. Preventive medicine and hygiene. Fig. 35.—The Little House Fly {Homalomyiacanicularis 6). (Hewitt.) FLIES 253 bacteria on flies are comparatively small, while later the numbers arevery large. The places where flies live also determine largely the num-ber of bacteria they carry. The average of the 415 flies was about oneand one-quarter million bacteria. The method of the experiment wasto introduce the flies into a sterile bottle and pour into the bottle aknown quantity of sterilized water, then shake the bottle to wash thebacteria from the body of the fly. The numbers, therefore, only repre-s
. Preventive medicine and hygiene. Fig. 35.—The Little House Fly {Homalomyiacanicularis 6). (Hewitt.) FLIES 253 bacteria on flies are comparatively small, while later the numbers arevery large. The places where flies live also determine largely the num-ber of bacteria they carry. The average of the 415 flies was about oneand one-quarter million bacteria. The method of the experiment wasto introduce the flies into a sterile bottle and pour into the bottle aknown quantity of sterilized water, then shake the bottle to wash thebacteria from the body of the fly. The numbers, therefore, only repre-sent those carried on the outside and not those in the intestinal experiments of Esten and Mason were designed to simulate thenumber of microorganisms that would come from a fly in falling intomilk. Torrey ^ found that a single fly may carry from 570 to 4,400,000bacteria upon its surface, and from 16,000 to 28,000,000 in its intes-tinal tract. The prevailing types are Streptococcus equinus jecalis and. Fig. 36.—Wing of House Fly, Showing How It Carries Dust Particles. salivarius, which are also found in the breeding and feeding places ofthe house fly. Torrey also obtained three cultures of B. paratyphosuswhich is especially signiflcant. Even though flies breed in manure, and the larvae teem with bacteria,the adult winged insect, when newly hatched, contains fewer micro-organisms. This cleansing is due to the active phagocytosis which takesplace during metamorphosis from pupa to imago. The bacteria in theintestinal tract of the newly hatched imago are mostly extruded soon afteremergence from the puparium. Bacot,^ however, has shown that certain species of bacilli ingestedduring the larval period of Musca domestica can retain their existencewhile their host is undergoing the process of metamorphosis, and continuetheir existence in the gut of the adult fly, but that their number dimin-ishes suddenly after emergence. In a subsequent work Bacot ^ demon-strated that Baci
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Keywords: ., bookauthorwh, bookcentury1900, bookdecade1910, booksubjecthygiene
