38 BACTERIOLOGY. 



and leather articles, this method is entirely impracticable. 

 In bacteriological work its application is limited to the 

 sterilization of glass- ware principally such, for exam- 

 ple, as flasks, plates, small dishes, test-tubes, pipettes 

 and such metal instruments as are not seriously injured 

 by the high temperature. 



With sterilization by moist heat stea"m the condi- 

 tions are much more favorable. The penetrating action 

 of the steam is not only much more energetic, but the 

 temperature at which this is ordinarily accomplished is, 

 as a rule, not destructive in its action. This is conspic- 

 uously seen in the work of the laboratory. The culture 

 media, composed in the main of decomposable organic 

 materials, which 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 he 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 au 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. 



These differences will be strikingly brought out in 

 the experimental work on this subject. For our purposes 

 it is necessary to say that the two methods have the fol- 

 lowing applications : 



The dry method, at a temperature of 150-180 C., 

 for one hour, is employed for the sterilization of glass- 



