THE PRODUCTION OF PURPURA BY DERIVATIVES OF PNEUMOCOCCUS : III. FURTHER STUDIES ON THE NATURE OF THE PURPURA-PRODUCING PRINCIPLE.

1. The purpura-producing principle of Pneumococcus is non-antigenic in the sense that it does not stimulate the formation of antibodies. 2. White mice acquire an increased resistance to purpura as a result of repeated injections of toxic doses of the purpura substance. 3. The serum of rabbits immunized with the purified purpura principle, with "S" and "R" strains of Pneumococcus or with cell extracts, autolysates or the nucleoprotein fraction of the organism does not confer upon white mice protection against purpura. 4. The purpura principle does not exist preformed in the cell, but is rather an autolytic derivative; since it is formed only when pneumococci undergo autolysis, and it is not found when the autolytic ferments are inactivated. 5. The purpura substance is associated with the proteose fraction of active pneumococcus extracts.