MEDULLATED NERVE FIBERS 433 



cord by way of the ventral root they would have degenerated 

 when their central connections were severed. 



If fibers of this group were closely connected with fibers in the 

 dorsal root, section of the dorsal root might produce a degenera- 

 tion such as was noted by Braeunig. This connection might be 

 of two types. The recurrent fibers of Sherrington might be 

 affected by retrograde degeneration if their central processes in 

 the dorsal root were severed. "Or, if branching fibers occur in 

 which one process enters the spinal cord by the dorsal root and 

 the second b}^ the ventral root, a similar degeneration might 

 follow section of the dorsal root. 



It remains for us to consider the possibility of localizing with- 

 in the spinal ganglion the neurone bodies with which our medul- 

 lated nerve fibers are united. We are able to refer to certain 

 experiments in which the same region of the spinal ganglion is 

 affected. Kleist ('04) after section of certain dorsal roots found 

 that in a region on the posterior aspect of the proximal" part of 

 the ganglion the degenerative changes in the nerve cells were 

 much more marked than in other parts of the ganglion. The 

 spinal nerves were not cut in Kleist's experiments. The location 

 of this region of extreme degeneration corresponds approxi- 

 mately with that to which I was able to trace the intact ventral 

 root fibers. I am not able, however, to suggest any relation 

 between the presence of intact fibers in the operated ventral 

 root apparently arising in this region and the excessive degenera- 

 tion noted bj^ Kleist. Such causal relation may exist. 



Numerous investigators have noted the presence within the 

 spinal ganglion of certain cells which did not degenerate after 

 section of the spinal nerves. Ranson ('09) in his discussion of 

 alterations in spinal ganglion cells, corroborates the findings of 

 earlier investigators in that he notes the presence of non-reactive 

 nerve cells in the spinal ganglia of the white rat. Hanson de- 

 scribes these cells as of a medium size and with a clear protoplasm 

 with large chromatic granules. These cells are not numerous, 

 constituting a small percentage of. the total number of nerve cells 

 in the spinal ganglion and are scattered through the ganglion. 

 Ranson agrees with Cox ('98) and with Warrington and Griffith 



