xii THE SKIN AND THE KIDNEYS 165 



SUMMARY OF THE MAIN POINTS 



1. The skin consists of an outer layer, the epidermis, and 

 below this a thicker layer, the dermis or true skin. 



2. The most important function of the skin is to protect 

 the body against foreign substances. It is firm and tough, but 

 very pliable. 



3. A thick layer of fatty tissue is deposited under the der- 

 mis. This serves as a food supply in case of sickness, as a 

 blanket to keep us warm in cold weather, and to give round- 

 ness and beauty to the human body. 



4. The epidermis consists of epithelial cells held together 

 by a small amount of cement. No blood vessels, nerves, or 

 lymphatics occur in it. 



5. In the deeper parts of the epidermis are found the pig- 

 ment cells that give color to the skin. 



6. The dermis is well supplied with blood vessels, lymphat- 

 ics, and nerves. 



7. The sweat glands of the skin are for the purpose of re- 

 moving water, salt, and small amounts of other wastes. About 

 a quart of perspiration is excreted on a temperate day. 



8. The oil glands secrete a small amount of oil which lubri- 

 cates the hair, keeps the skin soft and pliable, and protects the 

 body against moisture. 



9. The skin is the most important organ for controlling the 

 body temperature. 



10. The nails and hairs are two important structures made 

 of highly modified epidermis. They serve to protect and 

 beautify the body when properly cared for. 



11. The functions of the skin are to serve as a protecting 

 covering ; to regulate the body temperature ; to remove certain 

 waste products ; to furnish the sense of touch and temperature ; 

 to aid in respiration ; and to act as an absorbing surface. 



