12 THE VITAL FUNCTIONS. 



small proportion of carbonic acid, and a few saline 

 ingredients, of which that water is the vehicle. But 

 these, after having been converted by the powers 

 of vegetable assimilation, into the substance of the 

 plant, acquire the characteristic properties of orga- 

 nized products, though tliey are still the simplest 

 of that class. In this state, and when the fabric 

 they had composed is destroyed, and they are scat- 

 tered over the soil, they are fitted to become more 

 highly nutritive to other plants, which absorb them, 

 and adapt them with more facility to the purposes 

 of their own systems. Here they receive a still 

 higher degree of elaboration ; and thus the same 

 materials may pass through several successive 

 series of modifications, till they become the food 

 of animals, and are then made to undergo still 

 further changes. New elements, and in particular 

 nitrogen, is added to the oxygen, hydrogen and 

 carbon, which are the chief constituents of vege- 

 table substances :* and new properties are acquired 

 from the varied combinations into which their 

 elements are made to enter by the more energetic 

 powers of assimilation appertaining to the animal 

 system. The products which result are still more 

 removed from their original state of inorganic 

 matter : and in this condition they serve as the 

 appropriate food of carnivorous animals, which 



* Nitrogen, however, is generally present in vegetables; but in a 

 much smaller proportion than in animal structures. It is an essen- 

 tial ingredient in the food of plants, and is contained in their juices 

 and secretions ; although it never enters into the chemical compo- 

 sition of their membranes. The farinaceous seeds, more especially, 

 contain a considerable quantity of this element. It abounds in the 

 cambium, and generally in every part which is beginning to be deve- 

 loped. Payen: Comptes Rendus, 1838, p. 132. 



