664. Silk is not as good a conductor of heat as cotton, nor does it absorb moisture to any considerable degree; its texture is smooth, and does not irritate the skin; consequently, when the garment of this fabric has sufficient body or thickness, it 303 is a good article for clothing. The greatest objection to its use is the disturbance of the electricity of the system, and its high price.
661. Give the properties of fur. As an article of dress, to whom are they best adapted? 662. Give the properties of woollen cloth. Is this a good article for clothing? What objection? What are the advantages of wearing flannels? 663. What are the qualities of cotton as an article of dress? 664. Of silk?
665. Linen is not only a good conductor of heat, and consequently a poor article of apparel, but it likewise absorbs the fluids carried from the system by the agency of the oil and perspiratory glands. When garments are made of this material, the body is not surrounded by a layer of air, but by one of moisture. This still further increases its power to conduct heat from the system, rendering it a very objectionable article of apparel, even in warm weather and in hot climates, where the dress is usually thin.
666. Clothing differs in its power of radiating heat. This is influenced by the color; those articles that radiate heat freely also absorb it readily. A black surface is a good radiator, while a white surface is not, because it reflects the calorific rays. It is obvious that those colors which render the transmission of external heat difficult, must impede the transmission of caloric from the body. Thus it is manifest, that light-colored apparel is best adapted for every season and every climate.
Observation. Coach-drivers are practically aware, that in cold weather, light-colored over-coats are warmest, except when they are exposed to the direct rays of the sun, or when seated before a warm fire. On the other hand, when the temperature is elevated, light-colored apparel is coolest, because the sun’s rays are then reflected.
667. The clothing should be of a porous character. The skin is not only an important agent in separating from the blood those impurities that otherwise would oppress the system and occasion death, but it exercises great influence upon the system, by receiving oxygen through its tissues, and giving 304 back carbonic acid in return. Consequently, the apparel should be made of a material that will permit free transpiration from the skin, and likewise convey the excreted fluids from the surface.
665. What is said of linen as an article of apparel? 666. Why is light-colored apparel best adapted for every season? What is said of the apparel of coach-drivers? 667. Why should we wear porous clothing?
668. The necessity for this is illustrated in wearing India rubber over-shoes. If they are worn over boots ten or twelve hours, not only the hose, but the boots will be moist from retained perspiration, and the residual matter left in contact with the skin may be reconveyed into the system by absorption, causing headache and other diseases. Cotton and woollen fabrics are not only bad conductors of heat, but are also porous; for these reasons, they are well adapted to transmit the excretions of the skin.
669. The clothing should be not only porous, but fitted loosely. The garments should retain a layer of air between them and the body. Every one is practically aware that a loose dress is much warmer than one which fits closely; that a loose glove is warmer than a tight one; and that a loose boot or shoe affords greater warmth than one of smaller dimensions. The explanation is obvious; the loose dress encloses a thin layer of air, which the tight dress is incapable of doing; and what is required, is, that the dress should be closed at the upper part, to prevent the dispersion of the warm air, by the ventilating current which would be established from below.
Observation. As the purpose of additional garments is to maintain a series of strata of warm air within our clothing, we should, in going from a warm room into the cold air, put on our defensive coverings some little time previous, in order that the layers of air which we carry with us may be sufficiently warmed by the heat of the room, and not borrowed from the body on exposure to the cold.