r AND ii CULTURE MEDIA 83 



inside of the vessel until all dirt, stains, albumen, and fat 

 are removed. 



(3) Wash thoroughly in hot water, and then with nitric 

 acid. If the flasks or beakers are much stained, allow the 

 acid to act for some little time. 



(4) Rinse thoroughly with tap water and finally with 

 distilled water. 



(5) Allow the vessels to drain ; and when dry, they are 

 ready for sterilisation. 



IV. STERILISATION OF TEST -TUBES, FLASKS, AND 

 BEAKERS. 



Place the tubes and vessels when clean in the hot-air 

 steriliser for half an hour to three quarters of an hour, 

 having previously plugged them with cotton-wool. 



Sterilisation is completed when the cotton-wool plugs 

 turn slightly brown. 



Preparation of Nutrient Media 

 I. PREPARATION OF BEEF BROTH. 



(1) Take one pound of lean beef, remove all fat and 

 connective tissue, and cut it up into small pieces. 



(2) Mince it in a sausage machine or chop it up finely. 



(3) Add 1000 cc. of distilled water and stir vigorously. 

 Then boil for half an hour to one hour in a large flask or 

 in an enamelled iron pan, which must be well covered up. 



(4) Filter, and make the filtrate up to 1000 cc. with 



distilled water. 



