138 THE SUPERIOR EXTREMITY 



Dissection. The superficial muscles which arise from the 

 medial epicondyle of the humerus must now be cleaned. 

 Commence with the most lateral of the group, thepronator teres, 

 and follow it from its origin to its insertion into the middle of 

 the lateral surface of the radius. To expose the insertion the 

 brachio-radialis and the long and short radial extensors of the 

 carpus which cover it must be pulled aside. As the distal part of 

 the pronator teres is being cleaned be careful not to injure the thin 

 radial origin of the flexor digitorum sublimis which lies behind 

 it. Separate the proximal part of the pronator teres from the 

 flexor carpi radialis by dividing the intermuscular septum 

 between them. Divide the superficial head of the pronator teres, 

 turn the proximal part towards the medial epicondyle and the 

 distal part towards the radius and follow the deep head between 

 the median nerve and the ulnar artery to its origin from the 

 coronoid process of the ulna. After the pronator teres has been 

 examined clean the flexor carpi radialis, but do not follow its 

 tendon of insertion beyond the proximal edge of the transverse 

 carpal ligament, where it enters a special osteo-fibrous canal 

 through which it will be traced in a later dissection. Now clean 

 the palmaris longus ; trace its tendon to the intermediate part 

 of the palmar aponeurosis, and note that as it crosses the 

 transverse carpal ligament its deep surface is attached to the 

 ligament. 1 



The most medial muscle of the group, the flexor carpi ulnaris, 

 must now be cleaned. Note that its tendon of insertion lies 

 along the volar border of the distal part of the muscle. This is 

 a point of practical importance, for the tendon is used as a guide 

 during operations upon the ulnar nerve and artery in the distal 

 part of the forearm. Clean both heads of origin of the flexor 

 carpi ulnaris, one from the medial epicondyle and one from the 

 medial border of the olecranon of the ulna, and note that the 

 ulnar nerve, accompanied by the superior ulnar collateral artery, 

 disappears between them. Separate the proximal part of the 

 flexor carpi ulnaris from the adjacent parts of the palmaris longus 

 and the flexor digitorum sublimis by splitting the septa between 

 them; secure the ulnar nerve and its branches to the flexor 

 carpi ulnaris and the flexor digitorum profundus on the deep 

 surface of the flexor carpi ulnaris. Follow the ulnar nerve 

 distally. At the junction of the proximal and middle thirds 

 of the forearm it is joined by the ulnar artery, which appears 

 from under cover of the medial border of the flexor digitorum 

 sublimis. Clean the artery and nerve, as far as the lateral 

 side of the pisiform bone, and find the origins of the dorsal 

 and palmar branches of the nerve, which were seen when the 

 superficial structures of the palm and on the dorsum of the 

 hand were dissected (p. 70). Secure also the volar carpal 

 branch of the artery which arises near the proximal border of 

 the transverse carpal ligament. 



To get a good view of the flexor digitorum sublimis divide 

 the palmaris longus and the flexor carpi radialis at the middle 

 of the forearm. Turn the proximal parts of both the muscles 

 upwards and separate them from the pronator teres and the 

 flexor sublimis by splitting the intervening intermuscular septa. 



1 The palmaris longus is not uncommonly absent. 



