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. i8 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- 



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