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THE ANIMAL SYSTEM. 119
perception may take place in the retina itself; for the
nerve may as well convey a perception as the impres
sion of which that perception is made.
Vibrations of the atmosphere, striking upon the drum
of the ear, produce impressions upon the complicated
apparatus of hearing, of all appreciable varieties of sound.
The powers of these instruments are truly wonderful.
The eye seems more simple than the ear, and we come
nearer to understanding its beautiful mechanism; but
the result is, in both cases, a mystery.
The senses of smell and taste seem to be very sim
ple modifications of the great sense of touch. Atoms
of matter, delicate and infinitesimal, come in contact
with the olfactory nerve, and we have the delights of
smell. Savors, mingling with the moistening saliva of
the mouth,
come in contact with the nerves in the
papilla? of the tongue, and we experience the pleasures
of taste. These are two delightful sentinels set to
guard the avenue to the stomach ; and to see that no
impure thing finds entrance to the sanctuaries of organic
life, for as the organic nature supplies strength to the
animal, it is the duty of the animal to watch over and
protect the organic.
The sense of feeling pervades the whole body, and
even the organs of the other senses. We can not
only taste with the tongue, but we receive sensations
of form, size, roughness or smoothness, heat or cold,
pleasure or pain. So the nose can itch, or smart, or
tingle, as well as distinguish odors. The external eye
is the seat of the most acute sensibility. Wd feel
everywhere upon the surface, but especially with the
ends of our fiigers. This sense has relation to many