Reinier (also sometimes spelled Regnier) de Graaf (1641-1673) was a Dutch physician who made important discoveries studying the pancreas and mammalian reproductive organs, the most important of which was the discovery of the egg…more or less.

De Graaf studied medicine at the University of Angers in France, graduating in 1665. He returned to the Netherlands, settling in Delft in 1667, where he established a medical practice and would spend the rest of his life.

In 1672, he was using a primitive microscope to study ovaries. Incidentally, de Graaf was the first to call them ovaries. He discovered what he thought were eggs, but what he was actually looking at were the protective sacs of fluid in the wall of the ovary where the eggs grow, which would be later called graafian follicles.

Regardless of what he actually saw, it transformed current theories of reproduction. Previously, it was thought that menstrual fluid formed the fetus – instant baby, just add semen! Now, de Graaf’s theory that the eggs traveled down the fallopian tubes to the womb challenged the prevailing view. But the male medical establishment refused to believe that women contributed to the organizational formation of the baby, and asserted that the egg merely contained and nurtured the sperm. Soon enough though, theories were proposed that gave the egg all the credit. It would be another century before Lazzaro Spallanzani put one and one together.

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