342 ABRAM T. KERR 



the fourth cervical nerve. He does not, however, give the num- 

 ber of cases of each that he found. 



THE SUBCLAVIUS NERVE 



The nerve to the subclavius muscle is usually described as 

 arising from the cephalic trunk of the brachial plexus, occasion- 

 ally from the fifth cervical nerve. 



The nerve is a slender twig and is often broken in the dis- 

 section so that among the 175 plexuses of my series, it was satis- 

 factorily dissected and recorded in only 83 cases. 



In 18 or 21.68 per cent of these it arises from the fifth cervical 

 nerve after the fourth has joined it so that the fibers of the fourth 

 cannot be excluded. In 13 instances it is found as a single 

 separate branch (fig. 11) ; in 3 it arises from a common stem with 

 a branch to the phrenic nerve; and in 2 from a common stem with 

 the dorsal scapular nerve to the rhomboid muscle. 



In 22 plexuses or 26.50 per cent it arises from the fifth cervical 

 nerve only; in 10 as a separate branch (fig. 16), and in 10 from 

 a common stem with a branch to the phrenic nerve (fig. 25) ; 

 and in 1 from a branch common to it and the dorsal scapular 

 nerve. There is also one of the above instances in which it 

 arises from a stem common to it and a branch to the phrenic 

 nerve that arises from the fifth cervical nerve but receives a 

 branch from the sixth before dividing (fig. 7). 



In 41 or 49.39 per cent of the 83 cases it arises from the cephalic 

 trunk or its ventral branch. In 27 of these this trunk is formed 

 by the fourth, fifth and sixth cervical nerves. In 20 of these 

 instances it comes from the main branch of the cephalic trunk; 

 14 times as a single branch (fig. 6), and 6 times in combination 

 with a branch to the phrenic nerve. In 7 of the above 27 cases 

 the subclavian nerve arises from the ventral branch of the cephalic 

 trunk, in 5 as a single branch, in 1 in combination with a branch 

 to the phrenic nerve and in 1 with the lateral anterior thoracic 

 nerve. 



Id 14 of the 41 instances, in which the nerve arises from the 

 cephalic trunk, this trunk is formed by the fifth and sixth cervical 

 nerves only. In 9 of these the nerve arises from the undivided 



