OSSEOUS SYSTEM. 



185 



lation, where there is much circumduction. The circum- 

 duction of the femur is impeded by the distance of the 

 axis of motion from that of the bone being the whole 

 length of the neck of the thigh bone. 



Q. Give examples of articulations in which opposition 

 and circumduction are alone met with. 



Jl. In the angle of the jaw is a conspicuous one; you 

 see others in the wrist and radius, in the first phalanges. 



Q. Mention instances of the motion of opposition con- 

 fined to one direction, without circumduction and rotation. 



A. The knee, the elbow, second phalanges of the fin- 

 gers. These articulations are found in the middle joints 

 of limbs, 



Q. What conformation marks these articulations of 

 opposition, without circumduction or rotation? 



A. Prominences, such as condyles on the articular sur- 

 faces j or eminences and cavities fitted for each other; 

 these, with some other arrangements, prevent other mo- 

 tions than those just mentioned. These articulations are 

 remarkable for breadth of surface. 



Q. Why are luxations of these articulations more dan- 

 gerous than others? 



<ft. Because so many bands and ligaments are torn up 

 in their dislocation. 



Q. On what side is there the greatest motion in these 

 articulations? 



#. On that of flexion; hence the strength of the flexor 

 fibres, and also the location of the nerves and vessels for 

 security. 



Q. Can you give examples of articulation with rotatory 

 motion alone? 



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