42 THE FUNCTIONS OF LIFE. 



field of curious and interesting inquiry, and furnishing abun- 

 dant evidence of the wise and beneficent operations of na- 

 ture. These may be comprehended under a separate class 

 bearing the general title oi JVutritivc Functions. They are 

 often also, spoken of under the designation of the Vital 

 Ftinctions, from their more immediate relation to the con- 

 tinuance of vitality; that is, of mere vegetative life, as dis- 

 tinguished from the exercise of the hidier faculties of sen- 

 sation, perception, and voluntary motion, which are the ul- 

 timate ends of the animal existence, and which are empha- 

 tically 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 construction, adapted to those objects. 

 To the contrivances of the mechanist must be added a refined 

 hydraulic apparatus for the conve3^ance of fluids, and for the 

 resrulation of their movements; and with these must be con- 

 joined the skilful combinations of the laborator}^, by which 

 the powers of the most subtle chemistry are exercised in ef- 

 fecting all the transmutations required by this elaborate sys- 

 tem of operations. As far as they involve mechanical prin- 

 ciples, these objects again arrange themselves under the me- 

 chanical functions: and I shall accordingly include them 

 under that head, when giving an account of this branch of 

 the subject. 



There is another, and a most important consequence that 

 flows from the peculiar chemical conditions of the materials of 

 which animal structures are composed. The mode in which 

 their elements are combined is so complex as to require a 

 long and elaborate process to accomplish that purpose; and 

 neither tlie organs with which animals are furnished, nor 

 the powers with which those organs are endowed, are ade- 

 quate to tlie conversion of the materials furnished by the 

 inorganic world into the substances required for the con- 

 struction of their bodies, and the maintenance of their 

 powers. These inorganic elements must have passed 

 through intermediate stages of combination, and must 

 have been previously elaborated by other organized be- 



