38 



LIQUID MEDIA 



2. Boil for half an hour. 



3. Pour on to a coarse sieve, collect the liquid, and add to it 1 per cent, 

 salt, 2 per cent, ordinary sugar and a pinch of sodium bicarbonate. Boil. 

 Filter through paper. 



4. Tube. Sterilize at 115 C. 



This medium is used by Maze for the cultivation of the micro-organism 

 found in the nodules of leguminous plants. 



Decoction of dried fruits. 



1. Macerate 50-100 grams of dried fruits (prunes or raisins) in a litre 

 of water for several hours. Then stew them in the water. 



2. Pass through a coarse sieve. 



3. Boil. Filter. 



4. Tube. Sterilize at 115 C. 



The liquid is slightly acid and is useful for cultivating moulds. For other 

 purposes neutralize with soda solution before boiling (Stage 3). 



Wine. 



Wine was much used by Pasteur in his early work, but is now hardly 

 ever seen in the laboratory. Before sterilizing, neutralize or make slightly 

 alkaline with soda solution in the ordinary way. 



3. Synthetic media. 



These media, though seldom used in everyday work, have been employed 

 ior the study of certain problems in the biology of micro-organisms. 



The formulse of the best known are given below. Some others will be 

 described in connexion with the organisms in the study of which they have 

 been employed. 



Pasteur's medium. 



Water, - 100 grams. 



Candied sugar, - - 10 ,, 



Ammonium tartrate. - O'lOgram. 



Ash of yeast, - 0'075 



Boil. Filter. Tube. Sterilize. The reaction is alkaline. 



Raulin's medium. 



Water, - 

 Candied sugar, 

 Tartaric acid, 

 Ammonium nitrate, 

 Ammonium phosphate, 

 Potassium carbonate, 

 Magnesium carbonate, 

 Ammonium sulphate, 

 Zinc sulphate, 

 Sulphate of iron, 

 Potassium silicate, 



- 1500 grams. 

 70 

 4 

 4 



P 6 gram. 

 0-6 

 0-4 

 0-25 

 0-07 

 0-07 

 0-07 



Prepare as in the case of Pasteur's medium. 



The reaction is acid. This medium was used by Raulin in his well-known 

 work on Aspergillus niger. 



Cohn's medium. 



Distilled water, 

 Ammonium tartrate, 

 Potassium phosphate, 

 Magnesium sulphate, 

 Tricalcium phosphate, 



200 grams. 

 2 

 1 gram. 



O'lO " 



Prepare as in the case of Pasteur's medium. The reaction is alkaline. 



