Abstract
For the purpose of computing the portion of sensitivity in the mammary duct area in mice 35 days of age, female mice were divided into three groups: (1) a spayed and estrogen-treated group, (2) an estrogen-treated group, and (3) an intact group. A standard dose of estrogen was given from 20 to 35 days of age. At 35 days of age areas of mammary ducts were measured. Based on the explanation of the variance of the mammary duct area in the three groups, analysis was made.
The portion of estrogen factor was approximately 10 per cent in the estrogen-treated group and 30 per cent in the intact group. The error portion was estimated to be 4 per cent in both groups. Thus the portion of sensitivity was estimated to be 86 per cent in the estrogen-treated group and 66 per cent in the intact group. The results obtained suggest primarily that emphasis should be placed on the sensitivity rather than the estrogen stimulator for mammary growth and that the use of estrogen-treated mice may be efficient than the use of intact female mice, when selection for mammary parenchyma is intended.
The author is grately indebted to Dr. M. NAITO for his kind advice on the work.
