102 THE HOUSE FLY—DISEASE CARRIER 
eighteenth centuries have referred to this possibility, 
and our own Leidy, in 1871, said that he believed 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 
