46 



BACTERIOLOGY 

 FIG. 3. 



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

 a heavy copper bottom. They are arranged with venti- 

 lating openings for the escape of the contained air and 

 the entrance of the heated air. The flame, usually from 

 a rose burner (Fig. 5), is applied directly to the bottom. 

 The heat circulates from the lower surface around about 

 the apparatus through the space between its walls. 



The construction of the copper bottom of the appa- 

 ratus upon which the flame impinges, is designed to 

 prevent the direct action of the flame upon the sheet- 



