A Formulation of the Serological Flocculation Rate in the Region of Considerable Antibody Excess B~¢ Sanford B. Hooker Ai~o

Some antigen-antibody reactions as they are observed in the testtube may be divided, for convenience of study, into two phases: (i) combination, and (2) the secondary aggregation which results in flocculation or agglutination. When strong concentrations of the reactants are mixed--potent hemagglutinin or precipitin and its homologous antigen--the second phase becomes immediately visible and obviously the necessarily precedent phase, combination, must have been almost instantaneous. This rapid combination cannot be explored by current immunological technic, but the second phase is susceptible of rather accurate quantitative study if suitable dilutions are used. The Ramon (constant antigen) and the Dean and Webb (constant antibody) titrations exemplify practical uses of measuring the velocity of reaction. In a study of several simple precipitin-antigen systems we have observed that in regions of considerable antibody excess the times of flocculation are a linear function of the dilutions of antigen; i.e., they vary inversely and in the same ratio as the change in the concentration of antigen. Similar but less regular results are recorded in several recent papers (I, 2, 7); these, however, deal mostly with complex antigens--bacteria, plasma, egg white and because of the systems' complexity many observations are di~cult or impossible to interpret with confidence. Duncan (I) records one example of linearity obtained with a polysaccharide hapten from a species of Mycotor~a, but he comments only on the time of optimal flocculation as influenced 373