BACTERIUM PESTIS. 217 



(b) Indol reaction: After a long time; without the 

 addition of nitrite, slight ; with the addition of nitrite, 

 pronounced. 



(c) Toxins: Fluid cultures, devitalized by heat, never 

 contain soluble toxin. By extraction from cultures eight 

 to twelve weeks old which are killed with formalin, a fluid 

 is obtained which is very rich in toxin, and from this, with 

 ammonium sulphate or alcohol, a solid toxin may be ob- 

 tained, of which T 2wo °f the body-weight is fatal for mice. 

 Still, in the serum of animals treated with large doses of 

 toxin antitoxins are absent (Wernicke, C. B. xxiv, 859). 

 Markl obtained similar results. He obtained the largest 

 quantities of toxin in shallow bouillon cultures quite 

 rapidly (in a few days); he obtained sera with limited 

 antitoxic action, but without any effect against infection 

 with living bacteria (C. B. xxiv, 641). Roux, who pro- 

 duced strongly active sera, found them strongly antitoxic, 

 but not bactericidal. 



Resistance and Viability. — The pest bacillus is not 

 very different from other fission-fungi. It withstands 

 drying from three to seven days ; in water it dies in from 

 three to eight days, according to the composition. In 

 buried bodies the duration of life is from twenty-two to 

 thirty-eight days. Kasansky proved that they stand the 

 Russian winter for months (C. B. xxv, 122). For par- 

 ticulars consult Toptschieff (C. B. xxm, 730), Gladin 

 (C. B. xxiv, 588), Hankin(C. B. xxiv, 587), Wladimiroff 

 (C. B. xxiv, 424). 



Distribution. — (a) Outside the body : In India, Hankin 

 and Yersin have many times cultivated non- virulent varie- 

 ties of bacilli, resembling very much the pest bacillus, 

 from the environs of men in houses infected with pest. 



(6) In healthy body : Never. 



(c) In diseased human body : Is widely distributed. 

 Most abundant in the buboes, primary cutaneous pus- 

 tules, and the sputum of pest pneumonia. Rarely found 

 in the blood and organs (compare below). 



(d ) In animals: Pest occurs spontaneously in rats. 

 Epidemics of pest in rats often precede those in man. It 

 appears as if certain tropical soil bacilli first become accli- 

 mated to the rat's body, and then are transferred to man. 



