Nitrogen 76.95
Oxygen 15.67
Carbon dioxide 4.38
Water vapor 2
Argon 1
In other words, there is a loss between 4 and 5 per cent oxygen, and nearly
a corresponding gain in carbon dioxide, in expired air. There are also some
other organic substances present.
[Illustration: The respiration of cells.]
Cell Respiration.--It has been shown, in the case of very simple animals,
such as the _amoeba_, that when oxidation takes place in a cell, work
results from this oxidation. The oxygen taken into the lungs is not used
there, but is carried by the blood to such parts of the body as need oxygen
to oxidize food materials in the cells. Since work is done in the cells of
the body, food and oxygen are therefore required. The quantity of oxygen
used by the body is nearly dependent on the amount of work performed.
Oxygen is constantly taken from the blood by tissues in a state of rest and
is used up when the body is at work. This is suggested by the fact that in
a given time a man, when working, gives off more oxygen (in carbon dioxide)
than he takes in during that time.
While work is being done certain wastes are formed in the cell. Carbon
dioxide is given off when carbon is burned. But when proteins are burned,
another waste product containing nitrogen is formed. This must be passed
off from the cells, as it is a poison. Here again the lymph and blood, the
common carriers, take the waste material to points where it may be
_excreted_ or passed out of the body.
The Mechanics of Respiration. The Pleura.--The lungs are covered with a
thin elastic membrane, the _pleura_. This forms a bag in which the lungs
are hung. Between the walls of the bag and the lungs is a space filled with
lymph. By this means the lungs are prevented from rubbing against the walls
of the chest.
[Illustration: The chest cavity (_a_) at the time of a full breath; (_b_),
after an expiration. Explain how the cavity for lungs is made larger.]
Breathing.--In every full breath there are two distinct movements,
inspiration (taking air in) and expiration (forcing air out). In man an
inspiration is produced by the contraction of the muscles between the ribs,
together with the contraction of the diaphragm, the muscular wall just
below the heart and lungs; this results in pulling down the diaphragm and
pulling upward and outward of the ribs, thus making the space within the
chest cavity larger. The lungs, which lie within this cavity, are filled by
the air rushing into the larger space thus made. That this cavity is larger
than it was at first may be demonstrated by a glance at the accompanying
figure. An expiration is simpler than an inspiration, for it requires no
muscular effort; the muscles relax, the breastbone and ribs sink into
place, while the diaphragm returns to its original position.
[Illustration: Apparatus to show the mechanics of breathing.]
A piece of apparatus which illustrates to a degree the mechanics of
breathing may be made as follows: Attach a string to the middle of a piece
of sheet rubber. Tie the rubber over the large end of a bell jar. Pass a
glass Y-tube through a rubber stopper. Fasten two small toy balloons to the
branches of the tube. Close the small end of the jar with the stopper.
Adjust the tube so that the balloons shall hang free in the jar. If now the
rubber sheet is pulled down by means of the string, the air pressure in the
jar is reduced and the toy balloons within expand, owing to the air
pressure down the tube. When the rubber is allowed to go back to its former
position, the balloons collapse.
[Illustration: Diagram showing the relative amounts of tidal, complemental,
reserve, and residual air. The brace shows the average lung capacity for
the adult man.]
Rate of Breathing and Amount of Air Breathed.--During quiet breathing, the
rate of inspiration is from fifteen to eighteen times per minute; this rate
largely depends on the amount of physical work performed. About 30 cubic
inches of air are taken in and expelled during the ordinary quiet
respiration. The air so breathed is called _tidal air_. In a "long" breath,
we take in about 100 cubic inches in addition to the tidal air. This is
called _complemental air_. By means of a forced expiration, it is possible
to expel from 75 to 100 cubic inches more than tidal air; this air is
called _reserve air_. What remains in the lungs, amounting to about 100
cubic inches, is called the _residual air_. The value of deep breathing is
seen by a glance at the diagram. It is only by this means that we clear the
lungs of the reserve air with its accompanying load of carbon dioxide.
Respiration under Nervous Control.--The muscular movements which cause an
inspiration are partly under the control of the will, but in part the
movement is beyond our control. The nerve centers which govern inspiration
are part of the sympathetic nervous system. Anything of an irritating
nature in the trachea or larynx will cause a sudden expiration or cough.
When a boy runs, the quickened respiration is due to the fact that oxygen
is used up rapidly and a larger quantity of carbon dioxide is formed. The
carbon dioxide in the blood stimulates the nervous center which has control
of respiration to greater activity, and quickened inspiration follows.
Need of Ventilation.--During the course of a day the lungs lose to the
surrounding air nearly two pounds of carbon dioxide. This means that about
three fifths of a cubic foot is given off by each person during an hour.
When we are confined for some time in a room, it becomes necessary to get
rid of this carbon dioxide. This can be done only by means of proper
ventilation. A considerable amount of moisture is given off from the body,
and this moisture in a crowded room is responsible for much of the
discomfort. The air becomes humid and uncomfortable. It has been found that
by keeping the air in motion in such a room (as through the use of electric
fans) much of this discomfort is obviated.
The presence of impurities in the air of a room may easily be determined by
its odor. The odor of a poorly ventilated room is due to organic impurities
given off with the carbon dioxide. This, fortunately, gives us an index of
the amount of waste material in the air. Among the factors which take
oxygen from the air in a closed room and produce carbon dioxide are burning
gas or oil lamps and stoves, and the presence of a number of people.
[Illustration: Three ways of ventilating a room. _i_, inlet for air; _o_,
outlet for air. Which is the best method of ventilation? Explain.]
Proper Ventilation.--Ventilation consists in the removal of air that has
been used, and the introduction of a fresh supply to take its place. Heated
air rises, carrying with it much of the carbon dioxide and other
impurities. A good method of ventilation for the home is to place a board
two or three inches high between the lower sash and the frame of a window
or to have the window open an inch or so at the top and the bottom. An open
fireplace in a room aids in ventilation because of the constant draft up
the flue.
Sweeping and Dusting.--It is very easy to demonstrate the amount of dust in
the air by following the course of a beam of light in a darkened room. We
have already proved that spores of mold and yeast exist in the air. That
bacteria are also present can be proved by exposing a sterilized gelatin
plate to the air in a schoolroom for a few moments.[47]
Footnote 47: Expose two sterilized dishes containing culture
media; one in a room being swept with a damp broom, and the
other in a room which is being swept in the usual manner.
Note the formation of colonies of bacteria in each dish. In
which dish does the more abundant growth take place?
Many of the bacteria present in the air are active in causing diseases of
the respiratory tract, such as diphtheria, membranous croup, and
tuberculosis. Other diseases, as colds, bronchitis (inflammation of the
bronchial tubes), and pneumonia (inflammation of the tiny air sacs of the
lungs), are also caused by bacteria.
[Illustration: Plate culture exposed for five minutes in a school hall
where pupils were passing to recitations. Each spot is a colony of bacteria
or mold.]
Dust, with its load of bacteria, will settle on any horizontal surface in a
room not used for three or four hours. Dusting and sweeping should always
be done with a damp cloth or broom, otherwise the bacteria are simply
stirred up and sent into the air again. The proper watering of streets
before they are swept is also an important factor in health. Much dust is
composed largely of dried excreta of animals. Soft-coal smoke does its
share to add to the impurities of the air, while sewer gas and illuminating
gas are frequently found in sufficient quantities to poison people. Pure
air is, as can be seen, almost an impossibility in a great city.
[Illustration: A sleeping porch, an ideal way to get fresh air at night.]
How to get Fresh Air.--As we know, green plants give off in the sunlight
considerable more oxygen than they use, and they use up carbon dioxide. The
air in the country is naturally purer than in the city, as smoke and
bacteria are not so prevalent there, and the plants in abundance give off
oxygen. In the city the night air is purer than day air, because the
factories have stopped work, the dust has settled, and fewer people are on
the streets. The old myth of "night air" being injurious has long since
been exploded, and thousands of people of delicate health, especially those
who have weak throat or lungs, are regaining health by sleeping out of
doors or with the windows wide open. The only essential in sleeping out of
doors or in a room with a low temperature is that the body be kept warm and
the head be protected from strong drafts by a nightcap or hood. Proper
ventilation at _all_ times is one of the greatest factors in good health.
Change of Air.--Persons in poor health, especially those having
tuberculosis, are often cured by a change of air. This is not always so
much due to the composition of the air as to change of occupation, rest,
and good food. Mountain air is dry, and relatively free from dust and
bacteria, and often helps a person having tuberculosis. Air at the seaside
is beneficial for some forms of disease, especially hay fever and bone
tuberculosis. Many sanitariums have been established for this latter
disease near the ocean, and thousands of lives are being annually saved in
this way.
[Illustration: Unfavorable sleeping conditions. Explain why unfavorable.]
Ventilation of Sleeping Rooms.--Sleeping in close rooms is the cause of
much illness. Beds ought to be placed so that a constant supply of fresh
air is given without a direct draft. This may often be managed with the use
of screens. Bedroom windows should be thrown open in the morning to allow
free entrance of the sun and air, bedclothes should be washed frequently,
and sheets and pillow covers often changed. Bedroom furniture should be
simple, and but little drapery allowed in the room.
Hygienic Habits of Breathing.--Every one ought to accustom himself upon
going into the open air to inspire slowly and deeply to the full capacity
of the lungs. A slow expiration should follow. Take care to force the air
out. Breathe through the nose, thus warming the air you inspire before it
enters the lungs and chills the blood. Repeat this exercise several times
every day. You will thus prevent certain of the air sacs which are not
often used from becoming hardened and permanently closed.
Relation of Proper Exercise to Health.--We are all aware that exercise in
moderation has a beneficial effect upon the human organism. The pale face,
drooping shoulders, and narrow chest of the boy or girl who takes no
regular exercise is too well known. Exercise, besides giving direct use of
the muscles, increases the work of the heart and lungs, causing deeper
breathing and giving the heart muscles increased work; it liberates heat
and carbon dioxide from the tissues where the work is taking place, thus
increasing the respiration of the tissues themselves, and aids mechanically
in the removal of wastes from tissues. It is well known that exercise, when
taken some little time after eating, has a very beneficial effect upon
digestion. Exercise and especially games are of immense importance to the
nervous system as a means of rest. The increasing number of playgrounds in
this country is due to this acknowledged need of exercise, especially for
growing children.
Proper exercise should be moderate and varied. Walking in itself is a
valuable means of exercising certain muscles, so is bicycling, but neither
is ideal as the _only_ form to be used. _Vary_ your exercise so as to bring
different muscles into play, take exercise that will allow free breathing
out of doors if possible, and the natural fatigue which follows will lead
you to take the rest and sleep that every normal body requires.
Exercise should always be limited by fatigue, which brings with it fatigue
poisons. This is nature's signal when to rest. If one's use of diet and air
is proper, the fatigue point will be much further off than otherwise. One
should learn to _relax_ when not in activity. The habit produces rest, even
between exertions very close together, and enables one to continue to
repeat those exertions for a much longer time than otherwise. The habit of
lying down when tired is a good one.
The Relation of Tight Clothing to Correct Breathing.--It is impossible to
breathe correctly unless the clothing is worn loosely over the chest and
abdomen. Tight corsets and tight belts prevent the walls of the chest and
the abdomen from pushing outward and interfere with the drawing of air into
the lungs. They may also result in permanent distortion of parts of the
skeleton directly under the pressure. Other organs of the body cavity, as
the stomach and intestines, may be forced downward, out of place, and in
consequence cannot perform their work properly.
Suffocation and Artificial Respiration.--Suffocation results from the
shutting off of the supply of oxygen from the lungs. It may be brought
about by an obstruction in the windpipe, by a lack of oxygen in the air,
by inhaling some other gas in quantity, or by drowning. A severe electric
shock may paralyze the nervous centers which control respiration, thus
causing a kind of suffocation. In the above cases, death often may be
prevented by prompt recourse to artificial respiration. To accomplish
this, place the patient on his back with the head lower than the body;
grasp the arms near the elbows and draw them _upward_ and _outward_ until
they are stretched above the head, on a line with the body. By this means
the chest cavity is enlarged and an inspiration produced. To produce
an expiration, carry the arms downward, and press them against the chest,
thus forcing the air out of the lungs. This exercise, regularly repeated
every few seconds, if necessary for hours, has been the source of saving
many lives.
Common Diseases of the Nose and Throat.--Catarrh is a disease to
which people with sensitive mucous membrane of the nose and throat are
subject. It is indicated by the constant secretion of mucus from these
membranes. Frequent spraying of the nose and throat with some mild
antiseptic solutions is found helpful. Chronic catarrh should be attended
to by a physician. Often we find children breathing entirely through the
mouth, the nose being seemingly stopped up. When this goes on for
some time the nose and throat should be examined by a physician for
_adenoids_, or growths of soft masses of tissue which fill up the nose cavity,
thus causing a shortage of the air supply for the body. Many a child,
backward at school, thin and irritable, has been changed to a healthy,
normal, bright scholar by the removal of adenoids. Sometimes the
tonsils at the back of the mouth cavity may become enlarged, thus shutting
off the air supply and causing the same trouble as we see in a case of
adenoids. The simple removal of the obstacle by a doctor soon cures
this condition. (See page 395.)
Organs of Excretion.--All the life processes which take place in a living
thing result ultimately, in addition to giving off of carbon dioxide, in
the formation of organic wastes within the body. The retention of these
wastes which contain nitrogen, is harmful to animals. In man, the skin and
kidneys remove this waste from the body, hence they are called the organs
of excretion.
[Illustration: Longitudinal section through a kidney.]
The Human Kidney.--The human kidney is about four inches long, two and one
half inches wide, and one inch in thickness. Its color is dark red. If the
structure of the medulla and cortex (see figure above) is examined under
the compound microscope, you will find these regions to be composed of a
vast number of tiny branched and twisted tubules. The outer end of each of
these tubules opens into the _pelvis_, the space within the kidney; the
inner end, in the cortex, forms a tiny closed sac. In each sac, the outer
wall of the tube has grown inward and carried with it a very tiny artery.
This artery breaks up into a mass of capillaries. These capillaries, in
turn, unite to form a small vein as they leave the little sac. Each of
these sacs with its contained blood vessels is called a _glomerulus_.
[Illustration: Diagram of kidney circulation, showing a glomerulus and
tubule: _a_, artery bringing blood to part; _b_, capillary bringing blood
to glomerulus; _b'_, vessel continuing with blood to vein; _c_, vein; _t_,
tubule; _G_, glomerulus.]
Wastes given off by the Blood in the Kidney.--In the glomerulus the blood
loses by osmosis, through the very thin walls of the capillaries, first, a
considerable amount of water (amounting to nearly three pints daily);
second, a nitrogenous waste material known as urea; third, salts and other
waste organic substances, uric acid among them.
These waste products, together with the water containing them, are known as
_urine_. The total amount of nitrogenous waste leaving the body each day is
about twenty grams. It is passed through the _ureter_ to the _urinary
bladder_; from this reservoir it is passed out of the body, through a tube
called the _urethra_. After the blood has passed through the glomeruli of
the kidneys it is purer than in any other place in the body, because,
before coming there, it lost a large part of its burden of carbon dioxide
in the lungs. After leaving the kidney it has lost much of its nitrogenous
waste. So dependent is the body upon the excretion of its poisonous
material that, in cases where the kidneys do not do their work properly,
death may ensue within a few hours.
[Illustration: Diagram of a section of the skin. (Highly magnified.)]
Structure and Use of Sweat Glands.--If you examine the palm of your hand
with a lens, you will notice the surface is thrown into little ridges. In
these ridges may be found a large number of very tiny pits; these are the
pores or openings of the sweat-secreting glands. From each opening a little
tube penetrates deep within the epidermis; there, coiling around upon
itself several times, it forms the sweat gland. Close around this coiled
tube are found many capillaries. From the blood in these capillaries, cells
lining the wall of the gland take water, and with it a little carbon
dioxide, urea, and some salts (common salt among others). This forms the
excretion known as _sweat_. The combined secretions from these glands
amount normally to a little over a pint during twenty-four hours. At all
times, a small amount of sweat is given off, but this is evaporated or is
absorbed by the underwear; as this passes off unnoticed, it is called
_insensible perspiration_. In hot weather or after hard manual labor the
amount of perspiration is greatly increased.
Regulation of Heat of the Body.--The bodily temperature of a person engaged
in manual labor will be found to be but little higher than the temperature
of the same person at rest. We know from our previous experiments that heat
is released. Muscles, nearly one half the weight of the body, release about
five sixths of their energy as heat. At all times they are giving up some
heat. How is it that the bodily temperature does not differ greatly at such
times? The temperature of the body is largely regulated by means of the
activity of the sweat glands. The blood carries much of the heat, liberated
in the various parts of the body by the oxidation of food, to the surface
of the body, where it is lost in the evaporation of sweat. In hot weather
the blood vessels of the skin are dilated; in cold weather they are made
smaller by the action of the nervous system. The blood thus loses water in
the skin, the water evaporates, and we are cooled off. _The object of
increased perspiration, then, is to remove heat from the body._ With a
large amount of blood present in the skin, perspiration is increased; with
a small amount, it is diminished. Hence, we have in the skin an automatic
regulator of bodily temperature.
Sweat Glands under Nervous Control.--The sweat glands, like the other
glands in the body, are under the control of the sympathetic nervous
system. Frequently the nerves dilate the blood vessels of the skin, thus
helping the sweat glands to secrete, by giving them more blood.
"Thus regulation is carried out by the nervous system
determining, on the one hand, the _loss_ by governing the
supply of blood to the skin and the action of the sweat
glands; and on the other, the _production_ by diminishing or
increasing the oxidation of the tissues."--FOSTER AND SHORE,
_Physiology_.
Colds and Fevers.--The regulation of blood passing through the blood
vessels is under control of the nervous system. If this mechanism is
interfered with in any way, the sweat glands may not do their work,
perspiration may be stopped, and the heat from oxidation held within the
body. The body temperature goes up, and a fever results.
[Illustration: _A_, blood vessels in skin normal; _B_, when congested.]
If the blood vessels in the skin are suddenly cooled when full of blood,
they contract and send the blood elsewhere. As a result a congestion or
cold may follow. Colds are, in reality, a congestion of membranes lining
certain parts of the body, as the nose, throat, windpipe, or lungs.
When suffering from a cold, it is therefore important not to chill the
skin, as a full blood supply should be kept in it and so kept from the seat
of the congestion. For this reason hot baths (which call the blood to the
skin), the avoiding of drafts (which chill the skin), and warm clothing are
useful factors in the care of colds.
Hygiene of the Skin.--The skin is of importance both as an organ of
excretion and as a regulator of bodily temperature. The skin of the entire
body should be bathed frequently so that this function of excretion may be
properly performed. Pride in one's own appearance forbids a dirty skin. For
those who can stand it, a cold sponge bath is best. Soap should be used
daily on parts exposed to dirt. Exercise in the open air is important to
all who desire a good complexion. The body should be kept at an even
temperature by the use of proper underclothing. Wool, a poor conductor of
heat, should be used in winter, and cotton, which allows of a free escape
of heat, in summer.
Cuts, Bruises, and Burns.--In case the skin is badly broken, it is
necessary to prevent the entrance and growth of bacteria. This may be done
by washing the wound with weak antiseptic solutions such as 3 per cent
_carbolic acid_, 3 per cent _lysol_, or _peroxide of hydrogen_ (full
strength). These solutions should be applied immediately. A burn or scald
should be covered at once with a paste of baking soda, with olive oil, or
with a mixture of limewater and linseed oil. These tend to lessen the pain
by keeping out the air and reducing the inflammation.
Summary of Changes in Blood within the Body.--We have already seen that red
corpuscles in the lungs lose part of their load of carbon dioxide that they
have taken from the tissues, replacing it with oxygen. This is accompanied
by a change of color from purple (in blood which is poor in oxygen) to that
of bright red (in richly oxygenated blood). Other changes take place in
other parts of the body. In the walls of the food tube, especially in the
small intestine, the blood receives its load of fluid food. In the muscles
and other working tissues the blood gives up food and oxygen, receiving
carbon dioxide and organic waste in return. In the liver, the blood gives
up its sugar, and the worn-out red corpuscles which break down are removed
(as they are in the spleen) from the circulation. In glands, it gives up
materials used by the gland cells in their manufacture of secretions. In
the kidneys, it loses water and nitrogenous wastes (_urea_). In the skin,
it also loses some waste materials, salts, and water.
"The Effect of Alcohol on Body Heat.--It is usually believed
that 'taking a drink' when cold makes one warmer. But such
is not the case. In reality alcohol lowers the temperature
of the body by dilating the blood vessels of the skin. It
does this by means of its influence on the nervous system.
It is, therefore, a mistake to drink alcoholic beverages
when one is extremely cold, because by means of this more
bodily heat is allowed to escape.
"Because alcohol is quickly oxidized, and because heat is
produced in the process, it was long believed to be of value
in maintaining the heat of the body. A different view now
prevails as the result of much observation and experiment.
Physiologists show by careful experiments that though the
temperature of the body rises during digestion of food, it
is lowered for some hours when alcohol is taken. The flush
which is felt upon the skin after a drink of wine or spirits
is due in part to an increase of heat in the body, but also
to the paralyzing effect of the alcohol upon the capillary
walls, allowing them to dilate, and so permitting more of
the warm blood of the interior of the body to reach the
surface. There it is cooled by radiation, and the general
temperature is lowered."--MACY, _Physiology_.
Effect of Alcohol on Respiration.--Alcohol tends to congest the membrane of
the throat and lungs. It does this by paralyzing the nerves which take care
of the tiny blood vessels in the walls of the air tubes and air sacs. The
capillaries become full of blood, the air spaces are lessened, and
breathing is interfered with. The use of alcohol is believed by many
physicians to predispose a person to tuberculosis. Certainly this disease
attacks drinkers more readily than those who do not drink. Alcohol
interferes with the respiration of the cells because it is oxidized very
quickly within the body as it is quickly absorbed and sent to the cells. So
rapid is this oxidation that it interferes with the oxidation of other
substances. Using alcohol has been likened to burning kerosene in a stove;
the operation is a dangerous one.
Effects of Tobacco on Respiration.--Tobacco smoke contains the same kind of
poisons as the tobacco, with other irritating substances added. It is
extremely irritating to the throat; it often causes a cough, and renders it
more liable to inflammation. If the smoke is inhaled more deeply, the
vaporized nicotine is still more readily absorbed and may thus produce
greater irritation in the bronchi and lungs. Cigarettes are worse than
other forms of tobacco, for they contain the same poisons with others in
addition.
Effect of Alcohol on the Kidneys.--It is said that alcohol is one of the
greatest causes of disease in the kidneys. The forms of disease known as
"fatty degeneration of the kidney" and "Bright's disease" are both
frequently due to this cause. The kidneys are the most important organs for
the removal of nitrogenous waste.
Alcohol unites more easily with oxygen than most other food materials,
hence it takes away oxygen that would otherwise be used in oxidizing these
foods. Imperfect oxidation of foods causes the development and retention of
poisons in the blood which it becomes the work of the kidneys to remove. If
the kidneys become overworked, disease will occur. Such disease is likely
to make itself felt as rheumatism or gout, both of which are believed to be
due to waste products (poisons) in the blood.
Poisons produced by Alcohol.--When too little oxygen enters the draft of
the stove, the wood is burned imperfectly, and there are clouds of smoke
and irritating gases. So, if oxygen unites with the alcohol and too little
reaches the cells, instead of carbon dioxide, water, and urea being formed,
there are other products, some of which are exceedingly poisonous and which
the kidneys handle with difficulty. The poisons retained in the circulation
never fail to produce their poisonous effects, as shown by headaches,
clouded brain, pain, and weakness of the body. The word "intoxication"
means "in a state of poisoning." These poisons gradually accumulate as the
alcohol takes oxygen from the cells. The worst effects come last, when the
brain is too benumbed to judge fairly of their harm.