304 



HITCHCOCK'S A X ATOMY 



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? 



