CHAPTER III. 

 ACTIVE IMMUNIZATION. 



IMMUNIZATION WITH LIVING AND DEAD VIRUS. 



Active immunization depends upon the principle, that an organism in 



overcoming a slight infection either naturally or artificially 



The Principle acquired, develops enough protective bodies to withstand a 



of Active similar, severer, natural, or acquired infection. Moreover, 



Immunization, ft serves primarily the purpose of prophylaxis. In laboratories, 



active immunization of animals is also frequently undertaken 



with the view of obtaining sera for diagnostic and therapeutic indications. 



In the manufacture of serum on a larger scale, the horse is the animal 

 used almost exclusively. Occasionally cows, sheep, donkeys or mules are 

 selected. In small laboratories usually rabbits, guinea-pigs, white mice, 

 rats, and only occasionally goats or sheep are employed. 



The process of immunization evokes a marked disturbance in the general 

 health of the animals. For this reason they must be well kept in warm 

 places, and well fed with nutritious food. As far as their power of producing 

 antibodies is concerned, there are individual differences even among the 

 same species of animals; thus if five horses are immunized against diphtheria, 

 some will give much better curative sera than the others. In general, 

 the younger animals are preferable. 



Any substance which, when injected into an organism, can stimulate the 

 production or formation of an antibody, has been conveniently termed " anti- 

 gen." After the injection of such an antigen, special notice should be taken 

 of the animal in reference to temperature, weight, the excitation of diarrhea 

 or the occurrence of abscesses, infiltrates, edema or paralysis. 



If an animal dies, a careful postmortem, and if possible, a bacteriological 

 examination should be made. It should be the aim to ascertain if death was 

 induced by the inoculated antigen, by contamination or secondary infection. 

 One should always keep in mind the possibility of some of the animal 

 epidemic diseases. 



Epidemic diseases occurring in rabbits are: 



Animal i. RABBIT SEPSIS. Presents itself in the form of bronchopneumonia and 

 Infections, marked nasal catarrh. It is very infectious. Sick animals should at 

 once be isolated or killed and their cages thoroughly disinfected. 

 21 



