10 LABORATORY GUIDE IN BACTERIOLOGY 



should enter the hole provided at the bottom of the 

 sterilizer for that purpose. Care should be taken to 

 avoid the possibility of the flame becoming luminous, 

 as this would fill the box and cover the glassware with 

 soot (Figs. 3 and 4). 



The plugged culture-tubes are then placed in the 



Fig. 4 

 Lautenschlager Hot-Air Sterilizer 



sterilizer, and a temperature of 150° is maintained for 

 about 30 minutes, or until the plugs are slightly charred. 

 This can be recognized by a slight brownish color. The 

 tubes are now not necessarily sterile, but the plugs have 

 become set so as to fit the mouth of the tube, and may 

 easily be removed and replaced. 



