136 SOILS AND FERTILIZERS 



INCREASE DURING FATTENING. 



Dry Nitrogenous 



Water. matter. Fat. matter. Ash. 



Ox . 24.6 75.4 66.2 7.69 1.47 



Sheep 20.1 79.9 70.4 7.13 2.36 



Pig 22.0 78.0 71.5 6.44 0.06 



The results of numerous digestion experiments 

 show that when the food undergoes digestion from 5 

 to 15 per cent, of the nitrogen is, as a rule, retained 

 in the body. The nitrogen of the food is utilized 

 largely to replace that which has been required for 

 vital functions. The nitrogen of the food enters the 

 body, undergoes digestion changes, is utilized for 

 some vital function, and is then voided in the excre- 

 ments. 



The digestion of food has been compared to the 

 combustion of fuel : the undigested products of the 

 solid excrements represent the ashes, and the urine 

 represents the volatile products. When wood is burn- 

 ed the nitrogen is converted into volatile products. 

 When food is digested and utilized by the body the 

 digestible nitrogen is mainly converted into urea, 

 while the indigestible nitrogen is voided in the dung. 

 In the solid and liquid excrements of animals, from 

 80 to 95 per cent, of the nitrogen, phosphoric acid 

 and potash of the food are present. 



171. Composition of Solid and Liquid Excrements 

 Compared. In composition the liquid excrements 

 .differ from the solids in having a much larger amount 

 (.of nitrogen and less phosphoric acid. 56 



