100 OUTLINES OF EQUINE ANATOMY. 



ment of the edge of one Lone into a groove formed by part 

 of the edges of the others, the rest of the union between 

 the other two being by suture. Such is the attachment of 

 the vomer to the palatine processes. 



Partially moveable or ampMarthrotic joints are those 

 which, while admitting a small amount of motion, also 

 afford firm union. This is brought about by insertion 

 betv^een two roughened surfaces or edges of bone of a piece 

 of fibro -cartilage, the perichondrium of which is con- 

 tinuous with the periosteum of the bones connected. 

 Sooner or later, in different individuals, the cartilage 

 becomes ossified and the union complete. Such is the 

 connection of the ossa innominata by means of the sym- 

 physis, and of the two halves of the inferior maxilla, 

 which " grow together," forming the symphysis inferioris 

 maxillae. In the case of the articulations between the 

 bodies of the vertebrae we see permanent amphiarthrotic 

 joints. Some of these joints are strengthened by connecting 

 ligaments. 



Diarthrotic, synovial, or freely moveable joints are those 

 in which the component parts glide more or less upon each 

 other. They present cavities lined by synovial membranes, 

 the surfaces of the bones in apposition are coated with 

 articular cartilage, and are maintained in apposition by 

 ligaments. These ligaments may be interosseous, situated 

 between the bones, running from a roughened spot on the 

 surface of one bone to a corresponding part of its fellow ; 

 examples may be seen between many of the bones of the 

 hock and knee ; connecting, running from the outer surface 

 of one bone to that of the other. Capsular, broad, expanded 

 bands of white fibrous tissue serving to strengthen and 

 protect the synovial membranes of a diarthrodial joint. 

 Annular, extending round a complex joint attached to all 

 the prominent bony points it presents, keeping in position 

 its surrounding structures ; generally consists of a broad 

 ligamentous expansion, sometimes simply of a small white 

 fibrous band ; examples of both these forms may be seen in 

 the hock. The motion between synovial surfaces may be 

 simply an almost imperceptible gliding ; where this is the case 

 the joint is arthrodial. Others admit of more or less exten- 

 sive motion in two ways — either abduction and adduction 

 (motion from or towards the longitudinal vertical plane of 

 the body), or elevation and depression (motion to or from 



