Abstract
SUMMARY: Oestrone, oestradiol-17β and oestriol were administered by intramuscular injection to two men and four women. The amounts of oestrone, oestradiol-17β and oestriol excreted in the urine as a result of the injections were measured. The figures derived from these injection experiments have been used to speculate on the nature and the amounts of the oestrogens secreted by the ovaries during the menstrual cycle and by the placenta during pregnancy.