THE FUNCTIONS OF LIFE. ,33 



and for the regulation of their movements ; and 

 with these must be conjoined the skilful combina- 

 tions of the laboratory, by which the powers of a 

 most subtle chemistry are exercised in effecting all 

 the transmutations required by this complex system 

 of operations. As far as they involve mechanical 

 principles, these objects again arrange themselves 

 under the mechanical functions : and I shall ac- 

 cordingly include them under that head, when 

 giving an account of this branch of the subject. 



There is another, and a most important conse- 

 quence flowing from the peculiar chemical condition 

 of the materials of which animal structures arc 

 composed. The mode in which their elements are 

 combined is so complex as to require a long and 

 elaborate process to accomplish these peculiar com- 

 binations ; and neither the organs with which animals 

 are furnished, nor the powers with which those 

 organs are endowed, are adequate to the conversion 

 of the materials furnished by the inorganic world 

 into the substances required for the construction 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 or- 

 ganized beings. This important office is consigned 

 to the vegetable kingdom. Receiving the simple 

 food furnished by nature, which consists chiefly of 

 water, air, and carbonic acid, together with a small 

 proportion of other substances, plants convert these 

 aliments into products, which not only maintain 

 their own vitality, but serve the further purpose of 

 supporting the life of aniuials. Thus was the crea- 

 tion and continuance of the veoetable kin2:dom a 



VOL. I. D 



