162 COLLECTED STUDIES IN IMMUNITY. 



stration that the groups exciting the production of immunity are actually 

 the same as those which in haemolysis anchor the immune body. We 

 have seen, however, that there is not always an absence of reaction 

 and that even the injection of the same saturated blood, which in one 

 animal fails to cause a production of immune body, is followed in 

 another animal by a certain low-grade production of immune body. 

 The cause of these phenomena can only be that certain animals 

 possess the individual capacity to anchor the saturated receptors in 

 spite of this saturation. We do not know the mechanism of this 

 action. Two factors in particular come into consideration; a part 

 of the immune body may perhaps be destroyed in the animal body 

 through special agencies (oxidation?) and the receptors thereby set 

 free. It is also possible, however, without assuming a destruction of 

 immune body to explain the phenomenon in the sense of Ehrlich's 

 views, by assuming a higher affinity of the tissue receptors present in 

 the animal body, which receptors then would be able to break up the 

 union of blood-cell receptors and immune body, and draw the blood- 

 cell receptors unto themselves. 1 



Whichever of these explanations is the correct one, our experiments 

 certainly show one thing, that the dissolution of the blood-cell receptor 

 combination is never a complete one. Merely a portion of the groups 

 is concerned, for only by this partial dissolution is the fact (determined 

 by Neisser and Lubowski, as well as by us), to be explained that a 

 very slight degree of immunity reaction is produced by the injection of 

 saturated receptors. 



Hence even in the cases running an apparently unfavorable 

 course, only a part always of the receptors exert their action. This 

 portion of the experiments may therefore also be used as a sup- 

 port for the side-chain theory. 



1 A similar assumption must be made in order to explain certain forms of 

 over-sensitiveness studied particularly by v. Behring, in which, despite a large 

 excess of antitoxin, very small doses of toxin cause death. The most ready 

 explanation is that here, in contrast to the behavior in normal animals, the 

 toxinophile receptors possess a pathologically increased avidity by which they 

 are enabled to break up the neutral toxin-antitoxin mixture (which cannot be 

 broken up by normal cells) and take up the toxin thus set free. 



