OF THE ARTICULATIONS. 401 



tebrse, and those of the bones of the carpus and tarsus, whether 

 with each other or with the metatarsus and metacarpus. 



JLrthrodia differs from the preceding articulation, in this 

 respect, that the surfaces are less flat, the ligaments less tight, 

 and the motions freer and more numerous. Of this kind is the 

 temporo-maxillary articulation. 



Enarthrosis consists in the reception of a head into a cavity. 

 In this species the ligament is capsular, and the motions greatly 

 diversified. The articulation of the femur with the coxal bone 

 affords an example of it. 



These three first kinds of diarthrosis are orbicular or vague. 

 Their motions, which are more or less free, may take place in 

 all, or in many directions. The following species, on the con- 

 trary, are called alternate, because the motions are performed 

 in them only in two opposite directions. 



The rotatory diarthrosis, commissura trochoides of Fallo- 

 pius, is that which allows only motions of rotation; of which 

 kind are the articulation of the atlas with the second vertebra, 

 and that of the radius with the ulna. It is also called lateral 

 ginglymus. 



Ginglymus^ properly so called, or the hinge joint, also 

 called angular ginglymus, is the articulation in which there 

 are only two opposite motions, of which kind is the elbow 

 joint. In this species of diarthrosis, one of the bones com- 

 monly presents a pulley, and the other a corresponding sur- 

 face. There are generally two lateral ligaments. If the mo- 

 tion of extension is not to go beyond the line of direction of 

 the bones, these ligaments, in order to limit the motion, are 

 placed nearer the plane of flexion than the opposite plane. 



632. Accidental diarthrodial articulations are produced 

 under two different circumstances, after fractures of which the 

 pieces have not united, and after luxations which have not been 

 reduced. Both are very complex productions. The first kind 

 may be called supernumerary, the other supplementary articu- 

 lations. 



* I. F. Isenflamm and Schmidt. De Ginglymo. -Erlangx, 1785. 



