CHAPTER IV. THE LAWS OF HEALTH. PHILOSOPHY OF RESPIRATION. 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, they are in the highest degree deleterious and loathsome.-- Birnan.

Respiration is usually defined as the process by which air is taken into the lungs and expelled from them. It explains the changes that take place in these organs, in the conversion of chyle and venous, or worn-out blood, into arterial or nutrient blood. In order to be clearly understood, I must premise a few observations on the circulation of the blood.[11] The blood circulating through the body is of two different kinds; the one red or arterial, and the other dark or venous blood. The former alone is capable of affording nourishment and supporting life. It is distributed from the left side of the heart all over the body by means of a great artery, which subdivides in its course, and ultimately terminates in myriads of very minute ramifications closely interwoven with, and in reality constituting a part of, the texture of every living part. On reaching this extreme point of its course, the blood passes into equally minute ramifications of the veins, which in their turn gradually coalesce, and form larger and larger trunks, till they at last terminate in two large veins, by which the whole current of the venous blood is brought back in a direction contrary to that of the blood in the arteries, and poured into the right side of the heart. On examining the quality of the blood in the arteries and veins, it is found to have undergone a great change in its passage from the one to the other. The florid hue which distinguished it in the arteries has disappeared, and given place to the dark color characteristic of venous blood. Its properties, too, have changed, and it is now no longer capable of sustaining life.

Two conditions are essential to the reconversion of venous into arterial blood, and to the restoration of its vital properties. The first is an adequate provision of new materials from the food to supply the place of those which have been expended in nutrition, and the second is the free exposure of the venous blood to the atmospheric air. The first condition is fulfilled by the chyle, or nutrient portion of the food, being regularly poured into the venous blood just before it reaches the right side of the heart, and the second by the important process of respiration, which takes place in the air-cells of the lungs. The venous blood, having arrived at the right side of the heart, is propelled by the contraction of that organ into a large artery, leading directly, by separate branches, to the two lungs, and hence called the pulmonary artery. In the innumerable branches of this artery expanding themselves throughout the substance of the lungs, the dark blood is subjected to the contact of the air inhaled in breathing, and a change in the composition both of the blood and of the inhaled air takes place, in consequence of which the former is found to have reassumed its florid or arterial hue, and to have regained its power of supporting life. The blood then enters minute venous ramifications, which gradually coalesce into larger branches, and at last terminate in four large trunks in the left side of the heart, whence the blood, in its arterial form, is again distributed over the body, to pursue the same course and undergo the same change as before.

It will be perceived that there are two distinct circulations, each of which is carried on by its own system of vessels. The one is from the left side of the heart to every part of the body, and back to the right side of the heart. The other is from the right side of the heart to the lungs, and back to the left side of the heart. The former has for its object nutrition and the maintenance of life; and the latter, the restoration of the deteriorated blood, and the animalization or assimilation of the chyle from which the blood is formed. This process has already been referred to as the completion of digestion; for chyle is not fitted to nourish the system until, by its exposure to the atmospheric air in the lungs, it is converted into arterial blood.

As the food can not become a part of the living animal, or the venous blood regain its lost properties until they have undergone the requisite changes in the air-cells of the lungs, the function of respiration by which these are effected is one of pre-eminent importance in the animal economy, and well deserves the most careful examination. The term respiration is frequently restricted to the mere inhalation and expiration of air from the lungs, but more generally it is employed to designate the whole series of phenomena which occur in these organs. The term sanguification is occasionally used to denote that part of the process in which the blood, by exposure to the action of the air, passes from the venous to the arterial state. As the chyle does not become assimilated to the blood until it has passed through the lungs, this term, which signifies blood-making, is not unaptly used.

The quantity and quality of the blood have a most direct and material influence upon the condition of every part of the body. If the quantity sent to the arm, for example, be diminished by tying the artery through which it is conveyed, the arm, being then imperfectly nourished, wastes away, and does not regain its plumpness till the full supply of blood be restored. In like manner, when the quality of that fluid is impaired by deficiency of food, bad digestion, impure air, or imperfect sanguification in the lungs, the body and all its functions become more or less disordered. Thus, in consumption, death takes place chiefly in consequence of respiration not being sufficiently perfect to admit of the formation of proper blood in the lungs. A knowledge of the structure and functions of the lungs, and of the conditions favorable to their healthy action, is therefore very important, for on their welfare depends that of every organ of the body.

The exposure of the blood to the action of the air seems to be indispensable to every variety of animated creatures. In man and the more perfect of the lower animals, it is carried on in the lungs, the structure of which is admirably adapted for the purpose. In many animals, however, the requisite action is effected without the intervention of lungs. In fishes, for example, that live in water and do not breathe, the blood circulates through the gills, and in them is exposed to the air which the water contains. So necessary is the atmospheric air to the vitality of the blood in all animals, that the want of it inevitably proves fatal. A fish can no more live in water deprived of air, than a man could in an atmosphere devoid of oxygen, which is the element that unites with the blood in the lungs in sanguification.

In man the lungs are those large, light, spongy bodies which, along with the heart, completely fill up the cavity of the chest. They vary much in size in different persons; and as the chest is formed for their protection, it is either large and capacious, or the reverse, according to the size of the lungs.

The substance of the lungs consists of bronchial tubes, air-cells, blood-vessels, nerves, and cellular membrane. The bronchial tubes are merely continuations and subdivisions of the windpipe, and serve to convey the external air to the air-cells of the lungs. The air-cells constitute the chief part of the lungs, and are the termination of the smaller branches of the bronchial tubes. When fully distended, they are so numerous as in appearance to constitute almost the whole lung. They are of various sizes, from the twentieth to the hundredth of an inch in diameter, and are lined with an exceedingly fine, thin membrane, on which the minute capillary branches of the pulmonary arteries and veins are copiously ramified. It is while circulating in the small vessels of this membrane, and there exposed to the air, that the blood undergoes the change from the venous to the arterial state. So numerous are these air-cells, that the aggregate extent of their lining membrane in man has been computed to exceed twenty thousand square inches, or about ten times the surface of the human body. Some writers place the estimate considerably higher.

A copious exhalation of moisture takes place in breathing, which presents a striking analogy to the exhalation from the surface of the skin already described. In the former as in the latter instance, the exhalation is carried on by the innumerable minute capillary vessels in which the small arterial branches terminate in the air-cells. Pulmonary exhalation is, in fact, one of the chief outlets of waste matter from the system; and the air we breathe is thus vitiated, not only by the subtraction of its oxygen and the addition of carbonic acid gas, but also by animal effluvia, with which it is loaded when returned from the lungs. In some individuals this last source of impurity is so great as to render their vicinity offensive, and even insupportable. It is this which gives the disagreeable, sickening smell to crowded rooms. The air which is expired from the lungs is rendered offensive by various other causes. When spirituous liquors are taken into the stomach, for example, they are absorbed by the veins and mixed with the venous blood, in which they are carried to the lungs to be expelled from the body. In some instances, when persons have drank copiously of spirits, their breath has been so saturated with them as actually to take fire and burn. An instance of this kind has recently been communicated to me by several reliable witnesses, in which the flame was extinguished by closing the mouth and nose, thus excluding the pure air that supported the combustion, until the unfortunate experimenter could remove the candle by which his breath had taken fire. This illustration will explain how the odor of different substances is frequently perceptible in the breath long after the mouth is free from them.

The lungs not only exhale waste matter, but absorption takes place from their lining membrane. In both of these respects there is a striking analogy between the functions performed by the lungs and the skin. When a person breathes an atmosphere loaded with the fumes of spirits, tobacco, turpentine, or of any other volatile substance, a portion of the fumes is taken up by the absorbing vessels of the lungs, and carried into the system, and there produces precisely the same effects as if introduced into the stomach. Dogs, for example, have been killed by being made to inhale the fumes of prussic acid for a few minutes. The lungs thus become a ready inlet to contagion, miasmata, and other poisonous influences diffused through the air we breathe.

From this general explanation of the structure and uses of the lungs, it is obvious that several conditions which it is our interest to know and observe are essential to the healthy performance of the important function of respiration. The first among these is a healthy original formation of the lungs. No fact in medicine is better established, says Dr. Combe, than that which proves the hereditary transmission, from parents to children, of a constitutional liability to pulmonary disease, and especially to consumption; yet, continues he, no condition is less attended to in forming matrimonial engagements.

Another requisite to the well-being of the lungs, and to the free and salutary exercise of respiration, is a due supply of rich and healthy blood. When, from defective food or impaired digestion, the blood is impoverished in quality, and rendered unfit for adequate nutrition, the lungs speedily suffer, and that often to a fatal extent. The free and easy expansion of the chest is also indispensable to the full play and dilation of the lungs. Whatever interferes with or impedes it, either in dress or in position, is obviously prejudicial to health. On the other hand, whatever favors the free expansion of the chest equally promotes the healthy action of the respiratory organs. Stays and corsets, and tight vests and waistbands, operate most injuriously, compressing as they do the thoracic cavity, and interfering with the healthy dilation of the lungs.

The admirable harmony established by the Creator between the various constituent parts of the animal frame, renders it impossible to pay regard to the conditions required for the health of any one, or to infringe the conditions required therefor, without all the rest participating in the benefit or injury. Thus, while cheerful exercise in the open air and in the society of equals is directly and eminently conducive to the well-being of the muscular system, the advantage does not stop there, the beneficent Creator having kindly so ordered it that the same exercise shall be scarcely less advantageous to the important function of respiration. Active exercise calls the lungs into play, favors their expansion, promotes the circulation of the blood through their substance, and leads to their complete and healthy development. The same end is greatly facilitated by that free and vigorous exercise of the voice, which so uniformly accompanies and enlivens the sports of the young, and which doubles the benefits derived from them considered as exercise. The excitement of the social and moral feelings which children experience while engaged in play is another powerful tonic, the influence of which on the general health ought not to be overlooked; for the nervous influence is as indispensable to the right performance of respiration as it is to the action of the muscles or to the digestion of food.

The regular supply of pure fresh air is another essential condition of healthy respiration, without which the requisite changes in the constitution of the blood, as it passes through the lungs, can not be effected. To enable the reader to appreciate this condition, it is necessary to consider the nature of the changes alluded to.

It is ascertained by analysis that the air we breathe is composed chiefly of the two gases nitrogen and oxygen, united in the ratio of four to one by volume, with exceedingly small and variable quantities of carbonic acid and aqueous vapor. No other mixture of these, or of any other gases, will sustain healthy respiration. To be more specific—atmospheric air consists of about seventy-eight per cent. of nitrogen, twenty-one per cent. of oxygen, and not quite one per cent. of carbonic acid. Such is its constitution when taken into the lungs in the act of breathing. When it is expelled from them, however, its composition is found to be greatly altered. The quantity of nitrogen remains nearly the same, but eight or eight and a half per cent. of the oxygen or vital air have disappeared, and been replaced by an equal amount of carbonic acid. In addition to these changes, the expired air is loaded with moisture. Simultaneously with these occurrences, the blood collected from the veins, which enters the lungs of a dark color and unfit for the support of life, assumes a florid hue and acquires the power of supporting life.

Physiologists are not fully agreed in explaining the processes by which these changes are effected in the lungs. All, however, agree that the change of the blood in the lungs is essentially dependent on the supply of oxygen contained in the air we breathe, and that air is fit or unfit for respiration in exact proportion as its quantity of oxygen approaches to, or differs from, that contained in pure air. If we attempt to breathe nitrogen, hydrogen, or any other gas that does not contain oxygen, the result will be speedy suffocation. If, on the other hand, we breathe air containing too great a proportion of oxygen, the vital powers will speedily suffer from excess of stimulus.

The chief chemical properties of the atmosphere are owing to the presence of oxygen. Nitrogen, which constitutes about four fifths of its volume, has been supposed to act as a mere diluent to the oxygen. Increase the proportion of oxygen in the atmosphere, and, as already stated, the vital powers will speedily suffer from excess of stimulus, the circulation and respiration become too rapid, and the system generally becomes highly excited. Diminish the proportion of oxygen, and the circulation and respiration become too slow, weakness and lassitude ensue, and a sense of heaviness and uneasiness pervades the entire system. As has been observed, air loses during each respiration a portion of its oxygen, and gains an equal quantity of carbonic acid, which is an active poison. When mixed with atmospheric air in the ratio of one to four, it extinguishes animal life. It is this gas that is produced by burning charcoal in a confined portion of common air. Its effect upon the system is well known to every reader of our newspapers. It causes dimness of sight, weakness, dullness, a difficulty of breathing, and ultimately apoplexy and death.[12]

Respiration produces the same effect upon air that the burning of charcoal does. It converts its oxygen, which is the aliment of animal life, into carbonic acid, which, be it remembered, is an active poison. Says Dr. Turner, in his celebrated work on chemistry, "An animal can not live in air which is unable to support combustion." Says the same author again, "An animal can not live in air which contains sufficient carbonic acid for extinguishing a candle." It will presently be seen why these quotations are made.

It is stated in several medical works that the quantity of air that enters the lungs at each inspiration of an adult varies from thirty-two to forty cubic inches. To establish more definitely some data upon which a calculation might safely be based, I some years ago conducted an experiment whereby I ascertained the medium quantity of air that entered the lungs of myself and four young men was thirty-six cubic inches, and that respiration is repeated once in three seconds, or twenty times a minute. I also ascertained that respired air will not support combustion. This truth, taken in connection with the quotations just made, establishes another and a more important truth, viz., that air once respired will not further sustain animal life. That part of the experiment by which it was ascertained that respired air will not support combustion is very simple, and I here give it with the hope that it may be tried at least in every school-house, if not in every family of our wide-spread country. It was conducted as follows:

I introduced a lighted taper into an inverted receiver (glass jar) which contained seven quarts of atmospheric air, and placed the mouth of the receiver into a vessel of water. The taper burned with its wonted brilliancy about a minute, and, growing dim gradually, became extinct at the expiration of three minutes. I then filled the receiver with water, and inverting it, placed its mouth beneath the surface of the same fluid in another vessel. I next removed the water from the receiver by breathing into it. This was done by filling the lungs with air, which, after being retained a short time in the chest, was exhaled through a siphon (a bent lead tube) into the receiver. I then introduced the lighted taper into the receiver of respired air, by which it was immediately extinguished. Several persons present then received a quantity of respired air into their lungs, whereupon the premonitory symptoms of apoplexy, as already given, ensued. The experiment was conducted with great care, and several times repeated in the presence of respectable members of the medical profession, a professor of chemistry, and several literary gentlemen, to their entire satisfaction.

Before proceeding further, I will make a practical application of the principles already established. Within the last ten years I have visited half of the states of the Union for the purpose of becoming acquainted with the actual condition of our common schools. I have therefore noticed especially the condition of school-houses. Although there is a great variety in their dimensions, yet there are comparatively few school-houses less than sixteen by eighteen feet on the ground, and fewer still larger than twenty-four by thirty feet, exclusive of our principal cities and villages. From a large number of actual measurements, not only in New York and Michigan, but east of the Hudson River and west of the great lakes, I conclude that, exclusive of entry and closets, when they are furnished with these appendages, school-houses are not usually larger than twenty by twenty-four feet on the ground, and seven feet in height. They are, indeed, more frequently smaller than larger. School-houses of these dimensions have a capacity of 3360 cubic feet, and are usually occupied by at least forty-five scholars in the winter season. Not unfrequently sixty or seventy, and occasionally more than a hundred scholars occupy a room of this size.

A simple arithmetical computation will abundantly satisfy any person who is acquainted with the composition of the atmosphere, the influence of respiration upon its fitness to sustain animal life, and the quantity of air that enters the lungs at each inspiration, that a school-room of the preceding dimensions contains quite too little air to sustain the healthy respiration of even forty-five scholars three hours—the usual length of each session; and frequently the school-house is imperfectly ventilated between the sessions at noon, and sometimes for several days together.

Mark the following particulars: 1. The quantity of air breathed by forty-five persons in three hours, according to the data just given, is 3375 cubic feet. 2. Air once respired will not sustain animal life. 3. The school-room was estimated to possess a capacity of 3360 cubic feet—fifteen feet less than is necessary to sustain healthy respiration. 4. Were forty-five persons whose lungs possess the estimated capacity placed in an air-tight room of the preceding dimensions, and could they breathe pure air till it was all once respired, and then enter upon its second respiration, they would all die with the apoplexy before the expiration of a three hours' session.

From the nature of the case, these conditions can not conveniently be fulfilled. But numerous instances of fearful approximation exist. We have no air-tight houses. But in our latitude, comfort requires that rooms which are to be occupied by children in the winter season, be made very close. The dimensions of rooms are, moreover, frequently narrowed, that the warm breath may lessen the amount of fuel necessary to preserve a comfortable temperature. It is true, on the other hand, that the quantity of air which children breathe is somewhat less than I have estimated. But the derangement resulting from breathing impure air, in their case, is greater than in the case of adults whose constitutions are matured, and who are hence less susceptible of injury. It is also true in many schools that the number occupying a room of the dimensions supposed is considerably greater than I have estimated. Moreover, in many instances, a great proportion of the larger scholars will respire the estimated quantity of air.

Again, all the air in a room is not respired once before a portion of it is breathed the second, or even the third and fourth time. The atmosphere is not suddenly changed from purity to impurity—from a healthful to an infectious state. Were it so, the change, being more perceptible, would be seen and felt too, and a remedy would be sought and applied. But because the change is gradual, it is not the less fearful in its consequences. In a room occupied by forty-five persons, the first minute, thirty-two thousand four hundred cubic inches of air impart their entire vitality to sustain animal life, and, mingling with the atmosphere of the room, proportionately deteriorate the whole mass. Thus are abundantly sown in early life the fruitful seeds of disease and premature death.

This detail shows conclusively sufficient cause for that uneasy, listless state of feeling which is so prevalent in crowded school-rooms. It explains why children that are amiable at home are mischievous in school, and why those that are troublesome at home are frequently well-nigh uncontrollable in school. It discloses the true cause why so many teachers who are justly considered both pleasant and amiable in the ordinary domestic and social relations, are obnoxious in the school-room, being there habitually sour and fretful. The ever-active children are disqualified for study, and engage in mischief as their only alternative. On the other hand, the irritable teacher, who can hardly look with complaisance upon good behavior, is disposed to magnify the most trifling departure from the rules of propriety. The scholars are continually becoming more ungovernable, and the teacher more unfit to govern them. Week after week they become less and less attached to him, and he, in turn, becomes less interested in them.

This detail explains, also, why so many children are unable to attend school at all, or become unwell so soon after commencing to attend, when their health is sufficient to engage in other pursuits. The number of scholars answering this description is greater than most persons are aware of. In one district that I visited a few years ago in the State of New York, it was acknowledged by competent judges to be emphatically true in the case of not less than twenty-five scholars. Indeed, in that same district, the health of more than one hundred scholars was materially injured every year in consequence of occupying an old and partially-decayed house, of too narrow dimensions, with very limited facilities for ventilation. The evil, even after the cause was made known, was suffered to exist for years, although the district was worth more than three hundred thousand dollars. And what was true[13] of this school, is now, with a few variations, true in the case of scores, if not hundreds of schools with which I am acquainted, from far-famed New England to the Valley of the Mississippi.

This detail likewise explains why the business of teaching has acquired, and justly too, the reputation of being unhealthy. There is, however, no reason why the health of either teacher or pupils should sooner fail in a well-regulated school, taught in a house properly constructed, and suitably warmed and ventilated, than in almost any other business. If this statement were not true, an unanswerable argument might be framed against the very existence of schools; and it might clearly be shown that it is policy, nay, duty, to close at once and forever the four thousand school-houses of Michigan, and the hundred thousand of the nation, and leave the rising generation to perish for lack of knowledge. But our condition in this respect is not hopeless. The evil in question may be effectually remedied by enlarging the house, or, which is easier, cheaper, and more effectual, by frequent and thorough ventilation. It would be well, however, to unite the two methods.

In the winter of 1841-2, I visited a school in which the magnitude of the evil under consideration was clearly developed. Five of the citizens of the district attended me in my visit to the school. We arrived at the school-house about the middle of the afternoon. It was a close, new house, eighteen by twenty-four feet on the ground—two feet less in one of its dimensions than the house concerning which the preceding calculation is made. There were present forty-three scholars, the teacher, five patrons, and myself, making fifty in all. Immediately after entering the school-house, one of the trustees remarked to me, "I believe our school-house is too tight to be healthy." I made no reply, but secretly resolved that I would sacrifice my comfort for the remainder of the afternoon, and hazard my health, and my life even, to test the accuracy of the opinions I had entertained on this important subject. I marked the uneasiness and dullness of all present, and especially of the patrons, who had been accustomed to breathe a purer atmosphere. School continued an hour and a half, at the close of which I was invited to make some remarks. I arose to do so, but was unable to proceed till I opened the outer door, and snuffed a few times the purer air without. When I had partially recovered my wonted vigor, I observed with delight the renovating influence of the current of air that entered the door, mingling with and gradually displacing the fluid poison that filled the room, and was about to do the work of death. It seemed as though I was standing at the mouth of a huge sepulcher, in which the dead were being restored to life. After a short pause, I proceeded with a few remarks, chiefly, however, on the subject of respiration and ventilation. The trustees, who had just tested their accuracy and bearing upon their comfort and health, resolved immediately to provide for ventilation according to the suggestions in the article on school-houses in the last chapter of this work.

Before leaving the house on that occasion, I was informed an evening meeting had been attended there the preceding week, which they were obliged to dismiss before the ordinary exercises were concluded, because, as they said, "We all got sick, and the candles went almost out." Little did they realize, probably, that the light of life became just as nearly extinct as did the candles. Had they remained there a little longer, both would have gone out together, and there would have been reacted the memorable tragedy of the Black Hole in Calcutta, into which were thrust a garrison of one hundred and forty-six persons, one hundred and twenty-three of whom perished miserably in a few hours, being suffocated by the confined air.

What has been said in the preceding pages on the philosophy of respiration was first given to the public nearly ten years ago, in a report of the author's in the State of New York. He has since seen the same sentiments inculcated by many of our most eminent practical educators, some of whom had written upon the subject at an earlier date. Allen and Pepy showed by experiment that air which has been once breathed contains eight and a half per cent. of carbonic acid, and that no continuance of the respiration of the same air could make it take up more than ten per cent. Air, then, when once respired, has taken up more than four fifths of the amount of this noxious gas that it can be made to by any number of breathings.

Dr. Clark, in his work on Consumption, remarks as follows: "Were I to select two circumstances which influence the health, especially during the growth of the body, more than others, and concerning which the public, ignorant at present, ought to be well informed, they would be the proper adaptation of food to difference of age and constitution, and the constant supply of pure air for respiration." Dr. William A. Alcott, who has given especial attention to this subject, after quoting the preceding remark of Dr. Clark, adds: "We believe this is the opinion of all medical men who have studied the constitution of man, and its relation to outward objects."

A distinguished surgeon[14] of Leeds, England, goes somewhat further in praising pure air than most of his contemporaries. "Be it remembered," says he, "that man subsists more upon air than upon his food and drink." There is some novelty in this remark, I admit: but is it not truthful? Men have been known to live three weeks without eating. But exclude the atmospheric air from the lungs for the space of three minutes, and death generally ensues. We thus see that life will continue with abstinence from food three thousand times as long as it is safe to protract an atmospheric fast.

Let us take another view of the subject. Men usually eat three times in twenty-four hours. This is all that is necessary to, or compatible with, the enjoyment of uninterrupted good health. But we involuntarily breathe nearly thirty thousand times in the same length of time. We need, then, fresh supplies of pure air ten thousand times as often as it is necessary to partake of meals. Is it not apparent, then, that man subsists more upon air than upon his food and drink?

The atmosphere which we so frequently inhale, and upon which our well-being so much depends, surrounds the earth to the height of about forty-five miles. The surface of the earth contains about two hundred millions of square miles, and it is estimated that there dwell upon it eight hundred millions of inhabitants. This gives to each individual about eleven cubic miles of air. But the air is breathed by the inferior animals as well as by man. It is also rendered impure by combustion. If by both of these causes ten times as much air is consumed as by man, there is still left one cubic mile of uncontaminated atmospheric air to every human being dwelling upon the surface of the earth. This would allow him to live more than twice the age allotted to man, without breathing any portion of the atmosphere a second time. And still, as if to avoid the possibility of evil to man on this account, the beneficent Creator has wisely so ordered, that while we do not interfere with the laws of Nature, there is not even the possibility of rebreathing respired air until it has been purified and restored to its natural and healthful state; for carbonic acid, the vitiating product of respiration, although immediately fatal to animals, constitutes the very life of vegetation. When brought in contact with the upper surface of the green leaves of trees and plants, and acted upon by the direct solar rays, this gas is decomposed, and its carbon is absorbed to sustain, in part, the life of the plant, by affording it one element of its food, while the oxygen is liberated and restored to the atmosphere. Vegetables and animals are thus perpetually interchanging kindly offices, and each flourishes upon that which is fatal to the other. It is in this way that the healthful state of the atmosphere is kept up. Its equilibrium seems never to be disturbed, or, if disturbed at all, it is immediately restored by the mutual exchange of poison for aliment, which is constantly going on between the animal and vegetable worlds. This interchange of kindly offices is constantly going on all over the earth, even in the highest latitudes, and in the very depths of winter; for air which has been respired is rarefied, and, when thrown from the lungs, ascends, and is thus not only out of our reach, whereby we are protected from respiring it a second time, but this (to us) deadly poison falls into the great aËrial current which is constantly flowing from the polar to the tropical regions, where it is converted into vegetable growth. The oxygen which is exhaled in the processes of tropical vegetation, heated and rarefied by the vertical rays of the sun, mounts to the upper regions of the atmosphere, and, falling into a returning current, in its appointed time revisits the higher latitudes. So wisely has the Divine Author ordered these processes, that air, in its natural state[15] in any part of the world, does not contain more than one half of one per cent. of carbonic acid gas, although, as already stated, air which has been once respired contains eight and a half per cent. of this gas, which is at least seventeen times its natural quantity.

There are other agencies than carbonic acid gas which in civic life render the atmosphere impure. Of this nature is carbureted hydrogen gas, which is produced in various ways. This, says Dr. Comstock, is immediately destructive to animal life, and will not support combustion. It exists in stagnant water, especially in warm weather, and is generated by the decomposition of vegetable products. Dr. Arnott expresses the conviction that the immediate and chief cause of many of the diseases which impair the bodily and mental health of the people, and bring a considerable portion prematurely to the grave, is the poison of atmospheric impurity, arising from the accumulation in and around their dwellings of the decomposing remnants of the substances used for food and in their arts, and of the impurities given out from their own bodies. If you allow the sources of aËrial impurity to exist in or around dwellings, he continues, you are poisoning the people; and while many die at early ages of fevers and other acute diseases, the remainder will have their health impaired and their lives shortened.

There are many instances on record where the progress of an epidemic has been speedily arrested by ventilation. A striking instance is given by the writer last quoted. "When I visited Glasgow with Mr. Chadwick," says he, "there was described to us one vast lodging-house, in connection with a manufactory there, in which formerly fever constantly prevailed, but where, by making an opening from the top of each room through a channel of communication to an air-pump common to all the channels, the disease had disappeared altogether. The supply of pure air obtained by that mode of ventilation was sufficient to dilute the cause of the disease, so that it became powerless."

Sulphureted hydrogen gas is also exceedingly poisonous to the lungs and to every part of the system. When pure, this gas is described as instantly fatal to animal life. Even when diluted with fifteen hundred times its bulk of air, it has been found so poisonous as to destroy a bird in a few seconds. "This gas," says Dr. Dunglison, in his Elements of Hygiene, "is extremely deleterious.[16] When respired in a pure state it kills instantly; and its deadly agency is rapidly exerted when put in contact with any of the tissues of the body, through which it penetrates with astonishing rapidity. Even when mixed with a portion of air, it has proved immediately destructive. Dr. Paris refers to the case of a chemist of his acquaintance, who was suddenly deprived of sense as he stood over a pneumatic trough in which he was collecting this gas. From the experiments of Dupuytren and Thenard, air that contains a thousandth part of sulphureted hydrogen kills birds immediately. A dog perished in air containing a hundredth part, and a horse in air containing a fiftieth part of it."

The preceding are far from being all the causes of atmospheric impurity. Besides these, there are numerous exhalations, as well as gases, that are poisonous. Some of these exhalations are more abundant in the night, and about the time of the morning and evening twilight. "Hence the importance," says a writer on health, "to those who are feeble, of avoiding the air at all hours except when the sun is considerably above the horizon."

Although the atmosphere, in its natural state, is not at all times perfectly pure, still it is comparatively so, and especially in the daytime. All, therefore, who would retain and improve their health, should inhale the open air as much as possible, even though they can not, like Franklin's Methusalem,[17] be always in it. This remark is applicable to both sexes, and to every age and condition of life.

The following, from the pen of an American author[18] who has written much and well on physical education, is pertinent to the subject under consideration: "We breathe bad air principally as the production of our own bodies. Here is the source of a large share of human wo; and to this point must his attention be particularly directed who would save himself from disease, and promote, in the highest possible degree, his health and longevity. We must avoid breathing over the carbonic acid gas contained in the tight or unventilated rooms in which we labor or remain for a long time, whether parlors, school-rooms, counting-rooms, bed-rooms, shops, or factories. The individual who lives most according to nature—who observes with most care the laws of life and health—must necessarily throw off much carbonic acid from his lungs, if not from his skin. It does not follow, however, that because this gas is formed we are obliged to inhale it. We may change our position, change our clothing, ventilate our rooms of all sorts, shake up our bed-clothing often and air our bed, and use clean, loose, and porous clothing by night and by day. We may thus very effectually guard against injuries from a very injurious agent.

"One thing should be remembered in connection with this subject which is truly encouraging. The more we accustom ourselves to pure air, the more easily will our lungs and nasal organs detect its presence. He who has redeemed his senses and restored his lungs to integrity, like him who has redeemed a conscience once deadened, is so alive to every bad impression made upon any of these, that he can often detect impurity around or within him, and thus learn to avoid it. It will scarcely be possible for such a person long to breathe bad air, or nauseous or unwholesome effluvia, without knowing it, and learning to avoid the causes which produce it. Such a person will not neglect long to remove the impurities which accumulate so readily on the surface of his body, or suffer himself to use food or drink which induces flatulence, and thus exposes either his intestines or his lungs, or the lungs of others, to that most extremely poisonous agent, sulphureted hydrogen gas. Nor will he be likely to permit the accumulation of filth, liquid or solid, around or in his dwelling. There are those whose senses will detect a very small quantity of stagnant water, or vinegar, or other liquids, or fruit, or changed food in the house, or even the presence of those semi-putrid substances, wine and cider. But some will indeed say that such integrity of the senses would be an annoyance rather than a blessing. On the same principle, however, would a high degree of conscientiousness in regard to right and wrong in moral conduct be a curse to us. If it be desirable to have our physical sense of right and wrong benumbed, it is so to have our moral sense benumbed also. Yet what person of sense ever complained of too tender a conscience, or too perfect a sense of right and wrong in morals?"

Exercise of the Lungs.—Judicious exercise of the lungs, in the opinion of that eminent physiologist, Dr. Andrew Combe, is one of the most efficacious means which can be employed for promoting their development and warding off their diseases. In this respect the organs of respiration closely resemble the muscles and all other organized parts. They are made to be used, and if they are left in habitual inactivity, their strength and health are unavoidably impaired; while, if their exercise be ill-timed or excessive, disease will as certainly follow.

The lungs may be exercised directly by the use of the voice in speaking, reading aloud, or singing, and indirectly by such kinds of bodily or muscular exertion as require quicker and deeper breathing. In general, both ought to be conjoined. But where the chief object is to improve the lungs, those kinds which have a tendency to expand the chest and call the organs of respiration into play ought to be especially preferred. Rowing a boat, fencing, quoits, shuttlecock, the proper use of skipping the rope, dumb-bells, and gymnastics are of this description, and have been recommended for this purpose. All of them employ actively the muscles of the chest and trunk, and excite the lungs themselves to freer and fuller expansion. Climbing up a hill is, for the same reason, an exercise of high utility in giving tone and freedom to the pulmonary functions. Where, either from hereditary predisposition or accidental causes, the chest is unusually weak, every effort should be made, from infancy upward, to favor the growth and strength of the lungs, by the habitual use of such of these exercises as can most easily be practiced. The earlier they are resorted to, and the more steadily they are pursued, the more certainly will their beneficial results be experienced.

If the direct exercise of the lungs in practicing deep inspiration, speaking, reading aloud, and singing, is properly managed and persevered in, particularly before the frame has become consolidated, it will exert a very beneficial influence in expanding the chest, and giving tone and imparting health to the important organs contained in it. As a preventive measure, Dr. Clark, in his treatise on Consumption and Scrofula, recommends the full expansion of the chest in the following manner: "We desire the young person, while standing, to throw his arms and shoulders back, and, while in this position, to inhale slowly as much air as he can, and repeat this exercise at short intervals several times in succession. When this can be done in the open air it is most desirable, a double advantage being thus obtained from the practice. Some exercise of this kind should be adopted daily by all young persons, more especially by those whose chests are narrow or deformed, and should be slowly and gradually increased."

In this preventive measure recommended by Dr. Clark, some of our most eminent physiologists heartily concur. They also express the opinion that, for the same reason, even the crying and sobbing of children, when not caused by disease, contribute to their future health. Dr. Combe says, "The loud laugh and noisy exclamations attending the sports of the young have an evident relation to the same beneficial end, and ought, therefore, to be encouraged." But beneficial as the direct exercise of the lungs is thus shown to be, in expanding and strengthening the chest, its influence extends still further, and, as we have already seen, contributes greatly to promote the important process of digestion. If, therefore, the lungs be rarely called into active exercise, not only do they suffer, but an important aid to digestion being withdrawn, the stomach and bowels also become weakened, and indigestion and costiveness ensue.

The exercise of what has not unaptly been called Vocal Gymnastics, and the loud and distinct speaking enforced in many of our schools, not only fortify the vocal organs against the attacks of disease, but tend greatly to promote the general health. For this purpose, also, as well as for its social and moral influences, vocal music should be introduced into all our schools. That by these and like exercises deep inspirations and full expirations are encouraged, any one may become convinced who will attend to what passes in his own body while reading aloud a single paragraph.

There is danger of exercising the lungs too much when disease exists in the chest. At such times, not only speaking, reading aloud, and singing, but ordinary muscular exertion, ought to be refrained from, or be regulated by professional advice. When a joint is sore or inflamed, we know that motion impedes its recovery. When the eye is affected, we, for a similar reason, shut out the light. So, when the stomach is disordered, we respect its condition, and are more careful about diet. The lungs demand a treatment founded on the same general principle. When inflamed, they should be exercised as little as possible. All violent exercise ought, therefore, to be refrained from during at least the active stages of a cold; but colds may often be entirely prevented at the time of exposure by a proper exercise of the lungs.

In conversing with an eminent physician recently on this subject, he expressed the conviction that one of the most effectual methods of warding off a cold, when exposed by wet feet or otherwise, is to take frequent deep inhalations of air. By this means the carbonic acid, which the returning circulation deposits in the lungs, is not only more effectually disengaged, but, at the same time, the greater amount of oxygen that enters the lungs and combines with the blood quickens the circulation, and thus, imparting increased vitality to the system, enables it more effectually to resist any attack that may be induced by unusual exposure.

A late medical writer, who has become quite celebrated in this country for the successful treatment of pulmonary consumption,[19] expresses the opinion that, to the consumptive, air is a most excellent medicine, and "far more valuable than all other remedies." He thinks it "the grand agent in expanding the chest." In urging the importance of habitually maintaining an erect position, he expresses the conviction that "practice will soon make sitting or standing perfectly erect vastly more agreeable and less fatiguing than a stooping posture." To persons predisposed to consumption, these hints, he thinks, are of the greatest importance. While walking, he says, "the chest should be carried proudly erect and straight, the top of it pointing rather backward than forward." To illustrate the advantages of habitually maintaining this position, he refers to the North American Indians, who never had consumption, and who are remarkable for their perfectly erect posture while walking. "Next to this," he adds, "it is of vast importance to the consumptive to breathe well. He should make a practice of taking long breaths, sucking in all the air he can, and holding it in the chest as long as possible." He recommends the repetition of this a hundred times a day, and especially with those who have a slight cold or symptoms of weak lungs. When practiced in pure cold air, its advantages are most apparent. To increase the benefits resulting from this practice, he recommends the use of the "inhaling tube." He thinks that inhaling tubes made of silver or gold are much better than those made of wood or India-rubber. In this opinion I fully concur, for I think with him that gold and silver tubes will not so readily "contract any impure or poisonous matter." But there is another and a stronger reason why I prefer silver, and especially gold inhaling tubes, to those made of wood or India-rubber. They would be more highly prized and more frequently used.

The same writer entertains the belief that about one third of all the consumptions originate from weakness of the abdominal belts. He hence, in such cases, recommends the use of the "abdominal supporter." In order to favor an erect posture and an open chest, he also recommends the use of "shoulder-braces." He says the proper use of these, with other remedies, will "entirely prevent the possibility of consumption, from whatever cause." The inhaling-tube, together with the shoulder-braces and supporter when needed, he says are perfect preventives, and should not be neglected; for if the shoulders are kept off the chest, and the abdomen is well supported, and then an inhaling tube is faithfully used, "the lungs can never become diseased. Any person in this way, who chooses to take the trouble, can have a large chest and healthy lungs."

When persons have contracted disease they may require these artificial helps; but it should be borne in mind that an all-wise and beneficent Creator has kindly given to each of his creatures two inhaling tubes, admirably adapted to their wants. He has also furnished them with a set of abdominal muscles which, when properly used, have generally been found to supersede the necessity of artificial "supporters." He has, moreover, in the plenitude of his goodness, furnished each member of the human family with a good pair of shoulder-braces. It should also be borne in mind that Nature's shoulder-braces improve by use, while the artificial ones not only soon fail, but their very use generally impairs the healthy action of the natural ones; for these, like all other muscles, improve by use and become enfeebled by disuse. Parents and teachers, then, and all who have the care of the young, should encourage the correct use of Nature's inhaling tubes, shoulder-braces, and abdominal supporters; for in this way they have it in their power not only to supersede the necessity of resorting to artificial ones later in life, but of preventing much of human misery, and contributing to the permanent elevation of the race.

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