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 visible, as the trembling of the muscle. Figure 47 shows an easy standing posture.

What causes Fatigue.—Fatigue or exhaustion is due to the using up of the living material in the nerve cells and muscle cells by oxidation. Rest is necessary to give cells opportunity to repair themselves. Why is it less fatiguing to walk for an hour than to stand perfectly still for ten minutes? ; causes spine to curve to side; raises one hip and shoulder above the other. ; chest is free to expand, and weight is easily shifted from one foot to other. Degeneration of Muscles begins with habitual disuse. We dare not furnish a substitute for the work of a muscle, if we wish the muscle to remain sound. A belt or a stay at the waist will cause the muscles of the trunk to become flabby and the abdomen to relax and protrude. How Muscular Activity helps the Health.—Life is change, stagnation is death. Muscular activity uses up the