A little over a hundred years ago the medical world experienced a flurry when the French anatomist Cuvier announced that menstruation could no longer be considered a distinctly human characteristic, since he had found (as had indeed a few forgotten authors before him) that female apes and monkeys share with women this periodic bleeding phenomenon. The menstrual process was therefore set down as a primate character, particularly since, as Heape first pointed out, the menstrual cycle in both monkeys and women involves identical changes of the reproductive organs.
The general biologist may concede that in its spectacular manifestations menstruation is a "primate character." But if one searches for fundamental or even for the more superficial physiologic causes, and if one investigates other mammals and even the lower vertebrates and attempts to discover what they have in common with man, anthropocentric ideas receive jolt after jolt. I propose to show the