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 spirochaete 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 Spiroch&ta 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 
