88 BACTERIOLOGY 



These sterilizers are known as "digesters" and as "auto- 

 claves." Their construction can best be understood by 

 reference to Figs. 10 and 11. 



Fig. 10 



A B 



Autoclave. A, external appearance; B, section. 



STERILIZATION BY HOT AIR. 



The hot-air sterilizers used in laboratories are simply 

 double-walled boxes of Russian or Swedish iron (Fig. 12), 

 having a double-walled door, which closes tightly, and a 

 heavy copper bottom. They are provided with openings 

 for the escape of the contained air and the entrance of the 

 heated air. The flame, usually from a rose-burner (Fig. 13), 



