NON-BLOOD-SUCKING FLIES 295 



carry on their feet and in their crops the bacteria 

 of nearly all the important infectious diseases and 

 distribute them. Further the flies are not affected 

 by these bacteria. 



In civilized countries, with efficient drainage and 

 scavenging systems and suitable hospital accom- 

 modation for infectious patients, flies seldom obtain 

 opportunities of acquiring and carrying the bacilli 

 of typhoid fever, dysentery or other similar diseases. 

 On the other hand evidence is accumulating to show 

 that they are very important agents in the dissemina- 

 tion of epidemic diarrhoea, a disease which causes 

 a very great annual mortality amongst children. 

 In tropical countries it seems almost certain that 

 they are responsible to some extent for the spread 

 of ophthalmia, cholera and some other diseases. 



On the other hand in war-time their oppor- 

 tunities for acquiring and spreading the bacilli of 

 typhoid fever and allied diseases are almost un- 

 limited, and many competent observers have 

 thought that they are responsible for a not incon- 

 siderable proportion of the sickness that prevails. 

 A quotation from the report of the American 

 Commission, which investigated the sanitary con- 

 ditions prevailing during the Spanish-American 

 War, may suffice to illustrate the importance of 

 non-blood-sucking flies in war time. 



"There is no doubt that air and sunlight kill 

 infection, if given time, but their very access gives 

 opportunities for the flies to do serious mischief as 



