CARRIAGE OF DISEASE 
103 
pathogenic bacteria do not usually suryive more than 
a few hours (five to eighteen) on the legs and wings. 
Nevertheless, flies allowed to walk over sterile agar 
plates may cause infection for several days. This 
seems to be due to the fact that they frequently attempt 
to suck the surface, and in so doing infect it with fluid 
regurgitated from the crop. Within the crop non- 
spore-bearing bacteria frequently survive for several 
days, and they usually survive even longer in the 
intestine. No evidence of multiplication in either df 
these situations has been obtained. The feces deposited 
by such flies often contain the organisms in consider¬ 
able numbers for at least two days, and are frequently 
infective for much longer periods. Anthrax spores 
survived for many days on the exterior and in the ali¬ 
mentary canal. 
“Experiments with B. prodigiosns show that flies 
may infect sugar forty-eight hours after feeding on 
infected material, and that clean flies may infect them¬ 
selves by feeding on the recent deposits of infected 
flies. In the few experiments which were tried, milk 
and meat were not infected. Flies fed on anthrax 
spores did, however, infect the syrup which' was given 
to them as food. 
“In the experiments which have been described, very 
gross infection was produced in most cases by emul¬ 
sions of pure cultures. It is improbable, however, that 
under natural conditions flies would often have the op¬ 
portunity of feeding on materials which contain path¬ 
ogenic organisms practically in pure culture. The ef- 
