Rhazes (c.860-930), Islamic Persian scholar, physician and alchemist, with an assistant, in his chemistry laboratory in Baghdad (now in Iraq). Rhazes is a Latinized form. His full Arabic name is Abu-Bakr Muhammad Ibn Zakariyya Al-Razi. Having known an old apothecary in Baghdad, Rhazes decided to study medicine, and later became the chief physician of the largest hospital in Baghdad. He was the first doctor to differentiate clearly between the two infectious diseases variola (smallpox) and morbilli (measles). Rhazes also prepared what is now called plaster-of-Paris, a preparation of calcium sulphate which he used to form casts to hold broken bones in place. Engraving from the 1883 edition of Vies des Savants Illustres.