THE CHEMISTRY OF FOOD 77 



4. Inorganic Substances. The substances we use as food 

 are classified as organic and inorganic. By organic substances 

 are meant those derived from living forms, such as vegetables 

 and animals. Inorganic substances are those simpler inani- 

 mate forms which belong to the mineral kingdom. The former 

 alone are commonly spoken of as food; but the latter enter 

 very largely into the constitution of the body, and must there- 

 fore be present in our food. With the exception of two articles 

 water and common salt these substances enter the system 

 only when blended with organic substances. 



5. Water. Water, from a physiological point of view, is 

 the most important of all the articles of food. It is every- 

 where found in the body, even in the bones and the teeth. It 

 has been computed that as large a proportion as two-thirds of 

 the body is water. The teeth, the densest of the solids in the 

 human system, contain 'ten per cent, of water. The muscles, 

 tendons, and ligaments are more than half water; for it is 

 found that they lose more than half their weight when dried 

 with moderate heat. But it is in the fluids of the body that 

 water is found most abundantly. It gives to them the power 

 of holding a great variety of substances in solution, and is the 

 great highway by which new supplies are conveyed to the point 

 where they are required, and by which old particles of matter, 

 that have served their uses, are brought to the outlets of the 

 body to be thus removed from the system. (Bead Notes 3 and 4.) 



3. The Only Natural Drink. " Water is the natural drink of man, 

 as it is of all organized beings. It enters more largely into his compo- 

 sition than any other substance, giving liquidity to the blood, moisture to 

 all the tissues," and serving as the great solvent of the body ; not less 

 than two-thirds of its weight being of that element. It seems as if all 

 organic beings were so much "organized water." "Soft water is more 

 wholesome than hard, though water moderately hard is not perceptibly 

 injurious. When very hard, a part of the salts of lime can readily be 

 precipitated by boiling. As a rule, spring and well-waters, if brought 

 from deep fountains, are better and more wholesome than running 



4. What classification ? Define organic substances. Inorganic. Organic, how spoken 

 of? The inorganic ? Water and salt ? 



5. Water in physiology ? Where found ? Computation ? Water in the teeth f Mus- 

 cles, tendons, and ligaments ? How ascertained ? Water in the fluids of the body f What 

 is the advantage ? 



