28 LABORATORY GUIDE IN BACTERIOLOGY 



5. Sterilize in autoclav for 5 minutes at 120, or in 

 Arnold for 3 consecutive days with 20-30 minutes' 

 exposure. 



EXERCISE VI. PREPARATION OF LITMUS MILK 



i. Separate five-sixths of the cream from the milk. 



FIG. 17 FIG. 18 



Ordinary Style of Potato-Tube Potato-Tube 



a. Potato b. Cotton 



2. Add 7-10 per cent, of a solution of litmus (tincture 

 of litmus). 



3. Distribute about yc.c. into each of twenty-five tubes. 



4. Sterilize in autoclav for 5 minutes at 120, or in 

 Arnold for 3 consecutive days. 



NOTE. The prepared culture media should be carefully 

 stored in a dark, cool place. If they are to be kept for a consid- 



