THE INFLUENCE OF MINERALS 



471 



THE INFLUENCE OF MINERALS, OF FASTING, ETC. 



Mineral Matters, Water, Etc. The chief mineral constituents of 

 the foods are sodium, potassium, calcium, magnesium, and iron, together 

 with chlorine, sulphur, and phosphorus. The inorganic substances are not 

 a source of heat. They may supply a certain amount of energy, as osmotic 

 energy, but this is of no significance as compared with their influence on the 

 metabolism of organic substances. An animal fed on a normal food de- 

 prived of the mineral constituents survives only a few weeks at most. 



The amount of mineral matter in the tissues of the human body, exclusive 

 of the skeletal parts, is about one per cent. It is safe to say that this is 

 chiefly in complex organic combination in the body. The daily quantity 

 excreted is about twenty to thirty grams. This quantity enters the body in 

 the food, chiefly in combination with complex compounds. It is a question 

 as to what per cent, of organic salts, like the calcium, the phosphates, and 

 the iron, is available when taken into the body in inorganic form. 



We have discussed in previous chapters the role of certain salts in their 

 influence on metabolism; for example, of sodium, potassium, calcium, iron, 

 etc. Foods like milk and eggs are especially rich in calcium and phosphorus 

 and are particularly desirable for young children, the former for its influence 

 on the growth of the skeleton, the latter for the same reason and as a stimu- 

 lator of growth of protoplasm in general. Lack of mineral constituents, 

 especially calcium compounds, in food shows its influence on metabolism 

 in the disease known as rickets. 



NUTRITION EXPERIMENT IN FIVE-MONTHS-OLD PIGS. (E. B. FORBES.) 



