A. J. Carlson 345 
thickness and stained on the same slide with erythrosin and methylene 
blue according to Held, 50% alcohol or a weak solution of alum being 
used for differentiation. 
The retine from the stimulated and the resting eyes thus prepared 
show a constant difference in the amount ond appearance of the Nissl 
substance in the cells of the ganglionic and the bipolar cell layer. The 
ganglion cells of the stimulated retine are poorer in Nissl’s substance, 
the Nissl’s granules present are less distinct than in the resting retine, 
and the protoplasm of the cell bodies take a diffuse blue stain. Any 
shifting in position of the Nissl’s substance cannot be made out. In 
the resting state the coarsely granular chromophile substance fills the 
whole cell body, being massed particularly heavy around the periphery. 
In some cases the cells of the stimulated retine gave an appearance 
as if the Nissl’s substance first disappeared from the center of the 
cell (fig. 3 b), but this appearance‘ is probably due to the greater 
abundance of the substance around the periphery under normal con- 
ditions. But though this difference in the Nissl’s substance is shown 
in all the retine examined, it is by no means equally marked in all 
the preparations; and in the same preparations all the ganglion or 
the bipolar cells of the resting retina do not show an equal abundance 
of Nissl’s substance, nor do the cells in stimulated retina show an equal 
paucity of it. In fact, in nearly all the preparations, cells can be 
found in the resting retina which have no greater amount of chro- 
mophile substance than is possessed by some cells in the stimulated 
retina, though the difference between the extremes of the two retine 
as well as the difference in the blue coloration of the ganglionic layers 
as viewed under low power is easily discernable in all. Figure 1 a and 
b are from a preparation showing an average difference in this total 
effect, while figure 2a and b are from a preparation that showed the 
least difference. Figure 3 a and b are cells from the ganglion layers 
of the preparation represented in figure 1. The difference in the 
chromophile substance between figure 3 a and 3 b is rather more than 
shown by the majority of the preparations. Figure 4 a, ganglion cell 
from a resting retina, and 4b, ganglion cell from a stimulated retina, 
may be considered typical of the difference in chromophile substance 
of the preparations. Apart from this difference in the Nissl’s sub- 
stance, the nervous elements of the resting and the stimulated retine 
appear to show no constant variation. In some of the preparations 
the cell bodies of the ganglion and the bipolar cells appear somewhat 
smaller in the stimulated retina, and a greater number of cells are 
slightly shrunken; but the fact, that in the resting retina the cells 
24 
