THE TYPHOID FLY, OR HOUSE FLY. 25 



origin of the fever was confirmed. The conclusion was reached that 

 tlie fever is disseminated by the transference of the excretions of an 

 infected individual to the alimentary canals of others, and that a 

 man infected with typhoid fever may scatter the infection in every 

 latrine or regiment before the disease is recognized in himself, while 

 germs may be found in the excrement for a long time after the 

 apparently complete recovery of the patient. Infected water was 

 not an important factor in the spread of tjq^hoid in the national 

 encampments of 1898, but about one-fifth of the soldiers in the 

 national encampments in the United States during that summer de- 

 veloped this disease, while more than 80 per cent of the total deaths 

 were caused by typhoid. 



In 1899 the writer began the study of the typhoid or house fly 

 under both country and city conditions. He made a rather thorough 

 investigation of the insect fauna of human excrement, and made a 

 further investigation of the species of insects that are attracted to 

 food supplies in houses. In a paper entitled "A Contribution to the 

 Study of the Insect Fauna of Human Excrement (with special refer- 

 ence to the spread of typhoid fever by flies)," published in the Pro- 

 ceedings of the Washington Academy of Sciences, Volume II, pages 

 Sil-GOI, December 28, 1900, he showed that 98.8 per cent of the whole 

 number of insects captured in houses throughout the whole country 

 under the conditions indicated above were Musca domestica^ the 

 typhoid or house fly. He showed further that this fly, while breeding 

 most numerously in horse stables, is also attracted to human excre- 

 ment and will breed in this substance. It was shown that in towns 

 where the box privy was still in existence the house fly is attracted to 

 the excrement, and, further, that it is so attracted in the filthy regions 

 of a city where sanitary supervision is lax and where in low alleys 

 and corners and in vacant lots excrement is deposited by dirty people. 

 He stated that he had seen excrement which had been deposited over- 

 night in an alleyway in South Washington swarming with flies under 

 the bright sunlight of a June morning (temperature 92° F.), and that 

 within 30 feet of these deposits were the open windows and doors of 

 the kitchens of two houses kept by poor people, these two houses 

 being only elements in a long row. The following paragraph is 

 quoted from the paper just cited: 



" Now, when we consider the prevalence of typhoid fever and that 

 virulent typhoid bacilli may occur in the excrement of an individual 

 for some time before the disease is recognized in him, and that the 

 same virulent germs may be found in the excrement for a long time 

 after the apparent recovery of a patient, the wonder is not that ty- 

 phoid is so prevalent but that it does not prevail to a much greater 



