128 Journal of Coinparafive Neurology and Psychology. 



Degeneration." The operated ganglia, along with the control ganglia 

 of the opposite side, were removed after varying periods and fixed 

 in Hatai's flnid (Ilatai '01). After penetration with paraflin, they 

 were cnt in serial sections 6 microns thick and stained with toluidin- 

 blue. The 18 rats were allowed to survive the O'peration for different 

 lengths of time, which were as follows: 5, 0, 7, 8, 1), 10, 12, 16, 17, 

 20, 25, 27, 31, 34; 37, 41, 44, and 57 days. 



Types of Cells. 



A most exhaustive account of the cytology of the spinal ganglion 

 cells and of the axonal reaction, resulting from the lesion of their 

 peripherally directed processes, is to be found in the publications 

 of Lugaro. His contributions to this subject, which have appeared 

 from time to time during the past ten years, have been summarized 

 by David Orr ('04) from whose excellent review the following 

 citation has been taken. According to Lugaro, there are five cell 

 types in the spinal ganglia of mammals: (1) Large clear cells, 

 with granuliform chromophile elements scattered almost equally, 

 throughout the protoplasm with a slight increase toward the cell 

 periphery. The nucleus is large and clear and there is a definite 

 j^erinuclear and peripheral clear zone. (2) Large and medium 

 sized cells with very fine chromophile elements, which are larger, 

 however, at the periphery of the cell. Other characteristics as in 

 Type 1. (3) Small dark cells with very fine chromophile elements, 

 which are larger around the nucleus with which they are in contact. 

 The fundamental substance and the nucleus are diffusely colored. 



(4) Small and medium sized clear cells with chromophile elements 

 somewhat large and few in number. The nucleus is clear and 

 separated from the chromophile substance by an achromatic zone. 



(5) Large clear cells with elongated chromophie elements lying 

 concentrically around the nucleus in parallel planes. The nucleus 

 is always excentric. 



There can be no doubt but that cells corresponding to all these 

 types can be seen in the spinal ganglia of various animals ; but the 

 number of transitional forms is so great that anv such elaborate 



