_Erasistratus_ studied under Chrysippos (or Chrysippus), and under Metrodorus, the son-in-law of Aristotle. Herophilus had been a student at Cos, Erasistratus at Cnidos, so that the teaching of the two great Greek medical schools was introduced into Alexandria. Xenophon, of Cos, one of the followers of Erasistratus, first resorted to the ligation of vessels for the arrest of hæmorrhage, although for many years in later times this important practice was lost through the neglect of the study of the history of medicine. Erasistratus and Herophilus, it is sad to relate, considered that vivisection of human beings, as well as dissection of the dead, was a necessary part of medical education, and believed that the sufferings of a few criminals did not weigh against the benefit likely to accrue to innocent people, who could be relieved or cured of disease and suffering as the result of the knowledge gained by dissection of the living. This cruel and nefarious practice was followed "so that the investigators could study the particular organs during life in regard to position, colour, form, size, disposition, hardness, softness, smoothness, and superficial extent, their projection and curvatures." The followers of these teachers, unfortunately, became very speculative and fond of discussions of a fruitless kind, and, according to Pliny, it was easier "to sit and listen quietly in the schools than to be up and wandering over the deserts, and to seek out new plants every day,"[9] and so, in the third century before Christ, the school of _Empiricism_ was established, the system of which resembled the older Scepticism. It rested upon the "Empiric tripod," namely, accident, history and analogy. This meant that discoveries were made by accident, knowledge was accumulated by the recollection of previous cases, and treatment adopted which had been found suitable in similar circumstances. _Philinus of Cos_, a pupil of Herophilus, declared that all the anatomy he had learned from his master did not help him in the least to cure diseases. Philinus, according to Galen, founded the Empirici, the first schismatic sect in medicine. Celsus[10] wrote of this sect that they admit that evident causes are necessary, but deprecate inquiry into them because Nature is incomprehensible. This is proved because the philosophers and physicians who have spent so much labour in trying to search out these occult causes cannot agree amongst themselves. If reasoning could make physicians, the philosophers should be most successful practitioners, as they have such abundance of words. If the causes of diseases were the same in all places, the same remedies ought to be used everywhere. Relief from sickness is to be sought from things certain and tried, that is from experience, which guides us in all other arts. Husbandmen and pilots do not reason about their business, but they practise it. Disquisitions can have no connection with medicine, because physicians