198 BA CTERIOL OGY. 



only 0.3 per cent, of glucose has been added. Sterilize 

 and inoculate with bacillus coli communis. How do 

 the two tubes differ from one another after eighteen to 

 twenty-four hours in the incubator? First, as regards 

 the reaction of the fluid in the open arms of the tubes. 

 Second, as to accumulation of gas in closed arms of the 

 tubes. Third, as to the capacity of each solution for 

 reducing copper in Fehling's solution. What differ- 

 ences are observed, and how may they be explained? 



INJDOL, PROPUCTIOJ^ The generation of products 

 other tharrtKosethat give rise to alterations in the reac- 

 tion of the media, and whose presence may be detected 

 by chemical reactions, is now a recognized step in the 

 identification of different species of bacteria. Among 

 these products is one that is produced by a number 

 of organisms, and whose presence may easily be de- 

 tected by its characteristic behavior when treated with 

 certain substances. I refer to nitroso-indol, the reac- 

 tions of which were described by Beyer in 1869, and 

 the presence of which as a product of the growth of 

 certain bacteria has since furnished a topic for consid- 

 erable discussion. 



Indol, the name by which this body is now generally 

 known, when acted upon by reducing-agents becomes 

 of a more or less decided rose color. This body was 

 recognized as one of the products of growth of the 

 spirillum of Asiatic cholera first by Poel, and a short 

 time subsequently by Bujwid and by Dunham, and for 

 a time was believed to be peculiarly characteristic of 

 the growth of this organism. It has since been found 

 that there are many other bacteria which also possess 

 the property of producing indol in the course of their 

 development. It is constantly present in putrefying 



