About the same time flourished _Probus_, who is said to have been a presbyter of Antioch, and produced commentaries upon Porphyry’s _Isagoge_, and on Aristotle’s _Hermeneutica_, _Soph. Elench._, and _Analytica Priora_, these commentaries becoming favourite manuals amongst the Syriac speaking students of logic. Hoffman’s _De Hermeneuticis apud Syros_ (Leipzic, 1873) gives the text of the commentary on the _Hermeneutica_ followed by a Latin translation. The method employed here and in all Syriac commentaries is to take a short passage, often no more than a few words, of the Text of Aristotle translated into Syriac and then give an explanation of the meaning sometimes extending to several pages, sometimes only a brief remark, according to the difficulty of the text, very much as if a teacher were reading aloud and explaining passages by passage as he read. This became the usual method of commenting and was afterwards copied by the Muslims in their commentaries on the Qur´an. The commentary on the _Isagoge_ has been published by Baumstark (_Aristotles bei den Syrern_, Leipzic, 1900), and that on the _Analytica Priora_ by the great Louvain scholar Prof. Hoonacker in the _Journal Asiatique_ for July-August, 1900. The greatest of the Monophysite scholars was _Sergius_ of Ras al-`Ayn (d. 536), who was both a translator and the author of original treatises on philosophy, medicine, and astronomy. His medical work was his chief interest and he left a permanent mark as a translator into Syriac of a considerable part of Galen. He spent some time in Alexandria where he perfected himself in a knowledge of Greek and learned chemistry and medicine in the Alexandrian medical school then just beginning its career. Some of his translation of Galen is preserved in the British Mus. MSS. Addit. 14661 and 17156: in the latter are fragments of the “Medical art” and “Faculties of the aliments” which have been edited by Sachau (Inedita Syriaca, Vienna, 1870). Of his philosophical work Sachau has given us the versions which he made of the _Isagoge_ and _Table_ of Porphyry, and Aristotle’s _Categories_ and the dubious _de mundo_, as well as a treatise on “the soul” which is not the _de anima_ of Aristotle. He wrote original treatises on logic in seven books (incomplete--Brit. Mus. Add. 14660 contains that on the categories), on “negation and affirmation,” on “genus, species, and individual,” on “the causes of the universe according to Aristotle” and minor essays. In astronomy he has left a tract “on the influence of the moon” which is based on the work of Galen (cf. Sachau, op. cit.) The writings of Sergius circulated amongst both Nestorians and Monophysites, all regarding him as a leading authority on medicine and logic, and in medicine it seems that he was the founder of a Syriac school which became the parent of Arabic medicine, certainly that school owed its impetus to him. Bar Hebraeus refers to him as “a man eloquent and greatly skilled in the books of