93 



the movement forward of the head-ball in the 

 socket (§ 67 a'). 



At the following combination of this " primary 

 section " into the '' composite spine," in order to 

 keep the head steady, the above left movement 

 must be met by resistance along the inner edge of 

 the left condyle, and the movement forward by 

 the moving of the condyle along this line. 



Suppose next the right posterior line to form 



IN THE OPHIDIAN S. 



Its secondary section refleeied;!action — the cross- 

 line end being displaced, (§ 32) — will take its first 

 re-action against the anterior plane^section of the 

 spine (in which the anterior point of application 

 moved) bringing the posterior left comer of the 

 sternum to the right, as the false ribs come on 

 their inner bearings, and so far as it affects the 

 upper part of the sternum, carrying it further to 

 the left. The change in the [centres^ of gravity 

 ^will commence the change of the left hind and 

 right fore-legs to their inner bearings. 



At the following combination of this section into 

 the " composite spine," the tui'ning of the socket 

 against the anterior end of the left condyle would 

 occur, as the right socket^is withdrawn ; but as 



