488 Journal of Comparative Neurology and Psychology. 



cervical nerve, that is to say, somewhere about the level of the 

 third nerve as described by Bischoff. 



From two individuals the anterior roots of the second, 

 third, fourth and fifth cervical nerves were removed, stained in 

 osmic acid, imbedded, after the usual preliminary treatment, 

 in paraffin and cut into lO /j. sections. All of the roots were 

 composed principally of large medullated fibers, having a diam- 

 eter varying from lO to 20 /j., but in addition there could be 

 observed in each a small number of fibers whose diameter was 

 less than 4/1, many of them not exceeding 2/1. Even on 

 superficial examination, however, it could be perceived that 

 these small fibers were much more numerous in the lower than 

 in the upper roots and counts which were made of the fibers 

 with a diameter of 4/i or less gave the following results. 



Roots Rat No. I 



Rat No. II 



It is evident then, that a sudden increase in the number 

 of small medullated fibers occurs in the anterior root of the 

 fourth cervical nerve, that is to say, in the nerve immediately 

 below the emergence of the last root of the spinal accessory. 



The rami communicantes were next dissected out in three 

 other rats and placed in osmic acid. The rami which were 

 connected with the three uppermost cervical nerves failed to 

 show any blackening with the osmic and may consequently be 

 regarded as composed solely of gray rami fibers. With the 

 succeeding rami, however, the case was different, a distinct 

 blackening taking place, and on sectioning these rami it was 

 found that they were largely composed of medullated fibers, a 

 considerable number being of large size, measuring from 10 to 

 16/iin diameter, scattered among which were numerous fibers, 

 arranged to some extent in groups and of the same general 

 diameter as the small fibers of the anterior roots. Counting 

 these, it was found that they numbered in one individual 195 

 in the fourth ramus and 220 in the fifth. 



