mosquito, changed all the conventional conceptions regarding a larg class of diseases, and has been the stimulus to all of the discoverie that have followed. Moreover, the work of the Reed commission i Cuba added the third important disease to the list of those transmitted by insects as necessary agents. The carefulness of the experimentation was a model for subsequent work. Later, in the control of yellow fever in Cuba by the destruction of the mosquito conveyor, the United States made a most important contribution to the subject. Still more recently the sanitation of the Canal Zone has been an extensive and inspiring object lesson to other nations.

While this work has been going on other phases of the subject have received attention in this country. Dr. L. O. Howard has been the foremost contributor. His work on mosquitoes and the house fly, and numerous papers on the economic losses caused by insects have been a powerful influence in bringing about a realization of the necessity of the study of insects in connection with diseases. The climax of this work is the elaborate monograph of the Culicidae which is about to be issued by the Carnegie Institution. Other entomologists have also added to the available knowledge. Doctor Felt, Doctor Forbes, Professors Doane and Herms of California, Mr. Bishopp, Professor Cooley and Mr. Brues have advanced the subject very materially. Impressive as this list of contributors is, as we shall attempt to show, it does not represent more than a small fraction of the work that is demanded.

THE FUNCTION OF THE ENTOMOLOGIST IN THE INVESTIGATION

OF INSECT-BORNE DISEASES

As this is a rather new subject and our conceptions in some respects are not fully clarified, we may find it useful to refer to the function of the entomologist in the study of diseases. In doing so we acknowledge without reservation that it is primarily the medical profession that has benefited the world by work on insect-borne diseases. Smith and Kilbourne, Ross, Manson, Reed and his colleagues, Marchaux and Salembeni, Dutton and Todd and Ricketts-all intimately associated with splendid achievements were not entomologists.

In the first place entomologists are needed in the experimental work that will lead to either a demonstration or a denial of the existence of insect porters of any particular malady. Suppose, for instance, we have a disease the etiology of which is obscure and which theoretically may be transmitted by insects. The first step to be taken is to determine what insects should be taken into consideration. Here the knowledge of the entomologist on the life history and habits of the different species comes immediately into play. He can furnish an

intelligent list of suspects, whereas the non-entomological investigator would be compelled to grope about in the darkness and might experiment for years along fruitless lines. In this connection let us refer to the work of Reed and his colleagues on yellow fever. That was a case in which no time was lost and in which it might appear that a knowledge of entomology had little to do with the solution. In making plans to determine whether an insect was the transmitter of the disease, Doctor Reed and his colleagues went to Doctor Finlay. He was not an entomologist, properly speaking, but had been studying mosquitoes for many years. These studies made him familiar with the habits of the Cuban species. He had learned that one species alone should be considered. He had specimens in his possession and actually gave Reed the eggs from which were bred the first mosquitoes that conveyed yellow fever in the experiments. To this extent the work of the Reed commission was started without delay on the right course on account of the entomological knowledge of Doctor Finlay. Moreover Reed and his collaborators were in constant communication with Doctor Howard and spent some time in Washington studying mosquitoes while the Cuban experiments were under way.

When a list of possible transmitters of a disease is formulated and transmission experiments begin, the work of the entomologist is even more essential than before. It is necessary to obtain specimens, breed them and handle them. Immediately a host of points about.feeding and manipulation come up, and here again the entomologist is the only man who can supply the information. Suppose the investigation has been continued and it has been found that one or more species are the sole or important agents in the transmission of the malady. At this juncture the work of the entomologist becomes more important than at any other time. In fact, here something close to a separation between entomology and medical science takes place. The control of the disease becomes a question of the control of the transmitting agent and no one can deny that the entomologist is more fitted than anyone else to devise means for the control of insects and to carry them out.

The present practical unanimity of opinion that the primary method of controlling insect-borne diseases is through attack against the insect host and that the control of the human host is secondary is the outcome of practical experience. After the demonstration of the carriage of yellow fever by the mosquito, the first idea of medical men was to control the human host by isolation and to suppress the insect host only as a supplementary measure. The work of Gorgas at Havana in 1901, of Liceaga in Vera Cruz, of White in New Orleans and of Gorgas in Panama was all based upon this conception. But now

the very men who accomplished this magnificent work have change their views. We quote from Dr. H. R. Carter, "Yet Gorgas now b lieves, and I think all who participated in the work here concur wit him unreservedly, that his success in Havana and on the Isthmus wa due to the war waged against the Stegomyia directly, by the destruc tion of their breeding places, undertaken as an adjuvant to the isola tion of the sick, rather than to that isolation itself; to the control o the insect rather than of the human host."

As Doctor Carter points out, the elimination of the disease by the management of the human host failed because that host could not be controlled. We believe that the experience with yellow fever will be duplicated in practically all insect-borne diseases. Apparently healthy carriers will always interfere with attack against the disease through the human host. Nothing short of the suppression of the insect host will yield satisfactory results, and it is most encouraging that medical men seem practically universally to have arrived at this conclusion. The recent work of Celli in Italy in which medication with quinine rather than Anopheles destruction is the basis, is an exception.

The recent work on Stomorys calcitrans and poliomyelitis shows in a striking manner one of the incidental reactions of such discoveries on the entomologist. The work of Brues, Sheppard and Rosenau elevates the stable fly immediately from a position of one which has but little interest, except in connection with live stock, to one of extreme importance in connection with a most distressing human disease. Full information regarding the fly is immediately demanded. We turn to the literature to find it, but discover that as far as the American writings are concerned everything is covered in an aggregate of six to ten pages. It now becomes necessary for the entomologist to study the insect in all its habits and stages.

There are probably many cases in which insects come into important connection with diseases other than as carriers. Take the case of pellagra, for instance. The students of this malady are divided into two very distinct schools: those who believe in the causation by spoiled corn and those who adhere to the theory of insect transmission. If the zeistic school, to which practically all of the Italian investigators belong, should be found to be right, insects would still come into consideration in connection with the deterioration of the corn. In this country, as elsewhere, the injury to corn by insects begins in the field and continues when the harvest is placed in storage. Thus if it is an Aspergillus or a Penecillium that causes the disease, the insects injuring the stored product and starting decay are likely to have some connection with it.

COOPERATION NECESSARY

This subject is one in which coöperation by a number of classes of investigators is indispensable. Everyone must admit that experiments in disease transmission by insects should be conducted coöperatively by entomological and medical men. Neither class can do the best work and obtain definite results without loss of time unless the other one works shoulder to shoulder with it. In this respect, however, medical entomology does not differ from other departments of the science. In spraying work, for instance, the entomologist necessarily coöperates with the chemist and horticulturist. In the medical work he must coöperate with the clinician, the bacteriologist and the protozoologist, but the share of the work devolving upon the entomologist in one case is certainly as great as in the other.

The recent excellent work of Brues, Sheppard and Rosenau is an example of the rapid progress that can be made and the satisfactory results that can be obtained when the proper cooperation of the two interests concerned is established. The same advantage is expected in the present work of the Bureau of Entomology on the possible transmission of pellagra by insects. Messrs. A. H. Jennings and W. V. King, who are engaged in this investigation, have conducted their studies in the closest coöperation with the Thompson-McFadden Pellagra Commission of the New York Post-Graduate School of Medicine headed by Capt. J. F. Siler, of the Army Medical Corps, who, by his work in Italy and elsewhere, has become one of the foremost students of the disease.

IMPORTANCE OF MEDICAL ENTOMOLOGY IN THE UNITED STATES

One very recent event which has caused medical entomology to become of more direct concern to the people of the United States is our territorial expansion. We now have the Hawaiian Islands, the Philippines, Guam, Porto Rico and the Canal Zone. In these possessions many of the insect-borne diseases which do not occur within the United States proper are known to exist. Military and commercial interests cause intimate intercourse between this country and the outlying possessions. This naturally has the effect of greatly increasing the importance of full knowledge regarding any insects which may transmit these diseases if they become introduced.

However, the great importance of insects concerned in the transmission of disease, from the American standpoint, is not connected with tropical maladies which may be introduced and become epidemic here, but with a number of important endemic diseases. In the case of man we have malaria, dengue, spotted fever, a form of ophthalmia,

typhoid fever, tuberculosis, leprosy, poliomyelitis, dysentery and oth diseases in which insects are known to be concerned. In the case diseases of domestic animals we have splenetic fever of cattle, and the is a strong suspicion that infectious anemia of horses is transmitted b Stomoxys calcitrans, to say nothing of the possible presence withi our boundary also of spirillosis of fowls transmitted in other countrie by a tick which is very common in the Southwest.

In the group of exotic diseases of man we have yellow fever, plague cholera and others. Our public health service is wide awake and efficient, but the impossiblity of preventing the invasion of our country by exotic diseases is shown by the presence of plague in California and the outbreak of yellow fever in New Orleans not later than 1905. As long as it seems to be humanly impossible to prevent the invasion of such diseases, the study of the native insects which can transmit them will require investigation.

The danger of the introduction of new diseases in this country is illustrated in a case of shipment of Indian cattle which was brought to New York a few years ago. In order to be safeguarded, a veterinarian accompanied the importer to India where he made repeated blood examinations of every animal that was selected. Such care is

not exercised with human immigrants. The examinations were continued while the cattle were en route. As an extra precaution the animals were kept at quarantine off the harbor at New York for some weeks. Here it was found that the trypanosome which is the causative agent in surra was present. It is not difficult to imagine similar cases in which diseases might pass through the quarantine. In the case of surra, for instance, we have a number of species of insects that can carry it from one aninal to another. In fact, we have one of the identical species, Stomorys calcitrans, which has been proven to be a transmitter of this malady in the Philippines and elsewhere.

Narrowing our inquiry we will now consider the four specific diseases of man and one of cattle occurring in the United States, which, ast far as known, are transmitted only by insects. These are malaria, dengue, spotted fever, typhus, and splenetic fever of cattle.

Very recently students of conservation have furnished data that lead to much greater exactness in the determination of the losses caused by human diseases than was formerly possible. The most notable work of this kind has been done by Prof. I. Fisher of Yale University. As the result of most careful ealculations he has concluded that the average economic value of the lives now sacrificed by preventable diseases is $1,700. He has also estimated in certain cases the loss due to invalidism not resulting in death. These determina