he foregoing sections. Just here we must pause to
give further attention to the invariable relation between the human mind
and the human brain.

The personality of human consciousness consists of the current of thoughts
and feelings flowing continuously as one of them rises for a time to
dominance only to fade when it leads to and is replaced by another
dominant element of thought. This current is affected by the messages
brought to the brain by nerves from the outer parts of the body where lie
the eye and ear and other sense-organs. In like manner the various
non-nervous parts of the body exert their influences upon consciousness,
but the affective processes, as they are called, are not as well understood
as the impressions passed inwards by the sense-organs along their nervous
roadways to the central organ, the brain. But the brain is the place where
the thinking individual resides; and this is one of the most important
teachings of psychology, for not only does it help us to understand the
evidence that human faculty has evolved, but it also inevitably brings us
to consider certain vital questions of metaphysics, such as the
immortality of the thinking individual after the material person with its
brain ceases to exist. However, the latter question is something which
does not concern us here; now it is most important to realize how
completely mind is connected with the brain.

Many of the facts demonstrating this connection are matters of common
knowledge. In deep and dreamless sleep the essential tissues of the brain
are inactive, and in correspondence with the cessation of material events
the thinking individual actually ceases to exist for a time. Any one who
has ever fainted is subsequently aware of the break in the current of
human consciousness when the blood does not fully supply the brain and
this organ ceases to function properly; a severe blow upon the head
likewise interrupts the normal physical processes, and at the same time
the mind is correspondingly affected. Again, a progressive alteration of
the brain as the result of diseased growth causes the mind to grow dim and
incapable. Sometimes infants are born which are so deficient mentally as
to be idiots, and an examination of the brain in such a case reveals
certain correlated defects in physical organization. These and similar
facts form the basis for the dictum that the development and evolution of
the brain mean the growth and evolution of human inte