84 



BACTERIOLOGY. 



general recognition that almost everywhere this method 

 is supplanting the older one of intermittent sterilization 

 with streaming or live steam. By this plan one is able 

 to accomplish, by a single exposure of fifteen minutes to 

 steam under a pressure of one atmosphere, the same end 

 that would, with streaming .-steam, require three expos- 

 ures of fifteen minutes on each of three successive days. 



FIG. 10. 



Autoclave, pattern of Wiesnegg. A. External appearance. B. Section. 



For sterilization by steam under pressure several spe- 

 cial forms of apparatus exist. The principles involved 

 in them all are, however, the same. They provide for<| 

 the generation of steam in a chamber from which it 

 cannot escape when the apparatus is closed. Upon the 

 cover of this chamber is a safety-valve, which can be 

 regulated so that any degree of pressure (and coinci- 



