INFECTION, IMMUNITY, AND RECOVERY. 127 



protective substances, are always present in the body, 

 and that under special need, as when bacterial inva- 

 sion takes place, they are thrown out by the cells in 

 larger quantities, and this is especially true of the 

 special substances needed for existing infection. The 

 antitoxin then acts by fortifying the cells so that they 

 are enabled to resist the action of the toxin. In favor 

 of this view is the fact that the cells of certain ani- 

 mals are undoubtedly proof against these toxins, and 

 yet so far as chemistry in its present development can 

 detect, these cells are the same as similar but sensitive 

 cells in other animals. Another theory is that the 

 toxin, in some way in the body fluids, is changed into 

 antitoxin. This is made slightly plausible by the fact 

 that by the action of electricity there have been obtained 

 substances from toxins which are slightly antitoxic. 

 The practical point to remember is that whether or not 

 the theories are correct, there is no doubt that the pro- 

 tective substances exist. 



