Ibn al-Nafis

By Kaveh Hosseini

For thirteen centuries, every physician in the world believed Galen on the movement of blood. The great Roman anatomist had taught that blood seeped through invisible pores in the wall between the heart's ventricles, passing from right to left. It was wrong, and no one could prove it wrong — until a Damascus-born scholar in Mamluk Cairo sat down to annotate Avicenna's Canon of Medicine and did what commentators were not supposed to do: he disagreed.

Ala al-Din ibn al-Nafis was born in 1213 near Damascus and trained in its hospitals before moving to Cairo, where he rose to become chief physician of the al-Mansuri hospital — the largest medical institution of the medieval world — and personal physician to the sultan al-Zahir Baybars. He was a formidable polymath, writing on jurisprudence, theology, and logic, but his immortality rests on a single passage in his Sharh Tashrih al-Qanun, the Commentary on the Anatomy of the Canon, written around 1242.

There he stated, plainly and without hedging, that the septum of the heart is solid — there are no pores, visible or invisible. Blood must therefore travel from the right ventricle to the lungs through the pulmonary artery, be refined there, and return to the left ventricle through the pulmonary vein. This is the lesser, or pulmonary, circulation, described with complete accuracy nearly three hundred years before Michael Servetus and Realdo Colombo stumbled toward it in Europe, and four hundred before Harvey mapped the greater circulation. Ibn al-Nafis even grasped that the lungs nourish the blood with air and understood the anatomy of the coronary vessels.

And then — nothing. The discovery slept. His commentary circulated in the Arabic manuscript tradition but never reached Latin Europe, and the credit went to others for centuries. It was only in 1924 that an Egyptian physician, Muhyi al-Din al-Tatawi, found the passage in a Berlin manuscript and published it to a startled world. Ibn al-Nafis died in Cairo in 1288, wealthy and honored, his house and library bequeathed to the hospital he had served. He had corrected Galen in a footnote to Avicenna, and the world took seven hundred years to notice.

Impact on civilization

Ibn al-Nafis broke the longest monopoly in medical history: thirteen centuries of Galenic error about the heart, ended by one man's refusal to repeat what the master said. His description of the pulmonary circulation — blood aerated in the lungs, no pores in the cardiac septum — is the first correct account of any part of the circulatory system, and it made Harvey's later discovery of the full circulation conceivable. The seven-century delay in recognition only sharpens the lesson: the medieval Arabic medical tradition was not a storehouse of Greek wisdom but a living science capable of overthrowing it. Modern cardiology begins, unknowingly, in a Cairo hospital in 1242.