VARIATION AND TYPE SPECIFICITY IN THE BACTERIAL SPECIES HEMOPHILUS INFLUENZAE

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Abstract
During the course of a study of different strains of influenza bacilli, fifteen strains have been found to form colonies of a different appearance from that usually considered typical of influenza bacilli. These colonies are smooth, more opaque, and are iridescent in oblique transmitted light. Most of these strains were isolated from patients in whom these organisms seemed to play a pathogenic rô1e. When these strains were grown repeatedly on blood agar, other colonies appeared which were smaller, less smooth, less opaque, and not iridescent, and when subcultures were made from these rough colonies, all of the colonies were of this character. Further study of the cultures obtained from these smooth and rough colonies have shown that one is a variant of the other. The strain from the smooth colony has been called an S strain, that from the rough colony an R strain. Certain differences in the morphology of the organisms in the R and S strains have been observed. Of special importance is the fact that the bacteria of the S strains are possessed of capsules. It has also been found that the S strains are somewhat more virulent for laboratory animals than are the R strains.

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