A QUANTITATIVE THEORY OF THE PRECIPITIN REACTION : III. THE REACTION BETWEEN CRYSTALLINE EGG ALBUMIN AND ITS HOMOLOGOUS ANTIBODY.

1. A quantitative theory of the precipitin reaction based on the laws of classical chemistry has now been found applicable to the crystalline egg albumin-antibody system. Equations derived from the theory permit the calculation of the behavior of an anti-egg albumin serum over most of the reaction range after a few quantitative analyses have been made for the nitrogen precipitated. Data of other workers also conform to the proposed equations. 2. The empirical relation, shown to have advantages in the dye antidye system, may also be used for the Ea-A reaction. 3. Serum from the same animal after successive courses exhibits progressive changes which have been described graphically and quantitatively. These changes are believed to consist in the formation of more and more antibody capable of reacting with a larger number of chemically different groupings in the antigen molecule. 4. Evidence is presented that anti-egg albumin is not homogeneous, and that even after prolonged immunization the antiserum contains much low-grade antibody, incapable of forming precipitates unless more reactive precipitin is present. 5. Factors affecting the equivalence point ratio are discussed.