NON-MEDULLATED NERVE FIBERS 79 



in large numbers. "It is in these small cells that the most ex- 

 treme alterations are to be found. The nucleus is strikingly 

 eccentric; in most cases it causes a distinct bulging of the cell 

 outlines, and in many it appears to be indenting the cell from 

 without. The chromatic substance is completely dissolved except 

 for a dense ring which persists at the periphery of the cell and a 

 small clump sometimes found near the nucleus. Even at this 

 stage, five days after the operation, it is clear that some of these 

 small dark cells have disintegrated." A differential count made 

 twenty days after the operation showed the same number of 

 large cells in the normal and 'operated ganglia' (an average of 

 29 to a section) but the number of small cells was reduced by one- 

 half (from 42 to 19.5 per section). From these observations it 

 is clear that following the division of a nerve the small cells of the 

 associated ganglion react exactly as if their axons ran into the 

 nerve and had been divided when the nerve was cut. 



Confirmation of these results is to be had from another series 

 of experiments (Ranson '06). The dorsal ramus of the second 

 cervical nerve was cut in eleven white rats, eight of which were 

 12 days old and three were adult specimens 140 days old. Enu- 

 merations were made of the spinal ganglion cells in nine and of 

 the dorsal root fibers in ten of these animals after from two to 

 four months. Similar counts were made on normal animals for 

 control. There was a reduction in the number of spinal ganghon 

 cells as a result of the operation from an average of 8451 in four 

 normal specimens to 4124 in nine 'operated' ganglia. This loss 

 was a very constant one and there was no greater variation among 

 the operated ganglia than among the normal ones. It was shown 

 that in the operation on 12 day old rats approximately 1500 medul- 

 lated afferent fibers were cut and in the operation on rats 140 

 days old approximately 2500. This variation in the number of 

 medullated axons cut had no influence on the number of cells de- 

 generating, and moreover, it is obvious that even the larger 

 number is not sufficient to explain the degeneration of over 4,000 

 ganglion cells. More surprising still was the observation that after 

 more than 4000 ganglion cells had completely degenerated there 

 was an average loss of only 473 dorsal root fibers. Since the dor- 



