For as long as surgeons cut open living people to keep them alive, they have needed dead people to practice on. Today, donation programs keep medical schools supplied with the bodies they need to teach their students. But in 1820s Scotland, donating your body to science wasn’t legal yet. Nonetheless, one doctor found a way to get the bodies he needed. But it came at a terrible cost. This is the grisly story of the Anatomy Murders.

John Knox’s 400-body problem

In the early 1800s, surgery was booming. A few decades earlier, Scottish surgeon John Hunter had helped bring a scientific view to Western medicine , transforming surgery with experimentation and careful observation. The Napoleonic Wars had boosted the demand for trained surgeons, Alun Evans , a retired epidemiologist at Queen’s University in Belfast, tells Popular Science.

One of the leading lights in this burgeoning field was Hunter’s compatriot Robert Knox, who ran an anatomy school in Edinburgh.…