Progress on the science of menstruation—at last

HISTORY OFFERS no shortage of unhinged takes on menstruation. In 77AD, Pliny the Elder claimed that contact with menstrual blood would turn crops barren and drive dogs mad. A medieval medical text warned that the presence of menstruating women would make men ill, and that sex with them would cause cancer of the penis. In the first half of the 20th century, some theorised that periods contained toxins that could wilt flowers.