416 



PRINCIPLES OF AGRICULTURAL CHEMISTRY 



A respiration calorimeter is a complicated and expensive ap- 

 paratus, but it secures information regarding the use of nutrients 

 and the nutrition of the animal which is of the highest value, and 

 which can be secured in no other way. 



Fig. 86. Model of respiration calorimeter at the Pennsylvania 

 Station. U. S. D. A. 



Disposition of Food Materials. The carbon which enters an 

 animal in food, is disposed of as follows : 



1 i ) A portion appears as undigested material in the solid 

 excrement. 



(2) A portion escapes as marsh gas and carbon dioxide, pro- 

 duced by fermentation. 



(3) A portion is eliminated as partly oxidized compounds in 

 the urine. 



(4) A portion is eliminated as carbon dioxide in the gases 

 expired from the lungs, being fully oxidized in the body. 



(5) A portion is used in the production of hair, flesh, fat, 

 milk, etc. 



