EPIDERMIS. 



333 



the deeper tissues, and (2), as a sensitive organ in the exercise 

 of touch, it is also (3), an important excretory, and (4) an 

 absorbing organ ; while it plays a most important part in (5) 

 the regulation of the temperature of the body. 



Structure of the Skin. 



The skin consists, principally, of a layer of vascular tissue, 

 named the corium, derma, or cutis vera, and an external cover- 

 ing of epithelium termed the cuticle or epidermis. Within 

 and beneath the corium are imbedded several organs with 

 special functions, namely, sudoriparous glands, sebaceous glands, 

 and hair-follicles ; and on its surface are sensitive papillae. The 

 so-called appendages of the skin the hair and noils are modi- 

 fications of the epidermis. 



Epidermis. The epidermis is composed of several layers of 

 epithelial cells of the squamous kind (p. 34), the deeper cells, 

 however, being rounded or elongated, and in the latter in- 

 stance having their long axis arranged vertically as regards 

 the general surface of the skin, while the more superficial cells 

 are flattened and scaly 

 (Fig. 109). The deeper FIG. 109. 



part of the epidermis, 

 which is softer and more 

 opaque than the super- 

 ficial, is called the rete 

 mucosum. Many of the 

 epidermal cells contain 

 pigment, and the varying 

 quantity of this is the 

 source of the different 

 shades of tint in the skin, 

 both of individuals and 

 races. The coloring mat- 

 ter is contained chiefly in 

 the deeper cells composing 

 the rete mucosum, and be- 

 comes less evident in them 

 as they are gradually 

 pushed up by those under 



L j J -t 1-1 Skin of the negro, in a vertical section, mag- 



them, and become, like nified 250diameters . ,, cutaneous papiii* ; 



their predecessors, flat- b> um i e rmost and dark-colored layer of oblong 

 tened and Scale-like (Fig. vertical epidermis cells; c, mucous or Malpig- 

 109). It is by this pro- Wan layer ; d, horny layer (from Sharpey). 



cess of production from 



beneath, to make up for the waste at the surface, that the 



growth of the cuticle is effected. 



