e of spirit apart from body, but that at present such
existence is beyond the realm of science.

The dependence of mind upon body in a general way is evident to every
one, upon the most general observation and thought. We know the effect
on the mind of disease, of good health, of hunger, of fatigue, of
overwork, of severe bodily injury, of blindness or deafness. We have,
perhaps, seen some one struck upon the head by a club, or run over by an
automobile, and have noted the tremendous consequences to the person's
mind. In such cases it sometimes happens that, as far as we can see,
there is no longer any mind in connection with that body. The most
casual observation, then, shows that mind and body are in some way most
intimately related.

=Finer Dependence.= Let us note this relation more in detail, and, in
particular, see just which part of the body it is that is connected with
the mind. First of all, we note the dependence of mind upon sense
organs. We see only with our eyes. If we close the eyelids, we cannot
see. If we are born blind, or if injury or disease destroys the retinas
of the eyes or makes the eyes opaque so that light cannot pass through
to the retinas, then we cannot see.

Similarly, we hear only by means of the ears. If we are born deaf, or if
injury destroys some important part of the hearing mechanism, then we
cannot hear. In like manner, we taste only by means of the taste organs
in the mouth, and smell only with the organs of smell in the nose. In a
word, our primary knowledge of the world comes only through the sense
organs. We shall see presently just how this sensing or perceiving is
accomplished.

=Dependence of Mind on Nerves and Brain.= We have seen how in a general
way the mind is dependent on the body. We have seen how in a more
intimate way it is dependent on the special sense organs. But the part
of the body to which the mind is most directly and intimately related is
the nervous system. The sense organs themselves are merely modifications
of the nerve ends together with certain mechanisms for enabling stimuli
to act on the nerve ends. The eye is merely the optic nerve spread out
to form the retina and modified in certain ways to make it sensitive to
ether vibrations. In addition to this, there is, of course, the focusing
mechanism of the eye. So for all the sense organs; they are, each of
them, some sort of modification of nerve-endings which makes them
sensitive to some particular forc