572 



JSTmiKS IX IMMUXITY. 



natural consequence for us to assume that normal rabbit serum con- 

 tains the corresponding counter-group 3 in such high concentration 

 that even small amounts are able to neutralize 6 and so prevent its 

 union with the amboceptor anchored by the cell. See Fig. -. 



Coming no\v to the question whether, after group 3 is occupied, 

 group a no longer reacts with a. or whether, while the reaction takes 

 place, the union remains a very loose one, we decided this according 

 to the following considerations. If the latter assumption were cor- 

 rect, it would follow that the loose union should subsequently become 



^// 



FIG. 2. 3: Coraplementophile group of an amboceptor of normal serum. 



Otherwise as in Fig. 1. 



firm if in some way group l> could again be freed from its combination 

 with 3. In that case, evidently, the "curative" action of the anti- 

 amboceptor a should become manifest. If, on the contrary, a has not 

 been bound at all, this "curative" action should fail to appear on 

 the removal of b. 



Owing to the presence of group 3 in small amounts in normal 

 rabbit serum the possibility is given of abstracting the antigroup 6 

 already bound to the sensitized cell. We have at once taken advan- 

 tage of this fact, and attacked the question experimentally as follows: 



Sensitized blood-cells are digested with an excess of the antiserum 



