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.
In addition to all this, the air is filled with dust brought in and kept astir by many busy feet; with ashes floating from the stove or furnace; and especially with chalk dust. The modern method of teaching requires a large amount of blackboard work, and the air of the schoolroom is thus loaded with chalk particles. These collect in the nasal passages, and the upper part of the larynx, and irritate the membrane, perhaps laying the foundation of catarrh.
The usual schoolroom atmosphere bears in the pupils the natural fruit of frequent headaches, inattention, weariness, and stupor; but in the teacher its frightful influence is most apparent. His labor is severe, his worry of mind is constant, and, when he finishes his day's work, he is generally too tired to take proper physical exercise. He consequently labors on with impaired health, or is forced to abandon his profession.
Instead of six hundred feet of space being allowed for each pupil, as perfect ventilation demands—the lowest estimate being two hundred and fifty feet—often not over one hundred feet are afforded. Instead of two thousand cubic feet of fresh air being supplied every hour for each person, and as much foul air removed, which, all physiologists assert, is needed for perfect health, perhaps no means of ventilation at all are provided, and none is secured except what an occasionally opened door, or the benevolent cracks and chinks in the building furnish the suffering lungs. [Footnote: Imagine fifty pupils put into a class room thirty feet long, twenty-five feet wide, and ten feet high. This would generally be considered a very liberal provision. Such a room contains seven thousand five hundred cubic feet of air. But it furnishes only one hundred and fifty feet of space for each pupil. Allowing ten cubic feet of air per pupil each minute, in fifteen minutes after assembling, the entire atmosphere of the room is tainted, and unfit to be rebreathed. The demand of health is that at least one thousand five hundred cubic feet of pure air should be admitted into this room every minute, and as much be removed.]
HOW SHALL WE VENTILATE?—The usual method of ventilation depends upon the fact that hot air is lighter than cold air, and so the cold air tends, by the force of gravity, to fall and compel the warm air to rise. Thus, if we open the door of a heated room, and hold a lighted candle first at the top, and then at the bottom, we can see, by the deflection of the flame, that there is a current of air setting outward at the top, and another setting inward at the bottom of the opening. A handkerchief held loosely, or the smoke of a smoldering match, in front of a fireplace will show a current of air passing up the chimney; this is caused by the difference of temperature between the air in the room and the outside atmosphere. Upon this difference of temperature, all ordinary ventilation is based. [Footnote: Public buildings are sometimes ventilated by mechanical means, i. e., immense fans which are turned by machinery, and thus set the air in motion. Such methods are, however, expensive, and rarely adopted, except where power is also used for other purposes.] A proper treatment of this subject and its practical applications, would require a book by itself. There is room here for only a few general statements and suggestions.
1. Two openings are always necessary to produce a thorough change of air. (See "Popular Chemistry," p. 70.) Put a lighted candle in a bottle. The flame will soon be extinguished. The oxygen of the little air in the bottle is burned out, and carbonic acid has taken its place. Now place over the mouth of the bottle a lamp chimney, and insert in the chimney a strip of cardboard, thus dividing the passage. On relighting the candle, it will burn freely. The smoke of a bit of smoldering paper will show that two opposite currents of air are established, one setting into the bottle, the other outward.
2. In the winter, when our schoolrooms, churches, public halls, etc., are heated artificially, ventilation is comparatively easy if properly arranged. [Footnote: For the escape of bad air, Dr. Bell suggests that an efficient foul-air shaft may be fitted to the commonest of stoves by simply inclosing the stovepipe in a jacket—that is, in a pipe two or three inches greater in diameter. This should be braced round the stovepipe and left open at the end next the stove. At its entrance into the chimney, a perforated collar should separate it from the stovepipe.] The required difference of temperature is kept up with little difficulty. The fresh air admitted to the room should then be heated [Footnote: Ventilation is change of air, and, unless scientifically arranged, and especially unless the incoming volume of air be warmed in cold weather, such change of atmosphere means cold currents, with their attendant train of catarrhs, bronchitis, neuralgia, rheumatism, and all the evils that spring from these diseases. The raw, damp, frosty air of our ever-changing winter temperature ought not to have uncontrolled and constant ingress to our dwellings. Air out of doors is suited to out of door habits. It is healthy and bracing when the body is coated and wrapped, and prepared to meet it, and when exercise can be taken to keep up the circulation; but to live under cover is to live artificially, and such essential conditions must be observed as suit an abnormal state. All the evils attaching to ventilation, as it is generally effected, spring from the neglect of this consistency.—Westminster Review.] either by a furnace, or by passing over a stove, or through a coil of steam pipes. This cold air should always be taken directly from out of doors, and not from a cellar, or from under a piazza, where contamination is possible.
3. In order to remove the impure air, there should be ventilators provided at or near the floor, opening into air shafts, or pipes leading upward through the roof, with proper orifices at the top. These ventilating pipes should be heated artificially so as to produce a draught. They may form one of the flues of a chimney in which there is a constant fire; or be carried upward in a large flue through the center of which runs the smoke pipe of the furnace or stove; [Footnote: This plan has been adopted in the newer school buildings of Elmira, N. Y. The older buildings were provided with ventilating pipes, not heated artificially, and hence of no service. These pipes are rendered effective, however, by conducting them into a small room in the garret, heated by a coal stove. From this room, a large exit pipe leads to the roof, where it terminates in an Emerson's ventilator. So strong a draught is thus established that throughout the building air is taken from the floors, and consequently the cooler portion of the rooms, at a velocity of three to five feet per second or one hundred and eighty to three hundred cubic feet per minute for each square foot of flue opening. In perpendicular flues, heated throughout with a smoke flue from the furnace, ten feet per second is attained.] or the ventilating pipe be itself conveyed through the center of the larger chimney flue. If the register for hot air be on the floor at one side of the room, two or more ventilators may be placed near the floor on the opposite side. The warm air will thus make the complete circuit of the room, and thoroughly warm it before passing out.
If the ventilating shaft be not heated artificially; the ventilator must be placed at the top of the room in order that the hot air may escape through it, thus producing an upward draught. But the objection to this method is that it allows the warmer air to escape, while economy requires that the cooler air at the bottom of the room should be removed and the warm air be made to descend, thus securing uniformity of temperature.
4. In the summer, ventilation may be commonly provided for by opening windows at the top and the bottom, on the sheltered side of the building, so as to avoid draughts of air injurious to the occupants. On a dull, still, hot day, when there is little difference of temperature between the inner and the outer air, ventilation can be secured only by having a fire provided in the ventilating shaft; this, by exhausting the air from the room, will cause a fresh current to pour in through the open windows. At recess, all the children should, if the weather permit, be sent out of doors, to allow their clothing to be exposed to the purifying influence of the open air; meantime, the windows should be thrown wide open, that the room may be thoroughly ventilated during their absence. In bad weather, rapid marching or calisthenic exercises will furnish exercise, and also permit the airing of the room.
5. The school and the church are the centers for spreading contagious diseases. The former offers especially dangerous facilities for scattering disease germs. Great pains, therefore, should be taken to exclude pupils attacked by or recovering from diphtheria, scarlet fever, whooping cough, etc., and even those who live in houses where such sickness exists.
6. In our houses [Footnote: The air of our homes is often contaminated by decaying vegetables and other filth in the cellar; by bad air drawn up from the soil into the cellar, by the powerful draughts that our fires create; by defective gas and waste pipes that let the foul air from cesspool or sewer spread through the house; and by piles of refuse, or puddles of slops emptied at the back door. Too often, also, the water in our wells, or in the streams that supply our towns and cities, receives the drainage from outhouses and barnyards, and so introduces into our systems, in the liquid—and thus easily assimilated—form, the most dangerous poisons. The question of sanitary precautions is one that presses upon every observant mind, and demands constant and thoughtful attention. (See p. 305.)] open fireplaces are efficient ventilators, and they should never be closed for any cause. Fresh air admitted by a hot-air register and impure air passed out by a chimney, form a simple and thorough system. Our sleeping apartments demand especial care. As soon as the occupants leave the room, the bedclothes should be removed, and laid on the backs of chairs to air; the bed be shaken up; and the windows thrown open. In the summer, the windows may be closed before the sun is high; the house is then left filled with the cool morning air. In damp and cold weather, a fire should be lighted in sleeping apartments, particularly if used by children [Footnote: In winter, children should always be given a moderately warm, well-ventilated bedroom, with light, fleecy bed coverings. Says a recent English writer: "The loving care which prescribes for children a cold bedroom and a hot, sweltering bed is of the nature that kills. Buried in blankets, their delicate skins become overheated and relaxed, while they are irritated by perspiration; at the same time, the most delicate tissues of all, in the lungs, are dealing with air abnormally frigid. The poor little victims of combined ignorance and kindness thus toss and dream, feverish and troubled, under a mass of bedclothes, while the well-meaning mother, soothed by a bedroom fire, slumbers peacefully through this working out of the sad process of the 'survival of the fittest.'"] or delicate persons, to dry the bedclothing, and also to prevent a chill on the part of the occupants. It is not necessary to go shivering to bed in order to harden one's constitution.
WONDERS OF RESPIRATION.—The perfection of the organs of respiration challenges our admiration. So delicate are they that the least pressure would cause exquisite pain, yet tons of air surge to and fro through their intricate passages, and bathe their innermost cells. We yearly perform at least seven million acts of breathing, inhaling one hundred thousand cubic feet of air, and purifying over three thousand five hundred tons of blood. This gigantic process goes on constantly, never wearies or worries us, and we wonder at it only when science reveals to us its magnitude. In addition, by a wise economy, the process of respiration is made to subserve a second use no less important, and the air we exhale, passing through the organs of voice, is transformed into prayers of faith, songs of hope, and words of social cheer.
FIG. 33.
[Illustration: A, the natural position of the internal organs. B when deformed by tight lacing Marshall says that the liver and the stomach have, in this way, been forced downward almost as low as the pelvis.]
DISEASES, ETC.—1. Constriction of the Lungs is produced by tight clothing. The ribs are thus forced inward, the size of the chest is diminished, and the amount of inhaled air decreased. Stiff clothing, and especially a garment that will not admit of a full breath without inconvenience, will prevent that free movement of the ribs so essential to health. Any infraction of the laws of respiration, even though it be fashionable, will result in diminished vitality and vigor, and will be fearfully punished by sickness and weakness through the whole life.
2. Bronchitis (bron-ki'-tis) is an inflammation (see Inflammation) of the mucous membrane of the bronchial tubes. It is accompanied by an increased secretion of mucus, and consequent coughing.
3. Pleurisy is an inflammation of the pleura. It is sometimes caused by an injury to the ribs, and results in a secretion of water within the membrane.
4. Pneumonia (pneuma, breath) is an inflammation of the lungs, affecting chiefly the air cells.
5. Consumption is a disease which destroys the substance of the lungs. Like other lung difficulties, it is caused largely by a want of pure air, a liberal supply of which is the best treatment that can be prescribed for it. [Footnote: If I were seriously ill of consumption, I would live outdoors day and night, except in rainy weather or midwinter; then I would sleep in an unplastered log house. Physic has no nutriment, gaspings for air can not cure you, monkey capers in a gymnasium can not cure you, stimulants can not cure you. What consumptives want is pure air, not physic, plenty of meat and plenty of bread.—DR. MARSHALL HALL.]
6. Asphyxia (as-fix'-i-a).—When a person is drowned, strangled, or choked in any way, what is called asphyxia occurs. The face turns black; the veins become turgid; insensibility and often convulsions ensue. If relief is not secured within a few minutes, death will be inevitable. [Footnote: The lack of oxygen, and the presence of carbonic-acid gas, are the combined causes. Oxygen starvation and carbonic-acid poisoning, each fatal in itself, work together to destroy life.] (See p. 264.)
7. Diphtheria (diphthera, a membrane) is characterized by fever, debility, and a peculiar sore throat, in which exuding fibrinous matter forms a grayish white membrane, which afterward decomposes with a fetid odor. Its sudden and insidious approach, contagious character, and frequent fatality, render it an exceedingly dreaded disease. A diphtheritic patient should be quarantined, and everything connected with the sick room thoroughly disinfected.
8. Croup, which often attacks young children, is an inflammation of the mucous membrane of the larynx and trachea. It is commonly preceded by a cold. The child sneezes, coughs, and is hoarse, but the attack frequently comes on suddenly, and usually in the night. It is accompanied by a peculiar "brassy," ringing cough, which, once heard, can never be mistaken. It may prove fatal within a few hours. (See p. 260.)
9. Stammering depends, not on defects of the muscles, but on a want of due control of the mind. When a stammerer is not too conscious of his lack, and tries to form his words slowly, he speaks plainly, and may sing well, for then his words must follow one another in rhythmic time. Many persons who stammer in common conversation can talk with fluency when making a speech. The stammerer should seek to discover the cause of his difficulty, and to overcome it by vocal and respiratory exercise, especially by speaking only after a full inspiration, and during a long, slow expiration.
PRACTICAL QUESTIONS.
1. What is the philosophy of "the change of voice" in a boy?
2. Why can we see our breath on a frosty morning?
3. When a law of health and a law of fashion conflict, which should we obey?
4. If we use a "bunk" bed, should we pack away the clothes when we first rise in the morning?
5. Why should a clothespress be well ventilated?
6. Should the weight of our clothing hang from the waist, or the shoulder?
7. Describe the effects of living in an overheated room.
8. What habits impair the power of the lungs?
9. For full, easy breathing in singing, should we use the diaphragm and lower ribs, or the upper ribs alone?
10. Why is it better to breathe through the nose than the mouth?
11. Why should not a speaker talk while returning home on a cold night after a lecture?
12. What part of the body needs the loosest clothing?
13. What part needs the warmest?
14. Why is a "spare bed" generally unhealthful?
15. Is there any good in sighing?
16. Should a hat be thoroughly ventilated? How?
17. Why do the lungs of people who live in cities become of a gray color?
18. How would you convince a person that a bedroom should be aired? [Footnote: "If the condensed breath collected on the cool windowpanes of a room where a number of persons have been assembled, be burned, a smell as of singed hair will show the presence of organic matter; and if the condensed breath be allowed to remain on the windows for a few days, it will be found, on examination by the microscope, that it is alive with animalculæ."]
19. What persons are most liable to catarrhs, consumption, etc.?
20. If a person is plunged under water, will it enter his lungs?
21. Are bed curtains healthful?
22. Why do some people take "short breaths" after a meal?
23 What is the special value of public parks?
24. Can a person become used to bad air, so that it will not injure him?
25. Why do we gape when we are sleepy?
26. Is a fashionable waist a model of art in sculpture or painting?
27. Should a fireplace be closed? [Footnote: Thousands of lives would be saved if all fireplaces were kept open. If you are so fortunate as to have a fireplace in your room, paint it when not in use, put a bouquet of fresh flowers in it every morning, if you please, or do anything to make it attractive, but never close it; better use the fireboards for kindling wood. It would be scarcely more absurd to take a piece of elegantly-tinted court-plaster and stop up the nose, trusting to the accidental opening and shutting of the mouth for fresh air, because you thought it spoiled the looks of your face to have two such great, ugly holes in it, than to stop your fireplace with elegantly-tinted paper, or a Japanese fan, because it looks better.—Leeds.]
28. Why does embarrassment or fright cause a stammerer to stutter still more painfully?
29. In the organs of voice, what parts have somewhat the same effect as the case of a violin and the sounding-board of a piano?
30. Why should we be careful not to "take the breath of a sick person"?
31. What special care should be taken with regard to keeping a cellar clean?
32. How is the air strained as it passes into the lungs?
33. Can one really "draw the air into his lungs"?
34. How often do we breathe?
35. Describe some approved method of ventilation.
36. What is at once the floor of the chest and the roof of the abdomen?
37. What would you do in a case of apparent death by drowning, or by coal gas? (See p. 264.)
38. What would you do in a case of croup, while the doctor was coming? (See p. 260.)
39. How would you treat a severe burn? (See p. 257.)
40. Describe the various ways in which the water in a well is liable to become unwholesome.
FIG. 34.
[Illustration]
V.
THE CIRCULATION.
"No rest this throbbing slave may ask,
Forever quivering o'er his task,
While far and wide a crimson jet
Leaps forth to fill the woven net,
Which in unnumber'd crossing tides
The flood of burning life divides,
Then, kindling each decaying part,
Creeps back to find the throbbing heart."
HOLMES.
ANALYSIS OF THE CIRCULATION
| 1. Its Composition. | 1. THE BLOOD | 2. Its Uses. | | 3. Transfusion. | |4. Coagulation | | | 1. Description. | | 2. Movements. | | 3. Auricles and Ventricles. | | | | 1. The | | a. Need of. | | Heart.| | b. Tricuspid and | | | | Bicuspid. | | | 4. The | c. The Strengthen- | | | Valves. | ing of the | | | | Valves. | | | | d. Semilunar | | | | Valves. | | _ | 2. ORGANS OF THE | 2. The | 1. Description. | CIRCULATION | Arteries | 2. The Arterial System. | | |_3. The Pulse. | | _ | | 3. The | 1. General Description. | | Veins |_2. Valves. | | _ | | 4. The | 1. Description. | | Capilla-| 2. Use. | |_ ries |_3. Under the Microscope. | _ | | 1. The Lesser. | 3. THE CIRCULATION.| 2. The Greater. | |3. The Velocity of the Blood. | | 4. THE HEAT OF THE | 1. Distribution. | BODY. |2. Regulation. | | 5. LIFE BY DEATH. | | 6. CHANGE OF OUR BODIES. | | 7. THE THREE VITAL ORGANS. | | 8. WONDERS OF THE HEART. | | | 1. Description | 9. THE LYMPHATIC | 2. The Glands. | CIRCULATION. | 3. The Lymph. | |4. The Office of the Lymphatics. | | | 1. Congestion. | | 2. Inflammation. | | 3. Bleeding. | 10. DISEASES. | 4. Scrofula. | | 5. A Cold. | |6. Catarrh. | | | 1. Effect of Alcohol upon the Circulation. | 11. ALCOHOLIC | 2. Effect of Alcohol upon the Heart. | DRINKS AND | 3. Effect of Alcohol upon the Membrane. |_ NARCOTICS. | 4. Effect of Alcohol upon the Blood. |_5. Effect of Alcohol upon the Lungs.
THE CIRCULATION.
THE ORGANS OF THE CIRCULATION are the heart, the arteries, the veins, and the capillaries.
FIG. 35.
[Illustration: A, corpuscles of human blood, highly magnified; B, corpuscles in the blood of an animal (a non mammal).]
THE BLOOD is the liquid by means of which the circulation is effected. It permeates every part of the body, except the cuticle, nails, hair, etc. The average quantity in each person is about eighteen pounds. [Footnote: It is difficult to estimate the exact amount, and therefore authorities disagree. Foster places it at about one thirteenth of the body weight.] It is composed of a thin, colorless liquid, the plasma, filled with red disks or cells, [Footnote: There is also one white globular cell to every three or four hundred red ones. The blood is no more red than the water of a stream would be if you were to fill it with little red fishes. Suppose the fishes to be very, very small—as small as a grain of sand— and closely crowded together through the whole depth of the stream; the water would look quite red, would it not? And this is the way in which, blood looks red—only observe one thing; a grain of sand is a mountain in comparison with the little red fishes in the blood. If I were to tell you they measured about 1/3500 of an inch in diameter, you would not be much wiser; so I prefer saying (by way of giving you a more perfect idea of their minuteness) that there would be about a million in such a drop of blood as would hang on the point of a needle. I say so on the authority of a scientific microscopist—M. Bouillet. Not that he has ever counted them, as you may suppose, any more than I have done; but this is as near an approach as can be made by calculation to the size of 1/3500 part of an inch in diameter.—JEAN MACE.] so small that about three thousand five hundred placed side by side would measure only an inch, and it would take sixteen thousand laid flatwise upon one another to make a column of that height. Under the microscope, they are found to be rounded at the edge and concave on both sides. [Footnote: By pricking the end of the finger with a needle, we can obtain a drop for examination. Place it on the slide, cover with a glass, and put it at once under the microscope. The red disks will be seen to group themselves in rows, while the white disks will seem to draw apart, and to be constantly changing their form. After a gradual evaporation, the crystals (Fig. 36) may be seen. In animals, they have various, though distinctive forms.] They have a tendency to collect in piles like rolls of coin. The size and shape vary in the blood of different animals. [Footnote: Authorities differ greatly in their estimate of the size of the disks (corpuscles) in human blood. The fact is that the size varies in different persons, probably also in the same individual. Many of the best microscopists therefore hesitate to state whether a particular specimen of blood belonged to a human being or to an animal. Others claim that they can distinguish with accuracy. Evidently, the question is one of great uncertainty. The following statement of the size of the cells in different animals is taken from Gulliver's tables: Cat, 1/4404 of an inch in diameter; whale, 1/3100; mouse, 1/3614; hog, 1/4230; camel, 1/3123; sheep, 1/3352; horse, 1/4800; Virginia deer, 1/5038; dog- faced baboon, 1/4861; brown baboon, 1/3493; red monkey, 1/3396; black monkey, 1/3530.] Disks are continually forming in the blood, and are constantly dying—twenty million at every breath.—DRAPER.
The plasma also contains fibrin, [Footnote: it is usual to say that fibrin is contained in the blood. It probably does not exist as such, but there are present in the blood certain substances known as paraglobulin and fibrinogen, which by the action of a third substance, fibrin ferment under certain circumstances, form fibrin and so cause coagulation. The exact nature of the process by which fibrin is produced by these three factors is not understood—See Foster's Text Book of Physiology, p 22.] albumin—which is found nearly pure in the white of an egg—and various mineral substances, as iron, [Footnote: Enough iron has been found in the ashes of a burned body to form a mourning ring.] lime, magnesia, phosphorus, potash, etc.
FIG. 36.
[Illustration: Blood Crystals]
USES OF THE BLOOD.—The blood has been called "liquid flesh"; but it is more than that, since it contains the materials for making every organ. The plasma is rich in mineral matter for the bones, and in albumen for the muscles. The red disks are the air cells of the blood. They contain the oxygen so essential to every operation of life. Wherever there is work to be done or repairs to be made, there the oxygen is needed. It stimulates to action, and tears down all that is worn out. In this process, it combines with and actually burns out parts of the muscles and other tissues, as wood is burned in the stove. [Footnote: For the sake of simplicity, perhaps to conceal our own ignorance, we call this process "burning." The simile of a fire is good so far as it goes. But as to the real nature of the change which the physiologist briefly terms "oxidation," we know nothing. This much only can be asserted positively. A stream of oxygen is carried by the blood to the muscles (in fact to every tissue in the body), while, from the muscles the blood carries away a stream of carbonic acid and water. But what takes place in the muscles, when and what chemical change occurs, no one can tell. We see the first and the last stage. We know that contraction of the muscles somehow comes about, oxygen disappears, carbonic acid appears, energy is released, and force is exhibited as motion, heat, and electricity. But the intermediate step is hidden.
There are certain theories advanced, however, that are worth considering. Some physiologists hold that the muscle has the power of taking up the oxygen from the hemoglobin (a body that comprises ninety per cent of the red corpuscles when dried, and is the oxygen carrier of the blood), and fixing it, as well as the raw material (food) furnished by the blood, thus forming a true contractile substance. The breaking down or decomposition of this contractile substance in the muscle, sets free its potential energy. The process is gentle so long as the muscle is at rest, but becomes excessive and violent when contraction occurs. (See "Foster's Physiology," p. 118.) It is also believed by some that the chemical change in the muscle partakes of a fermentive character; that, under the influence of the proper ferments, the substances break up into other and simpler products, thus setting free heat and force; and that this chemical change is followed by a secondary oxidation by the oxygen in the arterial blood, thereby forming carbonic acid and water, as in all putrefactive processes. But these and other views are not as yet fully understood; while they utterly fail to tell us how a collection of simple cells, filled merely with a semifluid mass of matter, can contract and set free muscular power. The commonness of this act hides from us its wonderful nature. But here, hidden in the cell—Nature's tiny laboratory—lies the mystery of life. Before its closed door we ponder in vain, confessing the unskillfulness of our labor, and fearing all the while lest the Secret of the Cell will always elude our search.] The blood, now foul with the burned matter, the refuse of this fire, is caught up by the circulation, and whirled back to the lungs, where it is purified, and again sent bounding on its way.
There are then two different kinds of the blood in the body: the red or arterial, and the dark or venous.
TRANSFUSION.—As the blood is really the "vital fluid" it would seem that feeble persons might be restored to vigor by infusing healthy blood into their veins. This hypothesis, so valuable in its possible results in prolonging human life, has been carefully tested. Animals which have ceased to breathe have thus had their vitality recalled. In the seventeenth century the theory became a subject of special investigation. A maniac was restored to reason by the blood of a calf, and the most extravagant hopes were entertained. But many fatal accidents occurring, experiments upon human beings were forbidden by law, and transfusion soon fell into disuse. It has, however, been successfully practiced in several cases within the last few years, and is a method still in repute for saving lives.
COAGULATION.—When blood is exposed to the air, it coagulates. This is caused by the solidifying of the fibrin, which entangling the disks, forms the "clot." The remaining clear, yellow liquid is the serum. The value of this peculiar property of the blood can hardly be overestimated. The coagulation soon checks all ordinary cases of bleeding. [Footnote: In the case of the lower animals, which have no means of stopping hemorrhages as we have, the coagulation is generally still more rapid. In some species of birds it takes place almost instantaneously.] When a wound is made, and bleeding commences, the fibrin forms a temporary plug, as it were, which is absorbed when the healing process is finished. Thus we see how a Divine foresight has provided not only for the ordinary wants of the body, but also for the accidents to which it is liable. [Footnote: The fibrin is not an essential ingredient of the blood. All the functions of life are regularly performed in people whose blood lacks fibrin; and, in cases of transfusion, where blood deprived of its fibrin was used, the vivifying influence seemed to be the same. Its office, therefore, must mainly be to stanch any hemorrhage which may occur.—FLINT.]
FIG. 37.
[Illustration: The Heart. A, the right ventricle; B, the left ventricle; C, the right auricle; D, the left auricle.]
THE HEART is the engine which propels the blood. It is a hollow, pear- shaped muscle, about the size of the fist. It hangs, point downward, just to the left of the center of the chest. (See Fig. 31.) It is inclosed in a loose sac of serous membrane, [Footnote: The mucous membrane lines the open cavities of the body; the serous, the closed. The pericardium is a sac composed of two layers—a fibrous membrane on the outside, and a serous one on the inside. The latter covers the external surface of the heart, and is reflected back upon itself in order to form, like all the membranes of this nature, a sac without an opening. The heart is thus covered by the pericardial sac, but not contained inside its cavity. A correct idea may be formed of the disposition of the pericardium around the heart by recalling a very common and very convenient, though now discarded headdress, the cotton nightcap. The pericardium incloses the heart exactly as this cap covered the heads of our forefathers.— Wonders of the Human Body.] called the pericardium (peri, about; and kardia, the heart). This secretes a lubricating fluid, and is smooth as satin.
THE MOVEMENTS OF THE HEART consist of an alternate contraction and expansion. The former is called the sys'-to-le, and the latter the di-as'-to-le. During the diastole, the blood flows into the heart, to be expelled by the systole. The alternation of these movements constitutes the beating of the heart which we hear so distinctly between the fifth and sixth ribs. [Footnote: Two sounds are heard if we put our ear over the heart,—the first and longer as the blood is leading the organ, the second as it falls into the pockets of the two arteries, and the valves then striking together cause it. The first sound is mainly the noise made by the muscular tissue. During the first, the two ventricles contract; during the second the two auricles do so. The hand may feel the heart striking the ribs as it contracts,—a feeling called the impulse, or, if quicker and stronger than usual, palpitation. This is not always a sign of disease, but in hypochondriacs is often an effect of the mind on the nerves of the heart.—MAPOTHER]
FIG. 38.
[Illustration: Chambers of the Heart A, right ventricle; B, left ventricle, C, right auricle, D, left auricle, E, tricuspid valve, F, bicuspid valve; G, semilunar valves, H, valve of the aorta; I, inferior vena cava, K, superior vena cava, L, L, pulmonary veins.]
THE AURICLES AND VENTRICLES—The heart is divided into four chambers. In an adult, each holds about a wineglassful. The upper ones, from appendages on the outside resembling the ears of a dog, are called auricles (aures, ears). are termed ventricles. The auricle and ventricle on each side communicate with each other, but the right and left halves of the heart are entirely distinct, and perform different offices. The left side propels the red blood; and the right, the dark. The auricles are merely reservoirs to receive the blood (the left auricle, as it filters in bright and pure from the lungs; the right, as it returns dark and foul from the tour of the body), and to furnish it to the ventricles as they need. Their work being so light, their walls are comparatively thin and weak. On the other hand, the ventricles force the blood (the left, to all parts of the body; the right, to the lungs), and are, therefore, made very strong. As the left ventricle drives the blood so much farther than the right, it is correspondingly thicker and stronger.
NEED OF VALVES IN THE HEART.—As the auricles do not need to contract with much force simply to empty their contents into the ventricles below them, there is no demand for any special contrivance to prevent the blood from setting back the wrong way. Indeed, it would naturally run down into the ventricle, which is at that moment open to receive it. But, when the strong ventricles contract, especially the left one, which must drive the blood to the extremities, some arrangement is necessary to prevent it from returning into the auricle. Besides, when they expand, the "suction power" would tend to draw back again from the arteries all the blood just forced out. This difficulty is obviated by means of little doors, or valves, which will not let it go the wrong way. [Footnote: The heart of an ox or a sheep may be used to show the chambers and valves. The aorta should be cut as far as possible from the heart, and then by pumping in water the perfection of these valves will be finely exhibited. Cutting the heart across near the middle will show the greater thickness of the left ventricle.]
THE TRICUSPID AND BICUSPID VALVES.—At the opening into the right ventricle, is a valve consisting of three folds or flaps of membrane, whence it is called the tricuspid valve (tri, three; and cuspides, points), and in the left ventricle, one containing two flaps, and named the bicuspid valve. These hang so loosely as to oppose no resistance to the passage of the blood into the ventricles; but, if any attempts to go the other way, it gets between the flaps and the walls of the heart, and, driving them outward, closes the orifice.
FIG. 39.
[Illustration: Diagram showing the peculiar Fibrous Structure of the Heart and the Shape of the Valves. A, tricuspid valve, B, bicuspid valve; C, semilunar valves of the aorta; D, semilunar valves of the pulmonary artery.]
THESE FLAPS ARE STRENGTHENED like sails by slender cords, which prevent their being pressed back through the opening. If the cords were attached directly to the walls of the heart, they would be loosened in the systole, and so become useless when most needed. They are, therefore, fastened to little muscular pillars projecting from the sides of the ventricle; when that contracts, the pillars contract also, and thus the cords are held tight.
THE SEMILUNAR VALVES.—In the passages outward from the ventricles, are valves, called from their peculiar half-moon shape semilunar valves (semi, half; Luna, Moon). Each consists of three little pocket-shaped folds of membrane, with their openings in the direction which the blood is to take. When it sets back, they fill, and, swelling out, close the passage (Fig. 40).
THE ARTERIES [Footnote: Aer, air; and tereo, I contain—so named because after death they contain air only, and hence the ancients supposed them to be air tubes leading through the body.] are the tube-like canals which convey the blood from the heart. They carry the red blood (see note, p. 119). They are composed of an elastic tissue, which yields at every throb of the heart, and then slowly contracting again, keeps up the motion of the blood until the next systole. The elasticity of the arteries acts like the air chamber of a fire engine, which converts the intermittent jerks of the brakes or pump into the steady stream of the hose nozzle.
The arteries sometimes communicate by means of branches or by meshes of loops, so that if the blood be blocked in one, it can pass round through another, and so get by the obstacle. [Footnote: This occurs especially about the joints, where it serves to maintain the circulation during the bending of a limb, or when the main artery is obstructed by disease or injury, or has been tied by the surgeon. In the last case, the small adjacent arteries gradually enlarge, and form what is called a collateral circulation.] When an artery penetrates a muscle, it is often protected by a sheath or by fibrous rings, which prevent its being pulled out of place or compressed by the play of the muscles.
The arteries are generally located as far as possible beneath the surface, out of harm's way, and hence are found closely hugging the bones or creeping through safe passages provided for them. They are generally nearly straight, and take the shortest routes to the parts which they are to supply with blood.
THE ARTERIAL SYSTEM starts from the left ventricle by a single trunk—the aorta—which, after giving off branches to the head, sweeps back of the chest with a bold curve—the arch of the aorta (c, Fig. 34)—and thence runs downward (f), dividing and subdividing, like a tree, into numberless branches, which, at last, penetrate every nook and corner of the body.
THE PULSE.—At the wrist (k, radial artery) and on the temple (temporal artery) we can feel the expansion of the artery by each little wave of blood set in motion by the contraction of the heart. In health, there are about seventy-two [Footnote: This number varies much with age, sex, and individuals. Napoleon's pulse is said to have been only forty, while it is not infrequent to find a healthy pulse at one hundred or over. In general, the pulse is quicker in children and in old people than in the middle-aged; in short persons than in tall; in women than in men. Shame makes the heart send more blood to the blushing cheek, and fear almost stops it. The will can not check the heart. There is said, however, to have been a notable exception to this in the case of one Colonel Townsend, of Dublin, who, after having succeeded several times in stopping the pulsation, at last lost his life in the act.] pulsations per minute. They increase with excitement or inflammation, weaken with loss of vigor, and are modified by nearly every disease. The physician, therefore, finds the pulse a good index of the state of the system and the character of the disorder. (See p. 314.)
THE VEINS are the tube-like canals which convey the blood to the heart. [Footnote: There is one exception to the general course of the veins. The portal vein carries the blood from the digestive organs to the liver, where it is acted upon, thence poured into the ascending vena cava, and goes back to the heart.] They carry the dark or venous blood (note, p. 119). As they do not receive the direct impulse of the heart, their walls are made much thinner and less elastic than those of the arteries. At first small, they increase in size and diminish in number as they gradually pour into one another, like tiny rills collecting to form two rivers, the vena cava ascending and the vena cava descending (l, m, Fig. 34), which empty into the right auricle.
Some of the veins creep along under the skin, where they can be seen, as in the back of the hand; while others accompany the arteries, some of which have two or more of these companions.
VALVES similar in construction to those already described (the semilunar valves of the heart, page 114) are placed at convenient intervals, in order to guide the blood in its course, and prevent its setting backward. [Footnote: Too much standing, or tight elastics, often cause the veins in the leg to swell, so that the valves can not work; the veins then become varicose, or permanently enlarged, and, if they burst, the bleeding may be profuse and even dangerous. Raising the leg and pressing the finger on the bleeding spot will stay it. Walking does not encourage this disease, for the active muscles force on the venous blood. Clerks who are subject to varicose veins should have seats behind the counters where they may rest when not actually employed. A deep breath helps the flow in the veins, and a wound may suck in air with fatal effect. A maimed horse is most mercifully killed by blowing a bubble of air into the veins of his neck. As the deep-sea pressure would burst valves, the whale has none; hence a small wound by the harpoon causes him to bleed to death.— MAPOTHER.] We can easily examine the working of these valves. On baring the arm, blue veins may be seen running along the arm toward the hand. Their diameter is tolerably even, and they gradually decrease in size. If now the finger be pressed on the upper part of one of these veins, and then passed downward so as to drive its blood backward, swellings like little knots will make their appearance. Each of these marks the location of a valve, which is closed by the blood we push before our finger. Remove the pressure, and the valve will swing open, the blood set forward, and the vein collapse to its former size.
FIG. 40.
[Illustration: Valves of the Veins.]
THE CAPILLARIES (capillus, a hair) form a fine network of tubes, connecting the ends of the arteries with the veins. They blend, however, with the extremities of these two systems, so that it is not easy to tell just where an artery ends and a vein begins. So closely are they placed, that we can not prick the flesh with a needle without injuring, perhaps, hundreds of them. The air cells of the blood deposit there their oxygen, and receive carbonic acid, while in the delicate capillaries of the lungs [Footnote: The capillary tubes are there so fine that the disks of the blood have to go one by one, and are sadly squeezed at that. However, their elasticity enables them to resume their old shape as soon as they have escaped from this labyrinth.] they give up their load of carbonic acid in exchange for oxygen.
FIG. 41.
[Illustration: Circulation of the Blood in the Web of a Frog's Foot, highly magnified. A, an artery; B, capillaries crowded with disks, owing to a rupture just above, where the disks are jammed into an adjacent mesh; C, a deeper vein; the black spots are pigment cells.]
If, by means of a microscope, we examine the transparent web of a frog's foot, we can trace the route of the blood. [Footnote: With small splints and twine, a frog's foot can be easily stretched and tied so that the transparent web can be placed on the table of the microscope.] It is an experiment of wonderful interest. The crimson stream, propelled by the heart, rushes through the arteries, until it reaches the intricate meshes of the capillaries. Here it breaks into a thousand tiny rills. We can see the disks winding in single file through the devious passages, darting hither and thither, now pausing, swaying to and fro with an uncertain motion, and anon dashing ahead, until, at last, gathered in the veins, the blood sets steadily back on its return to the heart.
THE CIRCULATION [Footnote: The circulation of the blood was discovered by 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.]