Swine 



419 



enters the system of the hog and causes a reaction which results in 

 immunity like that which is found in hogs that recover from a natural 

 attack of the disease. The serum being given at the same time 

 prevents death or serious sickness which would otherwise be caused 

 by the virus, and through the combined action of these two agents 

 the hogs are rendered immune against cholera for life. 



In administering the simultaneous inoculation the serum is in- 

 jected in the manner already explained, and the virus is injected in 

 the same manner but on the opposite side of the body. The virus, 

 of course, is given in a very small dose as compared with the serum. 

 The doses for simultaneous inoculation are indicated below. 



DOSES OF SERUM AND VIRUS IN SIMULTANEOUS INOCULATION OF 

 HEALTHY HOGS 



If the herd is infected, the dose of serum should be slightly increased 

 for all apparently healthy hogs, and all those showing high temperature 

 or other evidence of disease should receive at least a dose and a half 

 of serum and no virus. 



While the serum alone has the advantage of being harmless, it 

 should be remembered that it has the disadvantage of producing 

 only a transitory immunity. The conditions are precisely reversed 

 in the case of the simultaneous inoculation. In this case the immunity 

 is prolonged, and it is rare to find a hog which has been immunized 

 properly by the simultaneous method which again becomes susceptible 

 to cholera. The principal objection to the simultaneous inoculation 

 is the element of danger caused by the injection of the virus of cholera. 

 If the serum should not be of proper strength, or if a sufficient dose of 

 serum should not be administered, or if the work is not done properly, 

 a case of hog cholera may be produced. Sufficient work, however, 

 has been done to show that the simultaneous inoculation can be ad- 

 ministered with safety. Certain important things are to be re- 



