Ptolemy gathered to the museum at Alexandria a number of very learned men, who lived within its walls and were provided with salaries, the whole system closely resembling a university. Grammar, prosody, mythology, astronomy and philosophy were studied, and great attention was given to the study of medicine. Euclid was the teacher of Mathematics, and Hipparchus of Alexandria was the father of Astronomy. The teaching of medicine and of astronomy was for long based upon observation of ascertained facts. The Alexandrian School endured for close upon a thousand years, and its history may be divided into two periods, namely, from 323 to 30 B.C., during the period of the Ptolemies, and from 30 B.C. to 640 A.D. The second period was distinguished for the study of speculative philosophy, and of the religious philosophy of the Gnostics, and was not a scientific period. Julius Cæsar was not the only Roman Emperor who brought trouble upon the Alexandrian School, for the brutal Caracalla took away the salaries and privileges from the _savants_, and prohibited scientific exhibitions and discussions. In recent excavations in the Baths of Caracalla in Rome, the ruins of a library have been discovered, and it is believed by some archæologists that Caracalla supplied this library with books and parchments from Alexandria. The Asclepiadæ of Cos and Cnidos had discoursed upon the phenomena of disease, without attempting to demonstrate its structural relations; like the sculptors of their own age, they studied the changing expression of vital action almost wholly from an external point of view. They meddled not with the dead, for, by their own laws, no one was allowed to die within the temple. But the early Alexandrians were subject to no such restrictions; and turning to good account the discoveries of Aristotle in natural history and comparative anatomy, they undertook for the first time to describe the organization of the human frame from actual dissections.[7] Thus there was inaugurated at Alexandria the Anatomic Period of Medicine, which lasted till Egypt came under the sway of the Romans. Medical practice became so flourishing at Alexandria that three great specialities were established, namely, Surgery, Pharmacy, and Dietetics, and a great variety of operations were performed. Lithotomy was much practised by specialists. A foul murder was perpetrated by lithotomists at the instigation of Diodotus, the guardian of Antiochus, son of Alexander, King of Syria (150 B.C.), young Antiochus, at the age of 10, being done to death under the pretence that he had a stone in his bladder.