I9I4] P. B. Hawk 423 



here again we are confronted by chemical and physical processes 

 which are dependent upon the presence of water. In the first place 

 the surface of the lungs must be moist before there can be any ex- 

 change of carbon dioxid and oxygen by diffusion; and secondly, 

 the blood cells are transported in a fluid medium. The regulation 

 of the temperature of the body is facihtated by the presence of cir- 

 culating water and the evaporation of water from the surface of 

 the skin. Water serves as a medium by which nutritive material is 

 carried to the body cells. All mucous surfaces of the human body 

 require the presence of water before they can function normally; a 

 dry mucous membrane is unable to play the röle for which it was 

 designed. Water also has an important relationship to absorption. 

 If the end-products of digestion in the intestine are not present in 

 proper dilution they will not be most efficiently absorbed. It has 

 been shown by experiment that dilute Solutions of sugar (glucose), 

 for example, are absorbed much more satisfactorily from the intes- 

 tine than are concentrated Solutions. If the sugar is present in 

 higher concentration than 8 per cent. a diluting secretion emerges 

 from the walls of the intestine to bring about proper dilution. 

 Moreover, the elimination of toxic substances from the body is ac- 

 complished more satisfactorily if they are brought to the kidney 

 well diluted. 



In addition to the above classes of activities, which are made pos- 

 sible or facilitated by the presence of water, there are many other 

 chemical processes in the human body which not only require water 

 for their proper conduct, but which are accompanied by the loss or 

 gain of water to the chemical structures undergoing change. I 

 refer to the changes which are accompanied by hydrolysis and de- 

 hydrolysis or anhydrolysis. A reaction of this character occurs 

 when our physician prescribes ammonium benzoate. In the body 

 this ammonium benzoate is split into benzoic acid and ammonia. 

 The kidney then takes the benzoic acid and conjugates it with gly- 

 cocoll, the synthesis being accompanied by the liheration of water 

 and the formation of hippuric acid, which is excreted in the urine. 

 In poisoning by methyl alcohol, the alcohol is oxidized in the body to 

 formic acid and water. When Phenolphthalein is used as a cathartic 

 it comes in contact wth the sodium carbonate in the intestine, water 



