268 " SPECIFIC TREATMENT" OF DISEASE 



produced an enormously increased resistance to 

 these poisons. When the serum of such resistant 

 animals was injected into experimentally infected 

 animals it was found to exert a curative effect. 

 By raising the resistance of an animal to a high 

 degree, rendering it hyper-immune, it was found 

 that its serum possessed a considerable protective 

 and curative power. The bacterial poisons are 

 spoken of as toxins and the serum of the hyper- 

 immunized animals as antitoxins. By a toxin we 

 understand a poison of vegetable or animal origin 

 whose exact chemical composition is unknown be- 

 cause of its complexity. A number of toxins are 

 known besides those derived from bacteria: toxins 

 for instance occur in the castor-oil bean and in the 

 venom of snakes, spiders and scorpions. These 

 toxins are only neutralized by their specific anti- 

 toxins, that is diphtheria antitoxin only neutralizes 

 diphtheria toxin, tetanus antitoxin only neutralizes 

 tetanus toxin, etc. When a toxin and its corre- 

 sponding antitoxin are mixed in the test-tube in 

 suitable proportions, the mixture is found to be 

 harmless because the toxin is neutralized by the 

 antitoxin present in the serum. 



The practical results of these discoveries have 

 been of immense value ; in diphtheria alone in all 

 its forms the mortality has been reduced from 

 about 30% to 8% in practice. The antitoxin for 

 tetanus is chiefly used in preventive treatment, 

 being administered to persons (or horses) who have 



