THE LIVING ORGANISM 209 



until the fluid part of the blood of the 

 animal is as highly charged as possible 

 with the antitoxin, and the animal itself 

 is now immune to the disease. Incidentally, 

 it may be mentioned that this is what is 

 achieved in the body of man himself (or 

 highly valuable animals) by preventive vacci- 

 nation or inoculation, as in smallpox vaccina- 

 tion. 



Now, returning to antitoxic treatment, 

 small quantities of the blood of such an 

 immunized animal when drawn off contain 

 dissolved in the fluid part of the blood (or 

 serum) chemical substances capable of neu- 

 tralizing the poisonous toxins, and these are 

 the antitoxins, or natural antidotes to the 

 disease. 



Such is anti-diphtheritic serum or diphtheria 

 antitoxin. It produces its wonderful effect 

 by yielding early in the disease a supply of 

 just that material which the body is struggling 

 to make for itself, and this auxiliary supply 

 both protects the vulnerable tissues, and 

 being absorbed by the invading organisms, 

 weakens them at an early stage when as yet 

 they are not very abundant and so renders 

 them both less productive and also an easier 

 prey to the natural forces at work. 



It is now readily seen why the anti-toxic 



