eyes have been removed.

It might, however, be supposed that in the higher land vertebrates sight
is predominant, and that the diurnal mammals depend principally upon
their eyes for their knowledge of nature. But there are facts which
throw doubt upon this supposition. These facts are of two kinds,
external and internal. That the quadrupeds, in general, are highly
sensitive to odors is well known, and also that they trust very largely
to the sense of smell. Hunters are abundantly aware of this, and have to
be quite as careful to avoid being smelt by their game as to avoid being
seen. We have abundant evidence of the remarkable acuteness of this
sense in so high an animal as the dog, which can follow its prey for
miles by scent alone, and can distinguish the odors, not only of
different species, but of different individuals, being capable of
following the trail of one person amid the tracks of numerous others.

The internal evidence of this fact is equally significant. In the
vertebrates, in general, the olfactory lobe of the brain is largely
developed, much exceeding in size the lobe of the optic nerve. It forms
the anterior portion of the cerebrum, and in many instances constitutes
a large section of that organ, being marked off from it by only a slight
surface depression. If we can fairly judge, then, by anatomical
evidence, the sense of smell plays a very prominent part in the life of
all the lower vertebrates. If we take our domestic animals as an
example, the olfactory lobe of the horse is considerably larger than
that of man, though the brain, as a whole, is very much smaller, so
that, comparatively, this organ constitutes a much larger portion of the
total brain. The other domestic animals yield similar evidence of the
great activity of the sense of smell.

While there is no doubt that sight is an active sense in all the higher
quadrupeds, it evidently divides this activity with smell to a much
greater degree than is the case with man, in whom smell plays a minor
part, sight a major part, among the organs of sense.

This fact shows its effect in the comparative mental development of man
and the lower animals. Man, depending so largely on vision, gains the
broadest conception of the conditions of nature, with a consequent great
expansion of the intellect. The quadrupeds, depending to a considerable
degree upon smell for their conceptions of nature, are much narrower in
their range of information and lower in t