268 THE DISSEMINATION OF OTHER DISEASES BY FLIES 



These experiments only prove the ability of flies to mechanically 

 transfer the anthrax bacilli from infected to uninfected matter. 

 Graham-Smith (1910 and 1911), however, has carried these ex- 

 periments further with a view to discovering, among other points, 

 the length of time that flies may carry the bacilli or its spores, 

 B. anthracis being a spore-bearing bacillus and consequently more 

 adapted for transference. Flies were placed for one hour in a cage 

 containing the body of a mouse just dead of anthrax, its body 

 having been opened to enable the flies to feed upon its blood. 

 The flies were afterwards transferred to a clean cage which on the 

 following morning was found to contain red spots of vomit and 

 yellowish faeces. B. anthracis was found in the former both 

 microscopically and by cultures. The flies were transfeiTed daily 

 to fresh cages and fed on syrup ; at intervals specimens were 

 removed and dissected and cultures were made on agar from their 

 legs, wings, heads, crops and intestinal contents. Cultures were 

 also made from the faeces. As a result of these careful examina- 

 tions, it was found that the non-spore-bearing anthrax bacilli did not 

 remain alive on the external parts of the fly for more than twenty- 

 four hours. They remained alive in the intestine for three days 

 and in the crop for five days, especially when this organ contained 

 partially coagulated blood. The bacilli were present in the faeces 

 deposited forty-eight hours after infection. No spore-bearing 

 forms were obtained from film preparations made at various times 

 from the contents of the crop and the intestine. Experiments 

 were also carried on with the spores of B. anthracis. An emulsion 

 of an old anthrax culture was made and heated to 70° C. for fifteen 

 minutes, after which a number of flies were allowed to feed on it. 

 These flies were then transfeiTed to fresh cages daily and fed on 

 syi-up and as in the previous experiment specimens were caught 

 and dissected at intervals, agar cultures being made from their 

 legs, wings, heads, crops and intestinal contents and faecal deposits. 

 Smears were made from the crop and intestinal contents at various 

 times but the absence of anthrax bacilli on microscopic examina- 

 tion demonstrated that the spores do not develop in the fl}'. This 

 experiment showed that flies infected with anthrax spores may 

 carry the spores upon their legs and Avings for at least twelve days, 

 and that the spores are present in considerable numbers in the 



