LECTUllE VI. QQ5 



that which has been deduced in the intro- 

 ductory lectures ; that vibratory actions 

 occurring in the nerves, in consequence of 

 impressions made on them, are transmitted 

 to the brain, and variously affect that which 

 is perceptive. It is evident to reason that 

 our perceptions have no rational corre- 

 spondence to the causes producing them ; 

 and nature may have allotted to animals 

 various kinds and degrees of perception 

 adapted to their wants, and the situation 

 they occupy in the scale of existence. 

 No one can guess what kind of vision 

 belongs to the fly. There are probably 

 25,000 hexagonal lenses or menisci on its 

 surface, or the same number of distinct 

 visual organs, as some comparative anato- 

 mists would have us to believe. Some 

 animals may have great susceptibility to 

 light, odour, and sound, and yet may not 

 possess great general susceptibility. We 

 find indeed, in may instances, organization 

 adapted to function, and yet it is highly 

 improbable that we shall ever be able to 

 explain function by means of our know- 

 ledge of organization. .; 



