122 MICROBES, FERMENTS, AND MOULDS. 
materials for effecting oxidation. This is another 
instance of the part played by microbes in artificial 
fermentation. 
Gayon and Dupetit believe that, in addition to 
the microbes which produce nitre, there are others 
which decompose the nitrates produced by the former. 
When nitrate of potassium is placed in culture- 
liquids, drain-water, chicken-broth, etc. it disappears 
rapidly under the action of these microbes. Under 
favourable conditions of temperature and environ- 
ment, culture microbes daily reduce one gramme of 
nitre to the litre. This decomposition causes the dis- 
engagement of nitrogen, the formation of ammonia 
and carbonic acid, which latter remain in solution in 
the form of bicarbonate. Gayon and Dupetit believe 
that this fact explains certain chemical. phenomena 
which occur in the soil, under the influence of manure 
and water. 
Thus fresh discoveries show more clearly every 
day the importance of the part played by microbes 
in nature. Agriculture, manufactures, geology, and 
chemistry must take them into account, since they 
are the active agents of a number of phenomena 
which have hitherto been obscure in physics, 
chemistry, and physiology. 
