VIII.
DOMESTIC EXERCISE.
IN a work which aims to influence women to train the young to honor
domestic labor and to seek healthful exercise in home pursuits, there is
special reason for explaining the construction of the muscles and their
connection with the nerves, these being the chief organs of motion.
The muscles, as seen by the naked eye, consist of very fine fibres
or strings, bound up in smooth, silky casings of thin membrane. But each
of these visible fibres or strings the microscope shows to be made up of
still finer strings, numbering from five to eight hundred in each fibre.
And each of these microscopic fibres is a series or chain of elastic
cells, which are so minute that one hundred thousand would scarcely
cover a capital O on this page.
The peculiar property of the cells which compose the muscles is
their elasticity, no other cells of the body having this property. At
Fig. 51 is a diagram representing a microscopic muscular fibre, in which
the cells are relaxed, as in the natural state of rest. But when the
muscle contracts, each of its numberless cells in all its small fibres
becomes widened, making each fibre of the muscle shorter and thicker, as
at Fig. 52. This explains the cause of the swelling out of muscles when
they act.
[Illustration: A diagram of a muscle fiber at rest, consisting of a
row of seven circles bordered by two parallel lines above and below. The
figure is labeled with an italic a.]
[Illustration: A diagram of a contracted muscle fiber, consisting of
a row of seven ovals bordered by two parellel lines above and below. The
figure is labeled with an italic b.]
Every motion in every part of the body has a special
muscle to produce it, and many have other muscles to restore the part
moved to its natural state. The muscles that move or bend any part are
called flexors, and those that
restore the natural position are called
extensors.
 Fig. 53 represents the muscles of the arm after the skin and flesh
are removed. They are all in smooth silky cases, laid over each other,
and separated both by the smooth membranes that encase them and by
layers of fat, so as to move easily without interfering with each other.
They are fastened to the bones by strong tendons and cartilages; and
around the wrist, in the drawing, is shown a band of cartilage to
confine them in place. The muscle marked 8 is the extensor that
straightens the fingers after they have been closed by a flexor the
other side of the arm. In like manner, each motion of the arm and
fingers has one muscle to produce it and another to restore to the
natural position.
[Illustration: An illustration of the muscles in a human arm.]
The muscles are dependent on the brain and nerves for power to move.
It has been shown that the gray matter of the brain and spinal marrow
furnishes the stimulating power that moves the muscles, and causes
sensations of touch on the skin, and the other sensations of the several
senses. The white part of the brain and spinal marrow consists solely of
conducting tubes to transmit this influence. Each of the minute fibrils
of the muscles has a small conducting nerve connecting it with the brain
or spinal marrow, and in this respect each muscular fibril is separate
from every other.
When, therefore, the mind wills to move a flexor muscle of the arm,
the gray matter sends out the stimulus through
the nerves to the cells of each individual fibre of that muscle, and
they contract. When this is done, the nerve of sensation reports it to
the brain and mind. If the mind desires to return the arm to its former
position, then follows the willing, and consequent stimulus sent through
the nerves to the corresponding muscle; its cells contract, and the limb
is restored.
When the motion is a compound one, involving the action of several
muscles at the same time, a multitude of impressions are sent back and
forth to and from the brain through the nerves. But the person acting
thus is unconscious of all this delicate and wonderful mechanism. He
wills the movement, and instantly the requisite nervous power is sent to
the required cells and fibres, and they perform the motions required.
Many of the muscles are moved by the sympathetic system, over which the
mind has but little control.
Among the muscles and nerves so intimately connected, run the minute
capillaries of the blood, which furnish nourishment to all.
 Fig. 54 represents an artery at a,
which brings pure blood to a muscle from the heart. After meandering
through the capillaries at c, to
distribute oxygen and food from the stomach, the blood enters the vein,
b, loaded with carbonic acid and
water taken up in the capillaries, to be carried to the lungs or skin,
and thrown out into the air.
[Illustration: An illustration of a blood vessel running through a
muscle. Parts of the illustration are labeled with italicized letters.]
The manner in which the exercise of the muscles quickens the
circulation of the blood will now be explained. The veins abound in
every part of every muscle, and the large veins have
valves which prevent the blood
from flowing backward. If the wrist is grasped tightly, the veins of the
hand are immediately swollen.
This is owing to the fact that the blood is prevented from flowing
toward the heart by this pressure, and by the vein-valves from returning
into the arteries; while the arteries themselves, being placed deeper
down, are not so compressed, and continue to send the blood into the
hand, and thus it accumulates. As soon as this pressure is removed, the
blood springs onward from the restraint with accelerated motion. This
same process takes place when any of the muscles are exercised. The
contraction of any muscle presses some of the veins, so that the blood
can not flow the natural way, while the valves in the veins prevent its
flowing backward. Meantime the arteries continue to press the blood
along until the veins become swollen. Then, as soon as the muscle ceases
its contraction, the blood flows faster from the previous accumulation.
If, then, we use a number of muscles, and use them strongly and
quickly, there are so many veins affected in this way as to quicken the
whole circulation. The heart receives blood faster, and sends it to the
lungs faster. Then the lungs work quicker, to furnish the oxygen
required by the greater amount of blood. The blood returns with greater
speed to the heart, and the heart sends it out with quicker action
through the arteries to the capillaries. In the capillaries, too, the
decayed matter is carried off faster, and then the stomach calls for
more food to furnish new and pure blood. Thus it is that exercise gives
new life and nourishment to every part of the body.
It is the universal law of the human frame that
exercise is indispensable to the
health of the several parts. Thus, if a blood-vessel be tied up, so as
not to be used, it shrinks, and becomes a useless string; if a muscle be
condemned to inaction, it shrinks in size and diminishes in power; and
thus it is also with the bones. Inactivity produces softness, debility,
and unfitness for the functions they are designed to perform.
Now, the nerves, like all other parts of the body, gain
and lose strength according as they are exercised. If they have too much
or too little exercise, they lose strength; if they are exercised to a
proper degree, they gain strength. When the mind is continuously
excited, by business, study, or the imagination, the nerves of emotion
and sensation are kept in constant action, while the nerves of motion
are unemployed. If this is continued for a long time, the nerves of
sensation lose their strength from over-action, and the nerves of motion
lose their power from inactivity. In consequence, there is a morbid
excitability of the nervous, and a debility of the muscular system,
which make all exertion irksome and wearisome.
The only mode of preserving the health of these systems is to keep
up in them an equilibrium of action. For this purpose, occupations must
be sought which exercise the muscles and interest the mind; and thus the
equal action of both kinds of nerves is secured. This shows why exercise
is so much more healthful and invigorating when the mind is interested,
than when it is not. As an illustration, let a person go shopping with a
friend, and have nothing to do but look on. How soon do the continuous
walking and standing weary! But, suppose one, thus wearied, hears of the
arrival of a very dear friend: she can instantly walk off a mile or two
to meet her, without the least feeling of fatigue. By this is shown the
importance of furnishing, for young persons, exercise in which they will
take an interest. Long and formal walks, merely for exercise, though
they do some good, in securing fresh air, and some exercise of the
muscles, would be of triple benefit if changed to amusing sports, or to
the cultivation of fruits and flowers, in which it is impossible to
engage without acquiring a great interest.
It shows, also, why it is far better to trust to useful domestic
exercise at home than to send a young person out to walk for the mere
purpose of exercise. Young girls can seldom be made to realize the value
of health, and the
need of exercise to secure it, so as to feel much interest in walking
abroad, when they have no other object. But, if they are brought up to
minister to the comfort and enjoyment of themselves and others, by
performing domest ic duties, they will constantly be interested and
cheered in their exercise by the feeling of usefulness and the
consciousness of having performed their duty.
There are few young persons, it is hoped, who are brought up with
such miserable habits of selfishness and indolence that they can not be
made to feel happier by the consciousness of being usefully employed.
And those who have never been accustomed to think or care for any one
but themselves, and who seem to feel little pleasure in making
themselves useful, by wise and proper influences can often be gradually
awakened to the new pleasure of benevolent exertion to promote the
comfort and enjoyment of others. And the more this sacred and elevating
kind of enjoyment is tasted, the greater is the relish induced. Other
enjoyments often cloy; but the heavenly pleasure secured by virtuous
industry and benevolence, while it satisfies at the time, awakens fresh
desires for the continuance of so ennobling a good.
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