Hatai, Spznal Ganglion Cells in the Rat. 7 
cells in several kinds of mammals in adult and embryonal stages, 
but does not give separate measurements for the small and 
large cells. 
From the observation of these two authors, it is known 
that the spinal ganglia of all vertebrate animals thus far exam- 
ined contain two kinds of the cells. The question arises, 
whether all of these cells are functional or not, and, if functional 
what is indicated by this veriation in size? To assist in form- 
ing an opinion on this point let us first describe the internal 
structure of these cells and make a comparison between their 
structural differences. 
III. INTERNAL STRUCTURE OF SPINAL GANGLION CELLS. 
Different arrangements of the stainable substance in the 
spinal ganglion cells according to the different sizes of the cell- 
bodies have been noticed by several authors, and according to 
these arrangements, they have tried to classify the cells. Some 
of these classifications are as follows: 
Nisst’ found in spinal ganglion of rabbit, the different 
classes of cells which he has distinguished and recognizes the 
great differences in the size of the cell-body. He further notes 
a number of varieties of cells characterized by the size of the 
masses of stainable substance. Using this as a criterion he 
distinguishes (1) those in which the stainable substance consists 
entirely of large masses, (2) those in which it consists of 
very small masses, (3) those in which both !arge and small 
masses are present. In this case the two sizesof stainable masses 
can be present in equal numbers or either the smaller or the 
larger may be in excess. (4) Both large and small masses of 
stainable substance may be present with a peculiar arrangement 
of the masses of a given size thus imparting to, the cell a char- 
acteristic appearance. 
1 NissL.— Ueber die sogenannten Granule der Nervenzellen. Meurolog. 
Centralblatt, ’94, Nos. 19, 21, 22. 
Ueber die Nomenclatur der Nervenzellenanatomie und ihre nachsten Ziehle. 
Neurolog. Centralblatt, ’95, No. 23. 
