Abu Bakr Mohammad Ibn Zakariya al-Razi, known in the West as Rhazes, was the leading scholar of the early Islamic world. His stature is comparable only to that of Ibn Sina a century later. Influenced by Hippocrates and classical Greek medicine, Al Razi wrote numerous books on a range of medical and scientific subjects. The Al-Mansuri and Al-Hawi, his encyclopedic reviews of medicine, were translated into several languages and became a standard text for Islamic and European medical students for centuries.
He was a keen experimenter and observer. As director of a large hospital in Baghdadand physician to the royal court, he engaged in medicine on a practical level and these experiences permeate his writings. He saw the importance of recording a patient’s case history and made clinical notes about the progress and symptoms of different illnesses, including his own.
One of his most innovative assertions related to measles and smallpox. Previously they were lumped together simply as a disease that caused rashes, but through careful observation al-Razi recorded the differences in appearance of the skin inflammations as well as the accompanying physical symptoms, and proposed correctly that they were indeed two distinct diseases.