THE SKELETON 341 



Exercises. i. State the main purpose of the skeleton. What is the 

 necessity for so many bones in its construction? 



2. How may the per cent of animal and of mineral matter in a bone 

 be determined? 



3. What properties are given the bones by the animal matter? 

 What by the mineral matter? 



4. Locate the bone cells. What is their special function? 



5. State the plan by which nourishment is supplied to the bone cells 

 in different parts of the bone. 



6. Give the uses of the periosteum. 



7. State the purpose of the Haversian canals. Of the canaliculi. 



8. Give functions of the spinal column. 



9. Name the different materials used in the construction of a joint 

 and the purpose served by each. 



10. Name four mechanical devices, or machines, found in the skele- 

 ton and state the purpose served by each. 



11. Name one or more of the body machines not located in the 

 skeleton. 



12. Of what advantage is the peculiar shape of the lower jaw? Of 

 the ribs? Of the bones of the pelvic girdle? 



13. State the importance of preserving the natural form of the 

 skeleton. How are unnatural curves produced in the spinal column? 



14. How may slight deformities of the skeleton be corrected? 



15. What different systems are employed in the body in the produc- 

 tion of motion? What is the special function of each? 



PRACTICAL WORK 



To obtain clear ideas of the form and functions of the bones, a 

 careful examination of a prepared and mounted skeleton is necessary. 

 Many of the bones, however, may be located and their general form 

 made out from the living body. Bones of the lower animals may also 

 be studied to advantage. 



Experiments to show the Composition of Bone. i . Examine a 

 slender bone, like that in a chicken's leg. Note that it resists bending 

 and is difficult to break. Note also that it is elastic that, when slightly 

 bent, it will spring back. 



2. Soak such a bone over night in a mixture of one part hydrochloric 

 acid and four parts water. Then ascertain by bending, stretching, and 



