Chapter VII 



VARIETIES OF SERA 



Sera may be divided into immune sera and 

 normal serum. Normal Serum is obtained 

 from the blood of normal animals that is, 

 animals which have not undergone any inten- 

 tional process of immunization. Immune Sera 

 are fluids containing antibodies already formed 

 and are derived from the blood of animals that 

 have been specifically immunized. For prac- 

 tical purposes the horse is usually employed 

 for the purpose of producing sera. Immune 

 sera from immunized horses are injected into 

 the circulation or into the tissues of man to 

 supply antibacterial elements or antitoxins 

 without stimulating the tissue-cells of the pa- 

 tient to the production of these substances. 

 Therefore, in the use of immune sera, the anti- 

 bodies formed by the tissue-cells of the horse 

 are supplied to the patient and a condition of 

 passive immunity is established, lasting only 

 a few weeks. 



Action There are two varieties of immune 



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