65 



results may follow, according to the further move- 

 ments which may be given to the head-ball and 

 socket-joint. 



First result — progression, as above described. 



§ 70. Second result — retrogression, if, instead of 

 at once beginning the alternate movement of the 

 light anterior point of application, the discharge 

 be refused. Then any further movement of the 

 left side of the head-ball being prevented, and the 

 attempted rotation of the right side of the socket 

 outward being continued, this latter movement will 

 be reduplicated in its effects on the left side of 

 the socket, and, being inoperative in reducing the 

 position of the ball on the same side, will, by 

 resiliency, take effect in raising the opposite (right) 

 side of the socket and carrying it forward. In the 

 same way, the ball motion of the left side being 

 reduplicated, the ball vrill be pressed down and 

 carried backward on the right side. We shall 

 thus have the head-joint in full position of the 

 alternate gathering, while the ribs, <fcc., still retain 

 the old one. 



The effect of these actions on the points of 

 gravity will be to throw, by the first, the appui, 

 off the convexes, upon the concaves of the first 



