ISOLATION OF SPECIFIC PATHOGEN ES. 55 



probably be accomplished with somewhat less difficulty 

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

 (Schottclius, 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, 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 Ham- 

 burg. 



Koch (Koch, 1893) prescribed the following method 

 for the isolation of the organism from water: 



To ico 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. After intervals of ten, fifteen, and 

 twenty hours the solution is examined microscopically 

 for comma-shaped organisms, and agar plate cultures are 

 made which are likewise incubated at 37. If any 

 colonies showing the characteristic appearance of the 

 cholera bacillus are found, these are examined micro- 



