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. A bird at any rate has nothing
which can properly be called a nose. For its so-called beak is a
substitute for jaws. The reason for this is to be found in the natural
conformation of birds. For they are winged bipeds; and this makes it
necessary that their heads and neck shall be of light weight; just
as it makes it necessary that their breast shall be narrow. The beak
therefore with which they are provided is formed of a bone-like
substance, in order that it may serve as a weapon as well as for
nutritive purposes, but is made of narrow dimensions to suit the small
size of the head. In this beak are placed the olfactory passages.
But there are no nostrils; for such could not possibly be placed
there.
As for those animals that have no respiration, it has already been
explained why it is that they are without nostrils, and perceive
odours either through gills, or through a blowhole, or, if they are
insects, by the hypozoma; and how the power of smelling depends,
like their motion, upon the innate spirit of their bodies, which in
all of them is implanted by nature and not introduced from without.
Under the nostrils are the lips, in such sanguineous animals, that
is, as have teeth. For in birds, as already has been said, the
purposes of nutrition and defence are fulfilled by a bonelike beak,
which forms a compound substitute for teeth and lips. For supposing
that one were to cut off a man's lips, unite his upper teeth together,
and similarly his under ones, and then were to lengthen out the two
separate pieces thus formed, narrowing them on either side and
making them project forwards, supposing, I say, this to be done, we
should at once have a bird-like beak
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