660 COLLECTED STUDIES IN IMMUNITY. 



In series A we see deflection of complement very well marked; 

 in series B, in which complement was added last, the deflection is 

 considerably lessened, and when the additions are made in accord- 

 ance with the technique of the antiamboceptor experiment, we find 

 that there is no deflection whatever. In this experiment, as already 

 explained, we made use of an antiserum having strong precipitating 

 and deflecting power. The result confirms our contention that 

 the inhibiting action observed in our previous experiments is not 

 due to the formation of a precipitate, but is caused solely by anti- 

 amboceptors. 



Even when present, the precipitates are unable to exert a deflec- 

 tion on the complement provided blood-cells laden with amboceptor 

 .are present at the same time, so that the complement subsequently 

 introduced has the alternative of combining with precipitate or with 

 the prepared blood-cells. At the same time we must call attention 

 to a possibility which makes it likely that an intensification of the 

 power of the precipitate occurs in connection with the antiamboceptor 

 action. Conditions might exist under which the complement would 

 replace the antiamboceptor already bound to the amboceptor, were 

 not the precipitate present at the same time. It is possible that 

 this explains the varying results obtained in attempts to definitely 

 replace with antiamboceptor the normal amboceptor already anchored 

 to the cell, and freed from normal serum constituents. 1 It is con- 



1 Ehrlich and Sachs (I.e.) called attention to a paradoxical phenomenon, 

 which consisted in the fact that the sensitized blood-cells were protected only 

 by small doses of the antiserum, while an excess of antiserum did not inhibit 

 haemolysis. They found, however, that the antiha3molytic effect was produced 

 even with an excess of antiserum, provided a small quantity of normal serum 

 homologous to the amboceptor was added. Moreschi (I.e.) interprets this 

 as indicating an anticomplementary action due to the formation of a pre- 

 cipitate. In opposition to this, it may be remarked that under analogous 

 conditions the formation of a precipitate does not lead to a deflection of com- 

 plement. The peculiarity of the phenomenon described by Ehrlich and Sachs 

 consists not alone in the fact that the antiserum acts only after the addition 

 of normal serum. The striking thing is that an excess should cause the anti- 

 serum to lose its inhibiting property. In this the presence and coaction of 

 normal serum constituents (precipitable substances) are entirely out of the 

 question. Hence, while at first sight Moreschi's explanation appears very 

 apt, we see that it is insufficient to throw light on the entire group of facts 

 presented by Ehrlich and Sachs. For the present it will be difficult to get 

 along without accepting the possibility suggested by those authors, namely, 



