1 86 ANTHRAX 



spores may remain alive in dead infected flies for an indefinite 

 period. Flies, which emerge from larvje, which have fed on 

 spore contaminated materials, are also infected, and can distribute 

 the organism. The fseces deposited by infected flies certainly 

 remain infective for 20 days, and probably for a much longer 

 time. 



It is evident, therefore, that under suitable conditions, which 

 are not infrequently fulfilled, the bacillus may be distributed 

 by flies in many ways, though no definite evidence of infection 

 either in men or animals has yet been obtained. 



CHAPTER XVIII 



OTHER BACTERIAL DISEASES 



DiphtJiei'ia. 



Smith (1898) allowed flies to walk over material infected with 

 B. dipJitJieria; and then over sterile media. " Naturally he 

 obtained a positive result." Graham-Smith (1910, p. 33) carried 

 out two series of experiments with cultures of B. diphtJiericj^. 



"In the first, a number of flies were allowed to feed for 30 minutes on an emulsion 

 of B. diphtheria in saliva, and were then tiansferred to a fresh cage. At intervals 

 flies were killed and cultures made on transparent serum medium (Nuttall and 

 Graham-Smith, 1908, p. 150), from their legs, wings, heads, and crop and intestinal 

 contents." 



"These experiments seem to indicate that B. diphtherics seXdom. 

 remains alive for more than a few hours on the legs and wings, 

 but may live in the crop and intestine for 24 hours or occasionally 

 longer. The faeces passed during the first few hours are fre- 

 quently infected. It is very probable that these experiments 

 under-estimate the vitality of B. dipJitJiericc, since in man}' cases 

 film-forming bacilli overgrew the cultures." 



There is no evidence that under natural conditions flies are 

 concerned in the spread of this disease, which is usualh- not 

 prevalent when flies are numerous, but, under suitable conditions, 

 it is possible that the disease may be occasionally conveyed by 

 them. 



