Abstract
A bacillus of the paratypnoid-enteritidis group associated with epizootics among laboratory mice has been identified with Bacillus festis caviæ Smith which produces similar affections in guinea pigs and has been very closely related to the type "mutton" aertrycke strain of Schütze. This identification is based upon the cultural reactions of the organism, direct and cross-agglutinations, and similar absorptive capacities of the unknown and type strains.