from either the 

 upper or middle division of the plexus, is larger than the 

 last, and descends by perforating the coraco-brachialis 

 muscle. It then passes outward between the biceps and 

 brachialis anticus, distributing filaments to these muscles, 

 and at the bend of the elbow it becomes superficial, joins 

 the cephalic vein, and descends to the wrist, where it 

 divides into branches, some of which are anterior, supply- 

 ing the ball of the thumb, others posterior, distributed to 

 the back of the hand. 



The circumflex or articular nerve arises from the lower 

 part of the plexus, and passes along with the posterior 

 circumflex artery, around the neck of the humerus, between 

 the teres minor and major muscles, to be distributed on 

 the inner surface of the deltoid. This nerve encircles the 

 neck of the humerus by a superior and inferior branch. 



The median or brachial nerve, (Fig. 235;) so called from 

 being between the ulnar and radial nerves, arises by two 

 roots and descends the arm in front of the brachial artery, 

 inclining however above rather to the outer side of the 

 artery, and below to its inner or ulnar side. It goes along 

 the inner edge of the biceps muscle, and at the bend of the 

 elbow is seen on the ulnar side of the supinator longus 

 beneath the bicipital aponeurosis. Here it perforates the 

 pronator teres, and descends the middle of the forearm, 

 between the superficial and deep flexors, to the anterior 

 annular ligament of the wrist, beneath which it passes to 

 the palm of the hand, there to terminate in digital branches. 



The median nerve gives off at the bend of the elbow 

 muscular branches, supplying most of the flexors and pro- 

 nators; next, the interosseous nerve, a considerable branch 

 which accompanies the anterior interosseal artery, sup- 

 plying the deep flexors in its course. At the pronator 



