hundreds of years ago; and it was revived early in our century. But scientific bacteriology is of quite recent creation. It dates from the end of the fifties—that is, from Pasteur's researches into the fermentation of beer and wine and Virchow's investigations into cellular pathology. Progress has been very rapid since. We have now numerous works, large and small, devoted entirely to the description and study of the life-history of the microscopic organisms which occasion disease; and every year brings the discovery of some new micro-organism to which some disease, or group of diseases, may be attributed. Cholera, typhoid fever, gastric affections altogether, malaria, and influenza; tuberculosis, leprosy, and cancer; diphtheria, measles, and scarlet fever; rheumatism, anthrax, small-pox, rabies, and tetanus; nay, even the poison of the cobra snake, have been traced to separate microscopical beings. The photograph of each separate bacillus or micrococcus may be found in the text-books; its manners of life, and very often its modes of reproduction, have been carefully studied, both in the animal body and in artificial cultures; so also its morbid effects when introduced into the bodies of various animals. True that the general reader is often amazed on learning that such and such a microbe which was introduced a few months ago, as the real cause of influenza or of some other disease, is recognized now as a common inhabitant of the human body, and has nothing to do with the said disease; while a few months later the real enemy will again be discovered, but will have no more success than its predecessor. But such ephemeral discoveries are simply indicative of an unhappily general tendency among modern scientists—that of hastening to announce discoveries, and to attach one's name to something new, before the supposed discovery has been submitted to the test of searching experiment. The same tendency prevails in all sciences—the only difference being, that the general reader is seldom gratified by the daily press with the discovery of a new chemical "law," or of a new "type" of fossil mammals, while each discovery which deals with disease, ephemeral or not, enjoys a wide publicity so soon as it has found its way into a scientific periodical. The very rapidity with which the would-be discoveries of new bacilli are reduced to their real value only proves, on the contrary, the safety of the methods used by bacteriology for distinguishing between the seeming and the real causes of disease.
We may thus safely recognize that science already knows a great number of micro-organisms which are capable, under certain circumstances, of producing certain specific diseases; and we
- M. Calmette, in Archives de médecine navale et coloniale, mars, 1892; referred to in Revue Scientifique, 23 avril, 1892.