Deep breathing aids digestion and assimilation, not only because of the regular exercise given to the pancreas, the spleen, the stomach, and the liver by the correct movement of the diaphragm, but also because of the latent heat which the oxygen liberates within the digestive organs and out among the tissues. While the chemical action of food creates activity within, this activity is materially aided by exercise. Exercise and oxygen are also necessary for chemical action in tearing down waste and in putting raw material into condition to be appropriated to the body needs. _Two glasses of water in the morning and fifteen minutes of brisk exercise in well-selected movements, to start a forceful circulation and to surge the water through the digestive organs, are a daily necessity if one is to keep clean and strong within._ Exercises should be interspersed with deep breathing of _pure_ air. In breathing guard against drawing up the chest; make the muscular effort, while practicing full breathing, to expand the entire rib cage, back, front, and side. _It is as important to cleanse the body within as without. It is the method employed by all men and women who would retain strong vital forces to a ripe old age. They fully enjoy the mere_ LIVING. * * * * * [Sidenote: Ventilation] It is of the utmost importance that one not only forms the habit of correct, full breathing, but also sees to it that the air in the home, or in the place of business, is pure. A window opened at the top and bottom is essential in any place of business—or at least a draft through the room. There should be plenty of _circulating_ air in the sleeping room. Many restless nights are due to stagnant air. Teachers find that when they keep their schoolrooms well ventilated the children are less restless, their minds are more alert, they more quickly comprehend what is said to them, and that both they and the children are much less fatigued at the end of the day. Proper ventilation, and proper exercise have so definite a bearing on the condition of the body which we term “tired” that this subject properly follows. * * * * * [Sidenote: Fatigue, Disturbed Balance] Since the condition of the body in fatigue so materially affects the digestion, absorption, and assimilation of food, as well as the elimination of waste, it is not amiss to discuss it here. The habit of eating when overfatigued is almost sure to result in indigestion. Muscular or mental activity has called the blood away from the digestive organs and enough time has not elapsed to restore the equilibrium. The digestive organs are not in condition to take care of the food promptly and fermentation begins. A few minutes of active exercise and deep breathing for the brain worker, or a half-hour of rest after muscular activity, will equalize the circulation and restore the blood to the stomach and intestines.