BRACHIAL PLEXUS OF NERVES IN MAN 313 



intermediate trunk receives an additional branch from the ventral 

 branch of the cephalic trunk. 



In 4 instances the cephalic and intermediate trunks join and 

 the cord thus formed divides into dorsal and ventral branches. 

 The dorsal branch joins with the dorsal division of the caudal 

 trunk to form the posterior fasciculus (fig. 21). 



In one case the fifth and sixth cervical nerves divide into dorsal 

 and ventral branches. The dorsal branches unite to form a 

 dorsocephalic cord that joins another cord formed by the union 

 of the dorsal branches of the intermediate and caudal trunks to 

 form the posterior fasciculus. Slightly more distal the posterior 

 fasciculus receives an extra branch from the lateral fasciculus. 

 It will be seen then that the posterior fasciculus is formed by the 

 union of dorsal branches of the plexus in 139 records. 



In 36 plexuses or 20.57 per cent of the 175 studied, there is no 

 real posterior fasciculus unless we consider a single nerve, the 

 radial, as representing the dorsal fasciculus. 



The arrangement of the dorsal branches in these cases will be 

 described in connection with the discussion of the radial and 

 axillary nerves. 



If the epineurium could have been completely removed from 

 all the plexuses, I have no doubt that more of them would have 

 corresponded to this last group in which no real dorsal fasciculus 

 was formed. It will be noted that in all but 6 of the plexuses of 

 this series the caudal branch to the dorsal fasciculus was from the 

 caudal trunk formed by the eighth cervical and the first thoracic 

 nerves. Herringham ('87) found the branch from the first 

 thoracic to the dorsal fasciculus absent in 39 out of 45 cases or 

 in 86.66 per cent. W. Harris ('04) however, found the branch 

 from the first thoracic nerve to the dorsal fasciculus 7 times out 

 of 9. In the specimens studied by maceration in nitric acid, I 

 found that the first thoracic sends branches to the dorsal fascicu- 

 lus in the majority of instances. As already explained, because 

 of the danger of breaking the minute connections by gross dis- 

 section I have attempted to determine in only a few instances 

 whether or not the branch to the dorsal fasciculus from the caudal 

 trunk contained fibers from both the eighth cervical and first 



