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BACTERIOLOGY. 



dicated is of the author's own construction (see Fig. 37). As a rule, 

 a regulator is not necessary when using the dry-heat sterilizer. 



Fig. 25. Dry-heat sterilizer, double width. In the corners, perforated brass 

 tubes to protect the thermometer and the thermoregulator. 



The time necessary to effect sterilization in the dry- 

 heat oven will, of course, depend upon the temperature. 

 The ordinary laboratory articles are quickly sterilized at 

 150°. When the thermometer indicates 150°, the time 

 should be noted, and this temperature should then be main- 

 tained for % to % oi an hour. Glass tubes and dishes 

 are, therefore, to be sterilized in the dry-heat oven at a 

 temperature of 150-160° for >^-^ of an hour. A tem- 

 perature of 170°, maintained for 15 minutes, will be suffi- 

 cient to effect sterilization. Another procedure is to allow 

 the temperature to rise till it reaches 195°, when the light 

 is turned out. The door of the oven remains closed until 

 the temperature falls below 100°. The cotton plugs in the 



