CULTURE MEDIA 43 



Steam for 2 hours, filter while hot, place in ice box over night; filter, add 0.25 

 cc. of i per cent, aqueous sol. neutral red (freshly prepared) and sugar J^ or 

 i per cent. Glucose, dulcite or adonite % per cent. other sugars i per cent. 

 Sterilize in steam sterilizer 10 minutes each day for 2 days. 



Gelatin Medium. 



1. Plain bouillon, 100 cc. 



2. Gelatin (best French leaf), 10 to 30 Gm. 



Break up gelatin, allow it to soak in the bouillon for 5 minutes; then, heat 

 and stir until dissolved and adjust reaction. 



Sterilize in steam sterilizer for 15 minutes each day for 3 days. 



Modifications of gelatin, such as glucose, lactose, saccharose, or other addi- 

 tions and coloring with litmus, are made by adding from i to 2 per cent, of the 

 sugar required and tinting is accomplished by adding sufficient sat. aqueous 

 solution of litmus to give a faint blue tint. 



Agar Medium. 



1. Plain bouillon, 100 cc. 



2. Agar, i to 3 Gm. 



Either shredded or powdered agar may be used, but for most purposes the 

 former is preferable. If shredded agar is used it should be cut into small pieces 

 before putting it into the bouillon. 



Boil and stir until agar is dissolved, add water to make up for the loss by 

 evaporation, adjust reaction and filter in a warm place, as agar solidifies at 

 about 35C. 



Sterilize in autoclave. 



When sugars alone, or sugars and litmus, are added to agar, it is done the 

 same as directed for bouillon and gelatin, and sterilized 15 minutes each day 

 for 3 days. 



Glycerin Agar Medium.- Prepare agar as directed; then, add 6 per cent, 

 glycerin. 



Sterilize in autoclave. 



Russel's Double Sugar Agar Medium. 



1. Plain agar (3 per cent.), 100 cc. 



2. Lactose, i Gm. 



3. Glucose, i Gm. 



Sat. aqueous sol. litmus violet tint. 



Sterilize in tubes in steam sterilizer 15 minutes each day for 2 days and slant. 



Endo's Medium. 



1. Nutrient agar (3 per cent.), 1000 cc. 



2. Lactose, 10 Gm. 



3. Filtered sat. sol. basic fuchsin in 95 per cent, alcohol, 3 cc. 



4. Sodium sulphite solution (10 per cent.), 30 cc. 



Liquefy agar in Arnold steam sterilizer. Dissolve in it the lactose. Test 



