280 THE DISSEMINATIOX OF OTHER DISEASES BY FLIES 



tabulated results it would appear that B. diphtheriae seldom 

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

 In the crop and intestine they may live for twenty-four hours or 

 occasionally longer. The faeces passed during the first few days 

 after infection are frequently infected. These experiments would 

 indicate, therefore, the ability of the house-fly to carry infection if 

 suitable conditions occur. 



Yaws {Framhoesia tropica). 



This disease which is widely distributed throughout the tropics 

 and is especially common on the west coast of Africa is extremely 

 contagious. It is characterised by ulcerous papules which develop 

 into fungus-like incrustations of a spreading and intensely dis- 

 agreeable nature. Gudger (1910) has called attention to a very 

 early suggestion that flies carry the infection of this disease. This 

 is contained in Bancroft's Essay on the Natural History of Guiana 

 in South America which volume was published in I7fi9. The 

 author states : " The yaws are spungey, fungous, yellowish, circular 

 protuberances, not rising very high, but of different magnitudes, 

 usually between one and three inches in circumference. These 

 infest the whole surface of the body, and are commonly so con- 

 tiguous that the end of the fingers cannot be inserted between 

 them ; and a small quantity of yellowish pus is usually seen 

 adhering to their surface, which is commonly covered with flies 

 through the indolence of the Negroes. This is a most trouble- 

 some, disagreeable disorder, though it is seldom fatal. Almost 

 all the negroes once only in their lives, are infected with it, and 

 sometimes the whites also, on whom its effects are much more 

 violent. It is usually believed that this disorder is communicated 

 by the flies that have been feasting on a diseased object, to those 

 persons who have sores, or scratches, which are uncovered, and 

 from many observations, I think that this is not improbable, as 

 none ever receive this disorder whose skins are whole ; for which 

 reason the Whites are rarely infected, but the backs of the Negroes 

 being often raw with whipping and suffered to remain naked, they 

 scarce ever escape it." 



Gudger (Lc.) also calls attention to Kosters' Travels in Brazil 



