After sleeping in a room in which the air is impure, one arises fatigued, because the supply of oxygen is insufficient to liberate the energy required for circulation and catabolism. _Harmony_, either mental or physical, _is rest_. With a little more intelligence in keeping up the supply of oxygen, in establishing correct breathing habits, and in understanding the law of distribution of circulation, which means the harmony of forces, this tired world could not only draw a deep, restful breath, but would be invigorated to enjoy life to the full. * * * * * [Sidenote: Sleep] During sleep all the processes of the body are retarded. Blood flow and breathing become slower and the digestive processes slacken. For this reason, if one goes to bed immediately after eating a heavy meal, digestion is retarded. This may react on the nerves, producing fitful or unrestful sleep. Fever or nightmare may result. The annoying, sleepy feeling which often comes on after a meal indicates a lack of balance in the system—usually that more food has been eaten than the body requires. Lessening the amount of food and increasing the exercise and the oxygen, and cleansing the intestinal tract will prevent it. On the other hand, if the alimentary tract is entirely empty, sleep may not come because there is too much blood in the brain. A glass of hot milk or cocoa, or a couple of crackers, will call the blood to the stomach and will often aid sleep. After eating a heavy meal, from three to three and a half hours should elapse before retiring for sleep. * * * * * [Sidenote: Influence of the Mind] The state of mind has much to do with regulating the digestive system. Cheerful thoughts keep the nerves of the entire organism in a normal state, while disagreeable thoughts cause a tense, unnatural condition. The nerves of the digestive organs are affected by the tenseness of the mind, just as are the nerves to any other part of the body. As an illustration, if one continuously thinks ugly, disagreeable thoughts, these thoughts affect the chemical activities of digestion and assimilation, resulting in an excess of acid in the blood, and actual illness results. Digestion and assimilation being impaired, the tissues become weakened, they lose their resistance, and, as a result, the organs may prolapse. We then have what is called a “vicious circle”—the mind affects the body unpleasantly and the body the mind. We are learning to consider many factors in looking for the causes of disease, particularly those due to general weakness, or a disturbed mental state. Even the temper shown in a crying babe may affect its digestion by disturbing the normal chemical activity.