2 ANIMAL MECHANICS 



were the atmosphere lighter, the earth larger, or 

 its attraction more ; were he, in short, an inhab- 

 itant of another planet, there would be no cor- 

 respondence between the strength, gravity, and 

 muscular power of his body, and the elements 

 around him, and the balance in the chances of life 

 would be destroyed. 



Without such considerations the reader would 

 fall into the mistake that weakness and liability 

 to fracture imply imperfection in the frame of the 

 body, whereas a deeper contemplation of the sub- 

 ject will convince him of the incomparable perfec- 

 tion both of the plan and of the execution. The 

 body is intended to be subject to derangement 

 and accident, and to become, in the course of life, 

 more and more fragile, until, by some failure in 

 the framework or vital actions, life terminates. 



And this leads us to reflect on the best means 

 of informing ourselves of the intention or design 

 shown in this fabric. Can there be any better 

 mode of raising our admiration than by compar- 

 ing it with things of human invention ? It must 

 be allowed that we shall not find a perfect ana- 

 logy. If we compare it with the forms of archi- 

 tecture the house or the bridge are not built 

 for motion, but for solidity and firmness, on the 

 principle of gravitation. The ship rests in equi- 

 librium prepared for passive motion, and the con- 

 trivances of the ship-builders are for resisting 



