38 THE FUNCTIONS OF LIFE. 



comprehend these under one general head, con- 

 sidering them as composing the Mechanical 

 Functions of the animal economy. They will 

 engage a considerable share of our attention 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 affected, 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 con- 

 tinual 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 enquiry, and fur- 

 nishing abundant evidence of the wise and bene- 

 ficent operations of nature. These may be com 

 prehended under a separate class bearing the 

 general title of Nutritive Functions. 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, per- 

 ception, arid voluntary motion, which are the 



