The study of the Human Body involves numerous other branches of
science, and, as a whole, is the most complex and intricate of all
the sciences. To explain its structure and workings we apply the
principles of Biology, Physiology, Chemistry, Physics, Psychology,
and Metaphysics.
The individual man, as a whole, is frequently forgotten both in
physiology and in medicine, owing to the extraordinary minuteness and
exactness with which each part and organ is examined and described. At
the outset, then, it should be remembered that the human body is an
organic whole, and what makes it _one_ is not the similarity or unity of
the machines and processes, for they are unlike and many; but it is the
unity of the one governing force, the _mind_, and especially the
_unconscious mind_, which presides over the body.
Nothing in the body is merely mechanical, although there is much
mechanism; all is vital, all is united in one great aim--the health and
well-being of the individual.
All organs and systems are held together and formed into one body by
means of a framework, partly fixed and partly movable, partly rigid and
partly flexible, partly hard and partly soft.
The _skeleton_ part of the framework is made of _bone_; flexibility is
given to certain parts by means of joints, which are simply smoothed and
rounded ends of bone covered with gristle to avoid friction, and joined
together by fiber and ligament for strength. This forms the rigid and
hard parts of the framework.
The flexible and soft part, which everywhere covers organs and muscles,
is composed of a layer of fat to preserve the warmth, as fat is a
non-conductor, and an outer covering of skin.
This framework is exquisitely adapted to give strong protection to the
vital parts so that they cannot readily be injured; and the whole of the
organs are so arranged and stowed away that a perfect human body is a
beautiful object full of symmetry and graceful curves and lines.
=Divisions of the Body.=--If we divide the body into six parts--four
limbs, trunk, and head and neck--we find each part contains about thirty
bones (counting the ribs in pairs) there being about _two hundred_ in
the entire body.
The height of the body depends mainly on the length of the bones of the
lower limbs.
=Everything in Pairs.=--In the body almost everything is paired, right
and left, giving it symmetry. There are but five central bones: two in
the head, one in the throat, and the breastbone and backbone (or spine);
and there are but five single muscles, all the rest--out of many
hundreds--being in pairs. In the interior, where economy rather than
symmetry is required, it is not so; there being as many single organs as
there are double.
=The Body Viewed as a Machine.=--A favorite way of looking at the body
as a whole is to regard it as an anatomical machine. In this view the
body has an internal skeleton, of which the chief feature is the central
axis or backbone.
Considering the skull and backbone as one, the body may be said to be
built up of two tubes. The smaller posterior or neural tube includes the
cavity of the skull and the vertebral canal. Within this tube is lodged
the nervous center, or engine, of the body. The anterior, or body, tube
is much larger, consisting of the face above, and the neck and trunk
below, and it contains the _four nutritive systems_ of life, so that the
whole body in section is like an eight with the lower circle immensely
exaggerated. The limbs, of course, are not tubular, and merely form part
of the machinery.
Adopting the simile of the human engine and boiler and machinery, we see
that the limbs, etc., are the machinery; the posterior tube the engines
and force that move them; and the anterior tube the human boiler that
generates the force. This boiler, like one in a steam engine, has an
upper and lower part. The upper part is where the steam is generated (in
lungs) and sent to the engine (the brain) by the heart. The lower part
is where the fuel is burned (the stomach) and the ashes and refuse drop
through (the intestines). So that the analogy between the two is close
and striking.
=Centers of Control.=--There are two distinct seats of government in the
human body: the one in the _upper brain_, or cortex, the other
principally in the very center of the human body. That in the upper
brain, or cortex, is the human will and the conscious mind. It has
absolute control given to it over the animal part of the human
life--that is, over the part that consists in the using of force, which
includes the nervous and locomotor systems, and the special senses.
_Nutritive Systems._--The other government, situated in the lower part
of the brain and spinal cord and in the center of the body--in front of
the spine and behind the stomach--is of an entirely different order. To
put this more plainly: The four systems that lie in the
body--_digestive_, _circulatory_, _respiratory_, and _excretory_--may be
termed the nutritive systems, being designed for the maintenance and
storage of life-forces. They are almost entirely under the control of
the involuntary nerve centers, and have full and undisputed sway over
life itself--that is, over the generating and storing of vital force,
rather than over its usage.