The Source of the Microorganisms in the Lungs of Normal Animals

It has been possible to show that the lungs of such animals as the calf, rabbit, guinea pig, white rat, and white mouse are readily invaded by organisms. The most frequent types observed in cultures from the border of the lungs have been streptothrix, molds, and bacteria of the Bacillus subtilis group. These forms originate in certain dry food stuffs (hay and straw). By withholding or moistening these materials it has been possible to diminish the number of organisms in the lungs. When these materials have been supplied to mice whose lungs under usual conditions contain only a few organisms, the number of positive cultures increases and is comparable with those of the larger animals. The bronchial lymph glands of all guinea pigs examined developed, in 66(2/3) per cent of the tubes, organisms similar to those obtained from the lungs.