Water as a Dietary Constituent 



PHILIP B. HAWK 



PHILADELPHIA 



Introduction 



The average man who lives among water mains, hydrants, and street, 

 sprinklers and in the vicinity of rivers and lakes gives little or no thought 

 to the important part water plays in his life processes, if indeed he 

 possesses any definite knowledge on the subject. If such a man were 

 possessed of an introspective hydro-eye, he could quickly convince him- 

 self that "water" and "life" are synonymous terms so far as the human 

 body is concerned. If he would flash the rays of this eye upon himself, 

 he would find that the blood plasma, that important carrier of nutritive 

 material to every organ and tissue, contains over 90 per cent of water; 

 that the brain, which regulates and correlates so many intricate activities 

 and processes, contains from 85 to 90 per cent water ; that the liver cell, 

 which is associated with so many processes which are vital to the main- 

 tenance of normal metabolism, contains 75 per cent water; that the 

 mighty muscle, which is so importantly related to feats of strength, is 

 three-fourths water; that the saliva, which quickly reduces the complex 

 and insoluble starch of our foods to a simple soluble sugar, is almost 

 pure water (99.5 per cent) ; that bone, which has been shown by test to 

 possess a tensile strength (25,000 pounds per square inch) one and one- 

 fourth times as great as that of cast iron and more than twice that of 

 good timber, is 40 per cent water; and finally, if he would put his 

 150-pound body in an electric oven and drive off all the water, the under- 

 taker would have to handle only 50 pounds, because the human body as a 

 whole is about two-thirds water. 



Since water is found in such large quantities in all organs, tissues, 

 and secretions of the body, it is not surprising that water is absolutely 

 essential to the proper performance of so many bodily functions. For 

 example, in respiration we have chemical and physical processes which 

 are dependent upon the presence of water. The surface of the lungs must 

 be moist before there can be any exchange of carbon dioxid and 

 oxygen. The regulation of body temperature is facilitated by the presence 

 of circulating water and the evaporation of water from the surface of the 



275 



