Seventy DDOU micewith the age of about 20 days. were raised separately or gregariously for 70 days to study the effects of gregariousness and sexual combination on the brain development. The animals were divided into 7 groups according to the number and sex of the mice in the separate cages, namely, one male or one female as the control, one couple, two males, two females, three couples and six couples. The mice were fed with the standard foods under the same conditions throughout the experiment. The animals were sacrificed at the 71st day and the brain weight, the weight percent of the brain to the body weight were calculated. The water content of the brain and the increasing rate of the body weight were also compared.
Following were the results:
1. The brain development of the mice raised with others was better than that of in solitude. The magnitude of the brain development was in order of three couples, six couples, one couple and one mouse.
2. The mice raised with the opposite sex showed a tendency of better brain development than that of with-its own sex.
3. There were no differences in the water content of the brain and the increasing rate of the body weight between all groups.
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