'50 



HUMAN PHYSIOLOGY 



CHAP. 



114. The Skin. The skin is a soft, tough, loosely 

 fitting covering of the entire surface of the body. It is 

 really somewhat like the mucous lining of the respira- 

 tory and digestive organs. Under the skin we find a 

 layer of fatty substance which serves as a kind of 

 blanket to keep us warm in cold weather, protect the 

 delicate parts beneath against injury, and to round out 

 the form, making it more beautiful. In old age, long 

 sickness, and starvation this fat may be used by the 

 cells, and the person grows thin and the skin becomes 

 wrinkled. 



The skin consists of a thin outer layer, the epidermis, 

 cuticle, or scarf skin, and of a thicker under layer, the 



dermis, cutis, or true 



Epidermis 



Hair . 



skin. 1 he raised 



part of a blister is 

 the epidermis. 

 When this is cut 

 away the dermis 

 may be seen below. 

 The epidermis 

 consists of round 

 and flat epithelial 

 cells closely packed 

 together so as to form a very firm but thin protecting 

 membrane for the dermis. On the soles of the feet 

 and the palms of the hands the epidermis is quite thick. 

 A callus may develop in the epidermis whenever it is 

 subjected to pressure for a long time. There are neither 

 nerves nor blood vessels in the outer layer, The rounded 



FlG. 76. A vertical section of the skin 

 (Newell). 



