CHAPTER VIII. 



EXCRETION. 



Sweat Pore 



Epi- 

 dermis 



Papilla- 



THE SKIN AND ITS FUNCTIONS. 



The Skin throws off Perspiration. The energies of 

 the body heat and motion are produced by the oxida- 

 tion in its tissues. 

 During this process 

 waste products are 

 formed, which if 

 retained in the 

 body would cause 

 very injurious 

 effects. 



How does the 

 body get rid of 

 these substances ? 

 We have learned 

 that the lungs 

 throw off carbon 

 dioxid, water, and 

 certain putrescible 

 organic matter. 

 The skin is constantly throwing off wastes, collectively 

 called sweat, or perspiration. 



The Structure of the Skin. The skin has two layers, 

 the inner, or dermis, and the outer, or epidermis. A 

 bruise often loosens or breaks off a piece of the epidermis, 



130 



Dermis 



Sweat 

 Gland 



Blood 

 Tube 



Bulb 



Fig. 49. Vertical Section of the Skin. 



