Ibn al-Nafis and Pulmonary Circulation, 1242 – Trust honest research, even when it contradicts predecessors

The first person known to have correctly described pulmonary (lung) circulation was the Muslim physician Ibn al-Nafis, born near Damascus, Syria, who worked in Cairo, Egypt. Pulmonary circulation refers to the path of blood between the heart and lungs. Specifically, oxygen-depleted blood leaves the heart by passing from the right ventricle (lower chamber) into the pulmonary arteries leading to the lungs. After being oxygenated by the lungs, blood passes through the pulmonary veins back to the heart’s left atrium (upper chamber), then moves into the left ventricle before being pumped to the carotid artery and the rest of the body.

Ibn al-Nafis was determined not to rely on the established ideas of earlier physicians. In his 1242 treatise, his "Commentary on Anatomy" in Avicenna’s Canon, he wrote: "In determining the use of each organ, we shall necessarily rely on verified examinations and honest research, disregarding whether our views agree with those of our predecessors." For example, he rejected the prevailing views of the Greek physician Galen and the Persian physician Avicenna, both of whom believed blood passed from one side of the heart to the other through invisible pores in the heart wall. Ibn al-Nafis knew there were no pores. Instead, he wrote: "Blood from the right ventricle must flow through the vena arteriosa (pulmonary artery) to the lungs, separate from its substances, mix there with air, pass through the arteria venosa (pulmonary vein) to reach the left chamber of the heart, and there form the vital spirit." Ibn al-Nafis developed his radical observation at the age of 29, and it was not dramatically surpassed around 1628 when English physician William Harvey published his complete theory of the continuous circulation of blood throughout the body.

Ibn al-Nafis also wrote 300 volumes of notes for The Comprehensive Book on Medicine, an 80-volume medical encyclopedia discussing surgery and other medical techniques.

Description of the article image: Ibn al-Nafis described the pulmonary circulation of blood between the heart and lungs. In the image, the pulmonary arteries and veins at the top of the heart branch horizontally to the left and right toward the lungs.

Historical figures mentioned in the article: Abu ‘Ali al-Husayn ibn ‘Abd-Allah Ibn Sina (Avicenna) (980– 1037), Ala al-Din Abu al-Hassan Ali ibn Abi-Hazm al-Qurashi al- Dimashqi (known as Ibn al-Nafis; 1213–1288), William Harvey (1578–1657)

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