356 ABRAM T. KERR 



THE RADIAL NERVE 



The radial nerve (musculo-spiral) is usually described as one 

 of the two terminal branches of the posterior fasciculus of the 

 brachial plexus produced by the division of the fasciculus into 

 radial and axillary. 



In my series the radial nerve is formed by the division of the 

 posterior fasciculus of the plexus in 138 plexuses, or 79.76 per 

 cent of the 173 satisfactory records for this nerve (figs. 1 to 5). 



There are, as already noted in connection with the dorsal 

 fasciculus, 36 plexuses in which there is no true dorsal trunk 

 but the radial and axillary nerves are formed by the union of 

 dorsal branches of the plexus. There are 35 of these cases where 

 the record for the radial nerve is satisfactory and in these cases 

 the radial nerve is formed by the union of two heads. 



In 19 of these a cord formed by the union of the dorsal divisions 

 of the cephalic and intermediate trunks, after giving off the 

 axillary nerve forms the cephalic head of the radial nerve. This 

 joins the caudal head of the radial which is the whole of the dorsal 

 division of the caudal trunk (fig. 6). The dorsal division of 

 the intermediate trunk in two of these and the caudal head of the 

 radial nerve in another sends a branch to the axillary nerve. 

 In one of these the dorsal division of the caudal trunk is repre- 

 sented by two branches, one from the eighth cervical and one 

 from the first thoracic i^erve. In another the dorsal division 

 of the caudal trunk comes from the eighth cervical only. More 

 than the usual amount of connective tissue had been removed 

 in this case so that three of the branches for the muscles of the 

 arm that ordinarily arise from the radial came from its heads, 

 two from the caudal head and one from the cephalic head. In 

 two of the above 19 cases the radial nerve receives a branch from 

 the medial fasciculus of the plexus, in one as a separate branch 

 and in the other as a branch of the medial brachial cutaneous 

 nerve that comes from the medial fasciculus. In 4 of the above 

 instances, the radial gives off the thoracodorsal nerve. 



In 10 cases the dorsal division of the cephalic trunk, after 

 giving off the axillary nerve forms the cephalic head of the radial 

 nerve. In two of these the dorsal division of the cephalic trunk 



