428 BIOLOGY FOR BEGINNERS 



2. Useful exercise should use the body muscles as well as arms and 

 legs: walking, swimming, and throwing are good examples. 



3. Exercise should cause full, deep breathing and preferably 

 should be in the open air. Loose clothing and erect position neces- 

 sarily follow. 



4. Exercise should be varied and should occupy the mind as 

 well as the body; any movements, however excellent, lose much 

 if they are not enjoyed while being performed. This is the objec- 

 tion to many really beneficial " systems of exercise " which become 

 very distasteful because of lack of interest. 



Hygiene of Digestion. For the general study of foods refer to 

 Chapter 37. The following is a summary of facts explained there: 



1. The amount and kind of food should be adjusted to the work 

 of the body. 



2. The " balance " of the ration should be maintained. 



3. The food should be clean and properly prepared. 



4. Usually the heartiest meal should come after the day's work 

 and should be preceded by a brief rest. Only when the brain or 

 muscles are not working, can the digestive organs get proper supply 

 of blood. 



5. Eating between meals is usually a bad practice, especially 

 in case of sweet foods, as it prevents proper desire for, and diges- 

 tion of, the solid food which the body requires. 



6. Water in abundance should be used both between and at 

 meals, but not to " wash down " unchewed food. It does not 

 " dilute the gastric fluid" but passes quickly from the stomach 

 and digestion is aided rather than hindered. 



7. It is unnecessary to dwell upon the importance of thorough 

 chewing. The smaller the food particles, the greater the surface 

 exposed for digestion and the less burden is put upon the stomach. 

 The starch digestion in the mouth may not be very extensive, but 

 thorough mastication prevents over-eating and too rapid eating, 

 both of which produce more indigestion than all other causes put 

 together. " Leave the table hungry " is a good rule. Americans 

 eat too much, particularly of proteid foods, a habit which is both 

 unhealthful and expensive. 



