Chap. YI] 



ARTICULATIONS 



87 



loid and the saddle joints admit of motion in every direction except 

 that of axial rotation. 



The different kinds of movement of which bones thus con- 

 nected are capable are : — 



1. Flexion. — A limb is flexed, when it is bent. 



2. Extension. — A limb is extended, when it is straightened out. 



3. Abduction. — This term generally means drawn away from 

 the middle line of the body. 



4. Adduction. — This term generally means brought to or 

 nearer the middle line of the body. 



Both abduction and adduction have a different meaning when 

 used with reference to the fingers and toes. In the hand the 

 imaginary line is supposed to be drawn through the middle finger ; 

 and in the foot through the second toe. 



5. Rotation. — INIeans made to turn on its own axis. 



6. Circumduction. — Means made to describe a conical space 

 by rotation around an imaginary axis. 



No part of the body is capable of perfect rotation, as a wheel, 

 for the simple reason that such motion w^ould necessarily tear 

 asunder all the vessels, nerves, muscles, etc., which unite it with 

 other parts. 



Sprain. — A wrenching or twisting of a joint accompanied 

 by a stretching or tearing of the ligaments or tendons is called 

 a sprain. 



Dislocation. — If in addition to a sprain, the bone is displaced, 

 the injury is called a dislocation. 



SUMMARY 



Articulations or Joints — connections existing between bones. 



1. Sutura. — Articulations by 



pro- 



cesses and indentations interlocked 

 together. A thin layer of fibrous 

 tissue is interposed between the 

 bones. Sutures may be dentated, 

 dove-tailed ; serrated, saw-like ; 

 squamous, scale-Uke ; harmonic, 

 smooth; and grooved, for the re- 

 ception of thin plates of bone. 

 , Synchondrosis. — Temporary 

 joint. Cartilage between bones 

 ossifies in adult life. 



