ANTITOXINS 



477 



cells are able to manufacture the protective substances, antibodies, 

 rapidly enough to counteract the work of the bacteria or their 

 poisons, we recover from the disease. In such a case as this, the 



■Crisis 



onset-* 



convalescence 



periocC of 

 incubatiora 



jpection 



. perioct 

 ofimmurnit^ 



Read your text, study the diagram carefully, and then explain how the body produces an 

 immunity against a specific disease. 



body cells do the work in righting the disease, and the immunity 

 thus acquired is said to be active. In case the body cells themselves 

 do not work, and, instead, an antitoxin is used, which is manufac- 

 tured outside the body, we have an example of passive immunity. 

 Let us consider the latter case first, as it is easier to understand. 



What are antitoxins and how are they used ? An example of 

 passive immunity is that obtained by the antitoxin treatment for 

 diphtheria. This treatment, as 

 the name denotes, is a method 

 of neutralizing the toxin given 

 off by the bacteria into the body. 

 It was discovered by a German, 

 Von Behring r that the serum of 

 the blood of an animal immune 

 to diphtheria is capable of neu- 

 tralizing the poison produced 

 by the diphtheria-causing bac- 

 teria. Horses develop large 

 quantities of antitoxin when 

 given the diphtheria toxin in 

 gradually increasing doses. 



day 

 1st, 



2nd 



3rd 



4rtfe 



5th 



deaths "per- loo cases 



none 



SI 





II 1 





IS. 1 





» ■■■■■■'■■: I 





The early use of antitoxin in cases of diph- 

 theria greatly decreases the death rates from 

 this disease. 



