Hygiene is the science of preserving health. The subject encompasses all agents affecting the physical and mental well-being of humans. It implies, in its personal aspect, the consideration of food and the consumption of water and other drinks. Clothes, work, exercise and sleep. Personal cleanliness, mental health and management of habits, and addictions. In its public aspect, it deals with climate, soils, characters, materials and layout, dwellings, heating and ventilation. Of waste removal. Medical knowledge on the incidence and prevention of diseases.