BACILLUS PESTIS. 483 



bubo for twenty days when unmixed with other 

 organisms (Albrecht and Ghon) ; in the sputum 

 from plague pneumonia for ten days; in various 

 foods, as milk, potatoes, for one to three weeks ; in 

 water from five to twenty days, depending on the 

 number of saprophytes which are present; in earth 

 from two weeks to three months, depending on the 

 quantity of organic matter and other organisms. 

 In all these instances the higher the temperature, 

 i. e., above 30 C., and the more numerous the 

 saprophytic organisms, the shorter is the life of 

 the plague bacillus. In winter, when contaminat- 

 ing saprophytes grow less rapidly, the plague bacil- 

 lus lives longer. Its resistance to desiccation, sun- 

 light and disinfecting agents is rather low, par- 

 ticularly when the surrounding temperature is 

 above 30 C. In temperatures of from 29 to 31 

 C., when thorouhgly dried, it rarely lives longer 

 than from six to seven days, whereas at lower tem- 

 peratures, 16 to 20 C., cultures may be obtained 

 after from one to several weeks, depending on the 

 material which contains the organisms. It lives 

 longer in woolen and cotton threads (clothing) 

 than when isolated as in dust ; hence, dust infection 

 is improbable (Dieudonne). In sputum (plague 

 pneumonia) and purulent exudates in which the 

 bacilli become incrusted to a degree, life may per- 

 sist for from three to four weeks. Sunlight kills 

 them in from two to six hours, depending on the 

 temperature and the proximity of the organisms to 

 the surface. Although cultures for the purpose of 

 vaccination have been killed at a temperature of 

 65 C. for one hour, precautions to insure an even 

 distribution of the heat are necessary to render cer- 

 tain the death of all organisms. A temperature of 



