396 The Diseases of Animals 



meters, and the cost per average -sized dose will be 

 about twenty-five cents. Most states have laboratories 

 that supply the serum at cost. 



Owing to the cost of serum, it may not be practical 

 to vaccinate hogs in regions where the disease rarely 

 occurs; but in regions where the disease is frequent, or 

 when the disease appears in a locality, or in animals 

 that are liable to exposure to the infection, the serum 

 should be used. 



The serum is not only a preventive of hog cholera, 

 but assists in curing animals when used in the early 

 stages. In vaccinating a herd, the sick animals should 

 be left until the last, to avoid possible spread of infec- 

 tion by the vaccinating instruments. The serum is 

 injected with a hypodermic syringe, and full directions 

 can be obtained with the serum. 



Hog cholera seems to be caused by an "ultra -micro- 

 scopic" germ, or one so small that it cannot be seen by 

 the most powerful modern microscopes; consequently 

 a rigid quarantine should be maintained against per- 

 sons, as well as animals, from infected places. 



The germs of hog cholera are scattered about by the 

 discharges from sick animals as they are moved over 

 the country. When hogs are shipped in cars, the latter 

 become infested; hence, the necessity of thoroughly 

 disinfecting cars before shipping healthy hogs in them. 

 Streams are frequent sources of infection; it is common 

 to find the disease occurring at farm after farm in 

 succession along a watercourse. The writer has seen 

 the bodies of hogs floating down streams during out- 

 breaks of cholera. Sick hogs are likely to wander 



