WATER 11 



Necessity for water 



The demands of tlic body for water arc far more imperative than 

 those for food. An animal can live for 100 days or more without food 

 but dies within five to ten days if no water is supplied. With a Scotch 

 collie, Hawk conducted two experiments in which the dog was main- 

 tained for 105 and 117 days, respectively, without food, but with an 

 abundance of water. At the end of each period the animal was still in 

 a fair condition of health. 



In the life of the plant enormous quantities of water arc transpired. 

 From three hundred to four hundred pounds of water are involved in 

 the manufacture of one pt)und of dry matter. ^A'ater is one of the great 

 raw materials from which the plant produces sugars, fats, proteins, and 

 all the other substances which go to make up the plant cell. 



Function of water 



Since all chemical changes involved in digestion are of a hydrolytic 

 nature, water is concerned in the first step toward utilization of fats, 

 proteins, and the higher carbohydrates. Water functions as a medium 

 for the transportation of food materials during digestion, absorption, and 

 circulation; and of waste prcxlucts, as well, in the process of elimination. 

 Hawk has demonstrated that digestion by saliva is more rapid if the 

 saliva is diluted with about seven times its volume of water. Gastric 

 digestion and pancreatic digestion also are aided by liberal quantities of 

 water. Carbohydrates, fats, and proteins are more completely absorbed 

 when large quantities of water are ingested with the food. The growth 

 of bacteria, and consequent putrefactive processes, are decreased by the 

 use of liberal quantities of water with food. 



AVater also plays an important role as a heat regulator. Because of 

 the high specific heat of water, oxidation in the body can proceed without 

 greatly increasing the temperature at the site of oxidation. Water is 

 a good conductor of heat and thus aids in the transfer of heat from the 

 interior to the surface of the body. Finally, because of its high latent 

 heat of vaporization, water carries off heat by vaporization in the expired 

 breath and evaporation from the surface of the body. It is estimated 

 that about 25 per cent of the heat produced in the body is carried off 

 by way of the breath and by evaporation from the skin. In animals that 

 do not perspire freely — dogs, swine, cattle — excess heat is dissipated by 

 increasing the respiration (panting). 



Finally, water performs an important function as a lubricant in the 

 many movements of the muscles, joints and organs of the body. 



