RESPIRATION AND EXCRETION 339 



Relation of Proper Exercise to Health. — We are all aware that 

 exercise in moderation has a beneficial effect upon the human or- 

 ganism. The pale face, drooping shoulders, and narrow chest of 

 the boy or girl who takes no regular exercise is too well known. 

 Exercise, besides giving direct use of the muscles, increases the 

 work of the heart and lungs, causing deeper breathing and giving 

 the heart muscles increased work; it liberates heat and carbon 

 dioxide from the tissues where the work is taking place, thus in- 

 creasing the respiration of the tissues themselves, and aids me- 

 chanically in the removal of wastes from tissues. It is well known 

 that exercise, when taken some little time after eating, has a very 

 beneficial effect upon digestion. Exercise and especially games 

 are of immense importance to the nervous system as a means of 

 rest. The increasing number of playgrounds in this country is 

 due to this acknowledged need of exercise, especially for growing 

 children. 



Proper exercise should be moderate and varied. Walking in 

 itself is a valuable means of exercising certain muscles, so is bicy- 

 cling, but neither is ideal as the only form to be used. Vary your 

 exercise so as to bring different muscles into play, take exercise 

 that will allow free breathing out of doors if possible, and the 

 natural fatigue which follows will lead you to take the rest and sleep 

 that every normal body requires. 



Exercise should always be limited by fatigue, which brings with 

 it fatigue poisons. This is nature's signal when to rest. If one's 

 use of diet and air is proper, the fatigue point will be much further 

 off than otherwise. One should learn to relax when not in activity. 

 The habit produces rest, even between exertions very close to- 

 gether, and enables one to continue to repeat those exertions for 

 a much longer time than otherwise. The habit of lying down 

 when tired is a good one. 



The Relation of Tight Clothing to Correct Breathing. — It is 

 impossible to breathe correctly unless the clothing is worn loosely 

 over the chest and abdomen. Tight corsets and tight belts pre- 

 vent the walls of the chest and the abdomen from pushing outward 

 and interfere with the drawing of air into the lungs. They may 

 also result in permanent distortion of parts of the skeleton directly 



