THE SKIN AS AN ORGAN OF SENSATION 



83 



dry, and unnucleated, or dead. The epidermis contains 

 no blood vessels, but in the deepest layers are found 

 minute terminations of some of the nerve fibers; and in 

 the same layers are the fine granules called pigment which 

 give color to the skin. This coloring matter is power- 

 fully affected by sun and wind, causing tan and freckles. 



Sweat-Duct 



Sebaceous Gland 



Horny layer < 

 Pigment layer 



Epidermii 



Dermis 



Fig. 49. Diagram of section of the skin. 



107. Hair and Nails are peculiarly developed forms of 

 the cuticle. Each hair is a long filament growing obliquely 

 from a little bulb called a papilla, lying in a hollow called 

 the hair follicle, which reaches down below the skin into 

 the areolar tissue beneath (Fig. 49). The part of a hair 

 buried in the skin is called its root; the remainder, the 

 stem, which tapers to a point. The stem is covered with 

 scales overlapping like the scales of a fish and project- 

 ing toward the point. When a hair is pulled out by the 

 root, a new one will grow again so long as the papilla is 

 uninjured. Each hair contains pigment granules which 



