Let us now look briefly at the construction of the human body and the
duties which its various parts are intended to perform, after which we
will take note of the methods of preserving health in general, and the
diseases and injuries which must be guarded against.
First, some explanations of the terms used in these connections: We
divide all nature into three classes of objects, those belonging to the
Animal, Vegetable and Mineral Kingdoms, and all things belong in one or
another of these. They are also divided into organic and inorganic
bodies. The first are those having organs by which they grow, such as
animals and plants. Inorganic bodies are those which are without life of
their own, such as air, water, stone and the like. All inorganic bodies
are included in the mineral kingdom. Those organic bodies which have no
power to feel are included in the vegetable kingdom, and those which
have the power to feel form the animal kingdom. There are things in
nature which are so close to this dividing line that even scientists
disagree as to whether they belong to the vegetable or animal kingdom.
The parts of an organized body, such as the mouth or the foot of an
animal, the root or the leaf of a plant, are called the organs, and the
work which an organ is intended to perform is called its function. The
material out of which any organ is composed is called tissue, and in the
human body, for instance, at least six different kinds of tissue are
found, forming the various organs. We will speak of the various solids
and fluids of the body by name, only in connection with their ailments
and their care hereafter. The tissues themselves are composed of fifteen
of the sixty-five chemical elements, or simple substances, known to
exist in nature.
The various organs of similar structure and common purpose found in the
human body, when taken together, are called a system.
These are the Osseous System, the Muscular System, the Digestive System,
the Circulatory System, the Respiratory System and the Nervous System.
The Osseous System means the skeleton, which gives shape to the body and
supports it, enables us to move and extend our limbs, and protects the
delicate organs from injury. The Muscular System is the flesh of the
body, forming a pad or covering around the bones, and thus also serving
as a protection, in addition to producing at will the motions of our
limbs and the controllable organs. The Digestive System is composed of
those organs which receive, transmit and dispose of our food, separating
the waste matter from the useful, and giving the latter to our
nourishment and strength. The mouth, the stomach, the intestines, and
various other organs are included in this service.
The Circulatory System includes the heart, the arteries, the veins and
the capillaries, those organs which transmit and purify the blood,
building up all other organs by this essential fluid which is life. The
Respiratory System is that which transmits the air and makes use of it
in the body for purifying the blood, thus including the lungs, and the
passages and valves which lead thither. The Nervous System is that part
of the organism by which the different parts of the body are controlled
and caused to work together, and through which mind and body are
connected. The brain, the spinal cord, the nerves and the ganglia of the
nerves are the organs of the Nervous System. They have been compared
most appropriately to an intricate telegraph system, of which the brain
is the head office or directing intelligence, the spinal cord is the
main line, the nerves are the wires running to every station, and the
ganglia are the stations themselves.
In addition to these general systems which have been named we must take
note also of the skin, which covers the whole exterior of the body; the
mucous membrane, which covers the open cavities and lines the organs;
the urinary organs, which separate and discharge the liquid waste of the
body and thus are akin to the digestive system; and the organs of
generation and reproduction by which the race is perpetuated.