CARRIAGE OF DISEASE 111 



ing them from one place to another. We regard it as 

 certain that they convey cholera and typhoid fever, 

 and we look forward with confidence to the complete 

 demonstration that they convey the causative agents 

 of infantile diarrhea and of dysentery, always remem- 

 bering that there are other vehicles, water, milk, etc., by 

 which these diseases may be communicated. 



''It should be remembered that a fly may cause rela- 

 tively gross infection of any food upon which it alights 

 after having fed upon infective substances, be they 

 typhoid, cholera, or diarrhea stools. Not only is its 

 exterior contaminated, but its intestine is charged with 

 infective material in concentrated form which may be 

 discharged undigested upon fresh food which it seeks. 

 Consequently, the excrement voided by a single fly may 

 contain a greater quantity of the infective agents than, 

 for instance, a sample of infected water. In potential 

 possibilities the droppings of one fly may, in certain 

 circumstances, weigh in the balance as against buckets 

 of water or of milk !" 



Surely no more authoritative or complete statement 

 than this could be made by scientific men. 



The whole literature of the subject of the transfer of 

 disease by insects and like creatures was first compre- 

 hensively studied and collected by Dr. George H. F. 

 Nuttall and published in 1900 in an admirable and ex- 

 tended paper in the Johns Hopkins Hospital Reports, 

 entitled *'On the Role of Insects, Arachnids and Myria- 

 pods, as Carriers in the Spread of Bacterial and Para- 

 sitic Diseases of Man and Animals. A Critical and 



