"It had already been known for several decades that sex hormones were able to suppress ovulation in animals. Ludwig Haberlandt, an Austrian physiologist is sometimes called the grandfather of the pill. Indeed, in 1921 he found that rabbits and guinea pigs became temporarily sterile after transplantation of ovaries from pregnant animals. These experiments paved the way for pharmacological studies on the effect of progesterone on ovulation. The anti-ovulatory effect of progesterone was demonstrated by A. W. Makepeace and co-workers in 1937 who injected progesterone in mated female rabbits. Large-scale experiments with progesterone, which hitherto had been extracted from animal ovaries became possible after Russell E. Marker, a professor of organic chemistry, found that progesterone could be manufactured from a substance named diosgenin, extracted from the root of a plant (Dioscorea mexicana) which grows in Mexican jungles."