126 SPECIFIC DISEASES 



interpretation and often covering an insufficient period is mainly 

 relied on, but in a few instances the evidence appears to be 

 conclusive. 



It is evident, therefore, that the greatest care has to be 

 exercised in criticizing and sifting the mass of evidence of 

 various kinds, which has been brought forward in favour of the 

 transmission of disease by non-biting flies, and that prolonged 

 and accurate investigations in all departments are necessary 

 before we can hope to have an accurate knowledge of the precise 

 part played by flies in disseminating various diseases. 



Flies do not seem to be affected in any way by bacteria 

 pathogenic to man. 



In the following chapters an endeavour has been made to 

 place before the reader an account of all the bacteriological 

 investigations which have been made in relation to each disease. 

 The more recent work has been quoted at sufficient length to 

 enable a judgment to be formed as to its merits. Selections 

 from the more important papers dealing with general observations 

 have also been quoted very fully. 



CHAPTER XIII 



TYPHOID OR ENTERIC FEVER AND DISEASE CAUSED 

 BY ALLIED ORGANISMS 



Though the possibility of the spread of typhoid fever infec- 

 tion by flies has been generally acknowledged for some years, 

 but few records are to be found of instances in which B. typhosus 

 has been recovered from infected flies in connection with out- 

 breaks of the disease. In spite of this fact much evidence has. 

 accumulated to show that under certain favourable conditions 

 flies are important agents in spreading the disease. Howard 

 (1911, p. xvi) has even gone so far as to propose the name 

 * typhoid-fly ' as a substitute for the name ' house-fly ' now in 

 general use, though he admits that "strictly speaking the term 



