DISEASES OF SWINE 457 



from an acute case of the disease) and after such treatment the blood 

 becomes highly charged with antitoxin so that a comparatively small 

 amount of the serum of such blood may be used for the protection 

 of other animals. This process is called hyper-immunizing, the ani- 

 mal so treated being designated as a hyperimmune, and it is this 

 principle that has been taken advantage of so successfully by Drs. 

 Dorset and Niles in the treatment of hog cholera, the results of their 

 work being published in Bulletin 102 of the Bureau of Animal In- 

 dustry. (S. C. B. 152.) 



Use of Immune Hogs. An immune hog is injected with large 

 amounts of blood from hogs sick with hog cholera. These injections 

 will not produce more than a transitory effect upon the health of the 

 immune, although they would prove certainly fatal to a susceptible 

 hog. This treatment of immune hogs with large amounts of viru- 

 lent blood is known as hyperimmunization, and gives to the blood of 

 the immune the power to protect susceptible hogs from hog cholera. 

 After a week or so, when the immune has recovered from the effects 

 of this treatment, blood is drawn from that animal by cutting off the 

 end of the tail. The blood drawing is repeated three or four times 

 at intervals of a week, after which the immune is usually bled to 

 death from a carotid artery. After each drawing from the immune 

 the blood obtained is defibrinated and mixed with a suitable antisep- 

 tic. If preserved in sterile bottles,this defibrinated blood, or serum, 

 as it is called, will retain its potency for years. The protective serum 

 having been obtained from an immune hog in the manner indicated, 

 the potency of this serum is determined by injecting susceptible pigs 

 with varying amounts, and at the same time exposing them to hog 

 cholera along with untreated control animals. In practice it will of 

 course be found best first to collect large quantities of serum and to 

 mix this before testing. A standard serum will thus be secured at a 

 minimum cost. A standard serum of known potency having been se- 

 cured, either of .two methods may be used for protecting susceptible 

 pigs. These are known as (1) the "simultaneous" method, and (2) 

 the "serum-alone" method, or simply the serum method. (B. A. I. 

 25th An. Kept.) 



Practice Briefly Stated. Animals that have recovered from hog 

 cholera or have been immunized by inoculation, are thereafter con- 

 sidered immune. These pigs are then injected with large amounts 

 of blood taken from a hog sick with hog cholera to make them 

 hyper-immune, that is, increasing the properties in their blood to 

 overcome or resist the disease. They are then bled from the tail at 

 intervals of a few weeks. After several bleedings, they are reinocu- 

 lated with virulent blood perpetuating the hyper-immunity. This 

 can be carried on until the tail is consumed when the pig is bled to 

 death ; the blood collected and one-half per cent carbolic acid added 

 to preserve the serum. (N. J. L. S. C. Cir. 1.) 



Details of Serum Production. The hog is first covered with a 

 sterile cloth to prevent any dirt or germs from dropping into the 

 vessel which collects the blood as it is drawn from the animal. The 

 tail is shaved closely, then thoroughly sterilized with a strong anti- 



