The surplus: Aristotle, Galen and Pliny

Antiquity · c. 400 BCE – 200 CE

The Hippocratic writers of classical Greece worked from a simple and internally consistent model. Women were thought to have spongier flesh than men and to accumulate more blood than their bodies could use. Menstruation was the necessary monthly release of that surplus — a purge. Health depended on it flowing freely, and illness was what happened when it did not.

The logic runs further than it first appears. If retained blood makes women ill, then the treatment for a great many complaints is to make the blood come out — which is precisely the therapeutic tradition that followed, and one reason bloodletting persisted in Western medicine into the nineteenth century. A theory built on the idea that the female body accumulates dangerous excess produced two thousand years of interventions aimed at draining it.

Aristotle: the blood as raw material

Aristotle gave the blood a different job. In his account of generation, the male contributed form and the female contributed matter — and the matter was menstrual blood, which semen shaped into an embryo. It was, in his framing, an incomplete version of semen, produced by a body he considered colder and less able to concoct it fully.

Two things followed from that, and both outlasted him by millennia. The blood was understood as generative rather than waste, which is closer to correct than the purge model. And the woman was cast as the passive ingredient in reproduction, which is not.

Galen and the humours

Galen synthesised the Greek inheritance into the humoral system that dominated European medicine until the Renaissance and lingered long after. Women were cold and moist, men hot and dry; menstruation was the body correcting a plethora it could not otherwise burn off. The framework was coherent, teachable, and wrong in almost every particular — and its coherence is exactly why it survived so long.

Pliny and the turn to poison

Then, in the first century, the register changes. Pliny the Elder's Natural History catalogues what contact with menstrual blood was believed to do: sour new wine, blight crops, kill grafts, dry seeds, bring fruit off the trees, dim mirrors, blunt the edge of steel, dull ivory, kill bees, rust bronze and iron, and drive dogs mad.

This is a different claim from the Hippocratic one. The purge model said menstruation was necessary. Pliny's said it was dangerous — not to the woman, but to everyone and everything around her. That is the sentence with the longest afterlife in this entire history. It is still being restated, in scientific dress, in the 1920s. You will meet it again below.