168 INTRODUCTION 



in immunity the antibody disappears a short time after the at- 

 tack, but this does not prevent the persistence of immunity for 

 years, or even decades, after the disappearance of the antibody. 



To summarize : however the serum of hyperimmunized animals 

 or the serum of an individual affected with some infectious disease 

 may act, it is impossible to establish any relation between the 

 antibacterial antibodies so-called and immunity. These anti- 

 bodies, like the agglutinins, can only be considered as indices 

 of infection. 



It may be objected that preventive vaccination by a sensitized 

 virus indicates a fragility in the bacteria impregnated with anti- 

 body. This objection is in reality not an objection, for experi- 

 mental facts show, on the contrary, that a sensitized bacterium 

 is as virulent as a normal bacterium. I have proved this for 

 B. typhi murium with the mouse, and for the bacterium of bovine 

 hemorrhagic septicemia in cattle. These animals are killed in 

 the same time and by the same dose, whether the bacteria in- 

 jected are normal or sensitized. The possibility of injecting man, 

 without great inconvenience, with sensitized cholera vibrios or 

 sensitized typhoid bacilli (and it may still be said with some re- 

 serve in this last case) does not negative these findings at all, 

 seeing that Ferran has given tens of thousands of preventive 

 vaccinations against cholera, using living cultures, and that Ch. 

 Nicolle has demonstrated the possibility of vaccinating man 

 against typhoid fever by injecting him with living, normal 

 typhoid bacilli. In general, injections of sensitized bacteria are 

 no more inoffensive than injections of the normal living organ- 

 isms, and they are equivalent, since living sensitized bacteria 

 and living normal bacilli are virulent to the same degree. 



One cannot avoid the conclusion that it is impossible to 

 attribute any active role in the production of antibacterial im- 

 munity to any actually known antibodies. All organic immunity 

 is reduced to antibacterial immunity, assured by phagocytosis, 

 and to antitoxic immunity, assured by the antitoxins. 3 



But is this organic immunity an attribute of the immunized 

 animal only? Is it not enjoyed by a susceptible animal? All 



3 Meaning by antitoxins all antibodies which neutralize a soluble toxic 

 substance. 



