72 Elements of Water Bacteriology. 



3. One-tenth gram of crystal violet in 100 c.c. water. 

 Solutions I and 2 are mixed by shaking together in a 

 flask, and the mixture poured into a flask containing 900 

 cubic centimeters of the water to be tested. 10 c.c. of 

 solution 3 are gradually added, and the whole thoroughly 

 mixed by shaking and then incubated at 37 degrees for 

 not over 12-13 hours. At the end of the incubation 

 period loopfuls of the solution are smeared over Drigal- 

 ski-Conradi plates. 



By this method the B. typhi wa§ isolated from mixtures 

 in river water containing one typhoid bacillus to 51,867 

 water bacteria and colon bacilli. 



A number of investigations have shown that the action 

 of the caffein is not as markedly selective as at first 

 claimed. Kloumann (Kloumann, 1904) obtained no 

 better results by this method than by the Drigalski- 

 Conradi medium alone, and Willson (WiUson, 1905) 

 found that certain strains of B. typhi were inhibited, 

 while strains of B. coli developed feebly in the presence 

 of 0.5 per cent of caffein. 



The phenomenon of agglutination was made the basis 

 of a method of isolating B. typhi from water by Adami 

 and Chopin (Adami and Chopin, 1904). Two-liter 

 samples of the water were collected in sterilized bottles 

 (Winchester quarts), and to each was added twenty cubic 

 centimeters of one per cent glucose broth. The sample 

 was incubated for 18 to 24 hours at 37° C, after 

 which ten cubic centimeter portions were withdrawn^ and 



