366 DISEASES OF SWINE 



in field work until it had been first thoroughly tested on test shoats 

 to prove that the germs present were not capable of producing 

 blood-poisoning and death of the animal. 



In some plants they are also making these tests by injection of 

 the serum into guinea-pigs, rabbits, and similar laboratory animals. 

 These small pets are very easily affected by the germs of blood- 

 poisoning, and quickly show the effects of their presence by severe 

 reaction and even death. If an injection of the serum into their 

 body produces no bad effects, it is not likely to in the hog. 



How Long May Virus Be Kept? — This is a question which can- 

 not be answered in the same manner as the similar question relative 

 to serum. Virus blood contains a very unstable substance in the 

 form of the virus of cholera, and to get a dependable reaction from 

 this virus blood it is necessary that it be used as soon as possible 

 after being drawn. It should not be used more than fifteen days 

 after being drawn, and, preferably, should be injected within the 

 first seven days after bleeding of the virus pig. 



The opportunity for development of other germs in the virus 

 is more marked than in the case of the serum. Hog-cholera is a 

 disease that is often comphcated by secondary infections of various 

 types, and germs of these diseases may get into the virus in small 

 numbers. The longer the virus is kept, the more these germs mul- 

 tiply, until they are soon present in sufficient amount to produce 

 marked effects when injected. Virus bottles should be labeled so 

 as to show the last date upon which the virus is to be used. After 

 that date it should be destroyed by burning. 



USE OF SERUM IN HOG-CHOLERA 



We have seen in the preceding section that hog-cholera serum 

 is a defibrinated blood obtained from hyperimmune animals as 

 a result of tail bleeding. This fluid carries in it a large amount of 

 germ-fighting substances, known as antibodies. These antibodies 

 are capable, when injected into the body of a healthy animal, 

 of defending that body from an attack by the germs of hog-cholera. 

 We are now ready to take up the methods of using the remedy 

 in actual warfare against hog-cholera. 



In using hog-cholera serum in actual field work there are two 

 principal methods of applying the remedy, both of which have 



