ISOLATION OF SPECIFIC PATHOGENES 97 



the cholera spirillum and found that the organism would 

 grow abundantly in a solution containing i per cent 

 peptone and 0.5 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 organism from water: 



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

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

 then incubated at 37 degrees. After intervals of 10, 

 15, and 20 hours the solution is examined microscopically 

 for comma-shaped organisms, and agar plate cultures 

 are made which are likewise incubated at 37 degrees. 

 If any colonies showing the characteristic appearance 

 of the cholera spirillum are found, these are examined 

 microscopically, and if comma-shaped organisms are 

 present, inoculations are made into fresh tubes to be 

 further tested by means of the indol reaction and by 

 inoculation into animals. 



Stokes and Hachtel (1912) have suggested the use 

 of a modified Hesse agar containing starch for the 

 isolation of the cholera spirilla, which produce acid on 

 such a medium, while the colon-typhoid organisms do 

 not. The glycerin and lactose are omitted from the 

 medium described on p. 79 and 10 gms. of soluble 

 starch are added. The intestinal spirilla as a class 

 form round, spreading, pinkish colonies on the starch 

 medium, while colonies of other intestinal bacilli remain 



