HOW DOUBLE TREATMENT IS GIVEN 391 



weeks later these same animals are injected with one thousand 

 times the dose of virus which would have killed them before they 

 received the double treatment. As a result of the protective 

 power which these hogs have developed they are now able to 

 receive this large dose of germ-bearing blood, and they show no 

 bad effects from it. As a further proof of the protection which 

 these animals have gained, they can be taken and placed in feed 

 lots with hogs which are sick with cholera and they will not take 

 the disease. Such proofs as these leave absolutely no question 

 as to the benefits to be derived from the double method of treat- 

 ment. 



This is the method of treatment that every well-educated and 

 competent veterinarian and stockman in the United States should 

 advocate. It is just as safe as the single method when used by 

 an educated man who understands the nature of the serum and 

 virus which he is using, and when he is handling a serum and virus 

 both of which have been thoroughly tested. 



How Virus is Tested. — At the same time that the serum is 

 tested the virus should also be tested. This is done in the follow- 

 ing manner: 4 pigs are taken, and 2 are injected with 1 c.c. of 

 virus alone, and receive no protective dose of serum. The other 

 2 receive the same dose of the virus or, better still, 2 c.c. of 

 virus and a proper protective dose of serum, according to their 

 weight. Ten days later the pigs which have received the virus 

 alone should begin to show signs of cholera, or may even be dead 

 if the virus used be of the very powerful variety, such as is used in 

 the Bureau of Animal Industry serum plant, where check pigs 

 are usually killed within six or seven days. The pigs which re- 

 ceived the virus and a protective dose of serum at the same time 

 should show no bad effects at the end of ten days nor at any time 

 following the injection. These tests should be made at the serum 

 plant, and no serum or virus should be allowed to leave the plant 

 until it has been so tested and proved to be just what it claims to be. 



Immunity in Litters. — Not only does the simultaneous method 

 of treatment give a protective power against cholera to the animal 

 so injected, but, as has already been mentioned, it gives the animal 

 the power of transferring to a limited extent this protection to 

 its young. The litters born from sows that have received the 



