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 circ.u.mstances. 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 quant.i.ty 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 quant.i.ty 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.

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?

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.

_Ill.u.s.tration._ 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 ill.u.s.trated 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 quant.i.ty 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.

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 ill.u.s.trated?

500. The principle in this experiment is a.n.a.logous 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 gla.s.s jar that has a stop-c.o.c.k, or one with a gla.s.s 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-c.o.c.k. 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 subst.i.tute for a jar with a stop-c.o.c.k, 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 quant.i.ty, 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.

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.

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 circ.u.mstances, the question may be asked, To what degree may the air be vitiated and still sustain life? and what is the smallest quant.i.ty 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 circ.u.mstance, that the expired air mixes with and vitiates the surrounding element that has not been inhaled.

503. _The quant.i.ty 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 quant.i.ty 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.

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.

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 circ.u.mstances, 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.

_Ill.u.s.trations._ 1st. The effects of breathing the same air again and again, are well ill.u.s.trated by an incident that occurred in one of our halls of learning. A large audience had a.s.sembled 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.

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 ill.u.s.tration of the effects of impure air on lighted lamps.

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 quant.i.ty 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.

_Ill.u.s.tration._ 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.

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 ill.u.s.tration.

507. _Churches, concert halls, and all rooms designed for a collection of individuals, should be amply ventilated._ While the architect and workmen are a.s.siduous 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.

_Ill.u.s.tration._ 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 ca.n.a.l-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 quant.i.ty 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 a.s.sembly, 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 ma.s.s 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."

What suggestion when a school-room is not ventilated? 507. What is said in regard to ventilating churches, concert halls, &c.? State the ill.u.s.tration. 508. What remarks relative to public conveyances? 509.

State the influence of habit by Birnan.