Rhazes (c.860-930), Islamic Persian scholar, physician and alchemist examining a boy. Rhazes is a Latinized form. His full Arabic name is Abu-Bakr Muhammad Ibn Zakariyya Al-Razi. Rhazes 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 (using calcium sulphate), which he used to form casts to hold broken bones in place. Engraving by Laplante after a work by Belgian painter Jan Verhas (1834-1896).