180 BACTERIOLOGY. 



From what has been said it may be inferred that the 

 cultivation of anaerobic bacteria is a simple matter and 

 attended with but little difficulty. Such an inference 

 will, however, be quickly dispelled when the beginner 

 attempts this part of his work for the first time, and 

 particularly when his effisrts are directed toward the 

 isolation of these forms from other organisms with 

 which they are associated. The presence of spore- 

 forming, facultative anaerobes in mixed cultures is 

 always to be suspected, and it is this group that renders 

 the task so difficult. At best the work requires undi- 

 vided attention and no small degree of skill in bacterio- 

 logical technique. 



Indol PeodugtiOjST. — The production of products 

 other than those which give rise to alterations in the 

 reaction of the media, and whose presence may be de- 

 tected by chemical reactions, is now a recognized step 

 In the identification of different species of bacteria. 

 Among these chemical products there is one which is 

 produced by a number of organisms, and whose presence 

 may easily be detected by its characteristic behavior 

 when treated with certain substances. I refer to the 

 body nitroso-indol, the reactions of which were described 

 by Beyer in 1869, and the presence of which as a pro- 

 duct of growth of certain bacteria has since furnished a 

 topic for considerable discussion. 



Indol, the name by which this body is now generally 

 known, when acted upon by reducing agents, is seen to 

 become of a more or less conspicuous 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 thought to be peculiarly character- 



