AMBOCEPTOR, COMPLEMENT, AND ANTICOMPLEMENT. 257 



the required equivalence will already be reached with the amount of 

 complement just sufficient for solution, and an increase of the com- 

 plement action by loading the blood-cells with additional ambo- 

 ceptor will not occur. 



The conditions, however, are entirely different if the affinity of 

 the complementophile group of the anchored amboceptor for the 

 complement is only very slight; in other words, when we are dealing 

 with an easily dissociated combination in a reversible process. In 

 that case, in accordance \vith a well-known chemical law, the more 

 of one of the elements is in excess, the more of the completed combination 

 will remain intact. Hence if there are very few receptor units in the 

 blood-cells, it will be necessary to add very much complement in order 

 to diminish the amount of dissociation and to cause the formation 

 of an effective unit of hremolysin; if more receptor units are present, 

 less complement will suffice. The tables here given present numerous 

 considerations which show that little amboceptor + much complement 

 and much amboceptor + little complement lead to the formation of the 

 same amount of complemtnt-amboceptor combination (hsemolysin 

 unit) anchored by the receptors. 



A most conspicuous role, however, is played by the fact that the 

 immune serum is not a simple substance, but is made up of partial ambo- 

 ccptors to which various dominant complements of the sera correspond. 

 Of especial importance in this respect are partial amboceptors present 

 in immune serum in small amounts (and which therefore can only 

 come into action when high multiples of the immune serum are 

 employed), but which, for their completion, find a partial complement 

 which is particularly plentiful in the completing serum. Such a 

 partial amboceptor present in these small amounts (such, for example, 

 as has been demonstrated in the serum of rabbits treated with ox 

 blood) constitutes one of the main explanations for the phenomena 

 above described. 



From these considerations we see that the various phenomena 

 which -we observe in the interdependence of the amounts of ambo- 

 ceptor and complement required may have entirely different causes, 

 but that, by regarding all of the three above-mentioned factors, these 

 phenomena can be explained very naturally. Under these circum- 

 stances it is, of course, not permissible to generalize from one particular 

 case. 



