CHAPTER II. 

 THE CHEMISTRY OF THE BODY. 



THE body of an animal is composed of water, organic compounds, 

 and inorganic salts. If the body, or any part of it, be dried at a 

 temperature of 105 C., the loss of weight indicates the amount of water 

 present. If the dried solids be exposed to a high temperature in the 

 presence of oxygen, the organic compounds are all oxidised, and the 

 residue consists of the inorganic matter. 



THE INORGANIC SALTS. 



The chief salts which are found in the body are the chlorides, 

 phosphates, sulphates, and carbonates of sodium, potassium, calcium, 

 and magnesium. Iodine, fluorine, and a few other chemical elements 

 are also present in small amount ; iron enters into the composition of 

 the coloured corpuscles of the blood. Generally speaking, sodium is the 

 base most largely present in the body fluids, such as the plasma of the 

 blood, and potassium is that most abundant in the cells and tissues ; 

 while the bones owe their rigidity to the large proportion of calcium 

 phosphate and carbonate which they contain. 



The functions of the inorganic salts are various, and are not yet 

 completely understood. The waste carbonic acid from the tissues is 

 conveyed to the lungs partly in the form of carbonates and bicarbonates. 

 Sulphates and phosphates are to some extent waste products derived 

 from the breaking down of organic compounds. Phosphates also serve 

 a useful purpose in maintaining the balance between acids and bases in 

 the body by undergoing change from mono- to di-hydrogen phosphate, 

 or the reverse, as occasion requires. The salts as a whole, but especially 

 the chlorides, have, moreover, important functions depending upon their 

 physical properties (p. 14). 



THE ORGANIC COMPOUNDS. 



The organic constituents of the body fall naturally into two main 

 groups, non-nitrogenous and nitrogenous. The substances comprised 

 in these two groups may be looked upon as fragments of the protoplasm 



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