70 THE VITAL FUNCTIONS. 



Stages of its conversion into blood ; a fluid which, 

 like the returning sap of plants, consists of nutri- 

 ment in its completely assimilated state. It will 

 be necessary, therefore, to enter into a more par- 

 ticular examination of the objects of these diflfe- 

 rent processes. 



In the more perfect structures belonging to 

 the higher orders of animals, contrivances must 

 be adopted, and organs provided for seizing the 

 appropriate food, and conveying it to the mouth. 

 A mechanical apparatus must there be placed 

 for effecting that minute subdivision, which is 

 necessary to prepare it for the action of the che- 

 mical agents to which it is afterwards to be sub- 

 jected. From the mouth, after it has been 

 sufficiently masticated, and softened by fluid 

 secretions prepared by neighbouring glands, the 

 food must be conveyed into an interior cavity, 

 called the Stomach, where, as in a chemical 

 laboratory, it is made to undergo the particular 

 change which results from the operation termed 

 Digestion. The digested food must thence be 

 conducted into other chambers, composing the 

 intestinal tube, where it is converted into Chyle, 

 which is a milky fluid, consisting wholly of 

 nutritious matter. Vessels are then provided, 

 which, like the roots of plants, drink up this 

 prepared fluid, and convey it to other cavities, 

 capable of imparting to it a powerful impulsive 

 force, and of distributing it through appropriate 



