During the month of November there occurred an outbreak of pneumonia among the calves in a large dairy. Thirty-two calves in one barn were exposed to the disease. Ten clinical cases developed. Two died of diffuse pneumonia. From these bovisepticus Group I organisms were obtained at autopsy. Four affected with pneumonia and eight other calves which failed to show symptoms of pneumonia developed a purulent rhinitis. From the nasal exudate of these cases Group I organisms were cultivated. The characteristic rhinitis was reproduced experimentally by brushing the nasal mucosa with a swab dipped in culture. Certain of the calves which suffered from the spontaneous rhinitis continued to carry the organisms in the nasal passages for periods as long as 121 days.
After the first outbreak had subsided practically all calves introduced into this barn developed a milder type of rhinitis associated with organisms of Group II bovisepticus. 25 per cent of such calves continued to carry the organism on the nasal mucosa for periods of 50 to 73 days. It was possible to induce nasal infection in calves with pure cultures of this organism.