unless definitely diseased, is a perfectly adequate instrument, as abundantly able to cope with the complex demands of modern society as with the simpler but more strenuous life of the stone age.  The body has stored within its cells enough energy in the shape of protein, carbohydrate and fat to meet and more than meet any drains that are likely to be made upon it, either through the monotony of the daily grind or the excitement of sudden emergency.  Nature never runs on a narrow margin.  Her motto seems everywhere to be, “Provide for the emergency, enough and to spare, good measure, pressed down, running over.”  She does not start her engines out with insufficient steam to complete the journey.  On the contrary, she has in most instances reserve boilers which are almost never touched.  As a rule the trouble is not so much a lack of steam as the ignorance of the engineer who is unacquainted with his engine and afraid to “let her out.”

="The Energies of Men."= Perhaps nothing has done so much to reveal the hidden powers of mankind as that remarkable essay of Professor William James, “The Energies of Men."[48] Listen to his introductory paragraph as he opens up to us new “levels of energy” which are usually “untapped”: 

[Footnote 48:  James:  On Vital Reserves.]

Every one knows what it is to start a piece of work, either intellectual or muscular, feeling stale—­or cold, as an Adirondack guide once put it to me.  And everybody knows what it is to “warm up to his job.”  The process of warming up gets particularly striking in the phenomenon known as the “second wind.”  On usual occasions we make a practice of stopping an occupation as soon as we meet the first effective layer (so to call it) of fatigue.  We have then walked, played or worked “enough,” so we desist.  That amount of fatigue is an efficacious obstruction on this side of which our usual life is cast.  But if an unusual necessity forces us to press onward, a surprising thing occurs.  The fatigue gets worse up to a certain critical point, when gradually or suddenly it passes away, and we are fresher than before.  We have evidently tapped a level of new energy, masked until then by the fatigue-obstacle usually obeyed.  There may be layer after layer of this experience.  A third and fourth “wind” may supervene.  Mental activity shows the phenomenon as well as physical, and in exceptional cases we may find, beyond the very extremity of fatigue-distress, amounts of ease and power that we never dreamed ourselves to own, sources of strength habitually not taxed at all, because habitually we never push through the obstruction, never pass those early critical points.

Again Professor James says: