146 TYPHOID FEVER 



several instances campaigns undertaken to exterminate flies have 

 met with marked success. The reports relating to military 

 camps in war time show very conclusively that flies are under 

 those conditions the principal agents in spreading the disease. 

 Both in Indian stations and in military camps it is probable that 

 ' carriers ' and incipient cases are largely responsible for providing 

 the necessary infected material. 



Much investigation is still required before the part played by 

 the fly in various circumstances is fully understood. 



Diseases caused by allied organisms. 

 (i) Dysentery. 



Though it is very probable that flies may occasionally 

 distribute the bacilli of dysentery, little evidence directl}' bearing 

 on the subject has yet been published. Orton (i 910) in America 

 investigated an outbreak of 136 cases of dysentery in the 

 Worcester State Hospital for the insane, and came to the 

 conclusions that flies, which were present in unusual numbers, 

 were entirely responsible for the outbreak. B. dysenteries was 

 not isolated from flies, but an interesting experiment was made 

 with B. prodigiosus. Cultures of this organism were exposed in 

 the laundry, where the bedding and clothing were cleaned, and 

 from some of the flies subsequently caught in other rooms of the 

 hospital this bacillus was isolated. Since many of the non-lactose 

 fermenting bacilli found in the intestines of flies are indistinguish- 

 able culturally from B. dysenteric, agglutination and absorption 

 tests would have to be employed in identifying any suspicious 

 organisms that might be isolated from suspected flies. 



(ii) Paratyphoid ajid food poisoning. 



Graham-Smith (1910, p. 14) carried out the following experi- 

 ments with B. enteritidis (Gaertner). 



" An emulsion of an agar culture of B. enteritidis (Gaertner) in syrup was placed 

 in a gauze cage containing a large number of flies. Eight hours later the emulsion 

 was removed and plain syrup substituted. Each day a certain number of flies were 

 caught in a large test-tube ; some were allowed to walk over Drigalski-Conradi plates, 

 and others were killed and their intestines dissected out and emulsified and sown on 

 similar plates. The faeces deposited on the test-tube were also emulsified and sown on 

 plates. 



