. Elementary anatomy and physiology : for colleges, academies, and other schools . Fig. 296. 533. Constitution. — lii constitution the hair con- sists of three distinct por- tions, an epidermis or outer portion, a fibrous, and a med- ullary portion. The epider- mis is arranged in the form of ring-Lke scales, which overlap each other like the shingles of a house, and is about soYoth of an inch thick (Fig. 294, d). Hence we see the reason why we can brush the hair in only one direction. The fibrous portion makes up the prin- cipal bulk of the hair, and is composed of longitudinal cells, which co
. Elementary anatomy and physiology : for colleges, academies, and other schools . Fig. 296. 533. Constitution. — lii constitution the hair con- sists of three distinct por- tions, an epidermis or outer portion, a fibrous, and a med- ullary portion. The epider- mis is arranged in the form of ring-Lke scales, which overlap each other like the shingles of a house, and is about soYoth of an inch thick (Fig. 294, d). Hence we see the reason why we can brush the hair in only one direction. The fibrous portion makes up the prin- cipal bulk of the hair, and is composed of longitudinal cells, which contain paint granules and air cavities which give the color to the hair. The medullary portion constitutes the central part of the hair (usually from one third to one fifth its diameter), and is made up of cells varying in diameter from F -oVo^n to coioo^ of an inch in diameter. 533 a. Color,—The color of the hair is thought by some to be owing to the iron contained in it, since it is said that there is the most of this metal in the darkest hair. 533 b. Physical Properties.—Hair is so elastic that it will stretch without breaking to nearly one third more than its original length. A single hair of the head will support six ounces without breaking. It readily absorbs moisture, and is dry and brittle or moist and soft, according as the skin or atmosphere is dry or moist. The beard is abundantly Highly Magnified Root of Hair, a, Shaft of Hair, b, c, Epidermic Sheath of Hair. £?, Dermic, or External Sheath of Hair, e, Epi- dermic Scales. 533. What three portions is each hair constituted of? What makes the principal pan of each hair? 683 a. What is it possible that the color of the hair is owing to? 533 b What is the strength of the hair?
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