MUSCULAR MOVEMENT AND EXERCISE 375 



keeping blood away from the skin, which grows pale, 

 or even bluish, in prolonged cold. In a short time, 

 however, they relax; more blood comes to the skin, 

 making it glow and giving a fine sensation of warmth. 

 Cold baths exercise the muscles which surround the 

 arteries and keep them both in good condition, and 

 this prevents us from catching cold when suddenly 

 chilled (page 368). People who take a cold shower or 

 sponge bath every morning are little liable to colds, 

 and need only an occasional warm bath to keep 

 the skin clean and in perfect condition. Hot baths 

 relax these muscles, and so make the skin red; but 

 their effect is to make one more liable to catch cold; 

 they are therefore best taken before retiring. 



Kinds of exercise. No one can keep well long without 

 exercise. This should be taken regularly. The best 

 exercise is that which exercises the most muscles in 

 the open air and is not too violent. Since the leg 

 muscles are the largest in the body, walking and running 

 take first rank. But exercise of the waist muscles, 

 as in rowing, chopping or sawing wood, or digging in 

 the garden, has an especially good effect on the bowels 

 (page 359). 



Rest and repair. All exercise destroys muscle, and 

 to replace it two things are needed: rest and food. 

 Plenty of sleep, especially during the years of growth, 

 is just as necessary as exercise. Abundance of good 

 food, especially protein (page 348), is likewise needed. 



