CARRIAGE OF DISEASE 105 



obtained B. typhosus from a number of flies caught in 

 various places where typhoid fever prevailed. He 

 further showed that B. typhosus or B. paratyphosus 

 (A) could be cultivated for several days from the in- 

 testines of perfect insects which emerged from larvae 

 fed on feces containing these organisms. 



"Several observers [Celli (1888), Hay ward (1904), 

 Lord (1904) and Buchanan (1907)] have shown that 

 the feces of flies which have fed on tubercular sputa 

 contain virulent tubercle bacilli. Buchanan (1907) 

 demonstrated that flies which had walked over nat- 

 urally infected anthracic meat were capable of infect- 

 ing agar plates. Yersin (1894) in Hong-Kong ob- 

 served many dead flies lying about in his laboratory 

 where he made autopsies on plague animals. He dem- 

 onstrated by inoculation into animals that a dead fly 

 contained virulent plague bacilli. 



"Finally the experiments of Macrae (1894) at the 

 Gaja jail show that exposed milk may become infected 

 by the agency of flies. 



"Even these observations only prove that cultures 

 of pathogenic organisms may occasionally be obtained 

 from naturally infected flies, and they do not afford 

 conclusive evidence that such flies are a frequent source 

 of disease in man by infecting food materials. Though 

 many of the observations cited by JSTuttall and Jepson 

 seem to indicate that flies have frequently acted as car- 

 riers of disease, it has only once (Macrae) been dem- 

 onstrated that food has actually been grossly contam- 

 inated by them." 



