io6 Journal of CoDiparativc Neurology and Psychology. 



and those eccentrically located might well be sheath cells. The 

 nature of these cells therefore is not definitely settled, and is a 

 problem of great importance. For if it is conclusively proved 

 that they are nerve cells, the structural independence of the 

 neurone and its genesis from a single ganglion cell can no longer 

 be maintained. By a series of degeneration experiments I have 

 attempted to solve the problem. 



2. THE RESULTS OF DEGENERATION EXPERIMENTS. 



If all of the nerve fibres in the palate of the frog are proc- 

 esses of the nerve cells situated either in the brain or in the sen- 

 sory ganglion of the seventh cranial ner\^e, they should, when 

 isolated from these cells for some weeks, degenerate completely, 

 being separated from their only trophic centers. If, how- 

 ever, there are peripheral nerve cells in the palate, these 

 as well at the fibers connected with them should remain 

 histologically unchanged. To determine which of these as- 

 sumptions is correct the following method suggested itself: 

 To sever the palatine nerves from all connection with their 

 central cells, and after the expiration of a period sufficient 

 for complete degeneration, to attempt the demonstration of 

 the peripheral networks by means of methylene blue. The 

 chief difficulty connected with this method lies in the well known 

 fickleness of the stain, a factor which might lead to negative re- 

 sults. I therefore experimented with normal animals until I 

 was able to obtain regularly a good percentage of successful 

 preparations. It was found that the subepithelial and perivas- 

 cular networks take the stain very quickly as they are in close 

 proximity to the blood vessels and capillaries, through the 

 walls of which the stain passes to the other tissues. The chief 

 point in getting good preparations therefore, is the removal and 

 fixation of the tissues as soon as possible after the stain has 

 passed through the capillaries. If one waits until the larger 

 nerves are impregnated, the color will have disappeared from 

 most of the finer elements. 



As is well known, methylene blue is a specific stain for 

 degenerated myelin, and Bethe has proved that the neuro- 



