THE FUNCTIONS OF LIFE. 43 



ings. This important office is consigned to the vege- 

 table kingdom. Receiving the simple food furnished by 

 nature, which consists chiefly of water, air, and carbonic 

 acid, together with a small proportion of other subslan es, 

 plants convert these aliments into products, which not only 

 maintain their own vitality, but serve the farther purpose 

 of supporting the life of animals. Thus was the creation 

 and continuance of the vegetable 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 Al- 

 mighty power. The physiology of Vegetables presents 

 many topics of great interest with relation to final causes, 

 and will in this Treatise be reviewed with special reference 

 to this important object. 



Nutrition, both in the vegetable and animal sj'stems, com- 

 prises a very extended scries of operations. In the former 

 it includes the absorption of the crude materials from the 

 surrounding 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 farther elaboration in particular vessels and recep- 

 tacles—their deposition of solid materials — and their con- 

 version into peculiar products, as well as into the substances 

 which compose the several organs; — and, finally, the growth 

 and development of the whole plant. Still more various 

 and complicated are the corresponding functions in animals. 

 Their objects may be arranged under the following general 

 heads; each, again, admitting of farther subdivision. The 

 first end to be accomplished is to animalize the food; that 

 is, to convert it into a matter having the chemical properties 

 of the animal substances with which it is to be afterwards 

 incorporated. The entire change thus effected is termed 

 Jissimilation^ of which Digestion forms a principal part. 

 The second object is to collect and distribute this prepared 

 nutriment, which is the blood, to the different organs, or 

 wherever it may be wanted. The necessary motions for 

 these purposes are given to the blood by the organs of Cir- 

 culation, consisting of the Heart, which impels it /hrough 



