SECTION XII. 



THE NUTRIENTS AND THEIR FUNCTIONS. 



The previous sections explained the composition of plants and 

 animals, how food is digested, absorbed and distributed over the 

 body, but we nnust now learn about the nutrients and their 

 functions. 



The Nutrients. — Protein, fats, nitrogen free extract, crude fiber, 

 water and ash serve to supply the needs of animals. Nitrogen 

 free extract and crude fiber are classed as carbohydrates and the 

 digestible amounts in both of these plant substances are regarded 

 as of equal value and supply the same needs in the animal body. 

 Water can be supplied in a cheaper form than in feed stuffs. 

 Protein, fats, carbohydrates and ash therefore are considered as 

 the nutrients. The nutrients and examples of each are: 



{Albumen (white of egg), legumin, casein of milk, washed 

 lean meat, fibrin of blood, gluten of flour, gelatiuoids 

 (gelatin), amides, globulin, peptones, etc. 



{Linseed oil, cotton seed oil, sunflower seed oil, rape seed 

 oil, olive oil, peanut oil, fat of milk, hog lard, mutton 

 suet, beef tallow, fish oil, etc. 



{Starches, sugars (milk sugar, grape sugar, cane sugar, 

 beet sugar, and glucose), glycogen, gums, dextrius, 

 fiber, etc. 



{Sodium carbonate (baking powder), sodium chloride (table 

 salt), carbonate of lime (limestone), magnesium sulphate 

 (Epsom salts), sodium sulphate (Glauber's salts), etc. 



Purpose of the Nutrients. — We want to know the purposes 

 which the nutritive elements serve. In a general way it may be 

 said that animals use food in two ways: i. To build up the 

 body and repair broken down tissues. 2. To produce energy 

 to keep warm and to supply that which gives locomotion or 

 movement to the animal body. 



Functions of Ash or Mineral Matter. — All the bones which 

 ■make up the framework of the animal body contain ash or 

 mineral compounds, and the blood, tissues and the digestive 

 fluids require these substances but to a less extent. Without 

 lime and phosphoric acid it would be impossible to build up the 

 bones to support the animal body. Soda and chlorine are re- 



