BIOLOGY APPLIED TO HEALTHFUL LIVING 529 



for busy people, whose muscles or nerves are hard-worked. 

 Then, after the day's work and a brief rest is the best time for 

 dinner, the chief meal of the day. The reason for this is that 

 intellectual activity leads to a marked increase in the amount 

 of blood in the vessels of the brain, and physical work affects 

 muscles similarly. The result must be a withdrawal of 

 blood from the vessels of the digestive organs and a conse- 

 quent retardation of the digestive process. 



The above plan suits most people ; A .4)ut there are numerous 

 individual exceptions, and each one must experiment with 

 himself if he would find the most v satisfactory time for meals. 

 Work and habits of human beings vary so greatly that there 

 can be no universal law of eating. Certain rules for general 

 application have been established by the experience of thou- 

 sands of people, and probably most important for remember- 

 ing are the following: (1) There should be regularity in 

 meals. (2) Physical and mental fatigue interfere with di- 

 gestion. (3) Overeating acts likewise. 



The selection of diet and its amount is similarly variable. 

 Hard physical exertion and exposure to cold demand abun- 

 dant food for energy ( 420, 421), and the question of easy 

 digestibility is of minor importance. On the other hand, per- 

 sons of sedentary habits should avoid unnecessary amounts of 

 all kinds of foods ; and also observe well their own pecul- 

 iarities as to digestibility of carbohydrates and fats. 



Eating anything between meals is, as a rule, inadvisable; 

 but here again there are individual exceptions, and knowledge 

 of the possible harm to digestion will lead to caution. 



Some water (not iced) should be taken at every meal, for 

 it is needed in liquefying the contents of the stomach in prep- 

 aration for escape into the intestine ( 400). But water 

 should not be taken at the same moment with solid food, for 

 it " washes down " the food and thus prevents mastication. 

 The old idea that water dilutes the gastric juice does not 

 now seem to be very significant, for it has been discovered 

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