268 journal of Comparative Neurology and Psychology. 



alterations in the central stump are just beginning. Too early 

 an examination of the material may thus lead to erroneous con- 

 clusions. 



The changes in the ventral root are less marked than in the 

 mixed nerve, and until the last twenty years these structures were 

 often reported normal (Vulpian'68-'69, Dickinson '68, Dejerine 

 and Mayor '78, Dreschfeld '79, Friedlander and Krause 

 '86). Atrophy of the ventral roots was reported by Berard ('29), 

 TiJRCK ('53), Genzmer ('76), Hayem and Gilbert ('84), and 

 Edinger ('88); and during the last two decades has been quite 

 uniformly observed (Kahler and Pick '80, Reynolds '87, Mari- 

 nesco '92 and Wille '95). According to Reynolds the atrophy 

 is due to an increase in the proportion of the small fibers, while in 

 two of Wille's cases it was due to a decrease in the total number. 

 On his forty dogs Homen found a decrease in the ventral root 

 fibers within the spinal cord. There was also a slightly larger 

 proportion of small fibers on the operated than on the normal side. 

 That some fibers degenerate and disappear from the ventral roots 

 after the section of the mixed nerves has also been demonstrated 

 by the Marchi reaction in animal experiments (Darkschewitsch 



'96, ReDLICK '93, MoSCHAEW '93, CaSSIRER '98, CeNI '99, VAN 



Gehuchten '03). 



The dorsal roots have undergone changes very similar to those 

 in the ventral roots; the authors usually describe them together 

 and in identical terms, so that the account just given of the latter 

 would, with the following exceptions, serve equally well for the 

 former. Dickinson ('68), and Friedlander and Krause ('86) 

 found a considerable diminution in the number of dorsal root fibers 

 although in both cases the ventral roots were reported practically 

 normal. Marinesco ('92) also found more advanced atrophy, 

 and Darkschewitsch ('96) more degenerating fibers in the dorsal 

 than in the ventral root. The roots of the spinal nerves are sub- 

 ject to considerable normal variation in size, so that a large root 

 might suflPer considerable atrophy and still appear normal; and 

 this is, no doubt, in large part responsible for the conflicting state- 

 ments to be found in the literature. 



It is obvious from the foregoing account that the roots show less 

 pronounced alterations than the central portions of the severed 

 nerve trunks. Friedlander and Krause's ('86) statement of 

 this relation is worth some attention. We have already described 



