ig6 BACTERIA 



Pathogenesis. Young cattle, six months to four years old, 

 sheep, goats, rats, mice, and more especially guinea pigs, are sus- 

 ceptible to it. Swine are immune, while dogs, cats, birds, and 

 rabbits are not susceptible. Man is immune. It causes in ani- 

 mals peculiar groups of emphysematous crepitating pustules, fol- 

 lowed by emaciation and death. These areas contain dark fluid, 

 probably broken-down blood. In guinea pigs inoculation is fol- 

 lowed by death within thirty-six hours. The site of inoculation 

 is found to be cedematous, and contains bloody fluid. The bacilli 

 are mostly found at the site of the inoculation, but later in the 

 blood in every part of the body. The virulence of this organism 

 in culture media is soon lost. The addition of lactic acid to the 

 cultures increases their virulence. 



Immunity. It is possible to decrease the virulence of this 

 organism, and to use the weakened bacteria as a vaccine against 

 infection. To attenuate this bacillus, prolonged exposure to heat, 

 or to heat and drying together is necessary. Inoculation with 

 bacilli treated in this way is followed by a mild local reaction, 

 which affords complete immunity against infection with virulent 

 bacilli. It has been found by Kitt that the muscles of an infected 

 animal, if subjected to a high temperature 85C. to 9o c C. 

 afforded complete protection to the animal inoculated with them. 

 It is best to use a weaker vaccine muscle that has been heated to 

 iooC. for two hours, in order to protect against the active 

 vaccine. Before heating, the meat is ground. When used as an 

 injection, it is crushed and mixed in a mortar with sterile water. 

 Guillod and Simon found that this means of preventative inocula- 

 tion reduced the death rate in unprotected animals from 20 per- 

 cent to 5 percent. If this bacillus, and the prodigiosus bacillus 

 are injected into naturally immune animals, death will often 

 result. 



There is a soluble toxin, anti-toxin against which appears in ' 

 immunized animals. The toxin may be used for prophylaxis. 

 One attack confers immunity. 





