Ibn al-Nafis: how a 13th-century Cairo physician traced blood from heart to lungs

Every medical student today learns in the first year that the right side of the heart sends blood to the lungs, where it is refreshed, and that it then returns to the left side of the heart. This is called the lesser circulation, or pulmonary circulation. It now seems so simple that it is hard to believe physicians held a different view for centuries. In the 13th century, Ibn al-Nafis, a physician in Cairo, rejected the old idea and described the correct path of the blood.

From Damascus to Cairo

In 2008, John B. West of the Department of Medicine at the University of California, San Diego, in the United States, wrote a research article on Ibn al-Nafis in the “Journal of Applied Physiology”. According to him, Ibn al-Nafis was born in Damascus, or very close to it, in 1213 and died in 1288. An article in the medical journal “Heart Views” in 2010 gives the year of his birth as 1210 and the place as Qarsh, a town near Damascus.

According to West, Ibn al-Nafis studied medicine at the Bimaristan al-Noori in Damascus. At the age of 23 he moved to Cairo, where he worked first at the al-Nassri Hospital and then at the al-Mansouri Hospital. At al-Mansouri he rose to the post of chief physician. He began writing a huge encyclopedia of medicine, the Comprehensive Book of Medicine. According to West, it was never completed, but it was the largest medical encyclopedia attempted in its time.

The old theory: hidden pores in the wall

In the second century AD, the Greek physician Galen and his school put forward a theory of the heart and blood. West writes that these teachings had held for a thousand years by the time of Ibn al-Nafis. Ibn Sina, whose “Al-Qanun fi al-Tibb” (The Canon of Medicine) was mentioned in the 38th article of this series, had also studied Galen’s writings closely. According to West, in this theory blood passed from the right chamber of the heart to the left through “invisible pores” in the wall that separates the two chambers.

The new route: through the lungs

West writes that at the age of only 29, Ibn al-Nafis wrote his most important book, “Sharh Tashrih al-Qanun”, a commentary on the anatomy section of Ibn Sina’s Canon. In this book he stated plainly that there is no passage between the two chambers of the heart. If blood cannot pass through the wall, how does it reach the left chamber? His answer was: through the lungs.

According to the “Heart Views” article, the sequence described by Ibn al-Nafis is as follows. Blood goes from the right chamber into the vessel now called the pulmonary artery, reaches the lungs from there, and then comes into the left chamber through the pulmonary vein. Today’s medical books give the same route.

Ibn al-Nafis went one step further. According to West, he said there must be small passages or pores between the artery and the vein in the lungs, which were called “manafidh” in Arabic. He could not see these passages with the eye, but he inferred that they existed by reasoning. These fine vessels, now called capillaries, were discovered about 400 years later by Marcello Malpighi. According to the “Heart Views” article, Ibn al-Nafis also wrote that the muscles of the heart are nourished by vessels within the heart itself.

Rediscovered seven hundred years later

The work of Ibn al-Nafis lay in libraries for centuries. According to West, the Egyptian physician Muhyo al-Deen al-Tatawi was writing a doctoral thesis at the University of Freiburg in Germany when he found a manuscript of the book in the Prussian State Library in Berlin. His thesis dates from 1924. It was never published; only five typewritten copies were made.

Fortunately, Max Meyerhof, a physician and scholar of Oriental studies based in Cairo, wrote a commentary to preserve the discovery. He later published German, French and English translations of the relevant sections. In this way the name of Ibn al-Nafis entered the history of medicine worldwide.

In 16th-century Europe, Michael Servetus put forward similar ideas in a book of 1553, and Realdo Colombo did so later. Did the work of Ibn al-Nafis reach them? Historians differ on this. According to West, many historians believe that Servetus was not aware of the work.

The lesson today

The most important thing in the story of Ibn al-Nafis is his method. He did not accept a theory that had held for a thousand years, and was considered authoritative, merely because it was old. He observed that the wall of the heart is solid, and from that observation concluded that the blood must take another route.

Today, when a doctor listens to the heart and lungs with a stethoscope, or a surgeon operates on the heart, he is working from the same map, an important part of which was written in 13th-century Cairo. The complete account of the circulation of blood through the whole body, given by William Harvey, will be the subject of a coming article in this series.