io8 Immunity 



amebadiastase, and regarded as a form of trypsin. The 

 intracellular digestion of coelenterate animals is accomplished 

 by means of actino diastase, an enzyme discovered by 

 Fredericq, and studied by Mesnil. 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 w r as made 

 necessary by the investigation of the bactericidal property of 

 the body juices. The experiments of Wright and Douglas* 

 indicate that the action of the phagocytes upon the bacteria 

 is not immediate, but only subsequent to a preparative 

 action upon the organisms by substances contained in 

 serum, to which they have given the name " Opsonins" (Lat. 

 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 Plugge|| 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 



*" 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; Kriiger 



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

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

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



