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Our knowledge of the causes of disease has unquestionably been greatly enlarged by the bacteriologic investigations of the past fifteen or twenty years, and we are constantly acquiring new information that is of the highest theoretical and practical importance. With the positive data, however, thus gained, there are others the signification of which is a puzzling problem, and that sometimes appear to contradict or overthrow the conclusions deduced from what have appeared to be well established pathologic acquisitions. Thus we find that even the more virulent pathogenic microbes do not always behave in the same way and there still remains a certain degree of indefiniteness in our knowledge of the behavior of any germ disease analogous to if not quite as extensive as that which formerly existed when bacteria were unknown and the causes of contagious and infectious diseases were yet an unsolved mystery. The natural history of these lowest
SOME PUZZLING FACTS OF IMMUNITY.. JAMA. 1898;XXX(11):619-620. doi:10.1001/jama.1898.02440630045007