256 DISSECTION OF THE ARM. 



ends at the inner side of the hand. In the arm the nerve lies at first close 

 to the inner side of the axillary, and the brachial artery, as far as the 

 insertion of the coraco-brachialis ; then leaving the bloodvessel, it is di- 

 rected inwards through the inner intermuscular septum to the interval be- 

 tween the olecranon and the inner condyle, being surrounded by the mus- 

 cular fibres of the triceps. There is not any branch from the nerve till it 

 reaches the elbow-joint. 



The internal cutaneous ( 2 ) is a tegumentary nerve of the forearm, to 

 which it is prolonged like the others. Arising from the inner cord of the 

 plexus, it is at first superficial to the humeral artery as far as the middle 

 of the arm, where it divides into two branches that perforate the investing 

 fascia and reach the forearm (p. 250). Near the axilla it furnishes a 

 small cutaneous offset to the integuments of the arm. 



The small internal cutaneous nerve ( 3 ) (nerve of Wrisberg) arises with 

 the preceding. Concealed at first by the axillary vein, it is directed in- 

 wards beneath (but sometimes through) that vein, and joins with the inter- 

 costo-humeral nerve. Afterwards it lies along the inner part of the arm 

 as far as the middle, where it perforates the fascia to end in the integu- 

 ment (p. 251). 



The musculo-cvtaneous nerve (nerv. perforans, Casserii), named from 

 supplying muscles and integuments, ends on the surface of the forearm. 

 It leaves the outer cord of the brachial plexus opposite the lower border 

 of the pectoralis minor (fig. 70) and perforates directly the coraco-brach- 

 ialis : it is then directed obliquely to the outer side of the limb between 

 the biceps and brachialis anticus muscles. Near the elbow it becomes a 

 cutaneous nerve of the forearm. 



Branches. The nerve furnishes branches to the muscles in front of the 

 hurnerus, viz., to the coraco-brachialis as it passes through the fibres, and 

 to the biceps and brachialis anticus where it is placed between them. 



Dissection. The brachialis anticus muscle will be brought into view 

 by cutting through the tendon of the biceps near the elbow, and turning 

 upwards this muscle. The fascia and areolar tissue should be taken from 

 the fleshy fibres ; and the lateral extent of the muscle should be well de- 

 fined on each side, so as to show that it reaches the intermuscular septum 

 largely on the inner side, but only for a short distance above on the outer 

 side. 



Some care is required in detaching the brachialis externally from the 

 muscles of the forearm, to which it is closely applied. As the muscles are 

 separated the musculo-spiral nerve with a small artery comes into sight. 



The BRACHIALIS ANTICUS (fig. 78, H ) covers the elbow-joint, and the 

 lower half of the front of the humerus. It arises from the anterior sur- 

 face of the humerus below the insertion of the deltoid muscle ; and from 

 the intermuscular septa on the sides, viz., from all the inner, but from 

 only the upper part of the outer (about one inch and a half.) The fleshy 

 fibres converge to a tendon, which is inserted into the impression on the 

 front of the coronoid process of the ulna (p. 271). 



This muscle is concealed by the biceps. On it lies the brachial artery, 

 with the median, musculo-cutaneous, and musculo-spiral nerves. It covers 

 the humerus and the articulation of the elbow. Its origin embraces by 

 two parts the attachment of the deltoid ; and its insertion is placed between 

 two fleshy pieces of the flexor profundus digitorum. The inner border 

 reaches the intermuscular septum in all its length ; but the outer is sepa- 

 rated from the external intermuscular septum below by two muscles of 



