These observations have brought out three facts which may be stated briefly as follows.
1. An acute respiratory epidemic was incited by mucoid strains of Bact. lepisepticum of moderate and uniform virulence.
2. The epidemic was brought about not by an alteration in the virulence of the prevailing strains of Bact. lepisepticum but by a sudden distribution of virulent organisms among a susceptible population hitherto unexposed.
3. Individuals in this population showed different degrees of resistance to the infecting bacillus; some died from pneumonia and septicemia, while others localized the infection to the nasal passages.
The significance of these facts has been discussed at length elsewhere (4).