FIFTIETH ANNUAL CONVENTION 75 



the pepsin acts only in the presence of an acid, normally 

 hydrochloric, derived from the salts of this acid present in 

 the blood. 



Mineral Compounds Control Life Processes. 



In some mysterious manner, possibly by carrying elec- 

 tric charges which stimulate the body cells, the mineral 

 compounds of the body direct its various vital processes. A 

 simple experiment often performed in the laboratory will 

 illustrate the important functions of the mineral elements 

 in life. If the heart, still beating, is removed from a frog 

 and placed in a solution of pure sodium chlorid (common 

 salt), its beats soon fade out. 



Now if a small amount of a calcium salt (lime) be add- 

 ed to the solution, the heart will at once begin to beat again, 

 and will continue in rhythmical contraction for some time. 

 Unless a small amount of a potassium salt is also added, 

 the beat will not, however, be normal, but the heart will fail 

 to relax quickly and completely enough after each contrac- 

 tion. Therefore, if potassium is not added the relaxations 

 become more and more feeble, until the heart stops in a 

 contracted state. 



Not only must potassium be present, but there must be 

 a correct proportion between the amounts of calcium and 

 potassium. If too much potassium is added, the heart will 

 fail to contract properly, and finally will again stop beat- 

 ing, but this time in a state of complete relaxation. 



Similarly, the other vital processes are dependent not 

 only on the presence of various mineral salts, but also on a 

 proper relationship between them. Therefore it will be 

 seen that unless the amount of these mineral salts in the 

 blood is kept normal, serious consequences will follow. In 

 large measure the kidneys protect the animal against an 

 unbalanced mineral matter content in the blood by prompt- 

 ly excreting any excess of various salts which may be 

 present. 



However, when the food continually furnishes the 

 blood an unbalanced salt mixture, the kidneys may be 

 unable to keep the blood composition normal, with result- 



