THEORIES OF IMMUNITY. 



bacteria follows the laws of the destruction of 

 formed elements in general, and this resorption 

 is, in the last analysis, the work of two soluble 

 digestive ferments, of which one (fixateur, 

 immune body) is easily excreted by the phago- 

 cyte into the plasma of the blood and exuda- 

 tions, and the other may exist there at all times. 



The theory of the phagocytes attempts to es- 

 tablish these principles in as exact a fashion as 

 possible, but it has not attempted to penetrate 

 the depths of the phenomena of intracellular di- 

 gestion, which is mixed up with the action of 

 soluble ferments in general, and this problem is 

 still far from being solved. 



In spite of the numerous objections, the theory 

 of phagocytosis within the limits indicated has 

 not only not been overthrown, but appears to 

 have slowly and gradually gained strength, as is 

 shown by the marked disappearance of opposi- 

 tion that is very noticeable of recent years. 

 Such changes are shown by the instance given 

 (Metchnikoff, I. c.) of Buchner's change of atti- 

 tude toward the theory (Muench. Med. "Woch., 

 1900, p. 1133). At the International Medical 

 Congress in Paris he maintained his theory of 



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