24 Anthrax. 



animals should be removed to another higher and dryer place. 

 When necessary they should be stabled. Not infrequently a 

 careful investigation of the pasture will disclose dangerous 

 places from which the animals should be kept. In other cases 

 it is possible to suppress an outbreak by the exclusion of pol- 

 luted, muddy watering places. In suspected places the danger- 

 ous character of the soil may be eliminated by draining and 

 cultivation. 



If under existing circumstances the danger of infection 

 cannot be excluded, and the presence of a threatening infec- 

 tion exists, it is advisable to reduce the natural susceptibility 

 of the animals by protective inoculations thereby protecting 

 them from the danger of infection. 



Immunization. Domestic animals may be immunized in 

 practice by attenuated living cultures of the bacilli, by spore- 

 containing- cultures, by immune serum, and finally by immune 

 serum and living cultures. 



I. Immunization with attenuated cultures (Pasteur's 

 method). In 1881 Pasteur established by conclusive experi- 

 ments that anthrax bacilli, when subjected to a temperature 

 of 42-43° C, will continue for a time to multiply actively and 

 no longer form spores. He further found that in such cultures 

 the bacilli die in about a month, but that in the meantime their 

 virulence decreases gradually, and finally he proved that the 

 bacilli, when attenuated to a certain degree, will retain this 

 degree of virulence if their cultivation is continued at body 

 or room temperature. On this experimental observation is 

 based the practical method of protective inoculation worked out 

 by Pasteur with the co-operation of Roux and Chamberland. 



The vaccine is prepared by growing the anthrax bacilli in bouillon 

 at a temperature of 42.5 °C. The cultures which are at first fatal for 

 rabbits, guinea pigs and mice are, after 12 days' growth at the above 

 temperature, attenuated to such degree that they are only exception- 

 ally fatal to rabbits. After an additional 12 days the culture kills 

 only young guinea pigs and mice. After the virulence of the culture 

 has been attenuated to these degrees their cultivation is continued at 

 35-37° C. With such stock cultures fresh liouillon cultures are inocu- 

 lated, and in this manner the vaccine is prepared in any desired (juantity. 



The more attenuated culture represents Pasteur's first, 

 the weaker vaccine, while the less attenuated is the second or 

 stronger vaccine (premier et deuxieme vaccin). The protective 

 inoculation is carried out ])y first injecting subcutaneously the 

 weaker, followed in 10 to 12 days by an injection of the stronger 

 vaccine. The immunization is based on the principle that the 

 first inoculation reduces the natural susceptibility of the animal 

 to such an extent, without endangering life, that it withstands 



