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Hygienic Physiology

J >> Joel Dorman Steele >> Hygienic Physiology




If we laugh or talk when we swallow, our food is apt to "go the wrong
way," _i. e._, little particles pass into the larynx, and the
tickling sensation which they produce forces us to cough in order to expel
the intruders.

2. _The Vocal Cords_.--On each side of the _glottis_ are the so-
called _vocal cords_. They are not really cords, but merely elastic
membranes projecting from the sides of the box across the opening.
[Footnote: The cartilages and vocal cords may be readily seen in the
larynx of an ox or sheep. If the flesh be cut off, the cartilages will
dry, and will keep for years.] When not in use, they spread apart and
leave a V-shaped orifice (Fig. 28), through which the air passes to and
from the lungs. If the cords are tightened, the edges approach sometimes
within 1/100 of an inch of each other, and, being thrown into vibration,
cause corresponding vibrations in the current of air. Thus sound is
produced in the same manner as by the vibrations of the tongues of an
accordion, or the strings of a violin, only in this case the strings are
scarcely an inch long.

FIG. 27.

[Illustration: _Passage to the Œsophagus and Windpipe._ c, _the
tongue;_ d, _the soft palate, ending in_ g, _the uvula;_ h,
_the epiglottis;_ i, _the glottis;_ I, _the œsophagus;_ f,
_the pharynx._]

DIFFERENT TONES OF THE VOICE.--The higher tones of the voice are produced
when the cords are short, tight, and closely in contact; the lower, by the
opposite conditions. Loudness is regulated by the quantity of air and
force of expulsion. A falsetto voice is thought to be the result of a
peculiarity in the pharynx (Fig. 27) at the back part of the nose; it is
more probably produced by some muscular maneuver not yet fully understood.
When boys are about fourteen years of age, the larynx enlarges, and the
cords grow proportionately longer and coarser; hence, the voice becomes
deeper, or, as we say, "changes." The peculiar harshness of the voice at
this time seems to be due to a congestion of the mucous membrane of the
cords. The change may occur very suddenly, the voice breaking in a single
night.

FIG. 28.

[Illustration: e, e, _the vocal cords;_ d, _the epiglottis._]

Speech is voice modulated by the lips, tongue, [Footnote: The tongue is
styled the "unruly member," and held responsible for all the tattling of
the world; but when the tongue is removed, the adjacent organs in some way
largely supply the deficiency, so that speech is still possible. Huxley
describes the conversation of a man who had two and one half inches of his
tongue preserved in spirits, and yet could converse intelligibly. Only the
two letters _t_ and _d_ were beyond his power; the articulation
of these involves the employment of the tip of the tongue; hence, "tin" he
converted into "fin," and "dog" into "thog."] palate, and teeth.
[Footnote: An artificial larynx may be made by using elastic bands to
represent the vocal cords, and by placing above them chambers which by
their resonance will produce the same effect as the cavities lying above
the larynx. An artificial speaking machine was constructed by Kempelen,
which could pronounce such sentences as, "I love you with all my heart,"
in different languages, by simply touching the proper keys.] Speech and
voice are commonly associated, but speech may exist without the voice, for
when we whisper we articulate the words, although there is no
vocalization, _i. e._, no action of the larynx. [Footnote: We can
observe this by placing the hand on the throat, and noticing the absence
of vibrations when we whisper, and their presence when we talk. The
difference between vocalization and non-vocalization is seen in a sigh and
a groan, the latter being the former vocalized. Whistling is a pure mouth
sound, and does not depend on the voice. Laughter is vocal, being the
aspirated vowels, a, e, or o, convulsively repeated.] (See p. 297.)

FIG. 29.

[Illustration: _The Lungs, showing the Larynx._ A, _the
windpipe;_ B, _the bronchial tubes._]

FORMATION OF VOCAL SOUNDS.--The method of modulating voice into speech may
be seen by producing the pure vowel sounds _a, e_, etc., from one
expiration, the mouth being kept open while the form of the aperture is
changed for each vowel by the tongue and the lips. _H_ is only an
explosion, or forcible throwing of a vowel sound from the mouth.
[Footnote: When, in sounding a vowel, the sound coincides with a sudden
change in the position of the vocal cords from one of divergence to one of
approximation, the vowel is pronounced with the _spiritus asper_.
When the vocal cords are brought together before the blast of air begins,
the vowel is pronounced with the _spiritus lenis._--FOSTER.]

The consonants, or short sounds, may also be made without interrupting the
current of air, by various modifications of the vocal organs. In sounding
singly any one of the letters, we can detect its peculiar requirements.
Thus _m_ and _n_ can be made only by blocking the air in the
mouth and sending it through the nose; _l_ lets the air escape at the
sides of the tongue; _r_ needs a vibratory movement of the tongue;
_b_ and _p_ stop the breath at the lips; _k_ and _g_ (hard), at the
back of the palate. Consonants like _b_ and _d_ are abrupt, or, like
_l_ and _s_, continuous. Those made by the lips are termed _labials_;
those by pressing the tongue against the teeth, _dentals_; those by the
tongue, _linguals_.

The child gains speech slowly, first learning to pronounce the vowel
_a_, the consonants _b, m_, and _p_, and then their unions --_ba, ma, pa_.

DESCRIPTION OF THE ORGANS OF RESPIRATION.--Beneath the larynx is the
windpipe, or _trachea_ (see Fig. 29), so called because of its
roughness. It is strengthened by C-shaped cartilages with the openings
behind, where they are attached to the œsophagus. At the lower end, the
trachea divides into two branches, called the right and left
_bronchi_. These subdivide in the small bronchial tubes, which ramify
through the lungs like the branches of a tree, the tiny twigs of which at
last end in clusters of cells so small that there are six hundred million
in all. This cellular structure renders the lungs exceedingly soft,
elastic, and sponge-like. [Footnote: The lungs of slaughtered animals are
vulgarly called "lights," probably on account of their lightness. They are
similar in structure to those of man. They will float on water, and if a
small piece be forcibly squeezed between the fingers (notice the creaking
sound it gives), it will retain sufficient air to make it buoyant.]

FIG. 30.

[Illustration: _Bronchial Tubes, with clusters of cells._]

The stiff, cartilaginous rings, so noticeable in the rough surface of the
trachea and the bronchi, disappear as we reach the smaller bronchial
tubes, so that while the former are kept constantly open for the free
admission of air, the latter are provided with elastic fibers by which
they may be almost closed.

WRAPPING OF THE LUNGS.--The lungs are invested with a double covering--the
_pleura_--one layer being attached to the lungs and the other to the
walls of the chest. It secretes a fluid which lubricates it, so that the
layers glide upon each other with perfect ease. [Footnote: These pleural
sacs are distinct and closed; hence, when the ribs are raised, a partial
vacuum being formed in the sacs, air rushes in, and distends the pulmonary
lobules.] The lungs are lined with mucous membrane, exceedingly delicate
and sensitive to the presence of anything except pure air. We have all
noticed this when we have breathed any thing offensive.

FIG. 31.

[Illustration: A, _the heart;_ B, _the lungs drawn aside to show
the internal organs;_ C, _the diaphragm;_ D, _the liver;_ E,
_the gall cyst;_ F, _the stomach;_ G,_ the small intestines;_ H,
_the transverse colon._]

THE CILIA.--Along the air passages are minute filaments (_cilia_,
Fig. 32), which are in constant motion, like a field of grain stirred by a
gentle breeze. They serve to fan the air in the lungs, and produce an
outward current, which is useful in catching dust and fine particles swept
inward with the breath.

HOW WE BREATHE.--Respiration consists of two acts--taking in the air, or
_inspiration_, and expelling the air, or _expiration_.

FIG. 32.

[Illustration: B, _a section of the mucous membrane, showing the cilia
rising from the peculiar epithelial cells on the outside of the mucous
membrane lining the tubes;_ A, _a single cell more highly
magnified._]

1. _Inspiration_.--When we draw in a full breath, we straighten the
spine and throw the head and shoulders back, so as to give the greatest
advantage to the muscles. [Footnote: If we examine the bony cage of the
thorax or chest in Fig. 8, we shall see that the position of the ribs may
alter its capacity in two ways.

1. As they run obliquely downward from the spine, if the sternum or
breastbone be lifted in front, the diameter of the chest will be
increased.

2. The ribs are fastened by elastic cartilages, which stretch as the
muscles that lift the ribs contract, and so increase the breadth of the
chest.]

At the same time, the diaphragm [Footnote: The diaphragm is the muscular
partition between the chest and the abdomen. It is always convex toward
the former, and concave toward the latter (Fig. 31). Long muscular fibers
extend from its center toward the ribs in front and the spine at the back.
When these contract, they depress and flatten the diaphragm; when they
relax, it becomes convex again. In the former case, the bowels are pressed
downward and the abdomen pushed outward; in the latter, the bowels spring
upward, and the abdomen is drawn inward.] descends and presses the walls
of the abdomen outward. Both these processes increase the size of the
chest. Thereupon, the elastic lungs expand to occupy the extra space,
while the air, rushing in through the windpipe, pours along the bronchial
tubes and crowds into every cell. [Footnote: It is said that in drawing a
full breath, the muscles exert a force equal to raising a weight of seven
hundred and fifty pounds. When we are about to make a great effort, as in
striking a heavy blow, we naturally take a deep inspiration, and shut the
glottis. The confined air makes the chest tense and firm, and enables us
to exert a greater force. As we let slip the blow, the glottis opens and
the air escapes, often with a curious aspirated sound as is noticeable in
workmen. To make a good shot with a rifle, we should take aim with a full
chest and tight breath, since then the arms will have a steadier support.]

2. _Expiration_.--When we forcibly expel the air from our lungs, the
operation is reversed. We bend forward, draw in the walls of the abdomen,
and press the diaphragm upward, while the ribs are pulled downward,--all
together diminishing the size of the chest, and forcing the air outward.

Ordinary, quiet breathing is performed mainly by the diaphragm,--one
breath to every four beats of the heart, or eighteen per minute. (See p.
299.)

MODIFICATIONS OF THE BREATH.--_Sighing_ is merely a prolonged
inspiration followed by an audible expiration. _Coughing_ is a
violent expiration in which the air is driven through the mouth.
_Sneezing_ differs from coughing, the air being forced through the
nose. _Snoring_ is produced by the passage of the breath through the
pharynx when the tongue and soft palate are in certain positions.
[Footnote: The soft palate must have fallen back in such a manner as
nearly or quite to close the entrance to the nasal cavity from the throat,
and the tongue must also be thrown back so far as to leave only a narrow
opening between it and the soft palate. The noise is produced by the air
being forced either inward or outward through this opening. A snore
results also when, with a closed mouth, the air is forced between the soft
palate and the back wall of the pharynx into the nasal cavity. With deep
breathing, perhaps accompanied by a variation in the position of the soft
palate, a rattling noise may be heard in addition to the snoring, which is
due to a vibration of the soft palate.--F. A. FERNALD, in "How we Sneeze,
Laugh, Stammer, and Sigh."--_Popular Science Monthly_, Feb., 1884.]
_Laughing_ and _crying_ are very much alike. The expression of
the face is necessary to distinguish between them. The sounds are produced
by short, rapid contractions of the diaphragm. _Hiccough_ is confined
to inspiration. It is caused by a contraction of the diaphragm and a
constriction of the glottis; the current of air just entering, as it
strikes the closed glottis, gives rise to the well-known sound.
_Yawning_, or _gaping_, is like sighing. [Footnote: The
usefulness of a yawn lies in bringing up the arrears, as it were, of
respiration, when it has fallen behindhand, either through fatigue or
close attention to other occupation. The stretching of the jaws and limbs
may also serve to equalize the nervous influence, certain muscles having
become uneasy on account of being stretched or contracted for a long
time.] It is distinguished by a wide opening of the mouth and a deep,
profound inspiration. Both processes furnish additional air, and therefore
probably meet a demand of the system for more oxygen. Frequently, however,
they are like laughing, sobbing, etc., merely a sort of contagion, which
runs through an audience, and seems almost irresistible.

THE CAPACITY OF THE LUNGS.--If we take a deep inspiration, and then
forcibly exhale all the air we can expel from the lungs, this amount,
which is termed the _breathing capacity_, will bear a very close
correspondence to our stature. For a man of medium height (five feet eight
inches) it will be about two hundred and thirty cubic inches, [Footnote:
Of this amount, one hundred cubic inches can be forced in only by an extra
effort, and is available for emergencies, or for purposes of training, as
in singing, climbing, etc. It is of great importance, since, if the
capacity of the lungs only equaled our daily wants, the least obstruction
would prove fatal.] or a gallon, and for each inch of height between five
and six feet there will be an increase of eight cubic inches. In addition,
it is found that the lungs contain about one hundred cubic inches which
can not be expelled, thus making their entire contents about three hundred
and thirty cubic inches, or eleven pints. The extra amount always on hand
in the lungs is of great value, since thereby the action of the air goes
on continuously, even during a violent expiration. In ordinary breathing,
only about twenty or thirty cubic inches (less than a pint) of air pass in
and out.

THE NEED OF AIR.--The body needs food, clothing, sunshine, bathing, and.
drink; but none of these wants is so pressing as that for air. The other
demands may be met by occasional supplies, but air must be furnished every
moment or we die. Now the vital element of the atmosphere is oxygen gas.
[Footnote: See "Steele's Popular Chemistry," p. 30. The atmosphere
consists of one fifth oxygen and four fifths nitrogen. The former is the
active element; and the latter, the passive. Oxygen alone would be too
stimulating, and must be restrained by the neutral nitrogen. Separately,
either element of the air would kill us.] This is a stimulating, life-
giving principle. No tonic will so invigorate as a few full, deep breaths
of cold, pure air. Every organ will glow with the energy of the fiery
oxygen.

ACTION OF THE AIR IN THE LUNGS.--In the delicate cells of the lungs, the
air gives up its oxygen to the blood, and receives in turn carbonic-acid
[Footnote: More properly _Carbon dioxide_.] gas and water, foul with
waste matter which the blood has picked up in its circulation through the
body. The blood, thus purified and laden with the inspiring oxygen, goes
bounding through the system, while the air we exhale carries off the
impurities. In this process, the blood changes from purple to red. If we
examine our breath, we can readily see what it has removed from the blood.

TESTS OF THE BREATH.--1. Breathe into a jar, and on lowering into it a
lighted candle, the flame will be instantly extinguished; thus indicating
the presence of carbonic-acid gas. 2. Breathe upon a mirror, and a film of
moisture will show the vapor. [Footnote: There is a close relation between
the functions of the skin, the lungs, and the kidneys--the scavengers of
the body. They all carry off water from the blood, and when the function
of one of the three is, in this respect, interfered with, the others are
called upon to perform its functions. When the function of perspiration is
deranged, the lungs and kidneys are required to perform heavier duty, and
this may lead to disease (see p. 62).] 3. If breath be confined in a
bottle, the animal matter will decompose and give off an offensive odor.

ANALYSIS OF THE EXPIRED AIR shows that it has lost about twenty-five per
cent of its oxygen, and gained an equal amount of carbonic-acid gas,
besides moisture, and organic impurities. Our breath, then, is air robbed
of its vitality, and containing in its place a gas as fatal to life
[Footnote: Carbonic-acid gas can not be breathed when undiluted, as the
glottis closes and forbids its passage into the lungs. Air containing only
three or four per cent acts as a narcotic poison (MILLER), and a much
smaller proportion will have an injurious effect. The great danger,
however, lies in the organic particles constantly exhaled from the lungs
and the skin, which, it is believed, are often direct and active poisons.]
as it is to a flame, and effete matter which is disagreeable to the smell,
injurious to the health, and which may contain the germs of serious
disease.

THE EVIL EFFECT OF REBREATHING the air can not be overestimated. We take
back into our bodies that which has just been rejected. The blood
thereupon leaves the lungs, bearing, not the invigorating oxygen, but
refuse matter to obstruct the whole system. We soon feel the effect. The
muscles become inactive. The blood stagnates. The heart acts slowly. The
food is undigested. The brain is clogged. The head aches. Instances of
fatal results are only too frequent. [Footnote: During the English war in
India, in the eighteenth century, one hundred and forty-six prisoners were
shut up in a room scarcely large enough to hold them. The air could enter
only by two narrow windows. At the end of eight hours, but twenty-three
persons remained alive, and these were in a most deplorable condition.
This prison is well called "The Black Hole of Calcutta."--Percy relates
that after the battle of Austerlitz, three hundred Russian prisoners were
confined in a cavern, where two hundred and sixty of them perished in a
few hours.--The stupid captain of the ship _Londonderry_, during a
storm at sea, shut the hatches. There were only seven cubic feet of space
left for each person, and in six hours ninety of the passengers were
dead.] The constant breathing of even the slightly impure air of our
houses can not but tend to undermine the health. The blood is not
purified, and is thus in a condition to receive the seeds of disease at
any time. The system uninspired by the energizing oxygen is sensitive to
cold. The pale cheek, the lusterless eye, the languid step, speak but too
plainly of oxygen starvation. In such a soil, catarrh, scrofula, and
kindred diseases run riot. [Footnote: One not very strong, or unable
powerfully to resist conditions unfavorable to health, and with a
predisposition to lung disease, will be sure, sooner or later, by partial
lung starvation and blood poisoning, to develop pulmonary consumption.
_The lack of what is so abundant and so cheap--good, pure air--is
unquestionably the one great cause of this terrible disease_.--BLACK'S
_Ten Laws of Health_.]

CONCERNING THE NEED FOR VENTILATION.--The foul air which passes off from
the lungs and through the pores of the skin does not fall to the floor,
but diffuses itself through the surrounding atmosphere. A single breath
will to a trifling but certain extent taint the air of a whole room.
[Footnote: This grows out of a well-known philosophical principle called
the Diffusion of Gases, whereby two gases tend to mix in exact
proportions, no matter what may be the quantity of each.--STEELE'S
_Popular Chemistry,_ p. 86, and _Popular Physics,_ p. 52.] A
light will vitiate as much air as a dozen persons. Many breaths and lights
therefore rapidly unfit the air for our use.

The perfection of ventilation is reached when the air of a room is as pure
as that out of doors. To accomplish this result, it is necessary to allow
for each person six hundred cubic feet of space, while ventilation is
still going on in the best manner known.

In spite of these well-known facts, scarcely any pains are taken to supply
fresh air, while the doors and windows where the life-giving oxygen might
creep in are hermetically stopped.

How often is this true of the sick room. Yet here the danger of bad air is
intensified. The expired breath of the patient is peculiarly threatening
to himself as well as to others. Nature is seeking to throw off the poison
of the disease. The scavengers of the body are all at work. The breath and
the insensible perspiration are loaded with impurities. [Footnote: The
floating dust in the air, revealed to us by the sunbeam shining through a
crack in the blinds, shows the abundance of these impurities, and also the
presence of germs which, lodging in the lungs, may implant disease, unless
thrown off by a vigorous constitution. "On uncovering a scarlet fever
patient, a cloud of fine dust is seen to rise from the body--contagious
dust, that for days will retain its poisonous properties."--YOUMANS. (See
p. 300.)] The odor is oftentimes exceedingly offensive. Sick and well
alike need an abundance of fresh air. But, too often, it is the only want
not supplied.

Our sitting rooms, heated by furnaces or red-hot stoves, generally have no
means of ventilation, or, if provided, they are seldom used. A window is
occasionally dropped to give a little relief, as if pure air were a
rarity, and must be doled out to the suffering lungs in morsels, instead
of full and constant draughts. The inmates are starved by scanty lung
food, and stupefied by foul air. The process goes on year by year. The
weakened and poisoned body at last succumbs to disease, while we, in our
blindness and ignorance, talk of the mysterious Providence which thus
untimely cuts down the brightest intellects. The truth is, death is often
simply the penalty for violating nature's laws. Bad air begets disease;
disease begets death.

In our churches, the foul air left by the congregation on Sunday is shut
up during the week, and heated for the next Lord's day, when the people
assemble to rebreathe the polluted atmosphere. They are thus forced, with
every breath they take, to violate the physical laws of Him whom they meet
to worship,--laws written not three thousand years ago upon Mount Sinai on
tables of stone, but to-day engraved in the constitution of their own
living, breathing bodies. On brains benumbed and starving for oxygen, the
purest truth and the highest eloquence fall with little force.

We sleep in a small bedroom from which every breath of fresh air is
excluded, because we believe night air to be unhealthy, [Footnote: There
is a singular prejudice against the night air. Yet, as Florence
Nightingale aptly says, what other air can we breathe at night? We then
have the choice between foul air within and pure air without. For, in
large cities especially, the night air is far more wholesome than that of
the daytime. To secure fresh air at night, we must open the windows of our
bedroom.] and so we breathe its dozen hogsheads of air over and over
again, and then wonder why we awaken in the morning so dull and
unrefreshed! Return to our room after inhaling the fresh, morning air, and
the fetid odor we meet on opening the door, is convincing proof how we
have poisoned our lungs during the night.

Each room should be supplied with two thousand feet of fresh air per hour
for every person it contains. Our ingenuity ought to find some way of
doing this advantageously and pleasantly. A moiety of the care we devote
to delicate articles of food, drink, and dress would abundantly meet this
prime necessity of our bodies.

Open the windows a little at the top and the bottom. Put on plenty of
clothing to keep warm by day and by night, and then let the inspiring
oxygen come in as freely as God has given it. Pure air is the cheapest
necessity and luxury of life. Let it not be the rarest!

SCHOOLROOM VENTILATION.--Who, on going from the open air of a clear,
bracing winter's day, into a crowded schoolroom, late in the session, has
not noticed the disagreeable odor, and been for a moment nauseated and
half stifled by the oppressive atmosphere! It is not strange. See how many
causes here combine to pollute the air. If the room is heated by a stove,
quantities of carbonic-oxide and carbonic-acid gases, as well as other
products of combustion, driven by downward drafts in the flue, escape
through seams and cracks and the occasionally opened door of the stove. In
the case of a furnace, the same effect is too often experienced, and the
odor of coal gas is a common one, especially when the fire is replenished.
The insensible perspiration is more active in children than in adults;
they, moreover, rush in with their clothing saturated with the
perspiration induced by their sports; so that, on the average, each pupil,
during school hours, loads the air with about half a pint of aqueous
vapor. The children come, oftentimes, from homes that are close, ill-
ventilated, and uncleanly; and frequently from sick rooms, bringing in
their clothing the germs of disease. (See p. 304.) Some of the pupils may
even bear traces of illness, or have unsound organs, and so their breath
and exhalations be poisonous.

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