14 APPLIED IMMUNOLOGY 



" stimulin," in antibacterial sera, capable of stimulat- 

 ing leucocytes to increased ingestion and destruction 

 of bacteria. JNIetchnikoiF claimed that immunity de- 

 pended upon this property of phagocytosis. 



It was at this time that Buchner described 

 " alexins," and Bordet " sensibilisators " in sera and 

 their role in the process of immunization. Numerous 

 foreign albuminous substances were utilized for the 

 production of antibodies and conceptions respecting 

 the nature of immunity definitely distinguished two 

 types, active and passive. JMoreover, it was realized 

 that eccotoocic bacteria were adaptable chiefly to pas- 

 sive, and endotoxic bacteria to active, immunization. 



In 1895, Pfeiffer demonstrated his phenomenon 

 of bacteriolysis, thus dealing a severe blow to INIetchni- 

 koiF's doctrine. While the discussion was still warm 

 over PfeifFer's discovery, in the next year Gruber and 

 Durham directed attention to the diagnostical value of 

 " agglutination " of bacteria in their specific antiserum 

 and Widal described the serodiagnosis of typhoid 

 fever. The following year, Kraus described other 

 antibodies, more or less closely related to bacteriolysins 

 and agglutinins, which he styled " precipitins." 



The year 1896 is notable in immunological annals 

 as marking the advent of antityphoid inoculation by 

 Wright. Previously, Ferran and Haffkine had em- 

 ployed attenuated living cultures, prophylactically. 



