71 



Third. The forcing of the movement [h'). Here 

 it will be remembered that the cross-line end being 

 held in check (§ 32), the reaction to the right pos- 

 terior point of application was at the head. The 

 movement forward, across the joint of the socket 

 will, therefore, first be equalized for both sides, 

 and, then, the primary section drawing, the pos- 

 terior end of the cross-line will be brought into 

 place to the front, and the point which should 

 serve as posterior cross-hne end in the left pos- 

 terior winding line be likewise similarly adjusted. 

 The requisite displacement for both now occurs to the 

 front. 



Fourth. The forcing of (b), i. e., of the outivard 

 rotation of the right side of the socket, compl-etes the 

 adjustment of the cross-line ends, forms the left 

 convex of the anterior C equal with that of the 

 right side, and finally equalizes the reciprocal press- 

 ure of head-ball on both sides of the head-joint. 



Remarks. — Referring to what was said in regard 

 to the lines of traction depending for existence 

 upon the relative situation of points in the skel- 

 eton, it is evident that when the super imposition of 

 twists (§ 71) is completed, the diagonal lines may 

 disappear, and tJie tractions become collateral. The 



