218 



COLLECTED STUDIES IN IMMUNITY. 



these have been treated at 37 C. for one hour with inactive ox 

 serum), it will be found, just as in the previous case, that haemolysis 

 does not occur. 



The reason for the non-activatibility in this case differs essen- 

 tially from that in the case previously described. The chief differ- 

 ence manifests itself in the behavior of the decanted fluid medium. 

 If the centrifuging is omitted, and active horse serum is added to 

 the sensitized blood-cells without previously removing the fluid 

 medium, it will be found that solution occurs. If the centrifuging 

 is not omitted, it will be seen that the decanted fluids behave in an 

 analogous manner, for when mixed with active horse serum they 

 will dissolve native guinea-pig blood. A complete experiment is 

 reproduced in Table VII. 



TABLE VII. 



In contrast, therefore, to the behavior in the first case described 

 .by us, the amboceptor has remained in the decanted fluid, and 

 has therefore not been bound by the blood-cells, or only to a very 

 slight degree. Our attempts by means, of horse serum to activate 

 the guinea-pig blood-cells which had previously been treated at 

 C. with inactive ox serum and then centrifuged, failed as a matter 

 of course; and the result was the same when the ox serum had been 

 freed of complementoid by shaking with yeast. 



This peculiar behavior, namely, that the amboceptor by itself 

 does not unite with the cell at all, and acts only after it has com- 

 bined with the complement, is of special significance for the method 



