=Underwear affects health.= Do you remember that we discovered the reason why one should be particular about the kind of underwear worn? We learned that ill health and fatigue are often caused by weight of clothing or by tight clothing causing lack of circulation or by clothing which prevents the skin from being ventilated. Textile materials and temperature of the body are closely related. We should learn to know which materials to select. Each person feels the need differently. Old people and little babies feel the heat or cold more than other people. Grandmother Stark usually feels cold and wears a shawl about her shoulders. Underwear must be chosen in relation to climatic conditions and also for conditions under which one wears them, for indoor or outdoor work. Each must study her health, the climate, her age, and occupation, and plan accordingly for the best kind. Underwear should be chosen which can be easily cleansed, also that which will permit plenty of air next to the skin. These properties of materials, as we call them, must be studied. The body, as we know, loses heat and water every day. Some materials conduct heat more rapidly than others; and some absorb and retain, while others eliminate, moisture more readily. Absorption and elimination differ with different fabrics. Linen is quicker than other fabrics to eliminate moisture. Wool on a dry body of a person who does not exercise freely feels warm and continues so as long as the skin does not give off more moisture than the wool can take up. If the body continues then to give off moisture, the heat of the body cannot escape and one does not feel comfortable. If a current of air or a draught occurs, the heat will be conducted quickly and the bodily temperature reduced too quickly. So underwear must not only prevent too great loss of heat by conduction, but must be so constructed as to conserve heat when it is needed. Heat is eliminated when materials conduct it. Porosity of materials prevents too great elimination. The air in the meshes or pores prevents this, as a still layer of air does not conduct heat readily. A loosely woven or knitted shawl is warmer under certain conditions than one which is firmer. Two lightweight garments are better than one heavy one because of the air space between. Wool is warm, but irritating to many people. It is not as cleanly as some fabrics, for it absorbs the body excretions and is not easily laundered. As it shrinks with use, it has fewer air spaces between the meshes. Any loosely woven or knitted underwear with air spaces is more hygienic than the closely woven.