366 The Diseases of Animals 
regious where this disease prevails, calves should be 
vaccinated before the trouble occurs. 
Directions for Using Bluckleg 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, 
