128 INFLUENCE OF WATER ON DIGESTION. 



Starch, which is the chief food - stuff in vegetables ; 

 while others, as gastric juice (p. 113), are adapted to 

 digest albumen, which is scarce in vegetables but abun- 

 dant in most animal foods. 



In warm weather, when the body easily keeps up its 

 animal heat, it is not well to eat much animal food. 



10. Drinking much Water during a Meal is Injurious. 

 The gastric juice acts well only in warmth, and a 

 glass of cold water cools the stomach very much, 

 and for a considerable time. Cold, also, drives the 

 blood out of the mucous membrane, just as it would 

 out of the skin. This stops or diminishes the action 

 of the glands, which can only pour out abundant gastric 

 juice when they are richly supplied with blood. If 

 water be taken slowly, and only a few mouthfuls at a 

 time, a much smaller quantity will satisfy the thirst, 

 than if a glassful be taken at a draught. Also, the 

 stomach is not enough cooled, at any moment, to inter- 

 fere with digestion. Moreover there is a limit to the 

 amount of water which the coats of the stomach will 

 quickly absorb. Any more than that will be left over 

 and make the gastric juice too weak to work well. 



About a single glass with a meal in cool weather, and 

 two glasses in warm, is a proper quantity. 



In warm weather or after heating exercise it is well to 

 assuage thirst at least half an hour before going to table, 

 so that the water may be absorbed before the stomach 

 is called upon to digest. 



10. What is necessary in order that the gastric juice may act 

 well ? What is the effect of drinking a glass of ice-water? How does 

 cold act on the blood in the mucous membrane ? What is the con- 

 sequence as regards the glands of the stomach ? Why should water 

 be drunk slowly ? The proper quantity with a meal ? Why assuage 

 thirst some time before eating? 



