94 BONES. 



laminae and all the fibres of which are incrusted with a strong 

 matter composed of lime united to particular acids, (phosphoric 

 acid, &c.) When bone is burned, the stony matter remains alone, 

 and is reduced to powder by slight friction, and when bone is 

 steeped in a particular liquid, which has the property of dissol- 

 ving this stony matter, (hydrochloric acid,) it is reduced to the 

 state of a flexible cartilage 



6 In infancy bone is at first cartilaginous, and before ossifica 

 tion is complete, each one is formed of several distinct pieces, 

 which run together, as it were, at a later period 



7. The bones that constitute the skeleton are united one to 

 the other by arlictilatiotts or joints, which change their name 

 according to their form. 



8. If the articulation that unites two bones permits them to 

 move, one on the other, it is called a moreablc articulation. 



9. If on the contrary, the articulation is merely to secure the 

 solidity and firmness of the bones, it is called immoveable. 



10. The more moveable an articulation, the less solid it is, and 

 vice versa ; the more solid, the less mobility it possesses. 



11. The immoveable articulations take place through the 

 medium of asperities which dove-tail together ; this mode of 

 union is called a suture. 



Ftg. 36. 12. The articular surface of the move- 



a ac c l able Dones > (My- 36.) is covered with 

 ', an elastic substance which is capable 

 of bearing the strongest pressure, and 

 which deadens the shocks they receive ; 

 this substance is called cartilage. The 

 articulations are also supplied with a 

 viscous fluid called synovia, designed 



Explanutionof Fip. 36. The articulation (joint) of the shoulder, show- 

 ing how the moveable bones are attached to each other, o. the scapula. 

 t. the head of the humerus, c. the capsule of the articulation opened, g. 

 glenoid cavity of the scapula, a. the acromion process of the scapula, articu- 

 lating ( jointing with the clavicle, (cl.) ac. coracoid process of the scapula, 

 -/. ligament extending from this process to the clavicle. 



6. What is the condition of bone in infancy ? 



7. How are bone" joined together ? 



8. What is a moveahle articulation ? 



9. What is meant by an immoveable articulation? 



10. What kind of articulation is most solid ? 



11. What is a suture? 



12. How are the articulating surfaces of moveable bones protected from 

 the effects of friction ? What is the use of synovia ? 



