* i 



114 



the indications of these functions are much less 

 manifest in the former than in the latter, which 

 is not the case with those already spoken of ; so 

 that we may still adopt this as a convenient, if not 

 a precise line of demarcation between the two. 

 I shall accordingly devote the present chapter to 

 a short description of the several organs, by 

 which, in different animals, the functions of 

 smell, sight, hearing, taste, touch and loco-mo- 

 tion, are respectively performed. 



In quite the lowest orders of animals the or- 

 gan, if any, specifically appropriated to smell is 

 in general very obscure, although some of them 

 in which this is the case the cuttle for example 

 display this function very remarkably. It is, 

 perhaps, in most of them, merely a modification 

 of touch, and performed equally by every part of 

 the surface of the body. In the snail the seat of 

 smell has been commonly considered to be their 

 short feelers ; but apparently without any good 

 reason. 



Insects in general smell very acutely ; and in 

 them the seat of this function has been at different 

 times supposed to be their stigmata, or air-holes, 

 their palpi, or commonly reputed organs of taste, 

 and their antennae, or organs of touch in gene- 

 ral. In the cray-fish, which is one of the few in- 

 sects that have a sufficiently obvious olfactory 

 nerve, it is manifestly their smaller antennae, at 

 the root of which the nasal cavities are situated. 

 In this animal, however, as well as in all aquatic 

 animals, smell is rather a modification of taste 



