466 BACTERIOLOGY. 



to unfavorable nutritive conditions than to the direct 

 action of the other organisms present. 



When completely dried, according to Koch, the 

 cholera spirillum does not retain its vitality longer 

 than twenty-four hours, but by others its vitality is 

 said to be destroyed by an absolute drying of three 

 hours. In moist conditions, as in artificial cultures, 

 vitality may be retained for many months ; though re- 

 peated observations lead us to believe that under these 

 circumstances virulence is diminished. According to 

 Kitasato,' they retain their vitality when smeared upon 

 thin glass cover-slips and kept in the moist chamber 

 for from 85 to 100 days, and for as long as 200 days 

 ^^hen deposited upon bits of silk thread. 



In the course of his studies upon the persistency of 

 pathogenic micro-organisms in the dead body von 

 Esmarch ^ found that when the cadaver of a guinea- 

 jiig dead after the introduction of cholera organisms 

 into the stomach was immersed in water until decom- 

 position set in, after eleven days, when decomposi- 

 tion was far advanced, it was impossible to find any 

 living cholera spirilla by the ordinary plate methods. 



A similar experiment resulted in their disappearance 

 in five days. In another experiment, in which de- 

 composition was allowed to go on without the animal 

 being immersed in water, none could be detected after 

 the fifth day. 



Carl Frankel ' has shown that an atmosphere of car- 

 bonic acid is directly inhibitory to the development of 

 tlie cholera spirillum, and Percy Frankland * states that 

 in an atmosphere of this gas it dies in about eight days. 



1 Zeitschrift fiir Hygiene, Bd. v. S. 134. ' Ibid., Bd. vil, S. 1. 



3 Ibid., Bd. V. S. 332. * Ibid., Bd. vi. S. 13. 



