140 MAN, — THE ANIMAL 



recovers. The study of the conditions of re- 

 covery give us still further insight into this phase 

 of living protoplasm. It is common observation 

 that human beings do recover from measles, ty- 

 phoid fever, diphtheria and other germ diseases. 

 Very little idea of how this recovery was brought 

 about existed until after Jenner, in 1789, at- 

 tempted to imitate nature and artificially produce 

 an immunity to certain diseases. Acting upon the 

 principles discovered by Jenner and others, we 

 have to-day more than a dozen antitoxines. If 

 it were possible to remove the germs which cause 

 any given disease from the body, the elaborate 

 experimentation which has been carried on to 

 discover suitable antitoxines would be unnecessary. 

 The underlying principle in the use of antitoxines 

 (and there must be a specific one for each disease 

 because the toxines produced by each different 

 germ are distinct) is gradually to accustom the 

 cells of the body to the poison in a mild form so 

 that during the process these same cells will 

 elaborate antibodies for the particular poison in- 

 troduced into the body. 



It is now possible to produce these antibodies 

 in animals other than man, extract them from 

 their blood and preserve them for subsequent use 

 in man when he happens to be suffering from 

 diphtheria, for example. Such antibodies are 

 called antitoxines. An antitoxine when introduced 



