IDENTIFICATION OF BACTERIA BY PFEIFFER's TEST 139 



cance of phagocytosis. Pfeiffer maintained that bacteriolysis was the 

 most important protective weapon of the immune organism, against bacte- 

 rial invasion. According to Metchnikoff and his followers among whom 

 Bail in particular must be mentioned, bacteriolysis in the abdominal 

 cavity is only an exceptional phenomenon (test-tube experiment in vivo); 

 its occurrence is made possible by the circumstance that the abdominal 

 cavity is as a rule almost free of wandering cells, and that the few which are 

 present are so injured by the severity of the infection that they disinte- 

 grate. If their number increases, bacteriolysis does not occur, or at least 

 is only slight. Likewise, bacteriolysis is incomplete in the presence of 

 cells, for instance in the blood, spleen, liver and subcutaneous tissue, etc. 

 A detailed consideration of this much mooted problem does not fall 

 within the compass of this book. It is sufficient to have pointed out the 

 great questions of fundamental significance which hinge upon the discus- 

 sion of the Pfeiffer experiment, questions which concern the essential 

 features of antibacterial immunity. It can be readily understood, there- 

 fore, why the phenomenon of bacteriolysis has been so much studied, 

 although its practical significance is only limited. 



The Pfeiffer experiment can be used for the differentiation of 

 The Practi- bacteria as well as for the demonstration of bacteriolysins in 

 cal Applica- serum. It serves as a control for the agglutination reaction, 

 tion of the 



Pfeiffer Ex- Pfeiffer and Kolle, Brieger and others, have used bacteriolysis as a 

 periment. method of estimating the immunity obtained by active protective im- 

 munization against cholera and typhoid in man. It must, however, be 

 questioned whether it is admissible to draw conclusions as to the degree of active im- 

 munity from the height of the bacteriolytic titer of the serum, inasmuch as animals 

 are found which possess no active immunity and still have sera of high bacteriolytic 

 powers. 



The most important practical use of the Pfeiffer experiment lies in the 

 identification of suspected cholera cultures. In Germany, the Pfeiffer test 

 made with the vibrios obtained in pure culture from the suspected patients 

 is required for the official diagnosis of the first cases of cholera. 



The serum used for this purpose should be at least strong enough in 

 amounts of 0.0002 c.cm. to cause the disintegration of the bacteria in one 

 hour, when a mixture of one loopful of an eighteen-hour agar culture of 

 cholera in i c.cm. of nutrient bouillon is injected into the peritoneal 

 cavity of a guinea-pig. 



For this experiment four guinea-pigs of 250 gms. weight are used. 



