INTRODUCTION. 49 



A rapid sketch of the intellectual functions of Animals 



The impression of external objects upon the indi- 

 vidual, the production of sensation and of ideas, 

 involve to our understanding an hitherto impene- 

 trable mystery. The hypothesis of materialism is 

 as little calculated as any other for the solution of 

 this problem, and is in fact the more rash and un- 

 satisfactory, inasmuch as philosophy is unable to 

 produce any direct proof of the real existence of 

 matter. But it is the business of the naturalist to 

 examine how far sensation may be modified by the 

 arrangement and composition of mere material parts, 

 to pursue the operations of intellect to their utmost 

 point of elevation in every living being, and to as- 

 certain whether the degrees of their perfection do or 

 do not depend upon the organization of the species, 

 are or are not affected by the momentary state of 

 the material body. 



Perception, generally speaking, depends upon an 

 uninterrupted communication of the nerves from the 

 external organs of sense to the central masses of the 

 medullary system. Hence it appears that the mo- 

 difications experienced by these central masses are 

 the real immediate objects of perception to the mind, 

 and accordingly we find that perception may also 

 be produced without the affection of the external 

 organs, and originate therefore in the nervous chain 

 of communication, or in the central masses them- 



Vol. I. E 



