4 THE VITAL FUNCTIONS. 



all materials, — the diamond. Such a machine, once 

 finished, being exempt from almost every natural 

 cause of decay, might remain for an indefinite 

 period in the same state. Far different are the 

 objects which must be had in view in the formation 

 of organized structures. In order that these may 

 be qualified for exercising the functions of life, they 

 must be capable of continual alterations, displace- 

 ments, and adjustments, varying perpetually, both 

 in kind and in degree, according to the progressive 

 stages of their internal developement, and to the 

 different circumstances which may arise in their 

 external condition. The materials which nature 

 has employed in their construction are, therefore, 

 neither the elementary bodies nor even their 

 simpler and more permanent combinations, but 

 such of their compounds as are of a more plastic 

 quality, and which allow of a variable proportion 

 of ingredients, and of considerable diversity in the 

 modes of their combination. So great is the 

 complexity of these arrangements, that although 

 chemistry is fully competent to the analysis of or- 

 ganized substances into their ultimate elements, no 

 human art is adequate to eff^ect their reunion in 

 the same state as that in which they had existed 

 in those substances ; for it was by the refined ope- 

 rations of vitality, the only power which could 

 produce such an adjustment, that they have been 

 brought into that condition. 



We may take as an example one of the simplest 

 of organic products, namely Sugar; a substance 

 which has been analysed with the greatest accuracy 

 by modern chemists : yet to reproduce this sugar, 

 by the artificial combination of its simple elements. 



