It has been held that the idea of a universal medicine had its origin with Geber. But this may be due to a misreading of his words, which in reality may have reference to the transmutation of metals. He tells of a medicine which cures all lepers. But this may be nothing but allegory. By _man_ is probably meant gold, and by _lepers_ the other metals; and the medicine is the universal solvent or agent which transmutes. Alchemistic literature is full of allegories of this character. Berthelot has shown that in reality there were two Gebers—one who is generally considered to be of Arab origin, and another whose identity is not established, but who was probably a Western European who appears to have lived about the year 1300.[1] [1] There is very little doubt that the work of “Phileletha,” which professed to be taken from an “Uhralten MS.” preserved in the Vatican Library, entitled _Geberi des Königes der Araber_, and published by Hieron. Philipp. Nitschel, Frankfurth and Leipzig, in 1710, is spurious. Other notable names in the history of Arabian alchemy are =Rhazes=, or =Abû Bakr Mohammed ibn Zakaráyá el-Rázi=, who lived _circa_ 925, and =Avicenna=, or in Arabic =Abû Ali el-Hosein ibn-Abdallah ibn-Sina=, born 980, died 1037. The former, a Persian, practised medicine at Baghdad as a follower of Galen and Hippocrates. The latter, one of the most eminent of Moslem physicians and a voluminous writer, was a native of Bokhara. He is mainly known in the history of science by his _Canon of Medicine_, in which he describes the composition and preparation of remedies. He wrote at least one treatise on alchemy, but others attributed to him are probably apocryphal. Of his _Philosophia Orientalis_, mentioned by Roger Bacon and Averroes, no trace remains. Although it is reasonably certain that the alchemists of the time of Geber and of his successors had a considerable acquaintance with manipulative chemistry, there were so many impudent literary forgeries during the alchemical period that the precise extent of the knowledge possessed by the early chemists must always remain uncertain. A number of the ordinary chemical processes, such as distillation, sublimation, calcination, filtration, appear to have been known to, and to have been commonly practised by, the Arabian chemists; and many saline substances, such as carbonate of soda, pearlash, sal-ammoniac, alum, copperas, borax, silver nitrate, cinnabar, and corrosive sublimate, were prepared by them. They seem to have known of certain of the mineral acids, and were familiar with the solvent properties of _aqua regia_.