40 THE FUNCTIONS OF LIFE. 



quired for the construction of their bodies, and 

 the maintenance of their powers. These inor- 

 ganic elements must have passed through inter- 

 mediate stages of combination, and must have 

 been previously elaborated by other organized 

 beings. This important office is consigned to the 

 vegetable kingdom. Receiving the simple food 

 furnished by nature, which consists chiefly 

 of water, air, and carbonic acid, together with a 

 small proportion of other substances, plants con- 

 vert these aliments into products, which not only 

 maintain their own vitality, but serve the further 

 purpose of supporting the life of animals. Thus 

 was the creation and continuance of the vege- 

 table kingdom a necessary step towards the 

 existence of the animal world ; as well as a link 

 in the great chain of being, formed and sustained 

 by Almighty power. The Physiology of Vege- 

 tables presents many topics of great interest with 

 relation to final causes, and will in this Treatise 

 be reviewed with special reference to this im- 

 portant object. 



Nutrition, both in the vegetable and animal 

 systems, comprises a very extended series of 

 operations. In the former it includes the ab- 

 sorption of the crude materials from the sur- 

 rounding elements, — their transmission to organs 

 where they are aerated, that is, subjected to the 

 chemical action of the air; — their circulation in 

 the different parts of the plant, — their further 



