MANUFACTURE OF HOG-CHOLERA SERUM 359 



remain. The next best plan is to take such measures as will pre- 

 vent their growth in large numbers. This is done by addition of 

 the small amount of carbolic acid, and. also by keeping the serum 

 in a cold place away from the hght. Moderately warm temperature 

 and light are two of the essentials to germ growth, and when fluids 

 containing germs are kept cold there is very little growth on the 

 part of the germs. 



Rehyperimmunizing and Repeated Bleedings.— After the three 

 tail bleedings above referred to, the animal is reinjected with virus 

 blood, as just described, and again placed back in the pen. One 

 week later he is ready for another bleeding. This new dose of the 

 virus of the disease has served to further stimulate the action of 

 the body cells, and they have turned out an even larger army of 

 antibodies. This again ensures a serum that will be of a high 

 standard of potency. 



Following this hyperimmunizing process the animal is bled twice 

 from the tail, and is now ready for the termination of the bleed- 

 ing process, with a final bleeding and death of the hyperimmune. 

 At this time the animal is brought into the operating room and 

 placed on the table, as in the case of bleeding of pigs for virus blood. 

 The neck is washed and shaved and the large vessels of this region 

 are then exposed by an incision, and the blood withdrawn in the 

 same manner as described in obtaining virus blood. 



At this bleeding all the blood possible to obtain is withdrawn. 

 The amount obtained will differ considerably in various animals, 

 even of the same weight. As a rule, several thousand cubic 

 centimeters are obtained. This is then treated in the same manner 

 as that withdrawn through the tail. It is shaken, the clot filtered 

 off, a small amount of carbolic acid added as a preservative, and 

 then bottled and kept in a cool place. 



The carcass is then dressed in the usual manner, and should 

 be inspected at this time by a United States or city inspector, and, 

 if there is no evidence of disease present, the meat can be passed 

 for food. Those that show presence of disease should be con- 

 demned and sent to the rendering tanks to be made into grease 

 or fertiUzer. 



