On Sense And The Sensible   

Consistently with what has been said above, not one of the lower

animals shows repugnance to the odour of things which are

essentially ill-smelling, unless one of the latter is positively

pernicious. They are destroyed, however, by these things, just as

human beings are; i.e. as human beings get headaches from, and are

often asphyxiated by, the fumes of charcoal, so the lower animals

perish from the strong fumes of brimstone and bituminous substances;

and it is owing to experience of such effects that they shun these.

For the disagreeable odour in itself they care nothing whatever

(though the odours of many plants are essentially disagreeable),

unless, indeed, it has some effect upon the taste of their food.

The senses making up an odd number, and an odd number having

always a middle unit, the sense of smell occupies in itself as it were

a middle position between the tactual senses, i.e. Touch and Taste,

and those which perceive through a medium, i.e. Sight and Hearing.

Hence the object of smell, too, is an affection of nutrient substances

(which fall within the class of Tangibles), and is also an affection

of the audible and the visible; whence it is that creatures have the

sense of smell both in air and water. Accordingly, the object of smell

is something common to both of these provinces, i.e. it appertains

both to the tangible on the one hand, and on the other to the

audible and translucent. Hence the propriety of the figure by which it

has been described by us as an immersion or washing of dryness in

the Moist and Fluid. Such then must be our account of the sense in

which one is or is not entitled to speak of the odorous as having

species.

The theory held by certain of the Pythagoreans, that some animals

are nourished by odours alone, is unsound. For, in the first place, we

see that food must be composite, since the bodies nourished by it

are not simple. This explains why waste matter is secreted from

food, either within the organisms, or, as in plants, outside them. But

since even water by itself alone, that is, when unmixed, will not