FUNCTIONS OF THE NUTRIENTS 155 



be neutralized through the presence of certain basic ele- 

 ments. Sodium, potassium, and calcium function in 

 this relation. If this neutralization did not occur, the 

 animal would be seriously affected and in time die. As a 

 matter of fact acidosis (acid condition) has not been 

 demonstrated with farm animals. The acidity or the 

 alkalinity determines the function of the action of certain 

 enzyms in the digestion of food, as, for instance, while the 

 pepsin of the stomach acts most effectively in an acid 

 solution, the trypsin and other enzyms of the duodenum 

 act only in an alkaline medium. 



223. Relation of mineral elements to osmosis. 

 The transference of substances in solution from one part 

 of the body to another involves the passage of solutions 

 through various membranes and tissues, as, for instance, 

 from the alimentary canal into the blood and from the 

 blood into various tissues which are nourished through 

 such distribution. The penetrability of these membranes 

 seems to be dependent upon the presence of mineral salts. 



224. Relation of mineral elements to muscular con- 

 trol. The contraction of both the voluntary and invol- 

 untary muscles seems to be dependent upon a certain 

 balanced chemical environment involving salts of calcium, 

 magnesium, sodium, and potassium. 



225. Relation of mineral elements to tissue develop- 

 ment. It has been shown that the eggs of certain marine 

 fishes segment normally only in water containing a mix- 

 ture of certain salts of a certain concentration, these 

 being the salts of the alkalies and alkaline earths. 



226. General considerations. It is easily seen that 

 the mineral salts sustain very complex relations to the 

 growth of animal tissue and to the maintenance of animal 

 life. It is a matter of common observation that when an 



