STERILIZATION UNDER PRESSURE. 45 



the water in the reservoir becoming exhausted and the 

 consequent destruction of the sterilizer. 



Fig. 2 gives an illustration of this apparatus. 



FIG. 2. 



For sterilization by steam under pressure several 

 special forms of apparatus exist. The principles of 

 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 desirable can be maintained 

 within the sterilizing chamber. These sterilizers are 

 known as " digestors " and also by the French name 

 "autoclav.'' Their construction can best be understood 

 by reference to Fig. 3. 



The dry sterilizers used in laboratories arc simply 

 double- walled boxes of Russian or Swedish iron (Fig. 4), 



a* 



