12 ELEMENTARY STRUCTURE OF ORGANIZED BODIES. 



besides, the incessant movement of growth, decomposition, 

 and renovation. 



33. Their mode of formation is also entirely different. 

 They are, in the first place, derived from sources unlike 

 themselves ; and if a mineral is enlarged, it is simply by 

 the outward addition of particles constituted like itself. 

 Organized bodies are not formed in this manner. They 

 always, and necessarily, are derived from beings similar 

 to themselves ; and once formed, they increase always 

 from within outward, by the interposition of new particles, 

 which go to complete the individual. 



34. Finally, organized bodies are limited in their dura- 

 tion. Animals and plants are constantly losing some of 

 their parts by decomposition during life, which at length 

 cease to be supplied, and they die, after having lived for a 

 longer or shorter period. Inorganic bodies, on the con- 

 trary, contain within themselves no principle of destruction ; 

 and unless subjected to some foreign influence, a crystal or 

 a rock would never change. The limestone and granite of 

 our mountains remain just as they were formed in ancient 

 geological epochs ; while numberless generations of plants 

 and animals have lived and perished upon their surface. 



SECTION II. 



ELEMENTARY STRUCTURE OF ORGANIZED BODIES. 



35. The exercise of the functions of life, which is the es- 

 sential characteristic of organized bodies (32), requires a 

 degree of flexibility of the organs. This is secured by 

 means of a certain quantity of watery fluid, which pene- 



