TRANSFORMATIONS OF ORGANIC SUBSTANCES. 51 



produced. The functions of the leaves of most 

 plants cease upon the ripening of their fruit, because 

 the products of their action are no longer needed. 

 They now yield to the chemical influence of the 

 oxygen of the ah*, generally suffer therefrom a 

 change in colour, and fall off. 



A peculiar " transformation" of the matters con- 

 tained in all plants takes place in the period be- 

 tween blossoming and the ripening of the fruit ; 

 new compounds are produced, which furnish con- 

 stituents of the blossoms, fruit, and seed. An 

 organic chemical "transformation" is the separation 

 of the elements of one or several combinations, 

 and their reunion into two or several others, 

 which contain the same number of elements, either 

 grouped in another manner, or in different propor- 

 tions. Of two compounds formed in consequence 

 of such a change, one remains as a component part 

 of the blossom or fruit, while the other is separated 

 by the roots in the form of excrementitious matter. 

 No process of nutrition can be conceived to subsist 

 in animals or vegetables, without a separation of 

 effete matters. We know, indeed, that an organised 

 body cannot generate substances,- but can only 

 change the mode of their combination, and that 

 its sustenance and reproduction depend upon the 

 chemical transformation of the matters which are 

 employed as its nutriment, and which contain its 

 own constituent elements. 



Whatever we regard as the cause of these trans- 



E 2 



