For thirteen centuries his name and influence dominated the medical profession in Europe, Asia, and Africa; and this influence, under the name of Galenism, was paramount in the eighteenth century, notwithstanding the discovery of the circulation of the blood and other great advances in science. Galen collected and co-ordinated all the medical knowledge which previous physicians and anatomists had acquired. He was no mere collector of, or compiler of other men’s works; but he enriched previous acquirements by his own observation, and was in every way a man greatly in advance of his time. “A great and profound spirit,” says Daremberg, “he was philosopher as well as physician, realising the aspiration of Hippocrates when he said that the physician who should be also a philosopher must be the equal of the gods. A dialectician like Aristotle, a psychologist like Plato, who glorified his work by his genius for interpreting nature and life, his position as philosopher would have been beside those men, if his devotion to medicine had not called him to another sphere of intellectual activity.” Nevertheless, Galen did in fact occupy an exalted position in the history of philosophy, not only in the West, but amongst the Arabians. His encyclopædic knowledge, his spirit of observation, and his influence on the thought of the middle ages, compel a comparison with Aristotle. It was thus that the vast body of medical material collected by the various sects and schools was analysed by the penetrating genius of Galen, whose philosophical and scientific mind was able to extract the good and permanent from the worthless and ephemeral material, which encumbered the literature of the healing art. He fell under the domination of none of the schools, though in one sense he may be said to have leaned towards the Dogmatists, “for his method was to reduce all his knowledge, as acquired by the observation of facts, to general theoretical principles.”[497] He endeavoured to draw the student of medicine back to Hippocrates, of whom he was an admirer and expounder. The labours of Galen had the effect of destroying the vitality of the old medical sects; they became merged in his system, and left off wrangling amongst themselves to imitate the new master who had arisen. A crowd of new writers found in the works of Galen abundant material for their industry. Partly in consequence of this jealousy, and partly from the fact that in A.D. 167 a pestilence broke out in Rome, he left the city privately, and returned to his native country.