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LECTURE VIIL 



♦JJN: OBOA^'iZEB BODIES, A'NT) THE STRUCTURE OF PLA:NTS COMPABED WITH 

 THAT OF AJilMALS. 



From the unorganized world, which has formed the main subject of our 

 two last lectures, let us now rise a step higher in the scale of creation ; 

 and ascend from insentient matter to life, under the various modifications 

 it assumes, and the means by which it is upheld and transmitted. 



If I dig up a stone, and remove it from one place to another, the stone 

 will suffer no alteration by the change of place ; but if 1 dig up a plant 

 and remove it, the plant will instantly sicken, and perhaps die. What is 

 the cause of this difference ? Both have proceeded from a minute mole- 

 cule, a nucleus or a germ ; both have a tendency to preserve their deriva- 

 tive or family configuration, and both have been augmented and perfected 

 from one common soil. If I break the stone to pieces, every individual 

 fragment will be found possessed of the characteristic powers of the ag- 

 gregate mass ; it is only altered in its shape and magnitude ; but if I tear 

 off a branch from the plant, the branch will instantly wither, and lose the 

 specific properties of the parent stock. 



No external exemination, or reasoning a priory will explain this dif- 

 ference of effect. It is only by a minute attention to the relative histories, 

 interior structures, and modes of growth of the two substances, that we 

 are enabled to offer any thing like a satisfactory answer ; and by such ex- 

 amination we find that the stone has been produced fortuitously, has grown 

 by external accretion, and can only be destroyed by mechanical or chemi- 

 cal force ; while the plant has been produced by generation, has grown 

 by nutrition, and been destroyed by death : that it has been actuated by 

 an internal power, and possessed of parts mutually dependent and contri- 

 butory to each other's functions. 



In what this internal power consists we know not. Differently modified, 

 we meet with it in both plants and animals ; and wherever we find it we 

 denominate it the principle of life, and distinguish the individual substance 

 it actuates by the name of an organized being. And hence, all the various 

 bodies in nature arrange themselves under the two divisions of organized 

 and unorganized ; the former possessing an origin by generation, growth 

 by nutrition, and a termination by death ; and the latter a fortuitous origin, 

 external growth, and a termination by chemical or mechanical force. 



This distinction is clear, and it forms a boundary that does not seem to 

 be broken in upon by a single exception. In what, indeed, that wonderful 

 power of crystallization consists, or by what means it operates, which gives 

 a definite and geometrical figure to the nucleus or primary molecule of 

 every distinct species of crystal ; and which, with an accuracy that laughs 

 at all human precision, continues to impress the same figure upon the 

 growing crystal through every stage of its enlargement, thus naturally sepa- 

 rating one species from another, and enabling us to discriminate each by 

 its geometrical shape alone — we know not : but even here, where we meet 

 with an approach towards that formative effort, that internal action and 

 consent of parts which peculiarly characterize the living substance, there 

 is not the smallest trace of an organized arrangement ; while the origin is 

 clearly fortuitous, and the growth altogether external, from the mere ap- 

 position of surrounding matter. 



