70 THE MANURE HEAP AND SEWAGE. 
contains the nitrogen which has been actually metabolized by ani- 
mals, and which' can now be brought back readily into a condition 
available for plant life. The liquid manure contains three-fourths 
of the total nitrogen of the whole heap, and four-fifths of the total 
potash. But farmers frequently fail to realize this, and allow this 
material to waste by soaking into the ground. In addition to these 
ingredients manure always contains a large amount of water and 
an unknown number of species and varieties of bacteria in very 
great abundance. 
In this manure the bacteria find plenty of food and moisture 
and their growth is rapid. There is a great struggle for existence 
among them and, in the weeks of fermentation, first one and then 
another species may gain mastery. If the bacterial contents of 
such a mass be studied at intervals, the number and variety of species 
which are most abundant are found to be constantly changing. 
At first the ordinary intestinal bacteria abound; later the putrefactive 
bacteria become most abundant, and finally the denitrifying and 
nitrifying bacteria are in the majority. All of this indicates faintly 
the wonderful complexity of bacterial life and the intensity of the 
struggle for existence among the numerous species originally present 
in the manure. 
Losses from the Manure Pile. The result of this bacteria 
growth is an extensive and profound series of chemical changes 
by which the manure is profoundly modified. These are partly 
useful and partly injurious, but, taken as a whole, they are neces- 
sary. Most of the material in the manure is in a form not capable 
of being used by plants, and must be greatly transformed before it is 
available for vegetation. The transformations are much the same 
as those we have already considered in the soil, but they take place 
under different conditions, which somewhat modify them. In our 
study of the subject it should be borne in mind that the most im- 
portant feature of manuring is the furnishing of nitrogen to the crops, 
and the first care should be to protect this material and avoid its 
loss. 
The losses from manure are due to two causes, i. Leaching. A 
considerable portion of the nitrogen is in a soluble form, including 
