Besides the nervous folk who feel themselves so weary that they scarcely have strength to live, there are thousands upon thousands of men and women who are called normal but who have lost much of the joy of life because they feel their bodies inadequate to meet the demands of everyday living. To such men and women the Biblical promise, "As thy day, so shall thy strength be," comes now as the message of modern science. Nature is not stingy. She has not given the human race a meager inheritance. She did not blunder when she made the human body, nor did she allow the spirit of man to develop a civilization to whose demand his body is not equal. After its long process of development through the survival of the fittest, the human body, 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_.]