STUDIES ON THE SENSITIZING PROPERTIES OF THE BACTERIOPHAGE.

1. Marked specific contractions of the uterine horns of guinea pigs, actively sensitized, to phage-lysed Flexner bacilli or to colon bacilli, lysed by the same bacteriophage, occurred on testing either series for anaphylaxis with the homologous phage lysates. These reactions, however, were not due to an antigenic function of the bacteriophage itself, because no reaction whatsoever occurred when the same bacteriophage, propagated on the heterologous organisms, was substituted in the anaphylactic test. 2. Specific uterine reactions of marked intensity were obtained in guinea pigs, actively sensitized to intact or autolyzed Flexner or colon bacilli, respectively, by testing either series for anaphylaxis with homologous, phage-free bacterial antigens. 3. No reaction occurred by testing the uterine strips of animals, sensitized to intact or autolyzed bacilli (either Flexner or coli), for anaphylaxis with homologous phage lysates and, vice versa, there was no contraction of uterine strips sensitized to phage lysates upon contact with homologous bacterial autolysates. 4. The observations made in this paper suggest that a new and immunologically distinct antigenic complex arises from the bacterial protein after lysis of the organisms by the bacteriophage.