86 THE CHEMISTRY OF THE FARM. 



ui-ea and salts by the kidneys ; water by all the organs 

 of excretion. 



Non-nitrogenous substances, as fat and sugar, when 

 oxidised in the body, yield simply water and carbonic 

 acid. The nitrogen of the albuminoids, gelatinoids, and 

 amides, is not oxidised, but is excreted in the form of 

 urea. The sulphur of the albuminoids is in part 

 oxidised to sulphuric acid. 



The quantity of nitrogen in the urine is a measure of 

 the albuminoids, gelatinoids, and amides oxidised in the 

 body. In the urine, and in the perspiration of the skin, 

 are also removed all the salts not required for the animal 

 economy. Sodium and potassium salts are generally 

 abundant in the urine. 



The solid excrement contains the undigested part of 

 the food, with the residues of the bile and other secre- 

 tions of the alimentary canal. 



