AETHEOLOGY. 99 



PART III— ARTHROLOGY. 



Articulations are tlie unions of the component parts 

 of the basement structures, the means by which such parts 

 are enabled to play on one another in adaptation to the 

 various movements of the individual. These are of three 

 kinds, moveable, imrtially moveable, and fixed. The fixed or 

 synarthrotic joints are those which in the young animal 

 are moveable, but become obliterated later on in life ; they 

 mainly serve for connection ; motion between the parts 

 forming them is but slight, it is impossible after full 

 development of the bones. They are of four hinds, the most 

 marked examples of which may be found in the cranium. 

 They consist of the coaptation of edges or surfaces of 

 bones with the intervention only of periosteum. The sim- 

 plest forms afford the most firm centres of connection. 



Sutura is the apposition of two edges or surfaces, more 

 or less complete, by the adajDtation of prominences on one 

 piece to depressions on the other. This adaptation may be 

 by the juxtaposition of irregular surfaces, sutura squamosa, 

 which may be more or less rough ; examples of this may 

 be seen in the union of the malar with the frontal bone ; 

 or it may be by the dovetailing of two jagged edges, sutura 

 serrata vel dentata. The latter name is applied when the 

 jagged margins resemble the line formed by the edges of a 

 dog's molars. 



Harmonia is the apposition of two edges of bone, which 

 may be roughened, but are not jagged ; they therefore 

 simply are in contact, and connection between the bones is 

 simply by continuity of periosteum, as in the union between 

 two ossa nasi. 



Gompliosis is the insertion of a peglike process of one 

 l>one into a corresponding cavity of another. It is rare ; 

 the connection of the teeth with the jaws and of the rib 

 with its cartilage are examples. 



Schindylesis is the union of three l)ones, by the attach- 



