PREFACE 



Instead, they should be adapted to practical purposes 

 applied for the good of suffering humanity ; and the best 

 way to do this is to bring out well-written, interesting, and 

 easily read books of this kind, so that all who run may 

 read and their readings endure. This book should assist 

 much to accomplish this end. Thus we may look forward 

 confidently to the day when house-flies, and the diseases 

 they carry, are things of the past. The " Book of the Fly " 

 must take its place in the history of the events which are 

 to lead up to the winning of that goal. 







HALFORD Ross 



(of the John Hmvard McFaddcn Researches at the 

 Lister Institute of Preventive Medicine}. 



