The first great physician of the Arab world was Muhammad ibn Zakariya al-Razi (860-940 A.D.), known as Razi by the Arabs and Rhazes by medieval Europe. Universally considered one of the outstanding authorities in medical history, Razi authored more than two hundred books. His most important work was the Hawi, an extremely detailed medical encyclopedia in twenty-five volumes that was being used by doctors and students not only in the East, but also throughout Europe well into the fifteenth century. Razi best demonstrated his sharp powers of observation in an encyclopedia of therapeutics.
Among his discoveries was the identification of smallpox and measles, both of which he treated successfully. His treatise on smallpox was translated into several European languages over the centuries, the last time in 1948, into English. Razi was the first to use alcohol as an antiseptic and mercury as a purgative. In surgery, he used a fine string made of animal intestine for sewing up wounds.
Perhaps the most renowned of all Arab philosopher-scientists was Abu Ah al-Hussain Ibn Sina (980-1037 A.D.), or Avicenna. An extremely precocious youngster, Ibn Sina did not turn to medicine until he was sixteen, by which time he had already mastered Islamic law, philosophy, natural sciences and mathematics. He was only eighteen when his fame as a physician was such as to induce ruling princes to seek his services. A busy statesman, teacher, lecturer, profound thinker, poet and highly prolific writer on subjects as diverse as geology, music and mathematics, Ibn Sina treated medicine as only one of his numerous occupations.

Nevertheless, he produced sixteen books on medicine, including the Canun, a work of one million words. This encyclopedia, dealing with every then-known disease, treatment and medication as prescribed by both Greek and Arab authorities, is generally regarded as the final codification