From the brain
runs the spinal marrow through the spine or backbone. From each side
of the spine the large nerves run out into innumerable smaller branches
to every portion of the body. The drawing shows only some of the larger
branches. Those marked 3 run to the neck and organs of the chest; those
marked 4 go to the arms; those below the arms, marked 3, go to the
trunk; and those marked 5 go to the legs.
The brain and nerves consist of two kinds of nervous matter--the _gray_,
which is supposed to be the portion that originates and controls a
nervous fluid which imparts power of action; and the _white_, which
seems to conduct this fluid to every part of the body.
The brain and nervous system are divided into distinct portions, each
having different offices to perform, and each acting independently of
the others; as, for example, one portion is employed by the mind in
thinking, and in feeling pleasurable or painful mental emotions; another
in moving the muscles; while the nerves that run to the nose, ears,
eyes, tongue, hands, and surface generally, are employed in seeing,
hearing, smelling, tasting, and feeling all physical sensations.
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