Ten strains isolated from cows are described. They are similar in morphology, in most cultural reactions, and in pathogenicity for rabbits, with the exception of 1 strain. When compared serologically by agglutination reactions, certain differences were readily apparent, since immune sera prepared with 4 strains allowed varying degrees of cross agglutination and apparently no cross absorption of specific agglutinins. Each immunizing strain apparently produces specific agglutinins, since they are not absorbed by any other culture. Also, a strain may stimulate production of distinct heterologous agglutinins. The fluffy type of colonies usually found by other workers was not observed in these cultures.