Only the minimum amount of clothing that will secure warmth should be worn. Woolens protect most, but they require the least exercise of the temperature-regulating apparatus of the body. While wool is also highly absorbent of moisture, it does not give off that moisture quickly enough. Hence, if worn next to the skin, it becomes saturated with perspiration, which it long retains to the disadvantage of the skin. Consequently woolen clothing is best confined to overcoats and outer garments, designed especially for cold weather. The underclothes should be made of some better conducting and more quickly drying material, such as cotton or linen. In winter light linen-mesh and medium wool over that, or "double-deck" linen and wool underclothes, can be worn by those who object to either linen or wool alone. [Sidenote: Color] As to color, the more nearly white the clothes the better. This is especially true in summer, but there is believed to be some advantage in white at all seasons. Those who have learned to clothe themselves properly find that they have grown far more independent of changing weather conditions. They do not suffer greatly from extreme summer heat nor extreme winter cold. Especially do they note that "raw" or damp cold days no longer tax their strength. Section III--Outdoor Living [Sidenote: Out-of-door Air] But we must not depend altogether on ventilating our houses and our clothes. We must turn our thoughts toward an outdoor life. The air of the best ventilated house is not as good as outdoor air. Those who spend much of their lives in the open enjoy the best health and the greatest longevity. It is a great advantage to go into camp in summer and to live in the country as much as possible. Climate, of itself, is a secondary consideration. Not every one can choose the best climate in the world, and, after all, the main advantages of fresh air can be enjoyed in almost any locality. Even in a city, outdoor air is, under ordinary circumstances, wonderfully invigorating. [Sidenote: Dampness] The common prejudice against damp air greatly exaggerates its evils. While moderate dryness of air is advantageous, it seems nevertheless true that to live in damp, even foggy, air out-of-doors is, in general, more healthful than to live shut up indoors. [Sidenote: Outdoor Schools] Observations have shown that the pupils in outdoor and open-window schools are not only kept more healthy but learn more quickly than those in the ordinary schools. It is even claimed that tuberculous children in an outdoor school may make more rapid progress in their studies than the more normal children in a badly ventilated school. Parents should insist on fresh air for their children when at school. They should also insist on outdoor playgrounds. [Sidenote: Outdoor Recreations] For themselves, also, they should not neglect outings, picnics, and visits to parks. Whenever practicable, outdoor recreation should be chosen in preference to indoor recreation.