50 BACTERIOLOGY. 



to this degree of heat the objects should be subjected for 

 not less than one hour. For the sterilization, therefore, 

 of the organic materials of which the media employed 

 in bacteriological work are composed, and of domestic 

 articles, such as cotton, woollen, wooden, and leather 

 articles, this method is entirely unsuitable. In bac- 

 teriological work its application is limited to the ster- 

 ilization of glassware principally — such, for example, 

 as flasks, plates, small dishes, test-tubes, pipettes — and 

 such metal instruments as are not seriously injured by 

 the high temperature. 



Sterilization by moist heat — steam — offers conditions 

 much more favorable. The penetrating action of the 

 steam is not only more energetic, but the temperature 

 at which sterilization is ordinarily accomplished is, as a 

 rule, not destructive to the obj ects under treatment. Th is 

 is conspicuously seen in the work of the laboratory ; the 

 culture media, composed in the main of decomposable or- 

 ganic materials that would be rendered entirely worthless 

 if exposed to the dry method of sterilization, sustain 

 no injury whatever when intelligently subjected to an 

 equally effective sterilization with steam. The same 

 may be said of cotton and woollen fabrics, bedding, 

 clothing, etc. 



Aside from the relations of the two methods to the 

 materials to be sterilized, their action toward the organ- 

 isms to be destroyed is quite different. The penetrating 

 action of the steam renders it by far the more efficient 

 agent of the two. The spores of several organisms 

 which are killed by an exposure of but a few moments 

 to the action of steam resist the destructive action of 

 dry heat at a higher temperature for a much greater 

 length of time. 



