I AND ii MODIFICATIONS OF BEEF BROTH 85 



Pour some broth into a sterile separating funnel, and 

 allow 5 to 8 cc. to run into each tube. 



Sterilise these broth-tubes in the steamer, for twenty 

 minutes, on three successive days. 



It is advisable during sterilisation to cover up the tubes 

 with a piece of stout tinfoil, so as to prevent the steam 

 from condensing on the cotton-wool plugs. 



In any case, when nutrient media are to be sterilised 

 in the steamer, care should be taken that the 

 latter is heated up to 100 C. before the tubes or 

 flasks are placed in it. 



Occasionally after sterilisation a slight precipitate 

 appears in the broth. This will settle gradually, 

 and for ordinary purposes may be disregarded. 



II. GLYCERINE BROTH AND GRAPE-SUGAR BROTH. 



(a) Glycerine broth. 



To every 100 cc. of broth add 4 to 6 cc. of pure glycerine, 

 and shake the flask till they are thoroughly mixed. 



Fill sterile test-tubes, arid sterilise them in the usual 

 manner. 



(b) Grape-sugar broth. 



To every 100 cc. of broth add 2 grammes of grape-sugar. 



When the sugar is quite dissolved, fill a number of 

 sterile test-tubes, and sterilise them in the usual manner. 



Glycerine broth is used for the cultivation of tubercle 

 bacilli, and grape-sugar broth for anaerobic cultiva- 

 tion. 



