Now, I have great faith that science will eventually solve these problems, but had little expectation that my feeble efforts for three months in Havana, would do more than to clear away some of the difficulties and make the solution easier for future investigators. I therefore had no hesitation in undertaking to do my best to fulfil the expectations of the National Board, without troubling myself as to whether a failure to find the germ would be considered a serious neglect of duty by the expectant public, or would be seized upon as a proof that there is no germ, by the wise men who, having, without any investigation at all, pronounced positively against its existence, are naturally anxious to have a chance to say, "I told you so." The truth is that we are yet a long way from settling this question. But I think I may safely say as the result of my investigations in Havana, that there is no gross and conspicuous germ or organism, either in the blood of yellow fever patients or in the air of infected localities, which, by its peculiar appearance or abundant presence, might arrest the attention of a microscopist and cause suspicion that it is the veritable germ of yellow fever. By gross and conspicuous germ, I mean an organism, the morphological peculiarities of which are readily made out with a first class modern objective, such as the Zeiss 1-18, which I used in Havana. The Bacillus anthracis of splenic fever; the Spirillum Obermeieri of relapsing fever; and the bacillus of pig typhoid, or infectious pneumo-enteritis, all come under this head. Yellow fever, so far as the germ theory is concerned, may therefore be classed with cholera, typhoid fever and the malarial fevers, which, by a process of reasoning, similar to that commonly used for yellow fever, are very generally believed to be germ diseases, but in which no organism has yet been demonstrated. It is true that the recent investigations of Klebs and Tomassi, in the vicinity of Rome, have resulted in the discovery of what they believe to be the veritable germ of malarial fever; but these observations require verification, and I may say here that I am instructed by the National Board to repeat their experiments, and to seek their Bacillus malaria in the vicinity of the swamps about New Orleans. I have already made some preliminary observations in this direction, but thus far without any positive results. Both for yellow fever and for the malarial fevers, the microscopic examination of infected atmospheres would seem to offer the best promise of success in the discovery of the organism, if there is an organism, which causes these diseases. We may suppose that in non-contagious diseases this organism is itself destroyed in producing its noxious effects and does not multiply in the human body; or that it exists in the blood or other fluids, in such small numbers as to escape attention, or that it accumulates in certain undiscovered foci, in the tissues; or that it is too minute to be discovered by the highest powers of the microscope. All of these hypotheses must be disproved before the germ theory, which, at present, so far as these diseases are concerned, is based upon a deductive process of reasoning and not upon direct experimental proof, can be supposed to have fallen before the attacks of science. On the other hand, in the efforts of science to discover the hypothetical germs of these diseases, it would seem that a study of infected atmospheres should give the best results; as we have here, beyond doubt, an abundance of these subtle poisons, which as yet are known to us only by their effects. The particulate nature of these poisons which is predicated, especially for yellow fever, upon various facts relating to portability, preservation in goods, clothing, etc., makes it seem especially the province of the microscopist to seek for them. It is to be hoped, however, that the resources of chemistry will also be brought to bear upon the problem. As already stated, a pretty thorough search in Havana has failed to disclose any organism peculiar to infected atmospheres, which may be supposed to be the germ of yellow fever. But the difficulties of such an investigation, the brief stay of the Commission in Cuba, the innumerable harmless organisms which abound everywhere in the atmosphere and which must be excluded, one by one, by the novice in this field of inquiry, and, finally, the imperfection of our optical apparatus, all combine to make this negative result of little value, and it is only after a protracted search by specially trained experts that a negative result can be supposed to carry any great weight. Even then, we shall only have disproved the presence of a germ visible with the optical apparatus now available, and the microscope of the future may show our successors that which at present is ultramicroscopic. We have positive evidence of the constant presence of ultra-microscopic germs in the atmosphere in the development of a multitude of microorganisms in organic liquids, exposed for a short time to the air. For these organisms, although quite within reach of our modern objectives, are not found in the atmosphere by the most careful search, except, occasionally in the immediate vicinity of sewers, etc., and, as evidence of spontaneous generation is wanting, we are obliged to assume that they are developed from germs which escape our researches. While I have nothing but negative results to bring before you, so far as the main object of my investigations is concerned, I have been enabled through the liberal policy of the National Board of Health to study and photograph many of the common organisms found in the atmosphere of New Orleans during the absence of any epidemic disease. As I consider a thorough knowledge of these every-day organisms an essential prerequisite to an enlightened study of an infected atmosphere, I have no hesitation in bringing before you the results of my labors. This I can best do by projecting my photo-micrographs for your inspection, and for this purpose will here terminate the written portion of my address. TITLES OF OTHER PAPERS READ IN THE PERMANENT SUBSECTION OF MICROSCOPY. . CONTRIBUTION TO THE HISTOLOGICAL NATURE OF THE MEMBRANE IN CROUP. By Ephraim Cutter, of Boston, Mass. ABUNDANCE OF MICROSCOPIC FORMS OF LIFE IN THE CENTRAL AND LATERAL SURFACES OF LAKES AND PONDS. of Boston, Mass. By Ephraim Cutter, ON THE LIMITS OF VISIBILITY WITH THE MICROSCOPE. Dolbear, of College Hill, Mass. By A. E. A NEW FREEZING MICROTOME. By Wm. Hailes, of Albany, N. Y. A METHOD OF MOUNTING IN GLYCERINE AND CERTAIN DIFFERENTIATIONS OF STRUCTURE PRODUCED BY IT ON INSECTS. By W. H. Seaman, of Washington, D. C. MINUTE ANATOMY OF THE HUMAN LARYNX.. By Carl Seiler, of Philadelphia, Pa. SOME OF THE INFUSORIA FOUND IN FRESH POND, CAMBRIDGE. By S. P. Sharples, of Boston, Mass. APPARATUS USED IN PHOTOGRAPHING MICROSCOPICAL OBJECTS. By Samuel Wells, of Boston, Mass. |