This paper reports inter-reactions of anaphylaxis and precipitation between antigens and antisera derived from the Type II variety of pneumococcus and from one variety of yeast. That the reactions occurred only with Type II and not with Types I and III is proof that the pneumococcus antigen responsible for the anaphylaxis of the antiyeast sensitized animals was the type-specific carbohydrate (S).

Pronounced differences in respect to reactivity with the pneumococcus antigen were found between individual antiyeast sera that were of equal potency in respect to reactivity with the yeast antigen. This fact emphasizes the desirability of the use of antisera from a large number of individual animals in the study of microbial inter-relationships.

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