20 THE HUMAN BODY. 



istry to our aid, to discover what elements and compounds 

 make up the cells and intercellular substance. 



Elements found in the body. Of the elements, about 

 seventy in number, known to chemistry, only sixteen exist 

 in the body.* Very few of these exist in it uncombined. 

 Some oxygen is dissolved in the blood ; and it is also 

 found mixed with nitrogen in the lungs. 



Chemical compounds existing in the body. These are 

 so numerous that ib would be a long task to enumerate 

 them, but some few require mention : they may be divided 

 into organic and inorganic. In a general way we may say 

 that the organic constituents of the body, if all water were 

 separated from them, would burn if put in a fire ; and the 

 inorganic components could not be made to burn. 



Inorganic constituents of the body. Of the inorganic 

 constituents of the body, water and common salt are the 

 most important ; they are found in all the organs and 

 liquids of the body. Phosphate and carbonate of lime are 

 found in large proportions in the bones and teeth ; and 

 free hydrochloric acid (spirits of salts or muriatic acid) 

 exists in the gastric juice, which dissolves some kinds of 

 food in the stomach. 



Organic constituents of the body. The organic con- 

 stituents of the body all contain carbon, hydrogen, and 



How many chemical elements exist in the body ? Are most of 

 them free or combined with others ? Name those found free. 



Into what main groups may be divided the chemical compounds 

 existing in the body ? Name some of the chief inorganic compounds 

 helping to build the body. Where are they found in it? 



What do all organic substances in the body contain? 



* The elements found in the body in health are carbon, hydrogen, nitrogen, 

 oxygen, sulphur, phosphorus, chlorine, fluorine, silicon, sodium, potassium, lithium, 

 elciiim, magnesium', iron, and manganese. 



