PROPERTIES OF ANTIBACTERIAL SERUM. 481 



phenomenon was witnessed if a minute quantity of the anti-serum 

 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 sub- 

 stance in the anti-serum. Pfeiffer found that the serum of con- 

 valescent cholera patients gave the same reaction as that of 

 immunised animals. 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 also found that an anti-serum heated 

 to 70 C. for an hour produced the reaction when injected with 

 the corresponding organisms into the peritoneum of a fresh 

 animal. He considered that the specific substance in the serum 

 existed chiefly in an inert and somewhat stable form, and that 

 it became actively bactericidal by the aid of living cells, probably 

 those of the peritoneal endothelium. Metchnikoff, however, 

 showed that lysogenesis occurred when the bacteria were simply 

 placed in some fresh peritoneal fluid to which the anti-serum 

 had been added outside the body, and Bordet showed that the 

 serum of a fresh animal could be substituted for peritoneal fluid 

 with the same result. The latter observer also found that in 

 some cases the anti-serum alone, if used quite fresh, could pro- 

 duce in vitro the destruction of the bacteria. In these cases, 

 accordingly, the action of the endothelial cells was excluded. 

 Bordet found that in every case in which Pfeiffer's reaction took 

 place within the body of an animal, a similar lysogenic reaction 

 could be observed by his method outside the body. 



His method was the following: (a} An emulsion of the living organisms 

 (for example, of the cholera vibrio) was made by adding a young culture to 

 about 5 c.c. of bouillon ; () two drops of this emulsion were taken, and mixed 

 with a small drop of anti-cholera serum ; (c) a drop of this mixture was taken, 

 and there was added to it a drop of equal size of fresh serum from a normal 

 guinea-pig. A hanging-drop preparation was made, and a change similar to 

 that described by Pfeiffer was observed within one to two hours if the prepara- 

 tion was kept at the temperature of the body. 



The outcome of the research with regard to lysogenic action 

 may be said to be the following. In order to produce the occur- 

 rence of the phenomena, two substances are necessary. One is 



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