OF SMELL. 179 



operation of respiration is principally performed through the nose, so 

 that the passage in them answers two purposes. 



Smelling is no more than the atmosphere or medium in which the 

 animal lives being impregnated with such matter as to make an impres- 

 sion on the organ ; therefore the air becomes the medium to the aerial, 

 and water to the aquatic. There is, however, a tribe of animals whose 

 construction is that of the most perfect, but which live entirely in 

 water, which search and catch their food in water, yet from their 

 general construction they must breathe air. [Whale and porpoise kind.] 



Here arises a difficulty: an animal to breathe air which it need not 

 smell, and not to breathe water which it should smell, if smelling were 

 necessary ; and to make a water-nose, was making the animal, in this 

 respect, like a fish, which would be deviating from the first principle ' : 

 therefore nature has made them entirely without the organ of smell 2 . 



Of Smelling. 



The third sense is that which is called smelling : it is where the 

 matter is too refined to be able to affect any of the other senses. To 

 affect this sense it must be in vapour, but it does not entirely depend 

 upon matter being in vapour ; it most likely depends upon a particular 

 modification of matter, or a particular modification of vapour which 

 naturally arises out of the volatile body. Whether the impression is 

 by impulse or by simple application is not so easily ascertained. 



This sense has a degree of refinement above taste ; and is, much in 

 the same proportion, less hurtful in its disagreeable sensations. It is 

 so connected and so subservient to taste, that I am inclined to think that 

 we can in some measure judge of the taste of a body from the smell, 

 and vice versa. 



Whether or not this imagination arises from custom, as we taste but 

 few things that we have not smelt before we taste, may be a question. 

 The moment that we smell food, we that instant have an idea of its 

 taste ; just as when we hear a bell ring we have an idea of the bell. 

 But what is most certain is, that smell and taste give us general ideas 

 of one another ; for, whatever is rich and fragrant to the smell, is also 

 such to the taste ; and I should suppose that whatever would give taste 

 in solution, would give smell in vapour, and perhaps such a smell as 

 would give a pretty just idea of the taste. 



1 [The ' homologicaP principle, or that of Unity of Plan.] 



2 [This was probably written before Hunter had dissected the piked and true 

 whales, in which he discovered the organ of smell. See Animal Economy , p. 377, 

 and Hunt. Prep. No. 154b.] 



n2 



