CHAPTER XII. 

 BACTERIOLYSINS AND HEMOLYSINS (CYTOLYSINS). 



If a guinea-pig is immunized with living or dead bacteria, for instance 

 cholera or typhoid, and then to test its immunity is injected with a single 

 fatal or many fatal doses of living bacilli, the animal remains alive; whereas 

 a normal-control animal, not treated beforehand, succumbs to a similar 

 inoculation. In order to determine the forces to which the immunized 

 animal owes its protection, Pfeiffer undertook the following experiment: 

 Two guinea-pigs, one immunized and another normal, were simultaneously 

 injected intra-peritoneally with living cholera vibrios, and the peritoneal 

 exudate was withdrawn from time to time and examined microscopically 

 in hanging-drop preparations. (The method of withdrawing the peritoneal 

 fluid with capillary pipettes and other technical details will be described 

 below.) 



A very striking phenomenon occurred. While the cholera 



Pfeiffer's vibrios in the peritoneal exudate of the normal animal retained 

 Phenomenon, their form and motility and increased in number continuously 

 until the animal succumbed to the infection, the bacteria in 

 the peritoneal exudate of the immunized animal behaved quite differently; 

 they first began to lose their power of locomotion, then their form changed, 

 they broke up into evenly small shining masses, so-called "granula," 

 and finally, after several minutes these also disappeared. Guinea-pigs in- 

 jected with the peritoneal exudate from these infected immune animals 

 remained healthy, and nutrient media inoculated with material from the 

 same source remained sterile. 



The above experiment is named after its discoverer, Pfeiffer, and the 

 phenomenon itself, "bacteriolysis." 



Bacteriolysis is a strictly specific process. If an animal which is immune 

 to cholera is inoculated with typhoid bacilli, the bacteria markedly increase, 

 as in a normal animal. The process by which this bacteriolytic force takes 

 place is clearly demonstrated when a mixture of living cholera vibrios and 

 blood serum of a guinea-pig which has been actively immunized against 

 cholera, is injected into the peritoneal cavity of a normal guinea-pig and as a 

 control, normal serum mixed with living cholera vibrios is. inoculated into a 

 second guinea-pig. Here the exudates on examination from time to time 

 show that in the peritoneal cavity of the animal injected with the immune 



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