48 PRACTICAL BACTERIOLOGY 



8. Pour the bouillon into clean tubes (about 10 c. c. in each), or 

 else into small Erlenmeyer flasks, and close with cotton wadding 

 plugs. (In making a cotton wadding plug, twist the cotton together, 

 and when placed in the tube the relaxation of the twist ensures a 

 tight Jit.) ^ 



9. The tubes or flasks are finally sterilized in the steam sterilizer 

 for fifteen to thirty minutes on each of three successive days. The 

 bouillon is ready for use if on cooling it still remains perfectly clear. 



LXXIV. GRAPE SUGAR BOUILLON. 



Put half a gramme of grape sugar into a small Erlenmeyer flask, add 

 100 c. cm. of bouillon after it is filtered, and proceed as in process 

 No. 7, ordinary bouillon, 73. 



MILK SUGAR BOUILLON. 



Prepare the same as grape sugar bouillon, but add 2 per cent, of 

 milk sugar instead of \ per cent, of grape sugar. 



LXXV. GLYCERINE BOUILLON. 



Add 4 to 6 grammes of glycerine to 1 00 c. c. of bouillon either at 

 process No. 3 or at process No. 7, ordinary bouillon, 73, and 

 continue the following processes : 



Instead of using lean beef or veal to make a meat infusion, 

 Liebig's Meat Extract can be substituted, using 10 

 grammes of the extract to 1 litre of distilled water, but 

 the resulting medium is brown coloured, whereas with the 

 meat infusion it is colourless. 



POTATO MEDIA. 



LXXVI. ORDINARY^ METHOD. 



1. Select some good potatoes and wash thoroughly with the 

 potato-brush and water, cutting out any eyes with the potato-knife. 



2. Lay the cleansed potatoes in sublimate solution, (see 66), for 

 thirty minutes. 



3. Sterilize in the steam sterilizer one-half to three quarters of an 

 hour. 



