The Day Of Rest In Nature And Human Nature -- By: E. G. Martin
BSac 73:290 (April 1916) p. 318
The Day Of Rest In Nature And Human Nature1
That sustained effort of mind or body brings about a state of weariness with marked impairment of efficiency is among the commonest facts of human experience. That an adequate period of rest will abolish the weariness and restore the efficiency is knowledge that sustains the tired worker through his period of toil and enters gratefully into his experience at its completion.
These facts of common knowledge, which are, indeed, guiding principles of everyday life, become to the man of science more than just facts on which he may base his conduct; they are to him vital phenomena crying for interpretation. Confronted with the fact of human fatigue he wishes to know what are the bodily processes concerned in it; noting that rest causes weariness to disappear he seeks to learn what there is about rest to give it a power so beneficent.
No one would maintain that the nature of fatigue is wholly comprehended, yet in a general way we understand the processes concerned in it. We know that it results from activity of mind or body. We know, further, that in the production of activity the body operates as an engine, and is subject to
BSac 73:290 (April 1916) p. 319
the same laws as govern other engines. Of these the most fundamental is the law that the energy manifested cannot be created within the engine out of nothing, but must come from an antecedent source. The body, in respect to its energy source, is a chemical engine, deriving its power of activity from chemical transformations in material obtained directly or indirectly from the food. In these chemical transformations by which energy is afforded the material does not vanish, it merely enters new combinations. These latter are without value to the body; they are waste products to be gotten rid of as speedily as possible.
The body is so constructed that the energy-yielding transformations, and the consequent production of waste substances, occur directly within the regions of exertion. The muscles that are moved are the immediate seats of the chemical processes which furnish the energy for the movements; the brain cells whose activity constitutes a mental process carry on within themselves the chemical changes upon which their activity is based. In this location of the precedent chemical activity within the operating tissues we have the clue to the nature of fatigue, for the chemical transformations inevitably give rise, as we have seen, to waste products, and as these accumulate, by virtue of their mere presence, they hamper the operation of the tissues. The familiar analogy of the furnace c...
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