Abstract
Summary
1. Beginning at the age of 2 weeks, 122 non-breeding male strain C3H mice were treated with estrogen for varying periods of time. At the end of the specified course of injections the mice received no further treatment until they died or were sacrificed. 2. Four weekly doses of 100 rat units of estrogen produced no mammary gland carcinomas; 8 and 12 weekly doses of 100 rat units produced a low incidence of these tumors. 3. After 16 weekly doses of 100 rat units of estrogen had been given a relatively high percentage of carcinoma of the mammary gland developed; the administration of 20 weekly doses or an average of 32.7 weekly doses of 100 rat units did not raise the incidence of tumors above this level. 4. Three thousand rat units of estrogen administered over a period of 3 days at the age of 2 weeks produced no tumors.
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