BRACHIAL PLEXUS OF NERVES IN MAN 371 



32. In over 54 per cent of the cases the cephaHc group, type 

 B on one side is associated with an intermediate group, type E 

 on the other. 



33. In 12.50 per cent the cephaHc group B is on one side and 

 the caudal group F on the other. 



34. The ulnar nerve is formed by the division of the medial 

 fasciculus of the plexus into medial head of the median nerve 

 and the ulnar nerve in over 97 per cent of the cases. 



35. There is a lateral head to the ulnar nerve arising from the 

 lateral fasciculus of the plexus, from the lateral head of the 

 median nerve or from the seventh cervical nerve in about 60 

 per cent of the cases. 



36. The ulnar nerve receives its fibers from the eighth cervical 

 and first thoracic nerves probably in all cases, and in those with 

 a lateral head, some fibers from the seventh cervical and possibly 

 some other nerves of the plexus send fibers to it. 



37. In the cephalic group of plexuses the ulnar nerve appears 

 to receive fibers from spinal nerves cephalic to the eighth cervical 

 nerve more frequently than in the caudal group. 



38. In over 86 per cent of the cases the median nerve is formed 

 by the union of two heads, a lateral head from the lateral fascicu- 

 lus of the plexus, a medial head from the medial fasciculus. 



39. In only one of my cases can I be sure that any nerve that 

 contributes to the brachial plexus did not also send fibers to the 

 median nerve. 



40. The musculocutaneous nerve arises from the division of the 

 lateral fasciculus of the plexus into medial head of the median 

 and musculocutaneous nerve in over 88 per cent of the plexuses. 



41. In the arm the musculocutaneous gives off a branch that 

 joins the median nerve in 24 per cent of the cases. This is probably 

 a greater percentage than would be found if complete records 

 through the arm had been available for all the cases. 



42. The musculocutaneous nerve may receive its fibers from 

 the fourth, fifth, sixth and seventh cervical nerves in 56 per 

 cent of the cases and from the fifth, sixth and seventh cervical 

 nerves only in over 30 per cent, that is fifth, sixth and seventh 

 cervical nerves may contribute in over 86 per cent. 



