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 and 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. 



