When the problem of the resistance to the passage of electricity in a conductor was to be studied, another nation supplied the man for the opportunity. Ohm had never been in contact with any of these great contemporaries and did his work entirely by himself. It is a curious confirmation of what we have stated with regard to the young man in {20} medicine and the making of great discoveries that practically all these founders in electricity were under thirty-five when their best original work was accomplished. From a series of biographies of great medical discoverers, certain salient traits stand out so as to attract attention even from the cursory reader. The essence of significant work in medicine consists of observation, not theory. It has always been the custom to theorize much and unfortunately to observe but little. Long ago John Ruskin said that the hardest thing in the world for a man to do is to see something and to tell it simply as he saw it. Certainly this has been true in medicine. The men who have had eyes, and have used them, have impressed their names upon the history of progressive scientific advance. The theorists have never contributed anything worth while to the body of medical truth. While this is readily acknowledged by every generation, with regard to the past, it is curious to note how different is the appreciation of each generation for the theorist as opposed to the observer. Medical theorists have always been honored by their contemporaries unless their theories were utterly outlandish, and even then they have had many disciples, and have seldom been without honor and never, with sorrow for the foolishness of men be it said, without emolument. The observer, however, has but rarely been in favor with his contemporaries. Not infrequently the observation that he made appeared to be so obvious that his fellows could not think that it represented a great truth. As a consequence they have usually derided him for attempting to make them see a significance in his observation that they could not think was there. Huxley once stated the phases through which a new scientific truth ordinarily passes. At first it is said to be trivial and insignificant, then as it attracts more attention {21} it is declared to be in contradiction with hitherto known truth. Finally it is declared to be after all only in other terms what the world has always believed in the matter. Certainly through these stages all the great discoveries in medicine have gone. So true is this, that if what seems to be a new truth in medicine is accepted at once, and willingly, there is more than a suspicion that it is not really a new discovery but only a modification of something hitherto well known.