VI. A Serological Study of the Bacillus of Pfeiffer

Confirming the previous work of Valentine and Cooper, a study of eighteen cultures of the bacillus of Pfeiffer isolated from cases of influenza in different localities and at different times revealed identities in the cultures only when a probability of personal contact existed. On the basis of Park's argument these findings admit of only one conclusion with regard to the rôle of Pfeiffer's bacillus; namely, that that microörganism is not the cause of the disease. An immune serum prepared by the injection of one strain of B. influenzae was found to agglutinate other strains of that bacillus, but not the one used for the immunization. This phenomenon was due to the presence of an unusual quantity of a specific inhibiting antibody.