DORSUM OF THE ARM 87 



the humerus by dividing into two terminal branches, viz. the 

 ramus superficialis (O.T. radial) and the ramus profundus 

 (O.T. posterior interosseous). The radial nerve presents, 

 therefore, very different relations as it is traced from its origin 

 to its termination: (i) between the subscapularis, latissimus 

 dorsi, teres major, and long head of the triceps which support 

 it behind, and the axillary and brachial arteries which are 

 placed in front of it ; (2) between the long and the medial heads 

 of the triceps ; (3) in the sulcus for the radial nerve between 

 the bone and the lateral head of the triceps ; (4) in the interval 

 between the brachialis on the medial, and the brachioradialis 

 and extensor carpi radialis longus on the lateral side. 



The branches which proceed from the radial nerve 

 are muscular, cutaneous, and terminal. 



The cutaneous branches are two in number, and have already 

 been traced. They are (i) the n. cutaneus brachii posterior, 

 and (2) and (3) the nervi cutanei antibrachii dorsales. 



The muscular branches are distributed to the three heads 

 of the triceps, to the anconaeus, to the lateral fibres of the 

 brachialis, to the brachic-radialis, and to the extensor carpi 

 radialis longus. The branches to the three last-named 

 muscles spring from the trunk of the nerve after it has 

 pierced the lateral intermuscular septum. The branch to 

 the medial head of the triceps is a long slender nerve, 

 termed the ulnar collateral nerve, on account of its association 

 with the ulnar nerve in the arm. The branch to the 

 anconaeus is a long slender twig which passes through the 

 substance of the medial head of the triceps on its way to 

 the anconaeus (Fig. 37). 



The terminal branches are the ramus superficialis (O.T. 

 radial), which is a purely cutaneous nerve, and the ramus 

 profundus (O.T. posterior interosseous), which is continued 

 into the dorsal part of the forearm as the dorsal interosseous 

 nerve, and is distributed to the muscles on the dorsal aspect 

 of the forearm, and to the radiocarpal joint. These nerves 

 will be followed later. 



Arteria Profunda Brachii (O.T. Superior Profunda Artery). 



This artery has been already observed to take origin from 



the brachial trunk, immediately below the lower margin of 



the teres major muscle. It accompanies the radial nerve and 



its relations to the three heads of the triceps and the sulcus 



for the radial nerve of the humerus are exactly the same as 



i 6& 



