Evidence is presented that the etiology of infectious murine catarrh is specifically referable to the coccobacilliform bodies. The disease was regularly produced in normal mice by the nasal instillation of primary tissue cultures. In the presence of the X bacillus, transfers of primary cultures were usually uninfective. Pure cultures, however, retained their pathogenicity through as many as 12 transfers.
The onset and progress of the experimental disease were somewhat retarded in comparison with the natural disease, but in general there was a close parallel. Mice injected with cultures did, however, show a significant decrease in the incidence of rhinitis. Transmission by direct contact was demonstrated in the presence of a rhinitis but not in its absence.