16 LITE IN NATURE. 



present powers of analysis. It is not unlikely that 

 the framework (if we may call it so) of the muscle 

 remains comparatively unchanged, and that fresh 

 portions of material are continually brought to un- 

 dergo decomposition. In this way, we might perhaps 

 better understand the decadence of the body with 

 advancing age ; it may be literally a wearing out. 



And, secondly, the dependence of the active 

 powers of the body upon the decomposition of its 

 substance was rendered difficult to recognize, by the 

 order in which the facts are presented to us. Let us 

 conceive that, instead of having invented steam- 

 engines, men had met with them in nature as 

 objects for their investigation. What would have 

 been the most obvious character of these bodies ? 

 Clearly their power of acting of moving. This 

 would have become familiar as a " property " or 

 endowment of steam-engines, long before the part 

 played by the steam had been recognized ; for that 

 would have required careful investigation, and a 

 knowledge of some recondite laws, mechanical, 

 chemical, pneumatic. Might it not, then, have 

 happened that motion should have been taken as a 



