CHAPTER II. 

 THE SKIN, ITS APPENDAGES AND ITS FUNCTION. 



The whole exterior surface of the body is covered by 

 the skin, an excreting and absorbing organ, which serves 

 as a protection to the parts beneath and is also the or- 

 gan of touch. It has two layers, a superficial and a 



Hair. 



Hair follicle. 

 Sweat gland. 



FIG. 11. Vertical section of skin. 



deep. The superficial layer, the epidermis or cuticle, 

 is composed wholly of epithelial cells, of which the deep- 

 est layer is columnar and moulded upon the papillary 

 layer of the derma, while the intermediate layers 

 are more rounded and the surface ones flat. The 

 deepest layer also contains the skin pigment, which 

 causes the variation in shade between the Indian, the 

 negro, and the white man. Below the epidermis, which 

 is chiefly protective, is the tough, elastic, and flexible 

 tissue of the derma or true skin, in which are vested 

 most of the activities of the skin. Its surface is covered 

 with papillae, which are more numerous in the more 

 sensitive parts. Each papilla contains one or more 

 capillary loops and one or more nerve fibers, while some 

 terminate in an oval body known as a tactile cor- 

 puscle. Beneath the papillae is the reticular layer, com- 

 posed of interlacing bands of fibrous tissue and contain- 



39 



