DISSECTION OF SUPERFICIAL STRUCTURES 69 



Dissection. Turn to the proximal end of the limb and com- 

 mence with the intercosto - brachial nerve, which was severed 

 when the superior extremity was removed from the trunk. It 

 lies in the posterior part of the medial side of the arm, and is at 

 first deep to the deep fascia. Note the point at which it pierces 

 the deep fascia (Figs. 31, 32) and trace it to its termination near 

 the elbow. By means of its various branches it supplies the skin 

 on the medial side of the posterior part of the arm (Figs. 31, 32). 



Find, next, the medial cutaneous nerve of the arm. It pierces 

 the deep of the fascia proximal third of the arm on the medial 

 side, and its branches supply the skin as far as the elbow in an 

 area anterior to that supplied by the intercosto-brachial nerve. 



After the medial cutaneous nerve of the arm has been cleaned, 

 look for the branches of the medial cutaneous nerve of the fore- 

 arm, which supply the medial part of the skin of the arm. They 

 vary in number and size, but they usually pierce the deep fascia 

 along the line of the medial border of the biceps brachii and they 

 communicate with one another (Fig. 31). 



The trunk of the medial cutaneous nerve of the forearm 

 either pierces the deep fascia close to the basilic vein, or it passes 

 through the same opening as the vein, and divides into its volar 

 and ulnar terminal branches. The volar branch passes either 

 deep or superficial to the median cubital vein and then descends 

 to the wrist. It supplies the skin of the ulnar half of the volar 

 aspect of the forearm. The ulnar branch passes either anterior 

 or posterior to the medial epicondyle and then along the ulnar 

 margin of the forearm. It supplies the skin of the ulnar margin 

 and of the ulnar part of the dorsum of the forearm as far as the 

 wrist. 



After the medial cutaneous nerve of the forearm has been 

 dissected, trace the remains of the posterior supraclavicular nerves 

 through the fat over the proximal part of the deltoid ; they supply 

 the skin over the proximal half of the deltoid muscle. When 

 they have been traced to their terminations make an incision 

 through the fat along the distal half of the posterior border of the 

 deltoid and secure the lateral cutaneous nerve of the arm. It is a 

 branch of the axillary nerve and will be found turning round the 

 posterior border of the deltoid at the junction of the proximal 

 two-thirds with the distal-third of the muscle (Figs. 31, 32, 33). 

 It runs forwards across the muscle and supplies the skin over its 

 distal half. 



To find the proximal and distal branches of the dorsal cutane- 

 ous nerve of the forearm dissect in the fat between the lateral 

 epicondyle of the humerus and the insertion of the deltoid. 

 They are branches of the radial nerve and both are occasionally 

 difficult to find. The proximal branch usually pierces the deep 

 fascia a little distal to the insertion of the deltoid (Figs. 31, 32). 

 It supplies the skin of the lateral part of the anterior aspect of 

 the arm as far as the elbow. The distal branch will be found 

 about one inch nearer the lateral epicondyle. It passes behind 

 the lateral epicondyle and then descends along the dorsal aspect 

 of the forearm to the wrist. 



After the distal branch of the dorsal cutaneous nerve of the 

 forearm has been traced to its termination, find the lateral 

 cutaneous nerve of the forearm. It is the continuation of the 

 musculo-cutaneous nerve. It appears at the lateral border of 

 i 5b 



