( 'ultural Mi thods 253 



1. Add the corn meal to 500 CC. oi wain and keep healed lo 65 C. lor 

 one hour. Filter through paper. 



2. Dissolve the agar in the remaining .100 cc. <>l water l>\ heating. 



3. \li\ tlu- corn meal and the agar. 



I. Filter through cotton. This is a slow process, and the agar will cool 

 and harden unless the flask is placed in a steam bath or sterilizer. 

 r>. Measure the mixture into test tubes. 



0. Autoclave the tubes for 20 minutes at a pressure of 15 lb. 

 7. Slant the tubes and leave them until the medium is solid. 



POTATO-CARROT AGAR 



This agar is useful in demonstrating the color characteristics ol a colony. 



Carrots 20 Gm. 



Potatoes 20 Gm. 



Vgar 15 Gm. 



Distilled wain 1,000 cc. 



1. Wash and peel the vegetables and cot them into small pieces, then 

 add them to TOO ee. of water and boil the mixture down to 500 cc. Filter 

 through paper. 



2. Dissolve the agar in 500 cc. of water by heating. 



3. Mix the vegetables and the agar. 



4. Measure the mixture into test tubes. 



5. Autoclave the tubes for 20 minutes at a pressure of 15 lb. 



6. Slant the tubes and leave them until the medium is cooled. 



WORT AGAR 



This commercial medium, a Difco product with a pi I of 4.8, is a good 

 substrate for the isolation and differentiation of the yeasts and yeastlike 

 organisms, as it almost entirely eliminates the growth of bacterial con- 

 taminants. This is due to the high hydrogen ion concentration, which, 

 while not harmful to yeastlike fungi, inhibits the growth of bacteria. 



WORT AGAR ENRICHED WITH FAT 

 To freshly made Wort agar, a sufficient quantity of ether extract of 

 crude lanolin or butter is pipetted over the surface and allowed to dry. 

 Benham recommends this agar for the isolation of Pityrosporum ovale. 



ANAERORIC MEDIUM (RREWER) 

 This medium is chiefly used to isolate Actinomyces. 



Pork infusion solids 1.0 Gm. 



Peptone (thio) 1.0 Gm. 



Sodium chloride 0.5 Gm. 



Sodium thioglycollate 0.1 Gm. 



Agar 0.05 Gm. 



Water q.s. ad. 100.0 cc. 



