X\r 



other two, and by moving the fore-limbs and lower jaw on 

 a virtual ball and socket joint at the root of the neck, forms 

 the whole body into one curve. 



In this doubly compounded curve the hind and fore- 

 limbs are the appuis, the head the director, and the centre of 

 the lungs, made one in action with the head joints is the 

 centre of force. 



In man, by means of the collar bones and general shape, 

 such a perfect transmission to the feet of the appui on the 

 arms is effected that his natural position becomes one of 

 sole acutual appui on these latter, although a proper action 

 of the arms as a brace is still a condition of its perfection. 



In the higher animals the effects of the lines of torsion 

 forming in the central or ophidian curve pass to the breast 

 bone, which, as an artificial ground, supports the play of 

 the ribs ; the effects of the lines of torsion forming in the 

 combination of the central and loin curves, and of a partial 

 movement in the neck, pass to the pelvis and to the upper- 

 most part of the breast bone ; and the effects of the lines 

 of torsion forming in the combination of the neck curve 

 with the two others, making one curve of the whole, pass 

 to the limbs, and finally to the front limbs and lower jaw. 



To sustain the complicated movements of the higher 

 animals, the construction of the head joint is altered from 

 that of the snake, so that in addition to the general ball and 

 socket movement there is a superimposed movement of the 

 same kind, but divided into two parts, which belongs especi- 

 ally to the limbs and by which the neck concentrates the 

 whole upon its own curve, with the shoulder-blades and 

 lower jaw as bases of action, and, as was before said, with 

 the centre of the lungs and the head joint conjoined in 

 action as a focus of force. 



The lungs also are so constituted that they act for the 

 central curve in four parts, the two lower of which belong par- 

 ticularly to the lower sections of the torsion lines whose point 



