4 jJournaL oF CompPARATIVE NEuROLoGY. 
has a weak penetrating power. CARNoY’s mixture gives 
very satisfactory results. This isa very simple but most safe 
fluid for general use. The author’s own mixture gave quite as 
satisfactory results as Carnoy’s. Especially for the study 
of differences between the axone and dendrites to be else- 
where described, the author’s fluid is preferable to any of 
the other fluids. In this fluid, the neurosomes of the axis 
cylinder stain very deeply but the neurosomes of the den- 
drites stain only lightly. The cell-bodies keep quite a good 
shape and never swell, as in the case of CARNoy’s fluid. 
But the author believes with Ewinc' who studied ganglion 
cells in the human nervous system, that ‘‘ more important than 
the choice of any particular fixative is the care in handling the 
tissue, and the exclusive dependence upon thin pieces of tissue, I- 
to 2mm., thick, which can be rapidly penetrated by all agents.” 
For staining, the author most often used thionin and 
toluidin blue, but a methylene blue was occasionally used. 
Good results were obtained from each of the staining fluids. 
A counter-staining fluid was always used in the present 
work. For this purpose, erythrosin and eosin were tried and 
erythrosin gave the more satisfactory results. 
Il. MEASUREMENTS OF THE CELLS IN THE SPINAL GANGLION.. 
Briefly, the spinal ganglion cells in the white rat form two 
groups distinguished, both by their chemical affinities and struc- 
tural form, as has already been mentioned. The general form 
of the cell in section is somewhat oblong, this shape, however, 
is variable, and some of the cells are quite circular in outline. 
For the most part, the smaller cells which are surrounded by 
thick connective tissue or compressed among larger ganglion 
cell-bodies show triangular, polygonal or very rarely a spindle. 
form. Very probably these irregular shapes result from the 
action of the preserving fluids. 
The size of the cells in the cervical spinal ganglia (ganglia 
1 EWING, J —Studies on Ganglion Cells, Arch. of Neurol. and Psycho- 
pathology, Vol. 1, No. 3, 9S. 
