CARRIAGE OF DISEASE 
109 
stayed in the pig-pen vicinity, there would be less ob¬ 
jection to the flies and the kinds of organisms they 
carry, but the fly is a migratory insect and it visits 
everything ‘under the sun.’ It is almost impossible to 
keep it out of our kitchens, dining-rooms, cow stables, 
and milk rooms. The only remedy for this rather 
serious condition of things is, remove the pig-pen as 
far as possible from the dairy and dwelling house. Ex¬ 
treme care should be taken in keeping flies out of the 
cow stables, milk rooms and dwellings. Flies walking 
over our food are the cause of one of the worst con¬ 
taminations that could occur from the standpoint of 
cleanliness and the danger of distributing disease 
germs.” 
A great deal of work of this general nature in re¬ 
gard to the carriage of micro-organisms by flies with¬ 
out specific reference as to the character of the organ¬ 
isms has been done and the results have been published 
here and there. The illustration shown at Fig. 18 is 
an early one made from a photograph taken by Wil¬ 
liam Lyman Underwood of a gelatin plate over which a 
fly, captured by chance in a room, was allowed to walk. 
On each spot which the fly’s feet touched there grew a 
colony of bacteria. 
Cobb (1906) studied the spores of a sugar cane fun¬ 
gus left by the feet of a fly which had been feeding 
upon the fungus on the sides of a glass vessel. The 
spores from five of the tracks on the glass were cal¬ 
culated and the number per track was found to be 
860,000. A second calculation gave 700,000 per foot- 
