330 



BUILDINGS, SANITATION, AND DISEASES 



Immunization. To the investigations of the Bureau of 

 Animal Industry of the U. S. Department of Agriculture, we 

 are indebted for the production of a. serum which seems likely 

 to play an important part in the suppression of hog cholera. 

 Briefly, the serum is prepared from the blood of hogs treated in 

 such a way as to render them immune from the disease. The 



Courtesy Tennessee Department of Agriculture. 



FIG. 94. Injecting serum into muscle of ham (pig). 



serum is injected under the skin of healthy hogs which it is 

 desired to protect from the disease. (Figs. 93, 94, 95.) It 

 is not a cure for cholera, but is wholly preventive in character, 

 bearing the same relation to hog cholera as vaccine bears to 

 smallpox. 



In an address before the American Veterinary Medical 



