The force thus stored in the food and liberated within the system by the vital processes, finds scope for action in several different ways, prominent among which are, First, in the production of animal heat; Secondly, in muscular contractions and the motions of the limbs and members resulting from them; and Thirdly, in mental phenomena connected with the action of the brain and the nerves.  This last branch of the subject is yet enveloped in great mystery; but the proof seems to be decisive that the nervous system of man comprises organs which are actively exercised in the performance of mental operations, and that in this exercise they consume important portions of the vital force.  If, for example, a child is actually engaged at play, and we direct him to take a seat and sit still, he will find it very difficult to do so.  The inward force will soon begin to struggle within him to find an issue.  But if, while he is so sitting, we begin to relate to him some very surprising or exciting story, to occupy his mind, he will become motionless, and very likely remain so until the story is ended.  It is supposed that in such cases the force is drawn off, so to speak, through the cerebral organs which it is employed in keeping in play, as the instruments by which the emotions and ideas which the story awakens in the mind are evolved.  This part of the subject, as has already been remarked, is full of mystery; but the general fact that a portion of the force derived from the food is expended in actions of the brain and nervous system seems well established.

Indeed, the whole subject of the reception and the storing up of force from the sun by the processes of vegetable and animal life, and the subsequent liberation of it in the fulfillment of the various functions of the animal system, is full of difficulties and mysteries.  It is only a very simple view of the general principle which is presented in these articles.  In nature the operations are not simple at all.  They are involved in endless complications which are yet only to a very limited extent unravelled.  The general principle is, however, well established; and if understood, even as a general principle, by parents and teachers, it will greatly modify their action in dealing with the incessant restlessness and activity of the young.  It will teach them, among other things, the following practical rules: 

Practical Rules.

1.  Never find fault with children for their incapacity to keep still.  You may stop the supply of force, if you will, by refusing to give them food; but if you continue the supply, you must not complain of its manifesting itself in action.  After giving your boy his breakfast, to find fault with him for being incessantly in motion when his system has absorbed it, is simply to find fault with him for being healthy and happy.  To give children food and then to restrain the resulting activity, is conduct very analogous to that of the engineer who should lock the action