The effect of variations in the cell content of hœmolytic systems

Several years ago, in order to explain the fact that the quantity of lysin apparently used up in producing complete lysis does not increase as much as might be expected when the number of red cells in the system is increased, I introduced the idea of a localised action of the lysin at the red cell surfaces, only those molecules of lysin near the cell surface, and contained within a hypothetical “zone of action” surrounding the cell, being supposed to take part in the haemolytic process (1). A later investigation (2) brought out the interesting fact that the volume of the zone of action is approximately proportional to the resistance of the particular type of cell studied,e.g ., the zone surrounding each cell in a system containing saponin and sheep cells is about five times as large as in a system containing the same lysin and rabbit cells, the resistance of which is only about one-fifth of that of the cells of the sheep. The methods used to test the validity of the hypothesis were, however, much less satisfactory than those at present available. I feel, accordingly, that the effect of varying the cell content of haemolytic systems should be investigated afresh particularly for two reasons : (a) that haemolytic reactions are now believed to be of an order higher than the first, whereas my earlier analysis treated them as reactions of the first order, and (6) that my earlier experiments covered a smaller range of cell concentrations than is desirable.