The Secret Dissections Behind The Mona Lisa

Between roughly 1489 and 1513, Leonardo da Vinci — painter of the Mona Lisa and The Last Supper, the most celebrated artist in European history — conducted a secret second career that would have ruined him if it had been fully exposed.

He dissected human corpses. At least 30 of them. At night. Often alone. In the morgues and hospitals of Florence, Milan and later Rome.

The Horror

The Catholic Church tightly restricted human dissection through much of the medieval and Renaissance periods. Rules differed by region and time; some universities received limited permission to dissect bodies for teaching. But unsanctioned cutting of the dead was widely frowned upon. For an artist with no formal medical degree to be opening bodies in hospital basements was, at best, a scandal and at worst potentially criminal.

Leonardo did it anyway. He needed to understand the machine he was painting.

He began with surface anatomy: muscles, tendons, the structures under the skin that matter for drawing arms, faces and torsos. Then he moved inward. He opened skulls and removed brains. He injected molten wax into brain ventricles to map chambers that collapse when exposed to air. He sliced vertebral columns and drew cross‑sections. He described and illustrated more than 200 individual muscles.

His method was methodical and experimental. He drew the skeleton from multiple angles. He studied the foetus in the womb with a level of anatomical accuracy that wasn’t matched until the age of modern imaging, centuries later. He sketched organs as systems, trying to show how they moved and worked, not just how they looked.

He became obsessed with the heart. He dissected hearts from animals and humans and set up experiments with water to mimic blood flow. He described the function of the aortic valve extremely precisely — including the way eddies form under the valve flaps — a pattern that modern cardiology only fully confirmed with advanced imaging.

He noticed that arteries become thicker and stiffer with age and linked that change to declining warmth and vitality. What we now call atherosclerosis — the progressive hardening and narrowing of arteries — appears in his notes as an observed process. He wrote that old people are colder because their vessels “restrict the passage of blood.” He had essentially described the mechanism of a major cardiovascular disease 400 years before it was named.

In the early 2000s, cardiac surgeons in Britain, including Francis Wells at Papworth Hospital, studied Leonardo’s heart drawings and used them to refine techniques for repairing mitral valves. A 21st‑century heart operation borrowed insight from 16th‑century sketches made by an artist working under candlelight.

Leonardo recorded his findings in notebooks — written in his characteristic mirror script, right‑to‑left. He likely wrote this way because it suited his left‑handedness, but the effect was that casual readers could not easily understand his pages. He never published his anatomical work. The notebooks stayed in bundles and chests. After his death in 1519, they were inherited, dispersed, sold and slowly reassembled across centuries.

The Modern Relic

Around 7,000–7,200 pages of Leonardo’s notebooks survive. His anatomical studies — a few hundred sheets with hundreds of individual drawings — are part of the Royal Collection in Britain, held at Windsor Castle.

These sheets show dissected hands, opened chests, exposed brains, foetuses, spines and hearts — all drawn with the same meticulous line that shaped the Mona Lisa’s smile and the apostles around the Last Supper table. The hand that painted soft sfumato flesh also traced the thin walls of ventricles and the branching of nerves.

One page includes a note about “an old man” who told Leonardo shortly before his death that he was over a hundred years old. Leonardo recorded that the man died peacefully, “without any movement or sign of distress.” Then Leonardo performed an autopsy that night, examining and drawing the inside of a centenarian’s body. He concluded that hardened vessels and failing organs had quietly ended the man’s life.

The unknown hospital dead — unclaimed, unrecorded — became his teachers. He turned their bodies into diagrams that medicine would eventually rediscover and use.

For four hundred years, the drawings stayed in collections, rarely seen and not integrated into mainstream anatomy. They were art curiosities more than textbooks. Only in the modern era did medicine look back and realise how much he had already seen.

The painter became an anatomist in secret. The anatomist became a diagnostician ahead of his time. The notebooks went into drawers. When surgeons finally opened them, they found hearts and vessels drawn so clearly that they changed how living hearts were repaired.

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