154 Biological Therapy 



DOSE OF VIRUS 



At least two c.c. should be used. No greater mistake 

 can be made than to entertain a fear of using too large doses 

 of virus, since Immunity Is directly dependent upon this 

 product. Animals receiving five c.c. of virus will give no 

 more visible reaction than those receiving one c.c. and re- 

 sultant Immunity is more certain. As a matter of fact a dose 

 of one c.c. of virus is more dangerous than one of five c.c. 

 since the smaller dose may fall to overcome the resistance 

 of the animal. When this occurs we fail to confer active 

 immunity, as a result of which a true break may occur at a 

 later period. It should be remembered that immunity is 

 dependent upon virus and that large doses of really virulent 

 virus are absolutely essential to obtain true-lasting im- 

 munity. 



ANTI-HOG CHOLERA SERUM AS A CURATIVE. Al- 

 though this product is not recommended for therapeutic pur- 

 poses, it is frequently the means of saving swine sick with 

 hog cholera. Therefore unless the animal is beyond help it 

 should be injected with liberal doses of serum. In such 

 cases the dose should be at least fifty per cent greater than 

 is recommended for the simultaneous treatment. 



Hog-Cholera Virus 



Many persons, while giving considerable attention to 

 the production and use of anti-hog-cholera serum, fail com- 

 pletely to appreciate the great Importance of hog-cholera 

 virus. While potent serum is necessary to protect swine 

 during the reaction of the simultaneous treatment, the real 

 immunity, which is the desired object of the treatment, is 

 dependent absolutely on the virulency and purity of the virus. 



Virus, unlike most antigens used in developing immu- 

 nity against disease, cannot be grown on artificial culture 

 media. On the contrary it is produced by inoculating sus- 

 ceptible pigs with virulent blood. Approximately seven days 

 later these animals are acutely sick with hog cholera and 

 are then bled from the throat, their blood defibrinated and a 

 preservative added, after which the blood from several ani- 

 mals is mixed to comprise a serial lot of simultaneous virus. 



There is considerable difference in the surroundings 

 under which this product is prepared and the actual tech- 

 nique used in its production. When produced in a crude 



