80 INORGANIC INGREDIENTS. 



From this table it will be seen that the greater part of potato and 

 of green vegetables is water, and that even of bread, water con- 

 stitutes a third. In other words, three of every four pounds of 

 potatoes and one of every three pounds of bread are water. In 

 some vegetables, such as the turnip, about 90 per cent, is water. 

 In liquid food, as milk, tea, and coffee, the proportion of water is, 

 of course, still greater. The amount of water daily taken into 

 the body in solid and liquid food aggregates 2000 c.c. In addition 

 to this there is a small amount actually formed within the body. 



One of the important ingredients of food is the class of carbo- 

 hydrates. A study of their composition shows that hydrogen and 

 oxygen exist in these substances in such proportion as to form 

 water. In the various changes which these elements undergo in 

 the body water is formed. Besides this source there is reason to 

 believe that a small quantity of water is formed by the action 

 of free oxygen on some organic substances. The amount of water 

 daily formed in these two ways is not far from 500 c.c., which 

 makes, with the water taken in with the food, a total of 2500 c.c. 



Avenues of Discharge from the Body. The water which has 

 been shown to form so essential a part of the body is not, how- 

 ever, a permanent ingredient that is, while water is always pres- 

 ent, it is not the same water : that which at one time exists in the 

 tissues is soon replaced by other water. The amount daily dis- 

 charged is equal to the amount taken in with the food and formed 

 in the body that is, about 2500 c.c. The avenues by which 

 it passes out, and the proportion by each, are as follows : 



Large intestine, as feces 4 per cent. 



Lungs, as watery vapor 20 " 



Skin, as perspiration 30 " 



Kidneys, as urine 46 " 



When discharged it is not pure water, but contains ingredients 

 that vary according to the channel by which it is eliminated. The 

 composition of these ingredients respectively will be studied in the 

 appropriate places. 



Salts. Sodium chlorid or common salt (NaCl) is present in 

 all the solids and fluids of the body, except in the enamel of the 

 teeth. The quantity (percentage) in different solids and fluids is 

 as follows : 



Milk 0.03 



Saliva 0.15 



Gastric juice 0.17 



Perspiration . . ! 0.22 



Blood . . 0^33 



Urine 0.55 



Bones 0.70 



The total quantity of common salt in the human body is 110 

 grams. 



Offices of Sodium Chlorid. The most important office which 



