In medicine he wrote many books...

In medicine he wrote many books, two of them are "Mujaz Al-Qanun" which means the "Summary of the Canon". In these two books which were based on avicenna's writings, he criticized the short comings of Avicenna's book and of Galen's views and added to them. That is why he was named by some as Avicenna the Second. For example be wrote "... We have relied chiefly on his (Galen) teachings, except in a few details which we think are wrong and were not given after a thorough investigation.

In describing the function of the organs, we have depended on careful investigation, observation, and honest study, regardless of whether or not these fit with the teachings and theories of those who have preceded us." Ibn-El-Nafis added lights to the physiology of the circulation. In the ancient history, Erasistratus of the Alexandria Scbool (310 B.C. - 250 B.C.) believed that blood was contained only in the eight side of the circulation, namely the veins and the fight side of the heart.

The left side of the circulation, namely the left side of the heart and the arteries were supposed to contain air because arteries were found empty when an animal was sacrificed, hence the name "arteria". When Galen came (131 - 210 A.D.), he described blood to pass from the right side of the heart to the left side through minute openings in the septum of the heart, then it mixed with air from the lungs, and sequently distributed to the whole body.

For centuries this was the prevalent belief and no one, including the Arab physicians and their eminent writer Avicenna, could dare to challenge this sacred view. Ibn-El-Nafis did. Five times he stated in unmistakable terms that "... the blood from the right chamber of the heart must arrive at the left chamber, but there is no direct pathway between them. The thick septum of the heart is not perforated and does not have visible pores as some people thought or invisible pores as Galen thought.

The blood from the right chamber must flow through the vena arteriosa (pulmonary artery) to the lungs, spread through its substance, he mingled with air, pass through the arteria venosa (Pulmonary vein) to reach the left chamber of the heart... " (Salem 1968). In describing the anatomy of the lung Ibn-El-Nafis stated: "The lung is composed of.

first, the bronchi: second, the branches of the arteria a venosa; and third, the branches of the vena arteriosa; all of these are connected by loose porous flesh ...