148 BACTERIOLOGY. 



bacillus subtilis require a temperature of 140 C. (dry 

 heat) maintained for three hours to insure their de- 

 struction. Moist heat at a temperature of 100 C., 

 either boiling water or free-flowing steam, destroys 

 the spores of known pathogenic bacteria within ten 

 minutes; certain non-pathogenic species, however, re- 

 sist this temperature for hours. Thus, Globig obtained 

 a bacillus from the soil, the spores of which required 

 five and a half to six hours' exposure to streaming 

 steam for their destruction. These spores survived 

 exposure for three-quarters of an hour in steam under 

 pressure at from 109 to 113 C. They were de- 

 stroyed, however, by exposure for twenty-five minutes 

 in steam at 113 to 116 C. and in two minutes at 

 127 C. 



The resistance of spores to moist heat is tested by 

 suspending cover-glasses upon which the spores (an- 

 thrax) have been dried in little gauze bags in a boiling 

 steam sterilizer. The cover-glasses are removed from 

 minute to minute and laid upon agar plates, which are 

 then placed in the incubator at 37 C. Anthrax spores 

 are obtained by carefully removing sporulating streak 

 cultures on agar and heating the emulsion prepared 

 with a little water to 70 C. for five minutes. 



In the practical application of steam for disinfecting 

 purposes it must be remembered that while steam under 

 pressure is more effective than streaming steam it is 

 scarcely necessary to give it the preference, in view of 

 the fact that all known pathogenic bacteria and their 

 spores are quickly destroyed by the temperature of 

 boiling water, and also that "superheated" steam is 

 less effective than moist steam. When confined steam 

 in pipes is " superheated " it has about the same germi- 



