66 METHODS FOR EFFECTING ACTIVE IMMUNIZATION OF ANIMALS 



be remembered that these substances the antigens are toxic, and 

 that the process of immunization may evoke a marked disturbance in 

 the general health of the animal. Special attention should be given to 

 feeding and the general care of the animal, the temperature, weight, the 

 presence of diarrhea, and the occurrence of abscesses, edema, paralysis, 

 etc. 



If the animal dies, a careful postmortem and bacteriologic examina- 

 tion should be made, in order to study the changes produced by the 

 inoculated antigen, and to ascertain if death was induced by the antigen 

 or by contamination and secondary infection. 



In the manufacture of serums on a large scale, especially for thera- 

 peutic use, horses are used almost exclusively. For diagnostic purposes 

 and especially in the study of immunity, smaller animals, such as rab- 

 bits, guinea-pigs, white mice, and rats, and occasionally goats or sheep, 

 are employed. 



So far as their power of producing antibodies is concerned, there are 

 individual differences among the same species of animals; thus, horses 

 immunized against diphtheria differ in the quantity of antitoxin pro- 

 duced. Similar differences are observed in the smaller animals. 



Immunization with a single antigen usually produces several differ- 

 ent antibodies, although for diagnostic or therapeutic purposes one 

 usually predominates. Thus immunization of a rabbit with dead 

 typhoid bacilli produces agglutinin, opsonin, bacteriolysin, and comple- 

 ment-fixing bodies, although the agglutinin is probably the most prom- 

 inent and is used in diagnosis. Immunization with the diphtheria 

 bacillus and its toxin leads to the formation of an antitoxin, opsonin, 

 and complement-fixing body, although antitoxin is by far the most 

 prominent and is used therapeutically. 



We give here methods for making various immune serums from small 

 animals, to be used for the purpose of study and for aiding diagnosis. 

 Curative serums, such as diphtheria and tetanus antitoxin, antimeningo- 

 coccus serum, etc., are made on a larger scale by immunizing horses. 



' GENERAL TECHNIC 



1. The antigens are usually injected subcutaneously, intramuscularly, 

 intraperitoneally, or intravenously. As a rule, the sooner the antigen 

 comes in relation with the body-cells, the more rapid is the immunity 

 gained, and for this reason the intravenous and intraperitoneal routes 

 are frequently chosen. 



