GENERAL MORPHOLOGY AND PHYSIOLOGY. 143 



mentation in solutions of starch, dextrine, and 

 sugar. These bacteria are agents in the ripening 

 of cheese, and the production of sauerkraut. Thus, 

 in a solution neutralised with calcium carbonate : 



2 [Ca(C 3 H 6 3 ) 2 ] + H 2 0=Ca(C 4 H 7 2 ) 2 +CaC0 3 + 3 CO 2 +H 8 . 



In the so-called viscous fermentation the Strep- 

 tococcus viscosus produces a gummy substance in 

 wines. According to Pasteur, the change may 

 be thus represented : 



25(C 12 H 2? O n ) + 25(H 2 O) = i2(C 12 H 20 O 10 ) + 2 4 (C 6 H 14 O 6 ) + 

 i 2 (C0 2 ) + i2(H 2 0). 



and as another example may be mentioned the 

 Bacillus acidi lactici, through whose agency sugar 

 of milk is converted into lactic acid : 



Saprogenic or putrefactive bacteria play a most 

 important role in the economy of nature. They 

 produce changes allied to fermentation in complex 

 organic substances. The nitrification of soil has 

 been attributed to their agency. Their action on 

 proteids, according to Hoppe-Seyler, may be com- 

 pared to digestion ; bodies like peptones are first 

 produced, then leucin, tyrosin, and fatty acids ; 

 lastly indol, phenol, sulphuretted hydrogen, am- 

 monia, carbonic acid, and water. They abstract 

 the elements they require, and the remainder enter 

 into new combinations. Associated with the forma- 

 tion of these substances are certain bodies, which 

 have a poisonous effect when introduced into 



