Medieval Muslims revolutionized the science and practice of medicine, as physicians began to question the medical traditions inherited from both East and West and distinguish one disease from another. For example, Ibn al-Haytham (ca. 965-1039), the so-called "father of optics," explained how human vision takes place by integrating physical, mathematical, experimental, physiological, and psychological considerations. His treatise had an enormous impact on all later writers on optics, both in the Muslim world and through a medieval Latin translation in the West. Similarly, the great Egyptian physician Ibn al-Nafis (d. 1288), discovered the minor, or pulmonary, circulation of the blood. Ibn Sina (980-1037), known in the West as Avicenna, synthesized Aristotelian and later Greek theories with his own original views, and his Canon of Medicine became the most famous medical book in the East or West, translated at least 87 times.
Muslims also expanded the practice of medical schools and hospitals. The Abbasid caliph Harun al-Rashid used the Sasanian academy of Jundishapur in southwestern Iran as his model when he founded his own hospital in Baghdad (ca. 800). Hospitals were soon established throughout the empire. They were staffed by dozens of specialists, from physiologists, oculists, and surgeons, to bonesetters. They even had special wards for the mentally ill and separate wings for men and women. These hospitals were often incorporated into large charitable foundations and were supported by endowments made by powerful and wealthy individuals. One of the most famous was that founded by the Mamluk sultan Qalawun in Cairo. In addition, traveling clinics and dispensaries provided services to rural areas.