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 1,000 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 
