1917 ENTOMOLOGICAL SOCIETY. 57 



THE RELATION OE INSECTS TO DISEASE IN MAN AND ANIMALS. 



Dr. L. 0. Howard, Wa^iiingtox, D.C. 



There are many here to-niglit to whom much that I shall say will be an old 

 story. In fact, more than sixteen years ago, in a lecture which I gave before 

 the Iioyal Society of Canada, May 30th, 1900, I showed some of the same lantern 

 slide?, which I shall show to-niglit, and even then the interest in the subject was 

 very keen and was still keener when three and one-half years later I spoke before 

 the Entomological Society of Ontario, at its September, 1903, meeting at Ottawa, 

 on the transmission of yellow fever by mosquitoes. That time my lantern slides 

 were held up at the border, and I am able to-night to show them for the first time 

 to the members of. this Society. 



After all, what is a period of sixteen years in the history of medicine and 

 of medical discoveries? The whole great field has practically developed within the 

 liist twenty years. Take some standard medical work of twenty years ago, such 

 as the 1896 editions of Osier's " Theory and Practice of IMedicine," and you will 

 find absolutely no mention of insects as connected with the etiology of disease 

 either of man or of the higher animals. 



And yet the foundations were already laid. In 1889 Theobald Smith, eight 

 years out of Cornell, and six years out of the Albany Medical College, and already 

 farther advanced as an investigator than any of his teachers, discovered the 

 causative organism of the so-called Texas fever of cattle, in the shape of a minute 

 pear-shaped protozoan in the red blood corpuscles, to which was given the name 

 Pyrosoina higeminum (now known as Babesia hovis). AVith the experimental 'aid 

 of F. L. Kilbourne, a doctor of veterinary medicine and engaged, as was Dr. 

 Smith, 'in research work under the Bureau of Animal Industry of the United 

 States Department of Agriculture at "Washington, he showed that this organism is 

 carried from southern cattle to non-immune cattle by the so-called southern cattle 

 tick {Margaropits annulatvs). The results of this experimental work were pub- 

 lished in 1893. 



Even before this, Dr. Patrick Manson, now Sir Patrick Manson. demonstrated 

 the carriage of tljie parasitic worm, Filaria nocturna, responsible for certain of 

 the diseases grouped under the name filariasis, from mosquitoes to man. 



This, however, was by no means as significant as the discovery of Theobald 

 Smith, and undoubtedly attention would have been directed at an earlier date 

 to the possible transfer by insects of diseases caused by blood-inhabiting micro- 

 organisms with man, had the revolutionary paper by Smith and Kilbourne 

 attracted more general attention. But it came from a veterinary service, and was 

 published in the Annual Eeport of the United States Department of Agriculture, 

 a publication which at that time unfortunately received but little attention from 

 the scientific world in general. 



So it was not until 1897 tlrnt Eoss, at the suggestion of Manson. begaiv out 

 in India his work on the possible carriage of malaria by certain mosquitoes, an in- 

 vestVf^tion which resulted triumphantly in 1898, and which ranks as one of the 

 monumental discoveries in medical science. 



Ross's work was immediately corroborated by Italian workers, and intensive 

 investigations of the blood-inhabiting protozoa were immediately begun. In a very 

 short time sound proof of the carriage of yellow fever by Aedes mlopus was brought 

 forward by Walter Reed and his co-workers, Carroll, Lazear and Agramonte, and 

 research in this direction was taken up all over the world. Constantly increasing in 



