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 from his Greek predecessors. He neither did, nor could, create the whole of physiology afresh, as he created the whole science of logic. This shows the difference between a science that is simple and abstract, being dependent on a few laws of the human mind, and a science which is infinitely complex, being dependent on facts which have only gradually been discovered up to a certain point during the long lapse of centuries, with the aid of instruments which were unknown to the ancients. But Aristotle had distinctly the idea of the advance of physiology and medicine by means of the study of nature. He said, “Physical philosophy leads to medical deductions, the best doctors seek grounds for their art in nature.” Perhaps from this sentence, at all events from the notion contained in it, the word “physician” has come to be appropriated in modern times by the practitioners of medicine.

Unfortunately, Aristotle not unfrequently applied dialectical reasonings to questions of physiology when they were quite inappropriate. Por instance, arguing against Plato’s theory of respiration—namely, that breathing results from the impact upon us of the external atmosphere following upon the disturbance which is caused by the expiration of warm air—he says that this would imply expiration to be the first of the two operations; but they alternate, and expiration is the last, therefore inspiration must be the first! Again, he mentions the opinion of those who said that the senses correspond with the four elements, and that sight is fire, trying to prove it by the fact that if the