THEORIES OF IMMUNITY. 



Pfeiffer's phenomenon; in places where there are 

 no or almost no preexisting leucocytes, Pfeiffer's 

 phenomenon does not occur at all. The same 

 with the cholera vibrio, — the extra-cellular de- 

 struction does not exist except under special con- 

 ditions, and the vast majority of other bacteria do 

 not show this phenomenon at all under the con- 

 ditions in which the cholera vibrio manifest it. 



Metchnikoff interprets the facts as indicating 

 that this destruction of the bacteria takes place 

 in the tissues as the result of the action of the 

 soluble ferments of the phagocytic" digestion. 

 These ferments are normally found in the inte- 

 rior of the phagocytes, and not outside except as 

 the result of the destruction or temporary injury 

 of these cells. 



Such a conclusion was in direct contradiction 

 to Pfeiffer's belief, who laid especial stress upon 

 an action of the endothelial secretions. So that, 

 to prove that these latter had nothing to do with 

 it, the reaction should occur outside of the body. 

 This Metchnikoff easily did by adding a little 

 lymph, full of leucocytes, to an inactive anti-in- 



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