ANATOMY OF PLANTS. 



219 



G. Wahlenberg, de sedibus materiarum immediatarum in Plantis. 



H. Steffens, Beytrage zur iiinern Naturgeschichte der Erde. 

 Rauch, Regeneration de la Nature vegetale. 



I. General Remarks. 

 342. 



The composition of organic bodies is distinguished by 

 more than one circumstance from the union of the elementa- 

 ry matters in unorganised substances ; and, on these accounts, 

 the examination of them becomes as difficult as it is instruc- 

 tive. 



The first peculiarity in the composition of organic bodies, is 

 their great liability to change, and their constant tendency to 

 decomposition ; while, at the same time, as long as life remains, 

 this tendency never perfectly succeeds. As soon, however, as 

 organic juices are withdrawn from the dominion of life, they 

 undergo a change of their elements, and a decomposition of 

 their constitution, which are attended with remarkable conse- 

 quences. 



Since we can thus only examine the composition of organic 

 bodies, after they have ceased to live, we cannot be always 

 certain that the results of our chemical examination really ex- 

 plain the way and manner in which the juices are mixed in 

 living substances. Indeed, a highly etherial matter, which, 

 as it were, gave life to the sap, seems often to make its escape, 

 at the moment when the fluid or organic matter loses its in- 

 dividual character, and is subjected to examination. We are 

 thus often reminded of the spiritus rector of the blood, which 

 our predecessors admitted, and which we have no reason to 

 treat with too much contempt. 



The change which organic matters undergo when they 

 cease to live, is of so peculiar a kind, that it cannot take 

 place in inorganic bodies, unless they are mixed with or- 

 ganic matter. It is an internal change, which, in the juices 

 of plants and in other vegetable matters, commonly begins 

 with the evolution of carbonic acid, and ends with the plenti- 

 ful production of acetic acid. It is called Fermentation. In 



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