Competent critics who have studied the medical teaching of Avicenna have not been able to discover wherein its merits have justified the high esteem to which it attained. The explanation appears to be that what Avicenna lacked in originality he made up in method. The main body of his “Canon” is a judicious selection from the Greek and Latin physicians, and from Rhazes and other of his Arabic predecessors. He wrote a great deal on drugs and remedies, but it has been found impossible to identify many of the substances of his Materia Medica, as in many cases the names he gives evidently do not apply to those given by Serapion, Rhazes, and other writers. He often prescribed camphor, and alluded to several different kinds; a solution of manna was a favourite medicine with him; he regarded corrosive sublimate as the most deadly of all poisons, but used it externally; iron he had three names for, probably different compounds; he had great faith in gold, silver, and precious stones; it was probably he who introduced the silvering and gilding of pills, but his object was not to make them more pleasant to take, but to add to their medicinal effect. Serapion the younger, and Mesuë the younger, who both lived soon after the time of Avicenna, were principally writers on Materia Medica, from whose works later authors borrowed freely. The subsequent Arab authorities of particular note came from among the Western Saracens. Albucasis of Cordova, Avenzoar of Seville, and Averrhoes of Cordova, who are all believed to have flourished in the twelfth century, were the most celebrated. Albucasis was a great surgeon and describes the operations of his period with wonderful clearness and intelligence. Avenzoar was a physician who interested himself largely in pharmacy. He was reputed to have lived to the age of 135 and to have accumulated experience from his 20th year to the day of his death. Averrhoes knew Avenzoar personally, but was younger. He was a philosopher and somewhat of a freethinker who interested himself in medical matters. We are naturally more concerned with Avenzoar than with the others.