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DISEASES OF SWINE 



large packing center. Farmers do not care to sell pigs of this 

 weight, as they are just beginning at this age to get to the point 

 where they will show a profit. Last summer it was necessary for 

 the Ames plant to offer as high as 12 and 13 cents a pound for 

 pigs of this weight. As the amount of virus needed is large, and 

 the amount of blood obtainable from a single pig of this weight very 

 small, it can be seen that the cost of production of virus blood in 

 this manner is quite high. In fact, the greatest expense attached 



Fig. 57. — Pens in which hogs are placed for production of virus blood. 

 Similar pens are used for housing of animals used in serum tests. (Photo by 

 H. K. Mulford Co.) 



to the manufacture of hog-cholera serum is the cost of the virus 

 blood. If some means could be devised for cutting down this cost, 

 without decreasing the quality of the virus, there would be a big 

 reduction in the cost of serum treatment. 



Manner of Securing Virus Blood. — The method of securing 

 virus blood by means of injection of susceptible pigs with a virus 

 of known quality is so far superior to other methods that it would 

 seem advisable to give a detailed description of this method: 



