It has been stated, that the excessive use of the muscles, as much as their inactivity, tends to weaken them. Nothing is more painful, than the keeping a muscle constantly on the stretch, without any relaxation or change. This can be realized, by holding out an arm, perpendicularly to the body, for ten or fifteen minutes, if any one can so long bear the pain. Of course, confinement to one position, for a great length of time, tends to weaken the muscles thus strained. This shows the evil of confining young children to their seats, in the schoolroom, so much and so long as is often done. Having no backs to their seats, as is generally the case, the muscles, which are employed in holding up the body, are kept in a state of constant tension, till they grow feeble from overworking. Then, the child begins to grow crooked, and the parents, to remedy the evil, sometimes put on bracers or corsets. These, instead of doing any good, serve to prevent the use of those muscles, which, if properly exercised, would hold the body straight; and thus they grow still weaker, from entire inactivity. If a parent perceives that a child is growing crooked, the proper remedy is, to withdraw it from all pursuits which tax one particular set of muscles, and turn it out to exercise in sports, or in gardening, in the fresh air, when all the muscles will be used, and the whole system strengthened. Or, if this cannot be done, sweeping, dusting, running of errands, and many household employments, which involve lifting, stooping, bending, and walking, are quite as good, and, on some accounts, better, provided the house is properly supplied with fresh air. Where persons have formed habits of inactivity, some caution is necessary, in attempting a change; this must be made gradually; and the muscles must never be excessively fatigued at any time. If this change be not thus gradually made, the weakness, at first caused by inactivity, will be increased by excessive exertion. A distinguished medical gentleman gives this rule, to direct us in regard to the amount of fatigue, which is safe and useful. A person is never too much fatigued, if one night of repose gives sufficient rest, and restores the usual strength. But, if the sleep is disturbed, and the person wakes with a feeling of weariness and languor, it is a sure indication that the exercise has been excessive. No more fatigue, then, should be allowed, than one night's rest will remedy.