CULTURAL CHARACTERS OF BACTERIA 33 



Lbwit's Method of staining Flagella and the Capsules of Bacteria 



See p. 6. 



All bacteria should be studied as to their ability 



1. To stain with standard aqueous solutions of fuchsin or 

 gentian violet (2) ; 



2. With Loffler's methylene blue (3). 



3. If not stained by either of the preceding, try anilin-water 

 fuchsin or gentian violet (4), and Ziehl's carbol-fuchsin (5). 



4. Whether stained or decolorized by Gram's method. 



5. Whether stained or decolorized by Ehrlich's or the Ziehl- 

 Neelsen method as used for tubercle bacilli. 



4. STUDY OF THE CHEMICAL FUNCTIONS OF BACTERIA 

 The Production of Indol and Phenol 



Indol and phenol are products of putrefaction, and are fre- 

 quently produced in bacterial cultures. Their presence or 

 absence is therefore of value in species differentiation. 



Indol production. Inoculate several tubes, each containing 

 10 cc. of bouillon free from glucose, and test for the presence of 

 indol after 5 and 10 days' growth. To 10 cc. of the culture add 

 10 drops of chemically pure concentrated sulphuric acid, and 

 then 1 cc. of a .02 per cent solution of sodium nitrite. If a pink 

 color develops within 10 minutes, indol is present. In record- 

 ing the production of indol it is necessary to state the age of the 

 culture, since indol may be produced in 10 days and not in 5 days. 

 The reaction may appear almost immediately after adding the 

 reagents, or a faint reaction may appear after long standing ; 

 hence the necessity of a time limit for the reaction to manifest 

 itself. Again, the reaction should be allowed to develop at room 

 temperature, since a culture which may show no reaction in the 

 cold may give one when heated. 



Phenol production. A 100 cc. Erlenmeyer flask is connected 

 with a condenser, and 50 cc. of a bouillon culture of the organ- 



