180 NAOKI SUGITA 
3. MATERIAL 
Series I (Litters A, B, C, D, and E, table 1) 
Procedure. In each litter, half of the young were selected for 
the experiment and marked with hectograph ink on the back and 
the remaining individuals were used as the controls. The young 
under experiment were taken away from'the mother each day 
and kept packed in cotton in a warm place, but without any food 
or water, for the time which had been determined. Table 1 
contains the records of the number of hours during which each 
test individual in this series was isolated each day. 
Litter A (born October 16, 1916) was composed of nine young. 
Five (ce, a, d, f, and h) were subjected to experiment and were 
separated from the mother daily beginning on the very day of 
birth, the foodless interval being increased day by day, as recorded 
in table 1. Sundays were excluded from any experimentation, 
The duration of starvation, daily and total, and the age at which 
the animals were killed is recorded also in table 1. Four controls 
(b, e, g, and 1) were also killed one by one at the same’ages as the 
test animals. The total hours of isolation, the average per day, 
and the percentage of hours isolated during the total life of the 
individual in hours, are given in the lower part of the table. 
As the young are not fed continuously, even when they were 
with the mother, this percentage will but roughly indicate the 
grade of underfeeding to which the young were subjected. ‘They 
were killed for examination at the ages of 3, 4, 9, 11, and 15 days 
(see X in table 1). 
Litter B (born October 15, 1916) consisted of ten young. Five 
(a, ec, e, f and i) were separated daily from their mother, as in the 
case of Litter A, and the remaining young (b, d, g, h, and j) were 
used as controls. The experiment was begun at the age of one 
day in Litter B, a day later than in the case of Litter A. They 
were killed for examination at the ages of 4, 8, 11, 12, and 19 days. 
Litter A and B represent groups in which mild starvation was 
instituted from a very early age. 
Litter C (born October 18, 1916) was composed of seven young, 
of which four (a, c, d, and f) were used for experiment and three 
