INTRODUCTION. XV 



and exclusive features, whicli separate the or- 

 ganic world into two distinct spheres of exist- 

 ence. 



Nor should it be forgotten that those outward 

 manifestations, which result from the presence of 

 a locomotive apparatus and a material recipient 

 of sentient impressions, though not exhibited by- 

 all animals, are by no means, on this account, less 

 worthy of being considered as the most striking 

 characteristics of animal life, of which, indeed, 

 they are the peculiar ^products. In this point of 

 view they were regarded by Aristotle"^, who tias 

 beautifully contrasted such active operations with 

 the profound slumber in which the life of vege- 

 tables is plunged. 



But of all the artificial distinctions which serve 

 to separate plants from animals, none will be 

 found more remarkable than those which are 

 based, either on the nature of their respective 

 nutrient materials, or the mode in which such 

 materials are appropriated. The food of plants ^^A' 

 consists, for the most part, of the inorganic com- 

 pounds, water, carbonic acid, and ammonia, to- 

 gether with minute quantities of a few mineral 

 substances, usually to be found in most fertile 

 soils. The Fungi, and other parasitic vegetables, 

 are supposed to offer only apparent exceptions to 

 the truth of this statement. Animals, on the 

 other hand, require for their subsistence organised 

 matter, which has been previously stored up in 

 the bodies of other living beings. Again, plants 



