ISOLATING THE TYPHOID BACILLUS. 447 



disturbing organisms, which, however, was not injurious 

 to the typhoid and colon organisms. In the selection 

 of an antiseptic coloring substance they had to be cer- 

 tain that the fermentative properties of the typhoid 

 bacteria were not influenced thereby. They experi- 

 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 : 3 pounds of finely chopped 

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

 twenty-four hours. The meat infusion is boiled for one 

 hour, filtered, and 20 grammes 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. 



6. 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 

 soda, 20 o c. of freshly prepared solution of 0.1 gramme 

 crystal violet (Hochst) in 100 c.c. of warm sterile dis- 

 tilled water. 



