55 



take place, beginniiig with the rearmost appui, 

 in the succession mentioned. 



It ^\all be remarked that the coui-se of the cutting 

 line coming from the opposite side, for the ribs on 

 the posterior halves, the line first takes effect in the 

 trunk, and thence ascends to the articulations, where- 

 as, coming for the anterior halves fi'om their own 

 sides, it descends at the posterior cross-line, and at 

 the head-ending of the posterior " winding line,'" from 

 the articulations, into the trunk. 



In these movements the secondary section work- 

 ing of the anteiior ^nnding line, in the posterior C, 

 represents the turning (a) of the head condyle. Its 

 primary section working, including the action of 

 the anterior cross-line end, represents (a ' ) the pas- 

 sage of the condyle pressure across the head-joint 

 to its front. The secondary section working of 

 the posterior winding hne in the anterior C, repre- 

 sents the turning (h) of the socket by its outer 

 edge. Its primary section working in the posterior 

 O, which partially anticipates the secondary, be- 

 cause the posterior cross-line end is checked in its 

 movement, represents (b ' ) the passage of the socket 

 action across the head-joint to the front. 



On the sides, also, the crossing of these lines 

 could be projected as ball and socket surfaces, the 



