CARRIAGE OF DISEASE 
161 
winds are unfavorable to the spread of diarrhea and to 
the active migration of flies alike. Loose soil and fis¬ 
sured rock, containing organic filth in its crevices, favor 
the spread of diarrhea and the breeding of flies, whilst 
solid rock is unfavorable to both.’ (See also News- 
holme, 1906, p. 145.) 
“Hamer (1908), who has studied the relation of fly- 
prevalence ( Mnsca, Homalomyia ) to diarrhea from an 
epidemiological point of view, appears to be somewhat 
sceptical as to flies being active agents in the spread of 
infection. He considers that the increase in flies and 
diarrhea may be due simply to a coincidence. 
“Ainsworth (1909, p. 498) has studied the relation 
of infantile diarrhea to flies in Poona and Kirkee, India, 
and illustrates the relation by means of a yearly curve 
which is very striking as affording evidence that flies 
stand in causal relationship to diarrhea. 
“All authorities agree that flies rest under strong 
suspicion of serving as disseminators of diarrheal in¬ 
fection.” 
Jackson (1907) gives the results of numerous ob¬ 
servations upon the relation of flies to intestinal dis¬ 
eases (including infant diarrhea) and the relation of 
deaths from intestinal diseases in New York City to 
the activity and prevalence of the common house fly 
is indicated not only by repeated observations but also 
by an interesting plotting of the curve of abundance 
of flies in comparison with the plotted curve of the 
abundance of deaths from intestinal diseases, indicat¬ 
ing that the greatest number of flies occurred in the 
