CHAPTER VI. 



Preparation of the tubes, flasks, etc., in which the media are to be 

 preserved. 



WHILE the media are in course of preparation it is 

 well to get the test-tubes and flasks ready for their 

 reception, and it is essential that they should be as clean 

 as it is possible to make them. For this purpose it is 

 advisable that both new tubes and those which have 

 previously been used should be boiled for about thirty 

 to forty-five minutes in a 2 to 3 per cent, solution of 

 common soda ; it is not necessary to be exact as to 

 strength, but it should not be weaker than this. At the 

 end of this time they are to be carefully swabbed out 

 with a cylindrical bristle brush, preferably one with 

 a reed handle (Fig. 21, a), as those with wire handles 



FIG. 21. 



Brushes for cleaning test-tubes. 



are apt to break through the bottoms of the tubes, 

 though Messrs. Lentz & Sons, .of this city, have in 

 large part eliminated this objection from the wire-handle 

 brush depicted in Fig. 21, b. All traces of adherent 



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