Harvey in 1619. For several years, he did not dare to publish his belief.
When it became known, he was bitterly persecuted, and his practice as a
physician greatly decreased in consequence. He lived, however, to see his
theory universally adopted, and his name honored. Harvey is said to have
declared that no man over forty years of age accepted his views.] consists
of two parts--the _lesser_, and the _greater_.
FIG. 42.
[Illustration: _Diagram illustrating the Circulation of the Blood._--
MARSHALL. A, _vena cava descending (superior);_ Z, _vena cava
ascending (inferior);_ C, _right auricle;_ D, _right ventricle;_ E,
_pulmonary artery;_ F P, _lungs and pulmonary veins;_ G, _left auricle;_
H, _left ventricle;_ I, K, _aorta._]
1. _The Lesser Circulation_.--The dark blood from the veins collects
in the right auricle, and, going through the tricuspid valve, empties into
the right ventricle. Thence it is driven past the semilunar valves,
through the pulmonary artery, to the lungs. After circulating through the
fine capillaries of the air cells contained in the lungs, it is returned,
bright and red, through the four pulmonary veins, [Footnote: It is
noticeable that the pulmonary set of veins circulates red blood, and the
pulmonary set of arteries circulates dark blood. Both are connected with
the lungs.] to the left auricle.
2. _The Greater Circulation_.--From the left auricle, the blood is
forced past the bicuspid valve to the left ventricle; thence it is driven
through the semilunar valves into the great aorta, the main trunk of the
arterial system. Passing through the arteries, capillaries, and veins, it
returns through the venæ cavæ, ascending and descending, gathers again in
the right auricle, and so completes the "grand round" of the body. Both
these circulations are going on constantly, as the two auricles contract,
and the two ventricles expand simultaneously, and _vice versa_.
THE VELOCITY OF THE BLOOD varies so much in different parts of the body,
and is influenced by so many circumstances, that it can not be calculated
with any degree of accuracy. It has been estimated that a portion of the
blood will make the tour of the body in about twenty-three seconds
(FLINT), and that the entire mass passes through the heart in from one to
two minutes. [Footnote: The total amount of blood in an adult of average
weight is about eighteen pounds. Dividing this by five ounces, the
quantity discharged by the left ventricle at each systole, gives fifty-
eight pulsations as the number necessary to transmit all the blood in the
body. This, however, is an extremely unreliable basis of calculation, as
the rapidity of the blood is itself so variable. Chauvreau has shown by
experiments with his instrument that, corresponding to the first dilation
of the vessels, the blood moves with immense rapidity; following this, the
current suddenly becomes nearly arrested; this is succeeded by a second
acceleration in the current, not quite so rapid as the first; and after
this there is a gradual decline in the rapidity to the time of the next
pulsation.] (See p. 314.)
DISTRIBUTION AND REGULATION OF THE HEAT OF THE BODY.--1.
_Distribution_.--The natural temperature is not far from 98°.
[Footnote: The average temperature is, however, easily departed from.
Through some trivial cause the cooling agencies may be interfered with,
and then, the heating processes getting the superiority, a high
temperature or fever comes on. Or the reverse may ensue. In Asiatic
cholera, the constitution of the blood is so changed that its disks can no
longer carry oxygen into the system, the heat-making processes are put a
stop to, and, the temperature declining, the body becomes of a marble
coldness, characteristic of that terrible disease.--DRAPER.] This is
maintained, as we have already seen, by the action of the oxygen within
us. Each capillary tube is a tiny stove, where oxygen is combining with
the tissues of the body (see note, p. 107). Every contraction of a muscle
develops heat, the latent heat being set free by the breaking up of the
tissue. The warmth so produced is distributed by the circulation of the
blood. Thus the arteries, veins, and capillaries form a series of hot-
water pipes, through which the heated liquid is forced by a pump--the
heart--while the heat is kept up, not by a central furnace and boiler, but
by a multitude of little fires placed here and there along its course.
2. _Regulation_.--The temperature of the body is regulated by means
of the pores of the skin and the mucous membrane in the air passages. When
the system becomes too warm, the blood vessels on the surface expand, the
blood fills them, the fluid exudes into the perspiratory glands, pours out
upon the exterior, and by evaporation cools the body. [Footnote: Just as
water sprinkled on the floor cools a room.--_Popular Physics_, p.
255.] When the temperature of the body is too low, the vessels contract,
less blood goes to the surface, the perspiration decreases, and the loss
of heat by evaporation diminishes. [Footnote: Thus one is enabled to go
into an oven where bread is baking, or into the arctic regions where the
mountains are snow and the rivers ice. Even by these extremes the
temperature of the blood will be but slightly affected. In the one case,
the flood gates of perspiration will be opened and the superfluous heat
expended in turning the water to vapor; and, in the other, they will be
tightly closed and all the heat retained.]
LIFE BY DEATH.--The body is being incessantly corroded, and portions borne
away by the tireless oxygen. The scales of the epidermis are constantly
falling off and being replaced by secretion from the cutis. The disks of
the blood die, and new ones spring into being. On the continuance of this
interchange depend our health and vigor. Every act is a destructive one.
Not a bend of the finger, not a wink of the eye, not a thought of the
brain but is at some expense of the machine itself. Every process of life
is thus a process of death. The more rapidly this change goes on, and
fresh, vigorous tissue takes the place of the old, the more elasticity and
strength we possess.
CHANGE OF OUR BODIES.--There is a belief that our bodies change once in
seven years. From the nature of the case, the rate must vary with the
labor we perform; the organs most used altering oftenest. Probably the
parts of the body in incessant employment are entirely reorganized many
times within a single year. [Footnote: To use a homely simile, our bodies
are like the Irishman's knife, which, after having had several new blades,
and at least one new handle, was yet the same old knife.]
THE THREE VITAL ORGANS.--Death is produced by the stoppage of the action
of any one of the three organs--the heart, the lungs, or the brain. They
have, therefore, been termed the "Tripod of Life." Really, however, as
Huxley has remarked, "Life has but two legs to stand upon." If respiration
and circulation be kept up artificially, the removal of the brain will not
produce death. [Footnote: When death really does take place, _i. e._,
when the vital organs are stopped, it is noticeable that the tissues do
not die for some time thereafter. If suitable stimulants be applied, as
the galvanic battery, transfusion of blood, etc., the muscles may be made
to contract, and many of the phenomena of life be exhibited. Dr. Brown-
Sequard thus produced muscular action in the hand of a criminal, fourteen
hours after his execution.]
WONDERS OF THE HEART.--The ancients thought the heart to be the seat of
love. There were located the purity and goodness as well as the evil
passions of the soul. [Footnote: Our common words, hearty, large-hearted,
courage (_cor_, the heart), are remains of this fanciful theory.]
Modern science has found the seat of the mental powers to be in the brain.
But while it has thus robbed the heart of its romance, it has revealed
wonders which eclipse all the mysteries of the past. This marvelous little
engine throbs on continually at the rate of one hundred thousand beats per
day, forty millions per year, often three billions without a single stop.
It is the most powerful of machines. "Its daily work is equal to one third
that of all the muscles. If it should expend its entire force in lifting
its own weight vertically, it would rise twenty thousand feet in an hour."
[Footnote: "The greatest exploit ever accomplished by a locomotive, was to
lift itself through less than one eighth of that distance." Vast and
constant as is this process, so perfect is the machinery, that there are
persons who do not even know where the heart lies until disease or
accident reveals its location.] Its vitality is amazing. The most tireless
of organs while life exists, it is one of the last to yield when life
expires. So long as a flutter lingers at the heart, we know the spark of
being is not quite extinguished, and there is hope of restoration. During
a life such as we sometimes see, it has propelled half a million tons of
blood, yet repaired itself as it has wasted, during its patient,
unfaltering labor. The play of its valves and the rhythm of its throb have
never failed until, at the command of the great Master Workman, the
"wheels of life have stood still." [Footnote: Our brains are seventy-five-
year clocks. The Angel of Life winds them up once for all, then closes the
case, and gives the key into the hand of the Angel of the Resurrection.
Ticktack! Ticktack! go the wheels of thought; our will can not stop them,
they can not stop themselves; sleep can not stop them; madness only makes
them go faster; death alone can break into the case, and, seizing the
ever-swinging pendulum which we call the heart, silence at last the
clicking of the terrible escapement we have carried so long beneath our
wrinkled foreheads.--HOLMES.]
FIG. 43.
[Illustration: _Lymphatics of the Head and Neck, showing the Glands,
and,_ B, _the thoracic duct as it empties into the left innominate
vein at the junction of the left jugular and subclavian veins._]
THE LYMPHATIC CIRCULATION is intimately connected with that of the blood.
It is, however, more delicate in its organization, and less thoroughly
understood. Nearly every part of the body is permeated by a second series
of capillaries, closely interlaced with the blood capillaries already
described, and termed the Lymphatic system. The larger number converge
into the thoracic duct--a small tube, about the size of a goose quill,
which empties into the great veins of the neck (Fig. 43). Along their
course the lymphatics frequently pass through _glands_,--hard,
pinkish bodies of all sizes, from that of a hemp seed to an almond. These
glands are often enlarged by disease, and then are easily felt.
_The Lymph_, which circulates through the lymphatics like blood
through the veins, is a thin, colorless liquid, very like the serum. This
fluid, probably in great measure an overflow from the blood vessels, is
gathered up by the lymphatics, undergoes in the glands some process of
preparation not well understood, and is then returned to the circulation.
FIG. 44.
[Illustration: _Lymphatics in the Leg, with Glands at the Hip_.]
OFFICE OF THE LYMPHATICS.--It is thought that portions of the waste matter
of the body capable of further use are thus, by a wise economy, retained
and elaborated in the system.
The _lacteals_, a class of lymphatics which will be described under
Digestion (p. 166), aid in taking up the food; after a meal they become
milk white. In the lungs, the lymphatics are abundant; sometimes absorbing
the poison of disease, and diffusing it through the system. [Footnote:
Persons have thus been poisoned by tiny particles of arsenic which
evaporate from green wall paper, and float in the air.]
The lymphatics of the skin we have already spoken of as producing the
phenomena of absorption, [Footnote: Pain is often relieved by injecting
under the cuticle a solution of morphine, which is taken up by the
absorbents, and so carried through the system.] Nature in her effort to
heal a cut deposits an excess of matter to fill up the breach. Soon, the
lymphatics go to work and remove the surplus material to other parts of
the body.
Animals that hibernate are supported during the winter by the fat which
their absorbents carry into the circulation from the extra supply they
have laid up during the summer. In famine or in sickness, a man
unconsciously consumes his own flesh.
DISEASES, ETC.--l. _Congestion_ is an unnatural accumulation of blood
in any part of the body. The excess is indicated by the redness. If we put
our feet in hot water, the capillaries will expand by the heat, and the
blood will set that way to fill them. The red nose and purplish face of
the drunkard show a congestion of the capillaries. Those vessels have lost
their power of contraction, and so are permanently increased in size and
filled with blood. Blushing is a temporary congestion. The capillaries
being expanded only for an instant by the nervous excitement, contract
again and expel the blood. [Footnote: Blushing is a purely local
modification of the circulation of this kind, and it will be instructive
to consider how a blush is brought about. An emotion--sometimes
pleasurable, sometimes painful--takes possession of the mind; thereupon a
hot flush is felt, the skin grows red, and according to the intensity of
the emotion these changes are confined to the cheeks only, or extend to
the "roots of the hair," or "all over." What is the cause of these
changes? The blood is a red and a hot fluid; the skin reddens and grows
hot, because its vessels contain an increased quantity of this red and hot
fluid; and its vessels contain more, because the small arteries suddenly
dilate, the natural moderate contraction of their muscles being superseded
by a state of relaxation. In other words, the action of the nerves which
cause this muscular contraction is suspended. On the other hand, in many
people, extreme terror causes the skin to grow cold, and the face to
appear pale and pinched. Under these circumstances, in fact, the supply of
blood to the skin is greatly diminished, in consequence of an excessive
stimulation of the nerves of the small arteries, which causes them to
contract and so to cut off the supply of blood more or less completely.--
Huxley's _Physiology_.]
2. _Inflammation_ means simply a burning. If there is irritation or
an injury at any spot, the blood sets thither and reddens it. This extra
supply, both by its presence and the friction of the swiftly moving
currents, produces heat. The pressure of the distended vessels upon the
nerves frets them, and produces pain. The swelling stretches the walls of
the blood vessels, and the serum or lymph oozes through. The four
characteristics of an inflammation are redness, heat, pain, and swelling.
3. _Bleeding_, if from an artery, will be of red blood, and will come
in jets; [Footnote: The elasticity of the arteries (p. 114) is a physical
property, as may easily be shown by removing one from a dead body. If they
were rigid and unyielding, a considerable portion of the heart's force
would be uselessly expended against their walls. Their expansion is a
passive state, and depends on the pressure of the blood within them; but
their vital contractility is an active property.--The intermittent
movement of the blood through the arteries is strikingly shown in the
manner in which they bleed when wounded. When an artery is cut across, the
blood spurts out with great force to a distance of several feet, but the
flow is not continuous. It escapes in a series of jets, the long, slender
scarlet stream rising and falling with each beat of the heart, and this
pulsation of the blood stream tells at once that it comes from a wounded
artery. But as the blood traverses these elastic tubes, the abruptness of
the heart's stroke becomes gradually broken and the current equalized, so
that the greater the distance from the heart the less obvious is the
pulsation, until at length in the capillaries the rate of the stream
becomes uniform.] if from the veins, it will be of dark blood, and will
flow in a steady stream. If only a small vessel be severed, it may be
checked by a piece of cloth held or bound firmly upon the wound. If a
large trunk be cut, especially in a limb, make a knot in a handkerchief
and tie it loosely about the limb; then, placing the knot on the limb,
with a short stick twist the handkerchief tightly enough to stop the flow.
If you have a piece of cloth to use as a pad, the knot will be
unnecessary. If it be an artery that is cut, the pressure should be
applied between the wound and the heart; if a vein, beyond the wound. If
you are alone, and are severely wounded, or in an emergency, like a
railroad accident, use the remedy which has saved many a life upon the
battlefield--bind or hold a handful of dry earth upon the wound, elevate
the part, and await surgical assistance.
4. _Scrofula_ is generally inherited. It is a disease affecting the
lymphatic glands, most commonly those of the neck, forming "kernels," as
they are called. It is, however, liable to attack any organ. Persons
inheriting this disease can hope to ward off its insidious approaches only
by the utmost care in diet and exercise; by the use of pure air and warm
clothing, and by avoiding late hours and undue stimulus of all kinds.
Probably the most fatal and common excitants of the latent seeds of
scrofula are insufficient or improper food, and want of ventilation.
5. _A COLD_.--We put on a thinner dress than usual, or, when heated,
sit in a cool place. The skin is chilled, and the perspiration checked.
The blood, no longer cleansed and reduced in volume by the drainage
through the pores, sets to the lungs for purification. That organ is
oppressed, breathing becomes difficult, and the extra mucus secreted by
the irritated surface of the membrane is thrown off by coughing. The
mucous membrane of the nasal chamber sympathizes with the difficulty, and
we have "a cold in the head," or a catarrh. In general, the excess of
blood seeks the weakest point, and develops there any latent disease
[Footnote: A party go out for a walk and are caught in a rain, or, coming
home heated from some close assembly, throw off their coats to enjoy the
deliciously cool breeze. The next day, one has a fever, another a slight
headache, another pleurisy, another pneumonia, another rheumatism, while
some of the number escape without any ill feeling whatever. The last had
vital force sufficient to withstand the disturbance, but in the others
there were various weak points, and to these the excess of blood has gone,
producing congestion.] Where one person has been killed in battle,
thousands have died of colds.
To restore the equipoise must be the object of all treatment. We put the
feet in hot water and they soon become red and gorged with the blood which
is thus called from the congested organs. Hot footbaths have saved
multitudes of lives. It is well in case of a sudden cold to go immediately
to bed, and with hot drinks and extra clothing open the pores, and induce
free perspiration. This calls the blood to the surface, and, by equalizing
and diminishing the volume of the circulation, affords relief. [Footnote:
Severe colds may often be relieved in their first stages by using lemons
freely during the day, and taking at night fifteen or twenty grains of
sodium bromide. Great care, however, should be observed in employing the
latter remedy, except under the advice of a physician.]
6. _Catarrh_ commonly manifests itself by the symptoms known as those
of a "cold in the head," and is produced by the same causes. It is an
inflammation of the mucous membrane lining the nasal and bronchial
passages. One going out from the hot dry air of a furnace-heated room into
the cold damp atmosphere of our climate can hardly avoid irritating and
inflaming this tender membrane. If our rooms were heated less intensely,
and ventilated more thoroughly, so that we had not the present hothouse
sensitiveness to cold air, this disease would be far less universal, and
perhaps would disappear entirely. [Footnote: Dr. Gray gives the following
table:
=====================================================================
Rooms Occupied by Letter-press Printers. | Number | Subject to
| per cent | Catarrh
| Spitting |
| Blood. |
------------------------------------------+------------+-------------
104 men having less than 500 cubic feet | |
of air to breathe | 12.50 | 12.50
| |
115 men having from 500 to 600 cubic feet | |
of air to breathe | 4.35 | 3.58
| |
101 men having more than 600 cubic feet | |
of air to breathe | 3.96 | 1.98
---------------------------------------------------------------------]
(See p. 315.)
ALCOHOLIC DRINKS AND NARCOTICS.
1. ALCOHOL.
That we may understand fully the effect of alcohol upon the human system,
let us first consider its nature and the process by which harmless fruits
and grains are made to produce a substance so unlike themselves in its
deleterious effects.
HOW ALCOHOL IS MADE.--When any substance containing sugar, as fruit juice,
is caused to ferment, the elements of which the sugar is composed, viz.,
hydrogen, carbon, and oxygen, so rearrange themselves as to form carbon
dioxide (carbonic acid), alcohol, and certain volatile oils and ethers.
[Footnote: The precise relation between chemical phenomena and the
physiological functions of the organic ferment is still to be discovered;
and all that has been said, written, and brought forward to decide the
question, need experimental proof.--SCHÜTZENBERGER.] The carbonic acid
partly evaporates and partly remains in the liquor; the alcohol is the
poisonous or intoxicating principle, while the oils and ethers impart the
peculiar flavor and odor. Thus wine is fermented grape juice, and cider is
fermented apple juice, each having its distinctive taste and smell, and
each containing, as one product of fermentation, more or less of the
inebriating alcohol. Wines are also made from other fruits and vegetables,
such as oranges, currants, tomatoes, and rhubarb, but the alcohol which
they contain is of the same nature in all cases, whether the fermented
liquor has been manufactured in great quantities, by large presses, or by
a simple domestic process for home consumption. It is important to
remember this fact, as many people do not associate alcohol with such
beverages as domestic wines and home-brewed ales, whereas it is always
present with the same treacherous qualities which attach to it everywhere.
An apple is a wholesome and useful fruit, and its simple juice, fragrant
and refreshing, is a delight to the palate; but apple juice converted into
cider and allowed to enter upon alcoholic fermentation, loses its
innocence, and becomes a dangerous drink, because it is the nature of the
alcohol it now contains to create an appetite for more alcohol. (See p.
185.)