Through the movements of the blood and the lymph, materials entering the
body are transported to the cells, and wastes formed at the cells are
carried to the organs which remove them from the body. We are now to
consider the passage of materials from outside the body to the cells and
_vice versa_. One substance which the body constantly needs is oxygen, and
one which it is constantly throwing off is carbon dioxide. Both of these
are constituents of
*The Atmosphere.*--The atmosphere, or air, completely surrounds the earth
as a kind of envelope, and comes in contact with everything upon its
surface. It is composed chiefly of oxygen and nitrogen,(29) but it also
contains a small per cent of other substances, such as water-vapor, carbon
dioxide, and argon. All of the regular constituents of the atmosphere are
gases, and these, as compared with liquids and solids, are very light.
Nevertheless the atmosphere has weight and, on this account, exerts
pressure upon everything on the earth. At the sea level, its pressure is
nearly fifteen pounds to the square inch. The atmosphere forms an
essential part of one's physical environment and serves various purposes.
The process by which gaseous materials are made to pass between the body
and the atmosphere is known as
*Respiration.*--As usually defined, respiration, or breathing, consists of
two simple processes--that of taking air into special contrivances in the
body, called the lungs, and that of expelling air from the lungs. The
first process is known as _inspiration_; the second as _expiration_. We
must, however, distinguish between respiration by the lungs, called
_external respiration_, and respiration by the cells, called _internal
respiration_.
_The purpose of respiration_ is indicated by the changes that take place
in the air while it is in the lungs. Air entering the lungs in ordinary
breathing parts with about five per cent of itself in the form of oxygen
and receives about four and one half per cent of carbon dioxide,
considerable water-vapor, and a small amount of other impurities. These
changes suggest a twofold purpose for respiration:
1. To obtain from the atmosphere the supply of oxygen needed by the body.
2. To transfer to the atmosphere certain materials (wastes) which must be
removed from the body.
The chief organs concerned in the work of respiration are
*The Lungs.*--The lungs consist of two sac-like bodies suspended in the
thoracic cavity, and occupying all the space not taken up by the heart.
They are not simple sacs, however, but are separated into numerous
divisions, as follows:
1. The lung on the right side of the thorax, called the right lung, is
made up of three divisions, or _lobes_, and the left lung is made up of
two lobes.
2. The lobes on either side are separated into smaller divisions, called
_lobules_ (Fig. 33). Each lobule receives a distinct division of an air
tube and has in itself the structure of a miniature lung.
[Fig. 33]
Fig. 33--*Lungs and air passages* seen from the front. The right lung shows
the lobes and their divisions, the lobules. The tissue of the left lung
has been dissected away to show the air tubes.
3. In the lobule the air tube divides into a number of smaller tubes, each
ending in a thin-walled sac, called an _infundibulum_. The interior of the
infundibulum is separated into many small spaces, known as the _alveoli_,
or air cells.
The lungs are remarkable for their lightness and delicacy of
structure.(30) They consist chiefly of the tissues that form their sacs,
air tubes, and blood vessels; the membranes that line their inner and
outer surfaces; and the connective tissue that binds these parts together.
All these tissues are more or less elastic. The relation of the different
parts of the lungs to each other and to the outside atmosphere will be
seen through a study of the
*Air Passages.*--The air passages consist of a system of tubes which form a
continuous passageway between the outside atmosphere and the different
divisions of the lungs. The air passes through them as it enters and
leaves the lungs, a fact which accounts for the name.
[Fig. 34]
Fig. 34--*Model of section through the head*, showing upper air passages
and other parts. 1. Left nostril. 2. Pharynx. 3. Tongue and cavity of
mouth. 4. Larynx. 5. Trachea. 6. Esophagus.
The incoming air first enters the _nostrils_. These consist of two narrow
passages lying side by side in the nose, and connecting with the pharynx
behind. The lining of the nostrils, called _mucous membrane_ is quite
thick, and has its surface much extended by reason of being spread over
some thin, scroll-shaped bones that project into the passage. This
membrane is well supplied with blood vessels and secretes a considerable
quantity of liquid. Because of the nature and arrangement of the membrane,
the nostrils are able to _warm_ and _moisten_ the incoming air, and to
_free it from dust particles_, preparing it, in this way, for entrance
into the lungs (Fig. 34).
The nostrils are separated from the mouth by a thin layer of bone, and
back of both the mouth and the nostrils is the pharynx. The _pharynx_ and
the _mouth_ serve as parts of the food canal, as well as air passages, and
are described in connection with the organs of digestion (Chapter X). Air
entering the pharynx, either by the nostrils or by the mouth, passes
through it into the _larynx_. The larynx, being the special organ for the
production of the voice, is described later (Chapter XXI). The entrance
into the larynx is guarded by a movable lid of cartilage, called the
_epiglottis_, which prevents food particles and liquids, on being
swallowed, from passing into the lower air tubes. The relations of the
nostrils, mouth, pharynx, and larynx are shown in Fig. 34.
From the larynx the air enters the _trachea_, or windpipe. This is a
straight and nearly round tube, slightly less than an inch in diameter and
about four and one half inches in length. Its walls contain from sixteen
to twenty C-shaped, cartilaginous rings, one above the other and
encircling the tube. These incomplete rings, with their openings directed
backward, are held in place by thin layers of connective and muscular
tissue. At the lower end the trachea divides into two branches, called the
bronchi, each of which closely resembles it in structure. Each _bronchus_
separates into a number of smaller divisions, called the _bronchial
tubes_, and these in turn divide into still smaller branches, known as the
_lesser bronchial tubes_ (Fig. 33). The lesser bronchial tubes, and the
branches into which they separate, are the smallest of the air tubes. One
of these joins, or expands into, each of the minute lung sacs, or
infundibula. Mucous membrane lines all of the air passages.
*General Condition of the Air Passages.*--One necessary condition for the
movement of the air into and from the lungs is an unobstructed
passageway.(31) The air passages must be kept open and free from
obstructions. They are _kept open_ by special contrivances found in their
walls, which, by supplying a degree of stiffness, cause the tubes to keep
their form. In the trachea, bronchi, and larger bronchial tubes, the
stiffness is supplied by rings of cartilage, while in the smaller tubes
this is replaced by connective and muscular tissue. The walls of the
larynx contain strips and plates of cartilage; while the nostrils and the
pharynx are kept open by their bony surroundings.
[Fig. 35]
Fig. 35--*Ciliated epithelial cells.* _A._ Two cells highly magnified. _c._
Cilia, _n._ Nucleus. _B._ Diagram of a small air tube showing the lining
of cilia.
The air passages are _kept clean_ by cells especially adapted to this
purpose, known as the _ciliated epithelial cells_. These are slender,
wedge-shaped cells which have projecting from a free end many small,
hair-like bodies, called _cilia_ (Fig. 35). They line the mucous membrane
in most of the air passages, and are so placed that the cilia project into
the tubes. Here they keep up an inward and outward wave-like movement,
which is quicker and has greater force in the _outward_ direction. By this
means the cilia are able to move small pieces of foreign matter, such as
dust particles and bits of partly dried mucus, called phlegm, to places
where they can be easily expelled from the lungs.(32)
[Fig. 36]
Fig. 36--*Terminal air sacs.* The two large sacs are infundibula; the small
divisions are alveoli. (Enlarged.)
*The Alveoli.*--The alveoli, or air cells, are the small divisions of the
infundibula (Fig. 36). They are each about one one-hundredth of an inch
(1/4 mm.) in diameter, being formed by the infolding of the infundibular
wall. This wall, which has for its framework a thin layer of elastic
connective tissue, supports a dense network of capillaries (Fig. 37), and
is lined by a single layer of cells placed edge to edge. By this
arrangement the air within the alveoli is brought very near a large
surface of blood, and the exchange of gases between the air and the blood
is made possible. It is at the alveoli that the oxygen passes from the air
into the blood, and the carbon dioxide passes from the blood into the air.
At no place in the lungs, however, do the air and the blood come in direct
contact. Their exchanges must in all cases take place through the
capillary walls and the layer of cells lining the alveoli.
[Fig. 37]
Fig. 37--*Inner lung surface (magnified)*, the blood vessels injected with
coloring matter. The small pits are alveoli, and the vessels in their
walls are chiefly capillaries.
[Fig. 38]
Fig. 38.--*Diagram to show the double movement of air and blood through the
lungs.* The blood leaves the heart by the pulmonary artery and returns by
the pulmonary veins. The air enters and leaves the lungs by the same
system of tubes.
[Fig. 39]
Fig. 39--*Diagram to show air and blood movements in a terminal air sac.*
While the air moves into and from the space within the sac, the blood
circulates through the sac walls.
*Blood Supply to the Lungs.*--To accomplish the purposes of respiration,
not only the air, but the blood also, must be passed into and from the
lungs. The chief artery conveying blood to the lungs is the _pulmonary
artery_. This starts at the right ventricle and by its branches conveys
blood to the capillaries surrounding the alveoli in all parts of the
lungs. The branches of the pulmonary artery lie alongside of, and divide
similarly to, the bronchial tubes. At the places where the finest
divisions of the air tubes enter the infundibula, the little arteries
branch into the capillaries that penetrate the infundibular walls (Figs.
38 and 39). From these capillaries the blood is conveyed by the pulmonary
veins to the left auricle.
The lungs also receive blood from two (in some individuals three) small
arteries branching from the aorta, known as the _bronchial arteries_.
These convey to the lungs blood that has already been supplied with
oxygen, passing it into the capillaries in the walls of the bronchi,
bronchial tubes, and large blood vessels, as well as the connective tissue
between the lobes of the lungs. This blood leaves the lungs partly by the
bronchial veins and partly by the pulmonary veins. No part of the body is
so well supplied with blood as the lungs.
[Fig. 40]
Fig. 40--*The pleurae.* Diagram showing the general form of the pleural sacs
as they surround the lungs and line the inner surfaces of the chest (other
parts removed). _A, A'._ Places occupied by the lungs. _B, B'._ Slight
space within the pleural sacs containing the pleural secretion, _a, a'._
Outer layer of pleura and lining of chest walls and upper surface of
diaphragm. _b, b'._ Inner layer of pleura and outer lining of lungs. _C._
Space occupied by the heart. _D._ Diaphragm.
*The Pleura.*--The pleura is a thin, smooth, elastic, and tough membrane
which covers the outside of the lungs and lines the inside of the chest
walls. The covering of each lung is continuous with the lining of the
chest wall on its respective side and forms with it a closed sac by which
the lung is surrounded, the arrangement being similar to that of the
pericardium. Properly speaking, there are two pleurae, one for each lung,
and these, besides inclosing the lungs, partition off a middle space which
is occupied by the heart (Fig. 40). They also cover the upper surface of
the diaphragm, from which they deflect upward, blending with the
pericardium. A small amount of liquid is secreted by the pleura, which
prevents friction as the surfaces glide over each other in breathing.
*The Thorax.*--The force required for breathing is supplied by the box-like
portion of the body in which the lungs are placed. This is known as the
thorax, or chest, and includes that part of the trunk between the neck and
the abdomen. The space which it incloses, known as the thoracic cavity, is
a _variable_ space and the walls surrounding this space are _air-tight._ A
framework for the thorax is supplied by the ribs which connect with the
spinal column behind and with the sternum, or breast-bone, in front. They
form joints with the spinal column, but connect with the sternum by strips
of cartilage. The ribs do not encircle the cavity in a horizontal
direction, but slope downward from the spinal column both toward the front
and toward the sides, this being necessary to the service which they
render in breathing.
*How Air is Brought into and Expelled from the Lungs.*--The principle
involved in breathing is that air flows from a place of _greater_ to a
place of _less_ pressure. The construction of the thorax and the
arrangement of the lungs within it provide for the application of this
principle in a most practical manner. The lungs are suspended from the
upper portion of the thoracic cavity, and the trachea and the upper air
passages provide the only opening to the outside atmosphere. Air entering
the thorax must on this account pass into the lungs. As the thorax is
enlarged the air in the lungs expands, and there is produced within them a
place of _slightly less_ air pressure than that of the atmosphere on the
outside of the body. This difference causes the air to flow into the
lungs.
[Fig. 41]
Fig. 41--*Diagram illustrating the bellows principle in breathing.* _A._
The human bellows. _B._ The hand bellows. Compare part for part.
When the thorax is diminished in size, the air within the lungs is
slightly compressed. This causes it to become denser and to exert on this
account a pressure _slightly greater_ than that of the atmosphere on the
outside. The air now flows out until the equality of the pressure is again
restored. Thus the thorax, by making the pressure within the lungs first
slightly less and then slightly greater than the atmospheric pressure,
causes the air to move into and out of the lungs.
Breathing is well illustrated by means of the common hand bellows, its
action being similar to that of the thorax. It will be observed that when
the sides are spread apart air flows into the bellows. When they are
pressed together the air flows out. If an air-tight sack were hung in the
bellows with its mouth attached to the projecting tube, the arrangement
would resemble closely the general plan of the breathing organs (Fig. 41).
One respect, however, in which the bellows differs from the thorax should
be noted. The thorax is never sufficiently compressed to drive out all the
air. Air is always present in the lungs. This keeps them more or less
distended and pressed against the thoracic walls.
*How the Thoracic Space is Varied.*--One means of varying the size of the
thoracic cavity is through the movements of the ribs and their resultant
effect upon the walls of the thorax. In bringing about these movements the
following muscles are employed:
1. The _scaleni_ muscles, three in number on each side, which connect at
one end with the vertebrae of the neck and at the other with the first and
second ribs. Their contraction slightly raises the upper portion of the
thorax.
2. The _elevators of the ribs_, twelve in number on each side, which are
so distributed that each single muscle is attached, at one end, to the
back portion of a rib and, at the other, to a projection of the vertebra a
few inches above. The effect of their contraction is to' elevate the
middle portion of the ribs and to turn them outward or spread them apart.
3. The _intercostal_ muscles, which form two thin layers between the ribs,
known as the _internal_ and the _external_ intercostal muscles. The
external intercostals are attached between the outer lower margin of the
rib above and the outer upper margin of the rib below, and extend
obliquely downward and forward. The internal intercostals are attached
between the inner margins of adjacent ribs, and they extend obliquely
downward and backward from the front. The contraction of the external
intercostal muscles raises the ribs, and the contraction of the internal
intercostals tends to lower them.
[Fig. 42]
Fig. 42--*Simple apparatus* for illustrating effect of movements of the
ribs upon the thoracic space; strips of cardboard held together by pins,
the front part being raised or lowered by threads moving through
attachments at 1 and 2. As the front is raised the space between the
uprights is increased. The front upright corresponds to the breastbone,
the back one to the spinal column, the connecting strips to the ribs, and
the threads to the intercostal muscles.
By slightly raising and spreading apart the ribs the thoracic space is
increased in two directions--from front to back and from side to side.
Lowering and converging the ribs has, of course, the opposite effect (Fig.
42). Except in forced expirations the ribs are lowered and converged by
their own weight and by the elastic reaction of the surrounding parts.
*The Diaphragm.*--Another means of varying the thoracic space is found in
an organ known as the diaphragm. This is the dome-shaped, _movable
partition_ which separates the thoracic cavity from the cavity of the
abdomen. The edges of the diaphragm are firmly attached to the walls of
the trunk, and the center is supported by the pericardium and the pleura.
The outer margin is muscular, but the central portion consists of a strong
sheet of connective tissue. By the contraction of its muscles the
diaphragm is pulled down, thereby increasing the thoracic cavity. By
raising the diaphragm the thoracic cavity is diminished.
The diaphragm, however, is not raised by the contraction of its own
muscles, but _is pushed up_ by the organs beneath. By the elastic reaction
of the abdominal walls (after their having been pushed out by the lowering
of the diaphragm), pressure is exerted on the organs of the abdomen and
these in turn press against the diaphragm. This crowds it into the
thoracic space. In forced expirations the muscles in the abdominal walls
contract to push up the diaphragm.
*Interchange of Gases in the Lungs.*--During each inspiration the air from
the outside fills the entire system of bronchial tubes, but the alveoli
are largely filled, at the same time, by the air which the last expiratory
effort has left in the passages. By the action of currents and eddies and
by the rapid diffusion of gas particles, the air from the outside mixes
with that in the alveoli and comes in contact with the membranous walls.
Here the oxygen, after being dissolved by the moisture in the membrane,
diffuses into the blood. The carbon dioxide, on the other hand, being in
excess in the blood, diffuses toward the air in the alveoli. The
interchange of gases at the lungs, however, is not fully understood, and
it is possible that other forces than osmosis play a part.
[Fig. 43]
Fig. 43--*Diagram* illustrating lung capacity.
*Capacity of the Lungs.*--The air which passes into and from the lungs in
ordinary breathing, called the _tidal_ air, is but a small part of the
whole amount of air which the lungs contain. Even after a forced
expiration the lungs are almost half full; the air which remains is called
the _residual_ air. The air which is expelled from the lungs by a forced
expiration, less the tidal air, is called the _reserve_, or supplemental,
air. These several quantities are easily estimated. (See Practical Work.)
In the average individual the total capacity of the lungs (with the chest
in repose) is about one gallon. In forced inspirations this capacity may
be increased about one third, the excess being known as the _complemental_
air (Fig. 43).
[Fig. 44]
Fig. 44--*Diagram* illustrating internal respiration and its dependence on
external respiration. (Modified from Hall.) (See text.)
*Internal, or Cell, Respiration.*--The oxygen which enters the blood in the
lungs leaves it in the tissues, passing through the lymph into the cells
(Fig. 44). At the same time the carbon dioxide which is being formed at
the cells passes into the blood. An exchange of gases is thus taking place
between the cells and the blood, similar to that taking place between the
blood and the air. This exchange is known as _internal_, or cell,
respiration. By internal respiration the oxygen reaches the place where it
is to serve its purpose, and the carbon dioxide begins its movement toward
the exterior of the body. This "breathing by the cells" is, therefore,
_the final and essential act of respiration_. Breathing by the lungs is
simply the means by which the taking up of oxygen and *the* giving off of
carbon dioxide by the cells is made possible.
HYGIENE OF RESPIRATORY ORGANS
The liability of the lungs to attacks from such dread diseases as
consumption and pneumonia makes questions touching their hygiene of first
importance. Consumption does not as a rule attack sound lung tissue, but
usually has its beginning in some weak or enfeebled spot in the lungs
which has lost its "power of resistance." Though consumption is not
inherited, as some suppose, lung weaknesses may be transmitted from
parents to children. This, together with the fact, now generally
recognized, that consumption is contagious, accounts for the frequent
appearance of this disease in the same family. Consumption as well as
other respiratory affections can in the majority of cases be _prevented_,
and in many cases cured, by an intelligent observation of well-known laws
of health.
*Breathe through the Nostrils.*--Pure air and plenty of it is the main
condition in the hygiene of the lungs. One necessary provision for
obtaining _pure air_ is that of breathing through the nostrils. Air is the
carrier of dust particles and not infrequently of disease germs.(33)
Partly through the small hairs in the nose, but mainly through the moist
membrane that lines the passages, the nostrils serve as filters for
removing the minute solid particles (Fig. 45). While it is important that
nose breathing be observed at all times, it is especially important when
one is surrounded by a dusty or smoky atmosphere. Otherwise the small
particles that are breathed in through the mouth may find a lodging place
in the lungs.
[Fig. 45]
Fig. 45--*Human air filter.* Diagram of a section through the nostrils;
shows projecting bones covered with moist membrane against which the air
is made to strike by the narrow passages. 1. Air passages. 2. Cavities in
the bones. 3. Front lower portion of the cranial cavity.
In addition to removing dust particles and germs, other purposes are
served by breathing through the nostrils. The warmth and moisture which
the air receives in this way, prepare it for entering the lungs. Mouth
breathing, on the other hand, looks bad and during sleep causes snoring.
The habit of nose breathing should be established early in life.(34)
*Cultivate Full Breathing.*--Many people, while apparently taking in
sufficient air to supply their need for oxygen, do not breathe deeply
enough to "freely ventilate the lungs." "Shallow breathing," as this is
called, is objectionable because it fails to keep up a healthy condition
of the entire lung surface. Portions of the lungs to which air does not
easily penetrate fail to get the fresh air and exercise which they need.
As a consequence, they become weak and, by losing their "power of
resistance," become points of attack in diseases of the lungs.(35) The
breathing of each individual should receive attention, and where from some
cause it is not sufficiently full and deep, the means should be found for
remedying the defect.
*Causes of Shallow Breathing.*--Anything that impedes the free movement of
air into the lungs tends to cause shallow breathing A drooping of the back
or shoulders and a curved condition of the spinal column, such as is
caused by an improper position in sitting, interfere with the free
movements of the ribs and are recognized causes. Clothing also may impede
the respiratory movements and lead to shallow breathing. If too tight
around the chest, clothing interferes with the elevation of the ribs; and
if too tight around the waist, it prevents the depression of the
diaphragm. Other causes of shallow breathing are found in the absence of
vigorous exercise, in the leading of an indoor and inactive life, in
obstructions in the nostrils and upper pharynx, and in the lack of
attention to proper methods of breathing.
To prevent shallow breathing one should have the habit of sitting and
standing erect. The clothing must not be allowed to interfere with the
respiratory movements. The taking of exercise sufficiently vigorous to
cause deep and rapid breathing should be a common practice and one should
spend considerable time out of doors. If one has a flat chest or round
shoulders, he should strive by suitable exercises to overcome these
defects. Obstructions in the nostrils or pharynx should be removed.
*Breathing Exercises.*--In overcoming the habit of shallow breathing and in
strengthening the lungs generally, the practicing of occasional deep
breathing has been found most valuable and is widely recommended. With the
hands on the hips, the shoulders drawn back and _down_, the chest pushed
upward and forward, and the chin slightly depressed, draw the air slowly
through the nostrils until the lungs are _completely_ full. After holding
this long enough to count three slowly, expel it quickly from the lungs.
Avoid straining. To get the benefit of pure air, it is generally better to
practice deep breathing out of doors or before an open window.
By combining deep breathing with simple exercises of the arms, shoulders,
and trunk much may be done towards straightening the spine, squaring the
shoulders, and overcoming flatness of the chest. Though such movements are
best carried on by the aid of a physical director, one can do much to help
himself. One may safely proceed on the principle that slight deformities
of the chest, spine, and shoulders are corrected by gaining and keeping
the natural positions, and may employ any movements which will loosen up
the parts and bring them where they naturally belong.(36)
*Serious Nature of Colds.*--That many cases of consumption have their
beginning in severe colds (on the lungs) is not only a matter of popular
belief, but the judgment also of physicians. Though the cold is a
different affection from that of consumption, it may so lower the vitality
of the body and weaken the lung surfaces that the germs of consumption
find it easy to get a start. On this account a cold on the chest which
does not disappear in a few days, but which persists, causing more or less
coughing and pain in the lungs, must be given serious consideration.(37)
The usual home remedies failing to give relief, a physician should be
consulted. It should also be noted that certain diseases of a serious
nature (pneumonia, diphtheria, measles, etc.) have in their beginning the
appearance of colds. On this account it is wise not only to call a
physician, but to call him early, in severe attacks of the lungs.
Especially if the attack be attended by difficult breathing, fever, and a
rapid pulse is the case serious and medical advice necessary.
*Ventilation.*--The process by which the air in a room is kept fresh and
pure is known as ventilation. It is a double process--that of bringing
fresh air into the room and that of getting rid of air that has been
rendered impure by breathing (38) or by lamps. Outdoor air is usually of a
different temperature (colder in winter, warmer in summer) from that
indoors, and as a consequence differs from it slightly in weight. On
account of this difference, suitable openings in the walls of buildings
induce currents which pass between the rooms and the outside atmosphere
even when there is no wind. In winter care must be taken to prevent drafts
and to avoid too great a loss of heat from the room. A cold draft may even
cause more harm to one in delicate health than the breathing of air which
is impure. To ventilate a room successfully the problem of preventing
drafts must be considered along with that of admitting the fresh air.
[Fig. 46]
Fig. 46--Window adjusted for ventilation without drafts.
The method of ventilation must also be adapted to the construction of the
building, the plan of heating, and the condition of the weather. Specific
directions cannot be given, but the following suggestions will be found
helpful in ventilating rooms where the air is not warmed before being
admitted:
1. _Introduce, the air through many small openings_ rather than a few
large ones. If the windows are used for this purpose, raise the lower sash
and drop the upper one _slightly_ for _several_ windows, varying the width
to suit the conditions (Fig. 46). By this means sufficient air may be
introduced without causing drafts.
2. _Introduce the air at the warmest portions of the room._ The air
should, if possible, be warmed before reaching the occupants.
3. If the wind is blowing, _ventilate principally on the sheltered side of
the house_.
Ample provision should be made for fresh air in sleeping rooms, and here
again drafts must be avoided. Especially should the bed be so placed that
strong air currents do not pass over the sleeper. In schoolhouses and
halls for public gatherings the means for efficient ventilation should, if
possible, be provided in the general plan of construction and method of
heating.
[Fig. 47]
Fig. 47--*Artificial respiration* as a laboratory experiment. Expiration.
Prone-posture method of Schaffer.
*Artificial Respiration.*--When natural breathing is temporarily suspended,
as in partial drowning, or when one has been overcome by breathing some
poisonous gas, the saving of life often depends upon the prompt
application of artificial respiration. This is accomplished by alternately
compressing and enlarging the thorax by means of variable pressure on the
outside, imitating the natural process as nearly as possible. Following is
the method proposed by Professor E.A. Schaffer of England, and called by
him "the _prone-posture_ method of artificial respiration":
The patient is laid face downward with an arm bent under the head, and
_intermittent_ pressure applied vertically over the shortest ribs. The
pressure drives the air from the lungs, both by compressing the lower
portions of the chest and by forcing the abdominal contents against the
diaphragm, while the elastic reaction of the parts causes fresh air to
enter (Figs. 47 and 48). "The operator kneels or squats by the side of, or
across the patient, places his hands over the lowest ribs and swings his
body backward and forward so as to allow his weight to fall vertically on
the wrists and then to be removed; in this way hardly any muscular
exertion is required.... The pressure is applied gradually and slowly,
occupying some three seconds; it is then withdrawn during two seconds and
again applied; and so on some twelve times per minute."(39)
[Fig. 48]
Fig. 48--Artificial respiration. Inspiration.
The special advantages of the prone-posture method over others that have
been employed are: I. It may be applied by a single individual and fora
long period of time without exhaustion. 2. It allows the mucus and water
(in case of drowning) to run out of the mouth, and causes the tongue to
fall forward so as not to obstruct the passageway. 3. It brings a
sufficient amount of air into the lungs.(40)
While applying artificial respiration, the heat of the body should not be
allowed to escape any more than can possibly be helped. In case of
drowning, the patient should be wrapped in dry blankets or clothing, while
bottles of hot water may be placed in contact with the body. The
circulation should be stimulated, as may be done by rubbing the hands,
feet, or limbs in the direction of the flow of the blood in the veins.
*Tobacco Smoke and the Air* Passages.--Smoke consists of minute particles
of unburnt carbon, or soot, such as collect in the chimneys of fireplaces
and furnaces. If much smoke is taken into the lungs, it irritates the
delicate linings and tends to clog them up. Tobacco smoke also contains
the poison nicotine, which is absorbed into the blood. For these reasons
the cigarette user who inhales the smoke does himself great harm, injuring
his nervous system and laying the foundation for diseases of the air
passages. The practice of smoking indoors is likewise objectionable, since
every one in a room containing the smoke is compelled to breathe it.
*Alcohol and Diseases of the Lungs.*--Pneumonia is a serious disease of the
lungs caused by germs. The attacks occur as a result of exposure,
especially when the body is in a weakened condition. A noted authority
states that "alcoholism is perhaps the most potent predisposing cause" of
pneumonia.(41) A person addicted to the use of alcohol is also less likely
to recover from the disease than one who has avoided its use, a result due
in part to the weakening effect of alcohol upon the heart. The congestion
of the lungs in pneumonia makes it very difficult for the heart to force
the blood through them. The weakened heart of the drunkard gives way under
the task.
The statement sometimes made that alcohol is beneficial in pulmonary
tuberculosis is without foundation in fact. On the other hand, alcoholism
is a recognized cause of consumption. Some authorities claim that this
disease is more frequent in heavy drinkers than in those of temperate
habits, in the proportion of about three to one, and that possibly half of
the cases of tuberculosis are traceable to alcoholism.(42)
*The Outdoor Cure for Lung Diseases*--Among the many remedies proposed for
consumption and kindred diseases, none have proved more beneficial,
according to reports, than the so-called "outdoor" cure. The person having
consumption is fed plentifully upon the most nourishing food, and is made
to spend practically his entire time, including the sleeping hours, _out
of doors_. Not only is this done during the pleasant months of summer, but
also during the winter when the temperature is below freezing. Severe
exposure is prevented by overhead protection at night and by sufficient
clothing to keep the body warm. The abundant supply of pure, cold air
toughens the lungs and invigorates the entire body, thereby enabling it to
throw off the disease.
The success attending this method of treating consumptives suggests the
proper mode of strengthening lungs that are not diseased, but simply weak.
The person having weak lungs should spend as much time as he conveniently
can out of doors. He should provide the most ample ventilation at night
and have a sleeping room to himself. He should practice deep breathing
exercises and partake of a nourishing diet. While avoiding prolonged
chilling and other conditions liable to induce colds, he should take
advantage of every opportunity of exposing himself fully and freely to the
outside atmosphere.
*Summary.*--The purpose of respiration is to bring about an exchange of
gases between the body and the atmosphere. The organs employed for this
purpose, called the respiratory organs, are adapted to handling materials
in the _gaseous_ state, and are operated in accordance with principles
governing the movements of the atmosphere. By alternately increasing and
diminishing the thoracic space, air is made to pass between the outside
atmosphere and the interior of the lungs. Finding its way into the
smallest divisions of the lungs, called the alveoli, the air comes very
near a large surface of blood. By this means the carbon dioxide diffuses
out of the blood, and the free oxygen enters. Through the combined action
of the organs of respiration and the organs that move the blood and the
lymph, the cells in all parts of the body are enabled to exchange certain
gaseous materials with the outside atmosphere.
[Fig. 49]
Fig. 49--Model for demonstrating the lungs.
*Exercises.--*1. How does air entering the lungs differ in composition from
air leaving the lungs? What purposes of respiration are indicated by these
differences?
2. Name the divisions of the lungs.
3. Trace air from the outside atmosphere into the alveoli. Trace the blood
from the right ventricle to the alveoli and back again to the left
auricle.
4. How does the movement of air into and from the lungs differ from that
of the blood through the lungs with respect to (_a_) the direction of the
motion. (_b_) the causes of the motion, and (_c_) the tubes through which
the motion takes place?
5. How are the air passages kept clean and open?
6. Describe the pleura. Into what divisions does it separate the thoracic
cavity?
7. Describe and name uses of the diaphragm.
8. If 30 cubic inches of air are passed into the lungs at each inspiration
and .05 of this is retained as oxygen, calculate the number of cubic feet
of oxygen consumed each day, if the number of inspirations be 18 per
minute.
9. Find the _weight_ of a day's supply of oxygen, as found in the above
problem, allowing 1.3 ounces as the weight of a cubic foot.
10. Make a study of the hygienic ventilation of the schoolroom.
11. Give advantages of full breathing over shallow breathing.
12. How may a flat chest and round shoulders be a cause of consumption?
How may these deformities be corrected?
13. Give general directions for applying artificial respiration.
PRACTICAL WORK
Examine a dissectible model of the chest and its contents (Fig. 49). Note
the relative size of the two lungs and their position with reference to
the heart and diaphragm. Compare the side to side and vertical diameters
of the cavity. Trace the air tubes from the trachea to their smallest
divisions.
*Observation of Lungs* (Optional).--Secure from a butcher the lungs of a
sheep, calf, or hog. The windpipe and heart should be left attached and
the specimen kept in a moist condition until used. Demonstrate the
trachea, bronchi, and the bronchial tubes, and the general arrangement of
pulmonary arteries and veins. Examine the pleura and show lightness of
lung tissue by floating a piece on water.
*To show the Changes that Air undergoes in the Lungs.*--1. Fill a quart jar
even full of water. Place a piece of cardboard over its mouth and invert,
without spilling, in a pan of water. Inserting a tube under the jar, blow
into it air that has been held as long as possible in the lungs. When
filled with air, remove the jar from the pan, keeping the top well
covered. Slipping the cover slightly to one side, insert a burning
splinter and observe that the flame is extinguished. This proves the
absence of sufficient oxygen to support combustion. Pour in a little
limewater(43) and shake to mix with the air. The change of the limewater
to a milky white color proves the presence of carbon dioxide.
[Fig. 50]
Fig. 50--*Apparatus* for showing changes which air undergoes while in the
lungs.
2. The effects illustrated in experiment 1 may be shown in a somewhat more
striking manner as follows: Fill two bottles of the same size each one
fourth full of limewater and fit each with a two-holed rubber stopper
(Fig. 50). Fit into each stopper one short and one long glass tube, the
long tube extending below the limewater. Connect the short tube of one
bottle and the long tube of the other bottle with a Y-tube. Now breathe
slowly three or four times through the Y-tube. It will be found that the
inspired air passes through one bottle and the expired air through the
other. Compare the effect upon the limewater in the two bottles. Insert a
small burning splinter into the top of each bottle and note result. What
differences between inspired and expired air are thus shown?
3. Blow the breath against a cold window pane. Note and account for the
collection of moisture.
4. Note the temperature of the room as shown by a thermometer. Now breathe
several times upon the bulb, noting the rise in the mercury. What does
this experiment show the body to be losing through the breath?
*To show Changes in the Thoracic Cavity.*--1. To a yard- or meter-stick,
attach two vertical strips, each about eight inches long, as shown in Fig.
51. The piece at the end should be secured firmly in place by screws or
nails. The other should be movable. With this contrivance measure the
sideward and forward expansion of a boy's thorax. Take the diameter first
during a complete inspiration and then during a complete expiration,
reading the difference. Compare the forward with the sideward expansion.
[Fig. 51]
Fig. 51--*Apparatus* for measuring chest expansion.
2. With a tape-line take the circumference of the chest when all the air
possible has been expelled from the lungs. Take it again when the lungs
have been fully inflated. The difference is now read as the chest
expansion.
[Fig. 52]
Fig. 52--*Simple apparatus* for illustrating the action of the diaphragm.
*To illustrate the Action of the Diaphragm.*--Remove the bottom from a
large bottle having a small neck. (Scratch a deep mark with a file and
hold on the end of this mark a hot poker. When the glass cracks, lead the
crack around the bottle by heating about one half inch in advance of it.)
Place the bottle in a large glass jar filled two thirds full of water
(Fig. 52). Let the space above the water represent the chest cavity and
the water surface represent the diaphragm. Raise the bottle, noting that
the water falls, thereby increasing the space and causing air to enter.
Then lower the bottle, noting the opposite effect. To show the movement of
the air in and out of the bottle, hold with the hand (or arrange a support
for) a burning splinter over the mouth of the bottle.
*To estimate the Capacity of the Lungs.*--Breathing as naturally as
possible, expel the air into a spirometer (lung tester) during a period,
say of ten respirations (Fig. 53). Note the total amount of air exhaled
and the number of "breaths" and calculate the amount of air exhaled at
each breath. This is called the _tidal_ air.
[Fig. 53]
Fig. 53--*Apparatus* (spirometer) for measuring the capacity of the lungs.
2. After an ordinary inspiration empty the lungs as completely as possible
into the spirometer, noting the quantity exhaled. This amount, less the
tidal air, is known as the _reserve_ air. The air which is now left in the
lungs is called the _residual_ air. On the theory that this is equal in
amount to the reserve air, calculate the capacity of the lungs in an
ordinary inspiration.
3. Now fill the lungs to the full expansion of the chest and empty them as
completely as possible into the spirometer, noting the amount expelled.
This, less the tidal air and the reserve air, is called the _complemental_
air. Now calculate the total capacity of the lungs.