Commentary on Anatomy in Avicenna's Canon

The Commentary on Anatomy in Avicenna's Canon is a work written in the 13th century by the Arab physician Ibn al-Nafis. A manuscript of the work was discovered in 1924 in the archives of the Prussian State Library in Berlin, Germany. It contains the earliest descriptions of the coronary circulation and pulmonary circulation systems. The manuscript records Ibn Nafis' prediction of the existence of the capillaries which he described as perceptible passages (manafidh) between pulmonary artery and pulmonary vein. These passages would later be identified by Marcello Malpighi as capillaries.