BACTERIOLOGICAL TECHNIQUE. 



221 



ent media are stored in large quantities in round or flat- 

 bottomed Erlenmeyer flasks (Fig. 23). From these, as 

 needed, glass tubes (Fig. 24) are filled. Glass dishes 

 with covers (Petri dishes, Fig. 27) and flat flasks are 

 used for growing bacteria in or upon thin layers of 

 media. When small amounts of media are taken fre- 

 quently from flasks, Pasteur's flasks (Fig. 25) are of 



FIG. 24. 



FIG. 23. 



FIG. 25. 



Erlenmeyer flask. 



Pasteur flask. 



Glass test-tubes. 



great convenience. They consist of a flask with a 

 ground-glass neck, over which fits a cap. This cap 

 may or may not terminate, as desired, in a narrow 

 tube, which is plugged with cotton. The cap keeps 

 the edges of the flask free from bacteria and prevents 

 the cotton from sticking. 



