PFEIFFER S PHENOMENON. Up 



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, however, the normal serum 

 has no influence upon the bacteria, so that they increase rapidly and kill 

 the animal. 



It is evident then, that the bacteriolytic power resides not only in the 

 actively immunized animal, but that it may also be transmitted to other 

 animals by means of the former's serum. Bacteriolysis, therefore, is not a 

 property of the tissues of the actively immunized animal, but is to be traced 

 to specific antibodies, "Bacteriolysins" which circulate in the blood serum 

 and body fluids. 



From the above experiment it must be assumed that the phenomenon of 

 bacteriolysis like agglutination and precipitation, can be demonstrated also 

 in vitro. The earlier investigations in this connection, however, were 

 unsuccessful. Bordet was the first to obtain conclusive results and also to 

 elucidate the cause of previous failures. 



While agglutination in vitro and bacteriolysis in vivo were readily pro- 

 duced by mixing living bacteria with old immune serum, bacteriolysis in 

 vitro did not occur under similar circumstances. But when freshly drawn 

 blood serum or exudate of an immune animal was used, bacteriolysis took 

 place in vitro also. (In fact, granule formation can be directly observed by 

 the microscope). When the serum becomes old and twenty-four hours is 

 sufficient to cause the change, it loses its bacteriolytic powers. It seems at 

 first glance as if bacteriolysins may be active outside the body also, but that 

 here they lead only an ephemeral existence. This view, however, is not 

 quite correct; for "inactive" serum, which has become "ineffective" in 

 vitro, can again produce bacteriolysis, if it is utilized to passively immunize 

 healthy animals. Something must exist in the organism, which supplements 

 the inactive bacteriolysins and restores their activity. This "reactivating 

 substance" is independent of the immunizing process, since it is to be found 

 in normal animals also. Furthermore, inasmuch as not only cholera and 

 typhoid immune sera, but also any other immune sera and not only guinea- 

 pig's serum but even rabbit's, horse's, and human serum may in like manner 

 be reactivated, it is evident that the reactivating agent lacks specificity. On 

 account of this peculiar quality of supplementing the inactive bacteriolytic 

 serum so that it can develop its real effectiveness, Ehrlich called the reactivat- 

 ing substance "Complement" Accordingly, the complement is a normal 

 non-specific substance which is found in the body fluids (particularly abundant 

 in the blood serum) of every organism; its existence is evidenced either by the 

 activation or reactivation of bacteriolytic antibodies. 



Bordet demonstrated that the apparent ease with which the bacteriolysins 

 lose their activity is to be traced not to these bodies, but to the complement. 

 If a small amount of fresh normal serum is added to bacteriolytic serum 



