THE SKIN 169 



QUESTIONS ON LESSON XXVIII. 



1. Of what parts is the skin composed ? How do these differ from each 



other ? 



2. What are the pores of the skin ? What purpose do they serve ? 



3. What is the difference between the skin of a European and that of a negro ? 



4. What is the use of the epidermis ? 



5. What purpose is served by the fatty tissue imbedded in the deeper portion 



of the dermis and in the tissue beneath it ? 



6 Where are the sweat glands situated ? What are their uses ? Describe 

 briefly the structure of these glands. 



7. What do you know about the perspiration ? What circumstances determine 



the amount of perspiration secreted ? 



8. How much perspiration is secreted daily ? How is it that we sometimes 



see it on the surface of the skin, while at other times it is insensible ? 



9. Compare the function of the skin with that of the lungs. 



10. What is the structure of a nail ? How does a nail grow ? 



11. Describe the structure of a hair, and say how the hair is connected with 



the skin. 



12. What are sebaceous glands ? What is their use ? 



13. By what means is the hair made to ' stand on end ' ? 



LESSON XXIX. 

 THE KIDNEYS. 



THE kidneys, two in number, are situated at the back of the 

 abdomen, one on each side of the upper lumbar vertebrae. They 

 are deeply seated in the loins, behind the peritoneum, and are 

 held in this position by their own vessels, and by a quantity of 

 areolar tissue which usually contains much fat. They measure 

 about 4 inches in length, z\ inches in width, and i^inch in thick- 

 ness, their weight being about 4^ ounces each. 



The kidneys are arranged with their concave surfaces directed 

 towards the vertebral column ; and the right kidney, which is 

 usually shorter and thicker than the left, is generally a little lower, 

 probably on account of the downward extension of the large right 

 lobe of the liver. 



The surface of the kidney is smooth, and of a deep red colour. 

 It is covered with a thin fibrous coat the capsule which invests 

 the organ closely, but which can easily be detached. 



In the concave surface of the kidney there is a longitudinal 

 depression called the hilus, at which the vessels and nerves enter 

 or pass out. The concavity of the kidney is usually filled in with 

 areolar and fatty tissue, through which the vessels pass to and 

 from the organ ; and by carefully removing this substance three 

 vessels may be traced to their entrance into the kidney. 



