FLIES AND TYPHOID FEVER. 



255 



striking. At the Presidio camp, the chance for the transfer of typhoid 

 by flies had by intelligent care been reduced to zero. This, however, 

 Mas, of course, a more or less permanent camp and opportunities were 

 better, but indicated in a beautiful way what might be done and what 

 should be done even in a temporary camp. 



(2) In towns where the box privy nuisance is still in existence 

 the house-fly is attracted to such places to a certain extent, though not 

 as abundantly as other flies, which, however, are not found in houses. 

 Observations to this effect were made by the writer and his assistants 

 in many parts of the United States. 



(3.) In the filthy regions of a city, where sanitary supervision is 

 lax, and where in low alleys and corners and vacant lots deposits are 

 made by dirty people, the house-fly is attracted to the stools, may breed 

 in them, and is thus a constant source of danger. The writer has seen 

 a deposit made over night in South Washington in an alleyway swarm- 



FlG. 8. MORELLIA MICANS— ENLARGED. 



Fig. 9. Myospila meditabukda— enlarged. 



ing with flies, in the bright sunlight of a June morning, temperature 

 92° F., and within thirty feet of this substance were the open doors and 

 windows of the kitchens of two houses occupied by poor people, these 

 two houses being only elements in a long row. 



The conclusions which the writer has reached after two years of 

 this experimental work are: 



(1) Of the seventy-seven species of flies found under such conditions 

 that their bodies, especially their feet and their proboscides, may 

 become covered with virulent typhoid germs, only eight are likely to 

 carry them to objects from which they can enter the alimentary canal 

 of man. 



(2) Of these eight species, two, namely, Lucilia ccesar and Calliphora 

 erythrocephala. can very rarely carry such germs, though they may 

 carry the germs of putrefaction and cause blood-poisoning, in alighting 

 upon abrasions of the skin or open wounds. 



