IO4 Immunity 



Fredericq, and studied by Mesml. It seems to be related 

 to papine and digests albuminoids. The digestion of ery- 

 throcytes and tissue fragments is accomplished through an 

 enzyme of the macrophages, which Metschnikoff calls macro- 

 cytase, that of bacteria through an enzyme of the microphages, 

 which he calls microcytase. In phagolysis these respective 

 ferments are liberated into the plasma, imparting to it a 

 bactericidal and bacteriolytic action similar to that normally 

 peculiar to the cytoplasm of the cells. The dissemination 

 of the enzymes in phagolysis, with resulting bacteriolytic 

 power of the blood plasma and serum, is a later modification 

 of the original conception of Metschnikoff, that the invading 

 parasites were eaten up by the phagocytes, and was made 

 necessary by the investigation of the bactericidal property of 

 the body juices, to which some attention must now be devoted. 

 The experiments of Wright and Douglas* indicate that the 

 action of the phagocytes upon the bacteria is not i nmedi- 

 ate, but only subsequent to a preparative action upon the 

 organisms by substances contained in seru 11, and to whhh 

 they give the name " Opsonins" (I^at. opsono, "I prepare 

 a meal for"). 



Long before Metschnikoff began his studies of the pha- 

 gocytes Traube and Gscheidelf observed that the blood 

 plasma possessed the power of destroying the vitality of 

 bacteria. GrohmanJ next observed that not only the 

 intravascular, but also the extravascular blood possessed 

 this property. The first exact investigations of the subject 

 were made by von Fodor. The systematic investigation of 

 the bactericidal activity of blood-serum in vitro was next 

 taken up by Flugge|| and more particularly by Nuttall,** 

 who found that different blood- serums possessed the power 

 of killing bacteria in large numbers, but that the bactericidal 

 power of the serum soon disappeared, after which the serum 

 became a good culture medium for the very bacteria it had 

 formerly destroyed. Metschnikoff objected to the observa- 

 tions, declaring that all the phenomena were ultimately 



*" Proc. Royal Society of London," LXXXII, p. 357, 1904 

 t " Jahresberichte der Schles. Ges. f. vaterl. Kultur," 1874 

 J " Untersuchungen aus dem physiol. Institut zu Dorpat," Dorpat, 

 1884; Krtiger 



" Centralbl. f. Bakt.," etc., 1890, vn, p 753. 

 || " Zeitschrift fur Hygiene," Bd. iv, S. 208. 

 ** "Zeitschrift fur Hygiene," Bd. iv, S. 353. 



