1. The intradermal inoculation of rabbits with Type I pneumococci gives rise to a local lesion and a definite sequence of other events that offer many analogies to pneumococcus lobar pneumonia, and for this reason the condition is being employed for a resurvey of the subject of pneumococcic infection.
2. This symptom-complex has been described in detail particularly as to the development of the local lesion, the temperature reaction, the bacteriemia, the white count, the persistence of organisms in the lesion, and the development of protective substances.
3. A certain number of animals recover from this condition after a definite course and by a process spoken of as crisis. The events correlated with this crisis have been described.
4. If sufficient antipneumococcic serum is given intravenously at 24 hours, prompt recovery can be brought about. The essential points of this recovery have been established.
5. Within 5 days after a single vaccination with dead pneumococci the normal rabbit develops an immunity to infection. If the rabbit is vaccinated and then infected within the period necessary for the development of this immunity the course of the consequent disease is shortened in proportion to the interval between vaccination and infection.