“No physical endowment is of more importance for a long and a vigorous life than capacious lungs. The intensity and efficiency of an individual’s life depend very largely upon the amount of air he habitually passes in and out of his lungs, just as the intensity of a fire, granting plenty of fuel, depends upon the rate at which the air is brought in contact with the fuel. It has been found that lung capacity depends very largely upon the height; thus, the taller a person the greater his lung capacity, other things being equal. The following table shows the lung capacity, or rather the amount of air which can be forced out of the lungs, the so-called vital capacity, for men of different heights: Height Weight Vital Capacity Inches Pounds Cubic Inches 64 115 205 65 126 228 66 126 230 67 133 244 68 134 248 69 140 254 70 141 256 71 150 272 72 151 287 “The proper time for the development of the chest is in childhood and in youth. The best of all means for increasing the chest capacity is running and active sports of all sorts. Mountain climbing, going up and down stairs, and all kinds of exercises which produce strong breathing movements are effective means of chest development. Exercises of this nature are far superior to breathing exercises, so-called, of whatever sort. Breathing exercises in which the lungs are forcibly compelled to take in more than the ordinary amount of air very soon become tiresome. The effort is wholly voluntary, and the muscles soon weary. When, however, a thirst for air is created by some active exercise which fills the blood with carbonic-acid gas, so that deeper and more rapid breathing is necessary to rid the body of this poisonous gas and to take in a supply of oxygen in its place, the act of breathing is no longer difficult, embarrassing, or tiresome, but is, on the other hand, a pleasure and a gratification. The impulse which comes from within, from the so-called respiratory centers, so excites the respiratory muscles that they cause the chest to execute the strongest breathing movements with the greatest ease, ventilating every portion of the lungs, filling every air-cell to its utmost capacity. [Illustration: ONE OF THE TRAILS UP WHICH THE HOPIS CLIMB AT FULL SPEED.]