Abu Bakr Muhammad Ibn Zakareya Al Razi (c. 865-923/932 C.E.)Known in Latin as Rhazes or Rasis.
Famous Persian Muslim physician, philosopher, and alchemist. He was chief physician at the Baghdad hospital. An observant clinician, he formulated the first known description of smallpox as distinguished from measles, and wrote a treatise on the subject. His works were widely circulated in Arabic, and translated to Latin in Europe. They include a textbook of medicine called Almansor and an encyclopedia of medicine compiled posthumously from his papers.
Amazingly, his treatise on measles and smallpox was published in Arabic and Latin in London 1766, as "Ar-Razi, Muhammad Ibn-Zakariya: Rhazes De Variolis Et Morbilis / cura et impensis Iohannis Channing. - Londini : Bowyer, 1766. - XVI, 276 S."