It would be easy to fill a small volume with examples of the way in which we are walking directly into nervous prostration; examples only of this one variety of disobedience,--namely, of the laws of_ rest._ And to give illustrations of all the varieties of disobedience to Nature's laws in _activity_ would fill not one small book, but several large ones; and then, unless we improve, a year-book of new examples of nervous strain could be published. But fortunately, if we are nervous and short-sighted, we have a good share of brain and commonsense when it is once appealed to, and a few examples will open our eyes and set us thinking, to real and practical results. V. THE USE OF THE BRAIN LET us now consider instances where the brain alone is used, and the other parts of the body have nothing to do but keep quiet and let the brain do its work. Take thinking, for instance. Most of us think with the throat so contracted that it is surprising there is room enough to let the breath through, the tongue held firmly, and the jaw muscles set as if suffering from an acute attack of lockjaw. Each has his own favorite tension in the act of meditation, although we are most generous in the force given to the jaw and throat. The same superfluous tension may be observed in one engaged in silent reading; and the force of the strain increases in proportion to the interest or profundity of the matter read. It is certainly clear, without a knowledge of anatomy or physiology, that for pure, unadulterated thinking, only the brain is needed; and if vital force is given to other parts of the body to hold them in unnatural contraction; we not only expend it extravagantly, but we rob the brain of its own. When, for purely mental work, all the activity is given to the brain, and the body left free and passive, the concentration is better, conclusions are reached with more satisfaction, and the reaction, after the work is over, is healthy and refreshing. This whole machine can be understood perhaps more clearly by comparing it to a community of people. In any community,--Church, State, institution, or household,--just so far as each member minds his own business, does his own individual work for himself and for those about him, and does not officiously interfere with the business of others, the community is quiet, orderly, and successful. Imagine the state of a deliberative assembly during the delivery of a speech, if half-a-dozen of the listeners were to attempt to help the speaker by rising and talking at the same time; and yet this is the absurd action of the human body when a dozen or more parts, that are not needed, contract "in sympathy" with those that have the work to do. It is an unnecessary brace that means loss of power and useless fatigue. One would think that the human machine having only one mind, and the community many thousands, the former would be in a more orderly state than the latter.