512 Cc. A. STEWART 
stock albino rats (presented in part in a Harvey Lecture, Decem- 
ber, 1916) which in general are in agreement with my own observa- 
tions upon normal animals. Only my own data are presented 
in this paper, however. This opportunity is taken to acknowl 
edge my indebtedness to Prof. C. M. Jackson for valuable 
advice given during the course of the present experiments. 
MATERIAL AND METHODS 
In the present investigation the brains of 64 normal (31 males, 
33 females, table 1), and of 29 test rats (19 males, 10 females, 
table 2) were used. Among the 64 normal rats are included 22 
individuals which also served as the direct controls for the test 
rats. The rats used were all Albinos (Mus norvegicus albinus) 
from the colony in the Institute of Anatomy here. 
The number and sex of the normal animals killed at the selected 
periods between birth and adult age are shown in table 1. Of the 
direct controls (table 2), 12 rats (8 &, 4 @) were killed at birth 
(average weight 4.7 to 5 grams), 9 rats (5 &, 4 2) at approxi- 
mately 10 grams, and one male at 12 grams body weight. 
The test rats were repeatedly starved by isolation from the 
mother for various periods as described elsewhere (Stewart, 
18b). In this manner 15 individuals (9 #, 6 2) were held 
approximately at birth weight for periods ranging from 5 to 18 
days; and 13 rats (9, 4 9) were permitted to increase slightly 
in weight reaching approximately 10 grams at 3 weeks of age. 
In addition one male was weaned when 21 days old, body weight 
10.5 grams, and was placed upon a limited diet of whole wheat 
(Graham) bread and whole milk. At 56 days of age this indi- 
vidual weighed only 12 grams. 
It will be noted that the average final body weight is prac- 
tically the same for the control and the test rats of each group 
(table 2). In comparing the data for the normal and the starved 
individuals, the slight differences existing in body weight have 
been disregarded. This seems justified since the error involved 
is small and cannot obscure the changes produced by the experi- 
mental conditions. Strictly speaking, however, a slight correc- 
tion should be made as previously noted (Stewart, ’18 b). 
