BRACHIAL PLEXUS OF NERVES IN MAN 325 



The lateral head of the ulnar nerve is found in 75 of the 175 

 plexuses of my series or in 42.85 per cent of them. Fifty-five 

 of these, or 31.42 per cent were group 1 plexuses, 16 or 9.4 per 

 cent were group 2 plexuses and 4 or 3.4 per cent were group 3 

 plexuses. The lateral head of the ulnar nerve is found in 55 of 

 the 110 plexuses of group 1 or in 50 per cent of them, in 16 of the 

 52 plexuses of group 2 and in 4 of the 13 plexuses of group 3 

 or 30.76 per cent of the group in each of these. If, however, we 

 entirely disregard the 30 doubtful cases in which a similar branch 

 has not been proved to join the ulnar but ends in the medial head 

 of the median nerve (fig. 20), we have a lateral head of the ulnar 

 occurring in 75 out of 145 cases or in 51.72 per cent of the cases 

 examined. If, on the other hand, we consider this branch to the 

 medial head of the median as representing the lateral head of the 

 ulnar, which I believe in the majority of cases it does, we have 

 a lateral head of the ulnar occurring in 105 of the 175 plexuses 

 or 60.00 per cent, which I believe to be more nearly the true 

 percentage. 



Walsh ('77), in an examination of 290 plexuses, found the 

 lateral head of the ulnar nerve absent in but 25 cases and in 13 of 

 these there was in place of it a branch arising from the seventh 

 cervical nerve above the clavicle which joined the medial fascic- 

 ulus of the plexus high up in the axilla. 



Spinal nerves that send fibers to the ulnar nerve 



The ulnar nerve probably, in all cases, receives fibers from the 

 eighth cervical and first thoracic and in those cases where the 

 second thoracic enters the plexus the possibility of this nerve 

 sending fibers to the ulnar nerve cannot be excluded. 



Besides the eighth cervical and first thoracic (or first and sec- 

 ond), fibers from the seventh cervical nerve may enter the ulnar 

 nerve in plexuses of types A and D. For, as has been shown, 

 fibers from the seventh cervical nerve pass to the medial fasciculus 

 of the plexus through the branch which is the distinguishing 

 characteristic of these types, and since the ulnar nerve arises 

 from the medial fasciculus, we cannot be sure that the seventh 

 cervical nerve does not take part in its formation. 



