CHAPTER VI 



IMMUNIZATION 



The antitoxins and other antibodies are of the 

 greatest importance to the animal body. On them 

 the so-called serum-therapy is founded. In order to 

 protect against illnesses antitoxin is injected in the 

 body — diphtheria, for instance, is treated in this 

 manner — or micro-organisms, living or dead, or their 

 products are injected, after which the patient himself 

 produces antitoxin — this treatment is used against 

 smallpox, for instance. Ehrlich gave the name 

 passive immunization to the first kind of treatment, 

 active immunization to the latter one. 



It is of high interest to know the fate of these 

 foreign substances in the body. For this purpose 

 animals have been treated in the said manner, and 

 samples of their blood have been taken at different 

 times and their content of antibodies investigated. 

 Some rather remarkable regularities have been 

 observed which will be spoken of in the following 

 pages. 



To begin with we may consider passive immun- 

 ization. Antidiphtheric serum, or other antibodies, 



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