Inhibition of hemolysis by plasma has been studied in systems containing saponin, digitonin, and sodium lauryl sulfate, using the methods developed for the study of the kinetics of progressive reactions. The results are that the progressive nature of the hemolytic reaction in saponin systems becomes less when the inhibitor is added, that the addition of inhibitor to digitonin systems has no effect on the final result although the velocity of the progressive reaction is reduced, and that the effect of plasma in lauryl sulfate systems is intermediate between the effects in saponin systems and digitonin systems. A simple explanation is that the lysin is very strongly fixed, to form an internal phase, to the cell surfaces in digitonin systems, less strongly in laurate systems, and still less strongly in saponin systems.

To answer the question as to whether, in a system in which some of the lysin forms as internal phase, the addition of an inhibitor results in a redistribution of the lysin between the internal phase and the bulk phase, sodium lauryl sulfate-S35 and sodium cetyl sulfate-S35 were prepared, and their distribution between the internal phase and the bulk phase was measured before and after the addition of plasma, the lysins being added to the cells either before or after the addition of the inhibitor. The results show that there is a large uptake of these lysins at the red cell surfaces when they are added first, and that the subsequent addition of plasma greatly reduces the quantity of lysin held in the internal phase. Further, if the inhibitor is added first and the lysin subsequently, the internal lysin phase is very incompletely formed.

Serum albumin, used in place of plasma, gives essentially similar results.

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