102 Agricultural Bacteriology. 



Vaccination against anthrax. There are a number 

 of infectious diseases which affect, as a rule, the individ- 

 ual but once. Measles, mumps, and small pox are ex- 

 amples of such diseases in man. The first attack pro- 

 tects the individual against a subsequent one. The exact 

 reason for this protection, which may last during the 

 life of the individual or for a shorter time, is not fully 

 known. This immunity is called " acquired" as opposed 

 to "natural" immunity. Jenner was the first to show 

 in the case of small pox that protection might be pro- 

 duced by artificially inoculating the individual with a 

 weakened virus, that this inoculation was without danger 

 to the individual, and yet protected him from acquiring 

 the virulent disease. The small pox virus is weakened 

 by passing it through the body of a calf so that it is no 

 longer able to produce a general infection but only a sore 

 at the point of inoculation. Later Pasteur discovered 

 that certain other diseases caused by bacteria could be 

 prevented by vaccination. In all cases the vaccine is 

 prepared by the use of the specific organism of the dis- 

 ease in question that has been artificially weakened or 

 reduced in virulence in a variety of ways. These meth- 

 ods will be given under the various diseases for which 

 vaccines are employed. 



In the case of anthrax the vaccine is prepared by grow- 

 ing the anthrax bacillus at a high temperature for several 

 days. This decreases its virulence. It is desirable to 

 have a vaccine of a virulence sufficient to produce a mild 

 fever in the animal, or there will be no immunity pro- 

 duced. 



The vaccine, as used is prepared in a variety of ways. 

 It should be applied only by an experienced veterinarian. 

 Care must be exercised in its use, because in it are living 



