METHODS 103 



which it will impose its own state, or whether it will be van- 

 quished and assimilated by the animal. In the former case 

 we say the colloid is toxic ; in the latter that it is a food in 

 relation to the given animal. When the animal A conquers, 

 the colloid B must have determined in the animal the func- 

 tion (A x B), the trace of which will be found in its serum ; 

 and the animal will consequently develop the organ corres- 

 ponding to the function. In this way, when the battle is 

 over and the colloid B has been conquered, the animal A will 

 continue to produce in its interior medium the diastase de- 

 fined by the function (A x B). This, indeed, is currently 

 verified. A horse into which diphtheritic toxin has been 

 injected continues for a long time to furnish an antitoxic 

 serum ; and when the function weakens it is revived by 

 giving the animal a new injection of the same toxin. 



