Ranson, Alterations in Spinal Ganglion Cells. 143 



very loose cellular connective tissue, and the cells which remain 

 are predominantly large cells. As time goes on the connective tissue 

 contracts, the spaces are obliterated, and the large cells, no longer 

 separated by so many small cells, come to lie much closer together 

 than in the normal ganglion. This condition is very obvious by the 

 20th day, at which time the degeneration is almost complete and 

 the majority of the surviving cells have returned to their normal 

 appearance. Figs. 1 and 2 are representative areas from the con- 

 trol and ''operated" ganglia of a rat which survived 20 days. 

 The large cells have undergone some atrophy. The disappearance 

 of the small cells and the approximation of the large ones is obvious, 

 yet the contrast is less marked in the illustration than that which 

 one finds in following through a series of sections of these two 

 ganglia. 



Perhaps a more satisfactory method of showing this relation is 

 by means of a differential count. A difficulty in the way of such 

 a count is that size is not the only point of differentiation between 

 the two types of cells. For, as has been said, there are cells of 

 medium size which because of other characteristics belong with the 

 large cells, and other medium sized cells which belong with the small 

 ones. On this account it is not possible to make an altogether 

 satisfactory differential count on the basis of size alone. ISTever- 

 theless, it is only by the use of such a rigid objective criterion that 

 one can rule out all possibility of personal bias. Accordingly, in 

 making the count a mean diameter of 20 microns was accepted as 

 an arbitrary dividing line between the two types. The majority 

 of the large cells have a greater diameter than this, the majority 

 of the small cells less. In making this count use was made of an 

 ocular net micrometer ruled in squares in such a way that with the 

 combination of the Zeiss oil-immersion lens and 12 eye-piece the 

 sides of these squares corres^wnded to the chosen diameter. In this 

 way it was possible rapidly to measure each cell and determine to 

 which class it belonged. Two counting machines w^ere used, the 

 large cells being registered on one, the small cells on the other. Four 

 sections from each ganglion were thus subjected to a differential 

 count. These sections were taken at random from different parts 

 of the ganglia. 



