534 THE SENSORIAL FUNCTIONS. 



a single ball, of about the size of a pea, between 

 two fingers which are crossed ; for there is then 

 a distinct perception of the presence of two 

 balls instead of one. 



But limited as our senses are in their range 

 of perception, and liable to occasional error, we 

 cannot but perceive, that, both in ourselves, and 

 also in every class of animals, they have been 

 studiously adjusted, not only to the properties 

 and the constitution of the material world, but 

 also to the respective wants and necessities of 

 each species, in the situations and circumstances 

 where it has been placed by the gracious and 

 beneficent Author of its being. 



If the sensorial functions had been limited to 

 mere sensation and j^erception, conjoined with 

 the capacity of passive enjoyment and of suf- 

 fering, the purposes of animal existence would 

 have been but imperfectly accomplished ; for in 

 order that the sentient being may secure the 

 possession of those objects which are agreeable 

 and salutary, and avoid or reject those which 

 are painful or injurious, it is necessary that he 

 possess the power of spontaneous action. Hence 

 the faculty of Voluntary 3Iotion is superadded 

 to the other sensorial functions. The muscles 

 which move the limbs, the trunk, the head, and 

 organs of sense, — all those parts, in a word, 

 which establish relations with the external 

 world, are, through the intermedium of a sepa- 

 rate set of nervous filaments, totally distinct from 



