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 1i- 
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 jomings 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- 
$i85( dee per aelgoy 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.—Tius 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 aconnecting 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 im 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. B 
