ii2 THE SUPERIOR EXTREMITY 



the medial epicondyle where they anastomose with the superior 

 and inferior ulnar collateral branches of the brachial artery. 



After the relative positions of the contents of the cubital 

 fossa have been studied turn to the dissection of the back of 

 the arm. 



DORSUM OF THE ARM. 



In this region in addition to the cutaneous nerves the 

 following are the structures which must be studied : 



1. The triceps muscle. 



2. The profunda brachii artery, and the radial nerve. 



3. The superior ulnar collateral artery, and the ulnar nerve. 



4. The posterior branch of the inferior ulnar collateral artery. 



5. The subanconaeus muscle. 



The skin and the superficial fascia have already been 

 removed but the cutaneous nerves are still present, and 

 the dissector should revise them before proceeding with the 

 dissection. 



On the medial side are branches of the intercosto-brachial 

 nerve ; lateral to them lies the posterior brachial cutaneous 

 branch of the radial nerve, and, along the lateral margin of 

 the arm, is the dorsal cutaneous nerve of the forearm, also 

 a branch of the radial nerve. 



Dissection. Make a vertical incision through the deep fascia 

 as far as the olecranon of the ulna, and a transverse incision 

 across the olecranon from one epicondyle to the other, taking 

 care not to injure the dorsal cutaneous nerve of the forearm. 

 Reflect the flaps of deep fascia to their respective sides until 

 their continuity with the medial and lateral intermuscular septa 

 respectively is demonstrated. As the medial flap is reflected, 

 avoid injury to the ulnar nerve which descends towards the 

 medial epicondyle on the medial head of the triceps. It is 

 accompanied by the superior ulnar collateral artery. When 

 the reflection of the flaps is completed clean the triceps muscle 

 and define carefully its attachments to the scapula, to the humerus, 

 and to the ulna. 



M. Triceps Brachii. The triceps muscle occupies the 

 entire posterior osteo-fascial compartment of the arm. It 

 arises by a long head from the scapula, and by two shorter 

 heads, lateral and medial, from the humerus. The fleshy 

 fibres of the three heads join a common tendon, which is 

 inserted into the proximal surface of the olecranon of the 



