218 NUTRITIONAL PHYSIOLOGY 



excrete. This may be contrary to the general impression, 

 for the temptation is to judge the work of a gland by the 

 volume of its output. But in the light of facts which 

 cannot be discussed here we are led to believe that con- 

 centration rather than sheer amount of secretion is what 

 puts the tubules of the kidneys to the severest test. They 

 act at the greatest disadvantage when required to excrete 

 a maximum of solids in a minimum of water. The urine 

 almost always has a concentration much higher than that 

 of the blood from which it is derived, and it is fair to assume 

 that the separation of the two fluids would be made easier 

 if the difference of concentration could be lessened. 

 Water drinking is the natural way to secure this result. 

 "Water," says Osier, "is, after all, the great diuretic." 



While teachers of hygiene are well agreed upon the value 

 of water in liberal quantities as conducing to health, 

 there has been much said against its free use with meals. 

 We can hardly question the impression that many cases of 

 indigestion have been benefited by the prohibition of water 

 at the table. An approach to Fletcherism is favored 

 when the saliva is not aided by swallows of water. Slower 

 eating is likely, and slower eating may be expected to 

 satisfy the appetite with a smaller actual intake. The 

 idea that the digestive juices are seriously diluted by water 

 taken with the food does not seem to be well founded. 

 Laboratory experiments show that dilution of the fresh 

 secretions is at least as likely to increase as to diminish 

 their activity. It must be borne in mind that the dilution 

 of a liquid containing a fixed amount of enzyme does not 

 reduce the quantity of the enzyme, but only makes it act 

 in a larger volume of the mixture. 



Very cold water swallowed rapidly may chill the mucous 

 membrane of the stomach and possibly retard the prog- 

 gress of gastric secretion. Digestion itself may also be 

 slowed if the contents of the stomach are cooled. But 

 bacterial fermentation should apparently be delayed just 

 as definitely as the normal hydrolysis, and we ought not 

 to make too much of these possibilities. Very recently 



