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STRUCTURE, DEVELOPMENT, AND BIONOMICS OF HOUSE-FLY. 385 



1. Typhoid Fever. 



Of all infectious diseases the conditions in this are most 

 favourable for the transference of infection by M. domestic a,, 

 and it is no doubt on this account that the greatest attention 

 has been paid to the role of house-flies in the dissemination 

 of this disease. The chief favourable condition is that the 

 typhoid bacillus occurs in the stools of typhoid and incipient 

 typhoid cases. Human excrement attracts flies not only on 

 account of its moisture but as suitable food for the larvae. 

 The infected excrement is often accessible to flies, especially 

 in military camps, as will be shown shortly, and the flies also 

 frequent articles of food and not infrequently the moist lips of 

 man. Such are the conditions most suitable for the transfer- 

 ence of the bacilli, and it is on account of the frequent 

 coincidence of these conditions that flies can play, and have 

 played, such an important role in the dissemination of this 

 disease among communities, in spite of the fact that the 

 typhoid bacillus cannot survive desiccation, which I think is 

 an argument against its being carried by dust. 



Bpidemiological and other evidence. There is a 

 very large amount of testimony given as to the role played 

 by flies in the spread of enteric in military stations and camps, 

 and especially during the two wars the Spanish-American 

 and the Boer War. All the conditions most favourable for 

 the dissemination of the bacilli by flies were, and in many 

 military stations are still, present; open latrines or filth- 

 trenches accessible to flies on the one hand and on the other 

 the men's food within a short distance of the latrines. I 

 cannot do better than repeat the evidence in the words of the 

 witnesses and allow it to speak for itself. 



Yaughan, a member of the U.S. Army Typhoid Commis- 

 sion of 1898, states : l 



" My reasons for believing that flies were active in the dis- 

 semination of typhoid fever may be stated as follows : 



1 In a paper, " Conclusions Reached after a Study of Typhoid Fever 

 among American Soldiers," read before the American Medical Asso- 

 ciation at Atlantic City, N". J., in 1900. 



