THE TYPHOID FLY, OR HOUSE ELY. 

 Table III. — <S'o«rrt's of bacteria from ftiex. 



29 



AT- 

 Bate. 



1907. 

 July 27 



July 27 



Aug. 6 



Aug.l4 



Aug.l4 



Sept. 4 



Sept.21 



Sept.21 



Sept.27 



Aug.20 



(a) 1 fly, bacteriological 

 laboratory 



(h) 1 lly, bacteriological 



laboratory 



(c) 19 cow-stable flies 



Average per fly 



{d) 94 swill-barrel flies 



Average per fly 



(e) 144 pigpen flics 



Average per fly 



(/) 18 swill-barrel flies 



Average per fly 



(g) 30 dwelling-house flies. 



Average per fly 



{h) 26dwelling-house flies. 



Average per fly 



{i) llOdwelling-house flies. 



Average per fly 



(j) 1 large bluebottle 

 blowfly 



I'otal 

 number. 



Total average of 414 flies. . 



Average per cent of 414 

 flies 



Average per fly of 256 

 fiie.s, experiments (d) , 

 (e),and (/) 



Average per cent of 256 

 flies, experiments (d), 

 (f),and(/) 



7. 980, 



420, 



155, 000, 



1, 660, 



133, 000, 



923, 



118, 800, 



6, 600, 



1, 426, 



•17, 



22, 8S0, 



880, 



35, 600, 



322, 



3,150 



308, 700 



1,222,570 



3,061,000 



Total acid 

 bacteria. 



22, 

 13, 671 



250 



100 

 000 

 600 

 000 

 300 

 000 

 700 

 000 

 000 

 000 

 167 

 000 

 000 

 000 

 200 



(o) 



Bacterium 

 lactis 

 acidi. 



Group A. 

 Class 1. 



-'■(SoK-sero- 



genes. 

 Group A. 



Class 2. 



4, 320, 000 



46, 000 



933, 000 



6,500 



10,480,000 



682, 000 



367, 300 

 30 



765, 000 



7,830 

 6 



73, 500 

 6 



268, 700 



8 



211,600 



4,630,000 

 49, 300 



1,176,000 



12,200 



30, 000, 000 



1,600,000 



,'53,800 

 18 



» 2,200 mold spores. 



" From the above table the bacterial population of 411 flies is 2:)retty 

 well represented. The domestic fl}' is passing from a disgusting nui- 

 sance and troublesome pest to a reputation of being a dangerous 

 enemy to human health. A species of mosquito has been demon- 

 strated to be the cause of the spread of malaria. Another kind of 

 mosquito is the cause of yellow fever, and now the house fly is con- 

 sidered an agency in the distribution of typhoid fever, summer com- 

 plaint, cholera infantum, etc. 



" The numbers of bacteria on a single fly may range all the way 

 from 550 to 6,600,000. Early in the fly season the- numbers of bac- 

 teria on flies are comparatively small, while later the numbers are 

 comparativeljT^ very large. The place where flies live also determines 

 largely the numbers that they carry. The average for the 414 flies 

 was about one and one-fourth million bacteria on each. It hardly 

 .seems possible for so small a bit of life to carry so large a number of 

 organisms. The method of the experiment was to catch the flies from 

 the several sources by means of a sterile fly net, introduce them into 

 a sterile bottle, and pour into the bottle a known quantity of steril- 

 ized Avater, then shake the bottle to wash the bacteria from their 

 bodies, to simulate the number of organisms that would come from a 

 fly in falling into a lot of milk. In experiments ' c/,' ' e,'' and ' / ' 



