210 COLLECTED STUDIES IN IMMUNITY. 



It is, of course, not at all necessary that such a diminution of 

 affinity occur with all complements; and, considering the great dis- 

 tribution and multiplicity of the substances included in the con- 

 cept " complement," this is a priori but little probable. We have 

 therefore hoped that in the course of our investigations we would 

 discover a suitable combination in which, on the formation of com- 

 plementoid, the diminution of affinity does not occur, or occurs only 

 to a slight degree. As a matter of fact, such a case has recently 

 presented itself to us. 



As is well known, normal dog serum dissolves guinea-pig blood 

 energetically. If this dog serum is inactivated, it is .easy to restore 

 the hsemolytic property with active guinea-pig serum; the inacti- 

 vation, however, must be effected at suitable temperatures, 50-51 C., 

 for at higher temperatures, as Sachs l has demonstrated, the ambo- 

 'jeptor of dog serum shows itself thermolabile. 



That is why Buchner in his experiments could not activate the 

 amboceptor of dogs, for at the inactivating temperature employed 

 by him, 60 C., the completion with guinea-pig serum is no longer 

 possible. Continuing the analysis of this interesting case we made 

 a curious observation: If guinea-pig blood-cells were treated with 

 appropriate amounts of inactive dog serum for one hour in an incu- 

 bator and the mixture then centrifuged, it was found that, con- 

 trary to all expectations, the sediments could no longer be activated 

 with guinea-pig serum, whereas when the three constituents w r ere 

 mixed simultaneously, prompt haemolysis occurred. (See Table I.) 



Our first thought was that the amboceptor, despite the relatively 

 long contact with the blood-cells (one hour), had perhaps not been 

 bound by these. Such behavior, to be sure, although conceivable 

 and, as we shall see later, sometimes actually occurring, would be 

 exceptional. In this case, however, we could readily convince our- 

 selves that this suspicion was groundless. For when by means of 

 guinea-pig serum we attempted to activate the guinea-pig blood- 

 cells digested with dog serum as above described, without first removing 

 the fluid medium, no haemolysis took place. And we could see by the 

 behavior of the fluid obtained by centrifuging the blood mixture as 

 described that the amboceptor was not present in the fluid. When 

 this was allowed to act on native guinea-pig blood jx> which active 

 guinea-pig serum (complement) had been added, no solution could 



1 See pages 181 et seq. 



