On The Generation Of Animals
do not see well at a distance, whereas those which have their eyes
lying deep in the head can see things at a distance because the
movement is not dispersed in space but comes straight to the eye.
For it makes no difference whether we say, as some do, that seeing
is caused by the sight going forth from the eye- on that view, if
there is nothing projecting over the eyes, the sight must be scattered
and so less of it will fall on the objects of vision and things at a
distance will not be seen so well- or whether we say that seeing is
due to the movement coming from the objects; for the sight also must
see, in a manner resembling the movement. Things at a distance,
then, would be seen best if there were, so to say, a continuous tube
straight from the sight to its object, for the movement from the
object would not then be dissipated; but, if that is impossible, still
the further the tube extends the more accurately must distant
objects be seen.
Let these, then, be given as the causes of the difference in eyes.
It is the same also with hearing and smell; to hear and smell
accurately mean in one sense to perceive as precisely as possible
all the distinctions of the objects of perception, in another sense to
hear and smell far off. As with sight, so here the sense-organ is
the cause of judging well the distinctions, if both that organ
itself and the membrane round it be pure. For the passages of all
the sense-organs, as has been said in the treatise on sensation, run
to the heart, or to its analogue in creatures that have no heart.
The passage of the hearing, then, since this sense-organ is of air,
ends at the place where the innate spiritus causes in some animals the
pulsation of the heart and in others respiration; wherefore also it is
that we are able to understand what is said and repeat what we have
heard, for as was the movement which entered through the
sense-organ, such again is the movement which is caused by means of
the voice, being as it were of one and the same stamp, so that a man
can say what he has heard. And we hear less well during a yawn or
expiration than during inspiration, because the starting-point of
the sense-organ of hearing is set upon the part concerned with
breathing and is shaken and moved as the organ moves the breath, for
while setting the breath in motion it is moved itself. The same
thing happens in wet weather or a damp atmosphere.... And the ears
seemed to be filled with air because their starting-point is near
the region of breathing.
Accuracy then in judging the differences of sounds and smells
depends on the purity of the sense-organ and of the membrane lying
upon its surface, for then all the movements become clear in such
cases, as in the case of sight. Perception and non-perception at a
distance also depend on the same things with hearing and smell as with
sight. For those animals can perceive at a distance which have
channels, so to say, running through the parts concerned and
projecting far in front of the sense-organs. Therefore all animals
whose nostrils are long, as the Laconian hounds, are keen-scented, for
the sense-organ being above them, the movements from a distance are
not dissipated but go straight to the mark, just as the movements
which cause sight do with those who shadow the eyes with the hand.
Similar is the case of animals whose ears are long and project far
like the eaves of a house, as in some quadrupeds, with the internal
spiral passage long; these also catch the movement from afar and
pass it on to the sense-organ.
In respect of sense-perception at a distance, man is, one may say,
the worst of all animals in proportion to his size, but in respect