Discovery of Pulmonary Circulation

by Meam Wye on June 20, 2009

Pulmonary circulation was first correctly described by Ibn Al-Nafis, a 13th century muslim polymath, in his book 'Sharh Tashrih al-Qanun Ibn Sina' (Commentary on Anatomy in Avicenna's Canon) centuries before the English physician William Harvey described the circulation of blood in 1628.

Prior to Ibn Al-Nafis's discovery, the accepted theory was that of Galen (2nd century). According to Galen 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 consequently distributed to the body. According to Galen's views, the venous system was quite separate from the arterial system, except when they came in contact through the unseen pores . However, Ibn Al-Nafis stated 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 substances, be mingled 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 Nafis also stated that:

"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 is in the lungs of air, then pass through the arteria venosa to the left cavity of the two cavities of the heart...”

In describing the anatomy of the lungs, Ibn al-Nafis stated:

"The lungs are composed of parts, one of which is the bronchi; the second, the branches of the arteria venosa; and the third, the branches of the vena arteriosa, all of them connected by loose porous flesh."

He then added:

"... the need of the lungs for the vena arteriosa is to transport to it the blood that has been thinned and warmed in the heart, so that what seeps through the pores of the branches of this vessel into the alveoli of the lungs may mix with what there is of air therein and combine with it, the resultant composite becoming fit to be spirit, when this mixing takes place in the left cavity of the heart. The mixture is carried to the left cavity by the arteria venosa."

In 1924, an Egyptian physician Dr. Muhyo Al-Deen Altawi discovered a manuscript dated 1242 of Ibn Nafis's 'Commentary on Anatomy in Avicenna's Canon)' in the Prussian State Library in Berlin while studying the history of Arab Medicine at the medical faculty of Albert Ludwig's University in Germany. He then discovered that Ibn Nafis was the real discoverer of pulmonay circulation - some 300 years before Servetus,Vesalius or Harvey who was incorrectly credited for the correct explanation of pulmonary circulation. It is interesting to note that in 1547, Andrea Alpago of Belluno translated some of Ibn Al-Nafis’ writings into Latin and a few years later european physicians 're-discovered' this theory.