1. The sera of 80 per cent of the rabbits intravenously inoculated with fixed amounts of heat-killed pneumococci contained agglutinins and all showed protective antibodies.

2. The sera of 60 per cent of the intraperitoneally inoculated rabbits contained agglutinins and all showed protective antibodies.

3. The sera of 33 per cent of the intramuscularly inoculated rabbits contained agglutinins and 86 per cent also showed protective antibodies.

4. None of the sera of the subcutaneously inoculated rabbits contained agglutinins although protective antibodies were present in 71 per cent.

5. Although there is a close relationship between the presence of agglutinins and protective antibodies in a given immune serum, these do not run parallel.

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