MATERIALS. 3 1 1 



surface (Fig. 59). Allow them to harden in this position and set aside for 

 future use. Keep this and all other culture media in a cool dark place until 

 used. 



Bouillon. To make bouillon the procedure is as above, except that agar 

 is not added. The other half of the dissolved mixture of water, peptone, 



FIG. 59. Showing method of hardening agar slants. 



salt, and beef extract, in a, is brought to the acidity of 1.5 per cent, in 

 exactly the same way as above described, and, after a boiling (the egg 

 white is not necessary here) the bouillon is filtered through filter-paper, 

 placed in tubes, and sterilized in exactly the same manner as agar medium. 



FIG. 60. A steam sterilizer (Fowler). 



If it is not convenient to use the autoclave, either of these may be 

 sterilized by discontinouus heating as follows: Place the tubes and flask 

 in a steam sterilizer and steam for one-half hour (Fig. 60). Set aside for 

 twenty-four hours and then steam for another half-hour. Set aside once 



