152 THE FEEDING OF ANIMALS 



other metabolic changes. The animal body is certainly 

 the seat of greatly varied and complex constructive and 

 destructive activities, which are sustained by the matter 

 and potential energy of the food. How this is done we 

 do not fully understand, but we know many facts which 

 are of great scientific and practical importance and which 

 the feeder must consciously or unconsciously recognize 

 if he would not come into conflict with immutable laws. 

 (See Pars. 236-241.) 



217. Functions of water. Water fills an impor- 

 tant place in the nutrition of all forms of life. In both 

 plants and animals it acts as a solvent of the building- 

 materials which it carries from one part of the organism 

 to another. It also serves as a carrier of wastes, particu- 

 larly those excreted through the kidneys, and the free 

 use of water is recommended as promoting thorough 

 cleansing of the tissues. It is proper to speak of water 

 as building-material for the animal body, for it is an 

 abundant constituent of animal tissue and takes part in 

 chemical changes such as hydrolysis. It fills an essential 

 office in regulating the heat processes of the body through 

 varying rates of evaporation from the surface of the body. 



FUNCTIONS OF THE MINERAL ELEMENTS 



218. Relation of mineral elements to vital processes. 

 The life of an animal is maintained through chemical 

 reactions between substances in solution. These reactions 

 are brought about by means of electrical currents, and 

 the importance of the mineral salts in these relations is 

 seen in the fact that very dilute solutions of the mineral 

 salts in water increase greatly the electrical conductivity. 

 The organic compounds in the body have a low electrical 



