Il8 THE STORY OF GERM LIFE. 



readily explained by the facts already considered. 

 The fresh animal secretions consist of various 

 highly complex compounds of nitrogen, and the 

 ripening is a process of their decomposition. The 

 proteids are broken to pieces, and their nitrogen 

 elements reduced to the form of nitrates, leucin, 

 etc., or even to ammonia or free nitrogen. Fur- 

 ther, a second process occurs, the process of 

 oxidation of these nitrogen compounds already 

 noticed, and the ammonia and nitrites resulting 

 from the decomposition are built into nitrates. 

 In short, in this ripening manure the processes 

 noticed in the first part of this chapter are taking 

 place, by which the complex nitrogenous bodies 

 are first reduced and then oxidized to form plant 

 food. The ripening of manure is both an ana- 

 lytical and a synthetical process. By the analy- 

 sis, proteids and other bodies are broken into very 

 simple compounds, some of them, indeed, being 

 dissipated into the air, but other portions are re- 

 tained and then oxidized, and these latter become 

 the real fertilizing materials. Through the agency 

 of bacteria the compost heap thus becomes the 

 great source of plant food to the farmer. Into 

 this compost heap he throws garbage, straw, vege- 

 table and animal substances in general, or any 

 organic refuse which may be at hand. The vari- 

 ous bacteria seize it all, and cause the decomposi- 

 tion which converts it into plant food again. The 

 rotting of the compost heap is thus a gigantic 

 cultivation of bacteria. 



This knowledge of the ripening process is fur- 

 ther teaching the farmer how to prevent waste. 

 In the ordinary decomposition of the compost 

 heap not an inconsiderable portion of the nitro- 

 gen is lost in the air by dissipation as ammonia 



