CARRIAGE OF DISEASE 167 



order whose skins are whole; for which reason the 

 whites are rarely infected ; but the backs of negroes, be- 

 ing often raw by whipping, and suffered to remain 

 naked, they scarce ever escape." 



Nuttall and Jepson state that Wilson (1868) says 

 that the belief prevails in the West Indies that this dis- 

 ease is carried by flies. They also show that Hirsch 

 (1896) reports two cases in which he thinks the dis- 

 ease was conveyed by flies. They also quote Cadet to 

 the effect that lesions of the skin are necessary for in- 

 fection, and that this may occur through direct contact 

 with infected clothes or flies, the latter transporting 

 the virus on their feet, which are soiled with diseased 

 secretions. 



The causative organism of yaws is supposed to be 

 an extremely delicate spirocha^te very much like that 

 of syphilis. Castellani (1907) reports experimental in- 

 vestigations showing that with monkeys the disease can 

 be conveyed by inoculation, showing also that yaws 

 and syphilis are different diseases. The causative or- 

 ganisms of the two diseases appear to be distinct, that 

 of yaws being called Spirochceta pertenuis. He makes 

 the statement that there can be no doubt of the con- 

 veyance of the disease by direct contact from person 

 to person, and that under certain conditions it may be 

 conveyed by flies and possibly by other insects. 



Ophthalmia 



A number of years ago, while studying the habits 

 of certain minute flies of the genus Hippelates, which 



