KINDS OF MOVEMENTS 



327 



as the case may be, the joint towards the side on which 

 it is placed. Thus the biceps muscle is attached, at 

 one end, to the shoulder-blade, while, at the other end, 

 its tendon passes in front of the elbow-joint to the radius 

 (Figs. 92 and 99, Bi) : when this muscle contracts, there- 

 fore, it bends, or flexes, the forearm on the arm. At the 

 back of the joint there is the triceps {Tr, Fig. 99) : when 



Fig. 102. 



The vertebral column in the upper part of the neck laid open to show, 

 a, the check ligaments of the axis ; fc, the broad ligament which extends 

 from the front margin of the occipital foramen along the hinder faces of 

 the bodies of the vertebrae ; it is cut through, and the cut ends turned 

 back to show, c, the special ligament which connects the point of the 

 " odontoid " peg with the front margin of the occipital foramen ; /, the 

 atlas ; //, the axis. 



this contracts, it straightens, or extends, the forearm on 

 the arm. 



In the other extreme form of articulation — the ball and 

 socket joint — movement in any number of planes may be 

 effected, by attaching muscles in corresponding number 

 and direction, on the one hand, to the bone which affords 

 the socket, and on the other to that which furnishes the 

 head. Circumduction will be effected by the combined 

 ind successive contraction of these muscles. 



