BRACHIAL PLEXUS OF NERVES IN MAN 323 



Walsh ('77) personally examined 350 plexuses and entirely 

 overlooked this branch in the first 60 but once his attention was 

 directed to it he found it absent in only 25 of the remaining 290. 



The dissections in my series were made by students who were 

 not especially looking for a lateral head of the ulnar nerve, and 

 although the work was carefully done I feel quite confident that 

 in a number of cases there had been a lateral head to the ulnar 

 which could not be demonstrated at the time the plexus was 

 examined by • the investigator since the connection with the 

 ulnar had been broken in the dissection and the broken ends 

 could not be found. 



In some of these cases there remains a branch connecting 

 with the medial head of the median nerve and similar in all 

 respects to a lateral head of the ulnar nerve except that the 

 connecting fibers could not be demonstrated (fig. 34). There 

 are 30 such cases in my series. Walsh, however, found but 10 

 instances in which a similar branch failed to send fibers to the 

 ulnar nerve but ended exclusively in the medial head of the 

 median nerve. 



There are 8 other instances in which there is a branch which 

 joins the medial fasciculus of the plexus close to the point where 

 this divides into the ulnar and the medial head of the median 

 nerve. I have not been able to prove in these 8 cases that fibers 

 from this branch go to the ulnar nerve, but this is probably the 

 lateral head of the ulnar nerve since in all other similar cases I 

 have found by very careful dissection or by macerating the 

 plexuses in nitric acid that this branch sends fibers to the ulnar 

 nerve. Sometimes all of its fibers go to the ulnar nerve and 

 sometimes part to the ulnar and part to the medial head of the 

 median nerve. I therefore believe this branch always represents 

 the lateral head of the ulnar nerve and have so considered it in 

 this paper. In 6 of the above cases this branch arises from the 

 lateral fasciculus of the plexus (fig. 11) and in 2 from the seventh 

 cervical only. 



The lateral head of the ulnar nerve, in my series, passes, in 

 40 cases, as a single branch to the ulnar nerve (fig. 2), but in 

 28 cases it divides and sends one or more branches to the medial 



