GENERAL SUMMARY OF USE OF SERUM 413 



is used, and the possibility of setting up an inflammation of the 

 testicles in male hogs which might make them incapable of per- 

 forming their duties as breeding animals. 



Other favorite locations for the injection of serum are in the 

 tissues behind the ear and inside the foreleg. Both of these loca- 

 tions are commonly used, especially in full-grown animals or ani- 

 mals that are about ready to go to market. 



(5) Hog-cholera virus which is used with the serum in giving 

 the double treatment is an entirely different substance from hog- 

 cholera serum. It is the blood of an animal which is sick with 

 cholera at the time that the blood is drawn, and it contains enor- 

 mous numbers of the germs of hog-cholera in an active stage of 

 development. These germs are ready and willing to attack any 

 animal into which they may be injected or which they may reach 

 by being scattered about in feed lots where hogs are located. 

 Virus must, on this account, be handled with the most extreme 

 care. 



(6) In using the serum for management of hog-cholera there are 

 two principal methods of use, viz., use of the serum alone, or use 

 of the serum and virus at the same time in the same animal. 



(7) When serum alone is used the animal is protected only just 

 so long as the germ-destroying bodies injected with the serum 

 remain in the body of the animal. Just as soon as this serum has 

 been all worked off the animal is no longer protected. 



The immunity or protection given by serum alone is, therefore, 

 to be classed as a temporary immunity or temporary protection. 



The length of time which this protection derived from the use 

 of the serum-alone method lasts is only about six weeks in the 

 majority of cases. There are a few cases in which animals given 

 the single treatment have been found to be immune even as long 

 as six months after use of the serum. This cannot be depended 

 upon, however, and six weeks is about as long as can be relied upon 

 for protection by this method. 



The reason that the immunity derived from use of serum alone 

 is only temporary is because there is nothing in the serum itself 

 which has the power to teach the cells of the hog how to make germ- 

 destroying bodies for themselves. In order for the cells to learn 

 this art it is necessary that there be the actual entrance into the 



