During sleeping hours the breathing movements are slighter and slower than when one is awake and active. It is necessary that the activity of the body should be lessened in order that rest may be secured; and yet the work of the liver, kidneys, and other organs which are engaged in throwing off poisons goes on continually; as does also the repairing work of the living cells, which are forever building up the parts of the body broken down by work or sickness. For some six to nine hours the body is thus occupied in resting and repairing itself, in order that on the next day it may respond like a living machine to the demand of the conscious mind. We should do all in our power to help on this recuperative process; and no way will be more effective than to sleep, out of doors, or with the head at a window, or at least in a well-ventilated room. There are a great number of breathing exercises described in various books on the subject, but the best breathing exercise is natural breathing. If the head is kept erect, and the shoulders low so that the chest is upright; if breathing is carried on through the nostrils, and the habit of deep breathing carefully cultivated—there will be no need for special exercises, save in the case of invalids. The most effective of all breathing exercises is to run or walk rapidly, or walk up a hill, or up stairs, if these be in the open air, with the head well back. This exercise heightens the action of the lungs, and all parts of the body are flooded with fresh air. HOW EXERCISE AIDS THE BATTLE OF THE BLOOD The question of breathing properly is intimately bound up with the question of exercise. The best of all exercise is play. All games in the open air which a person takes part in for the love of them far surpass the cleverest and most scientific sets of rules which physiologists have ever evolved. Unconscious performance of all the functions of the body is the ideal of hygiene. Exercise aids the battle of life within us in a direct manner. Exercise breaks down worn out tissue, making room for new and healthy tissue. It increases the rate of oxidation or burning up of fuel within us, and this in its turn enables the body to get rid of waste of material. Exercise also increases the strength and endurance of the muscles and fibres. When muscles become weak, they relax and allow various portions of the body to drop into positions which are not only ungraceful, but are decidedly injurious. When the muscles are not used and become flabby, the shoulders get rounded and drop forward through the weakness of the muscles which are intended to hold them back in position. The ribs which form the framework of the chest not being properly sustained by the muscles attached to them, gradually fall inward, thus flattening the chest, and compressing the lungs. There is a very close connection between gracefulness of carriage and sound bodily health.