2 INTRODUCTION 



gusting pest which should be put down if possible. 

 Then the ravages caused by common house-flies 

 among children especially seem to be so little 

 known or are so commonly ignored by the general 

 public that an attempt to describe the knowledge 

 which has been gained during the past few years 

 and a method of applying that knowledge is well 

 justified. It is of the utmost importance that this 

 knowledge should be disseminated, because flies can 

 be easily reduced in numbers, and the diseases con- 

 veyed by them may thus be prevented to some 

 considerable extent. Scientific research, the gaining 

 of knowledge, is of little use unless it is followed 

 by the practical application of the discoveries made. 

 Too often important observations are published in 

 scientific memoirs or read before scientific societies, 

 and they then remain buried in the obscurity of the 

 bookshelf for years until somebody realises the possi- 

 bility of their practical application and usefulness. 



So it is with our knowledge concerning the 

 dangers of house-flies. It has been known for years 

 that the common domestic fly, Musca domestica, can 

 convey typhoid fever and infantile enteritis from one 

 person to another, but little organised attempt seems 

 to have been made to bring such knowledge to 

 public notice or to induce authorities concerned to 

 reduce the numbers of these insects in localities w r here 

 they do the most harm. This is due to ignorance, 

 perhaps, or to that apathy which has been said to 

 exist appertaining to all matters concerning the dis- 

 eases which destroy human life. But it seems more 

 probable that this apathy is really due to the fact 

 that the general public has not grasped the essentials 

 which are known concerning many of these diseases. 



