His full name was Ala al-Din Abu al-Hassan Ali Ibn Abi-Hazm al-Qarshi al-Dimashqi, and so not surprisingly he is commonly referred to as Ibn al-Nafis [13–15]. He was born in Damascus (or very nearby) in 1213 and had his medical education there at the Medical College Hospital (Bimaristan al-Noori). At the age of 23 he moved to Cairo where he first worked at the Al-Nassri Hospital, and subsequently at the Al-Mansouri Hospital, where he became physician-in-chief. When he was only 29 he published his most important work, the Commentary on Anatomy in Avicenna’s Canon which included his ground-breaking views on the pulmonary circulation and heart that are referred to below [1–6, 8]. He also worked on an enormous textbook, The Comprehensive Book of Medicine. This was never completed but was the largest medical encyclopedia to be attempted at the time and is still consulted by scholars.

Ibn al-Nafis was an orthodox Sunni Muslim and, as mentioned above, wrote extensively in areas outside of medicine including law, theology, philosophy, sociology, and astronomy. He also authored one of the first Arabic novels translated as Theologus Autodidactus. This is a science fiction story about a child brought up on an isolated desert island who eventually comes in contact with the outside world.

The teachings of the Galenical school about the pulmonary circulation were discussed at length in Chap. 1 and depicted there in Fig. 1.​3. A feature was that some of the blood in the right ventricle passed into the left ventricle through “invisible pores” in the interventricular septum. The existence of these so-called pores was a puzzle to some anatomists but they were a necessary feature of the Galen scheme because it was not appreciated that a large amount of blood flowed from the lungs to the heart.

In his Commentary on Anatomy in Avicenna’s Canon, Ibn al-Nafis made three important advances with respect to Galen’s scheme:

but there is no passage between these two cavities [right and left ventricles]; for the substance of the heart is solid in this region and has neither a visible passage, as was thought by some persons, nor an invisible one which could have permitted the transmission of blood, as was alleged by Galen. The pores of the heart there are closed and its substance is thick.

This forceful denial of the permeability of the interventricular septum is also repeated elsewhere in the commentary. For example, in the section identified as fol 65 r and v, Meyerhof’s translation is as follows:

There is no passage at all between these two ventricles; if there were the blood would penetrate to the place of the spirit [left ventricle] and spoil its substance. Anatomy refutes the contentions [of former authors]; on the contrary, the septum between the two ventricles is of thicker substance than other parts in order to prevent the passage of blood or spirits which might be harmful. Therefore the contention of some persons to say that this place is porous, is erroneous; it is based on the preconceived idea that the blood from the right ventricle had to pass through this porosity–and they are wrong!