Physiological Control of Population Growth

Abstract

MOUSE ova collected from the Fallopian tubes at the eight-cell stage have been consistently shown to develop to blastulae when cultivated in a purified medium¹. It has now been observed that if progesterone is added to this medium, all ova die when the concentration is 8 µgm./ml. or more. A proportion survive at 4 µgm./ml., while a concentration of 2 µgm./ml. is without apparent effect. Since Forbes² found a level of 5.2 µgm./ml. in human plasma it seemed possible that this action of progesterone, together with those described by Pincus³ and Ishikawa⁴, might provide a method of fertility control. However, when recently inseminated mice were injected with 10 mgm. of progesterone intraperitoneally on two successive days, there was no reduction in the number of free blastulæ or of implantation sites.