46 LABORATORY GUIDE IN BACTERIOLOGY 



to allow liquids to pass through, but no solids or organ- 

 isms. 



I. Arrange a Berkefeld filter so as to connect with 

 the suction pump, and filter a quantity of unsterilized 

 broth (Fig. 24). 



Fig. 24 

 Action of Berkefeld Filter 

 a. Berkefeld filter d. Intercepting flask 



6. Filtered liquid ' e. Connection with aspirator 



t. Side tube with cotton filter /. Rubber hose 



2. Set aside, and observe the results. The filter (a), 

 after being connected with the flask, is steriUzed in the 

 autoclav. The cotton plug at c prevents the air, which 

 is sucked back, from carrying germs. The flask d will 



