ORGANS OF PERCEPTION. 909 
are likewise classified, according to the effects which they 
produce immediately upon the organ or the feelings in gene- 
ral; thus, we have pungent, nauseous, and fragrant smells. 
In many cases, however, we are compelled, in describing an 
odour, to compare it with that which is emitted by some well 
known substance. Thus, we say, sulphureous, vinous, 
alliaceous, musky, in reference to the smell of burning sul- 
phur, wine, garlic, or musk. 
This sense gives us information of the presence of odor- 
ous bodies, and, in many cases, of their position. It is, 
however, more extensively employed by animals, to distin- 
guish one body from another when contiguous, especially 
the different kinds of food. It informs us of many of the 
changes which take place in bodies by heat, light, or mois- 
ture, and thus serves the purpose of a chemical test. 
The sense of smell contributes greatly to our enjoyments, 
in our anticipations of food, and in the pleasure derived 
from perfumes. In man, the organs of smell are more 
developed in the savage than in the civilised state. In the 
latter, multitudes destroy the utility of this sense, as the 
mean of procuring information or pleasure. Other mam- 
miferous animals derive great pleasure from this sense, as 
is exhibited by the fondness of dogs to putrid substances, 
against which they delight to rub themselves, and of cats 
to particular plants. 
From the difficulty of characterising the different kinds 
of smells, and of recollecting the particular sensations which 
they excite, the information communicated by this sense, 
though varied, is seldom to be relied on with much confi- 
dence. The smell of one body may be disguised by the 
presence of another, even when small in quantity, as may 
be seen to a great extent in the deceptions of moder 
cookery. 
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