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.
2. _Convulsions_ are an involuntary contraction of the muscles.
Consciousness is wanting, while the limbs may be stiff or in spasmodic
action. (See p. 261.)
3. _Locked-jaw_ is a disease in which there are spasms and a
contraction of the muscles, usually beginning in the lower jaw. It is
serious, often fatal, yet it sometimes follows as trivial an injury as the
stroke of a whip lash, the lodgment of a bone in the throat, a fishhook in
the finger, or a tack in the sole of the foot.
4. _Gout_ is characterized by an acute pain located chiefly in the
small joints of the foot, especially those of the great toe, which become
swollen and extremely sensitive. It is generally accompanied by an excess
of uric acid in the blood, and a deposit of urate of soda about the
affected joint. Gout is often the result of high living, and of too much
animal food. It is frequently inherited.
5. _Rheumatism_ affects mainly the connective, white, fibrous tissue
of the larger joints. While gout is the punishment of the rich who live
luxuriously, rheumatism afflicts alike the poor and the rich. There are
two common forms of rheumatism--the inflammatory or acute, and the
chronic. The latter is of long continuance; the former terminates more
speedily. The acute form is probably a disease of the blood, which carries
with it some poisonous matter that is deposited where the fibrous tissue
is most abundant. The disease flies capriciously from one joint to
another, and the pain caused by even the slightest motion deprives the
sufferer of the use of the disabled part and its muscles. Its chief danger
lies in the possibility of its affecting the vital organs. Chronic
rheumatism--the result of repeated attacks of the acute--leads to great
suffering, and oftentimes to disorganization of the joints and an
interference with the movements of the heart.
6. _Lumbago_ is an inflammation of the lumbar muscles and fascia.
[Footnote: Lumbago is really a form of myalgia, a disease which, has its
seat in the muscles, and may thus affect any part of the body. Doubtless
much of what is commonly called "liver" or "kidney complaint" is only, in
one case, myalgia of the chest or abdominal walls near the liver, or, in
the other, of the back and loins near the kidneys. Chronic liver disease
is comparatively rare in the Northern States, and pain in the side is not
a prominent symptom; while certain diseases of the kidneys, which are as
surely fatal as pulmonary consumption, are not attended by pain in the
back opposite these organs.--WEY.] It may be so moderate as to produce
only a "lame back," or so severe as to disable, as in the case of what is
popularly termed a "crick in the back." Strong swimmers who sometimes
drown without apparent cause are supposed to be seized in this way.
7. _A Ganglion_, or what is vulgarly called a "weak" or "weeping"
sinew, is the swelling of a bursa. [Footnote: A bursa is a small sack
containing a lubricating fluid to prevent friction where tendons play over
hard surfaces. There is one shaped like an hourglass on the wrist, just at
the edge of the palm. By pressing back the liquid it contains, this bursa
may be clearly seen.] It sometimes becomes so distended by fluid as to be
mistaken for bone. If on binding something hard upon it for a few days it
does not disappear, a physician will remove the liquid by means of a
hypodermic syringe, or perhaps cause it to be absorbed by an external
application of iodine.
PRACTICAL QUESTIONS.
1. What class of lever is the foot when we lift a weight on the toes?
2. Explain the movement of the body backward and forward, when resting
upon the thigh bone as a fulcrum.
3. What class of lever do we use when we lift the foot while sitting down?
4. Explain the swing of the arm from the shoulder.
5. What class of lever is used in bending our fingers?
6. What class of lever is our foot when we tap the ground with our toes?
7. What class of lever do we use when we raise ourselves from a stooping
position?
8. What class of lever is the foot when we walk?
9. Why can we raise a heavier weight with our hand when lifting from the
elbow than from the shoulder?
10. What class of lever do we employ when we are hopping, the thigh bone
being bent up toward the body and not used?
11. Describe the motions of the bones when we are using a gimlet.
12. Why do we tire when we stand erect?
13. Why does it rest us to change our work?
14. Why and when is dancing a beneficial exercise?
15. Why can we exert greater force with the back teeth than with the front
ones?
16. Why do we lean forward when we wish to rise from a chair?
17. Why does the projection of the heel bone make walking easier?
18. Does a horse travel with less fatigue over a flat than a hilly
country?
19. Can you move your upper jaw?
20. Are people naturally right or left-handed?
21. Why can so few persons move their ears by the muscles?
22. Is the blacksmith's right arm healthier than the left?
23. Boys often, though foolishly, thrust a pin into the flesh just above
the knee. Why is it not painful?
24. Will ten minutes' practice in a gymnasium answer for a day's exercise?
25. Why would an elastic tendon be unfitted to transmit the motion of a
muscle?
26. When one is struck violently on the head, why does he instantly fall?
27. What is the cause of the difference between light and dark meat in a
fowl?
III.
THE SKIN.
A protection from the outer world, it is our only means of communicating
with it. Insensible itself, it is the organ of touch. It feels the
pressure of a hair, yet bears the weight of the body. It yields to every
motion of that which it wraps and holds in place. It hides from view the
delicate organs within, yet the faintest tint of a thought shines through,
while the soul paints upon it, as on a canvas, the richest and rarest of
colors.
ANALYSIS OF THE SKIN.
_
_ | 1. The Cutis; its Composition and Character.
| 1. THE STRUCTURE | 2. The Cuticle; its Composition and Character.
| OF THE SKIN. | 3. The Value of the Cuticle.
| |_4. The Complexion.
| _
| | a. _Description._
| _ | b. _Method of Growth._
| | 1. The Hair.....| c. _As an Instrument of
| | | Feeling._
| 2. THE HAIR AND | | d. _Indestructibility of
| THE NAILS. | |_ the Hair._
| | _
| |_2. The Nails....| a. _Uses._
| |_b. _Method of Growth._
| _
| 3. THE MUCOUS | 1. The Structure.
| MEMBRANE | 2. Connective Tissue.
| |_3. Fat.
| _
| | 1. Number and Kinds of Teeth.
| | _
| | 1. The Two Sets.| 1. _The Milk Teeth._
| | |_2. _The Permanent Teeth._
| |
| 4. THE TEETH. | 2. Structure of the Teeth.
| | 3. The Setting of the Tooth in the Jaw.
| | 4. The Decay of the Teeth.
| |_5. The Preservation of the Teeth.
| _ _
| | 1. The Two Kinds.| 1. _Oil Glands._
| | |_2. _Perpiratory Glands._
| |
| 5. THE GLANDS | 2. The Perspiration.
| | 3. The Absorbing Power of the Skin. (See
| |_ Lymphatics.)
| _
| | 1. About Washing and Bathing.
| | 2. The Reaction.
| | 3. Sea Bathing. _
| 6. HYGIENE | | a. _General Principles._
| | | b. _Linen._
| | | c. _Cotton._
| |_4. Clothing.......| d. _Woolen._
| | e. _Flannel._
| | f. _Color of Clothing._
| | g. _Structure of
| | Clothing._
| | h. _Insufficient
| _ |_ Clothing._
| | 1. Erysipelas.
| | 2. Salt Rheum.
|_7. DISEASES. | 3. Corns.
| 4. Ingrowing Nails.
| 5. Warts.
|_6. Chilblains.
THE SKIN.
THE SKIN is a tough, thin, close-fitting garment for the protection of the
tender flesh. Its perfect elasticity beautifully adapts it to every motion
of the body. We shall learn hereafter that it is more than a mere
covering, being an active organ, which does its part in the work of
keeping in order the house in which we live. It oils itself to preserve
its smoothness and delicacy, replaces itself as fast as it wears out, and
is at once the perfection of use and beauty.
1. STRUCTURE OF THE SKIN.
CUTIS AND CUTICLE.--What we commonly call the skin--viz., the part raised
by a blister--is only the cuticle [Footnote: _Cuticula_, little skin.
It is often styled the scarfskin, and also the epidermis (_epi_,
upon; and _derma_, skin).] or covering of the cutis or true skin. The
latter is full of nerves and blood vessels, while the former neither
bleeds [Footnote: We notice this in shaving; for if a razor goes below the
cuticle, it is followed by pain and blood. So insensible is this outer
layer that we can run a pin through the thick mass at the roots of the
nails without discomfort.] nor gives rise to pain, neither suffers from
heat nor feels the cold.
The cuticle is composed of small, flat cells or scales. These are
constantly shed from the surface in the form of scurf, dandruff, etc., but
are as constantly renewed from the cutis [Footnote: We see how rapidly
this change goes on by noticing how soon a stain of any kind disappears
from the skin. A snake throws off its cuticle entire, and at regular
intervals.] below.
Under the microscope, we can see the round cells of the cuticle, and how
they are flattened and hardened as they are forced to the surface. The
immense number of these cells surpasses comprehension. In one square inch
of the cuticle, counting only those in a single layer, there are over a
billion horny scales, each complete in itself.--HARTING.
FIG. 22.
[Illustration: A _represents a vertical section of the Cuticle._ B,
_lateral view of the cells._ C, _flat side of scales like_ d,
_magnified 250 diameters, showing the nucleated cells transformed into
broad scales._]
VALUE OF THE CUTICLE.--In the palm of the hand, the sole of the foot, and
other parts especially liable to injury, the cuticle is very thick. This
is a most admirable provision for their protection. [Footnote: We can hold
the hand in strong brine with impunity, but the smart will quickly tell us
when there is even a scratch in the skin. Vaccine matter must be inserted
beneath the cuticle to take effect. This membrane doubtless prevents many
poisonous substances from entering the system.] By use, it becomes callous
and horny. The boy who goes out barefoot for the first time, "treading as
if on eggs," can soon run where he pleases among thistles and over stones.
The blacksmith handles hot iron without pain, while the mason lays stones
and works in lime, without scratching or corroding his flesh.
THE COMPLEXION.--In the freshly made cells on the lower side of the
cuticle, is a pigment composed of tiny grains. [Footnote: These grains are
about 1/2000 of an inch in diameter, and, curiously enough, do not appear
opaque, but transparent and nearly colorless.--MARSHALL.] In the varying
tint of this coloring matter, lies the difference of hue between the
blonde and the brunette, the European and the African. In the purest
complexion, there is some of this pigment, which, however, disappears as
the fresh, round, soft cells next the cutis change into the old, flat,
horny scales at the surface.
Scars are white, because this part of the cuticle is not restored. The sun
has a powerful effect upon the coloring matter, and so we readily "tan" on
exposure to its rays. If the color gathers in spots, it forms freckles.
[Footnote: This action of the sun on the pigment of the skin is very
marked. Even among the Africans, the skin is observed to lose its intense
black color in those who live for many months in the shades of the forest.
It is said that Asiatic and African women confined within the walls of the
harem, and thus secluded from the sun, are as fair as Europeans. Among the
Jews who have settled in Northern Europe, are many of light complexion,
while those who live in India are as dark as the Hindoos. Intense heat
also increases this coloring matter, and thus a furnace-man's skin, even
where protected by clothing, becomes completely bronzed. The black pigment
has been known to disappear during severe illness, and a lighter color to
be developed in its place. Among the negroes, are sometimes found people
who have no complexion, _i. e._, there is no coloring matter in their
skin, hair, or the iris of their eyes. These persons are called Albinos.]
II. HAIR AND NAILS.
The Hair and the Nails are modified forms of the cuticle.
FIG. 23.
[Illustration: A _Hair, magnified 600 diameters._ S, _the sac
(follicle);_ P, _the papilla, showing the cells and the blood
vessels:_ V.]
THE HAIR is a protection from heat and cold, and shields the head from
blows. It is found on nearly all parts of the body, except the palms of
the hands and the soles of the feet. The outside of a hair is hard and
compact, and consists of a layer of colorless scales, which overlie one
another like the shingles of a house; the interior is porous, [Footnote:
In order to examine a hair, it should be put on the slide of the
microscope, and covered with a thin glass, while a few drops of alcohol
are allowed to flow between the cover and the slide. This causes the air,
which fills the hair and prevents our seeing its structure, to escape.]
and probably conveys the liquids by which it is nourished.
Each hair grows from a tiny bulb (papilla), which is an elevation of the
cutis at the bottom of a little hollow in the skin. From the surface of
this bulb, the hair is produced, like the cuticle, by the constant
formation of new cells at the bottom. When the hair is pulled out, this
bulb, if uninjured, will produce a new one; but, when once destroyed, it
will never grow again. [Footnote: Hair grows at the rate of about five to
seven inches in a year. It is said to grow after death. This appearance is
due to the fact that by the shrinking of the skin the part below the
surface is caused to project, which is especially noticeable in the
beard.] The hair has been known to whiten in a single night by fear,
fright, or nervous excitement. When the color has once changed, it can not
be restored. [Footnote: Hair dyes, or so-called "hair restorers," are
almost invariably deleterious substances, depending for their coloring
properties upon the action of lead or lunar caustic. Frequent instances of
hair poisoning have occurred, owing to the common use of such dangerous
articles. If the growth of the hair be impaired, the general constitution
or the skin needs treatment. This is the work of a skillful physician, and
not of a patent remedy. Dame Fashion has her repentant freaks as well as
her ruinous follies, and it is a healthful sign that the era of universal
hair dyeing has been blotted out from her present calendar, and the gray
hairs of age are now honored with the highest place in "style" as well as
in good sense and cleanliness.] (See p. 285.)
Wherever hair exists, tiny muscles are found, interlaced among the fibers
of the skin. These, when contracting under the influence of cold or
electricity, pucker up the skin, and cause the hair to stand on end.
[Footnote: In horses and other animals which are able to shake the whole
skin, this muscular tissue is much more fully developed than in man.] The
hairs themselves are destitute of feeling. Nerves, however, are found in
the hollows in which the hair is rooted, and so one feels pain when it is
pulled. [Footnote: These nerves are especially abundant in the whiskers of
the cat, which are used as feelers.] Thus the insensible hairs become
wonderfully delicate instruments to convey an impression of even the
slightest touch.
FIG. 24.
[Illustration: A, _a perspiratory tube with its gland;_ B, _a hair
with a muscle and two oil glands;_ C, _cuticle;_ D, _the
papillæ;_ and E, _fat cells._]
Next to the teeth and bones, the hair is the least destructible part of
the body, and its color is often preserved for many years after the other
portions have gone to decay. [Footnote: Fine downy hairs, such as are
general upon the body, have been detected in the little fragments of skin
found beneath the heads of the nails by which, centuries ago, certain
robbers were fastened to the church doors, as a punishment for their
sacrilege.]
THE NAILS protect the ends of the tender finger, and toe, and give us
power more firmly to grasp and easily to pick up any object we may desire.
They enable us to perform a hundred little, mechanical acts which else
were impossible. At the same time, their delicate color and beautiful
outline give a finish of ornament to that exquisite instrument, the hand.
The nail is firmly set in a groove (matrix) in the cuticle, from which it
grows at the root in length [Footnote: By making a little mark on the nail
near the root we can see, week by week, how rapidly this process goes on,
and so form some idea of what a multitude of cells must be transformed
into the horny matter of the nail.] and from beneath in thickness. So long
as the matrix at the root is uninjured, the nail will be replaced after
any accident. (See p. 288.)
III. THE MUCOUS MEMBRANE.
STRUCTURE.--At the edges of the openings into the body, the skin seems to
stop and give place to a tissue which is redder, more sensitive, more
liable to bleed, and is moistened by a fluid, or mucus, as it is called.
Really, however, the skin does not cease, but passes into a more delicate
covering of the same general structure, viz., an outer, hard, bloodless,
insensible layer, and an inner, soft, sanguine, nervous one. [Footnote:
With a dull knife, we can scrape from the mucous membrane which lines the
mouth some of the cuticle for examination under the microscope. In a
similar way, we can obtain cuticle from the surface of the body for study
and comparison.] Thus every part of the body is wrapped in a kind of
double bag, made of tough skin on the outside, and tender mucous membrane
on the inside.
CONNECTIVE TISSUE.--The cutis and the corresponding layer of the mucous
membrane consist chiefly of a fibrous substance interlaced, like felt. It
is called connective tissue, because it connects all the different parts
of the body. It spreads from the cutis, invests muscles, bones, and
cartilages, and thence passes into the mucous membrane. So thoroughly does
it permeate the body, that, if the other tissues were destroyed, it would
give a perfect model of every organ. [Footnote: It is curious to notice
how our body is wrapped in membrane. On the outside, is the skin
protecting from exterior injury, and, on the inside, is the mucous
membrane reaching from the lips to the innermost air cell of the lungs.
Every organ is enveloped in its membrane. Every bone has its sheath. Every
socket is lined. Even the separate fibers of muscles have their covering
tissue. The brain and the spinal cord are triply wrapped, while the eye is
only a membranous globe filled with fluid. These membranes protect and
support the organs they enfold, but, with that wise economy so
characteristic of nature everywhere, they have also an important function
to perform. They are the _filters_ of the body. Through their pores
pass alike the elements of growth, and the returning products of waste. On
one side, bathed by the blood, they choose from it suitable food for the
organ they envelop, and many of them in their tiny cells, by some
mysterious process, form new products,--put the finishing touches, as it
were, upon the material ere it is deposited in the body.] It can be seen
in a piece of meat as a delicate substance lying between the layers of
muscle, where it serves to bind together the numerous fibers of which they
are composed.
Connective tissue yields gelatine on boiling, and is the part which tans
when hides are manufactured into leather. It is very elastic, so that when
you remove your finger after pressing upon the skin, no indentation is
left. [Footnote: In dropsy, this elasticity is lost by distension, and
there is a kind of "pitting," as it is called, produced by pressure.] It
varies greatly in character,--from the mucous membrane, where it is soft
and tender, to the ligaments and tendons which it largely composes, where
it is strong and dense. [Footnote: The leather made from this tissue
varies as greatly, from the tough, thick oxhide, to the soft, pliable kid
and chamois skin.]
FAT is deposited as an oil in the cells [Footnote: So tiny are these
cells, that there are over sixty-five million in a cubic inch of fat. As
they are kept moist, the liquid does not ooze out, but, on drying, it
comes to the surface, and thus a piece of fat feels oily when exposed to
the air. The quantity of fat varies with the state of nutrition. In
corpulent persons, the masses of fat beneath the skin, in the mesentery,
on the surface of the heart and great vessels, between the muscles, and in
the neighborhood of the nerves, are considerably increased. Conversely, in
the emaciated we sometimes find beneath the skin nucleated cells, which
contain only one oil drop. Many masses of fat which have an important
relation to muscular actions--such as the fat of the orbit or the cheek--
do not disappear in the most emaciated object. Even in starvation, the
fatty substances of the brain and spinal cord are retained.--VALENTIN.] of
this tissue, just beneath the skin (Fig. 24), giving roundness and
plumpness to the body, and acting as an excellent nonconductor for the
retention of heat. It collects as pads in the hollows of the bones, around
the joints, and between the muscles, causing them to glide more easily
upon each other. As marrow, it nourishes the skeleton, and also
distributes the shock of any jar the limb may sustain.
It is noticeable, however, that fat does not gather within the cranium,
the lungs, or the eyelids, where its accumulation would clog the organs.
IV. THE TEETH.