INFECTION AND STERILIZATION 



47 



prevent the water from running back and mixing with 

 the filtered liquid. 



Now arrange a cotton filter as shown in Fig. 25. 

 Vessel a, provided with a rubber stopper (b) with two 

 openings, is arranged so as to have a glass tube (c) reach 

 to the bottom. This tube is provided with cotton at 



a. Erlenmeyer flask 



b. Rubber stopper 



c. Glass tube 



d. Cotton filter 



e. Broth 



FIG. 25 

 Action of Cotton Filter 



/. Bent glass tube with cotton filter 



at f. 



g. Erlenmeyer flask 

 h. Tube connecting with aspirator 



the top (d) and some nutritive medium (broth, e) is 

 placed inside. Through the opening a bent glass tube 

 leads out, and this tube is also provided with a cotton 

 filter at /. The whole apparatus is then sterilized in 



