10 LABORATORY GUIDE IN BACTERIOLOGY 



at a temperature of 150° C. for about 30 minutes, or 

 until the plugs are slightly browned. The tubes are 

 not necessarily sterile, but the plugs have become set 

 so as to fit the mouth of the tube, and may be removed 

 and replaced readily. 



SECTION 4 



METHODS OF STERILIZATION 



Sterilization is the process of removing all living 

 organisms. This may be accomplished by heat, by 



Fig. 3 

 Berkefeld Filter 

 o. Berkefeld filter d. Intercepting flask 



b. Filtered liquid e. Connection with aspirator 



(.. Side tube with cotton filter /, Rubber hose 



