THE METABOLISM OF BACTERIA 145 



no means has been devised for their separation or ex- 

 traction. 



End-products of Metabolism. Under this heading 

 are included 



Organic Acids (e. g., lactic, butyric, etc.). 



Alkalies (e. g., ammonia). 



Aromatic Compounds (e. g., indol, phenol). 



Reducing Substances (e. g., those reducing nitrates 

 to nitrites). 



Gases (e. g., sulphuretted hydrogen, carbon dioxide, 

 etc.) . 



And while the discussion of their formation, etc., is 

 beyond the scope of a laboratory handbook, the 

 methods in use for their detection and separation 

 come into the ordinary routine work and will therefore 

 be described (vide page 276 et seq.). 



Jo 



