172 THE HOUSE FLY—DISEASE CARRIER 
survive for eight days after feeding on infected organs 
and that they still harbored virulent bacilli forty-eight 
hours and more after they were transferred to clean 
vessels. At high temperatures the infected flies died 
more rapidly than controlled flies which were fed on 
the organs of healthy animals, from which he concluded 
that the plague bacillus may be fatal to house flies un¬ 
der suitable conditions of temperature. This possibly 
accounted for the dead flies noted by Yersin in his 
Hong-Kong laboratory. Nuttall also points out that 
a French observer, Matignon, observed in 1898 that 
flies died in large numbers in Mongolia during plague 
times. 
Tropical Sore 
This disease is referred to by Nuttall and Jepson 
under this name aftd also under the name “Bouton de 
Biskra.” They state that it is asserted by Laveran 
and Seriziat (1880) that flies convey this trouble. In 
other localities, the natives declare that the disease is 
caused by the bite of certain insects. It is said that 
Seriziat asserts that a lesion of the skin is always neces¬ 
sary for an infection to take place, and that it unques¬ 
tionably results at times as a consequence of mosquito 
bite. Laveran in his observations at Biskra stated that 
from September to October the slightest wound tends 
to be transformed into the bouton. He has seen it graft 
itself upon pustules of acne, upon vaccine pustules, and 
upon wounds following burns or blisters. He does not 
doubt that it is carried by flies on their feet and on their 
beaks. 
