166 THE HOUSE FLY— DISEASE CARRIER 



in many of the West Indian Islands, in Ceylon, Java, 

 in Fiji, and Samoa, and other Pacific islands. It oc- 

 curs in China, but is rare there. It is highly contagious, 

 but simple contact of the skin is not sufficient — an 

 abraded surface is necessary. Sir Patrick Manson says 

 that probably the virus is often conveyed by insect bites 

 or by insects acting as go-betweens and carrying it from 

 a yaw sore to an ordinary ulcer ; thus the disease often 

 commences in a pre-existing ulcer. It is neither hered- 

 itary nor congenital. 



Prof. E. W. Gudger, of the State Normal College 

 at Greensboro, N. C, has called attention to a very 

 early idea as to the carriage of yaws by flies, on pages 

 385 to 386 of Dr. Edward Bancroft's ''An Essay on 

 the Natural History of Guiana in South America," 

 published in London in 1769. Doctor Bancroft writes, 

 ''The yaws are spongy, fungous, yellowish, circular pro- 

 tuberances, not rising very high, but of different mag- 

 nitudes, usually between one and three inches circum- 

 ference. These infest the whole surface of the body 

 and are commonly so contiguous that the end of the 

 finger 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. * * * It is 

 usually believed that this disorder is communicated by 

 the flies which have been feasting on the diseased ob- 

 ject to those persons who have sores or scratches which 

 are uncovered; and from many observations I think 

 this is not improbable, as none ever receive this dis- 



