INFECTIOUS DISEASES OF MICE 411 



incubation period was about 48 hours. Transmission occurred via the 

 nasal passages by contact. When carriers were added to a group of 100 or 

 more mice, some died within 5 days, 50 to 70 per cent succumbed within 

 2 weeks, some contracted the disease and recovered, and others were refrac- 

 tory. Organisms were not found in the bedding, food, or feces. Intra- 

 nasal inoculation reproduced the pulmonic lesions with as few as 200 to 

 600 organisms. 



At autopsy, subserous petechial hemorrhages characteristic of septicemia 

 and bilateral pneumonia were noted. The lungs were red and moist, on 

 section contained little air, and the fluid expressed from the cut surface 

 was viscid and stringy. Pleurisy was frequently present. The micro- 

 scopic picture varied with the duration of the lesion from interstitial conges- 

 tion, hemorrhage, edema, and serous alveolar exudate in the early lesions 

 to a cellular exudate of polymorphonuclear cells filling the alveoli. A 

 fibrinous and cellular exudate covered the pleural surfaces. In general, the 

 pathology was similar to that following experimental infection of mice with 

 Friedlander's bacillus (29). 



Cultures of the nasal passages, lungs, and blood yielded a large, gram- 

 negative, capsulated bacillus which w^as morphologically and culturally 

 indistinguishable from Friedlander's bacillus {Klebsiella pneumoniae). 

 Better growth occurred at 23°C. than at 37°C. The organism, however, was 

 entirely distinct antigenically from five known types of Friedlander's bacillus. 



Infection due to an organism resembling the influenza bacillus. — Kairies 

 and Schwartzer (116) have described a sporadic and epidemic disease due to 

 an organism resembling the influenza bacillus. Sporadically ill animals 

 showed weakness, shaggy coats, adherent eyelids, frequent abscesses on the 

 head, rapid respirations, and bronchopneumonic lesions in the lungs. Dur- 

 ing the epidemic in which 2 to 4 mice of a stock of 500 died daily, diarrhea 

 was an additional feature. Leukopenia resulted from infection with the 

 organism, the leukocyte counts varying from 1200 to 4000 with a decrease 

 in lymphocytes and an increase in segmented and stab forms. Cultures of 

 the pharynx, nose, eyes, abscesses, heart's blood, and lungs of diseased mice 

 yielded a tiny gram-negative cocco-bacillus showing bipolar staining in 

 young cultures but involution and thread forms in old cultures. Approxi- 

 mately 35 to 40 per cent of healthy animals were found by culture to harbor 

 the bacillus. Occasionally a hemolytic streptococcus was recovered with 

 the cocco-bacillary organisms from all parts of the body; rarely the strep- 

 tococcus alone was found in the respiratory tract. Although not strongly 

 hemoglobinophilic, the bacillus morphologically and culturally was almost 



