5° 



MANUAL OF BACTERIOLOGY. 



allowed to go to the extent of scorching the cotton; but a faint 

 light browning of the outside is permissible, and is a guarantee 

 that the sterilization is effectual. 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 

 steriUzation is never used for culture-media. 



The apparatus used for hot-air steriHzation consists of a box 



Fig. II. — Hot-air Stekilizer. 



made of sheet-iron, the walls being double, with an air-space 

 between them. On 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 danger of its setting fire to inflammable articles, as the heat 



