570 APPLICATION OF METHODS OF BACTERIOLOGY 



remains make the test for indol by the addition of 10 drops 

 of concentrated sulphuric acid for each 10 c.c. of fluid con- 

 tained in the tube. If comma bacilli are growing in the tube, 

 the rose color characteristic of the presence of indol should 

 appear. 



By following this plan "a bacteriologist who is familiar 

 with the morphological and biological peculiarities of this 

 organism should make a more than probable diagnosis at 

 once by microscopic examination alone, and a positive diag- 

 nosis in from twenty to, at most, twenty-four hours after 

 beginning the examination." (Koch.) 



Since the publication of the foregoing plan many other 

 methods have been suggested. They all comprehend the 

 "enrichment," by special culture methods, of the number 

 of cholera organisms in the original material without at 

 the same time encouraging the multiplication of the other 

 bacteria present, and the subsequent isolation of the cholera 

 organism by the use of selective plating media. Of these 

 methods, the following gives general satisfaction and can be 

 recommended : 



1. Enrichment in the peptone solution exactly as recom- 

 mended above by Koch if it be intestinal contents that are 

 under consideration; if it be water or sewage, then add to 

 90 c.c. of the water or sewage in an Erlinger flask 10 c.c. 

 of a 10 per cent, solution. Keep at 37 to 38 C. for about 

 eight hours. 



2. Without shaking the tube or flask, now transfer one 

 wire loopful from the surface of the mixture of feces, water 

 or sewage and peptone solution, to several tubes containing 

 the Benedict 1 medium : 



Water 1000 c.c. 



Peptone 10 c.c. 



Sodium chloride 5 c.c. 



1 Cent, of Bact., etc., Abt. i, Bd. Ixii, S. 536. 



