THEORIES OF IMMUNITY. 



The facts in hemolysis and bacteriolysis have 

 led to the investigation of the action of other 

 kinds of cells when introduced into fresh ani- 

 mals. A very large number of different kinds 

 of action of this nature have been studied, and 

 it is demonstrated that it is possible to secure 

 sera of many sorts which have a specific action 

 upon the cells originally used for the production 

 of the cytolytic power. Thus, for example, the 

 study of the results following the injection of 

 living spermatozoa has been the demonstration 

 of the production, in the serum of the animal in 

 which they are injected, of ii property that has 

 the power of immobilizing fresh spermatozoa, if 

 not of absolutely dissolving them ; the same 

 thing holds true of other cells. Liver cells in- 

 jected in the same way will produce a serum 

 capable of inducing fatty degeneration of the 

 liver cells of a fresh animal. Of course the pos- 

 sible results that may come from such cytolytic 

 action as this are of the most important nature. 



The reactions are explained by Ehrlich in the 

 same way as the phenomena of hemolysis and 



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