=Long-Lived Insomniacs.= A man of my acquaintance once said in all seriousness and with evident alarm: "I am following in the footsteps of my mother. She lived to be seventy years old and she had insomnia all her life." If this man had been preaching a sermon on the harmlessness of chronic insomnia, he could not have chosen a better text, but he seemed just as much concerned about himself as if his mother had died from the effects of three months' wakefulness. People can live healthy lives during twenty or thirty years of insomnia because chronic insomnia is nothing more or less than a habit, and "habit spells ease." The brain cells are not irritated by either internal or external stimuli; there is no effort to keep awake; virtually no energy is expended,--except in restless tossing and worry. If the body is kept still and emotion eliminated, fatigue products are washed away and the reserves are filled in with perfect ease. =Thinking in Circles.= Habit means automatic, subconscious activity, with the least expenditure of energy and the least amount of fatigue. We have already noted the ease with which heart and diaphragm muscles carry on their work from the beginning of life to its end. Anything relegated to the subconscious mind can be kept up almost indefinitely without tire, and to this subconscious type of activity belong the thoughts of a chronic insomniac. Despite all assertions to the contrary, his conscious mind is not really awake. If he is questioned about the happenings of the night, he is likely to have been unaware of the most audible noises. The thoughts that run through his brain are not new, constructive, energy-consuming thoughts, but the same old thoughts that have been going around in circles for days and weeks at a time. It is true that a person sometimes chooses to wake up and do his constructive planning in the night. This kind of thought does bring fatigue, up to a certain point. After that the body hastens its rate of repair or automatically goes to sleep. Activity of this kind is always a matter of choice. He who really prefers sleep will shut the drawers containing the day's business and leave them shut until morning. =Day-Dreaming at Night.= However, the man who makes a practice of staying awake rarely does much real thinking. He lets the thoughts run through his mind as they will, builds air-castles of things he would like to do and can't, or other kinds of air-castles about the disastrous effects of his insomnia on the day that is to come; he worries over his health, or his finances, and grieves over his sorrows. He is really indulging himself, thinking the thoughts he likes most to think, and these consume but little energy. Like a horse that knows the rounds, they can go jogging on indefinitely without guidance from the driver. WHAT CAUSES THE FATIGUE