BONES 363 



and the numerous fine branches of the cells. Notice the Haversian 

 canal in the center of each circle. Examine also a specimen of 

 cartilage. 



1 60. Procure two slender bones which are exactly alike. Place one 

 in a hot fire for a few hours. This will burn out the cells and fibers 

 and leave only the lime. The bone is now very brittle and easily crum- 

 bles to pieces. Place the other in a bottle containing one part of 

 muriatic acid and ten of water. After a week this acid will have 

 removed the lime, leaving only the cells and fibers. The bone can now 

 be twisted and bent like a piece of flesh. 



161. Boil a leg bone of a half-grown animal until the flesh is re- 

 moved. Notice that a disk of cartilage extends nearly through the 

 shaft very near the ends. Possibly the end beyond it will come off. 

 Explain that the cartilage forms new bone which increases the length 

 of the shaft as long as the bone continues to grow. 



REVIEW TOPICS 



1. Show why bones are needed in the body. 



2. Describe the bones of the skull; of the spine; of the 



ribs ; of the arms ; of the pelvis ; and of the legs. 



3. Describe the appearance of a bone when sawed in two 



both lengthwise and crosswise. 



4. Show the advantage of having some of the bones 



hollow. 



5. Describe the microscopic appearance of bone. 



6. Give the uses of periosteum. 



7. Describe cartilage. 



8. Describe the changes which occur in bones with ad 



vancing age. 



9. Describe rickets. 



10. Describe the condition of a bone when broken, and 



tell how it is repaired, and how to care for a broken 

 limb. 



11. Show how a bone can become inflamed ; and how dead 



bone is replaced. 



