heir mental development. As
regards the ape family, it occupies a position between man and the
quadrupeds, and its intellectual activity may well be due in great
measure to an increased trust in sight and a decreased trust in smell in
gaining its conception of nature.

The question may arise, Why, if sight has this superiority over smell,
did it not long since gain predominance, and relegate smell to a minor
position? It may be answered that the superiority of sight is not
complete. In one particular this sense is inferior to smell. The leading
agency in the development of the sense organs of animals has been the
struggle for existence, including escape from enemies, and the
perception of food-animals or material. In these processes acuteness of
smell plays a very important part. It has, moreover, the advantage of
gathering information from all directions, while sight is very limited
in its range. The eye is so subject to injury that its multiplication
over the body would be rather disadvantageous than otherwise, while,
localized as it is, a movement of the head is necessary to any breadth
of vision, and the whole body must rotate to bring the complete horizon
under observation. It seems evident, from these considerations, that
sight is much inferior to smell in the timely perception of many forms
of danger. Light comes in straight lines only, and a movement of the
body is necessary to perceive perils lying outside these lines. Odors,
on the contrary, spread in all directions, and make themselves manifest
from the rear as well as the front.

In all probability this fact has had much to do with the continued
dependence of animals on smell. In fishes and reptiles a full sweep of
vision is so slowly gained that some more active sentinel sense is
requisite to safety. In mammals the head rotates more easily, but
valuable time is lost in the rotation of the whole body. These animals,
therefore, depend on both sight and smell, in some cases equally, in
some more fully on one or the other of these senses. When we reach the
semi-upright ape, we have to do with a form capable of turning the body
and observing the whole surrounding circle of objects more quickly and
readily than any quadruped. As a result, these animals have grown to
depend more fully on vision and less on smell than the quadrupeds.
Finally, in fully erect man, the power of quick turning and alert
observation of the whole circle of the horizon reaches its ultimat