270 THE DISSEMINATION OF OTHER DISEASES BY FLIES 



transfer the virulent germs may appear to be lessened. A careful 

 consideration of the facts, nevertheless, will show that this is far 

 from being the case. My experiments and observations on the 

 feeding habits of the fly have shown that this insect is especially 

 fond of and attracted to sputum. This is a matter of common 

 observation where spittoons or cuspidors are used and are not 

 kept in a clean condition. There is no lack of opportunity, under 

 natural conditions, for flies to infect themselves externally and 

 internally with the tubercle bacilli. To what extent they may 

 prove the means of infection depends upon their access to food. 

 In my opinion their greatest danger lies in the possibility of their 

 coming into contact with the mouths or food of helpless infants. 



Spillman and Haushalter were the first to carry out bacterio- 

 logical investigations on the dissemination of Bacillus tuheixulosis 

 by flies. As early as 1887 they found this bacillus in large 

 numbers in the intestines of flies from a hospital ward, and also 

 in the dejections which occurred on the windows and walls of the 

 ward. Hoffmann (1886) also found tubercle bacilli in the excreta 

 of flies in the room where a patient had died of tuberculosis, and 

 he also found the bacilli in the flies' intestinal contents. One out 

 of three guinea-pigs which were inoculated with the flies' intestines 

 died ; two inoculations with the excreta had no eflect, which led 

 him to believe that the bacilli became less virulent in passing 

 through the fly's alimentary tract. But Celli {I.e.) records ex- 

 periments in which two rabbits inoculated with the excreta of 

 flies fed with tubercular sputum developed the disease. 



Hayward (1904) obtained tubercle bacilli in ten out of sixteen 

 cultures made from flies which had been caught feeding on bottles 

 containing tuberculous sputum. Tubercle bacilli were also re- 

 covered from cultures made from faeces of flies which had fed in 

 the same manner, which apparently caused a kind of diarrhoea in 

 the flies, and they died from two to three days afterwards. Faeces 

 of flies fed on tubercular sputum were rubbed up in sterile water 

 and injected into the peritoneal cavity of guinea-pigs, which de- 

 veloped tuberculosis. Buchanan (1907) allowed flies to walk over 

 a film of tubercular sputum and then over agar ; the agar was 

 then washed with water and a guinea-pig died of tuberculosis in 

 thirty-six days by inoculating it with the resulting solution. 



