XI. CULTURE MEDIA. 



ORDINARY OR STOCK MEDIA. 



Nutrient Bouillon. 



1 . Measure out double strength meat extract, 500 c.c., 

 into a litre flask and add 300 c.c. distilled water. 



2. Weigh out Witte's peptone, 10 grammes (= i per 

 cent.), salt, 5 grammes (=0.5 per cent.), and mix into 

 a smooth paste with 200 c.c. of distilled water pre- 

 viously heated to 60 C. (Be careful to leave no un- 

 broken globular masses of peptone.) 



. 3. Add the peptone emulsion to the meat extract in 

 the flask and heat in the steamer for forty-five minutes 

 (to completely dissolve the peptone, and to render the 

 acidity of the meat extract stable) . 



4. Estimate the reaction of the medium; control the 

 result; render the reaction of the finished medium 

 + io (vide page 155). 



5. Heat for half an hour in the steamer at 100 

 C. (to complete the precipitation of the phosphates, 

 etc.). 



6. Filter through Swedish filter paper into a sterile 

 flask. 



7. Fill into sterile tubes (10 c.c. in each tube). 



8. Sterilise in the steamer for twenty minutes on 

 each of three consecutive days i. e., by the discon- 

 tinuous method (vide page 35). 



NOTE. As an alternative method when neither fresh nor frozen 

 meat is available nutrient bouillon may be prepared from a com- 

 mercial meat extract, as follows: 



Lemco Broth. 



1. Measure out 250 c.c. distilled water into a litre flask. 



2. Weigh out 10 grammes Liebig's Lemco Meat Extract on a 



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