412 BIOLOGY OF THE LABORATORY MOUSE 



impossible to distinguish from Pfeiffer's bacillus and the name ''Bacterium 

 influenzae murium'''' was accordingly proposed. Certain aspects of the 

 spontaneous illness, as well as the hemorrhagic exudation produced by 

 experimental inoculation, resemble mouse pasteurellosis (hemorrhagic 

 septicemia), from which it should be differentiated. In view of the fact 

 that some cultures in liquid media contained tiny bodies passing a membrane 

 with a pore diameter of 400 to 600 m^l, a relationship may exist between 

 these forms and the pleuropneumonia-like organisms or the cocco-bacilli- 

 form bodies of infectious catarrh of mice (178). 



Spontaneous pneumonia due to the pneumococcus has not been reported, 

 although the isolation of this organism from mice has been claimed (194). 

 A partial explanation may be found in experimental attempts to produce 

 pneumonic lesions. Following inhalation of virulent Type I pneumococci, 

 which killed rapidly by other routes of inoculation, the organisms were 

 found in the lungs only up to 3 hours after administration (256). Pneu- 

 monia did not result unless the animals were partially immune (258, 259) 

 nor did systemic infection follow (139, 256) unless the animals were intoxi- 

 cated with alcohol (257). Experimental pneumonia readily occurred 

 following inhalation of virulent hemolytic streptococci and Friedlander's 

 bacillus (256, 29). Later work, however, has demonstrated that certain 

 strains of pneumococci, inoculated intranasally, produced in some mice a 

 fatal respiratory and general infection with septicemia, pneumonia, pleurisy, 

 empyema, pericarditis, and cervical lymphadenitis (325). By balancing the 

 virulence of the organism and the resistance of the mice, it was possible to 

 produce pneumonia with a consistency which permitted study of the pathol- 

 ogy and pathogenesis of the infection (213, 214). 



Cultures of the lungs of normal mice (112) have yielded organisms of the 

 streptothrix type {Streptobacillus), B. subtilis, and various kinds of cocci. 

 Similar organisms were found in the dust from hay and straw, and by with- 

 holding such substances the number of contaminating organisms was 

 reduced. These bacteria were non-pathogenic when injected subcuta- 

 neously, however, and probably are of little importance in the production 

 of disease. 



Control measures to be undertaken in the event of an outbreak of 

 respiratory infection are simply those of isolation and the usual precau- 

 tionary procedures to prevent spread. In an unusually valuable stock, 

 chemotherapy with one of the sulfonamide drugs (sulfanilamide, sulfa- 

 pyridine, or sulfathiazole) might be attempted, although no information is 

 available regarding the efhcacy of any of them in these infections. 



