BRACHIAL PLEXUS OF NERVES IN MAN 329 



heads of the median nerve respectively. It will thus be seen that 

 the nerve may contain fibers from all the spinal nerves entering 

 the plexus. 



In 150 of the 175 plexuses of my series, the median nerve is 

 formed in the usual way by two heads, as described above 

 (fig. 5) . The lateral head arises from the lateral fasciculus of the 

 plexus which is formed by the union of the ventral branch of 

 the cephalic trunk with the ventral branch of the intermediate 

 trunk (figs. 1, 2, 3). There are two other plexuses differing 

 from the above only in that the lateral fasciculus of the plexus 

 from which the lateral head arises receives fibers from the caudal 

 trunk of the plexus. One of these plexuses belongs to type C 

 (fig. 6), and the other to type G of plexus (fig. 8). Th^re are 

 then 152, or 86.85 per cent, of the 175 plexuses of my series in 

 which the median nerve may be considered to arise by two heads 

 in the usually described manner. 



In the remaining 23 plexuses of the series, the median nerve 

 is formed in a different way. 



In 7 of these instances, the lateral head of the median is formed 

 by the ventral branch of the cephalic trunk, after giving off the 

 musculocutaneous nerve, joining with the ventral branch of the 

 intermediate trunk (seventh cervical nerve) (fig. 18). In another 

 case, the ventral branch from the intermediate trunk joins the 

 medial head of the median, giving off also the lateral head of the 

 ulnar, (fig. 15), but sending no branch to the medial head of the 

 median. In three of the above cases, the branch from the seventh 

 cervical nerve divides and goes to the medial head of the median 

 as well as helping to form the lateral head (fig. 16). In one of 

 these latter there is an additional branch to the medial head of 

 the median nerve from the ventral division of the seventh 

 cervical nerve, which gives off also from its dorsal division the 

 lateral head of the ulnar nerve, and this also connects with the 

 medial head of the median. 



There is a ninth plexus in which the lateral head of the median 

 nerve arises from the ventral branch of the intermediate trunk 

 (seventh cervical nerve) of the plexus. The ventral branch of 

 the cephalic trunk (fifth and sixth cervical nerves) does not con- 



