364 ABRAM T. KERR 



from the subscapular nerve and gives off a small branch to the 

 latissimus dorsi muscle. In 5, it is formed from a common trunk 

 with the thoracodorsal nerve. In 68 other cases it arises from 

 the axillary nerve which takes origin from the posterior fascic- 

 ulus (fig. 1), and in one from the radial nerve that arises from 

 the posterior fasciculus. Its origin is directly or indirectly from 

 the posterior fasciculus in 117 cases, or in 74.52 per cent of the 

 cases. 



It arises directly from the cord formed by the union of the 

 dorsal divisions of the cephalic and intermediate trunks in 12 

 cases (fig. 13), and from the axillary nerve that takes origin from 

 this cord in 9 others (fig. 6), making a total of 21 or in 13.37 per 

 cent of the 157 cases. 



It comes from the dorsal division of the cephalic trunk in 3 

 cases directly (fig. 10), and in 7 others from the axillary nerve 

 that takes origin from the dorsal division of the cephalic trunk 

 (fig. 23), making 10 in all. 



In one other case it arises from the axillary nerve and this 

 nerve arises by two roots, one from the dorsal division of the 

 cephalic trunk and one from the dorsal division of the intermedi- 

 ate trunk. 



In one plexus it arises from the dorsal division of the inter- 

 mediate trunk and in 2 from the cord formed by the union of the 

 dorsal divisions of the caudal and intermediate trunks. 



In 5 instances it arises by two heads. In 4 of these one comes 

 from the dorsal division of the cephalic, and one from the dorsal 

 division of the intermediate trunk (fig. 7). In one of these 

 the thoracodorsal nerve arises in common with the axillary sub- 

 scapular nerve. In the fifth case, one root comes from the cord 

 formed by the union of the dorsal branches of the cephalic and 

 intermediate trunks and the other from the dorsal division of 

 the caudal trunk. Immediately after its origin, the nerve re- 

 ceives a branch from the thoracodorsal nerve. 



It will be noted then that the axillary subscapular nerve arises 

 directly from one of the dorsal divisions of the brachial plexus 

 in 71 instances or 45.22 per cent, and from the axillary nerve 

 in 85 instances or 54.14 per c^nt. 



