PREFACE 



A LTHOUGH it is now generally recognized that flies 

 ** are very important agencies in the dissemination of 

 infectious diseases, few people are aware, of the remarkable 

 advances which have resulted from modern research in this 

 field. To the general public the practical application of 

 these researches appeals with greater force than the detailed 

 accounts of investigations, of absorbing interest though many 

 of them are, in the varied subjects which have to be called 

 to our aid in combating disease. Some of the results hitherto 

 obtained may be illustrated by two examples, both of which 

 have brought this subject into some prominence. 



In the first of these, Yellow Fever, owing to the factors 

 involved being relatively simple, it is literally possible within 

 a few months to remove this most deadly disease from the list 

 of human ailments. All that is required is public appreciation 

 of the remedies at our disposal, as demonstrated by the result 

 of the admirable measures adopted by the Americans first in 

 Cuba and afterwards in Panama, which alone rendered possible 

 the completion of the Canal. Similar measures in other 

 regions directed against the mosquito (Stegomyia fasciata), 

 which is responsible for the transmission of the infection, 

 would render the reappearance of Yellow Fever in the highest 

 degree improbable in the future. 



Sleeping Sickness may be taken as our second example. 

 The difficulties in this case are undoubtedly more formidable, 

 owing to the extreme complexity of the modes of dissemination. 



