Nature’s fine and wonderful mechanism needs to be constantly exercised in order to be in a condition to accomplish the object for which it was designed. The do-nothing system is a dangerous one in any case. Physical exercise in the direction of useful labor has a happy influence upon the mind, strengthens the muscles, improves the circulation, and gives the invalid the satisfaction of knowing how much he can endure, and that he is not wholly useless in this busy world; whereas, if this is restricted, his attention is turned to himself and he is in constant danger of exaggerating his difficulties. If invalids would engage in some well-directed physical exercise, using their strength but not abusing it, they would find it an effective agent in their recovery.