56 PURE CULTURE OF BACTERIA 



A stock of each should be prepared for future use. 



Ex. 25. i. Nutrient Beef Broth (Bouillon). Take i Ib. of 

 lean beef free from fat, chop it up very fine, with a knife or 

 mincing machine. 



Put it in a porcelain dish or glass beaker and pour on it 

 i litre of water. Leave it to soak all night in a cool place, 

 covered from dust. Strain the extract through muslin into a 

 saucepan and boil it for one hour. Filter through filter paper 

 into a large flask and make up the volume to i litre again. Add 

 to it 



Sodium chloride, 5 grams. 

 Witte's peptone, 10 grams. 



Heat the whole in a steam sterilizer or water-bath for an hour, 

 shaking occasionally until all is dissolved. 



Neutralize as in Ex. 17. Heat in steam for quarter of an hour. 

 Neutralize again if necessary and acidify to 4- 10 as in Ex. 17. 

 Filter into sterile flasks or test-tubes. Sterilize in flasks or in 

 tubes for three successive days for twenty minutes each time. 



2. The following varieties of beef broth are occasionally 

 needed : 



Nutrient Beef Broth with Sugars. Add to the above before 

 final filtration 



(i) Milk sugar or lactose, 20 grams, or 

 (ii) Grape sugar or glucose, 20 grams. 



Ex. 26. Lemco's Extract Broth (Bouillon). Dissolve in 

 i litre of water at room temperature 



Lemco's extract of meat, 5 grams. 

 Witte's peptone, 10 grams. 



Neutralize as in Ex. 17. Boil for fifteen minutes, make up to 

 i litre, neutralize again if needed, and acidify to + 10 as in 

 Ex. 17. Boil, filter into sterile flasks or tubes, and then sterilize 

 on three successive days for twenty minutes each time. 



Ex. 27. Nutrient Gelatine. Prepare as in Ex. 17, using 

 (a) Nutrient beef, from Ex. 25, for nutrient medium, or 

 (&) Lemco's extract, as given in Ex. 17 and Ex. 26. 



