290 BIOLOGY AND HUMAN LIFE 



more of the heavy labor to machines, but we cannot shift to 

 any machines or medicines the job of keeping the organism in 

 working condition. 



230. Exercise. Many systems of exercise have been de- 

 veloped with the idea of getting what is necessary for the body 

 with the least effort and with the least loss of time. All these 

 systems somehow fail to keep people in good health; at least 

 they fail to keep people following the system long enough to 

 do any permanent good. The fact is that merely moving the 

 muscles is not sufficient. What is needed is a habit of giving the 

 muscles enough work every day to bring out the perspiration, 

 to quicken the breathing, to increase the heart beat. People 

 whose daily work is carried on with the large muscles have this 

 amount of exercise without setting aside any special time or any 

 special thought ; but most people who work at desks, or at auto- 

 matic machines, or at store counters, or at most of the jobs in 

 cities do not get sufficient exercise. They may get tired enough 

 every day, but that is not sufficient to keep the blood coursing 

 through the remotest capillaries, to make the air reach the very 

 last air sacs in the lungs, to clear the blood of all its wastes, to 

 keep the intestinal muscles in condition. 



For most people certain outdoor games offer the best and most 

 satisfying substitutes for a variety of interesting work and 

 adventure. For most of us traveling long distances by canoe 

 or on horseback, finding our own food and fuel and preparing 

 our meals and shelter, would be out of the question. Many 

 games, however, have in them very much the same kinds of 

 interests— adventure, rivalry, effort — as real work in the out- 

 of-doors, and they yield similar satisfaction of achievement in 

 addition to the varied exercise. There is real danger, however, 

 that we may overdo these games just because they are interest- 

 ing ; and because they make good spectacles for others there is 

 also the danger that many young people will cultivate stunts 

 and show pieces instead of playing the game for the fun of it. 

 Indeed, there is already so much professional playing of various 

 games that too many people spend what leisure time and spare 



