A QUANTITATIVE STUDY OF THE INHIBITION OF ESTRADIOL BENZOATE BY PROGESTERONE IN THE BABOON (PAPIO PORCARIUS)

THE QUANTITATIVE INHIBITION of estrogen by progesterone has been estimated exclusively by means of histological examination of the endometrium in primates. In the baboon, however, it is possible to determine the quantitive inhibition of the two ovarian hormones by means of the sexual skin and the time of the onset of bleeding after the last injection of the combined hormones. When estradiol benzoate is administered to a prepubertal or castrate baboon the perineum swells or turgesces, and with effective doses it reaches its maximum size in 7 to 10 days. When the hormone is withheld the perineum returns to its resting level about the 10th day, and between the 10th to 16th days after withdrawal of the estrogen bleeding supervenes (2, 3).