PROCESSES OF NUTKITION. 11 



measures are taken for tlie removal of these useless 

 or noxious materials, by transferring them to the 

 general mass of circulating blood, so as either to be 

 again usefully employed, or altogether discarded by 

 excretion from the system. This object is accom- 

 plished by a peculiar set of vessels; and the 

 function they perform is termed Absorption. 



Lastly, the conversion of the fluid nutriment into 

 the solids of the body, and its immediate applica- 

 tion 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 harmonious system of opera- 

 tions. 



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 increase in complexity, corres- 

 ponding, in some measure, to the greater refine- 

 ment 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 surrounding them ; mate- 

 rials which consist almost wholly of water, with a 



