84 



JOURNAL Of Comparative Neurology. 



TABLE X. 



The proportion of ventral root to dorsal root fibers contained in tbe Vllth, 

 Vlllth, and IXth nerves of four specimens. 



Wt. of frog, 

 grams. 



23 

 63 

 48 



59 



Ventral root 

 fibers. 



1088 



1453 

 2471 

 2287 



Dorsal root 

 fibers. 



1754 

 2656 



4387 

 4000 



Proportion. 



^~^'li\j^- virescens, 

 I-I-75J 



These proportions are interesting because they seem to in- 

 dicate that, whatever the size of the animal, there exists an al- 

 most fixed relation between the inervation of the tissue of the 

 leg by sensory and motor fibers. This similarity in the propor- 

 tion of ventral to dorsal root fibers fails if there be included in 

 the sums, the ventral and dorsal root fibers of other nerves than 

 those which go to form the sciatic. Even when the Vlth nerve 

 alone is included the proportions become more varied. 



Another point may be noted with regard to the roots. 

 The average diameter of the fibers of the same root differs for 

 the different nerves. Birge noted for the European frog that 

 the greatest average diameter for ventral root fibers is possessed 

 by the Vllth nerve and the least average diameter of ventral 

 root fibers by the Illrd. This is found to be true also for the 

 specimens here investigated. In addition it may be added that 

 the least average diameter of dorsal root fibers is to be found in 

 the dorsal root of the 1st nerve and usually the largest of those 

 very large dorsal root fibers before mentioned are to be found 

 in the dorsal root of the Vllth. For the ventral root of the 

 Ilird, it may be said that the few fibers it contains of the ordi- 

 nary ventral root type are as large as the average of those of 

 the ventral roots of the other nerves. Its fibers however are 

 sharply divided into two types and the average diameter of its 

 fibers is reduced because of the presence of a very large num- 

 ber of that type of small fibers which Gaskell ('89) and others 

 have described as destined to pass to the sympathetic system 

 and which, in the preparations here used, can be seen to largely 

 compose the rami communicantes. 



Birge obtained the average diameter of the fibers of a 



