UTILIZATION OF FOOD 419 



and possibly other compounds. All these substances are incom- 

 pletely oxidized, and represent a loss of energy from the food. 

 Non-nitrogenous organic substances are also present in the urine. 

 For example, the following is an analysis of the urine of a 

 sheep : 



Water 86.48 



Urea 2.21 



Hippuric acid 3.24 



Ammonia 0.02 



Carbonic acid 0.42 



Other organic substances 2.07 



Ash 5.56 



The effect of various substances upon the urine may be studied 

 by determining the amount and composition of the urine with a 

 given ration, adding the substance to be studied to the ration, and 

 determining the change in the urine caused by the addition. This 

 effect is usually expressed in terms of energy (calories). Kell- 

 ner, 1 assuming that only the proteids fed affected the loss of 

 energy in the urine, obtained the following results with certain 

 concentrates : 



Average energy in i gram digested proteids, Calories 5.71 



Average loss of energy in urine from i gram, Calories 1.29 



Average percentage loss of energy in urine 22.6 



Maximum percentage loss (with linseed meal) 26.6 



Minimum percentage loss (with gluten meal) 18.9 



The assumption of Kellner, however, is not correct, since the 

 other constituents of the food have some effect upon the loss of 

 energy in the urine. Only traces of sugar or pentosans are found 

 in normal urine, but an addition of roughage to a ration increases 

 the loss of energy in the urine to a considerably greater extent 

 than the addition of an equal quantity of protein in the con- 

 centrated feeding-stuffs mentioned above. Sometimes the in- 

 creased loss is greater than the quantity of energy in the proteids 

 fed in the roughage. Non-nitrogenous substances, therefore, 

 1 Die Ernahrung d. Landw. Niitzture, p. 83. 



