560 THE SENSORIAL FUNCTIONS. 



medulla oblongata, are those principally con- 

 cerned in sensation ; and that the cerebellum is 

 the chief sensorial agent in voluntary motion. 



§ 4. Comparative Physiology of Perception. 



Of the perceptions of the lower animals, and of 

 the laws which they obey, our knowledge must, of 

 necessity, be extremely imperfect, since it must 

 be derived from a comparison with the results of 

 our own sensitive powers, which may differ very 

 essentially from those of the subjects of our 

 observation. The same kind of organ which, in 

 ourselves, conveys certain definite feelings, may, 

 when modified in other animals, be the source 

 of very different kinds of sensations and per- 

 ceptions, of which our minds have not the power 

 to form any adequate conception. Many of the 

 qualities of surrounding bodies, which escape 

 our more obtuse senses, may be distinctly per- 

 ceived, in all their gradations, by particular 

 tribes of animals, furnished with more delicate 

 organs. Many quadrupeds and birds possess 

 powers of vision incomparably more extensive 

 than our own ; in acuteness of hearing, we are 

 excelled by a great number of animals ; and in 

 delicacy of taste and smell, there are few quad- 

 rupeds that do not far surpass us. The organ 



