Hog Choleka and Its Peevention. 135 



for its control lies in its prevention rather than in its cure, 

 and this brings us to the discussion of the serum method 

 of treatment, which is distinctly preventive rather than 

 curative in its nature. Success in fighting hog cholera lies 

 in warding it , off rather than in overcoming it after the 

 animals have become diseased. 



To understand this method of procedure it is essential 

 that one has in mind a clear idea of what is meant by im- 

 munity. 



It is common knowledge that when a person has once 

 recovered from an attack of certain contagious diseases 

 he is thereafter less liable to respond to a second attack 

 of those same diseases, and this holds with other animals 

 as well as with human beings. Such individuals, whether 

 persons or other animals, are said to be immune to those 

 particular infections. 



What this immunity consists in is still under debate, I 

 believe, but whatever its nature it is very clear that those 

 animals possess a resisting power they did not possess pre- 

 vious to the first attack of the disease. 



Scientists tell us that all disease-producing germs or bac- 

 teria develop certain toxins or poisons which acting upon 

 the body cells and nerve centers tend to cause death. At 

 the same time that this invasion is going on nature, in her 

 attempt to save life, begins the manufacture of a counter- 

 acting substance, called anti-toxin, the function of which- is 

 the destruction of the living, death-producing microbes 

 and thus stay or limit the progress of the disease. There 

 is, therefore, being carried on within the system of the 

 infected animal a life and death struggle between these 

 two opposing forces, the toxin and the anti-toxin, and the 

 ultimate success of the one or the other means either the 

 death or the recovery of the hog. In the large majority 

 of cases, however, the body becomes so thoroughly impreg- 

 nated with the poisonous germs that the anti-toxin cannot 

 be developed rapidly enough and hence the animal dies. 

 If, on the other hand, the animal has at the beginning an 

 unusual or sufiicient amount of native resisting power, or 

 the infection be not of the more virulent nature, recovery 

 takes place and thereafter the animal is considered, and is 

 in reality, immune. 



