14 



satisfactory explanation of them been made. This explanation 

 depends upon the discovery of the existence and the actions, in the 

 manure, of three classes of very small microscopic organisms called 

 bacteria. They are responsible not wholly, but chiefly, for the 

 changes mentioned. Let us note here just what chemical materials 

 are in the manure at the beginning and what they are changed 

 into. 



The fresh manure contains mineral substances like potash and 

 phosphates, and also organic material of two kinds, ntimely: The 

 nitrogenous, found in the liquid manure and to some extent in the 

 solid, and the non-nitrogeuous, which largely makes up the straw, 

 leaves, sawdust, and solid excrement. It is just these two kinds 

 of organic constituents and what they become, which concern us 

 now. 



In those portions of the manure which are accessible to the air, 

 one class of bacteria live and breed in enormous numbers. They 

 feed on the oxygen of the air and the nitrogenous portion of the 

 manure, and, in their excrements, give off large quantities of nitrates, 

 the latter being the direct products of the oxidation of nitrogenous 

 organic matter anywhere, whether in the bodies of these bacteria or 

 not. These nitrates being very soluble in water, drain down into 

 the interior of the manure heap, just as they drain through the soil. 

 But, instead of all going off in the drainage water and becoming lost, 

 as they often do in the soil, they are chiefly lost by an entirely dif- 

 ferent process. 



In the interior of the heap, shut awa}' from the air, these nitrates 

 fall prey to another class of bacteria known as " nitrate destroyers." 

 They completely undo the work of the other bacteria or " nitrate 

 formers." The "nitrate destroyers "live on the non-nitrogenous 

 constituents of the straw and leaves and the oxygen of the nitrates. 

 This liberates the nitrogen in the form of gas which escapes into the 

 air and is lost to the farmer. The process also consumes the non- 

 nitrogenous portion, which is chiefly the remainder of the litter. It 

 is formed into water and carbonic acid gas which escape into the air 

 and thus diminish the bulk of the pile. "While the '• nitrate formers " 

 live near the surface of the manure and require air for their work, 

 the " nitrate destroyers" live away from the air and do not need it. 

 They are dependent, however, on food of a certain kind and must 

 have plenty of it, otherwise they become inactive and can do no 

 damage, though millions of. them may exist in the interior of the 



