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Hygienic Physiology

J >> Joel Dorman Steele >> Hygienic Physiology




FIG. 14.

[Illustration]

THE MUSCLES.

THE USE OF THE MUSCLES.--The skeleton is the image of death. Its unsightly
appearance instinctively repels us. We have seen, however, what uses it
subserves in the body, and how the ugly-looking bones abound in nice
contrivances and ingenious workmanship. In life, the framework is hidden
by the flesh. This covering is a mass of muscles, which by their
arrangement and their properties not only give form and symmetry to the
body, but also produce its varied movements.

In Fig. 14, we see the large exterior muscles. Beneath these are many
others; while deeply hidden within are tiny, delicate ones, too small to
be seen with the naked eye. There are, in all, about five hundred, each
having its special use, and all working in exquisite harmony and
perfection.

CONTRACTILITY.--The peculiar property of the muscles is their power of
contraction, whereby they decrease in length and increase in thickness.
[Footnote: The maximum force of this contraction has been estimated as
high as from eighty-five to one hundred and fourteen pounds per square
inch.] This may be caused by an effort of the will, by cold, by a sharp
blow, etc. It does not cease at death, but, in certain cold-blooded
animals, a contraction of the muscles is often noticed long after the head
has been cut off.

ARRANGEMENT OF THE MUSCLES. [Footnote: "Could we behold properly the
muscular fibers in operation, nothing, as a mere mechanical exhibition,
can be conceived more superb than the intricate and combined actions that
must take place during our most common movements. Look at a person running
or leaping, or watch the motions of the eye. How rapid, how delicate, how
complicated, and yet how accurate, are the motions required! Think of the
endurance of such a muscle as the heart, that can contract, with a force
equal to sixty pounds, seventy-five times every minute, for eighty years
together, without being weary."]--The muscles are nearly all arranged in
pairs, each with its antagonist, so that, as they contract and expand
alternately, the bone to which they are attached is moved to and fro. (See
p. 275.)

If you grasp the arm tightly with your hand just above the elbow joint,
and bend the forearm, you will feel the muscle on the inside (biceps,
_a_, Fig. 14) swell, and become hard and prominent, while the outside
muscle (triceps, _f_) will be relaxed. Now straighten the arm, and
the swelling and hardness of the inside muscle will vanish, while the
outside one will, in turn, become rigid. So, also, if you clasp the arm
just below the elbow, and then open and shut the fingers, you can feel the
alternate expanding and relaxing of the muscles on opposite sides of the
arms.

If the muscles on one side of the face become palsied, those on the other
side will draw the mouth that way. Squinting is caused by one of the
straight muscles of the eye (Fig. 17) contracting more strongly than its
antagonist.

KINDS OF MUSCLES.--There are two kinds of muscles, the _voluntary_,
which are under the control of our will, and the _involuntary_,
which are not. Thus our limbs stiffen or relax as we please, but the
heart beats on by day and by night. The eyelid, however, is both
voluntary and involuntary, so that while we wink constantly without
effort, we can, to a certain extent, restrain or control the motion.

STRUCTURE OF THE MUSCLES.--If we take a piece of lean beef and wash out
the red color, we can easily detect the fine fibers of which the meat is
composed. In boiling corned beef for the table, the fibers often separate,
owing to the dissolving of the delicate tissue which bound them together.
By means of the microscope, we find that these fibers are made up of
minute filaments (_fibrils_), and that each fibril is composed of a
row of small cells arranged like a string of beads. This gives the muscles
a peculiar striped (striated) appearance. [Footnote: The involuntary
muscles consist generally of smooth, fibrous tissue, and form sheets or
membranes in the walls of hollow organs. By their contraction they change
the size of cavities which they inclose. Some functions, however, like the
action of the heart, or the movements of deglutition (swallowing), require
the rapid, vigorous contraction, characteristic of the voluntary muscular
tissue--FLINT.] (See p. 276.) The cells are filled with a fluid or
semifluid mass of living (protoplasmic) matter.

FIG. 15.

[Illustration: _Microscopic view of a Muscle, showing, at one end, the
fibrillæ; and, at the other, the disks, or cells, of the fiber._]

The binding of so many threads into one bundle [Footnote: We shall learn
hereafter how these fibers are firmly tied together by a mesh of fine
connective tissue which dissolves in boiling, as just described] confers
great strength, according to a mechanical principle that we see
exemplified in suspension bridges, where the weight is sustained, not by
bars of iron, but by small wires twisted into massive ropes.

FIG. 16.

[Illustration: _Tendons of the Hand._]

THE TENDONS.--The ends of the muscles are generally attached to the bone
by strong, flexible, but inelastic tendons. [Footnote: The tendons may be
easily seen in the leg of a turkey as it comes on our table; so we may
study Physiology while we pick the bones.] The muscular fibers spring from
the sides of the tendon, so that more of them can act upon the bone than
if they went directly to it. Besides, the small, insensible tendon can
better bear the exposure of passing over a joint, and be more easily
lodged in some protecting groove, than the broad, sensitive muscle. This
mode of attachment gives to the limbs strength, and elegance of form.
Thus, for example, if the large muscles of the arm extended to the hand,
they would make it bulky and clumsy. The tendons, however, reach only to
the wrist, whence fine cords pass to the fingers (Fig. 16).

Here we notice two other admirable arrangements. 1. If the long tendons at
the wrist on contracting should rise, projections would be made and thus
the beauty of the slender joint be marred. To prevent this, a stout band
or bracelet of ligament holds them down to their place. 2. In order to
allow the tendon which moves the last joint of the finger to pass through,
the tendon which moves the second joint divides at its attachment to the
bone (Fig. 16). This is the most economical mode of packing the muscles,
as any other practicable arrangement would increase the bulk of the
slender finger.

FIG. 17.

[Illustration: _Muscles of the Right Eye:_ A, _superior
straight,_ B, _superior oblique passing through a pulley,_ D; G,
_inferior oblique,_ H, _external straight, and, back of it, the
internal straight muscle._]

Since the tendon can not always pull in the direction of the desired
motion, some contrivance is necessary to meet the want. The tendon (B)
belonging to one of the muscles of the eye, for example, passes through a
ring of cartilage, and thus a rotary motion is secured.

FIG. 18.

[Illustration: _The three classes of Levers, and also the foot as a
Lever._]

THE LEVERS OF THE BODY. [Footnote: A _lever_ is a stiff bar resting
on a point of support, called the _fulcrum_ (_F_), and having connected
with it a _weight_ (_W_) to be lifted, and a _power_ (_P_) to move it.
There are three classes of levers according to the arrangement of the
power, weight, and fulcrum. In the first class, the _F_ is between the
_P_ and _W_; in the second, the _W_ is between the _P_ and _F_; and in
the third, the _P_ is between the _W_ and _F_ (Fig. 18). A pump handle
is an example of the first; a lemon squeezer, of the second; and a
pair of fire tongs, of the third. See "Popular Physics," pp. 81-83, for a
full description of this subject, and for many illustrations.]--In
producing the motions of the body, the muscles use the bones as levers. We
see an illustration of the _first class_ of levers in the movements
of the head. The back or front of the head is the weight to be lifted, the
backbone is the fulcrum on which the lever turns, and the muscles at the
back or front of the neck exert the power by which we toss or bow the
head.

FIG. 19.

[Illustration: _The hand as a Lever of the third class._]

When we raise the body on tiptoe, we have an instance of the _second
class_. Here, our toes resting on the ground form the fulcrum the
muscles of the calf (gas-troc-ne'-mi-us, _j_ and so-le'-us, Fig. 14),
acting through the tendon of the heel, [Footnote: This is called the
Tendon of Achilles (_k_, Fig. 14) and is so named because, as the
fable runs, when Achilles was an infant his mother held him by the heel
while she dipped him in the River Styx, whose water had the power of
rendering one invulnerable to any weapon. His heel, not being wet, was his
weak point, to which Paris directed the fatal arrow--"This tendon," says
Mapother, "will bear one thousand pounds weight before it will break." The
horse is said to be "hamstrung," and is rendered useless, when the Tendon
of Achilles is cut. (see p. 284.)] are the power and the weight is borne
by the ankle joint.

An illustration of the _third class_ is found in lifting the hand
from the elbow. The hand is the weight, the elbow the fulcrum, and the
power is applied by the biceps muscle at its attachment to the radius (A,
Fig. 19.) In this form of the lever there is great loss of force, because
it is applied at such a distance from the weight, but there is a gain of
velocity, since the hand moves so far by such a slight contraction of the
muscle. The hand is required to perform quick motions, and therefore this
mode of attachment is desirable.

The nearer the power is applied to the resistance, the more easily the
work is done. In the lower jaw, for example, the jaw is the weight, the
fulcrum is the hinge joint at the back, and the muscles (temporal,
_d_, and the mas'-se'ter, _e_, Fig. 14) on each side are the
power. [Footnote: We may feel the contraction of the masseter by placing
our hand on the face when we work the jaw, while the temporal can be
readily detected by putting the fingers on the temple while we are
chewing. The tendon of the muscle (digastric)--one of those which open the
jaw--passes through a pulley (_c_, Fig. 14) somewhat like the one in
the eye.] They act much closer to the resistance than those in the hand,
since here we desire force, and there, speed.

FIG. 20.

[Illustration: _The Kneejoint;_ k, _the patella;_ f, _the
tendon._]

THE ENLARGEMENT OF THE BONES AT THE JOINTS not only affords greater
surface for the attachment of the muscles, as we have seen, but also
enables them to work to better advantage. Thus, in Fig. 20 it is evident
that a muscle acting in the line _f b_ would not bend the lower limb
so easily as if it were acting in the line _f k_, since in the former
case its force would be about all spent in drawing the bones more closely
together, while in the latter it would pull more nearly at a right angle.
Thus the tendon _f_, by passing over the patella, which is itself
pushed out by the protuberance _b_ of the thigh bone, pulls at a
larger angle, [Footnote: The chief use of the processes of the spine (Fig.
6) and other bones is, in the same way, to throw out the point on which
the power acts as far from the fulcrum as possible. The projections of the
ulna ("funny bone") behind the elbow, and that of the heel bone to which
the Tendon of Achilles is attached, are excellent illustrations (Fig. 1).]
and so the leg is thrown forward with ease in walking and with great force
in kicking.

HOW WE STAND ERECT.--The joints play so easily, and the center of gravity
in the body is so far above the foot, that the skeleton can not of itself
hold our bodies upright. Thus it requires the action of many muscles to
maintain this position. The head so rests upon the spine as to tend to
fall in front, but the muscles of the neck steady it in its place.
[Footnote: In animals the jaws are so heavy, and the place where the head
and spine join is so far back, that there can be no balance as there is in
man. There are therefore large muscles in their necks. We readily find
that we have none if we get on "all fours" and try to hold up the head. On
the other hand, gorillas and apes can not stand erect like man, for the
reason that their head, trunk, legs, etc., are not balanced by muscles, so
as to be in line with one another.] The hips incline forward, but are held
erect by the strong muscles of the back. The trunk is nicely balanced on
the head of the thigh bones. The great muscles of the thigh acting over
the kneepan tend to bend the body forward, but the muscles of the calf
neutralize this action. The ankle, the knee, and the hip lie in nearly the
same line, and thus the weight of the body rests directly on the keystone
of the arch of the foot. So perfectly do these muscles act that we never
think of them until science calls our attention to the subject, and yet to
acquire the necessary skill to use them in our infancy needed patient
lessons, much time, and many hard knocks.

FIG. 21.

[Illustration: _Action of the Muscles which keep the body erect._]

HOW WE WALK.--Walking is as complex an act as standing. It is really a
perilous performance, which has become safe only because of constant
practice. We see how violent it is when we run against a post in the dark,
and find with what headlong force we were hurling ourselves forward.
Holmes has well defined walking as a perpetual falling with a constant
self-recovery. Standing on one foot, we let the body fall forward, while
we swing the other leg ahead like a pendulum. Planting that foot on the
ground, to save the body from falling farther, we then swing the first
foot forward again to repeat the same operation. [Footnote: It is a
curious fact that one side of the body tends to outwalk the other; and so,
when a man is lost in the woods, he often goes in a circle, and at last
comes round to the spot whence he started.]

The shorter the pendulum, the more rapidly it vibrates; and so short-
legged people take quicker and shorter steps than long-legged ones.
[Footnote: In this respect, Tom Thumb was to Magrath, whose skeleton,
eight and one half feet high, is now in the Dublin Museum, what a little
fast-ticking, French mantel clock is to a big, old-fashioned, upright,
corner timepiece.] We are shorter when walking than when standing still,
because of this falling forward to take a step in advance. [Footnote:
Women find that a gown that will swing clear of the ground when they are
standing still, will drag the street when they are walking. The length of
the step may be increased by muscular effort, as when a line of soldiers
keep step in spite of their having legs of different lengths. Such a mode
of walking is necessarily fatiguing. (See p. 280.)]

In running, we incline the body more, and so, as it were, fall faster.
When we walk, one foot is on the ground all the time, and there is an
instant when both feet are planted upon it; but in running there is an
interval of time in each step when both feet are off the ground, and the
body is wholly unsupported. As we step alternately with the feet, we are
inclined to turn the body first to one side and then to the other. This
movement is sometimes counterbalanced by swinging the hand on the opposite
side. [Footnote: In ordinary walking the speed is nearly four miles an
hour, and can be kept up for a long period. But exercise and a special
aptitude for it enable some men to walk great distances in a relatively
short space of time. Trained walkers have gone seventy-five miles in
twenty hours, and walked the distance of thirty-seven miles at the rate of
five miles an hour. The mountaineers of the Alps are generally good
walkers, and some of them are not less remarkable for endurance than for
speed. Jacques Balmat, who was the first to reach the summit of Mont
Blanc, at sixteen years of age could walk from the hamlet of the Pélerins
to the mountain of La Côte in two hours,--a distance which the best-
trained travelers required from five to six hours to get over. At the time
of his last attempt to reach the top of Mont Blanc, this same guide, then
twenty years old, passed six days and four nights without sleeping or
reposing a single moment. One of his sons, Édouard Balmat, left Paris to
join his regiment at Genoa; he reached Chamouni the fifth day at evening,
having walked three hundred and forty miles. After resting two days, he
set off again for Genoa, where he arrived in two days. Several years
afterward, this same man left the baths at Louèche at two o'clock in the
morning, and reached Chamouni at nine in the evening, having walked a
distance equal to about seventy-five miles in nineteen hours. In 1844, an
old guide of De Saussure, eighty years old, left the hamlet of Prats, in
the valley of Chamouni, in the afternoon, and reached the Grand-Mulets at
ten in the evening; then, after resting some hours, he climbed the glacier
to the vicinity of the Grand Plateau, which has an altitude of about
thirteen thousand feet, and then returned to his village without
stopping.--_Wonders of the Body_.]

THE MUSCULAR SENSE.--When we lift an object, we feel a sensation of
weight, which we can compare with that experienced in lifting another
body. [Footnote: If a small ivory ball be allowed to roll down the cheek
toward the lips, it will appear to increase in weight. In general, the
more sensitive parts of the body recognize smaller differences in weight,
and the right hand is more accurate than the left. We are very apt,
however, to judge of the weight of a body from previous conceptions. Thus,
shortly after Sir Humphrey Davy discovered the metal potassium, he placed
a piece of it in the hand of Dr. Pierson, who exclaimed: "Bless me! How
heavy it is!" Really, however, potassium is so light that it will float on
water like cork.] By balancing it in the hand. The muscular sense is
useful to us in many ways. It guides us in standing or moving. We gratify
it when we walk erect and with an elastic step, and by dancing, jumping,
skating, and gymnastic exercises.

NECESSITY OF EXERCISE.--The effect of exercise upon a muscle is very
marked. [Footnote: The greater size of the breast (pectoral muscle) of a
pigeon, as compared with that of a duck, shows how muscle increases with
use. The breast of a chicken is white because it is not used for flight,
and therefore gets little blood.] By use it grows larger, and becomes
hard, compact, and darker-colored; by disuse it decreases in size, and
becomes soft, flabby, and pale.

Violent exercise, however, is injurious, since we then tear down faster
than nature can build up. Feats of strength are not only hurtful, but
dangerous. Often the muscles are strained or ruptured, and blood vessels
burst in the effort to outdo one's companions. [Footnote: Instances have
been known of children falling dead from having carried to excess so
pleasant and healthful an amusement as jumping the rope, and of persons
rupturing the Tendon of Achilles in dancing. The competitive lifting of
heavy weights is unwise, sometimes fatal.] (See p. 278.)

Two thousand years ago, Isocrates, the Greek rhetorician, said: "Exercise
for health, not for strength." The cultivation of muscle for its own sake
is a return to barbarism, while it enfeebles the mind, and ultimately the
body. The ancient gymnasts are said to have become prematurely old, and
the trained performers of our own day soon suffer from the strain they put
upon their muscular system. Few men have sufficient vigor to become both
athletes and scholars. Exercise should, therefore, merely supplement the
deficiency of our usual employment. _A sedentary life needs daily,
moderate exercise, which always stops short of fatigue_. This is a law
of health. (See p. 280.)

No education is complete which fails to provide for the development of the
muscles. Recesses should be as strictly devoted to play as study hours are
to work. Were gymnastics or calisthenics as regular an exercise as grammar
or arithmetic, fewer pupils would be compelled to leave school on account
of ill health; while spinal curvatures, weak backs, and ungraceful gaits
would no longer characterize so many of our best institutions.

TIME FOR EXERCISE.--We should not exercise after long abstinence from
food, nor immediately after a meal, unless the meal or the exercise be
very light. There is an old-fashioned prejudice in favor of exercise
before breakfast--an hour suited to the strong and healthy, but entirely
unfitted to the weak and delicate. On first rising in the morning, the
pulse is low, the skin relaxed, and the system susceptible to cold. Feeble
persons, therefore, need to be braced with food before they brave the
outdoor air.

WHAT KIND OF EXCERCISE TO TAKE.--For children, games are unequaled.
Walking, the universal exercise, [Footnote: The custom of walking, so
prevalent in England, has doubtless much to do with the superior physique
of its people. It is considered nothing for a woman to take a walk of
eight or ten miles, and long pedestrian excursions are made to all parts
of the country. The benefits which accrue from such an open-air life are
sadly needed by the women of our own land. A walk of half a dozen miles
should be a pleasant recreation for any healthy person.] is beneficial, as
it takes one into the open air and sunlight. Running is better, since it
employs more muscles, but it must not be pushed to excess, as it taxes the
heart, and may lead to disease of that organ. Rowing is more effectual in
its general development of the system. Swimming employs the muscles of the
whole body, and is a valuable acquirement, as it may be the means of
saving life. Horseback riding is a fine accomplishment, and refreshes both
mind and body. Gymnastic or calisthenic exercises bring into play all the
muscles of the body, and when carefully selected, and not immoderately
employed, are preferable to any other mode of indoor exercise. [Footnote:
The employment of the muscles in exercise not only benefits their especial
structure, but it acts on the whole system. When the muscles are put in
action, the capillary blood vessels with which they are supplied become
more rapidly charged with blood, and active changes take place, not only
in the muscles, but in all the surrounding tissues. The heart is required
to supply more blood, and accordingly beats more rapidly in order to meet
the demand. A larger quantity of blood is sent through the lungs, and
larger supplies of oxygen are taken in and carried to the various tissues.
The oxygen, by combining with the carbon of the blood and the tissues,
engenders a larger quantity of heat, which produces an action on the skin,
in order that the superfluous warmth may be disposed of. The skin is thus
exercised, as it were, and the sudoriparous and sebaceous glands are set
at work. The lungs and skin are brought into operation, and the lungs
throw off large quantities of carbonic acid, and the skin large quantities
of water, containing in solution matters which, if retained, would produce
disease in the body. Wherever the blood is sent, changes of a healthful
character occur. The brain and the rest of the nervous system are
invigorated, the stomach has its powers of digestion improved, and the
liver, pancreas, and other organs perform their functions with more vigor.
By want of exercise, the constituents of the food which pass into the
blood are not oxidized, and products which produce disease are engendered.
The introduction of fresh supplies of oxygen induced by exercise oxidizes
these products, and renders them harmless. As a rule, those who exercise
most in the open air will live the longest.--LANKESTER.] (See p. 280.)

THE WONDERS OF THE MUSCLES.--The grace, ease, and rapidity with which the
muscles contract are astonishing. By practice, they acquire a facility
which we call mechanical. The voice may utter one thousand five hundred
letters in a minute, yet each requires a distinct position of the vocal
organs. We train the muscles of the fingers till they glide over the keys
of the piano, executing the most exquisite and difficult harmony. In
writing, each letter is formed by its peculiar motions, yet we make them
so unconsciously that a skillful penman will describe beautiful curves
while thinking only of the idea that the sentence is to express. The mind
of the violinist is upon the music which his right hand is executing,
while his left determines the length of the string and the character of
each note so carefully that not a false sound is heard, although the
variation of a hair's breadth would cause a discord. In the arm of a
blacksmith, the biceps muscle may grow into the solidity almost of a club;
the hand of a prize fighter will strike a blow like a sledge hammer; while
the engraver traces lines invisible to the naked eye, and the fingers of
the blind acquire a delicacy that almost supplies the place of the missing
sense.

DISEASES, ETC.--l. _St. Vitus's Dance_ is a disease of the voluntary
muscles, whereby they are in frequent, irregular, and spasmodic motion
beyond the control of the will. All causes of excitement, and especially
of fear, should be avoided, and the general health of the patient
invigorated, as this disease is closely connected with a derangement of
the nervous system.

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