MANUFACTURE OF HOG-CHOLERA SERUM 353 



carried out to some extent abroad, and also to an even wider degree 

 in American serum plants. It is a system that has found more 

 adoption among the workers in state experiment stations than 

 among commercial firms or the Bureau of Animal Industry. It 

 compares very similarly to the subcutaneous method, and has 

 about the same advantages and disadvantages. 



There is the advantage of comparative ease of injection, and 

 perhaps less danger of producing death in the hands of an inex- 

 perienced operator. The main disadvantages are the frequent 

 formation of large abscesses and even generalized pus infection 

 of the blood-stream. Such animals cannot produce a reliable 

 serum. Abscesses following the intraperitoneal method are if 

 anything even more numerous than in those animals that receive 

 the subcutaneous treatment. This also again interferes with the 

 subsequent sale of the dressed carcass. 



Serum derived from the intraperitoneal method is also likely 

 to be unreliable in protective power. It may or may not prove to 

 be therapeutically active when taken out in the hog-cholera dis- 

 tricts and injected. 



Tail Bleeding For Serum. — After the animal has been hyper- 

 immunized he is placed in the feed lot and allowed the usual atten- 

 tion given to feeding hogs. Food and water of the usual character 

 and amount are provided, and no special attention paid to the 

 animal. It is a good plan to keep a daily record of the tempera- 

 tures in order to see that no undesireable reaction takes place. 

 This daily temperature record may be kept upon the identifica- 

 tion and record card already mentioned, and which was made out 

 at the time the animal was first immunized by the simultaneous 

 method, or, if not used at that time, should be made out at time 

 of hyperimmunization. 



One week after hyperimmunizing, the hog is ready for the first 

 bleeding. Some men wait ten days, but the usual period is one 

 week. Where plenty of time is allowable it may be as well to wait 

 until the tenth day. During this time there has been a severe 

 attack upon the defenses of the body by the toxins of the hog- 

 cholera virus injected in such enormous quantity — many thousand 

 times the fatal dose. The cells have been trained for just such an 

 emergency as this by their experience three weeks previously with 



