A bacillus was found associated in pure culture with an extensive lobar bronchopneumonia in calves. It occurs in the exudate as a minute bacillus in small groups. In cultures it appears in three forms: as a bacillus, as a coccus-like endospore or arthrospore, and as a conglomerate Actinomyces-like flake or colony with peripheral clubs. The bacillar and coccoid forms occur on agar, the Actinomyces form in the condensation water of coagulated serum (horse). The coccoid form is probably a spore state, the minute refringent spore being contained in a roundish, unstainable mass representing either the remnants of bacillar substance or some capsular material. The somewhat striking similarities between this organism and Actinomyces are expressed by the massed growth with terminal clubs, the bacillar and coccoid stages, all of which are characteristic of Actinomyces.

Sealing the tubes is essential for multiplication. Cultures must be renewed within a few days, otherwise multiplication fails. The substance which forms the bulk of the radiate flocculi is probably of capsular nature, greatly overproduced in serum tubes and scarce or absent on agar. Its nature is unknown.

The organism is not appreciably pathogenic when injected into certain small laboratory animals.

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