306 BACTERIOLOGY. 



by their proliferation in the body than by the 

 formation of soluble poisons, which are ab- 

 sorbed, pass into the circulation and so affect 

 important tissues like the nerves, muscles or 

 glands. It was shown to be possible, by sepa- 

 rating the poisons from the bacteria by nitra- 

 tion or by killing the bacteria by means of 

 chemicals or heat, to produce with these poisons 

 manifestations of disease that appeared to 

 resemble those which earlier had been pro- 

 duced only with the living bacteria. These 

 poisons were at first, in accordance with 

 Brieger's view, held to be organic bases, the 

 so-called ptomams. Later it was seen that the 

 bacterial poisons were poisonous proteid bodies 

 or substances closely related to proteids or at 

 least not positively separable from them, and 

 that they often possessed properties similar to 

 those of the digestive ferments (p. 125). 



The French investigators Toussaint and 

 Chauveau as far back as 1880 endeavored to 

 establish the theory, in opposition to Pasteur's 

 view, that the protective effect resulting from 

 the incorporation into the body of attenuated 

 disease germs depends upon the fact that the 

 soluble metabolic products of the germs confer 

 immunity. The American investigators Sal- 

 mon and Smith finally proved, in 1886, that 

 this is sometimes the case, by successfully 



