36 ^ THE VITAL FUNCTIONS. 



pended. It is impossible to contemplate so 

 special an adjustment of opposite effects without 

 admiring this beautiful dispensation of Provi- 

 dence, extending over so vast a scale of being, 

 and demonstrating the unity of plan on which 

 the whole system of organized creation has been 

 devised. 



§ 5. Return of the Sap. 



The sap, which, during its ascent from the roots, 

 contains but a small proportion of nutritious par- 

 ticles, diluted with a large quantity of water, 

 after undergoing in the leaves, as in a chemical 

 laboratory, the double processes of exhalation 

 and aeration, has become much more highly 

 charged with nutriment ; and that nutriment has 

 been reduced to those particular forms and states 

 of composition which render it applicable to the 

 growth of the organs, and the other purposes of 

 vegetable life. This fluid, therefore, corresponds 

 to the blood of animals, which, like the elaborated 

 sap, may be regarded as fluid nutriment, per- 

 fectly assimilated to that particular kind of or- 

 ganization, with which it is to be afterwards in- 

 corporated. From the circumstance of its being 

 sent back from the leaves for distribution to the 

 several organs where its presence is required, it 

 has received the name of the returning sap, that 

 it miglit be distinguished from the crude fluid 



