The House-fly as a Carrier of Disease 
155 
Tuberculosis is one of the diseases which it is quite conceivable 
may be carried occasionally. The spurirm of tubercular patients 
is very attractive to flies, and various workers, notably Graham- 
Smith, have found that Musca domestica may distribute the bacillus 
for several days after feeding on infected material. 
A type of purulent opthalmia which is very prevalent in Egypt 
is often said to be carried by flies. Nuttall and Jepson (1909) 
consider that the evidence regarding the spread of this disease by 
flies is conclusive and that the possibility of gonorrhoeal secretions 
being likewise conveyed cannot be denied. 
Many studies have been published, showing a marked agreement 
between the occurrence of typhoid and other intestinal diseases 
and the prevalence of house-flies. The most clear-cut of these are 
the studies of the Army Commission appointed to investigate the 
cause of epidemics of enteric fever in the volunteer camps in the 
Southern United States during the Spanish-American War. Though 
their findings as presented by Vaughan (1909), have been quoted 
very many times, they are so germane to our discussion that they 
will bear repetition: 
“Flies swarmed over infected fecal matter in the pits and fed 
upon the food prepared for the soldiers in the mess tents. In some 
instances where lime had recently been sprinkled over the contents 
of the pits, flies with their feet whitened with lime were seen walking 
over the food.” Under such conditions it is no wonder that “These 
pests had inflicted greater loss upon American soldiers than the arms 
of Spain.” 
Similar conditions prevailed in South Africa during the Boer War. 
Seamon believes that very much of the success of the Japanese in 
their fight against Russia was due to the rigid precautions taken to 
prevent the spread of disease by these insects and other means. 
Veeder has pointed out that the characteristics of a typical fly- 
borne epidemic of typhoid are that it occurs in little neighborhood 
epidemics, extending by short leaps from house to house, without 
regard to water supply or anything else in common. It tends to 
follow the direction of prevailing winds (cf. the conclusions of Hindle 
and Merriman). It occurs during warm weather. Of course, when 
the epidemic is once well under way, other factors enter into its spread. 
In general, flies may be said to be the chief agency in the spread of 
typhoid in villages and camps. In cities with modern sewer systems 
they are less important, though even under the best of such condi- 
