30 BACTERIOLOGY 



Saccharin Bouillon 



Certain bacteria produce chemical changes in bouillon con- 

 taining glucose, lactose, and saccharose, consisting either in the 

 production of the gaseous products of fermentation, or of 

 organic acids, or both. They are prepared by adding to ordi- 

 nary bouillon I per cent by weight of one or the other of these 

 sugars. In the preparation of lactose and saccharose bouillon ' 

 the original bouillon must be free from muscle sugar. This can 

 easily be tested by inoculating a fermentation tube, containing 

 the plain bouillon, with a gas-producing organism like B. coli. 

 If no gas is produced, the medium is free from muscle sugar. 



Potato 



The potatoes are cut into cylinders with a brass cork 

 borer of the proper size for the tubes, and a couple of inches 

 in length, and then cut across diagonally at an angle of about 

 30 degrees. The pieces are then washed in running water for 

 12 to 18 hours, placed in tubes, and sterilized. 



For the preparation of other and special media, see various 

 text-books on Bacteriology. 



3. THE STAINING OF BACTERIA 



In the examination of the staining properties of bacteria, the 

 following solutions will be necessary : — 



1. Standard alcoholic solutions of the anilin colors, notably 

 fuchsin and gentian violet, made by dissolving 10 g. of the dry 

 color in 100 cc. of 95 per cent alcohol, and filtering. 



2. Standard aqueous solutions of fuchsin and gentian violet, 

 composed of 10 cc. of distilled water and i cc. of the standard 

 alcoholic solution. These solutions should be made fresh. 



3. Loffier's alkaline methylene blue solution. To 100 cc. of 

 distilled water add i cc. of a i per cent caustic potash solution, 



