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 im- 

 munized animal owes its protection, Pfeiffer undertook the following 

 experiment: Two guinea-pigs, one immunized and another normal, were 

 simultaneously injected intraperitoneally with living cholera vibrios, and 

 the peritoneal exudate was withdrawn from time to time and examined 

 microscopically in hanging-drop preparations. (The method of withdraw- 

 ing 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 re- 

 Phenomenon, tained their form and motility and increased in number con- 

 tinuously 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 injected 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 cholera serum, the same phenomena of bacteriolysis 

 occur as described above, leading to the sterilization of the peritoneal 

 cavity, and protection of the animal from illness. In the control animal , 



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