138 Journal of Coiiiparafive Neurology and Psychology. 



smallest dark cells tliat fail to react. In the cat no cells nnder 25 

 microns, dark or clear, showed chromatolysis. They estimate these 

 non-reacti\'e cells as constituting from 7 to 13 per cent of all the 

 cells, according to the ganglion studied. 



In my preparations from the rat, which came to autopsy five 

 days after the operation, the chromatolysis is at its highest point 

 and the majority of the cells are greatly altered. It is therefore 

 not possible to determine whether the large or small cells were first 

 altered. It is in the small cells, however, that the most extreme 

 alterations are found. Fig. 3 illustrates some of these changes. 

 The nucleus is strikingly excentric, in most of the cases it causes 

 a distinct bvilging 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 

 perijihery 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, but 

 of this more will be said in connection Avith the phase of degenera- 

 tion. 



From what has ])een said it will be obvious that the changes wliich 

 appear in the small cells are characteristic of axonal reaction, and 

 there is nothing in the finer details of the chromatolysis to indicate 

 that it is due to any other cause than a lesion of the axons of these 

 cells. If we are to continue to place any confidence in the con- 

 clusions based on Nissl's axon-reaction; we are forced from these 

 facts to admit that the majority of the small cells possess axons 

 in the peripheral nerve, the numerical results to the contrary not- 

 withstanding. 



Concerning the phase of reaction in the large cells there is very 

 little to add to that which has been described by previous observers. 

 We have already mentioned the facts concerning the non-reacting 

 coarsely granular cells. There is but one other point of interest 

 in the chromatolysis of the large cells, namely, the absence of any 

 trace of clumping of the tigroid masses about the nucleus in the 

 preparations of the reacting ganglia of the rat. Fleming, Cox, and 

 Kleist have each seen and described this phenomenon; and there 



