1. About two-thirds of the rabbits injected intracutaneously with suspensions of heat-killed S or R pneumococci develop an increased eye reactivity.
2. Eye reactions in these animals may be elicited by the instillation of "nucleoprotein," or of a solution of Pneumococcus from which the acid precipitable and heat coagulable proteins have been removed. The eye reactions are not elicited, under the conditions described, by living R cells or the protein-free, type-specific, polysaccharides.
3. Rabbits do not develop an increased eye reactivity following intravenous injections of the intact cell.
4. Rabbits do not develop an increased eye reactivity following injections of soluble derivatives of Pneumococcus.
5. Experimental infection by Pneumococcus may stimulate eye reactivity in rabbits.
6. Eye reactivity occurs in animals actively resistant to infection.
7. Eye reactions are observed more frequently in rabbits which show the secondary reaction.