CHEMICAL CHANGES IN PLANTS AND ANIMALS. 



643 



pound of either proteins or carbohydrates as 1860 calories, while 

 that in a pound of fat is equal to 4220 calories. 



It is important to notice that carbohydrates and fats are oxidized 

 to carbon dioxide and water, thus producing the theoretical yield of 

 energy in the body, while only part of the protein molecule is reduced 

 to carbon dioxide and water, the remainder appearing as urea and 

 other nitrogenous bodies possessing latent energy, which must be sub- 

 tracted from the theoretical heat value of the protein. 



Composition and fuel values of several important food materials are 

 given in the following table: 



The relative proportions in which the two kinds of food are taken 

 by animals depend upon the nature of the animal and upon its par- 

 ticular condition of existence. 



Below are given in column A the daily quantity of food required 

 to maintain a grown person in good health, with neither loss nor 

 gain in weight, while the figures in column B refer to the quantities 

 of food for a working man of average height and weight. 



Proteins 125 grammes. 



Fats 79 



Carbohydrates . . . .485 " 

 Inorganic salts . . . .25 " 



Water 2600 



Equivalent to 3050 calories. 



The above nutrients will be furnished by a diet consisting of 1.5 



B. 



130 grammes. 

 85 " 

 400 



30 " 

 2600 " 

 3800 calories. 



