Findings are described which amplify those of a preceding paper in showing that bacteria increased in volume when treated with specific agglutinin. When the increase in volume approximated 20 per cent all the bacteria were agglutinated. We have attempted to correlate the volumetric increase with the quantity of protein adsorbed by the organisms during agglutination and have studied not only bacteria but collodion particles first sensitized to antigen and then agglutinated with a precipitin specific for the antigen. The increase in volume of the collodion particles was small and the quantity of protein adsorbed relatively large. When two species of bacteria were agglutinated with their respective antisera the reverse was true; the apparent volume increase was much greater than the quantity of protein deposited during the reaction. There is, then, no direct correlation between protein deposition and apparent increase in volume. Nevertheless, the results of experiments here reported have suggested an explanation for the fact of increase in volume.

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