BRACHIAL PLEXUS OF NERVES IN MAN 357 



is formed by the union of the dorsal divisions of the fifth and 

 sixth cervical nerves (fig. 15). In the above 10 instances the 

 caudal head of the radial nerve is formed by the union of the 

 dorsal divisions of the intermediate and caudal trunks (fig. 7). 

 In one of these the dorsal division of the caudal trunk is from the 

 eighth cervical nerve only, but in this case the radial nerve 

 receives a branch from the medial fasciculus and it also gives 

 off the thoracodorsal nerve. 



In another case the cephaHc head of the radial nerve is formed 

 as above but the caudal head is formed by the dorsal division of 

 the intermediate trunk being joined by the dorsal division of 

 the eighth cervical nerve and more distad by the dorsal division 

 of the first thoracic nerve. 



In 4 cases the cephalic head of the radial nerve is formed by 

 the dorsal division of the cephalic trunk after giving off the axil- 

 lary nerve joining the dorsal division of the intermediate trunk. 

 The caudal head of the radial nerve in these cases is formed by 

 the dorsal division of the caudal trunk. 



In one instance the cephalic head of the radial nerve is formed 

 by the dorsal division of the cephalic trunk joining the dorsal 

 division of the intermediate trunk after this has given off the 

 axillary nerve. The caudal head of the radial is the dorsal 

 division of the caudal trunk. 



In 169, or 97.68 per cent of the cases, none of the nerves of the 

 plexus can be excluded from sending fibers to the radial. In 

 109, the fourth, fifth, sixth, seventh and eighth cervical and 

 first thoracic might contribute and in 60 the fourth cervical did 

 not enter the plexus. In 4 instances, there was no dorsal branch 

 from the first thoracic nerve so that in these this could be posi- 

 tively excluded. 



Wichmann reports from the literature that fibers from the 

 fifth, sixth, seventh and eighth unite to form the radial nerve in 

 98 cases; from the sixth, seventh and eighth in 27 cases; from the 

 fifth, sixth, seventh and eighth cervical and first thoracic in 25 

 cases; the sixth, seventh and eighth cervical and first thoracic 

 in 3; and the fifth, sixth and seventh; the sixth and seventh; 

 and the seventh and eighth in one case each. 



