28 LOSS THKOUGH INSECTS THAT CARRY DISEASE. 



activity and prevalence of tlie common house fly is shown not only 

 by repeated observations but also by an interesting plotting of the 

 curve of abundance of flies in comparison with the plotted curve of 

 abundance of deaths from intestinal diseases, indicating that the 

 greatest numbei- of flies occurred in the weeks ending July 27 and 

 August 3; also, that the deaths from intestinal diseases rose above 

 the normal at the same time at which flies became prevalent, culmi- 

 nated at the same high point, and fell off wdth slight lag at the 

 time of the gradual falling off of the prevalence of the insects. 



Similar studies have been carried on during the summer of 1908 

 in the city of Washington, and the curve of typhoid-fly abundance 

 for the whole city, as well as that for a district comprising eight city 

 squares in wdiich intensive studies have been made both of flies and 

 of disease, wall be plotted at the close of the season. At the time 

 of present writing this work has not been completed. 



The typhoid fly also possesses importance as a disseminator of the 

 bacilli of tuberculosis. In a paper by Dr. Frederick T. Lord, of 

 Boston, reprinted from the Boston Medical and Surgical Journal for 

 December 15, 1904, pages 651-654, the following conclusions - are 

 reached : 



" 1. Flies may ingest tubercular sputum and excrete tubercle ba- 

 cilli, the virulence of wdiich maj^ last for at least fifteen days. 



" 2. The danger of human infection from tubercular flyspecks is 

 by the ingestion of the specks on food. Spontaneous liberation of 

 tubercle bacilli from flyspecks is unlikely. If mechanically dis- 

 turbed, infection of the surrounding air may occur. 



''As a corollary to these conclusions, it is suggested that — 



" 3. Tubercular material (sputum, pus from discharging sinuses, 

 fecal matter from patients with intestinal tuberculosis, etc.) should 

 be carefully protected from flies, lest they act as disseminators of the 

 tubercle bacilli. 



" 4. During the ^j season greater attention should be paid to the 

 screening of rooms and hospital wards containing patients with 

 tuberculosis and laboratories where tubercular material is examined. 



" 5. As these precautions would not eliminate fly infection by 

 patients at -large, foodstuffs should be protected from flies which may 

 already have ingested tubercular material." 



From all these facts it appears that the most important part played 

 by the typhoid fly or house fly in the human economy is to carry 

 bacteria from one place to another. The folloAving table and com- 

 ments are taken from Bulletin No. 51 (April, 1908). of the Storrs 

 Agricultural Experiment Station, Storrs, Conn., entitled " Sources of 

 Bacteria in Milk," by W. M. Esten and C. J. Mason : 



