A previous paper (1) dealing with the effects of homologous type-specific polysaccharide on the agglutination and capsular swelling of sensitized pneumococci III has shown that both agglutination and capsular swelling are reversed when suitable amounts of carbohydrate are used. The reversal of these two reactions was interpreted as being due to dissociation and redistribution of the specific antibody. With the reagents and technic used at that time, it was not possible to demonstrate that any amount of carbohydrate caused increased aggregation of pneumococci sensitized in the inhibition-zone of antibody-excess and washed free of uncombined antibody. This was contrary to expectations in view of the findings of Heidelberger and Kabat (2).
By use of a higher-titered serum and by modifying the earlier technic, it has now become possible to demonstrate increased aggregation of sensitized washed pneumococci exposed to certain concentrations of the homologus polysaccharide.