BACTERIOLOGY. 



burner. It is employed for sterilising nutrient 



media in tubes or flasks, 

 for cooking potatoes, or 

 hastening the filtration 

 of agar-agar. When 

 the thermometer indi- 

 cates 1 00 C. the lid is 

 removed, and test-tubes 

 are lowered in a wire 

 basket by means of a 

 hook and string, and 

 the lid quickly replaced. 

 FIG. 2. -HOT-AIR STERILISER. Potatoes or small flasks 



are lowered into the cylinder in a tin receiver with 

 a perforated bottom, which rests 

 upon the grating and admits of 

 its contents being exposed to 

 the steam. 



Hot-air Steriliser. A cubi- 

 cal chest of sheet iron with 

 double walls, supported on four 

 legs ; it may also be suspended 

 on the wall of the laboratory, 

 with a sheet of asbestos inter- 

 vening (Figs. 2 and 3). It is 

 heated with a rose gas-burner 

 from below, and the temperature 

 of the interior indicated by a 

 thermometer inserted through 

 a hole in the roof; in a second 



uy^tlJ-Ls 



