In 1924, Egyptian
physician, Muhyo Al-Deen Altawi, discovered a manuscript entitled,
Sharh tashrih al-qanun li’ Ibn Sina, or "
Commentary on Anatomy in Avicenna's Canon" in the
Prussian State Library in
Berlin while studying the history of Arabic Medicine at the medical faculty of Albert Ludwig's University. This manuscript covers in detail the topics of
anatomy,
pathology, and
physiology. This is the earliest description of
pulmonary circulation.
Pulmonary circulation The most commonly accepted theory of cardiac function prior to Ibn al-Nafis was that of
Galen. Galen taught that the blood reaching the right side of the
heart went through invisible pores in the cardiac septum, to the left side of the heart, where it mixed with air to create spirit, and was then distributed to the body. According to Galen, the
venous system was separate from the
arterial system except when they came in contact through the unseen pores. The newly discovered manuscript of Ibn al-Nafis was translated by Max Meyerhof. It included critiques of Galen's theory, including a discussion on the pores of the heart. Based on animal
dissection, Galen hypothesized
porosity in the
septum in order for blood to travel within the heart as well as additional help on the part of the
lungs. However, he could not observe these pores and so thought they were too small to see. “Ibn al-Nafīs's critiques were the result of two processes: an intensive theoretical study of medicine, physics, and theology in order to fully understand the nature of the living body and its soul; and an attempt to verify physiological claims through observation, including dissection of animals.” Ibn al-Nafis rejected Galen's theory in the following passage: The blood, after it has been refined in the right cavity, must be transmitted to the left cavity where the (vital) spirit is generated. But there is no passage between these cavities, 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. He posited that the "pores" of the heart are closed, that there is no passage between the two chambers, and the substance of the heart is thick. Instead, Ibn al-Nafis hypothesized that blood rose into the lungs via the arterial vein and then circulated into the left cavity of the heart. Elsewhere in this work, he said: The heart has only two ventricles...and between these two there is absolutely no opening. Also dissection gives this lie to what they said, as the septum between these two cavities is much thicker than elsewhere. The benefit of this blood (that is in the right cavity) is to go up to the lungs, mix with what air is in the lungs, then pass through the arteria venosa to the left cavity of the two cavities of the heart; and of that mixture is created the animal spirit.
Coronary circulation Ibn al-Nafis also postulated that nutrients for heart are extracted from the
coronary arteries: Again his [Avicenna's] statement that the blood that is in the right side is to nourish the heart is not true at all, for the nourishment to the heart is from the blood that goes through the vessels that permeate the body of the heart.
Capillary circulation Ibn al-Nafis had an insight into what would become a larger theory of the capillary circulation. He stated that "there must be small communications or pores (manafidh in Arabic) between the pulmonary artery and vein," a prediction that preceded the discovery of the capillary system by more than 400 years. Ibn al-Nafis' theory, however, was confined to blood transit in the lungs and did not extend to the entire body: For this reason the arterious vein has solid substance with two layers, in order to make more refined that (the blood) which transsudes from it. The venous artery, on the other hand, has thin substance in order to facilitate the reception of the transsuded [blood] from the vein in question. And for the same reason there exists perceptible passages (or pores) between the two [blood vessels].
Pulsation Ibn al-Nafis also disagreed with Galen's theory that the heart's pulse is created by the arteries’ tunics. He believed that "the pulse was a direct result of the heartbeat, even observing that the arteries contracted and expanded at different times depending upon their distance from the heart. He also correctly observed that the arteries contract when the heart expands and expand when the heart contracts. == Other medical contributions ==