I42 DONALDSON. [VoL. IX. 
to determine whether the process goes on in the same manner 
in a brain remaining within the skull as in a brain which has 
been removed. 
Parts of Encephalon.— Up to this point we have been con- 
sidering the reactions of the subdivisions of the brain taken 
in the normal proportions, as represented in a hemiencephalon. 
We shall now take up separately the several parts of the 
brain. The subdivisions examined were as follows :— 
The stem, consisting of the oblongata, pons and quadri- 
gemina. The cerebellum, separated from the stem at the base 
of its peduncles ; and the cerebrum, the portion lying in front 
of the quadrigemina. The cerebral hemispheres were without 
the gray caps of the olfactory lobes and without the hypophysis. 
After 153 days in 2% bichromate of potash the weight rela- 
tions were as follows :— 
TABLE 14. 
R. HEMISPHERE. L. HEMISPHERE. CEREBELLUM. STEM. 
PEr- PEr- PErR- PrEr- 
SERIAL| FRESH 
CENTAGE CENTAGE CENTAGE CENTAGE 
No. WEIGHT. 
GAIN. Gain. GAIN. GAIN. 
82 42.80 + 35.1 44.50 + 37.5 12.25 + 29.3 19.61 + 32.8 
83 41.55 33-1 39-73 31.6 13.00 28.1 20.03 29.7 
84 32.55 3257 32.69 33-4 12.07 26.8 18.43 32.9 
Avg. = 33.6 Ae i201 —— no 
Average of both Hemispheres = 33.8. 
From the consideration of these figures we see that the 
cerebrum increases most in weight, next the stem, and last the 
cerebellum. These parts of the brain represent varying mixt- 
ures of gray and white matter, and for this reason might be 
expected to react differently. From tests made for the purpose 
it has been found, as might be expected, that the increase in 
the weight of the gray matter is only about half of the white. 
Exact figures have little value in this instance, because gray 
matter can never be obtained pure, and its increase in weight 
is modified by the proportion of white substance in it. In this 
