CHAPTER XXX 

 PASSIVE EVEMUNIZATION--SERUM THERAPY 



SERUM therapy may be said to have had its origin in 1890, when von 

 Behring discovered diphtheria antitoxin. He found that guinea-pigs 

 surviving a subcutaneous inoculation of living diphtheria bacilli may 

 harbor virulent bacilli at the site of injection without showing any 

 evidences of intoxication. Subsequent investigation showed that the 

 blood-serum of these animals contained the protective principles, for 

 when the serum was injected into other animals along with the diph- 

 theria toxin, symptoms of the disease did not develop, and, indeed, as 

 was shown later, the immune serum was found capable of neutralizing 

 the toxin in the test-tube. Shortly afterward Kitasato made similar 

 discoveries in studying tetanus, and these antitoxins have since proved 

 of great importance, not only from the new light that has been thrown 

 upon the mechanism of immunity, and they were used as important 

 arguments for the humoral as opposed to the phagocytic theory, and 

 form the very basis and starting-point of Ehrlich's researches, but also 

 from the new and important field of therapy that was now opened, 

 which gave promise and hope for the discovery of a specific serum treat- 

 ment for each bacterial disease. 



At the time it was thought possible to immunize animals with the 

 various microorganisms known to produce disease, and that the immune 

 serums so produced may be employed in the form of specific treatment. 

 This theory rested on the fact that they contained the antibodies that 

 would quickly overcome the infection. With a few of the genuinely 

 antitoxic serums these hopes have been realized; but many other 

 serums have not yielded the expected and wished-for results, although 

 at the present time the reasons for failure are being recognized and 

 gradually eliminated. 



Definitions. It will be remembered that in active immunization 

 our own body-cells are stimulated to produce antibodies, either by 

 reason of the presence of a disease or as the result of vaccination with the 

 antigen of the disease in a modified and attenuated form. In passive 

 immunization, however, our own body-cells do not produce the antibodies, 



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