SYNTHETIC MEDIA 63 
Dissolve cold and add sugar. Add NaCl (8 per cent) if it is to be 
used for luminous bacteria, and an excess of pure CaCOs if acid form- 
ing bacteria are to be grown. 
Prazmowski’s Culture—Fluid. 
Dipotassium phosphate, KeHPO............. 5 gms. 
Magnesium sulphate, MgSO4.-7HeO......... 5 gms. 
Ammonium carbonate, (NH4)eCO3.......... 5 gms. 
Calcium chloride, CaCle.............0 00024. 0.5 gms. 
Distilled water.......... 0.0.00. c cee eee 1000 «c.c. 
Naegeli’s Medium (after Besson, 1913). 
Water... ccc cece eee eens 1000 gms 
Ammonium tartrate.... .......... Lees .. 10 gms. 
Dipotassium phosphate, KoHPO4........... 1 gm. 
Magnesium sulphate, MgSO4-7H2O......... 0.2 gm. 
Calcium chloride, CaClg.................... 0.12 gm. 
Cohn’s Solution. 
Distilled water... 0.0.0.0... cece ees 1000 c.c. 
Dipotassium phosphate, KeHPOQ4........... 5 gms. 
Magnesium sulphate, MgSO.:7H2O......... 5 gms. 
Ammonium tartrate... 02... cee eee eee 10 gms. 
Potassium chloride, KCl................... 0.5 gm. 
Hydrolyzed Casein Medium (Cannon, 1916). Zipfel proposed the 
addition of tryptophane to a synthetic medium for the determination 
of indo] formation. Cannon has realized the high cost of tryptophane 
and suggested the use of a hydrolyzed casein which is prepared as 
follows: Ten grams of casein are hydrolyzed by 200 c.c. of 10 per cent 
sulphuric acid. The mixture is kept on the water bath for twenty- 
four hours after which it is neutralized by saturated barium hydroxide. 
This will precipitate the sulphate. LEvaporate the resulting solution 
until the amino acids crystallize. Half of the preparation is then dis- 
solved in 500 c.c. of Zipfel’s synthetic medium, which has the following 
composition: 
Asparagin... 2.0... 0c cece cee eee eee e eens 5.0 gms. 
Ammonium lactate... 0.2.0.0... cee eee eee 5.0 gms. 
Potassium acid phosphate.................. 2.0 gms. 
Magnesium sulphate................. 00008. 0.2 gm. 
Distilled water... 2.0.0... eee eee ene eee ees 1000.0 gms. 
