574 



THE SKIN. 



[CH. XXXVIII. 



may be present in both medulla and fibrous layer, and cause the 

 hair to look white by reflected light. The grey hair of old age, 

 however, is produced by a loss of pigment. 



The root is enlarged at its extremity into a knob, into which 

 projects a vascular papilla from the true skin. 



The hair follicle consists of two parts, one continuous with the 

 epidermis, called the root-sheath, the other continuous with the 



Fig. 444. Transverse section of a hair and hair-follicle made below the opening of the 

 sebaceous gland, a, medulla or pith of the hair ; ft, fibrous layer ; c, cuticle ; d, 

 Huxley's layer ; e, Henle's layer of internal root-sheath ; / and g, layers of external 

 root-sheath, outside of g is the basement membrane or hyaline layer; h, dermic 

 (fibrous) coat of hair follicle; i, vessels. (Cadiat.) 



dermis, called the dermic coat. The two are separated by a 

 basement membrane called the hyaline layer of the follicle. The 

 root-sheath consists of an outer layer of cells like the Malpighian 

 layer of the epidermis, with which it is directly continuous (outer 

 root-sheath), and of an inner horny layer (inner root-sheath), 

 continuous with the horny layer of the epidermis. The inner 

 root-sheath consists of three layers, the outermost being com- 

 posed of long, non-nucleated cells (Henle's layer), the next of 

 squarish nucleated cells (Huxley's layer), and the third is a cuticle 

 of scales, imbricated downwards, which fit over the scales of the 

 cuticle of the hair itself. 



A small bundle of plain muscular fibres is attached to each 



