496 BACTERINS, SERUMS — VACCINES — ANTITOXINS 



Dose. The dosage of tetanus antitoxin varies. An immunizing 

 dose for a horse is usually from 500 — 1500 units. The therapeutic 

 dose ranges from 5000 — 20,000 units. 



The injection of an antitoxin into an animal establishes a passive 

 immunity differing from that produced by the use of vaccines or bac- 

 terins. It is an efficient prophylactic agent, but its therapeutic value 

 is somewhat doubtful. 



SERUMS 



Anti-Hog-Oholera Serum. The method of preparing this 

 product as given by Birch is as follows : 



Process of serum preparation. Immunize a large hog by giving it 

 2 mils of virus and sufficient serum to protect. After it has recov- 

 ered from the slight resulting reaction (in ten days or more) it is 

 ready to hyperimmunize at any subsequent time. 



Hyper immunization. Inject the immune hog intravenously with 

 5 mils of the virus for each pound of body weight. This completes 

 hyperimmunization and the animal is ready to bleed for serum in 

 about ten days. 



Bleeding for serum. This is done under antiseptic conditions 

 from the tail, by cutting off the end. Five mils for each pound of 

 body weight is the usual amount drawn. When the bleeding is fin- 

 ished ligate the tail securely. 



Handling the hlood. Immediately after blood is drawn it is de- 

 fibrinated, and strained through sterile gauze. For each 90 mils of 

 blood there is added, as a preservative, 10 mils of a 5 per cent, solu- 

 tion of phenol. This completes the process of preparation, and the 

 blood, or serum as it is called, is stored in a refrigerator until a test 

 is to be made. Then the combined bleedings from several hogs are 

 mixed in a large container and a sample is drawn for testing. 



Testing the Serum. Eight young susceptible pigs, weighing from 

 30 to 60 pounds each, and preferably from the same litter, are chosen 

 for the test. All are exposed to hog cholera by giving them 2 mils 

 each of virus. Two of the pigs receive 10 mils each of the serum 

 sample to be tested, two receive 15 mils each, and two receive 20 

 mils each of the same sample. Two are given no serima and serve as 

 checks. The pigs are marked for identification, placed together and 

 given like care. The requirements of a satisfactory test are that the 

 pigs receiving virus and no serum shall sicken inside of seven days 

 and reach a dying condition inside of fourteen days; and that they 

 shall, on post-mortem, show marked cholera lesions; that the pigs 

 receiving virus and 10 mils of serum shall remain well or sicken and 

 recover ; that the pigs receiving virus and the larger doses of serum 

 (15 and 20 mils each) shall not show any clinical symptoms of hog 

 cholera except a moderate and transient rise in temperature. 



