Proper habits of sitting, standing, and walking, if not attained during youth, are rarely acquired afterward. The habit of a graceful carriage and a manly or womanly bearing should be established before the age of sixteen. But the exercises that most closely affect the health are those which relate to the expansion of the chest. The lungs vitalize and purify the blood. The larger their capacity, the more satisfactorily will they accomplish their work. With a good supply of pure blood, the growth and health and vigor of the body will be largely provided for. =Middle Life.=--While judgment and discretion in the kinds of exercises, and in the manner of doing them, are, at every period of life, desirable, persons from 20 to 35 years of age are able to undertake severer tasks and to withstand greater shocks to the system than the young or the old. Persons from 35 to 50 years of age may take long walks but should be cautious about rapid running. At this age exercises requiring endurance and persistence are better than those demanding intensity or violence. This is especially applicable to those whose occupation is sedentary. Any hereditary tendency to disease is apt to show itself during this period, and should be carefully watched by the individual and by his physician, for by it the kind and degree of the exercise should be determined. =Old Age.=--Unless the habit of taking physical exercise has been pursued more or less constantly through life, persons in advanced years, especially if feeble, need to observe great caution in beginning it, on account of the unusual strain upon the heart and blood-vessels. Their native power of resistance being small, any severe shock or strain upon the system may be attended with serious results. William Cullen Bryant, at eighty years of age, took an hour of severe exercise, followed by a cold bath, before breakfast, then walked three miles to his office and back again, in all states of weather, but he had kept up his physical training through life, and found in it a pleasure as well as a benefit to health. With increasing years, the duties and responsibilities of the busy man increase. Instead of the walk or the ride on horseback, the stately coach, which more fittingly represents his growing wealth, is now used for his afternoon recreation, the coachman relieving him of even the mental and physical stimulus of driving. Wealth is a menace to health, so far as it tends to discourage the simple living upon which health depends.