THEORIES OF IMMUNITY. 



otherwise the experiments of Hey mans (quoted 

 by Ehrlieh himself) would upset the theory 

 entirely. In these he injected a minimal lethal 

 dose of tetanus toxine and immediately removed 

 all the blood of the animal, at the same time 

 replacing it by the blood of a fresh animal, yet 

 death occurred from tetanus just the same. 

 These experiments as well as many others show 

 that the toxine must act within the fixed cells as 

 well as in the free cells of the blood or body 

 fluids, but just where this reaction takes place 

 has not been definitely proven. The suggestion 

 that the antitoxine may be the result of the 

 splitting up of the toxine molecule, while con- 

 ceivable, is negatived by the facts thus far 

 observed that seem to show that the toxine 

 molecule is smaller than that of the antitoxine. 



Antitoxine is formed in the body somewhere, 

 there can be no doubt of that in the minds of 

 any one who has ever had to do with the im- 

 munizing of horses with diphtheria toxine. In 

 these animals, after bleeding and the removal of 

 a considerable proportion of the antitoxine pres- 

 ent, there is a return of antitoxic strength in the 



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