208 NATURAL THEOLOGY. 



axle-tree between two wheels ; or they are like a 

 pillar under a great weight ; or those bones are 

 acting as levers. We see, therefore, why, to with- 

 stand these different shocks, a bone should con- 

 sist, as we have stated, of three parts, the earth of 

 bone (sub-phosphate of lime) to give it firmness ; 

 fibres to give it toughness ; and cartilage to give 

 it elasticity. 



We may pursue this subject a little further still, 

 taking the text of our author — " The proportion- 

 ing of one thing to another. ^^ Chap. xvii. sec. v. 



The great functions by which animals live and 

 breathe and are nourished, are the same through 

 the whole chain, from the simplest polypus or 

 mass of jelly that floats in the sea, to the largest 

 and most complex of all terrestrial creatures. The 

 appetite for food, the powers of assimilation, cir- 

 culation, aeration, secretion, are the same func- 

 tions in all living creatures, only modified by their 

 size or condition. When we consider the aston- 

 ishing variety in the shapes of animated beings, 

 we are apt to forget the necessity of apportioning 

 their size and strength, not only to the vegetable 

 productions and to the materials found on the 

 surface of the earth, but to the magnitude of the 

 globe — to the " great motions that are passing in 

 the heavens." On that plan of living structure 

 which pervades all the varieties of animals in 

 which bones afford resistance and muscles activity, 

 there must be a limit to stature. The resisting 

 parts of the smaller animals, which have an ex 



