POWERS OF ASSIMILATION. 13 



Lastly, the conversion of the fluid nutriment 

 into the solids of the body, and its immediate 

 application to the purposes of the developement 

 of the organs, of their preservation in the state of 

 health and activity, and of the repair of such 

 injuries as they may chance to sustain, as far as 

 the powers of the system are adequate to such 

 reparation, are the objects of a seventh set of 

 functions, more especially comprised under the 

 title of Nutrition, which closes this long series of 

 chemical changes, and this intricate but har- 

 monious system of operations. 



Although the order in which the constituent 

 elements of organized products are arranged, and 

 the mode in which they are combined, are 

 entirely unknown to us, we can nevertheless 

 perceive that in following them successively 

 from the simplest vegetables to the higher orders 

 of the animal kingdom, they acquire continually 

 increasing degrees of complexity, corresponding, 

 in some measure, to the greater refinement and 

 complication of the structures by which they have 

 been elaborated, and of the bodies to which they 

 are ultimately assimilated. Thus plants derive 

 their nourishment from the crude and simple 

 materials which they absorb from the earth, the 

 waters, and the air that surround them ; mate- 

 rials which consist almost wholly of water, with 

 a small proportion of carbonic acid, and a few 

 saline ingredients, of which that water is the 



