Abstract
In the experimental disease brought about by infecting rabbits intradermally with Type I Pneumococcus the use of relatively small or subeffective amounts of specific antipneumococcus serum leads to the survival of some individuals and the death of others. It has been shown that both the severity of the infection and the white blood cell count are factors in the determination of the outcome of the disease but that there remain other host factors which have to do with the utilization or functioning of the specific antisera.