Page:Popular Science Monthly Volume 20.djvu/114

 104 but working at low-pressure is incomparably worse. As a matter of experience, a sense of weariness commonly precedes collapse from "overwork"; not mere bodily or nervous fatigue, but a more or less conscious distaste for the business in band, or perhaps for some other subject of thought or anxiety which obtrudes itself. It is the offensive or irritating burden that breaks the back. Thoroughly agreeable employment, however engrossing, stimulates the recuperative faculty while it taxes the strength, and the supply of nerve-force seldom falls short of the demand. When a feeling of disgust or weariness is not experienced, this may be because the compelling sense of duty has crushed self out of thought. Nevertheless, if the will is not pleasurably excited, if it rules like a martinet without affection or interest, there is no verve, and, like a complex piece of machinery working with friction and heated bearings, the mind wears itself away and a breakdown ensues. Let us look a little closely at this matter.

The part which "a stock of energy" plays in brain-work can scarcely be exaggerated. Reserves are of high moment everywhere in the animal economy, and the reserve of mental force is in a practical sense more important than any other. It may happen that mere strength of mind carries a body with scarcely a vestige of power in reserve through some crisis of extraordinary difficulty, but the mental exploit is full of danger. The residual air in a lung is the basis of the respiratory process; the sustained tension of the smaller arteries transforms the pulsating current of blood thrown into the system by the heart to a continuous circulation; the equilibriated tonicity of opposing muscles gives stability to the apparatus of motion, and renders specific combinations of movement possible. What is true of the physical is also true of the mental constitution; the residual force, the tension, the tonicity, of mind, form the basis of intellectual action. It is not necessary to discuss the relations of mind and matter; even if the mental being is no more than a formulated expression of the physical organism, the continuity is so complete that the same laws govern both. For the purposes of the present argument it is sufficient to assert that, without a reserve of energy, healthy brain-work is impossible. Pain, hunger, anxiety, and a sense of mind-weariness, are the warning tokens of exhaustion extending to the reserves. When these indications are disregarded, or destroyed, as they may be, by stupefying drugs, an inordinate use of stimulants, a strong effort of the will, or the anæsthetic effect of excessive exhaustion, the consumption of energy goes on unobserved. The feats of intellectual or physical strength, the surprising exploits of special sensation and mind-power, performed by individuals under the influence of any condition which suspends the sense of pain, weakness, or fatigue, are explained by the circumstance that unsuspected reserves of power and endurance are placed at the disposal of the will. These resources were there before, but jealously guarded by the sensations. Martyrdom is possible under the influence of an over-