SUBDIVISION INTO THREE CLASSES. 



1ST 



Ani[>/iiartlirosis, 

 Mixed Articulation. 



1. Surfaces connected by nbro-cartilage, not separated by 

 synovial membrane, and having limited motion. Bodies of 

 vertebrae. 



2. Surfaces covered by nbro-cartilage ; lined by a partial 

 synovial membrane. Sacro-iliac and pubic sympliyses. 



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Arihrodia. Gliding joint ; articulation by plane surfaces, 

 which glide upon each other. As in sterno- clavicular and 

 acromio-clavicular articulations. 



Enarthrosis. Ball-and-socket joint ; capable of motion in 

 all directions. Articulation by a globular head received into 

 Diarthrosis, ' a cup-like cavity. As in hip and shoulder -joints. 

 Movable Joint. / Ginglymus. Hinge joint; motion limited to two directions, 

 forwards and backwards. Articular surfaces fitted together 

 /so as to permit of movement in one plane. As in the elbow, 

 /ankle, andjoiee. 



Diarthrosis' rotatorius. Articulation by a pivot process 

 1 turning within a ring, or ring around a pivot. As in supe- 

 \rior radio-ulnar articulation, and atlo-axoid joint. 



THE KINDS OF MOVEMENT ADMITTED IN JOINTS. 



The movements admissible in joints may be divided into four kinds, gliding, 

 angular movement, circumduction, and rotation. 



Gliding movement is the most simple kind of motion that can take place in a 

 joint, one surface gliding over another. It is common to all movable joints ; but 

 in some, as in the articulations of the carpus and tarsus, is the only motion per- 

 mitted. This movement is not conniied to plane surfaces, but may exist between 

 any two contiguous surfaces, of whatever form, limited by the ligaments which 

 inclose the articulation. 



Angular movement occurs only between the long bones, and may take place in 

 four directions, forwards or backwards, constituting flexion and extension, or inwards 

 and outwards, which constitutes abduction and adduction. Flexion and extension 

 are confined to the strictly ginglymoid or hinge-joints. Abduction and adduction, 

 combined with flexion and extension, are met with only in the most movable 

 joints ; as in the hip, shoulder, and metacarpal joint of the thumb, and partially 

 in the wrist and ankle. \ 



Circumduction is that limited degree of motion which takes place between the 

 head of a bone and its articular cavity, whilst the extremity and sides of a limb 

 are made to circumscribe a conical space, the base of which corresponds with the 

 inferior extremity of the limb, the apex with the articular cavity ; and is best seen 

 in the shoulder and hip-joints. 



Rotation is the movement of a bone upon its own axis, the bone retaining the 

 same relative situation with respect to the adjacent parts : as in the articulation 

 between the atlas and axis, where the odontoid process serves as a pivot around 

 which the atlas turns ; or in the rotation of the radius upon the humerus, and also 

 in the hip and shoulder. 



The articulations may be arranged into those of the trunk, those of the upper 

 extremity, and those of the lower extremity. 







