50 THE HOUSE FLY— DISEASE CARRIER 



tor Cobb states that he possesses actual counts made 

 by the use of a little counter of his own invention, but 

 that he does not publish these records for fear that he 

 will be accused of sensationalism. He says that win- 

 dow-panes with from i,ooo to 10,000 fly-specks per 

 square foot are not at all uncommon, and that from 

 ten to fifty per square foot is a common number in what 

 are considered well-kept homes. And this is only in 

 places where the dirt can be readily seen. He states 

 that on neutral-tinted objects which are not cleaned so 

 frequently fly-specks occur in millions. "On wallpaper, 

 chandeliers, outside veranda posts, on cornices, ceil- 

 ings, and window blinds, the numbers are almost past 

 computation." He further shows that examination of 

 the excreta of flies captured in the open shows that 

 they contain a great variety of spores in living con- 

 dition. He finds that the digestion of the fly consists 

 simply in the absorption of those substances readily 

 soluble in its weak digestive fluids and the evacuation 

 of all others ; therefore the fly is an enormous feeder. 

 Doctor Cobb states that in a single meal it frequently 

 swallows nearly half of its own weight of food. This 

 accounts for the frequency of the fly-specks, and, con- 

 sidering the number of flies, for the enormous num- 

 ber of specks. 



Doctor Graham-Smith, elsewhere quoted, made a 

 few studies of the number of deposits left by flies. He 

 found that the rate at which the deposits are produced 

 depends upon temperature and the form of food, flies 

 being most lively in hot weather or when placed in a 



