342 HAND-BOOK OF PHYSIOLOGY. 



the alimentary canal. The loss from these various organs may be thus 

 apportioned (quoted by Dalton from various observers). 



From the Alimentary Canal (faeces) . 4 per cent. 



Lungs 20 " 



Skin (perspiration) ... 30 



Kidneys (urine) 46 " 



100 



Sodium and Potassium Chlorides 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. In the blood, the quantity of chloride of sodium is greater than 

 that of all its other saline ingredients taken together. In the muscles, 

 on the other hand, the quantity of chloride of sodium is less than that of 

 the chloride of potassium. 



Calcium Fluoride, in minute amount, is present in the bones and 

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



Calcium, Potassium, Sodium, and Magnesium Phosphates 

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

 and teeth the phosphate of calcium exists in very large amount, and is 

 the principal source of that hardness of texture on which the proper per- 

 formance of their functions so much depends. The phosphate 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; 

 and, after the removal of its inorganic salts, a bone is left soft, tough, 

 and flexible. 



Potassium and sodium phosphates with the carbonates, maintain th& 

 alkalinity of the blood. 



Calcium Carbonate 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 

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

 matter existing as such in the body. 



Potassium and Sodium Carbonates are found in the blood, and 

 some other fluids and tissues. 



Potassium, Sodium, and Calcium Sulphates are met with in 

 small amount in most of the solids and fluids. 



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 haemoglobin, the coloring- 

 matter of the blood, of which a further account has been given with the 



