ARTICULATIONS OF THE BONES. 113 



The different kinds of articulations naturally admit of a 

 division into two classes. In the first may be placed the 

 true joints, which possess articular surfaces, surrounding li- 

 gaments, and a lubricating liquor. In the second, there are 

 no articular surfaces, the lines of junction either uniting by 

 contact, or by the intervention of some connecting sub- 

 stance. The joinings are secured by a continuation of the pe- 

 riosteum of the one bone, until it unites with that of the other. 

 The first class of articulations is usually termed Diarthro- 

 sis^KA per en^&^ov artus) ; the second has been long known by 

 the title of Symphysis. As the articulation by symphysis is 

 the most simple in its structure, we shall consider its charac- 

 ters in the first place. 



1. Articulation by Symphysis. This kind of junction 

 takes place either without, or by means of a connecting me- 

 dium. The articulation which has no connecting me- 

 dium, is usually termed Synarthrosis ; that in which there 

 is a connecting medium Amphiarthrosis. 



Synarthrosis is a mode of junction which admits of no 

 motion, the connecting surfaces coming into close and per- 

 manent contact. When two flat bones join each other by 

 their edges, the line of division is called the suture. It is 

 termed serrated when the edges are jagged, and when the 

 projections of the one edge are received into recesses in the 

 other. The bones of the human skull afford fine exam- 

 ples of this kind of junction. It is usually obliterated in 

 old age by the crevices being filled up with osseous mat- 

 ter. The dove-tail in architecture, is merely an imitation 

 of the serrated suture. When the edges of the bones are 

 even, and come in contact without indentation, the suture 

 is said to be harmonic. Examples of this kind occur in 

 the bones of the head in quadrupeds and birds. It is ad- 

 mirably exhibited in the junction of the plates of the crust 

 VOL. i. H 



