Perspiration

in physiology, a liquid given off by the glands of the skin. A more common but less elegant term is sweat. The sweat glands are slender tubes of considerable length. The lower portion is coiled in a sac amid the innermost cells of the skin. This follows a wavy path through the cutis or true skin, and reaches the surface in spirals--twisted like a thread. The knotted coil within the sac absorbs moisture and wastes from the blood in the capillaries by which it is surrounded. The fluid thus gathered is discharged at the outer surface of the skin. The liquid consists chiefly of water, but it contains phosphorus, sulphur, and salt also, together with traces of waste matter that impart disagreeable odors.

A person perspires at all times. If a piece of glass be held against the body it will reveal a trace of moisture. In case of heat or severe exertion the amount of perspiration is sufficient to become visible. Authorities claim that a normal person under ordinary conditions gives off from two to three quarts of invisible perspiration daily. This point is determined chiefly by noting loss of weight. An athlete may lose several pounds in a very short time, as during a boat race.

Perspiration performs its greatest service in cooling the body. It is a well known principle of physics that evaporation makes way with a large amount of heat. In warm weather the discharge of perspiration is rapid. By its evaporation the surface of the body is cooled off and the body is prevented from overheating. Under ordinary conditions the flow of perspiration and the consequent rate of evaporation are regulated by nature so as to maintain a uniform temperature of about 98 deg. Fahrenheit.

A horse has an active perspiratory system and may be driven rapidly in warm weather. A hog has a sluggish respiratory system. It sweats scarcely at all and dies of overheating if driven in warm weather.

Bathing opens the respiratory pores. For people who do not work hard enough to perspire visibly bathing is a requisite of health. One who earns his daily bread by the sweat of his brow requires to bathe rather as a matter of bodily cleanliness. The flow of perspiration is connected closely with the action of the nervous system. Fear, nervous weakness, mental anguish, or physical agony may cause beads of perspiration to appear.