228 THE DISSEMINATION OF PATHOGENIC ORGANISMS BY FLIES 



in number, while the larvae which had been feeding on B. typhosus 

 contained enormous numbers of the bacilli as both cultui'al and 

 microscopical study demonstrated. 



Graham-Smith (1911) carried out experiments on flies bred 

 from artificially infected larvae. He used the blow-fly Galliphora 

 erythrocepJiala and fed the larvae on meat infected with the anthrax 

 bacillus. These experiments gave results of a positive character 

 and are described in a later chapter on anthrax. 



In a further report Graham-Smith (1912) finds that of the 

 non-spore-producing organisms only those which are adapted to 

 the conditions prevailing in the intestine of the larvae, such as 

 Morgan's bacillus and certain non-lactose fermenting bacilli survive 

 through the metamorphosis and are present in the adult flies. 

 Such organisms as Bacillus typhosus, B. enteritidis and B. prodi- 

 giosus rarely survive. 



More recently Tebbutt (1912) has found that such pathogenic 

 organisms as Bacillus dysenteriae (type " Y ") cannot be recovered 

 from pupae or flies reared from larvae to which these organisms 

 have been administered. When larvae which have been reared 

 from disinfected ova have been fed on B. dysenteriae (type " Y ") 

 the organism is recovered in a small proportion of cases from the 

 pupae and flies. Under similar conditions B. typhosus was not 

 recovered. Further experiments appeared to indicate that the 

 process of metamorphosis is accompanied by a considerable de- 

 struction of bacteria present in the larval stage. Tebbutt believes 

 that there is but a remote possibility of flies becoming infected 

 from the presence of pathogenic organisms in the breeding ground 

 of the larvae. 



Nevertheless, it would appear that the experiments which 

 have been described demonstrate the possibility that flies, bred 

 from larvae which have bred in infected matter, may carry infec- 

 tion internally, and the practical significance of these i-esults 

 surely needs no explanation. 



