81 



tions, before reaching the breast-bone, become 

 united on each side into a single one, and the two 

 resulting continuations are attached to the hinder 

 — in man the lower — end of the breast-bone. 



The true ribs diminish in length and capability 

 of independent movement as thej approach the 

 neck, so that the upper ones have \erj httle be- 

 yond a hinge-like movement at the spine, as 

 their front ends are raised when the breast-bone 

 is drawn up by muscles from above, in connection 

 with the outer tui'ning of the false ribs below. 



In man there are seven true and five false ribs ; 

 in the horse, eight true and ten false ; in the Hon 

 and cat, nine true and four false ; in the gii-affe, 

 eight tme and six false ; variations which, no 

 doubt, favour certain pecuharities in the motion of 

 each animal. 



In this way the breast-bone answers, at its 

 sides, to only a part of the length along which the 

 rib sockets extend, being, in fact, only imder those 

 of the true ribs. 



At its rear, however, the breast-bone is power^ 

 fully acted on by the false ribs, and these, prin- 

 cipally, give it direction and push it forward, the 

 false ribs of either side driving their motion 

 through the breast-bone up to the head by a con- 



