176 BACTERIA 



is liquefied, and bubbles of gas are formed in stab cultures. A sour 

 odor is emitted from cultures; i percent to 2 percent of sugar is 

 required for successful cultivation; or 5 percent of glycerine will 

 answer. On agar the growth is marked; gas is produced, and 

 acidous odors evolved. In bouillon it grows rapidly. Large 

 masses of the organism sink to the bottom, gas is formed, and the 

 medium is clouded. Milk affords a good medium for the growth 

 of the organism, but the casein is not coagulated. 



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 rab- 

 bits are not susceptible. Man is immune. It causes in animals 

 peculiar groups of emphysematous crepitating pustules, followed 

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

 broken-down blood. In guinea pigs inoculation is followed by 

 death within thirty-six hours. The site of inoculation is found to be 

 oedematous, and contains bloody fluid. The organs generally 

 are normal. The bacilli are mostly found at the site of the inocu- 

 lation, but later in the blood in every part of the body. The viru- 

 lence 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 organ- 

 ism, 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 com- 

 plete 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 85 C. to 90 C. afforded complete protec- 

 tion to the animal inoculated with them. It is best to use a weaker 

 vaccine muscle that has been heated to 100 C. 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 



