Introduction, Reversibility of reaction between antibodies, Velocity of reaction. Homogeneous systems, Velocity of reaction. Homogeneous systems, Velocity of reaction. Homogeneous systems, Velocity of reaction. Heterogeneous systems, Equilibria in absorption processes, Neutralisation of the Haemolytic properties of bases and of lysins of bacterial origin, Neutralisation of Diphtheria-toxin, Ricin, saponin, and snake venoms, The compound haemolysins, The precipitins and their antibodies,