606 



THE SKIN AND ITS APPENDAGES 



[CH. XL. 



hairs the centre is occupied by a medulla, formed of rounded cells 

 containing eleidin granules. Minute air-bubbles may be present in 

 both medulla and fibrous layer, and cause the hair to look white by 



* C 



reflected light. The grey hair 

 of old age, however, is pro- 

 duced 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 epi- 

 dermis, called the root-sheath, the other 

 continuous with the 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 

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

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



FIG. 389. Vertical section of skin. 

 A. Sebaceous gland opening 

 into hair follicle. B. Muscu- 

 lar fibres. C. Sudoriferous or 

 sweat-gland. D. Subcutaneous 

 fat. E. Fundus of hair follicle, 

 with hair papilla. (Klein.) 



