i9i3 _I 9 I 4-] The Common House Fly. 125 



or six days in their alimentary canal. Indeed the larvse of 

 flies, if they feed on material containing typhoid organisms, 

 retain the infection when they develop into mature flies. 



Epidemic or summer diarrhoea is a disease which takes toll 

 of an enormous number of infant lives, and, as in the case of 

 enteric fever, there is an intimate relation between the storage 

 of excreta and a high mortality from diarrhcea. The infected 

 flies convey the organisms to the milk given to the infants, or 

 settle on the lips or nose and directly transmit infection. 

 The dirtier the village or town, the greater is the number of 

 flies and the greater is the mortality from diarrhcea. In the 

 same town, if attention be given to sanitation and cleansing, 

 the number of flies diminishes and the incidence of diarrhcea 

 ceases. The dirtier the house, the greater the number of flies, 

 the larger the number of cases of epidemic diarrhcea. The 

 same conclusions hold in regard to the propagation of cholera. 



Though flies are often found feeding on tuberculous sputum, 

 &c, no direct evidence of the propagation of this disease by 

 flies has been adduced. It points, however, to the advisability 

 of great care being taken to destroy tuberculous material, so 

 as not to allow flies to gain access to it. 



Anthrax is a very deadly disease affecting oxen, sheep, and 

 occasionally man. Flies infected with this organism may 

 retain the infection for many days, and indeed the spores 

 may remain alive in dead flies for an indefinite time. 

 Diphtheria may infrequently be carried by flies. The eggs 

 of parasitic worms may also be carried by flies, — the larvse 

 may eat them and, in the fully-formed fly, the eggs may be 

 found, and so the disease may be transmitted to animals 

 or man. 



When flies have fed on plague material they are enabled 

 to carry the disease, but to themselves the disease is fatal in 

 from seven to eight days. The bacilli remain virulent in 

 them for two days, and hence flies are a real danger in 

 propagating this disease. In Egypt and other countries it 

 is almost undoubted that the disease of ophthalmia is trans- 

 mitted from child to child by flies, and it is a terrible sight to 

 see swarms of flies attacking the tender eyes of little children 

 there. 



It is worth considering the means to be taken to control 



