Ibn al-Nafis

Ibn al-Nafis was an Arab physician and polymath of the Islamic Golden Age who worked chiefly in Damascus and Cairo, where he served as chief physician at major hospitals. He is best known for describing pulmonary circulation, the path blood takes from the heart through the lungs and back, roughly 350 years before William Harvey's work on the circulatory system reached Western medicine. In doing so he directly challenged the long-standing Galenic account of invisible pores in the heart's septum, and he also made early observations toward what would later be understood as capillary circulation.