All outbreak of pneumonia in dairy cows attributed to Bacillus bovisepticus is described. About twenty cows and two calves were affected. The first cases were noted in cows purchased in Michigan. The disease next appeared in another lot of cows from Pennsylvania and subsequently attacked native stock. Of the ten cases which came under our observation, five apparently recovered, two died, and two severely affected cows were killed. The other case developed multiple abscesses of the lung and was finally killed.

The more characteristic symptoms observed were high temperature, rapid respiration, dyspnea, cough, dullness on percussion, bronchial breathing, and albuminuria.

The pneumonia was diffuse but first affected the cephalic and more dependent lobes. The process varied from hyperemia and hemorrhage to exudation of fibrin and leucocytes within the air spaces. The plugging of the interlobular lymph channels and blood vessels with fibrin was frequent.

Bacillus bovisepticus was isolated in pure cultures from all involved portions of lung at autopsy. It was not found in blood cultures during the height of the disease, nor could it be obtained from the spleen and kidney after death.

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