62 CLINICAL BACTERIOLOGY. 



2. LYSOGENIC ACTIVITY OF THE IMMUNE SERUM (PFEIF- 

 FER'S REACTION). The bactericidal activity of the bodily 

 fluids in the case of artificial immunity differs from that 

 described as due to the alexins, as was discovered by R. 

 Pfeiffer and his pupils. If guinea-pigs are immunized with 

 carefully destroyed cultures against cholera-vibrios, typhoid- 

 bacilli, coli commune, and other similar microorganisms, 

 the animals thus treated acquire the property of dissolving, 

 after intraperitoneal introduction, the bacteria toward which 

 they have been immunized. In order to follow this phe- 

 nomenon, which is now generally known as Pfeiffers reac- 

 tion, directly under the microscope, a small amount of the 

 exudate that forms in the abdominal cavity shortly after in- 

 traabdominal injection of the bacteria is removed, from time 

 to time, by means of capillary glass tubes. Immediately 

 after the injection the microscopic field exhibits complete 

 immobility of the bacteria ; several (up to ten) minutes later 

 these appear swollen, exhibit beginning disintegration into 

 granules, and after the lapse of ten minutes more the exu- 

 date contains only fine granules. If, at this time, plates are 

 inoculated with the fluid obtained, they remain sterile. 

 Precisely the same results are obtained if, instead of vacci- 

 nated guinea-pigs, animals are employed that were not pre- 

 viously treated, and cholera-bacilli or typhoid-bacilli, mixed 

 with a minimal amount of serum from an animal that has 

 been immunized against cholera or typhoid fever, are in- 

 jected into the peritoneum. In this experiment, also, dis- 

 integration of the bacteria into fine granules, a gradual dis- 

 solution within the infected body, is observed. 



Pfeiffer designates as bactericidal such serum as yields 

 the reaction described by him. This designation, however, 

 has, as has already been pointed out, been employed in 

 another sense namely, for the germ -destroy ing action of 

 blood-serum in the test-tube. It is, therefore, well to 

 adopt the suggestion of C. Frankel, who designates such 

 serum as yields the phenomenon of Pfeiffer as lysogenic, or 

 solvent, serum. 



Lysogenic serum tolerates exposure to 60 C. (140 F.) 

 for an hour, its bacterial solvent activity being thus scarcely, 

 if at all, affected. 



Pfeiffer himself had recognized that the serum of normal 

 animals also is capable of inducing the reaction described ; 

 but in this instance it is necessary to inject a much larger 



