70 



A COURSE ON ZOOLOGY. 



The name articulation is given to the joining or fitting 

 together of the bones. All the bones of the human body, 

 with a single exception, the hyoid bone, are joined or 

 articulated together in the solid framework, called the 

 skeleton. The manner of articulation varies accord- 

 ing to the kind of move- 

 FIG. 38. ment that must take place. 



Fm. 38. 



STRUCTURE OP A LONG BONE. a, 

 head or epiphysis, filled with 

 spongy tissue ; 6, body or diaph- 



ysis. 



VERTICAL SECTION OF THE KNEE- 

 JOINT. 5, tibia ; 1, femur ; 3, pa- 

 tella; 2, 4, tendon, enclosing the 

 articulation in front and en- 

 closing the patella ; e, ligament 

 of the articulation ; s, synovial 

 membrane forming the articular 

 capsule. 



There are three principal kinds : fixed articulation, mixed 

 articulation, and mobile articulation. 



In the fixed articulation the bones are so joined as to 

 be incapable of any movement one on the other ; they 

 sometimes are joined by smooth edges, sometimes by 

 notches that dovetail together. Such are the articula- 

 tions of the cranial bones. 



In mixed articulation the bones do not touch, but are 



