PHAGOCYTOSIS IN IMMUNITY. 313 



well aware that fibrin ferment is liberated under 

 these circumstances. 



It was equally desirable, if possible, to determine 

 the relation of fixators to the leucocytes. The sit- 

 uation is, however, very complex, and, although 

 Metchnikoff regards the fixators as secretion or ex- 

 cretion products of phagocytic cells, the question 

 is, perhaps, not definitely settled. When phagoly- 

 sis is prevented in the manner described, the in- 

 jected erythrocytes may well absorb fixators from 

 the plasma and still undergo no hemolysis until en- 

 globed by the phagocytes. It is considered that 

 fixators in contrast to cytase may exist in the cir- 

 culating plasma. 



Phagocytosis as a feature of local resistance phagocytosis 

 against microbic invasion was considered in rela- in Immnnit *- 

 tion to inflammation. We come now to speak of 

 the relationship of the leucocytes to general 

 states of immunity, having reference to the condi- 

 tions which have been designated as natural and 

 acquired antibacterial immunity, and natural and 

 acquired antitoxic immunity. 



The first expressions of Metchnikoff concerning 

 the antimicrobic activity of phagocytes, the power 

 of freeing the organism from "invaders of every 

 sort," were made altogether from an a priori stand- 

 point in an address delivered in 1883, "Ueber die 

 Heilkrafte des Organismus." He justified his po- 

 sition on general grounds, having in mind the 

 "more general phenomena of phagocytosis and the 

 resorption of corpuscular elements," as he had 

 observed them in various zoological studies. 



Shortly there came to him the opportunity of Natural im- 



, i . . ,. ,. -,. ji T\ i mnnlty to 



studying an infectious disease among the Daphma Bacteria. 



