186 



ARTICULATIONS. 



Gingtymus or Hinge-joint (yiyyxt^oj, a hinge). In this form of joint, the articular 

 surfaces are moulded to each other in such a manner as to permit motion only in 

 two directions, forwards and backwards, the extent of motion at the same time 

 being considerable. The articular surfaces are connected together by strong 

 lateral ligaments, which form their chief bond of union. The most perfect forms 

 of ginglymi are the elbow and ankle ; the knee is less perfect, as it allows a slight 

 degree of rotation in certain positions of the limb : there are also the metatarso- 

 phalangeal and phalangeal joints in the lower extremity, and the metacarpo-pha- 

 langeal and phalangeal joints in the upper extremity, 



Diarthrosis rotatorius or Lateral Q-inglymus. Where the movement is limited 

 to rotation, the joint is formed by a pivot-like process turning within a ring, or 

 the ring on the pivot, the ring being formed partly of bone, partly of ligament. 

 In the articulation of the odontoid process of the axis with the atlas, the ring is 

 formed in front by the anterior arch of the atlas; behind, by the transverse liga- 

 ment: here the ring rotates round the odontoid process. In the superior radio- 

 ulnar articulation, the ring is formed partly by the lesser sigmoid cavity of the 

 ulna ; in the rest of its extent, by the orbicular ligament : here the head of the 

 radius rotates within the ring. 



Subjoined, in a tabular form, are the names, distinctive characters, and examples 

 of the different kinds of articulations. 



S. Dentata, having 

 tooth-like processes. 



Interparietal su 

 ture. 



S. Serrata, having 

 serrated edges, like 

 the teeth of a saw. 



Interfrontal 



Sutura vera 

 (true), articulation 

 by indented bor- 

 ders. 



Sutura. Arti- 

 culation by pro- 

 cesses and indent-/ 

 ations interlocked 

 together. 



Synarthrosis or Im- 

 movable Joint. Sur- 

 faces separated by 

 fibrous membrane, no 

 intervening sy no vial 

 cavity, and immova-/ 

 bly connected with\ 

 each other. 



Example: bones of 

 the cranium and face, 

 except lower jaw. 



Sutura notha 

 (false), articulation 

 \by rough surfaces. 



su- 

 ture. 



S. Limbosa, having 

 bevelled margins, 

 and dentated pro- 

 cesses. 



Fronto-parietal su- 

 ture. 



S. Squamosa, form- 

 ed by thin bevelled 

 margins overlapping 

 each other. 



Temporo - parietal 

 suture. 



S. Harmonia, form- 

 ed by the apposition 

 of contiguous rough 

 surfaces. 



Intermaxillary su- 

 ture. 



Schindyksis. Articulation formed by the reception of a 

 thin plate of bone into a fissure of another. 



Rostrum of sphenoid with vomer. 



Gomphosis. An articulation formed by the insertion of 

 a conical process into a socket. 



Tooth in socket. 



