ANTISERA. 35 



Preparation of Antitoxic Sera 

 When bacteria whose action depends upon toxins 

 separated from them in the process of growth enter 

 the body, they, as a rule, remain at the point of en- 

 trance, from which the toxins spread through the cir- 

 culation. In response to the stimulation of the toxins, 

 the body produces antitoxins in the blood-serum, by 

 which their deleterious action is neutralized. The anti- 

 toxins at the same time render harmless to some extent 

 the living bacteria at the point of entrance. This proc- 

 ess is termed active immunization. 



Antitoxin production is artificially induced by ac- 

 tive immunization of suitable animals by subcutaneous, 

 intraperitoneal or intravenous injections of the toxins 

 of certain bacteria. The antitoxin thus formed not 

 only protects the animal inoculated, but can also be 

 removed from the original animal and used as a cura- 

 tive and protective agent against the same infection in 

 other animals, by means of injections. The process in 

 the second animal is known as passive immunization. 

 So we distinguish active from passive immunization by 

 the fact that in the former the animal produces its own 

 antibodies to combat an infection, while in the latter 

 the antibodies have been produced by another animal 

 ( see Chapter I ) . 



As an example of the preparation of antitoxic sera, 

 the method of artificial production of antidiphtheritic 

 serum (diphtheria antitoxin) will be described. 



