CULTURE MEDIA FOR CULTIVATION OF MICROORGANISMS 



683 



2. Tomato. 



3. Agar. 

 Preparation : 



(1) Place small pieces of tomato in a glass 

 jar and add sufficient water to just 

 cover the topmost layer. 



(2) Steam for 2 hours. 



(3) Filter. 



(4) Add 1.6% agar to the filtrate. 

 (.5) Heat at 120°C. for 30 minutes. 



(6) Add 40.0% NaOH to obtain a reaction 

 of a minus 5 on the Eyres scale. 



(7) Filter and resterilize the medium in 

 the autoclave. 



(8) Readjust the reaction to a minus 5. 



(9) Tube while hot. 



Sterilization: Final sterilization not 



specified. 

 Use: Cultivation of streptococci and 



pneumococci. 

 Variants: Green or canned tomatoes may 



be used instead of fresh red ones. 

 Reference: Jenkins (1923 p. 116). 



2113. Graham-Smith's Potato Agar 



Constituents : 



1. Water 500.0 cc. 



2. Potato pulp 500.0 g. 



3. Agar 30.0 g. 



Preparation : 



(1) Wash and peel potatoes and crush 

 in a mincing machine. 



(2) Add water in the ratio of 1.0 g. of 

 potato pulp to 1.0 cc. of water. 



(3) Allow to stand in a flask for 12 hours. 



(4) Filter thru a filter paper. 



(5) The medium may be left in the 

 acid condition or to give an alka- 

 line medium, neutralize the acid 

 with N/1 caustic soda, using litmus 

 as the indicator and then adding 

 3.0 cc. of alkali per liter. 



(6) Treat agar as usual (treatment not 

 • specified) and add 3.0% to (4). 



(7) Place in steam sterilizer at 100°C. 

 until agar is dissolved. 



(8) When cool add white of egg and 

 clarify in the steam sterilizer. 



(9) Filter thru Chardin filter paper. 

 (10) Tube. 



Sterilization: Sterilize on 3 successive days 



in steam at 100°C. 

 Use: Differentiation of diphtheria and 



diphtheria-like bacilli. Author reported 



that diphtheria bacilli colonies after 24 

 hours at 37''C. were either opaque or 

 transparent. Pseudo-bacilli formed me- 

 dium sized, round, whitish, opaque 

 dome shaped colonies. Acid agar clear 

 and opalescent. Alkaline agar clear 

 but of a brownish color. 

 Variants: Thomas (Tanner) prepared a 

 similar medium as follows: 



(1) Wash, pare and slice potatoes. 



(2) Heat one volume of (1) in two 

 volumes of water slowly for 2 hours. 



(3) Boil, after heating for two hours. 



(4) Filter thru cloth. 



(5) Add water to make up the loss due 

 to evaporation. 



(6) Filter. 



(7) Add 1.0% shredded agar to the 

 filtrate. 



(8) Heat in the autoclave for 30 minutes 

 at 15 pounds pressure. 



(9) Filter, if desired, and tube. 

 (10) Sterilization not specified. 



References: Graham-Smith (1904 p. 278), 

 Tanner (1919 p. 61). 



2114. Dawson's Potato Juice Agar 



Constituents : 



1. Water 1000.0 cc. 



2. Agar 20.0 g. 



3. Potato juice 500.0 g. 

 Preparation : 



(1) Use 500.0 g. unskinned potatoes and 

 1000.0 cc. water and obtain potato 

 juice. 



(2) Free juice from starch (method not 

 given). 



(3) Dissolve agar in (2). 

 Sterilization: Not specified. 



Use: To show bacterial variation of B. coli. 

 Reference: Dawson (1919 p. 142). 



2115. Gaehtgens' Potato Agar 



Constituents : 



1. Water 1000.0 cc 



2. Potato 500.0 g. 



3. Agar 



4. NaCl 

 Preparation : 



(1) Carefully wash and peel 500.0 g. 

 potatoes. 



(2) Grind the potatoes fine by means of a 

 porcelain mortar. This is to be 



