The largest work of Rhazes is _Al-Háwí_, or the _Comprehensive_ book, commonly called “Continens.” In the Latin translation this fills two folio volumes. Although little more than a sort of medical commonplace book, it has a value in that it has preserved for us many fragments from the works of ancient physicians which we should not otherwise have possessed. Another important work of Rhazes is the _Ketábu-l-Mansúri_, or _Liber ad Almansorem_, so called from being dedicated to Mansur, prince of Chorásán. It was intended to instruct the physician in everything which it was necessary for him to know. It is chiefly a compilation, but was a popular text-book in the fifteenth and sixteenth centuries. Rhazes taught the external use of arsenic, mercurial ointments, and sulphate of copper, and the internal use of brandy, nitre, borax, coral, and gems. ALI BEN EL ABBAS (Ali Abbas), who lived in the latter part of the tenth century, was a Persian physician, who wrote a medical text book, entitled the _Royal Book_. Up to the time of Avicenna, this was the standard authority on medicine amongst the Arabs, and was several times translated into Latin. In the theory of medicine and partly in its practice he followed the Greeks, but imitated the use of the excellent materia medica of the Arabs. He wrote also on ophthalmology and obstetrics. AVICENNA, or EBN SINA, was called “the Prince of Physicians,” and was the greatest philosopher produced by the Arabs in the East. He was born in the province of Bokhara, in 980 A.D. It is related that at the age of sixteen he had learned all the science of a physician. Having cured Prince Nouh of a serious malady, he became a court favourite. After travelling for a while he composed his great work, the _Canon of Medicine_, by which his name was made famous both in Asia and Europe for several centuries. In the midst of the troubles of an adventurous life, he wrote a hundred gigantic books, the greatest of which was the _Al-Schefà_. ISHAK BEN SOLEIMAN (830-940) wrote on dietetics, and is said to have been the first to introduce senna. SERAPION THE YOUNGER (about 1070). His work, _De Simplicibus Medicamentis_, was published in Latin at Milan in 1473. MESUE the younger (about 1015) was a pupil of Avicenna, and physician to the court at Cairo. He rendered great services to pharmacy by teaching the method of preparing extracts from medicinal plants.