No. 1.] HARDENING REAGENTS. 143 
instance the gray matter was the cortical gray of the sheep, 
which, of course, contains a large proportion of white matter. 
A determination of the percentage of solid matters in the sub- 
divisions of the fresh encephalon yielded the following :— 
TABLE I5. 
Percentage of solids in the subdivisions of the fresh encephalon: — 
SERIAL No.| R. HEMISPHERE. L. HEMISPHERE. CEREBELLUM. STEM. 
98 21.9 20.3 21.5 25.6 
99 21.2 20.0 18.9} 25.6 
74 21.0 20.6 20.9 27.3 
75 21.0 21.4 21.0 26.7 
IOI 20.9 20.2 18.9} 26.3 
87 20.8 21.0 21.5 2758 
86 20.3 20.4 20.2 26.7 
Avg.= 21.0 = 20.5 = 21.0 == 2055 
As will be seen, this shows the percentage of solids in both 
hemispheres and in the cerebellum to be about the same, while 
the percentage in the stem is much higher. 
Taking the percentage of solids as an index of the proportion 
of white matter, and remembering that under the influence of 
bichromate of potash solution, the white matter increases most 
in weight; we should expect that the order in which the 
subdivisions would increase in weight, would be the stem most, 
and the cerebrum and cerebellum in about the same degree. 
As a matter of fact under the conditions of our experiments, 
the cerebellum increases least, the stem next, and the cerebrum 
most. The strong system of supporting tissues in the stem is 
doubtless one influence acting against its greater enlargement. 
Whether the laminated condition of the white matter in the 
cerebellum, is a cause of the failure to increase in weight, or 
whether the composition of the medullary substance is there 
different, has yet to be determined. As we shall see when 
1 The low percentage of the solids in the cerebellum in the instances indicated 
is sufficiently noticeable to call for explanation, but at present none can be given. 
The average for the solids of the cerebellum without these two low figures is 
21.0% With them it is 20.4%. 
