(\2 EGYPTIAN AGRICi'L 77 '.RK. 



simple bodies which are nearly ready to feed the plants. 

 The decay bacteria cause processes of oxidation and are 

 therefore only active when air has free access to the fer- 

 menting mass. By these bacteria, the products of the life 

 of the putrefactive germs and raw organic matter are 

 converted into simple odourless bodies. Generally, when 

 organic matter is undergoing fermentation the putrefying 

 and decay bacteria are both active, the former in the inside 

 of the mass and the latter on the surface where there is 

 a plentiful supply of air. The fermentation of "Cellulose," 

 the woody part of organic matter, is brought about by a 

 great variety of micro-organisms. The black colour of soil 

 and decomposed organic manure is largely due to the black 

 carbon derived from the dehydration of cellulose. In the 

 presence of air, cellulose is completely oxidised to carbon 

 dioxide and water. When this oxidation of cellulose is 

 going on rapidly, as in a rich manure heap, there is always 

 a very considerable rise in temperature. Through the 

 action of the putrefying, decay, and cellulose bacteria 

 organic matter is at last completely reduced to such simple 

 bodies as water, carbon dioxide, ammonia, and carbonates, 

 sulphates and phosphates of the mineral bases contained in 

 it. The chief nitrogenous compounds in urine are changed 

 to ammonia compounds through the action of certain 

 micro-organisms. This change may take place quickly 

 and the ammonia produced gives a strong ammoniacal 

 odour to stables and manure heaps. The decay, and other 

 bacteria, prepare the ash constituents of organic matter for 

 plant feeding, but the nitrogenous bodies are not available 

 for the plant until they have undergone a further fer- 



