glycerine penetrated around the edges so as completely to saturate portions of the wing, the scales at once became transparent and the structure was clearly apparent.

The difficulty still remained to replace the air under the concave portions of the wing with the glycerine, so that it could come to, and completely saturate, every portion of the wing, to the exclusion of all the air. Recourse was now had to heat, and by holding the slide over the lamp till ebullition took place, the glycerine was found to replace the air without any injury to the wing structure, and even in those refractory cases where the glycerine was allowed to boil for a considerable length of time, no injury whatever was done to the wing-membrane.

THE MICROSCOPICAL INVESTIGATIONS OF THE HAVANA YELLOW FEVER COMMISSION. By GEO. M. STERNBERG, of Washington, D. C.

THE purpose of the present paper is to give a general idea of the nature and objects of the investigations in which the writer has been engaged during the past year, under the auspices of the National Board of Health, and, more especially, to bring to notice the results obtained in photographing minute organisms, and to call attention to the great value of this method in conducting similar investigations.

A photographic memorandum of an object which we have seen under the microscope, while it may not be so sharply defined as a drawing, has the advantage of being quickly made, and is an unimpeachable record of what has been seen. A record, it is true, which conveys but little meaning to the untrained eye, just as a dingy painting, by one of the old masters, fails to tell its story to the eye of an untutored savage; but which, nevertheless, is full of meaning and of interest for the skilled microscopist. The photograph also saves great time and labor in the measurement of objects, and makes it easy to compare objects seen at different times and places by different observers. It may also be duplicated indefinitely; and when everything is working well, fifteen or

1 Surg, U. S. A., Secretary of the Commission.

twenty negatives may be made, with the assistance of a skilled photographer, in the time which would be required by an accomplished draughtsman to make a single copy of any one of them. Many of my photographs have been made from extemporaneous preparations, in which a delay of half an hour or less, for the purpose of making drawings and measurements, would have resulted in the destruction of the specimen by drying of the liquid in which it was immersed.

All microscopists in the habit of working with high powers know how many accidents may happen to interesting extemporaneous preparations, by which the object, which has been found after a protracted search, is lost from view before the drawings and measurements desired have been made. This is obviated to a great extent by the promptness with which a photograph may be made, and with low powers we may even take instantaneous views of objects in motion. I do not claim, however, that all is plain and easy sailing and that the art of making photo-micrographs of minute objects can be acquired without effort. On the contrary, there are many difficulties with which to contend, and the chances are that the beginner will make many poor pictures and will have his temper and patience sorely tried before, he attains any considerable degree of success. The labors of my friend, Surg. J. J. Woodward of the Army, have done much towards reducing these difficulties and establishing a satisfactory technique for this art, and I take pleasure in embracing the present opportunity to acknowledge my own indebtedness to him for my first lessons in photo-micrography.

As I intend to project some of these photo-micrographs for your inspection and to make a few remarks upon each, while it is displayed before you on the screen, I will not, at present, dwell upon this portion of my subject, but will proceed briefly to review the objects and results of the microscopical investigations in which I have been engaged.

The Havana Yellow Fever Commission received the following instructions from the National Board of Health.

"First. To ascertain the actual sanitary condition of the principal ports of Cuba from which shipments are made to the United States."

"Second. To increase existing knowledge as to the pathology of yellow fever."

"Third. To obtain as much information as possible with regard to the so-called endemicity of yellow fever in Cuba, and the conditions which may be supposed to determine this endemicity."

"The three points above referred to are believed to be those which will most certainly yield results to scientific investigation; and which, therefore, should receive the special attention of the Commission."

"But, in addition to these, the National Board desires that the Commission shall consider certain problems relating to this disease; problems which may be entirely insoluble, but which nevertheless, are of such importance that an effort should be made. to decide whether the National Board of Health will be justified in undertaking the labor and expense which will probably be required to obtain anything like a complete solution of them, if such solution is at all possible. These problems relate to the nature and natural history of the cause of yellow fever.”

In the division of labor made by the members of the Commission, the duty of conducting the investigations under the first and third of the above headings was assigned to the chairman of the Commission, Dr. S. E. Chaillé; and that of conducting the investigations under the second heading to Dr. J. Guiteras; while my attention was chiefly given to investigations contemplated in the additional instructions:

This, then, was the task set before me to determine the nature of the yellow fever poison; to answer the question which is uppermost in our minds whenever this disease is mentioned, and which has heretofore baffled all research. Is it an emanation from the human body? Is it a gas generated external to the body? Is it a bioplast? Is it a germ?

I might well have hesitated before undertaking this unpromising investigation, if the language of our instructions had implied that the National Board considered this an easy task, and one which they expected would be accomplished during our brief stay in Havana. But you will observe that no such result was anticipated, that the difficulty of the undertaking was fully appreciated; and that the work of the Havana Commission in this direction was looked upon as pioneer work, "to decide whether the National Board will be justified in undertaking the labor and expense which will probably be required to obtain anything like a complete solution of them, if such solution is at all possible."

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.