284 SWINE 



comparatively small hog, — that is 30 to 75 pounds, — it 

 can readily be seen that the expense of this method is an 

 item of considerable importance. Furthermore, the hogs 

 from which this serum is to be obtained must first be ren- 

 dered immune and then hyper-immune, which involves 

 labor and expense and the danger of losing some individ- 

 uals ; besides this the process of manufacturing must be 

 continued indefinitely so as to have the serum on hand 

 for any possible outbreaks of the disease. Although the 

 serum may be kept for a considerable length of time, it 

 is not considered that it will keep indefinitely. When 

 prepared with the carbolic acid solution, and kept in 

 ordinary cellar temperature, it may be preserved for sev- 

 eral months. 



The hyper-immunizing process is dangerous because it 

 requires the use of the virulent hog cholera serum, or 

 serum containing the living hog cholera organisms. 

 When this is used without the protective serum an out- 

 break of hog cholera is immediately started. Thus if this 

 method of treatment is put into the hands of people who 

 are not thoroughly familiar with this sort of work, there 

 is danger of spreading hog cholera broadcast. 



Since the development of this hog cholera serum by the 

 Bureau of Animal Industry of the United States Depart- 

 ment of Agriculture, various state experiment stations 

 have taken up the work and have tried to improve upon 

 it. At different places the method has been somewhat 

 modified. In some cases, the hog in being rendered 

 hyper-immune, is fed the viscera of hog cholera hogs in 

 connection with being inoculated with the virulent hog 

 cholera serum. 



The horse and also the donkey have been used as a 

 means of producing serum that shall have the same prop- 



