INFECTIOUS DISEASES OF MICE 449 



solidation were present in the apices or dorsal portions of the lung. The 

 consolidation spread as the disease progressed and at death the entire lung 

 might be involved, often having a uniform dark red or plum-colored appear- 

 ance resembling the lesions due to the influenza virus (262). The micro- 

 scopic picture was one of a patchy interstitial pneumonia, with mononuclear 

 inhltration and varying degrees of hemorrhage and edema. Cellular 

 exudate in the bronchial lumina consisted of mononuclear and polymorpho- 

 nuclear leukocytes. The epithelium of the bronchi was well preserved in 

 contradistinction to the necrosis and desquamation produced by the 

 influenza virus. Non-inflammatory focal necrosis was present in the liver. 

 A variety of organisms were cultured from the lungs in some instances, but 

 none reproduced the disease. 



The virus was present in the lung and in the liver (89) of infected mice, 

 and passed Berkefeld N and V as well as Seitz filters. Mice were susceptible 

 only to intranasal inoculation. No spread occurred by contact. In ferrets, 

 administration of virus by the nasal route produced an elevation of tempera- 

 ture to about io5°F., occasionally associated with respiratory difficulty. 

 Intratracheal inoculation of rabbits resulted in pneumonia, mediastinitis, 

 and pericarditis, complicated, however, by the presence of secondary 

 bacteria (54). The guinea pig was resistant. Protective serum was not 

 produced in rabbits by administration of lung emulsions containing the 

 virus, nor was active immunization of mice successful. The agent is 

 apparently distinct from human influenzal virus, since mice convalescent 

 from infection with the latter were fully susceptible to the murine virus. 

 Further immunological studies are necessary, however, to achieve certain 

 dift"erentiation and identification of this agent. 



Pneumonia described by Horsfall and Hahn (103, 104). — As already 

 pointed out, this t>^e of experimental pneumonia differs in certain impor- 

 tant respects from that described in the preceding paragraphs. The disease 

 was found to be latent in 3 of 8 different colonies of albino Swiss mice. 

 Using 3 to 4-week-old animals, infection became apparent after 2 to 7 intra- 

 nasal passages of the supernatant fluid from lung emulsion at an interval of 

 7 to 9 days, but not by rapid serial passage at 4 to 5 day intervals. The 

 mice appeared well for 5 to 7 days, but then showed a decrease in activity 

 and food consumption, loss of weight, ruiitled fur. slow, deep, and sometimes 

 labored respirations, and often cyanosis of the ears and tail. Death occurred 

 from 8 to 14 days after inoculation. The morbidity and mortality rates 

 varied with the amount of virus inoculated and the particular stock of mice 

 employed. 



