i@2 THE PHILOSOPHY 



olfadory nerves are defended from the adion of the air, and from 

 the painful ftimuli of acrid odours. 



The odours perceived by fmelling are extremely various. Some 

 of them convey to us the moft delightful and refrefhing fenfations, 

 and others are painful, noxious, and difgufting. All bodies in 

 Nature, whether folld or fluid, whether animated or inanimated, 

 continually fend forth to the air certain effluvia or emanations from 

 their refpedive fubft;ances. Thefe effluvia float in the atmofphere, 

 and adl upon the olfadory nerves of different animals, and fome- 

 times of different individuals of the fame fpecies, in fuch a manner 

 as to produce very different fenfations. What is pleafant to the 

 nofl:rils of one animal is highly offenfive to thofe of another. Brute 

 animals feled their food chiefly by employing the fenfe of fmelling, 

 and it feldom deceives them. They eafily diftinguifh noxious from 

 falutary food ; and they carefully avoid the one, and ufe the other 

 for nourifhment. The fame thing happens with regard to the drink 

 of animals. A cow, when it can be obtained, always repairs to the 

 cleared and frefhefl ftreams ; but a horfe, from fome inftindivq im- 

 pulfe, uniformly raifes the mud with his feet, and renders the water 

 impure, before he drinks. 



In the feledion of food, men are greatly afTifted, even in the mofl 

 luxurious ftate of fociety, by the fenfe of fmelling. By fmelling 

 we often rejed food as noxious, and will not rifk the other left of 

 »afling. Viduals which have a putrid fmell, as equally offenfive to 

 our noflrils as hurtful to our conflitutions, we avoid with abhor- 

 lence; but we are allured to eat fubfl:ances which have a grateful 

 and favoury odour. The more frequent and more acute difcern- 

 ment of brutes in the exercife of this fenfe, is entirely owing to their 

 freedom, and to their ufing natural produdions alone. But men in 

 fociety, by the arts of cookery, by the unnatural afTemblage of twen- 

 ty 



