We often, however, fall into the bad habit of allowing our muscles to be inactive, and the result is they become weak and attenuated. Exercise is needed. Run the machinery and you obtain the wonderful result that the living machine improves in strength and size. The mere act of making the muscle work develops its powers. It grows stronger and thicker, and it works with greater precision and effectiveness. Hence the value of athletic exercises, if carefully carried out. They should not, however, fall on one muscle or one set of muscles exclusively. If they do, these muscles, instead of being benefited, suffer from fatigue. Athletic exercises should be carefully graduated and selected, so as to employ different groups of muscles, stimulating and developing each without unduly exhausting any one group. It is often forgotten, I think, that this is best accomplished by natural movements. The lower animals—for example, take a cat, in which the muscular arrangements are admirably developed—do not require to go to gymnasia for graduated athletic exercises. They run, and leap, and move in the almost unconscious enjoyment
