We now proceed to treat of the senses

for there are diversities
in animals with regard to the senses, seeing that some animals have
the use of all the senses, and others the use of a limited number of
them. The total number of the senses (for we have no experience of any
special sense not here included), is five: sight, hearing, smell,
taste, and touch.

Man, then, and all vivipara that have feet, and, further, all
red-blooded ovipara, appear to have the use of all the five senses,
except where some isolated species has been subjected to mutilation,
as in the case of the mole. For this animal is deprived of sight; it
has no eyes visible, but if the skin-a thick one, by the way-be
stripped off the head, about the place in the exterior where eyes
usually are, the eyes are found inside in a stunted condition,
furnished with all the parts found in ordinary eyes; that is to say,
we find there the black rim, and the fatty part surrounding it; but
all these parts are smaller than the same parts in ordinary visible
eyes. There is no external sign of the existence of these organs in
the mole, owing to the thickness of the skin drawn over them, so
that it would seem that the natural course of development were
congenitally arrested; (for extending from the brain at its junction
with the marrow are two strong sinewy ducts running past the sockets
of the eyes, and terminating at the upper eye-teeth). All the other
animals of the kinds above mentioned have a perception of colour and
of sound, and the senses of smell and taste; the fifth sense, that,
namely, of touch, is common to all animals whatsoever.