36 THE HUMAN BODY. 



3, How do blood-vessels and nerves get into a bone ? What are 

 the Haversian canals ? 



SECTION VI. 1. What is the chemical composition of bone? 

 How can the animal and mineral constituents be separated? Why 

 do the bones of old people break more easily than children's ? 



SECTION VII. 1- What three kinds of joints are there in the 

 body? 



2, Of the movable joints, what varieties are there? 



3, What are the essential parts of a joint? How does a joint 

 oil itself? 



4, Why are some people's joints looser than those of other 

 people ? 



5, What is a sprain ? 



SECTION VIII. 1. Are bones constantly changing, like other 

 tissues ? 



2. What helps, and what may hinder, their growth ? 



