ORGANS OF PF/UCEl'TION. 205 



Thus, we can in general distinguish between the sound of 

 wood or metal, water or air, and hollow or solid bodies. 



In judging, however, of any one of these qualities or 

 conditions of bodies, we call to our assistance all the infor- 

 mation which is communicated by the different characters 

 of the sonorous vibrations, so that the conclusion at which 

 we arrive, is frequently the result of a very complex, though 

 rapidly executed mental operation. 



To animals in general, the sense of hearing gives warn- 

 ing of die approach or retreat of their foes. In some cases, 

 it is likewise the medium of communication between the 

 individuals of the same species, in the expressions of their 

 feelings of joy or grief, love or hatred. The human ear,, 

 judges of all the qualities of sounds. Some of the qua- 

 drupeds and birds can, however, perceive sounds which 

 are inaudible to us, and perhaps can recognise more readily 

 than we are able to do, some of the modifications of a par- 

 ticular quality. But our knowledge of the peculiar func- 

 tions of the different parts of the ear, is still too limited to 

 enable us to speculate, with any prospect of success, even 

 were our information concerning the habits and feelings of 

 the lower animals more extensive and precise. 



In the systematical arrangement of animals, the charac- 

 ters furnished by the organs of hearing, are scarcely ever 

 employed, unless in the exhibition of generic or specific dis- 

 tinctions. Even for such purposes, the attention is exclu- 

 sively directed to the external ear, and to the form and po- 

 sition of the entrance ; the internal ear being concealed from 

 view, difficult to dissect, and furnishing characters which 

 can scarcely be expressed by words. 



V. SENSE OF SMELL. 



In those animals which possess organs of Smell, suffi- 

 ciently developed to be obvious to the eye, the Nose, or en- 



