ISOLATING THE TYPHOID BACILLUS. 433 



mented with the following analine dyes : Malachite 

 green, 1 to 1,000,000; brilliant green, 1 to 1,000,000; 

 medicinal methylene-blue, 1 to 100,000 ; methyl violet, 

 1 to 100,000, and crystal violet, 1 to 100,000. Of 

 these the crystal violet gave the most satisfactory result, 

 v. Drigalski and Conradi give the following direc- 

 tions for the preparation of their culture medium : 



a. Preparation of agar : 1500 grams of finely chopped 

 beef are placed in two litres of water and set aside for 

 twenty -four hours. This meat infusion is then boiled for 

 one hour, filtered, and 20 grams of Witte's peptone, 20 

 grammes of nutrose, and 10 grammes of sodium chloride 

 are added and again boiled for an hour, filtered, and 60 

 grammes of agar-agar are added, boiled for three hours 

 (or one hour in the autoclave), rendered slightly alka- 

 line to litmus-paper, filtered, and boiled for one-half 

 hour. 



b. Litmus solution : Litmus solution (according to 

 Kubel and Tiemann) 260 c.c. boiled ten minutes, add 

 30 grammes chemically pure lactose, boil fifteen min- 

 utes. 



c. The hot litmus-lactose solution is added to the hot 

 nutritive agar, thoroughly mixed, and the alkaline reac- 

 tion is again restored. To this medium is then added 

 4 c.c. of a hot sterile solution of 10 per cent, water-free 

 sodium carbonate, 20 c.c. of freshly prepared solution 

 of 0.1 gramme crystal violet (Hochst) in 100 c.c. of 

 warm sterile distilled water. 



One now has a meat-infusion-peptone-nutrose-agar 

 with 13 per cent, of litmus solution and 0.01 per thou- 

 sand crystal violet, which becomes very hard on solidi- 

 fying, without becoming too dry. Plates are poured 

 of this material and held in readiness for some time, and 



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