FRONT OF THE ARM 65 



to the subcutaneous surface on the back of the olecranon. 

 In cases of suspected fracture, therefore, this border affords 

 valuable information. The styloid process of the ulna 

 may be detected, immediately above the wrist, and it should 

 be observed that this does not extend so far distally as the 

 corresponding process of the radius. The rounded distal 

 end of the ulna makes a marked projection on the medial and 

 dorsal aspect of the limb immediately proximal to the wrist- 

 joint, and lying in the groove between it and the styloid 

 process the tendon of the extensor carpi ulnaris may be felt. 



Reflection of Skin. The skin should be removed from the limb as far 

 down as the radio-carpal joint. It is necessary to do this in order that a 

 connected view may be obtained of the cutaneous nerves and the superficial 

 veins. But at the same time the skin should not be cast aside, as it forms 

 a most efficient protective wrapping for the part even after it has been 

 detached. Make one long incision along the middle of the anterior aspect 

 of the arm and the volar surface of the forearm down to the radiocarpal 

 articulation. A second incision carried transversely round the distal end 

 of the forearm, immediately above the radio-carpal joint, will enable the 

 dissector to reflect the skin in two large flaps, medially and laterally. In 

 the fatty superficial fascia which is then exposed, the superficial structures 

 may be traced. It is well to begin with the nerves, as these are not so 

 apparent and, therefore, more liable to injury than the veins. But the 

 dissection of the veins should be carried on concurrently with that of the 

 nerves. 



Nervi Cutanei (Cutaneous Nerves). These are very 

 numerous, and are derived from several sources. In 

 addition to the two medial cutaneous nerves, which 

 spring from the brachial plexus, there are the terminal 

 cutaneous part of the musculo- cutaneous nerve, three 

 branches derived from the radial nerve and one the 

 intercostobrachial nerve form the second thoracic nerve. 

 These seven nerves may be classified into a medial and a 

 lateral group as follows : 



1 Distributed mainly 

 i. N. cutaneus antibrachu dorsahs upper branch, I the 



. . iu as upper ranc, the 



2. N. cutaneus antibrachu dorsahs lower branch, r *;_# nf f i 



AT ,., , .. , ,. part oi me arm 



3. N. cutaneus antibrachu laterahs, j J nd forearm< 



I. N. intercostobrachialis, "\ 



2. N. cutaneus brachii posterior, I Distributed mainly upon the medial 



3. N. cutaneus brachii medialis, j part of the arm and forearm. 



4. N. cutaneus antibrachii medialis, J 



The two dorsal cutaneous nerves of the forearm pierce the 



deep fascia about the middle of the lateral surface of the 



arm immediately distal to the insertion of the deltoid, and 



VOL. i 5 



