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MANUAL OF BACTERIOLOGY. 



ton. The sterilization should change the cotton to a light 

 brown color, but it should not be scorched to a dark brown. 

 Glassware should be placed within the sterilizer when it is 

 cold, and after heating should be allowed to cool gradually 

 in order to avoid breaking. Hot-air sterilization is never 

 used for culture-media. 



The hot-air sterilizer is a box made of sheet-iron, the 

 walls being double, with an air-space between them. On 



FIG. ii. 



Hot-air sterilizer. 



one side is a door. There are openings at the top to secure 

 the circulation of air in the air-chamber. A thermometer 

 passes from the top into the interior of the sterilizer so 

 that one may read off the temperature that is being attained. 

 The sterilizer should be placed so that there will be no dan- 

 ger of its setting fire to inflammable articles, as the heat 



