Erasistratus was the first who thought that a knowledge of anatomy should be made a part of the healing art. Before his time surgery and medicine had been deemed one and the same; they had both been studied by the slow and uncertain steps of experience, unguided by theory. Many a man who had been ill, whether through disease or wound, and had regained his health, thought it his duty to Esculapius and to his neighbours to write up in the temple of the god the nature of his ailings, and the simples to which he fancied that he owed his cure. By copying these loose but well-meant inscriptions of medical cases, Hippocrates had, a century earlier, laid the foundations of the science; but nothing further was added to it till Erasistratus, setting at nought the prejudices in which he was born, began dissecting the human body in the schools of Alexandria. There the mixing together of Greeks and Egyptians had weakened those religious feelings of respect for the dead which are usually shocked by anatomy; and this study flourished from the low tone of the morality as much as from the encouragement which good sense should grant to every search for knowledge. Herophilus lived about the same time with Erasistratus, and was, like him, famous for his knowledge of the anatomy of man. But so hateful was this study in the eyes of many, that these anatomists were charged by writers who ought to have known better, with the cruelty of cutting men open when alive. They had few followers in the hated use of the dissecting-knife. It was from their writings that Galen borrowed the anatomical parts of his work; and thus it was to the dissections of these two great men, helped indeed by opening the bodies of animals, that the world owed almost the whole of its knowledge of the anatomy of man, till the fifteenth century, when surgeons were again bold enough to face the outcry of the mob, and to study the human body with the knife. Hegesias of Cyrene was an early lecturer on philosophy at Alexandria. His short and broken sentences are laughed at by Cicero, yet he was so much listened to, when lecturing against the fear of death, and showing that in quitting life we leave behind us more pains than pleasures, that he was stopped by Ptolemy Soter through fear of his causing self-murder among his hearers. He then wrote a book upon the same subject, for though the state watched over the public teaching, it took no notice of books; writing had not yet become the mightiest power on earth. The miseries, however, of this world, which he so eloquently and feelingly described in his lectures and writings, did not drive him to put an end to his own life. Philostephanus of Cyrene, the friend of Callimachus, was a naturalist who wrote upon fishes, and is the first investigator that we hear of who thought it desirable to limit his studies to one branch of the science of natural history.