THE MOST COMMON DISEASES OF SWINE ^^47 



tected are injected on the inside of the hind-leg with a 

 suitable dose of the serum alone. This injection will 

 serve to protect hogs from hog cholera for several 

 weeks and, in some cases, for a longer time. But if 

 the hog is not exposed to hog cholera within a few 

 weeks after this treatment, the immunity which is con- 

 ferred by the serum will gradually lessen in degree and 

 the hog may again become susceptible. If, however, 

 the hog is exposed to cholera within a short time after 

 the injection of the serum, the immunity becomes, so 

 far as experiments have shown, of permanent and life- 

 long duration. 



"The injection of the serum alone is especially to be 

 recommended in cases where there is immediate danger 

 of exposure, especially when valuable hogs are carried 

 to fairs, and in herds where the disease has already 

 broken out but has not progressed \ery far. In herbs 

 of this character all of the well animals may be treated, 

 and even in the case of slightly sick animals much good 

 may be accomplished by the serum injection. 



"Su}iiilta)icoits inoculation. — In this form of vaccina- 

 tion the same serum is used as is employed when tlic 

 serum alone is used, but in addition to the serum there 

 is injected on the opposite side of the body, in the same 

 manner as the serum, a very small amount of blood 

 taken from a hog sick of cholera. This simultaneous 

 injection of serum and virulent blood confers upon the 

 injected pig a permanent and lasting immunity, and is 

 therefore to be recominended in cases of well herds 

 which may not be exposed for some months after the 

 treatment. 



