XVI. THE SKELETON {continued). 



Joints. 



In the living body tlie various bones are closely iinited 

 to one another by various kinds of articulations or joints. 

 Some of these joints permit movement of the combining 

 bones, while others are rigid and form a fixed or immov- 



FlG. 98 — Forms of joints ; A, hinge joint (elbow) ; B, ball and socket joint (hip) ; 

 0, immovable joint (skull sutures). 



able joint. For convenience it is customary to classify all 

 joints as movable or immovable. To the first class belong 

 such unions as the shoulder and hip joints, the knee, 

 elbow, wrist and anlde joints, the finger, toe, and jaw 

 articulations, etc. Examples of the other class are found 

 in the sutures of the skull plates and the symphyses of 

 the pelvic bones with the sacrum. The word sutures 

 is restricted to dovetailed joints, and symphyses to those 

 in which the united bones have their edges simply pressed 

 together. 



244 



