68 HITCH cock's anatomy 



cient movement in that direction. In the knee, however, 

 there are thirteen ligaments. 



154. Motions of the Joints. — The motions of the joint3 

 may be comprised under four principal divisions : Gliding, 

 Angular movement, Circumduction, and Rotation. 



155. Gliding. — Gliding movement is where the bones 

 simply slip over one another in the movement of the joint, 

 and exists to a greater or less extent in all the joints. 



156. Angular. — Angular movement may be performed 

 in four directions : forwards and backwards, called flexion 

 and extension, and inwards and outwards, called adduction 

 and abduction. A joint, as the finger, is said to be flexed 

 when it is bent upon itself, that is upon the palm of the 

 hand, and extended when it is stretched to its fullest extent, 

 or as in the finger, when it is made straight with the bones of 

 the fore-arm. Adduction means the bringing of one of the 

 extremities towards the body, or its fellow, while abduction 

 has the reverse signification. 



157. Circumduction. — Circumduction can be performed 

 only by the ball and socket joints. It consists in carrying 

 the limb about the joint in a circular plane, or in other 

 words, describing a circle about the joint as a center. 



158. Rotation. — Rotation is the movement of a bone upon 

 its own axis. A slight rotatory movement can be effected in 

 the joints of the shoulder and hip, but the best instance i3 

 that of the radius rotating against the articular head of the 

 humerus, producing the subdivisions pronation and supina- 

 tion. Pronation consists in rotating the fore-arm so that the 

 palm of the hand shall be downwards, and Supination the 

 reverse. Rotation is also observed 'in the movement of the 

 atlas upon the pivot of the axis. 



154. What are the four motions of the joints ? 155. Describe the Gliding movement. 

 156. In what four directions can Angular movements be ? 157. What is Circumduction ? 

 158. Describe Rotation. What is Pronation and Supination? 



