This is one of the secrets of the healthfulness and value of play and games for children, and for older persons as well. When you get tired, you can stop and rest; and then start in again when you feel rested--that is to say, when your heart has washed the poisons out of your muscles and nerves. In fact, if you will notice, you will find that nearly all play and games are arranged on this plan--a period of activity followed by a period of rest. Some games have regular "innings," with alternate activity and rest for the players; or each player takes his turn at doing the hard work; or the players are constantly changing from one thing to another--for instance, throwing or striking the ball one minute; running to first base the next; and standing on base the next. Every muscle, every sense, every part of you is exercised at once, or in rapid succession, and no part has time to become seriously fatigued; so that you can play hard all the afternoon and never once be uncomfortably tired, though your muscles have done a tremendous lot of work, measured in foot-pounds or "boy-power," in that time. The good school imitates nature in this respect. The recitation periods are short, and recesses frequent; a heavy subject is followed by a lighter one; songs, drawing, calisthenics, and marching are mixed in with the lessons, so as to give every part of the mind and body plenty to do, and yet not over-tire any part. All-Round Training from Work and Play. Every game that is worth playing, every kind of work that accomplishes anything worth while, trains and develops not merely the muscles and the heart, but the sight, hearing, touch, and sense of balance, and the powers of judgment, memory, and reason, as well. If you are healthy, you know that you don't need to be told to play, or even how, or what, to play; for you would rather play than eat. You have as strong and natural an appetite for play as you have for food when you are hungry, or for water when you are thirsty, or for sleep when you are tired. It is just as right to follow the one instinct as the others, though any one may be carried to extremes. Some of the most important part of your training and fitting for life is given by plays and games. Not only do they put you in better condition to study and enjoy your work in school, but they also teach you many valuable lessons as well. Our favorite national game, base-ball, for instance, not only develops the muscles of your arms and shoulders in throwing the ball and in striking and catching it, and your lungs and heart in rushing to catch a fly or in running the bases, but also develops quickness of sight and hearing,--requires, as we say, "a good eye" for distance,--makes you learn to calculate something of the speed at which a ball is coming toward you or flying up into the air, requires you to judge correctly how far it is to the next base and how few seconds it will take to get there and whether you or the baseman can get there first.