32 THE FUNCTIONS OF LIFE. 



the Mechanical Functions of the animal economy. 

 They will engage a considerable share of our atten- 

 tion in this work, as affording the clearest and most 

 palpable proofs of contrivance and design. 



From the peculiar conditions of the living body, 

 not only with regard to the mechanical properties 

 of its various parts, and the powers by which their 

 movements are effected, but also with regard to the 

 chemical laws which regulate the combinations of 

 elements composing the substance of the body, 

 there is required, as will be more fully explained in 

 the sequel, a continual renovation of that substance. 

 For this purpose new materials are perpetually 

 wanted, and must be as regularly supplied. Hence 

 arises a new class of functions, comprising a great 

 extent of operations, opening a wide field of curious 

 and interesting inquiry, and furnishing abundant 

 evidence of the w ise and beneficent operations of 

 nature. These may be comprehended under a sepa- 

 rate class bearing the general title oi Nutritive Func- 

 tions. They are often, also, spoken of under the 

 designation of the Vital Functions, from their more 

 immediate relation to the continuance of vitality, 

 that is, of mere vegetative life, as distinguished from 

 the exercise of the higher faculties of sensation, 

 perception, and voluntary motion, which are the 

 ultimate ends of animal existence, and which are 

 emphatically termed the Animal Functions. 



The vital as well as the animal functions require 

 for the execution of their various objects certain 

 instruments of an appropriate mechanical con- 

 struction, adapted to those objects. To the contri- 

 vances of the mechanist must be added a refined 

 hydraulic apparatus for the conveyance of fluids, 



