234 NATURAL THEOLOGY. 



tural bodyof the necessity for elasticity. We be- 

 fore observed that a child, rash and unsteady, is 

 liable to a thousand accidents to which those of 

 maturer years are not exposed. Now, during all 

 the active years of life, the whole textures of the 

 frame, and especially of the thorax, both bone and 

 cartilage, possess elasticity, corresponding with the 

 hazards to which youth is subject : in short, the 

 child falls and suffers no injury ; when an old man, 

 striking his ribs upon the corner of the table, has 

 them fractured. But let us observe the effect of 

 elasticity in the act of respiration. 



The ribs do not move to accommodate them- 

 selves to the motions of the lungs, but by moving 

 draw the lungs after them, and cause their expan- 

 sion. The interstices of the ribs being filled up, 

 and a septum closing the thorax below, the en- 

 largement of the cavity permits the lungs to be 

 expanded by the weight of the atmosphere, the 

 air entering them through the windpipe. We at 

 once see the importance of the motions of the ribs, 

 for the expansion of the chest and the play of the 

 lungs. Our author has, however, omitted an es- 

 sential part of this interesting subject. He has 

 shown that the oblique position of the ribs is neces- 

 sary to inspiration, and that, by the rising of th^ 

 anterior part of the rib, the breast-bone is thrust 

 forwards and the cavity enlarged. But the rib has 

 a double motion. It has a motion on its own axis. 

 Suppose a line drawn through the two extremities 

 of a rib, which would represent the string of a 



