366 The Diseases of Animals 



regions where this disease prevails, calves should be 

 vaccinated before the trouble occurs. 



Directions for Using Blackleg Vaccine 



Blackleg vaccine is made from diseased flesh taken 

 from a calf that has died from blackleg. This is cut 

 into thin strips and dried at a temperature of about 

 100° Fahr. It is then ground into fine powder and 

 weakened by heating. Two forms of vaccine are pre- 

 pared: the "single vaccine," which requires but one in- 

 jection or application; and the "double vaccine," which 

 requires two injections about ten days apart. 



The first, or weakest, of the double vaccine is heated 

 for six hours at a temperature of 210° to 212° 

 Fahr. This first vaccine is intended to prepare the 

 animal's system for the second dose, which is very much 

 stronger. The second vaccine is prepared by heating it 

 for six hours at a temperature of 167° to 169° Fahr. 



The single vaccine is of medium strength, and re- 

 quires but a single application. This is made ready by 

 heating the virus for six hours at 197° Fahr. The 

 double vaccine is safer to use and gives better protection 

 than the single, and is generally to be recommended, the 

 only objection being that it requires handling the cattle 

 twice. Single vaccine should not be used on animals 

 that are very fat, as they are especially susceptible to 

 blackleg. In case blackleg has already broken out in 

 a bunch of young cattle, the single vaccine is usually 

 recommended. 



Vaccine is also prepared in the form of a little pill, 



