io FOOD-GRAINS OF INDIA. 



that of building up and renewing the blood and tissues of the 

 body. The "potential" energy laid up in each of the combustible 

 nutrients is capable of being set free as actual or kinetic energy, 

 when the nutrient, after digestion, absorption, and assimilation, is 

 oxidized in the organism by means of the oxygen taken into the 

 lungs. But the nitrogenous nutrients alone are capable of trans- 

 formation into the very substance of the nitrogenous tissues 

 themselves. 



CHEMICAL AND PHYSIOLOGICAL CLASSIFICATION 



OF FOOD. 



CLASS I. NUTRIENTS. 

 DIVISION I. INCOMBUSTIBLE COMPOUNDS. 



i. WATER : The carrier of nutritive materials and waste products ; 

 forms an essential part of all tissues. 



ii. SALTS OR MINERAL MATTER : Such as common salt and 

 phosphate of lime, which serve to effect solution and 

 change, and to build up certain tissues. 



DIVISION II. COMBUSTIBLE COMPOUNDS. 



iii. CARBON-COMPOUNDS, such as starch, sugar, and oil, which serve 

 to keep up the heat, and do the work of the body by 

 the discharge of their potential energy during oxidation 

 in the organism. The fat of the body is formed in part 

 from the fat or oil in the food ; in part from the starch 

 and sugar. Gum, mucilage, pectose, etc., belong here. 



iv. NITROGEN-COMPOUNDS, such as albumen, fibrin, and legumin, the 

 chief formative and reparative compounds of food ; 

 they may also yield fat, and by their oxidation set free 

 heat and actual energy. Hereafter we shall call them 

 " albuminoids." 



