Pathology of Experimental Pneumococcus Pneumonia in Mice. by Arnold

In preceding papers (1) it has been shown that virulent pneumococci generally disappear from the lungs of normal mice within a few hours after inhalation and do not give rise to generalized infection. In alcohol-intoxicated mice, however, pneumococci persist in the lungs for a longer period and a fatal septicemia frequently follows. I t has further been shown (2) that a high degree of immunity is produced in mice following repeated inhalations of live pneumococci and that a less marked immunity results from exposure to a spray of dead organisms. In the instances in which non-immune mice succumb as the result of infection following a pneumococcus spraying while alcoholized, death is due to general septicemia and there is no evidence of localized infection in the lung. However, mice which have been rendered partially immune by inhalation of live or killed pneumococci and are later alcoholized and exposed to virulent pneumococci show definite evidence of localized pulmonary infection. In the present paper we shall report upon (1) the normal histology and the pathological lesions which have been encountered in routine examinations of the lungs of a large series of stock mice; (2) the effect of alcohol on the lungs of normal mice together with the changes brought about by the inhalation of pneumococci; and finally (3), the pathological lesions produced in the lungs of normal and immunized mice sprayed with pneumococci while under the influence of alcohol.