THE HOUSE-FLY 19 



aration of vegetable salads. The typhoid bacillus 

 grows on the surface of potatoes readily, and this accounted 

 for the outbreak, on the necessary supposition that the 

 woman was of uncleanly habits. The curious point in 

 this case was that she had had typhoid thirty-six years 

 previously for the only time." 



It is difficult to detect these chronic carriers, and often 

 a serious problem to know what to do with them when 

 found. It is evident that they are dangerous and un- 

 doubtedly many, of whose presence we are unaware, are 

 in existence. It is important that all possible efforts 

 should be made to detect them and it is equally important 

 that none of them should be allowed to take any part in 

 the production or sale of milk or its products and no part 

 in preparing and handling food. 



FLIES THAT BREED IN HUMAN EXCREMENT 



Since flies take up bacilli on their feet, from places 

 where they breed and over which they walk and carry 

 them into our dwellings, it becomes pertinent to ascertain 

 what flies breed in human excrement and whether such 

 flies enter our houses. L. O. Howard, in an investigation 

 of this subject, found that 36 species of flies actually 

 breed in human feces and 41 species were found 

 visiting this substance or feeding upon it. Of these 

 77 species, he found that six were in the habit of visiting 

 houses and were actually caught in dwellings. At the 

 head of these stood the common house-fly, which was, 

 by far, the most abundant fly in houses, but not, be it 

 said, the most numerous one on the excrement. 



It is almost superfluous to point out and emphasize 



