IMMUNITY. l8l 



the bacteria for the phagocytes. These substances are devel- 

 oped in the blood under certain conditions. Thus, injections 

 of dead cultures of the S. pyogenes aureus into the blood pro- 

 duces a substance which prepares the live staphylococcus as 

 food for the phagocytes. Substances acting in this way they 

 call "opsonins" (opsono, I prepare victuals for). 



These authors find that phagocytosis for certain organisms 

 depends upon the presence of opsonins in the blood. Thus, 

 B. typhosus, S. choleras Asiaticas, B. coli communis, B. dysen- 

 teriae, S. pyogenes aureus, B. pestis, M. melitensis, D. pneu- 

 moniae, are all taken up by phagocytes after being prepared by 

 the opsonins. B. diphtherias and B. xerosis are not acted upon 

 by opsonins. 



Neufeld and Rimpau* found that antisireptococcus serum 

 acts as an opsonin. 



Just the contrary effect to opsonins, on the other hand, is 

 produced by certain other bodies; for Bailf has found that 

 when tubercle bacilli undergo bacteriolysis certain substances 

 are liberated which check phagocytosis. These he regards as 

 endotoxins, and gives to them the name aggressins. 



There can be no doubt but that phagocytosis plays an im- 

 portant part in combating bacterial infection. And what fol- 

 lows in regard to the germicidal and antitoxic action of the 

 fluid portion of the blood containing no phagocytes does not 

 alter the fact that phagocytes, when these are present, do de- 

 stroy the bacteria. Moreover, Metchnikoff maintains that 

 the germicidal property of the blood-serum free from cells is 

 due to substances liberated from the phagocytes by phagolysis, 

 or breaking up of phagocytes. In other words, he holds that 

 infection is combated by the phagocytes or by substances de- 

 rived from the phagocytes. 



* Deutsche medicinische Wochenschrijt. 1904. Bd. XXX., p. 1458. 

 ■\ Oskar Bail. Wiener klinische Wochenschrijt. Bd. XVIII. 1905. Re- 

 view in Bulletin de I'Institut Pasteur. III. p. 348. 1905. 



