Isolation of Specific Pathogenes. 71 



while favoring B. typhi, and has been recommended for 

 the isolation of the organism from feces. Doebert 

 (Dcebert, 1900) has shown that certain varieties of mala- 

 chite green are not suited to this purpose. Nowack 

 (Nowack, 1905) has also pointed out the same fact, and 

 ascribed the difference to the' presence of dextrin. He 

 finds that a medium 0.8 per cent alkaline to phenol- 

 phthalein is more favorable to B. typhi and less favor- 

 able to B. coli than one neutral to litmus. With such 

 a medium about 20 per*cent of the typhoid bacilli present 

 develop. 



More recently a considerable degree of success has 

 been attained by methods based upon the inhibitory action 

 of caflein for B. coli. 



This important fact, which was announced by Roth 

 (Roth, 1903), has given rise to much investigation, and 

 offers what is probably the most promising method for the 

 isolation of the typhoid bacillus from water. Hoffmah 

 and Ficker (Hoffman and Ficker, 1904) have developed 

 methods for the isolation of B. typhi from feces and 

 from infected water by its use in connection with nutrose 

 and ctystal violet. For the isolation from infected water 

 solutions are prepared as follows: 



1. Ten grams of nutrose in 80 c.c. of sterilized dis- 

 tilled water. 



2. Five grams caffein, in 20 c.c. sterilized distilled 

 water. 



