IMMUNITY. 



233 



With the explanation given above of the nature of ambocep- 

 tors and complements, the phenomena which take place in im- 

 mune serum become more or less satisfactorily explicable. By 

 means of the characteristics ascribed to these bodies it is pos- 

 sible to account for the peculiar behavior of immune serum 

 when it is diluted. This peculiar behavior 'consists in the 

 fact that such serum is frequently more potent when diluted 

 than when it is undiluted. 



Neisser and Wechsberg were the first to offer a theoretical 

 explanation of this phenomenon, and they very appropriately 

 call their explanation the theory of the diversion of complement. 



Fig. 57. — Diversion of complement in undiluted immune serum. 



As the name implies, they attribute the lack of bacteriolysis 

 in the undiluted immune serum to the turning aside of the 

 complement from the bacteria, or rather from the amboceptors 

 which are attached to the bacteria. They hold that this 

 diversion is brought about by the free amboceptors them- 

 selves. In other words, where there are more amboceptors 

 than there are complements present in a serum, a part of 

 these attach themselves to the bacteria and a part to the 

 complements. 



The accompanying diagram (Fig. 57), taken from Neisser 

 and Wechsberg, and modified to suit the present description, 

 shows two amboceptors, a, attached to bacteria, b, and four 



