STUDIES ON AXTIAMBOCEPTORS. 663 



inhibition of haemolysis at the end of half an hour is less marked in the latter. 

 One would have expected the contrary to be the case, or the presence of pre- 

 cipitable substance in series A furnishes conditions favorable to the formation 

 of a precipitate. It must not be forgotten, however, that the mixtures in 

 series A also contain free normal amboceptors (eliminated in series B) and 

 these may be able to diminish the antiamboceptor action. This is all the 

 more likely since these amboceptors are free in solution and therefore more 

 readily able to react with the antlamboceptors than are the specific am- 

 boceptors already bound to the cell. 



At the end of two hours, on the other hand, we find that the antiambo- 

 ceptor action is more marked in series A than in series B. On the basis of 

 the above assumption, this might be due to the fact that the precipitate 

 produced by the large quantities of antiserum is, in a way, a deflector of 

 complement, since it robs the complement of its tendency to break up the 

 amboceptor-antiamboceptor combination. Under the conditions obtaining, 

 the complement-binding power of the precipitate is too small to prevent the 

 complement uniting with the free complementophile group of the amboceptor, 

 but is large enough to restrain it when the complementophile group is already 

 occupied by the antiamboceptor. Precipitate and antiamboceptor would thus 

 at times mutually support each other in their action. 



To what extent such a combined action really occurs must be 

 left to future investigations. In any case, we believe it important 

 to bear this possibility in mind, in order to gain a clear idea of all 

 the conditions which may play a part in the action of anti- 

 amboceptors. 



Each of the two factors (precipitate and antiamboceptor) will 

 surely also be able to exert an antihamolytic effect by itself. The 

 independent action of the antiamboceptor is demonstrated further 

 by the fact that it persists even when the complement is increased 

 several times. If the inhibition were due only to precipitates, we 

 should expect that it would be overcome by an excess of complement, 

 since the precipitate acts only as an anticomplement. On the con- 

 trary, it can be shown that the inhibition produced by the anti- 

 amboceptor persists even when the dose of complement is consider- 

 ably increased. It might be thought that a precipitate present at the 

 same time binds all the complement added, but this is not the case. 

 It is possible to demonstrate the presence of sufficient free complement 

 by separating the fluid from the undissolved blood-cells, and allowing 

 it to act on native, sensitized blood-cells. This fact agrees with 

 Bordet's observation, that the antiamboceptor robs sensitized blood- 

 cells of the power to bind complement. When we employed a 

 very small quantity of complement, just sufficient to produce com- 



