CHAPTER VII. 



THE LYSINS. 



One of the most important contributions to the science of bacteri- 

 ologj made during the last decade of the nineteenth century was the 

 discovery of what is known as Pfeiffer's phenomenon. In his ex- 

 periments, R. Pfeiffer discovered that if cholera bacteria are placed 

 in the peritoneal cavity of a guinea-pig which has been immunized 

 to cholera, the bacterial cells are dissolved by the peritoneal fluid. 

 If such an injection be made and portions of the bacilli be removed 

 with capUlaiy glass tubes every five minutes, it can be plainly seen, 

 under the microscope, that the bacterial cells are undergoing solu- 

 tion in the surrounding fluid just as lumps of salt dissolve in water. 

 The bacilli lose their motility, swell up, and then break into small 

 granules which gradually melt away into the fluid. Extended in- 

 vestigation showed that this reaction is specific and the same phe- 

 nomenon may be observed in animals which have been immunized 

 to the typhoid bacillus or other pathogenic microorganisms, and by 

 this means the cholera bacillus may be differentiated fix)m other 

 vibrios. Moreover, when a mixed culture is subjected to this test, 

 the peritoneal fluid dissolves the bacteria of the species against 

 which the animal has been immunized and leaves all other bacteria 

 untouched. Pfeiffer found that it was not necessary to use an im- 

 munized animal, but that the same result can be obtained by placing 

 a small quantity of a cholera culture mixed with the serum of a 

 guinea-pig which has been immunized to cholera, in the abdominal 

 cavity of a normal guinea-pig. Later, Metschnikoff ' discovered 

 that Pfeiffer's phenomenon, which is also known as bacteriolysis, 

 takes place in vitro, when to a mixture of cholera serum and the 

 cholera culture there be added a small quantity of the peritoneal 

 exudate from a normal guinea-pig, and Bordet added the observa- 

 tion that cholera serum in and of itself suffices to induce bacteri- 

 olysis in vibro when it is perfectly fresh. On long standing it be- 

 comes inactive, but its activity even then may be restored by the 

 addition of a small quantity of normal serum. Pfeiffer repeated 

 Bordef B experiments, and confirmed them in a modified way, inas- 

 much as Pfeiffer found that not every fresh blood serum had the 

 same effect, and that the process of bacteriolysis as observed in vibro 

 is not comparable in intensity with that observed in the animal body. 



> Annates <UfIn»tUut PaOatr, 1895. 

 122 



