Now it is certain that nothing contributes so little to cheerfulness as riches, or so much, as health. Is it not in the lower classes, the so-called working classes, more especially those of them who live in the country, that we see cheerful and contented faces? and is it not amongst the rich, the upper classes, that we find faces full of ill-humor and vexation? Consequently we should try as much as possible to maintain a high degree of health; for cheerfulness is the very flower of it. I need hardly say what one must do to be healthy--avoid every kind of excess, all violent and unpleasant emotion, all mental overstrain, take daily exercise in the open air, cold baths and such like hygienic measures. For without a proper amount of daily exercise no one can remain healthy; all the processes of life demand exercise for the due performance of their functions, exercise not only of the parts more immediately concerned, but also of the whole body. For, as Aristotle rightly says, _Life is movement_; it is its very essence. Ceaseless and rapid motion goes on in every part of the organism. The heart, with its complicated double systole and diastole, beats strongly and untiringly; with twenty-eight beats it has to drive the whole of the blood through arteries, veins and capillaries; the lungs pump like a steam-engine, without intermission; the intestines are always in peristaltic action; the glands are all constantly absorbing and secreting; even the brain has a double motion of its own, with every beat of the pulse and every breath we draw. When people can get no exercise at all, as is the case with the countless numbers who are condemned to a sedentary life, there is a glaring and fatal disproportion between outward inactivity and inner tumult. For this ceaseless internal motion requires some external counterpart, and the want of it produces effects like those of emotion which we are obliged to suppress. Even trees must be shaken by the wind, if they are to thrive. The rule which finds its application here may be most briefly expressed in Latin: _omnis motus, quo celerior, eo magis motus_.