• BRACHIAL PLEXUS OF NERVES IN MAN 335 



through the arm for only 75 plexuses, in 18 of these the musculo- 

 cutaneous nerve gives off a branch to the median nerve. (In 

 one of these instances the musculocutaneous arises from the 

 cephalic trunk formed only by the fourth, fifth, and sixth cervical 

 nerves). In one of the above instances, the musculocutaneous 

 also receives a branch from the median nerve. 



In addition to these, in one of the plexuses where the musculo- 

 cutaneous nerve arises from the median nerve as described above, 

 it gives off a branch which joins the median nerve further distad. 

 This branch arises from the median nerve distal to the point 

 where the musculocutaneous would normally pierce the coraco- 

 brachialis muscle which it does not pierce in this case. 



Although these records show that in nearly a quarter of the 

 plexuses the musculocutaneous nerve gives off a branch in the 

 arm which joins the median nerve, I do not believe that such a 

 relation exists as frequently as this, for undoubtedly some of the 

 records were made because of the occurrence of this anomaly. 

 On the other hand, in 100 plexuses of my series the records were 

 not preserved for the arm so that I cannot be positive that there 

 may not have been more cases where the communication existed. 

 If there were no more instances among the 175 plexuses of my 

 series, which is unlikely, the anomaly is found in this series in 

 10.28 per cent of the 175. In the 75 where the records are com- 

 plete, it is found in 18 or in 24 per cent of the cases. The truth 

 probably lies somewhere between these two extremes. 



Testut ('84) found a branch from the musculocutaneous nerve 

 to the median nerve in 38 instances out of 105 examined, or 36.19 

 per cent, which is considerably larger than in my series. 



In 3 cases, or in 4 per cent of the 75 complete records, the 

 median nerve in the arm sends a branch to the musculocutaneous 

 nerve. In one of these, as already noted, the median also re- 

 ceives a branch from the musculocutaneous. Testut, found a 

 branch from the median to the musculocutaneous nerve in only 

 two out of 105, or in less than 2 per cent, while Villar ('88) found 

 such a branch in 3 out of 37 cases, or in 8.10 per cent. 



In my series of 175 cases, the musculocutaneous nerve may 

 receive fibers from the fourth, fifth and sixth cervical nerves 



