THE NUTRITION OF BACTEK1A 



9 



Exercise 8. Preparation of Bouillon 



Two methods of preparation are used by bacteriologists, but 

 method B is more convenient and hence more generally used. It 

 is open to the folloAving objec- 

 tion : Liebig's Beef Extract 

 (the one commonly used) 

 often contains very resistant 

 bacterial spores. Triple steri- 

 lization at 100 C. sometimes 

 fails to kill these organisms; 

 hoAvever, the bouillon can 

 be sterilized by heating to 

 120C. in the autoclave and 

 subsequently used either as 

 a culture medium or as a 

 basis for making up nutrient 

 gelatin, agar, etc. 



FIG. 6. Cotton plugs 



A, correctly made plug; 7> J , shallow plug 



which will be easily displaced; O, plug 



which does not protect the tube from the 



entrance of dust 



B 



1. Add 4g. of Liebig's Beef 

 Extract to 1000 cc. of dis- 

 tilled water. 



2. Place the materials in a 

 flask or agate-ware kettle for 

 cooking. 



1. Place 500 g. of lean 

 chopped beef, free from fat, in 

 1000 cc. of distilled water. S th- 

 an d set in a refrigerator for 

 twelve to twenty-four hours. 



2. Strain the meat water 

 through a piece of clean cheese- 

 cloth. Add distilled Avater to 

 make nitrate up to 1000 cc. 

 Place in a flask or agate-ware 

 kettle for cooking. 



3. Add to either of the above 10 g. peptone and 5 g. sodium 

 chloride. Weigh the vessel containing the solution on a balance 

 and record the weight. 



4. Cook the bouillon on a steam bath or in the Arnold steril- 

 izer fifteen to twenty minutes. Add water to restore to the 

 original weight. 



