92 BACTERIOLOGY 



is applied directly to the bottom. The heat circulates from 

 the lower surface around about the apparatus through the 

 space between its walls. 



FIG. 11 



Autoclave or digester for sterilizing by steam under pressure. 



The construction of the copper bottom of the apparatus 

 upon which the flame impinges is designed to prevent the 

 direct action of the flame upon the sheet-iron bottom of the 

 chamber. It consists of several copper plates placed one 



