T66 



ELEMENTARY PHYSIOLOGY 



Each hair consists of a root or bulb and a shaft or stem. The 

 root is imbedded in a recess of the skin called the follicle, which 

 is formed by a layer of the dermis, lined with a thin continuation 

 of the cuticle. These two layers form a sheath which invests the 



Fig. 153. Section through a Nail. 



i, epidermis ; 2, dermis. 



root of the hair so closely as to be often pulled out with the hair. 

 From the bottom of the follicle there rises a small papilla which 

 is supplied with blood-vessels, and this is the growing point from 

 which the hair is pushed forward by continual additions. The 

 shaft of the hair is, like the epidermis generally, devoid of blood- 



Fig. 154. Vertical Section throueh a small portion of a Nail. 

 Highly magnified. 



A, dermis ; B, rete mucosum ; c, the nail, composed of thickened epithelium. 



vessels and nerves. It generally consists of a central medullary 

 portion Q\ pith, surrounded by a fibrous cortical part. In some 

 hairs the medullary portion is wanting. 



Each hair is provided with small glands which secrete an oily 

 fluid to lubricate the hair and the surrounding skin. These are 



