102 THE HOUSE FLY— DISEASE CARRIER 



eighteenth centuries have referred to this possibility, 

 and our own Leidy, in 1871, said that he beheved that 

 house flies were responsible for the spread of hospital 

 gangrene during the Civil War. In that same year 

 (1871) Lord Avebury (then Sir John Lubbock), in 

 an article in the London Lancet, mentioned the fact 

 that flies alight on decomposing matter and carry se- 

 cretions with them. He uses this significant sentence : 

 "Far from looking upon them as dipterous angels danc- 

 ing attendance on Hygeia, regard them rather in the 

 light of winged sponges spreading hither and thither 

 to carry out the foul behests of Contagion." 



Exact Experiments 



There was, for a long time, no experimental proof of 

 such carriage. There have been outbreaks of disease 

 and single cases of disease where the carriage of the 

 causative organism by house flies seemed to be the best 

 •explanation. Actual experimental proof satisfactory to 

 the laboratory worker, however, has been of recent ac- 

 quirement, and it will be well before entering upon the 

 subject of specific diseases to mention some of this work. 



One of the latest and one of the most careful series 

 of laboratory observations has been made by Doctor 

 Graham-Smith (1910). His experiments covered a 

 wide range and seem to have been carried out with the 

 utmost pains. The most satisfactory method of con- 

 veying his results is to give his conclusions in his own 

 words : 



"Infection experiments show that non-spore-bearing 



