282 yonrnal of Comparative Neurology and Psychology. 



a number even greater than the normal average for rats of that 

 age. The other three roots fall below the normal; in one case the 

 number goes as low as 1236. The average loss is 393 fibers or 

 17 per cent. 



The deficiency of fibers in the dorsal roots, associated with the 

 injured nerves, finds its counterpart in the degenerating fibers 

 which may be recognized by the method of Marchi (see p. 267). 

 According to recorded observations the degenerating fibers con- 

 stitute only a fraction of the total number. To what extent de- 

 generation occurred in our specimens can only be determined by 

 study of the roots with the Marchi method, because it is not possi- 

 ble to say what part of the fibers, enumerated in this investigation 

 have been formed since the operation as an attempt to repair the 

 damaged root. 



TABLE VII. 

 Showing the Relation of the Number of Dorsal Root Fibers to Spinal Ganglion 

 Cells in the Operated II C. Nerve of the White Rat. 



Table VII shows that in every case there are more than enough 

 spinal ganglion cells to account for the dorsal root fibers, although 

 in one case the excess of cells is not very great. By comparison 

 with the average normal ratio taken from Table II, it will be seen 

 that the ratio of cells to fibers is reduced in the operated nerves, 

 and that while in the normal nerve it is approximately constant 

 at one fiber to 3.2 cells in the operated nerves it shows much greater 

 variation. The table also shows that there is no constant relation 

 between the number of spinal ganglion cells destroyed by the opera- 

 tion and the number of dorsal root fibers which are found two 

 months later; and that, therefore, the loss of dorsal root fibers 

 cannot, without some qualification, be attributed to the degener- 



