1'20 



THE CHEMISTKY OF THE FARM 



from time to time in a respiration chamber, the wholo 

 of the air entering and leaving the chamber being 

 measured and analysed. 



Kellner ascertained, by numerous experiments with 

 oxen, the net heat value to the animal of 1 gram of 

 the digestible matter in various foods : his results 

 were as follows : — 



The loss in the urine chiefly depends on the pro- 

 portion of nitrogenous matter in the food, and reaches 

 its maximum in the case of a pure albuminoid, as 

 wheat gluten. The loss of combustible matter, as gas, 

 reaches its maximum in wheat straw, the food most 

 difficult of digestion employed in the experiments. 



For the maintenance of animal life a certain 

 quantity of heat must be developed (p. 178). The heat 

 values ascertained for foods in the manner just described 

 may be used to calculate the amount of food which 

 will suffice for a maintenance ration. When used for 



