minerals 25 



Chemical Compounds of the Body. 



The elements previously enumerated very rarely occur 

 in an uncombined state in plant or animal matter; the 

 only important exception to this rule being the element 

 oxygen, and even that is more abundant in combined 

 form than in the free state. The various compounds 

 (acids, oxides, salts, and bases) are so numerous and 

 varied that it would take too long to enumerate them all. 

 Fortunately, they admit of classification into a few char- 

 acteristic groups of life properties. These groups are 

 called, respectively, minerals, gases, and carbon com- 

 pounds. 



Minerals. — Under this head are grouped water, mineral 

 salts, and all acids that do not contain carbon. The only 

 important acid in our bodies under this group is hydro- 

 chloric, and this is found in small quantities in the gastric 

 juice of the stomach. Water forms more than fifty per 

 cent, by weight, of all living matter. In the human body 

 approximately .59% is water; the bones contain 22%, the 

 liver 69%, the muscles 7.5%, and the kidneys 82%, while 

 the fluids of the body are still richer in water content. 

 Mineral salts will not burn, and by burning different parts 

 of the body until nothing but the ash or mineral salts 

 remain we cannot only demonstrate their presence in 

 every part of the body, but also determine the form and 

 proportion present. Such determination shows them to 

 be of great variety as to kind. The most common are 

 the chlorides, carbonates, and phosphates of the metals 

 sodium, calcium, and potassium. These names indicate 

 the predominant elements in these compounds. Bone ash 

 also represents nearly 33% by weight of the entire bone^ 



