IMMUNITY. 307 



using poisonous " metabolic products " to pro- 

 tect against the virulent disease called Ameri- 

 can swine-plague. Such soluble substances, 

 it was hoped, could be measured accurately 

 and then safely introduced into the body in 

 definite quantities. With substances of this 

 kind, freed from germs by heating or by filtra- 

 tion, Foa and Eonome produced immunity 

 against Proteus-, Charrin against Pyocyaneus, 

 Roux and Chamberland against maligant 

 oedema, Roux against symptomatic anthrax, 

 Gamaleia against the Vibrio septicaemia of 

 pigeons and against cholera, and C. Frankel 

 against diphtheria. 



It might seem safe to infer from these facts 

 that immunity consists in accustoming the 

 organism to the " specific " poisons of the dis- 

 ease germs. Such a conclusion, however, is not 

 in harmony with the observations previously 

 mentioned as made by me in 1887 and by 

 Chauveau in 1889, for we succeeded by the use 

 of entirely attenuated bacteria, which had be- 

 come wholly saprophytic and no longer capable 

 of forming specific poisons, in producing im- 

 munity towards these same bacteria in a fully 

 virulent condition. Hueppe and Wood suc- 

 ceeded also in 1889 in producing immunity to- 

 wards disease-producing bacteria by inoculation 

 with ordinary saprophytes derived from water 



