1. Extensive acute, fibrinopurulent meningitis may be produced in dogs by the intracisternal injection of virulent Type I pneumococci.
2. Given an equal number of virulent infecting organisms, the rate of establishment of infection depends upon the phase of growth and the quantitative growth per cc. of culture plus an uncontrollable individual factor in the animal.
3. The pathology of pneumococcal meningitis is discussed. It resembles very closely the similar disease in man.
4. Systematic lavage and treatment with optochin-serum mixtures by the method of quadruple puncture, as described above, have resulted in cures of Type I pneumococcal meningitis in dogs.
5. The important factor in obtaining cures is to bring all regions of the meninges into frequent contact with the therapeutic agent.
6. In the absence of such contact, incomplete sterilization results and "reinfection" is almost inevitable.
7. Protocols show the necessity of repeated negative cisternal fluids, both on smear and on culture, before sterilization can be assured.
8. Recovered dogs subjected to meningeal reinfection show some degree of resistance.