Page:Popular Science Monthly Volume 67.djvu/415

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SLEEP as a factor in physical economics ranks in importance with respiration and digestion. Those who live normally, who throughout all ordinary exigencies maintain a natural attitude toward life, its strains and reponsibilities, may expect to enjoy a full measure of this restorative function. How much each one needs is not to be determined by dogmatic rules or precedents, nor does each one require the same amount under every condition or circumstance. There must be enough, daily and weekly, and of suitable character, to restore the balance of neural energy reduced by whatsoever of fatigue follows upon daily activities; otherwise the sensorium resents this deprivation in one way or another. Individual needs vary and can only be determined inferentially, giving due weight to generally accepted requirements.

Sleep, being the completest form of rest, is needed most by the youngest and least by the oldest. Most sleep is required by the weakest and least by the strongest. During childhood and exhaustive states too much sleep is rarely possible. For those in full tide of vigor too much sleep is often distinctly hurtful. Many modifications will immediately suggest themselves to those who are wise or learned in the science of bodily growth, development and disorders. Experience always counts for much. Variants, sometimes wide, are often permissible. Large errors will arise when these qualifications are marred by caprice, taste, prejudice; and harm follows, of one sort or another, sometimes of serious degree, by obscuration of sane reasoning on what may seem to be obvious and simple facts.

Physical efficiency depends chiefly upon the kind and amount of effort expended. Rest is an inevitable corollary. Relaxation is the starting point of all effort. For example, the strongest blows, the most accurate thrusts, can only proceed from an arm in thorough equipoise. Equipoise presupposes a full quantum of energy. Animal energy depends upon adequate rest as much as on force-giving foods. Complex acts, conditional always upon harmonies between intact central nervous dynamos, and well-adjusted mechanisms, can only be performed in their completeness when forces are at the norm.

Sleep is an absolute necessity for conscious beings. There are those who oppose this view, and some require relatively little, and that,