I 10 AGRICULTURAL BACTERIOLOGY. 



teria. It will contain large or small amounts of hay or 

 derived from bedding and from the incompletely digested food, 

 especially if horses contribute to its formation. It will likely 

 contain sawdust or some other form of woody tissue. It will be 

 likely to contain more or \essfles/i and bone from dead animals, 

 and will be sure to contain albuminoids, gelatins, fats, sugars, 

 starclies, and indeed nearly z\\ types of organic matter pro- 

 duced by animals or plants, Mid these will be in various states 

 of digestion and decomposiapn. Lastly, and perhaps most 

 important, it will contain large\amounts of nitrogen in the form 

 of urea, or liquid manure, which represent the result of the 

 nitrogenous metabolism of animal life. This liquid manure 

 constitutes undoubtedly one of the most valuable parts of the 

 whole, since it contains all of the nitrogen which has been 

 actually metabolized by animals, and which is in a form to be 

 readily brought back again into a condition available for plant 

 life. Nevertheless, the condition upon our farms is almost al- 

 ways such as to result in a large or almost complete waste of 

 this most useful fertilizer, since it is allowed to soak into the 

 ground without any attempt being made to retain it. In addi- 

 tion to these ingredients manure always contains a large 

 amount of water and an unlimited quantity of bacteria of a 

 wholly unknown number of species and varieties. Some of 

 the material in the manure heap is perhaps already in a form 

 to be used by plants, but the most of it must undergo some 

 important chemical transformations before it can be available 

 for vegetation. 



In this manure the bacteria find most favorable conditions 

 for growth. Plenty of food and moisture are always found and 

 there inevitably occurs a rapid growth of bacteria. There is a 

 great struggle for existence among them and, in the weeks of 

 fermentation, first one and then another species may gain the 

 mastery. If the bacterial contents of such a mass be studied 

 at intervals the number and variety of species which are most 



