FLIES AND THE PUBLIC HEALTH 



Flies in relation to Disease. Non-Bloodsucking Flies. By G. S. Grahat, 

 Smith, M.D., University Lecturer in Hygiene, Cambridge. 



Demy Svo. pp. xiv^-292. With ^4. plates and 32 text-figures. 

 Price loi. 6./. net 



The first volume in The Cambridge Public Health Series deals with 

 a subject which has hitherto received too little attention. 



" The work done up to the present " he says " has been mainly of a 

 preliminary character. It has, however, established certain very important 

 facts; that many of the non-biting flies found in houses walk over and feed 

 on decaying substances and 

 excreta of all kinds, and that 

 their larvae develop in them ; 

 that occasionallv disease-pro- 

 ducing bacteria may be pre- 

 sent in these excreta; that 

 flies can carry bacteria on 

 their limbs and bodies for 

 several hours, and internally 

 for several days; that for 

 some days they can infect 

 substances, including human 

 food materials, over which 

 they walk or defaecate,. and 

 on which they feed ; and 

 that their habits are such 

 that they constantly infect 

 food with the bacteria they 

 carry. Further, the epidemiological evidence suggests that, when suitable 

 conditions prevail, flies may be highly important factors in the spread or 

 certain infectious diseases 



In this book an attempt has been made to collect the most important 

 and reliable information available on the subject, and to arrange it in such 

 a manner that all who are interested in its various aspects may be able to 

 ascertain the present extent of our knowledge. 



In order to meet the requirements of various classes of readers, those 

 portions of the book which are devoted to matters of general interest and 

 importance are printed in large type, and in them, as far as practicable, the 

 use of technical terms has been avoided. The details of bacteriological 

 experiments and technical descriptions ot important insects have been 

 printed in smaller type, for the convenience of medical officers, bacterio- 

 logists and entomologists." 



Photograph (side view) of an unfed 



fly (x7) 



14 



