PFEIFFEFS PHENOMENON. 481 



Lysogenic Action. Pfeiffer found that if certain organisms, 

 e.g., the cholera spirillum, were injected into the peritoneal 

 cavity of a guinea-pig highly immunised against these 

 organisms they lost their motility almost immediately, 

 gradually became granular and swollen up in places into 

 droplets, and then disappeared in the fluid, all these changes 

 sometimes occurring within half an hour lysogenic action. 

 Further, he found that the same phenomenon was witnessed 

 if a minute quantity of the anti-serum (that is, the serum of 

 an animal highly immunised against the corresponding 

 organism) was added to a certain quantity of the organisms, 

 and the mixture injected into the peritoneal cavity of another 

 animal. In both cases the organisms die an extracellular 

 death, and their destruction is brought about by the 

 medium of a specific substance in the anti-serum. Pfeiffer 

 found that the serum of convalescent cholera patients gave 

 the same reaction as that of immunised animals, that is, it 

 possesses specific antagonising substances. He obtained 

 the same reaction also in the case of the typhoid bacillus 

 and other organisms. From his observations he concluded 

 that the reaction was specific and could be used as a means 

 of distinguishing organisms which resemble one another. 

 He considered that the specific substance in the serum 

 existed chiefly in an inert form, and that it became actively 

 bactericidal l by the aid of living cells, probably those of 

 the peritoneal endothelium. Thus he found that if the 

 anti-serum was injected into the peritoneal cavity of a fresh 

 animal, and if, after a time, some of the peritoneal fluid 

 was withdrawn and the corresponding organism added to 

 it, the reaction could be observed outside the body. 

 Metchnikoff, however, showed that the same result was 

 obtained when the organism was simply placed in some 

 fresh peritoneal fluid to which the anti-serum had been 

 added outside the body. In this case, accordingly, the 

 action of the endothelial cells was excluded. 



Borclet confirmed this observation and showed further that a small 



1 In some cases an antimicrobic serum possesses specific directly bac- 

 tericidal powers, but this is not a general law. 



