32 POISONOUS PKOTEINS 



As has been said, we found the cellular pro- 

 teins of all the bacteria studied more or less 

 harmful to animals when introduced parente- 

 rally. The size of the dose necessary to pro- 

 duce a fatal result varies greatly with the 

 source of the protein. The cellular substance of 

 bacteria to which in its living state an animal 

 is highly susceptible does not kill that animal 

 at all or does so only after large doses. We 

 have injected into the abdominal cavities of 

 guinea-pigs the cellular proteins of the tuber- 

 cle bacillus in quantities of from five to two 

 hundred mg. without causing death in a single 

 instance, while on the other hand a fraction of 

 a mg. of the protein from bacillus prodigiosus 

 kills. To kill a guinea-pig one part of the cel- 

 lular substance of the anthrax bacillus to 1,700 

 parts of body weight is necessary, while with 

 the colon substance one part to 75,000 kills all 

 animals provided the material is finely ground. 

 In general it may be said that the more highly 

 susceptible a given animal is to infection with 

 a given bacterium the more difficult it is to kill 

 that animal with the cellular protein of that 

 bacterium. On the other hand, the more highly 

 immune a given animal to infection with a given 

 bacterium the more readily does that animal 

 succumb to injections of the cellular proteins 



