94 THE CHEMICAL COMPOSITION OF THE BODY 



way, as chloride of sodium, of which only four-fifths of the quantity ingested 

 are excreted in the same form. Some are newly formed within the body- 

 as, for example, a part of the sulphates and carbonates. 



Much of the inorganic saline matter found in the body is a necessary 

 constituent of its structure, as necessary in its way as albumin or any other 

 organic principle. Another part is important in regulating or modifying 

 various physical processes, as absorption, solution, and the like. A part 

 must be reckoned only as matter which is, so to speak, accidentally present, 

 whether derived from the food or the tissues, and which will, at the first 

 opportunity, be excreted from the body. The principal salts present in 

 the body are: 



Sodium and Potassium Chlorides. These salts are present in nearly 

 all parts of the body. The former seems to be especially necessary, judging 

 from the instinctive craving for it on the part of animals in whose food it is 

 deficient, and from the diseased condition which is consequent on its with- 

 drawal. The quantity of sodium chloride in the blood is greater than that 

 of all its other saline ingredients taken together, but it is present chiefly in 

 the fluids of the body. In the tissues, the muscles for example, the quantity 

 of sodium chloride is less than that of the chloride of potassium, which 

 forms a constant ingredient of protoplasm. 



Calcium Fluoride. It is present in minute amount in the bones and 

 teeth, and traces have been found in the blood and some other fluids. 



Calcium, Potassium, Sodium, and Magnesium Phosphates. These phos- 

 phates are found in nearly every tissue and fluid. In- some tissues the bones 

 and teeth the phosphate of calcium exists in very large amount. The phos- 

 phate of calcium is intimately incorporated with the organic basis or matrix, 

 but it can be removed by acids without destroying the general shape of the 

 bone. After the removal of its inorganic salts, a bone is left soft, tough, 

 and flexible. 



Potassium and sodium phosphates, with the carbonates, maintain the 

 alkalinity of the blood. 



Calcium Carbonate. It occurs in bones and teeth, but in much smaller 

 quantity than the phosphate. It is found also in some other parts. The 

 small concretions of the internal ear (otoliths) are composed of crystalline 

 calcium carbonate, and form the only example of inorganic crystalline matter 

 existing as such in the body. 



Potassium and Sodium Carbonates and Sulphates. These are found in 

 the blood and most of the secretions and tissues. 



Silicon. A very minute quantity of silica exists in the urine and in the 

 blood. Traces of it have been found also in bones, hair, and some other parts. 



Iron. The especial place of iron is in hemoglobin, the coloring-matter 

 of the blood, of which a full account will be given with the chemistry of the 

 blood. Iron is found, in very small quantities, in the ashes of bones, mus- 



