Describes 13 canons or concepts that are important to keep a healthy patient through the environment. Believed that with the right balance of these concepts, nature would be able to cure the body of any disease. These canons are ventilation and warming: thought that the person who breathes their air would become or remain sick. That it was necessary to have fresh air to eliminate any foul odors that came from the excrements. Nightingale also stressed the importance of room temperature. The patient should not be too warm or too cold. Should be controlled by the appropriate balance between burning fires and ventilations from the windows. Health of houses: no houses can be healthy without pure air, pure water, efficient drainage, cleanliness,
