Amongst the famous products of this school was Paul of Aegina, whose medical works formed the basis of much of the mediæval Arabic and Latin teaching, and the priest Ahrun (Aaron) who composed a manual of medicine which was afterwards translated into Syriac and became a popular authority. Alexandria was the centre also of chemical science, and as such was the parent of later Arabic alchemy. It appears from M. Berthelot’s exhaustive study of Arabic chemistry (_La chimie au moyen age_: Paris, 1893) that the Arabic material may be divided into two classes, the one based upon, and mainly translated from, the Greek writers current in Alexandria, the other representing a later school of independent investigation. Of the former class Berthelot gives three specimens, the Books of Crates, of al-Habid, and of Ostanes, all representing the Greek tradition which flourished at Alexandria on the eve of the Muslim invasion. Whilst the Alexandrians kept alive an interest in medical and the allied sciences the separated branches of the vernacular speaking churches of Asia were more interested in logic and speculative philosophy. It was perhaps natural that the Monophysites with their strong Egyptian connection should adopt the commentaries of John Philoponus, himself a Monophysite of a type, but both they and the Nestorians invariably used Porphyry’s _Isagoge_ as an introductory manual. In the general treatment of metaphysics and psychology as applied to theology, and in the treatment of theology itself, the Monophysites inclined more towards neo-Platonism and mysticism than the Nestorians, and their life centered more in the monasteries, whilst the Nestorians adhered rather to the older system of local schools, although they too had monasteries, and in course of time the schools adopted the discipline and methods of the convent.