EXPERIMENTAL STUDIES ON THE MENSTRUAL CYCLE OF THE BABOON (PAPIO PORCARIUS). VI. THE EFFECT OF PROGESTERONE UPON THE FIRST PART OF THE CYCLE IN NORMAL FEMALE BABOONS1

IN A PREVIOUS study (I) it was shown that progesterone when repeatedly given in the first part of the cycle of a normal adult female baboon the turgescent perineum underwent deturgescence very rapidly and returned to its resting state. This resting condition could be maintained over a period the length of which was determined only by the administration of the progesterone. Further it was shown that if the total quantity of the hormone exceeded 15 mg. bleeding invariably occurred after withdrawal, the exact time of the onset of bleeding being determined purely by the quantity of progesterone used. If the total amount of progesterone happened to be less than 15 mg. then, after its induced resting state, the turgescent perineum rose rapidly without any microscopic evidence of bleeding. This experimentally affected cycle was invariably a prolonged one. The conclusion was arrived at that in a normal adult baboon deturgescence is a positive phenomenon initiated by progesterone or an allied substance.