CULTURE MEDIA FOR CULTIVATION OF MICROORGANISMS 



547 



lactose is dissolved in a little 

 water, filtered and added to each 

 liter. 



Various fuchsin solutions may- 

 differ and the absolute quantities 

 given above may not be exactly 

 the proper balance in separate 

 lots. These are aproximate, 

 however, and the proper balance 

 can easily be attained by a little 

 preliminary testing in which so- 

 dium sulphite solution is added to 

 small quantities of fuchsin solu- 

 tion in a test tube. 



The finished product is poured 

 into large sterile Petri dishes. 

 The cover is left off until the agar 

 is hard. Smears are made on these 

 plates. 



It is helpful to lay a piece of 

 filter paper into the lid of the 

 petri plate in order to absorb 

 liquid evaporating from the agar 

 in the incubator. If there is 

 not enough filter paper for this, 

 the plate should be placed upside 

 down in the incubator, 

 (p) Committee A.P.H.A. (1923)— Same 

 as for 1917-1920 (variant (h) above) 

 but adjust the reaction to an alka- 

 linity slightly higher than required 

 instead of to +1.0. 

 (q) Stitt. 



(1) Prepare nutrient agar using 5.0 g. 

 Liebig's meat extract, 5.0 g. NaCl, 

 10.0 g. peptone and 30.0 g. agar 

 per 1000.0 cc. water. (Method 

 not given.) 



(2) Adjust the reaction to or +0.2 

 to phenolphthalein. 



(3) Keep this agar base in 100.0 cc. 

 quantities in Erlenmeyer flasks. 



(4) When ready for use melt the agar, 

 and while liquid add 6 drops satu- 

 rated alcoholic solution of basic 

 fuchsin to each flask. 



(5) Then add about 20 drops of a 

 freshly prepared 10.0% solution 

 of sodium sulphite. This de- 

 colorizes the intense red color to a 

 light rose pink. 



(6) Add 5.0 cc. of a freshly prepared 

 hot aqueous 20.0% solution of 

 chemically pure lactose to each 

 flask. 



(7) Mixthoroly. 



(8) Pour into plates. 



[t) Kligler and Defandorfer (Park, Wil- 

 liams and Krumwiede). 



(1) Prepare a beef extract agar. The 

 reaction should be from pH = 7.6 

 to 7.8. 



(2) Sterilize (1) in 100.0 cc. quantities 

 (method not given). 



(3) When desired for use add 1.0 g. of 

 lactose to each bottle. 



(4) Melt the agar. This sterilizes the 

 lactose. 



(5) Add 1.0 cc. of a saturated alco- 

 holic solution of fuchsin to 10.0 

 cc. of a freshly prepared solution 

 of sodium bisulphite. 



(6) Heat in the Arnold sterilizer for 

 30 minutes. 



(7) Add 0.5 cc. of (6) to each bottle of 

 melted agar. 



(8) Pour in plates and allow to harden 

 without the covers. 



(9) Dry in the incubator for 30 

 minutes, protecting the plates 

 from dust. 



(s) Committee A.P.H.A. (1925). 



(1) Add 5.0 g. beef extract, 10.0 g. 

 peptone and 30.0 g. agar (undried 

 market product) to 1000.0 cc. dis- 

 tilled water. 



(2) Boil until the agar is dissolved. 

 This may be done over a free 

 flame with constant stirring or 

 place in the autoclave, in a 

 straight walled container, and 

 autoclave at 15 pounds pressure 

 for 15 minutes. Shut off the steam 

 and allow the agar to stand in the 

 autoclave until it has solidified. 

 Then dump the solidified agar on a 

 clean paper and cut away the 

 sediment. Cut the agar into small 

 pieces and melt. If the agar is 

 dissolved over a free flame, it is 

 necessary to filter thru cotton or 

 cloth. 



(3) Adjust the reaction so that the 

 pH is between 7.8 and 8.2. 



(4) Distribute in 100.0 cc. lots in 

 flasks. 



(5) Sterilize in the autoclave at 15 

 pounds pressure for 15 minutes. 



(6) Prepare a 10.0% solution of basic 



