138 PATHOGENIC BACTERIA. 



seems possible to produce strongly germicidal serums 

 with rich cultures of feeble virulence. In the treatment 

 of the toxic diseases the antimicrobic serums are far less 

 useful than the antitoxic serums, but in the invasive dis- 

 eases their r61e is daily becoming more and more im- 

 portant, and a place in the therapeusis of plague, suppu- 

 rations, pneumococcus infections, typhoid fever, and 

 cholera, is being assigned to them. 



The most striking illustration of the protective action 

 and operation of an antimicrobic serum is probably 

 observed in connection with the choleraic peritonitis of 

 guinea pigs in what is known as "Pfeiffer's 1 phenome- 

 non." When virulent cholera organisms are injected into 

 the peritoneal cavity of guinea pigs a peritonitis with some 

 effusion develops and is fatal in about three days. The 

 fluid within the peritoneum abounds with healthy, 

 actively growing, motile cholera organisms. If a very 

 small quantity (0.002 c.c.) of the serum of a guinea pig 

 .immunized to cholera be injected into a guinea pig with 

 well-developed choleraic peritonitis, it is found by the 

 microscopic examination of occasional drops of fluid from 

 the peritoneum that the energy of the micro-organism 

 rapidly wanes, that they become less active, soon agglu- 

 tinate in clumps, die, and undergo a granular degenera- 

 tion, the animal recovering from the infection. The phe- 

 nomenon was also observed when the serum of cholera 

 convalescents was employed instead of that of immun- 

 ized animals. The power of the serum to bring the 

 changes about was destroyed by heating to 6o° C. 

 Later the same phenomenon was observed in typhoid 

 infection. 



Pfeiffer found that if some of the serum was injected 

 into a healthy guinea pig, the fluid withdrawn from the 

 body was capable of producing the same phenomenon in 

 the test-tube. Metschnikoff also found that an identical 

 reaction resulted when the serum was added to fresh 

 peritoneal fluid outside the body, thus eliminating the 



1 Zeiischrift fiir Hygiene, 1 894, Bd. 1 8 and 20. 



