80 ELEMENTS OF WATER BACTERIOLOGY 



37 degrees for not over 12-13 hours. At the end of the 

 incubation period loopfuls of the solution were smeared 

 over Drigalski-Conradi plates. 



By this method the B. typhi was 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 (Willson, 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. 



In this country marked success in the isolation of 

 the typhoid bacillus has been attained by the use of 

 lactose bile as an enrichment medium. Jackson (Jack- 

 son and Melia, 1909), the principal exponent of this 

 procedure, recommends that sterilized undiluted fresh 

 ox gall (or an II per cent solution of dry fresh ox gall) 

 containing i per cent of peptone and i per cent of 

 lactose be made up in 40 c.c. amounts in fermen- 

 tation tubes to which varying amounts of water, up 

 to 10 c.c. may be added. After incubation for 48 

 or 72 hours, he plates on Hesse agar and he finds 

 that in the bile medium B. typhi tends to over- 

 grow B. coli while most other organisms are entirely 

 suppressed. 



Dr. Krumwiede has found brilliant green broth 

 useful as an enrichment medium for the isolation of 



