Isolation of Specific Pathogenes. 83 



bacillus, however desirable theoretically, cannot be re- 

 garded at present as generally profitable. 



The isolation of the ■ cholera bacillus from water can 

 .probably be accomplished with somewhat less difficulty 

 than is encountered in the case of B. typhi. Schottelius 

 (Schottelius, 1885) was the first to point out the necessity 

 for growing this organism in an alkaline medium, and 

 Loeffler (Loeffler, 1893) found that its isolation from 

 water could be successfully accomplished by adding 10 c.c. 

 of alkaline peptone broth to 200 c.c. of the infected water 

 and incubating for twenty-four hours at 37 degrees, when 

 the organism could be found at the surface of the medium. 



Somewhat earlier than this Dunham (Dunham, 1887) 

 had made a special study of the chemical reactions of the 

 cholera bacillus and found that the organism would grow 

 abundantly in a solution containing i per cent peptone 

 and ^5 per cent salt (Dunham's solution), producing the 

 " cholera-red or nitroso-indol reaction." This medium 

 was brought into practical use by Dunbar (Dunbar, 1892), 

 who succeeded in isolating the organisms from the water 

 of the Elbe in 1892, during the cholera epidemic at 

 Hamburg. 



Koch (Koch, 1893) prescribed the following method for 

 the isolation of the organisih from water: 



To 100 c.c. of the water to be examined is added i 

 per cent peptone and i per cent salt. The mixture is 

 then incubated at 37 degrees. After intervals of ten, 

 fifteen, and twenty hours, the solution is examined micro- 



