The curious thing with regard to animal energy, however, is that it does not accumulate in the body beyond a certain limited extent, and all energy that is manufactured beyond that seems to have a definite tendency to dissipate itself throughout the body, producing discomfort of various kinds instead of doing useful work. The process is very like what is called short-circuiting in electrical machinery, and this enables us to understand how much harm may be done. Making ourselves comfortable, therefore, may in the {15} end have just exactly the opposite effect, and often does. This is not noted at first, and may escape notice entirely unless there is an analysis of the mode of life which is directed particularly to finding out the amount of exertion of will and energy that there is in the daily round of existence. The will, like so many other faculties of the human organism, grows in power not by resting but by use and exercise. There have been very few calls for serious exercise of the will left in modern life and so it is no wonder that it has dwindled in power. As a consequence, a good deal of the significance of the will in life has been lost sight of. This is unfortunate, for the will can enable us to tap sources of energy that might otherwise remain concealed from us. Professor William James particularly called attention to the fact, in his well-known essay on "The Energies of Men", that very few people live up to their _maximum_ of accomplishment or their _optimum_ of conduct, and that indeed "_as a rule men habitually use only a small part of the powers which they actually possess and which they might use under appropriate conditions._" It is with the idea of pointing out how much the will can accomplish in changing things for {16} the better that this volume is written. Professor James quoted with approval Prince Pueckler-Muskau's expression, "I find something very satisfactory in the thought that man has the power of framing such props and weapons out of the most trivial materials, indeed out of nothing, merely by the force of his will, which thereby truly deserves the name of omnipotent." [Footnote 1] [Footnote 1: "Tour in England, Ireland and France."]