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A Treatise on Anatomy, Physiology, and Hygiene (Revised Edition)
by Calvin Cutter
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488. What is formed when oxygen unites with carbon or hydrogen? 489. Give the theory for the formation of carbonic acid and watery vapor thrown out of the system. 490. Illustrate the passage of fluids through membranes, and the different affinities of gases.

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491. The walls of the air-vesicles, and coats of the blood-vessels, are similar, in their mechanical arrangement, to the membranous bladder in the before described experiment. As the oxygen of the air has greater affinity for blood than for nitrogen, so it permeates the membranes that intervene between the air and blood more readily than the nitrogen. As the carbonic acid and water have a greater affinity for air than for the other elements of the blood, so they will also pass through the walls of the blood-vessels and air-cells more readily than the other elements of the dark-colored blood.



492. As the impure blood is passing in the minute vessels over the air-cells, the oxygen passes through the thin coats of the air-cells and blood-vessels, and unites with the blood. At the same time, the carbonic acid and water leave the blood, and pass through the coats of the blood-vessels and air-cells, and mix with the air in the cells. These are thrown out of the system every time we breathe. This interchange of products produces the change in the color of the blood.

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Explain fig. 98. 492. How and where is the blood changed?

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Experiment. Fill a bladder with dark blood drawn from any animal. Tie the bladder closely, and suspend it in the air. In a few hours, the blood next to the membrane will have become of a bright red color. This is owing to the oxygen from the air passing through the bladder, and uniting with the blood, while the carbonic acid has escaped through the membrane.



493. The presence of carbonic acid and watery vapor in the expired air, can be proved by the following experiments: 1st. Breathe into lime-water, and in a few minutes it will become of a milk-white color. This is owing to the carbonic acid of the breath uniting with the lime, forming the carbonate of lime. 2d. Breathe upon a cold, dry mirror for a few minutes, and it will be covered with moisture. This is condensed vapor from the lungs. In warm weather, this watery vapor is invisible in the expired air, but in a cold, dry morning in winter, the successive jets of vapor issuing from the mouth and nose are sufficiently obvious.

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Give the experiment showing that oxygen changes the dark-colored blood to a bright red color. What is represented by fig. 99? 493. How can the presence of carbonic acid in the lungs be proved?

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494. From the lungs are eliminated other impurities beside carbonic acid, the perceptible quality of which is various in different persons. The offensive breath of many persons may be caused by decayed teeth, or the particles of food that may be retained between them, but it often proceeds from the secretion, in the lungs, of certain substances which previously existed in the system.

Illustration. When spirituous liquors are taken into the stomach, they are absorbed by the veins and mixed with the dark-colored blood, in which they are carried to the lungs to be expelled from the body. This will explain the fact, which is familiar to most persons, that the odor of different substances is perceptible in the breath, or expired air, long after the mouth is free from these substances.

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How the watery vapor? 494. Are there other excretions from the lungs? Give the illustration.

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Note. Let the anatomy and physiology of the respiratory organs be reviewed from figs. 96, 97, and 99, or from anatomical outline plates Nos. 5 and 7.



CHAPTER XXV.

HYGIENE OF THE RESPIRATORY ORGANS.

495. For man to enjoy the highest degree of health, it is necessary that the impure "venous" blood be properly changed. As this is effected in the lungs by the action of the air, it follows that this element, when breathed, should be pure, or contain twenty-one per cent. of oxygen to about seventy-nine per cent. of nitrogen.

496. The volume of air expelled from the lungs is somewhat less than that which is inspired. The amount of loss varies under different circumstances. An eightieth part of the volume taken into the lungs, or half a cubic inch, may be considered an average estimate.

497. The quality and purity of the air is affected by every respiration. 1st. The quantity of oxygen is diminished. 2d. The amount of carbonic acid is increased. 3d. A certain proportion of watery vapor is ejected from the lungs in the expired air. Of the twenty-one parts of oxygen in the inspired air, only eighteen parts are expired, while the carbonic acid and watery vapor are increased about four per cent. The quantity of nitrogen is nearly the same in the expired as in the inspired air.

Observation. It is now fully ascertained that while the chemical composition of the blood is essentially changed, its weight remains the same, as the carbon and hydrogen discharged are equal to the united weight of the oxygen and nitrogen absorbed.

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495-546. Give the hygiene of the respiratory organs. 495. What is necessary that man enjoy the highest degree of health? 496. How does the volume Of expired air compare with that which was inspired? Does this loss vary, and what is an average estimate? 497. How is the purity of the air affected by respiration? How is the inhaled oxygen affected? What effect on the carbonic acid and watery vapor? On the nitrogen? What is said respecting the weight of the blood?

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498. If one fourth part of the volume of air received by the lungs at one inspiration is decomposed at one "beat" of the heart, it might be supposed that if the expired air be again received into the lungs, one half of the oxygen would be consumed, and, in a similar ratio, if re-breathed four times, all the oxygen would be consumed. But it does not follow, if the air is thus re-breathed, that the same changes will be effected in the lungs. For air that has been inspired does not part with its remaining oxygen as freely as when it contains the proper amount of this life-giving element, and thus the changes in the impure blood are not so completely effected.

Illustration. In the process of dyeing, each successive article immersed in the dye weakens it; but it does not follow that the dye each time is affected in the same degree, or that the coloring matter by repeated immersions can be wholly extracted. The same principle applies to the exchange of oxygen and carbonic acid gas in the lungs.

499. If the inspired air is free from moisture and carbonic acid, these substances contained in the blood will be more readily imparted to it. When the air is loaded with vapor, they are removed more slowly; but if it is saturated with moisture, no vapor will escape from the blood through the agency of the lungs. This may be illustrated by the following experiment: Take two and a half pounds of water, add to it half a pound of common salt, (chloride of sodium,) and it will readily mix with the water; and to this solution add the same quantity of salt, and it will be dissolved more slowly. Again, add more salt, and it will remain undissolved, as the water has become saturated by the pound before dissolved.

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498. Does air that is re-breathed freely impart its oxygen? Why? 499. What is the effect on the blood when the air is free from vapor and carbonic acid? When loaded with vapor? When saturated? How is this illustrated?

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500. The principle in this experiment is analogous to that of the union between carbonic gas and atmospheric air. Allen and Pepy showed by experiment, that air which had been once breathed, contained eight and a half per cent. of carbonic acid. They likewise showed, that no continuance of the respiration of the same air could make it take up more than ten per cent. This is the point of saturation.

Experiment. Sink a glass jar that has a stop-cock, or one with a glass stopper, into a pail of water, until the air is expelled from the jar. Fill the lungs with air, and retain it in the chest a short time, and then breathe into the jar, and instantly close the stop-cock. Close the opening of the jar that is under the water with a piece of paper laid on a plate of sufficient size to cover the opening, invert the jar, and sink into it a lighted candle. The flame will be extinguished as quickly as if put in water.[15] Remove the carbonic acid by inverting the jar, and place a lighted candle in it, and the flame will be as clear as when out of the jar.

[15] As a substitute for a jar with a stop-cock, take a piece of lead pipe bent in the form of a siphon, and insert it in the mouth of a reversed jar. This experiment is as conclusive whether the air is inhaled once only or breathed many times.

Observations. 1st. It is familiarly known that a taper will not burn where carbonic acid exists in any considerable quantity, or when there is a marked deficiency of oxygen. From this originated the judicious practice of sinking a lighted candle into a well or pit before descending into it. If the flame is extinguished, respiration cannot there be maintained, and life would be sacrificed should a person venture in, until the noxious air is removed.

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500. What did the experiments of Allen and Pepy show? How can the presence of carbonic gas in the expired air be demonstrated? State observation 1st. Observation 2d.

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2d. It is the action of carbonic acid upon the respiratory organs, that gives rise to a phenomenon frequently seen in mines and caves. A man may enter these subterranean rooms, and feel no inconvenience in breathing; but the dog that follows him, falls apparently dead, and soon dies if not speedily removed to pure air. This arises from the fact that this gas is heavier than air, and sinks to the bottom of the room or cave.

3d. While it is true that carbonic acid possesses properties that render it unfit to be breathed, it is, notwithstanding, productive of very agreeable effects, when conveyed into the stomach. It forms the sparkling property of mineral waters, and fills the bubbles that rise when beer or cider is fermenting.

501. Pure atmospheric air is best adapted to a healthy action of the system. As the air cannot be maintained pure under all circumstances, the question may be asked, To what degree may the air be vitiated and still sustain life? and what is the smallest quantity of pure air a person needs each minute to maintain good health? Birnan says, that air which contains more than three and a half per cent. of carbonic acid is unfit for respiration, and, as air once respired contains eight and a half per cent. of carbonic acid, it clearly shows that it is not fitted to be breathed again.

502. No physiologist pretends that less than seven cubic feet of air are adequate for a man to breathe each minute, while Dr. Reid allows ten feet. The necessity of fifteen or twenty times the amount of air actually taken into the lungs, arises from the circumstance, that the expired air mixes with and vitiates the surrounding element that has not been inhaled.

503. The quantity of air which different persons actually need, varies. The demand is modified by the size, age, habits, and condition of the body. A person of great size who has a large quantity of blood, requires more air than a small man with a less amount of circulating fluid. Individuals whose labor is active, require more air than sedentary or idle persons, because the waste of the system is greater. On the same principle, the gormandizer needs more of this element than the person of abstemious habits. So does the growing lad require more air than an adult of the same weight, for the reason that he consumes more food than a person of mature years. Habit also exerts a controlling influence. A man who works in the open air suffers more when placed in a small, unventilated room, than one who is accustomed to breathe the confined air of workshops.

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Observation 3d. 501. What questions may be asked respecting the inspired air? Give the remark of Birnan. 502. How many cubic feet of air are adequate for a man to breathe each minute? How much does Dr. Reid allow? 503. Mention some reasons why different persons do not require the same amount of air.

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504. Air, in which lamps will not burn with brilliancy, is unfitted for respiration. In crowded rooms, which are not ventilated, the air is vitiated, not only by the abstraction of oxygen and the deposition of carbonic acid, but by the excretions from the skin and lungs of the audience. The lamps, under such circumstances, emit but a feeble light. Let the oxygen gas be more and more expended, and the lamps will burn more and more feebly, until they are extinguished.

Illustrations. 1st. The effects of breathing the same air again and again, are well illustrated by an incident that occurred in one of our halls of learning. A large audience had assembled in an ill-ventilated room, to listen to a lecture; soon the lamps burned so dimly that the speaker and audience were nearly enveloped in darkness. The oppression, dizziness, and faintness experienced by many of the audience induced them to leave, and in a few minutes after, the lamps were observed to rekindle, owing to the exchange of pure air on opening the door.

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How is it with the laborer? With the gormandizer? With the person that works in the open air? 504. What effect has impure air on a burning lamp? Give the illustration of the effects of impure air on lighted lamps.

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2d. In the "Black Hole of Calcutta," one hundred and forty-six Englishmen were shut up in a room eighteen feet square, with only two small windows on the same side to admit air. On opening this dungeon, ten hours after their imprisonment, only twenty-three were alive. The others had died from breathing impure air.

505. Air that has become impure from the abstraction of oxygen, an excess of carbonic acid, or the excretions from the lungs and skin, has a deleterious effect on the body. When this element is vitiated from the preceding causes, it prevents the proper arterialization, or change in the blood. For this reason, pure air should be admitted freely and constantly into work-shops and dwelling-houses, and the vitiated air permitted to escape. This is of greater importance than the warming of these apartments. We can compensate for the deficiency of a stove, by an extra garment or an increased quantity of food; but neither garment, exercise, nor food will compensate for pure air.

506. School-rooms should be ventilated. If they are not, the pupils will be restless, and complain of languor and headache. Those unpleasant sensations are caused by a want of pure air, to give an adequate supply of oxygen to the lungs. When pupils breathe for a series of years such vitiated air, their life is undoubtedly shortened, by giving rise to consumption and other fatal diseases.

Illustration. A school-room thirty feet square and eight feet high, contains 7200 cubic feet of air. This room will seat sixty pupils, and, allowing ten cubic feet of air to each pupil per minute, all the air in the room will be vitiated in twelve minutes.

Observation. In all school-rooms where there is not adequate ventilation, it is advisable to have a recess of five or ten minutes each hour. During this time, let the pupils breathe fresh air, and open the doors and windows, so that the air of the room shall be completely changed.

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Of the effects of breathing impure air. 505. In preserving health, what is of greater importance than warming the room? 506. Why should a school-room be ventilated? Give the illustration.

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507. Churches, concert halls, and all rooms designed for a collection of individuals, should be amply ventilated. While the architect and workmen are assiduous in giving these public rooms architectural beauty and splendor, by adorning the ceiling with Gothic tracery, rearing richly carved columns, and providing carefully for the warming of the room, it too frequently happens that no direct provision is made for the change of that element which gives us beauty, strength, and life.

Illustration. A hall sixty feet by forty, and fifteen feet high, contains 36,000 cubic feet of air. A hall of this size will seat four hundred persons; by allowing ten cubic feet of air to each person per minute, the air of the room will be rendered unfit for respiration in nine minutes.

508. Railroad cars, cabins of steam and canal-boats, omnibuses, and stage-coaches, require ample ventilation. In the construction of these public conveyances, too frequently, the only apparent design is, to seat the greatest number of persons, regardless of the quantity and character of the air to maintain health and even life. The character of the air is only realized when, from the fresh, pure air, we enter a crowded cabin of a boat or a closed coach; then the vitiated air from animal excretions and noxious gases is offensive, and frequently produces sickness.

509. The influence of habit is strikingly expressed by Birnan, in the "Art of Warming and Ventilating Rooms:" "Not the least remarkable example of the power of habit is its reconciling us to practices which, but for its influence, would be considered noxious and disgusting. We instinctively shun approach to the dirty, the squalid, and the diseased, and use no garment that may have been worn by another. We open sewers for matters that offend the sight or the smell, and contaminate the air. We carefully remove impurities from what we eat and drink, filter turbid water, and fastidiously avoid drinking from a cup that may have been pressed to the lips of a friend. On the other hand, we resort to places of assembly, and draw into our mouths air loaded with effluvia from the lungs, skin, and clothing of every individual in the promiscuous crowd—exhalations offensive, to a certain extent, from the most healthy individuals; but when arising from a living mass of skin and lungs, in all stages of evaporation, disease, and putridity,—prevented by the walls and ceiling from escaping—they are, when thus concentrated, in the highest degree deleterious and loathsome."

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What suggestion when a school-room is not ventilated? 507. What is said in regard to ventilating churches, concert halls, &c.? State the illustration. 508. What remarks relative to public conveyances? 509. State the influence of habit by Birnan.

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510. The sleeping-room should be so ventilated that the air in the morning will be as pure as when retiring to rest in the evening. Ventilation of the room would prevent morning headaches, the want of appetite, and languor—so common among the feeble. The impure air of sleeping-rooms probably causes more deaths than intemperance. Look around the country, and those who are most exposed, who live in huts but little superior to the sheds that shelter the farmer's flocks, are found to be the most healthy and robust. Headaches, liver complaints, coughs, and a multitude of nervous affections, are almost unknown to them; not so with those who spend their days and nights in rooms in which the sashes of the windows are calked, or perchance doubled, to prevent the keen but healthy air of winter from entering their apartments. Disease and suffering are their constant companions.

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510. What is said of the ventilation of sleeping-rooms? What would adequate ventilation prevent? Give a common observation.

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Illustration. By many, sleeping apartments twelve feet square and seven feet high, are considered spacious for two persons, and good accommodations for four to lodge in. An apartment of this size contains 1008 cubic feet of air. Allowing ten cubic feet to each person per minute, two occupants would vitiate the air of the room in fifty minutes, and four in twenty-five minutes. When lodging-rooms are not ventilated, we would strongly recommend early rising.

511. The sick-room, particularly, should be so arranged that the impure air may escape, and pure air be constantly admitted into the room. It is no unusual practice in some communities, when a child or an adult is sick of an acute disease, to prevent the ingress of pure air, simply from the apprehension of the attendants, that the patient will contract a cold. Again, the prevalent custom of several individuals sitting in the sick-room, particularly when they remain there for several hours, tends to vitiate the air, and, consequently, to increase the suffering and danger of the sick person. In fevers or inflammatory diseases of any kind, let the patient breathe pure air; for the purer the blood, the greater the power of the system to remove disease, and the less the liability to contract colds.

Observation. Among children, convulsions, or "fits," usually occur when they are sleeping. In many instances, these are produced by the impure air which is breathed. To prevent these alarming and distressing convulsions, the sleeping-room should be ventilated, and there should be no curtains around the bed, or coverings over the face, as they produce an effect similar to that experienced when sleeping in a small, unventilated room. To relieve a child when convulsed, carry it into the open air.

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What is said of the size of sleeping-rooms? 511. What is said of the sick-room? Mention some prevailing customs in reference to these rooms. What is said of convulsions among children?

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512. While occupying a room, we are insensible of the gradual vitiation of the air. This is the result of the diminished sensibility of the nervous system, and gradual adaptation of the organs to blood of a less stimulating character. This condition is well illustrated in the hibernating animals. We are insensible of the impure air of unventilated sleeping-rooms, until we leave them for a walk or ride. If they have been closed, we are made sensible of the character of the air as soon as we reenter them, for the system has regained its usual sensibility while inhaling a purer atmosphere.

513. In the construction of every inhabited room, there should be adequate means of ventilation, as well as warming. No room is well ventilated, unless as much pure air is brought into it as the occupants vitiate at every respiration. This can be effected by making an aperture in the ceiling of the room, or by constructing a ventilating flue in the chimney. This should be in contact with the flues for the escape of smoke, but separated from them by a thin brick partition. The hot air in the smoke flues will warm the separating brick partition, and consequently rarefy the air in the ventilating flue. Communication from every room in a house should be had to such flues. The draught of air can be regulated by well-adjusted registers, which in large rooms should be placed near the floor as well as near the ceiling.

514. While provision is made for the escape of rarefied impure air, we should also provide means by which pure air may be constantly admitted into the room, as the crevices of the doors and windows are not always sufficient; and, if they should be adequate, air can be introduced in a more convenient, economical, and appropriate manner. There should be an aperture opposite the ventilating flue, at or near the floor, to connect with the outer walls of the building or external air. But if pure heated air is introduced into the room, it obviates the necessity of the introduction of the external air.[16]

[16] Mr. Frederick Emerson, of Boston, has devised a simple and effective apparatus for removing vitiated air from a room. It is successfully used upon all the public school-houses of Boston. It is now being generally applied to the school-houses and other public buildings, as well as private dwellings, of New England.

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512. Why are we insensible to the gradual vitiation of the air of an unventilated room? 513. What is very important in the building of every inhabited room? How can a room be well ventilated? 514. What is said relative to a communication with the external air?

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515. In warming rooms, the hot air furnaces, or box and air-tight stoves converted into hot air furnaces, should be used in preference to the ordinary stoves. The air thus introduced into the room is pure as well as warm. In the adaptation of furnaces to dwelling-houses, &c., it is necessary that the air should pass over an ample surface of iron moderately heated; as a red heat abstracts the oxygen from the contiguous air, and thus renders it unfit to be respired.[17]

[17] Dr. Wyman's valuable work on "Ventilation," and the work of Henry Barnard, Esq., on "School-house architecture," can be advantageously consulted, as they give the practical methods of ventilating and warming shops, school-rooms, dwelling-houses, public halls, &c.

Observation. Domestic animals need a supply of pure air as well as man. The cows of cities, that breathe a vitiated air, have, very generally, tubercles. Sheep that are shut in a confined air, die of a disease called the "rot," which is of a tuberculous character. Interest and humanity require that the buildings for animals be properly ventilated.

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515. How should rooms be warmed? What is necessary in the adaptation of furnaces to dwelling-houses?

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CHAPTER XXVI.

HYGIENE OF THE RESPIRATORY ORGANS, CONTINUED.

516. The change that is effected in the blood while passing through the lungs, not only depends upon the purity of the air, but the amount inspired. The quantity varies according to the size of the chest, and the movement of the ribs and diaphragm.

517. The size of the chest and lungs can be reduced by moderate and continued pressure. This is most easily done in infancy, when the cartilages and ribs are very pliant; yet it can be effected at more advanced periods of life, even after the chest is fully developed. For want of knowledge of the pliant character of the cartilages and ribs in infants, too many mothers, unintentionally, contract their chests, and thus sow the seeds of disease by the close dressing of their offspring.

518. If slight but steady pressure be continued from day to day and from week to week, the ribs will continue to yield more and more, and after the expiration of a few months, the chest will become diminished in size. This will be effected without any suffering of a marked character; but the general health and strength will be impaired. It is not the violent and ephemeral pressure, but the moderate and protracted, that produces the miscalled, "genteel," contracted chests.

519. The style of dress which at the present day is almost universal, is a prolific cause of this deformity. These baneful fashions are copied from the periodicals, so widely circulated, containing a "fashion plate of the latest fashions, from Paris." In every instance; the contracted, deformed, and, as it is called, lady-like waist, is portrayed in all its fascinating loveliness. These periodicals are found on almost every centre-table, and exercise an influence almost omnipotent. If the plates which corrupt the morals are excluded by civil legislation, with the same propriety ought not those to be suppressed that have a tendency so adverse to health?

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516. What varies the amount of air received into the lungs? 517. How can the size of the chest be diminished? When is this most easily effected? 518. How are the miscalled, "genteel," contracted chests usually produced? 519. What is said of the style of the dress at the present day?

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Observations. 1st. The Chinese, by compressing the feet of female children, prevent their growth; so that the foot of a Chinese belle is not larger than the foot of an American girl of five years.

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What does fig. 100 represent? Fig. 101? Give observation 1st.

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2d. The American women compress their chests, to prevent their growth; so that the chest of an American belle is not larger than the chest of a Chinese girl of five years. Which country, in this respect, exhibits the greater intelligence?

3d. The chest can be deformed by making the linings of the waists of the dresses tight, as well as by corsets. Tight vests, upon the same principle, are also injurious.

520. In children, who have never worn close garments, the circumference of the chest is generally about equal to that of the body at the hips; and similar proportions would exist through life, if there were no improper pressure of the clothing. This is true of the laboring women of the Emerald Isle, and other countries of Europe, and in the Indian female, whose blanket allows the free expansion of the chest. The symmetrical statues of ancient sculptors bear little resemblance to the "beau ideal" of American notions of elegant form. This perverted taste is in opposition to the laws of nature. The design of the human chest is not simply to connect the upper and lower portions of the body, like some insects, but to form a case for the protection of the vital organs.

521. Individuals may have small chests from birth. This, to the particular individual, is natural; yet it is adverse to the great and general law of Nature relative to the size of the human chest. Like produces like, is a general law of the animal and vegetable kingdoms. No fact is better established, than that which proves the hereditary transmission from parents to children of a constitutional liability to disease and the same may be said in regard to their conformations. If the mother has a small, taper waist, either hereditary or acquired, this form may be impressed on her offspring;—thus illustrating the truthfulness of scripture, "that the sins of the parents shall be visited upon the children unto the third and fourth generation."

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Observation 2d. Observation 3d. 520. What is the size of the chest of a child that has always worn loose clothing? What is said of the size of the laboring women of Ireland, and the Indian female? How is it in ancient statues? What is the design of the chest? 521. What is a general law of both the animal and vegetable kingdoms? What fact in this connection is well established?

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522. The quantity of air inhaled is modified by the capacity of the respiratory organs. The necessity of voluminous lungs may he elucidated by the following experiment: Suppose a gill of alcohol, mixed with a gill of water, be put into a vessel having a square foot of surface, and over the vessel a membrane be tied, and that the water will evaporate in twenty-four hours. If the surface had been only six inches square, only one fourth of the water would have evaporated through the membrane in the given time. If the surface had been extended to two square feet, the water would have evaporated in twelve hours.

523. Apply this principle to the lungs: suppose there are two hundred feet of carbonic acid to be carried out of the system every twenty-four hours. This gas, in that time, will pass through a vesicular membrane of two thousand square feet. If the lungs were diminished in size, so that there would be only one thousand square feet of vesicular membrane, the amount of carbonic acid would not, and could not, be eliminated from the system. Under such circumstances, the blood would not be purified.

524. Again; suppose the two thousand square feet of membrane would transmit two hundred cubic feet of oxygen into the system every twenty-four hours. If it should be diminished one half, this amount of oxygen would not pass into the blood. From the above illustrations we may learn the importance of well-developed chests and voluminous lungs; for, by increasing the size of the lungs, the oxygen is more abundantly supplied to the blood, and this fluid is more perfectly deprived of its carbon and hydrogen.

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What does this hereditary transmission prove? 522. How is the necessity of voluminous lungs illustrated? 525. How is this principle applied to the interchange of products in the lungs?

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525. The chest is not only most expanded at its lower part, but the portion of the lungs that occupies this space of the thoracic cavity contains the greater part of the air-cells; and, from the lower two thirds of the lungs the greatest amount of carbonic acid is abstracted from the blood, and the greatest amount of oxygen gas is conveyed into the circulating fluid. Hence, contracting the lower ribs is far more injurious to the health than diminishing the size of the upper part of the chest.

526. The question is often asked, Can the size of the chest and the volume of the lungs be increased, when they have been injudiciously compressed, or have inherited this unnatural form? The answer is in the affirmative. The means for attaining this end are, a judicious exercise of the lungs, by walking in the open air, reading aloud, singing, sitting erect, and fully inflating the lungs at each act of inspiration. If the exercise be properly managed and persevered in, it will expand the chest, and give tone and health to the important organs contained in it. But, if the exercise be ill-timed or carried to excess, the beneficial results sought will probably not be attained.

Observation. Scholars, and persons who sit much of the time, should frequently, during the day, breathe full and deep, so that the smallest air-cells may be fully filled with air. While exercising the lungs, the shoulders should be thrown back and the head held erect.

527. The movement of the ribs and diaphragm is modified by the dress. When the lungs are properly filled with air, the chest is enlarged in every direction. If any article of apparel is worn so tight as to prevent the full expansion of the chest and abdomen, the lungs, in consequence, do not receive air sufficient to purify the blood. The effect of firm, unyielding clothing, when worn tight, in preventing a due supply of air to the lungs, may be shown by the following illustration.

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525. Why is it more injurious to contract the lower part of the chest than the upper? 526. How can the size of the chest be increased when it is contracted? Give the observation. 527. How is the movement of the ribs and diaphragm modified?

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Illustration. If the diameter of a circle is three feet, the circumference will be nine feet. If the diameter is extended to four feet, the circumference will be increased to twelve feet. Should a tight band be thrown around a circle of nine feet, its diameter cannot be increased, for the circumference cannot be enlarged.

528. Any inelastic band, drawn closely around the lower part of the chest, or the abdomen, below the ribs, operates like the band in the preceding illustration, in restricting the movement of the ribs. When any article of dress encircles either the chest or abdomen, so as to prevent an increase of its circumference, it has an injudicious tendency, as it prevents the introduction of air in sufficient quantities to purify the blood. The question is not, How much restriction of the respiratory movements can be endured, and life continue? but, Does any part of the apparel restrict the movements? If it does, it is a violation of the organic laws; and though Nature is profuse in her expenditures, yet sooner or later, she sums up her account.

529. In determining whether the apparel is worn too tight, inflate the lungs, and, if no pressure is felt, no injurious effects need be apprehended from this cause. In testing the tightness of the dress, some persons will contract to the utmost the abdominal muscles, and thus diminish the size of the chest, by depressing the ribs; when this is done, the individual exclaims, "How loose my dress is!" This practice is both deceptive and ludicrous. A good test is, to put the hand on the chest below the arm; if there is no movement of the ribs during respiration, the apparel is too tight. The only reliable test, however, is a full inflation of the lungs.

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How is the effect of unyielding clothing, when worn tight, illustrated? 528. What effect has an inelastic band upon the lower part of the chest? What question is asked? 529. How can we determine whether the apparel is worn too tight?

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Observation. Many individuals do not realize the small amount of force that will prevent the enlargement of the chest. This can be demonstrated by drawing a piece of tape tightly around the lower part of the chest of a vigorous adult, and confining it with the thumb and finger. Then endeavor fully to inflate the lungs, and the movement of the ribs will be much restricted.

530. The position in standing and sitting influences the movement of the ribs and diaphragm. When the shoulders are thrown back, and when a person stands or sits erect, the diaphragm and ribs have more freedom of motion, and the abdominal muscles act more efficiently; thus the lungs have broader range of movement than when the shoulders incline forward, and the body is stooping.

531. Habit exercises an influence upon the range of the respiratory movements. A person who has been habituated to dress loosely, and whose inspirations are full and free, suffers more from the tightness of a vest or waistband, than one, the range of movements of whose chest has long been subjected to tight lacing.

532. The condition of the brain exercises a great influence upon respiration. If the brain is diseased, or the mind depressed by grief, tormented by anxiety, or absorbed by abstract thought, the contractile energy of the diaphragm and muscles that elevate the ribs, is much diminished, and the lungs are not so fully inflated, as when the mind is influenced by joy or other exhilarating emotions. The depressing passions likewise lessen the frequency of respiration. By the influence of these causes, the blood is but partially purified, and the whole system becomes enfeebled. Here we may see the admirable harmony between the different parts of the body, and the adaptation of all the functions to each other.

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Give another test. How can the amount of pressure necessary to prevent the enlargement of the chest be demonstrated? 530. Show the effect of position on the movements of the ribs and diaphragm. 531. Show the effect of habit on the respiratory movements. 532. State the influence of the mind upon respiration.

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533. As the quantity of air inhaled at each unimpeded inspiration in lungs of ample size, is about forty cubic inches, it follows, if the movement of the ribs and diaphragm is restricted by an enfeebled action of the respiratory muscles, or by any other means, the blood will not be perfectly purified. In the experiment, (Sec. 522, 523,) suppose forty cubic inches of air must pass over the membrane twenty times every minute, and that this is the amount required to remove the vapor which arises from the membrane; if only half of this amount of air be supplied each minute, only one half as much water will be removed from the alcohol through the membrane in twenty-four hours; consequently, the alcohol would be impure from the water not being entirely removed.

534. Restrain the elevation of the ribs and depression of the diaphragm, so that the quantity of air conveyed into the lungs will be reduced to twenty cubic inches, when forty are needed, and the results will be as follows: Only one half of the carbonic acid will be eliminated from the system, and the blood will receive but one half as much oxygen as it requires. This fluid will then be imperfectly oxydated, and partially freed of its impurities. The impure blood will be returned to the left side of the heart, and the whole system will suffer from an infringement of organic laws.

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533. Illustrate the effect upon the blood when the respiratory muscles are enfeebled in their action. 534. Show how the blood is imperfectly purified by restricting the movements of the ribs and diaphragm.

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535. Scrofula, or consumption, frequently succeeds a depressed state of the nervous system. These diseases arise from the deposition of tuberculous matter in different parts of the body. Those individuals who have met with reverses of fortune, in which character and property were lost, afford painful examples. Hundreds yearly die from the effect of depressed spirits, caused by disappointed hopes, or disappointed ambition.

Illustration. A striking instance of the effects of mental depression is related by Laennec. In a female religious establishment in France, great austerities were practised; the mind was absorbed in contemplating the terrible truths of religion, and in mortifying the flesh. The whole establishment, in the space of ten years, was several times depopulated—with the exception of the persons employed at the gate, in the kitchen, and garden—with that fatal disease, consumption. This institution did not long continue, but was suppressed by order of the French government.

536. The purity of the blood is influenced by the condition of the lungs. When the bronchial tubes and air-cells have become partially impervious to air, from pressure upon the lungs, from fluids in the chest, from tumors, or from the consolidation of the cells and tubes from disease,—as inflammation, or the deposition of yellow, cheesy matter, called tubercles,—the blood will not be purified, even if the air is pure, the lungs voluminous, and the respiratory movements unrestricted, as the air cannot permeate the air-cells.

Observations. 1st. The twenty-three who escaped immediate death in the Black Hole of Calcutta were soon attacked with inflammation of the lungs, by which these organs were consolidated, and thus prevented the permeation of air into their cells. This disease of the lungs was caused by breathing vitiated air.

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535. Mention some of the effects of mental depression upon the body. What is related by Laennec? 536. Does the condition of the lungs influence the purity of the blood? Mention some of the conditions that will impede the oxydation of blood in the lungs. What occurred to those persons who escaped death in the Black Hole of Calcutta?

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2d. One of the precursory symptoms of consumption is the feeble murmur of respiration in the upper part of the lungs. This condition of these organs is produced by, or frequently follows, mental depression, the breathing of impure air, the stooping position in standing or sitting, and the restriction of the movements of the ribs and diaphragm.

3d. Persons asphyxiated by carbonic acid, water, strangling, or any noxious air, after resuscitation, are usually affected with coughs and other diseases of the lungs.

537. COLDS and COUGHS are generally induced by a chill, that produces a contraction of the blood-vessels of the skin; and the waste material, which should be carried from the body by the agency of the vessels of this membrane, is retained in the system, and a great portion of it is returned to the mucous membrane of the lungs. For such is the harmony established by the Creator, that if the function of any portion of the body is deranged, those organs whose offices are similar take on an increased action.

538. The waste material, that should have passed through the many outlets of the skin, creates an unusual fulness of the minute vessels that nourish the mucous membrane of the bronchia; this induces an irritation of these vessels, which increases the flow of blood to the nutrient arteries of the lungs. There is, also, a thickening of the lining membrane of the lungs, caused by the repletion of the bronchial vessels of the mucous membrane; this impedes the passage of air through the small bronchial tubes, and consequently the air-vesicles cannot impart a sufficient quantity of oxygen to purify the blood, and this fluid, imperfectly purified, does not pass with facility through the lungs. An additional obstacle to the free passage of air into the lungs, is the accumulation of blood in the pulmonary vessels.

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What is one of the precursory symptoms of consumption? How is this condition frequently produced? What diseases usually follow asphyxia by carbonic acid, water, strangling, &c.? 537. How are colds generally induced? 538. What effect has a common cold upon the mucous membrane of the lungs?

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539. As colds and coughs are very generally treated by the "matrons" of the community, or by the patient, the following suggestions may aid in directing a proper treatment: To effect a speedy cure, it is necessary to diminish the amount of fluid in the vessels of the lungs. This can be effected in two ways: 1st. By diminishing the quantity of blood in the system; 2d. By diverting it from the lungs to the skin. The first condition can be easily and safely affected, by abstaining from food, and drinking no more than a gill of fluid in twenty-four hours. As there is a continuous waste from the skin and other organs of the system, the quantity of blood by this procedure will be diminished, and the lungs relieved of the accumulated fluid.

540. The second condition can be accomplished by resorting to the warm or vapor bath. These and the common sweats will invite the blood from the lungs to the skin. By keeping up the action of the skin for a few hours, the lungs will be relieved. In some instances, emetics and cathartics are necessary; mucilages, as gum arabic or slippery-elm bark, would be good. After the system is relieved, the skin is more impressible to cold, and consequently requires careful protection by clothing. In good constitutions, the first method is preferable, and generally sufficient without any medicine or "sweating."

541. The method of resuscitating persons apparently drowned. In the first instance, it is necessary to press the chest, suddenly and forcibly, downward and backward, and instantly discontinue the pressure. Repeat this without intermission, until a pair of bellows can be procured. When the bellows are obtained, introduce the nozzle well upon the base of the tongue, and surround the mouth and nose with a towel or handkerchief, to close them. Let another person press upon the projecting part of the neck, called "Adam's apple," while air is introduced into the lungs through the bellows. Then press upon the chest, to force the air from the lungs, to imitate natural breathing. (Appendix M.)

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539. Give the first method for the treatment of cold. 540. The second method. 541, 542. How should persons apparently drowned be treated?

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542. Continue the use of the bellows, and forcing the air out of the chest, for an hour at least, unless signs of natural breathing come on. Wrap the body in warm, dry blankets, and place it near the fire, to preserve the natural warmth, as well as to impart artificial heat. Every thing, however, is secondary to filling the lungs with air. Avoid all friction until breathing is restored. Send immediately for medical aid.

543. The means of resuscitating persons asphyxiated from electricity, &c. In apparent death from electricity, (lightning,) the person is frequently asphyxiated from pa-ral'y-sis (palsy) of the respiratory muscles. To recover such persons, resort to artificial respiration. In cases of apparent death from hanging or strangling, the knot should be untied or cut immediately; then use artificial respiration, or breathing, as directed in apparent death from drowning.

Observation. It is an impression, in many sections of the country, that the law will not allow the removal of the cord from the neck of a body found suspended, unless the coroner be present. It is therefore proper to say, that no such delay is necessary, and that no time should be lost in attempting to resuscitate the strangled person.

544. The method of resuscitating persons apparently dead from inhaling carbonic acid gas. When life is apparently extinct from breathing carbonic acid gas, the person should be carried into the open air. The head and shoulders should be slightly elevated; the face and chest should be sponged or sprinkled with cold water, or cold vinegar and water, while the limbs are wrapped in dry, warm blankets. In this, as in asphyxia from other causes, immediately resort to artificial respiration.

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543. What treatment should be adopted in asphyxia from electricity? From hanging? 544. What should be the treatment in asphyxia from inhaling carbonic acid gas?

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Observations. 1st. Many persons have died from breathing carbonic acid that was formed by burning charcoal in an open pan or portable furnace, for the purpose of warming their, sleeping-rooms. This is not only produced by burning charcoal, but is evolved from the live coals of a wood fire; and being heavier than air, it settles on the floor of the room; and, if there is no open door or chimney-draught, it will accumulate, and, rising above the head of an individual, will cause asphyxia or death.

2d. In resuscitating persons apparently dead from causes already mentioned, if a pair of bellows cannot be procured immediately, let their lungs be inflated by air expelled from the lungs of some person present. To have the expired air as pure as possible, the person should quickly inflate his lungs, and instantly expel the air into those of the asphyxiated person. Place the patient in pure air, admit attendants only into the apartment, and send for a physician without delay.

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What sad results frequently follow the burning of charcoal in a closed room? What suggestion in resuscitating asphyxiated persons?

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CHAPTER XXVII.

ANIMAL HEAT.

545. The true sources of animal heat, or calorification, are still imperfectly known. No hypothesis has, as yet, received the concurrent assent of physiologists. We see certain phenomena, but the ultimate causes are hidden from our view. Its regular production, to a certain degree, is essential both to animal and vegetable life.

546. There is a tendency between bodies of different temperature to an equilibrium of heat. Thus, if we touch or approach a hot body, the heat, or caloric passes from that body to our organs of feeling, and gives the sensation of heat. On the contrary, when we touch a cold body, the heat passes from the hand to that body, and causes a sensation of cold.

547. The greater number of animals appear cold when we touch them; and, indeed, the temperature of their bodies is not much above that of the atmosphere, and changes with it. In man, and other animals that approach him in their organization, it is otherwise. They have the faculty of producing a sufficient quantity of caloric to maintain their temperatures nearly at the same degree, under all atmospheric changes, and keep themselves warm.

548. Those animals whose proper heat is not very perceivable, are called cold-blooded; as most species of fishes, toads, snakes, turtles, and reptiles generally. Those animals which produce sufficient heat independently of the atmosphere surrounding them, are called warm-blooded; as man, birds, quadrupeds, &c.

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545-570. What is said respecting animal heat? 545. Are the true sources of animal heat known? What do we see? 546. What is the tendency between bodies of different temperatures? Give an explanation. 547. What is said of the temperature of animals? 548. What is meant by cold-blooded animals? By warm-blooded animals?

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549. The temperature of man is about 98 deg., (Fahrenheit's thermometer,) and that of some other animals is higher; the temperature of birds, for example, is about 110 deg. It is obvious, that in most parts of the globe, the heat of the atmosphere is, even in summer, less than that of the human body. In our latitude, the mercury rarely attains 98 deg., and sometimes it descends to several degrees below zero.

550. Captain Parry, with his ship's company, in his voyage of discovery to the arctic regions, wintered in a climate where the mercury was at 40 deg., and sometimes at 55 deg. below zero. Captain Back found it 70 deg. below zero. These were 72 deg. and 102 deg. below the freezing point, or about 200 deg. below that of their own bodies, and still they were able to resist this low temperature, and escape being "frost-bitten."

551. Captain Lyon, who accompanied Captain Parry in his second voyage to the northern regions, found the temperature of an arctic fox to be 106 deg., while that of the atmosphere was 32 deg. below zero; making a difference between the temperature of the fox and that of the atmosphere, of 138 deg. Captain Scoresby found the temperature of a whale, in the Arctic Ocean, to be 104 deg., or nearly as high as that of other animals of the same kind in the region of the equator, while the temperature of the ice was as low as 32 deg., and the water was nearly as cold. These facts show what a strong counteracting energy there is in animals against the effects of cold.

552. On the other hand, it has been ascertained by numerous and well-conducted experiments, that the human body can be exposed, even for a length of time, to a very high temperature, without essentially elevating that of the body. Chantrey, the sculptor, often entered the furnace, heated for drying his moulds, when the temperature indicated by the thermometer was 330 deg. Chaubert, the Fire-King, is said to have entered ovens when heated to 600 deg. In 1774, Sir Charles Blagden entered a room in which the mercury rose to 260 deg. He remained eight minutes without suffering.

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549. What is the temperature of the human body? Of birds? How does the heat of the atmosphere in summer, in our latitude, compare with that of the human system? 550. What is related of Captain Parry? Of Captain Back? 551. Of Captain Lyon? Of Captain Scoresby? What do these facts show? 552. What has been ascertained on the other hand?

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553. In order to render it certain that there was no fallacy, says Sir Charles Blagden, "in the degree of heat shown by the thermometer, but that the air breathed was capable of producing all the well-known effects of such a heat on inanimate matter, I put some eggs and beefsteak upon a tin frame placed near the thermometer, and farther distant from the cockle than from the wall of the room. In about twenty minutes the eggs were taken out, roasted quite hard; and in forty-seven minutes, the steak was not only dressed, but almost dry."

554. If a thermometer be placed under the tongue of a healthy person, in all climates and seasons the temperature will be found nearly the same. Sir Charles Blagden, "while in the heated room, breathed on a thermometer, and the mercury sank several degrees; and when he expired forcibly, the air felt cool as it passed through the nostrils, though it was scorching hot when it entered them in inspiration."

Observation. Did not the human body possess within itself the power of generating and removing heat, so as to maintain nearly an equality of temperature, the most fatal consequences would ensue. In northern latitudes, especially, in severe weather of winter, the blood would be converted into a solid mass, and on the other hand, the fatty secretion, when subjected to equatorial heat, would become fluid, and life would be extinguished.

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What is related of Chantrey? Of Chaubert? Of Sir Charles Blagden? 553. Give Sir Charles's own statement. 554. What is said of the temperature of the human tongue? Mention the experiment by Sir Charles Blagden. What would be the effect if the human system did not maintain an equality of temperature?

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555. To enable man, and other warm-blooded animals, to maintain this equilibrium of temperature under such extremes of heat and cold, naturally suggests two inquiries: 1st. By what organs is animal heat generated? 2d. By what means is its uniformity maintained?

556. The ancients had no well-arranged theory on the subject of animal heat. They believed that the chief object of respiration was to cool the blood, and that the heart was the great furnace where all the heat was generated. At a later period, Mayow, from his discoveries respecting respiration, asserted that the object of respiration was to produce heat, and denied that the blood was cooled in the lungs.

557. When it was discovered that, both in combustion and respiration, carbonic acid was produced and oxygen absorbed, it led Dr. Black to conclude that breathing was a kind of combustion by which all the heat of the body was produced. This theory was objected to, because, if all the heat was generated in the lungs, like those parts of a stove in contact with the fuel, they would be at a higher temperature than those parts at a distance, which was known not to exist.

558. The next theory, and one which received the sanction of the scientific men of Europe, was proposed by Dr. Crawford. He agreed with Dr. Black that heat not only was generated in the lungs, but that the arterial blood had a greater capacity for heat than the venous, and that this increase of capacity takes place in the lungs. At the moment heat is generated, a portion of it, under the name of latent heat, is absorbed and conveyed to the different parts of the body Wherever arterial blood is converted into venous, this latent heat is given out. But, unfortunately for this theory, Dr. Davy proved the capacity of both, for heat, to be nearly the same.

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555. What inquiries are naturally suggested? 556. What was the theory of the ancients? What did Mayow assert at a later period? 557. What was the theory of Dr. Black? The objection? 558. What was the theory of Dr Crawford?

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559. No one can doubt that respiration and animal heat are closely connected. Those animals whose respiratory apparatus is the most extended, have the highest temperature. An example is seen in birds, whose organs of respiration extend over a large part of the body, and their temperature is 12 deg. above man; while the respiratory apparatus of cold-blooded animals, as some kinds of fish, is imperfect, and only a small quantity of blood is subjected, at any time, to the effects of respiration.

560. To understand the process by which heat is generated in the human system and in animals, it will be necessary to state: 1st. That the apparent heat of a body, as perceived by the touch, or as indicated by a thermometer, is not the measurement of heat contained in the body, or its capacity for heat.

Illustration. If we mix one pound of water, at the temperature of 60 deg., with another pound at 91 deg., the resulting temperature will be exactly the medium, or 75 1/2 deg. But, if we mix a pound of water at 60 deg. with a pound of quicksilver at 91 deg., the resulting temperature will be only 61 deg., because the capacity of water for heat is so much greater than that of quicksilver, that the heat which raised the quicksilver 31 deg. will raise the water only 1 deg.

561. 2d. When the density and the arrangement of the atoms of a body are changed, its capacity to hold heat in a latent state is altered. If it will retain more, heat will be absorbed from contiguous and surrounding substances; but, if its capacity for caloric is lessened, heat will be set free and given out to surrounding bodies.

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The objection? 559. In what do all the physiologists of the present day concur? How is it proved that respiration and animal heat are closely connected? 560. What is said of the apparent heat of bodies? How is this illustrated? 561. What is the effect when the density and the arrangement of the atoms of a body are changed?

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Illustrations. 1st. Ice and salt, (Chl. of Sodium,) when mixed, are converted into a fluid. In this state they will hold more heat than when solid. The heat necessary to produce this change is drawn from the surrounding medium, which is made proportionally colder by the loss of caloric imparted to the ice and salt. It is by this chemical process that "ice-cream" is made.

2d. On the other hand, mix water and sulphuric acid, (oil of vitriol,) of the temperature of 60 deg., and the mixture will become quite warm, and will freely impart its heat to surrounding and contiguous objects.

562. The same principle is exhibited, when oxygen unites with an inflammable body, as in the burning of wood, coal, oil, &c. In combustion, the oxygen of the atmosphere unites with carbon and hydrogen, and carbonic acid and water are produced. This process, according to all the known laws of caloric, is attended with heat. The quantity of heat disengaged in combustion is always in proportion to the amount of carbon and hydrogen consumed; thus a piece of wood weighing one pound, in burning slowly, would give out the same quantity of heat as a pound of shavings of the same wood, in burning rapidly. Upon these principles, the production of animal heat may be understood.

563. The food contains carbon and hydrogen. These exist in the chyle. The old and waste atoms of the body likewise contain the same elements. In the lungs the oxygen and nitrogen of the inspired air are separated. It is now supposed that the oxygen enters the capillary vessels of the lungs, and mingles with the blood, with which it is carried to the heart and thence to the nutrient capillary vessels of every part of the system.

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Give the 1st illustration. The 2d. 562. What changes take place when oxygen unites with an inflammable body? To what is the quantity of heat proportionate in combustion? Give an example. 563. How are carbon and hydrogen supplied to the system? How the oxygen? Where does the oxygen mingle with the blood?

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564. In the capillary vessels, the oxygen of the arterial blood unites with the carbon and hydrogen which the refuse materials contain, and carbonic acid and water are formed. The combustion of carbon and hydrogen in the capillaries of every part of the system, (the lungs not excepted,) is attended with a disengagement of heat, and the carbonic acid and water are returned to the lungs in the dark-colored blood, and evolved from the system.

565. Sir Benjamin Brodie and some others have maintained, that the heat of the system is generated exclusively by the influence of the brain and nerves. This theory is discarded by most physiologists; yet it is true that the nervous system exercises a great influence over the action of the capillary vessels in the process of nutrition, secretion, and absorption. When these operations are most active, the change among the particles of matter of which the body is composed, is then greatest, and the generation of heat is increased in a corresponding degree.

566. The necessity of pure, red blood in the production of animal heat, is shown when the vessels that carry blood to a limb are ligated, or tied; the part immediately becomes colder. The necessity of nervous influence is seen in the diminished temperature of a paralytic limb.

567. Our next inquiry is, By what means is the uniformity of temperature in the body maintained? As there is a constant generation of heat in the system, there would be an undue accumulation,—so much so as to cause disagreeable sensations,—if there were no means by which it could be evolved from the body, or its production lessened.

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564. Where does it unite with the carbon and hydrogen contained in the body, and how is heat generated? 565. What was the theory of Sir Benjamin Brodie? Is this theory in general discarded? What is true of this theory? 566. How is the necessity of pure, red blood and nervous action shown in the production of animal heat?

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568. It has been ascertained that the principal means by which the system is kept at a uniform temperature, is the immense evaporation from the skin and lungs. These membranes, in an ordinary state, are constantly giving out water, which is converted into vapor, and carried off by the surrounding air. The quantity of heat abstracted from the system to effect this, depends on the rapidity of the change of air, its temperature, and the amount of water it contains in a state of vapor. The quantity removed is greatest when the air is warm and dry, and the change, or current, rapid.

Observations. 1st. The first discovery of the use of free evaporation of the perspiration from the skin in reducing the heat of the body, and the analogy subsisting between this process and that of the evaporation of water from a rough porous surface, so constantly resorted to in warm countries, as an efficacious means of reducing the temperature of the air in rooms, and of wine and other drinks, much below that of the surrounding atmosphere, was made by Franklin.

2d. In all ages and climes, it has been observed that the increased temperature of the skin and system in fevers, is abated as soon as free perspiration is restored. In damp, close weather, as during the sultry days of August, although the temperature is lower, we feel a disagreeable sensation of heat, because the saturation of the air with moisture lessens evaporation, and thus prevents the escape of heat through the lungs and skin.

3d. It is on the principle of the evaporation of fluids that warm vinegar and water, applied to the burning, aching head, cools it, and imparts to it a comfortable feeling. The same results follow if warm liquids are applied to the skin in the hot stage of fever; and this evaporation can be increased by constant fanning.

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568. What are the principal means by which a uniform temperature of the body is maintained? On what does the quantity of heat abstracted from the system depend? What discovery relative to animal heat is due to Franklin? What is said of free perspiration in fevers? What occasions the disagreeable sensation of heat in damp, close weather?

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4th. It is frequently noticed, in very warm weather, that dogs and other domestic animals are seen with their tongues out of their mouths, and covered with frothy secretions. This is merely another mode of reducing animal heat, as the skin of such animals does not perspire as much as that of man.

569. Under some circumstances, a portion of the heat of the system is removed by radiation. When cold air comes in contact with the skin and mucous membrane of the lungs, heat is removed from the body, as from a stove, to restore an equilibrium of temperature. The removal of heat from the body is greatest when we are in a current of cold air, or when a brisk, cold wind is blowing upon us.

570. As the primary object of the different processes of nutrition is to supply animal heat, so the action of the different nutritive organs is modified by the demands of the system for heat. When heat is rapidly removed from the body, the functional activity of the organs of nutrition is increased. When the system is warmed by foreign influence, the activity of the nutritive organs is diminished. This leads to the natural, and, we may add, instinctive change in the quality and quantity of food at different seasons of the year.

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569. When is heat radiated from the body? When is it greatest? 570. What is the primary object of the different processes of nutrition? When is the activity of the nutritive organs increased? When diminished? To what does this lead?

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CHAPTER XXVIII.

HYGIENE OF ANIMAL HEAT.

571. The amount of heat generated in man and inferior animals depends upon the quantity and quality of the food, age, exercise, the amount and character of the respired air, condition of the brain, skin, and general system.

572. Animal heat is modified by the proportion of digestible carbon which the food contains, and by the quantity consumed. As the kind of fuel that contains the greatest amount of combustible material evolves the most caloric when burned, so those articles of food that contain the greatest quantity of carbon produce the most heat when converted into blood. The inhabitants of the frigid zones, and individuals in temperate climates during the cold season, consume with impunity stimulating animal food, that contains a large proportion of carbon, while the inhabitants of the tropical regions, and persons in temperate climates during the warm season, are more healthy with a less stimulating or vegetable diet.

Observation. When we ride or labor in cold weather, an adequate amount of nutritious food will sustain the warmth of the system better than intoxicating drinks.

573. Age is another influence that modifies the generation of animal heat. The vital forces of the child being feeble, less heat is generated in its system than in that of an adult. The experiments of Dr. Milne Edwards show that the power of producing heat in warm-blooded animals, is at its minimum at birth, and increases successively to adult age; and that young children part with their heat more readily than adults, and, instead of being warmer, are generally a degree or two colder. After adult age, as the vital powers decline, the generation of heat is diminished, as the energies of the system are lessened. Hence the young child, and the debilitated aged person, need more clothing than the vigorous individual of middle age.

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571-585. Give the hygiene of animal heat. 571. State some of the influences that modify the generation of animal heat. 572. What element of the food influences the generation of heat? When and where can animal food be eaten with impunity? Give the practical observation.

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574. Exercise is an influence that modifies the generation of animal heat. As carbon and hydrogen enter into the composition of the organs of the body, whatever increases the flow of blood in the system, increases also the deposition of new material, and the removal of the waste particles. This change among the particles of matter is attended with an elevation of temperature, from the union of oxygen with the carbon and hydrogen of the waste atoms. For this reason, a person in action is warmer than in a quiescent state. Consequently, the amount of clothing should be increased, when exercise or labor is diminished or suspended.

575. On the other hand, whatever impedes the circulation and the interchange of the atoms of matter, diminishes animal heat. Common observation shows, that the extremities are not as warm when tight gloves or boots are worn as when they are loose. One reason is, the circulation of blood is impeded, which is attended with less frequent change of the particles of matter.

576. The quantity of air which is inhaled modifies the heat of the system. In the generation of heat in a stove, air, or oxygen, is as essential as the wood or coal. It is equally so in the production of animal heat. The oxygen of the inspired air should be in proportion to the carbon and hydrogen to be consumed. This requires voluminous lungs, together with free movements of the ribs and diaphragm. A person whose chest is small, and whose apparel is worn tight over the ribs, suffers more from the cold, and complains more frequently of chilliness and cold extremities, than the broad-chested and loosely dressed.

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What do the experiments of Dr. Milne Edwards show? 574. Why does exercise influence animal heat? 575. What is the effect when the circulation of blood is impeded? Give examples. 576. Why do those persons that have broad chests and voluminous lungs suffer less from cold than the narrow-chested with small lungs?

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Observation. Fishes that breathe by means of gills, as the cod, pike, &c., depend solely on the small quantity of oxygen that is contained in the air mixed with the water. Their temperature is not much greater than the medium in which they live. Whales, dolphins, &c., breathe by means of lungs, and the inhalation of atmospheric air makes their temperature about 100 deg., independent of the heat of the element in which they live.

577. The quality of respired air influences the generation of animal heat. In vestries, and other public rooms, when crowded with an audience, where the ventilation is inadequate, the lamps will emit but a faint light, because the oxygen is soon expended, and there is not enough of the vivifying principle to unite with the oil and disengage light. In the human body, when the respired air has lost some of its life-giving properties, the combustion that takes place in different parts of the system is not so complete as when it contains a proper proportion of oxygen; and hence less heat is disengaged. For this reason, those persons that breathe impure air, either in the daytime or night, require more clothing, than those that work and sleep in well-ventilated rooms.

578. The condition of the brain and nervous system affects the generation of animal heat. If the brain is diseased, or the mind is absorbed in thought, depressed by sorrow, or aroused from fear, the breathing becomes slow and scarcely perceptible, and a chilliness pervades the body, particularly the extremities; while, on the contrary, if the mind and nervous system are excited by joyous and agreeable emotions, the circulation of blood is quicker, and the system more powerfully resists external cold. During sleep, when the brain is partially inactive, less heat is generated than when awake.

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What is said of those fishes that breathe by means of gills? Of those that breathe by means of lungs? 577. Why do lamps give but a faint light in crowded, unventilated rooms? What effect on animal heat has impure air? 578. Mention the effects of some of the mental emotions on animal heat.

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Observation. The preceding remark explains why an individual who sleeps in the same clothing that was adequate to prevent chills while awake, contracts a cold, unless he throws over him an additional covering.

579. The state of the skin exercises much influence in the generation of heat. If the functions of this membrane are not interrupted, more heat will be generated than when it is pallid and inactive. The action of the capillaries is most energetic when the skin is clean; on this account, before taking a walk or a ride, in cold weather, remove all impurities from the skin, by thorough ablution and vigorous friction.

580. The amount and kind of clothing modify the temperature of the system. Those persons that are well clothed have greater power to resist cold than the thinly apparelled, because both the evaporation and the radiation from the skin are impeded, and less heat, in consequence, is abstracted from the body. If the articles of apparel possess the property of retaining air in their meshes, as flannel, the removal of heat is not as rapid as when linen is worn.

Observation. In winter, although more heat is generated in the system than in summer, yet we require more clothing, and also those articles that are poor conductors of heat, because caloric is more rapidly extracted in clear, cold weather, than in a warm day.

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What does the preceding remark explain? 579. What suggestion respecting the condition of the skin before taking a walk or ride in a cold day? Why? 580. Do the amount and kind of clothing affect animal heat? What is said of well-clothed persons? When does the system generate the most heat?

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581. The health and constitution influence the generation of heat. When the health is firm, and the constitution vigorous, less clothing is needed, for the change among the particles of matter is more rapid, and more heat is generated, than when the opposite condition obtains. Persons of a feeble constitution, particularly, if any of the vital organs[18] are diseased, need more clothing and require rooms of a warmer temperature, than individuals who are free from disease and have a vigorous constitution.

[18] The brain, lungs, heart, and digestive organs, are called vital organs.

Observation. Persons who are infirm, and whose vital powers are feeble, in general, accustom themselves to an undue amount of clothing and warm rooms. A more judicious practice would be, to exercise more and use a moderate amount of clothing, together with a more nutritious diet.

582. The surplus heat should be removed equally from all parts of the system. The rapid evaporation of fluids, as in free perspiration, or from radiation, as in a cold atmosphere, is attended with a removal of heat from the system. This modifies the action of the circulatory vessels. Consequently, if heat is suddenly and rapidly abstracted from one part of the system, the equilibrium of the circulation is destroyed, which will produce disease.

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Why do we, then, require more clothing in winter than in summer? 581. Why do persons of firm health and vigorous constitutions need less clothing than those who are feeble? What is a general practice among infirm persons? What would be more judicious? 582. Why should the surplus heat be removed equally from all parts of the system? What is said respecting currents of air from small apertures?

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Observation. Currents of air that impinge upon small portions of the body, as from small apertures, or from a window slightly raised, should be avoided. They are more dangerous than to expose the whole person to a brisk wind, because the current of air removes the heat from the part exposed, which disturbs the circulation of blood and causes disease, usually in the form of "colds." For the same reason, it is not judicious to stand in an open door, or the opening of a street.

583. The system suffers less when the change of temperature is gradual. The change in the production of heat, as well as in the evaporation of fluids from the system, is gradual when not influenced by foreign causes. This gradual change is known under the name acclimation. By this means the body is enabled to endure tropical heat and polar cold. Owing to this gradual adaptation of the system to different temperatures, we can bear a greater degree of heat in the summer between the tropics, than in the winter under the polar circles. On the other hand, we can endure a greater degree of cold in winter and in the arctic region, than in the summer and in equatorial countries.

584. The sensation of heat which would be oppressive in a mild, warm day of January, would only be grateful in July, and a degree of cold which could scarcely be endured in August, would not be uncomfortable in December. The changes of season in our latitude prevent the disagreeable and perhaps fatal consequence that would follow, if no spring or autumn intervened between the severity of winter's cold and the intensity of summer's heat. During the transition periods, the constitution is gradually changed, and adapted to bear the extremes of temperature without suffering. The amount of heat generated in the nutrient capillary vessels, is likewise diminished or increased as the temperature of the season becomes greater or less.

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583. In what manner should change of temperature take place, to be adapted to the body? How is the body enabled to endure tropical heat and polar cold? State some of the effects of the gradual adaptation of the system to different temperatures. 584. What is said relative to a warm day in winter? To a cold day in summer? What is said of the changes of seasons in our latitude? What effect on the constitution during spring and autumn? What change in the amount of heat generated?

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585. But, on the contrary, we cannot suddenly pass from one extreme of temperature to the other with impunity. Let an inhabitant of Quebec suddenly arrive in Cuba in February, and he would suffer from languor and exhaustion; after becoming acclimated to this tropical climate, let him suddenly return to Quebec in January, and the severity of the weather would be almost insupportable.

Observations. 1st. Experience shows that heated rooms, as well as tropical climates, lessen the generation of heat in the body, and likewise the power of resisting cold. It would be idle for the merchant from his warehouse, or the mechanic from his heated shop, to attempt to sit on the box with a coachman, with the same amount of clothing as his companion, who is daily exposed to the inclemency of the weather.

2d. "It is the power of endurance of cold at one period, and the absence of its necessity at another, that enables animals, in their wild and unprotected state, to bear the vicissitudes of the seasons with so little preparation in clothing, and so little real inconvenience."

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585. What effect on the system has a sudden transition from a cold to a warm climate? What does experience show? Why do wild animals bear the vicissitudes of the seasons with so little preparation in clothing?

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CHAPTER XXIX.

THE VOICE.

586. The beautiful mechanism of the vocal instrument, which produces every variety of sound, from a harsh, unmelodious tone, to a soft, sweet, flute-like sound, has, as yet, been imperfectly imitated by art. It has been compared, by many physiologists, to a wind, reed, and stringed instrument. This inimitable, yet simple instrument, is the Lar'ynx.

587. Incidentally, the different parts of the respiratory organs, as well as the larynx, are subservient to speaking and singing. The tongue, nasal passages, muscles of the fauces and face, are agents which aid in the intonation of the voice.

ANATOMY OF THE VOCAL ORGANS.

588. The LARYNX is a kind of cartilaginous tube, which, taken as a whole, has the general form of a hollow, reversed cone, with its base upward toward the tongue, in the shape of an expanded triangle. It opens into the pharynx, at its superior extremity, and communicates, by its inferior opening with the trachea. It is formed by the union of five cartilages, namely, the Thy'roid, the Cri'coid, the two A-ryt-e'noid, and the Ep-i-glot'tis. These are bound together by ligaments, and moved by muscles.

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586. What is said of the structure of the vocal instrument? With what instrument have physiologists compared it? What is the vocal instrument called? 587. What organs are called into action in speaking beside the larynx? 588-596. Give the anatomy of the vocal organs. 588. Describe the larynx. Name the cartilages that form the larynx.

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589. The THYROID CARTILAGE is the largest of the five, and forms the prominence in the front of the neck, called Po'mum A-da'mi, (Adam's apple.) It is composed of two parts, and is connected with the bone of the tongue above, and with the cricoid cartilage below.

590. The CRICOID CARTILAGE takes its name from its resemblance to a ring. It is situated below the thyroid cartilage, it is narrow in front, broader at the sides, and still broader behind, where it is connected with the thyroid cartilage. Below, it connects with the first ring of the trachea.



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589. Describe the thyroid cartilage. 590. From what does the cricoid cartilage derive its name? Where is it situated? Explain fig. 102. Fig. 103.

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591. The ARYTENOID CARTILAGES are small triangular bodies placed upon the back part of the cricoid cartilage. They are connected with the thyroid cartilages, by four ligaments, called Vo'cal Cords.

592. The EPIGLOTTIS is fibro-cartilaginous, and is placed behind the base of the tongue. In shape it resembles a leaf of parsley.

593. The VOCAL CORDS, or ligaments, are formed of elastic and parallel fibres, enclosed in a fold of mucous membrane. They are about two lines in width, and pass from the anterior angle of the thyroid cartilage, to the two arytenoid cartilages. The one is called the superior, and the other the inferior vocal ligament. The cavity, or depression between the superior and inferior ligament, is called the ventricle of the larynx. The aperture, or opening between these ligaments, is called the glot'tis, or chink of the glottis. It is about three fourths of an inch in length, and one fourth of an inch in width, the opening being widest at the posterior part. This opening is enlarged and contracted by the agency of the muscles appropriated to the larynx.



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591. Describe the arytenoid cartilages. 592. What is said of the epiglottis? 593. Give the structure of the vocal cords. Where is the ventricle of the larynx? Where is the glottis situated? What is represented by fig. 104? Explain fig. 105.

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594. The larynx is connected by muscles with the sternum, oesophagus, base of the skull, hyoid bone, lower jaw, and tongue. This organ is supplied with a large number of blood-vessels, and it likewise receives nerves from the sympathetic system, and two large nerves from the tenth pair. The number and size of the nervous filaments distributed to the mucous membrane of the larynx, render it more sensitive than any other portion of the respiratory organs.

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How is the glottis enlarged or contracted? Explain fig. 106. 594. By what means and to what organs is the larynx connected? Why is the larynx more sensitive than other parts of the respiratory organs?

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595. The larynx is much more developed and prominent in man than in woman. In the former, the anterior angle of the thyroid cartilage is acute, while in the latter it is rounded, and the central slope of the superior border of the same cartilage is less deep, and the epiglottis smaller and less prominent, than in man.

596. The difference in the formation of the larynx in infancy is less striking; but at a later period, it is more developed in the male than in the female. It is very remarkable that this increase is not progressive, like that of other organs, but, on the contrary, develops itself at once at the period of puberty.

PHYSIOLOGY OF THE VOCAL ORGANS.

597. In the formation of the voice, each part already described performs an important office. The cricoid and thyroid cartilages give form and stability to the larynx; the arytenoid cartilages, by their movement, vary the width of the glottis. The epiglottis is flexible and elastic. When it is erect, the chink of the glottis is open, as in inspiration; when depressed, as in swallowing food and drink, it covers and closes this aperture. It prevents the introduction of articles of food into the trachea, and probably modifies sound as it issues from the glottis.

598. The muscles of the neck elevate and depress the larynx; the muscles of the larynx increase or diminish the width of the glottis; at the same time, the vocal cords are relaxed or tightened, while the muscles of the face open and close the mouth.

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595. What difference between the formation of the larynx of the female and that of the male? 596. Does this difference exist in childhood? Is its development progressive? 597-600. Give the physiology of the vocal organs. 597. Which cartilages give stability and form to the larynx? Which vary the width of the glottis? What is the function of the epiglottis? 598. What effect have the muscles of the neck upon the larynx? The use of the muscles of the larynx?

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599. The elasticity of the ribs and the contraction of the abdominal muscles diminish the cavity of the chest, and the air, in consequence, is pressed from the air-cells into the bronchial tubes and trachea. It then rushes by the vocal cords, and causes a peculiar vibration, which produces sound.

Observations. 1st. Experiments have satisfactorily shown that the vocal cords are the principal agents in the formation of the voice. The tongue, which many have supposed to be the most important organ in speaking, is not essential to sound. In several instances it has been removed, and the persons thus mutilated could speak with fluency.

2d. When the vocal cords are ulcerated, or inflamed, however slightly, as in sore throat produced by a cold, the voice will be changed. The loss of speech among public speakers is generally produced by a relaxation of the vocal ligaments. Hence, bronchitis is a misnomer for this affection.

600. Sound is varied by the velocity of the expelled current of air, and the tension of the vocal ligaments. The size of the larynx, the volume and health of the lungs, the condition of the fauces and nasal passages, the elevation and depression of the chin, the development and freedom of action of the muscles which are attached to the larynx, the opening of the mouth, the state of the mind, and general health of the system, influence the modulations of sound.

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What effect has the combined action of these muscles? 599. How is sound produced? What have experiments shown? What effect has disease of the vocal ligaments upon the voice? 600. How is sound varied? Mention other conditions that contribute to the modulation of sound.

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CHAPTER XXX.

HYGIENE OF THE VOCAL ORGANS.

601. The voice can be changed and modified by habit. Sailors, smiths, and others, who are engaged in noisy occupations, exert their vocal organs more strongly than those of more quiet pursuits. This not only affects the structure of the vocal organs, but varies the intonation of the voice.

602. The voice is strong in proportion to the development of the larynx, and the capacity of the chest. Singing and reading aloud improve and strengthen the vocal organs, and give a healthy expansion to the chest. The enunciation of the elementary sounds of the English language, aids in developing the vocal organs, as well as preventing disease of the throat and lungs. This exercise also conduces to the acquisition of musical sounds.

603. The attitude affects the modulation of the voice. When an individual stands erect, the movements of the whole respiratory apparatus are most free and effective. The larynx is brought forward by the erect position of the head and the elevation of the chin. The muscles of the arytenoid cartilages are then brought to a proper relation for action, by which a tension of the vocal cords is produced, that favors clear and harmonious enunciation.

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