THE LIVER 



161 



4. Describe the gall-bladder. Where is it situated ? What is its use ? What 



does it contain ? Give the names of the vessels connected with it. In 

 which direction does the fluid move in these vessels ? Illustrate your 

 answer by a sketch. 



5. What is the nature of the fluid contained in the portal vein ? Where does 



this fluid come from ? 



6. How is it that the liver discharges less blood than it receives ? In what 



respects does the blood discharged differ from that received ? 



7. What is a portal canal ? What does it contain ? 



8. What is the size of an hepatic lobule ? Describe the arrangement of its 



constituent parts. How does the blood circulate through a lobule ? 



9. Where is the bile formed ? Describe the course of its circulation (a) when 



the digestive organs are active, and (b] after fasting. 



10. What are the chief functions of the liver? 



11. What is the quantity of bile secreted daily ? What becomes of all this ? 



12. What are the chief uses of the bile? (See Lesson XIX.) 



13. What is glycogen ? Where is it formed, what is its use, and what becomes 



of it? 



LESSON XXVIII. 

 THE SKIN. 



THE skin or integument forms a protective covering over the 

 whole of the body. It consists of two layers, the epidermis and 

 the dermis. 



The epidermis (Gr. epi, upon ; and 

 derma, the skin) cuticle, or scarf-skin, 

 covers every part of the dermis or true 

 skin. It is hard and horny, and composed 

 of minute scales which are being continu- 

 ally worn away from the surface. The 

 thickness of the epidermis varies in diffe- 

 rent parts. In the palms of the hands and 

 the soles of the feet parts which are much 

 exposed to great pressure it is as much 

 as ^ of an inch, while in some parts the 

 thickness is less than -^ of an inch. 



The surface of the epidermis presents 

 a multitude of minute openings when viewed 

 with a magnifying glass. These are called 

 the pores of the skin, and are really the 

 openings of the ducts of little glands which 

 secrete the sweat or perspiration. 



The epidermis itself contains no blood-vessels and but few 

 nerves, its office being simply to protect the deeper layer of the 



Fig. 149. Magnified 

 View of the Epi- 

 dermis, showing 

 the Fores. 



