Rensselaer Republican, Volume 16, Number 38, Rensselaer, Jasper County, 29 May 1884 — THE BREATH OF LIFE. [ARTICLE]

THE BREATH OF LIFE.

Man comes into the world with a cry, not of joy or of pain or of fear, but a ▼ocal sound announcing that a being has taken the first breath of life, and that a new independent existence is begun. This cry attends the beginning of a wonderful group and series of phenomena. A cold-blooded animal, virtually, with a mixture of venous and arterial blood circulating through a great part of the body, becomes, with the first breath, a warm-blooded animal; the single heart becomes a double heart, <me side sending blood to the lungs, and the other side to the system at large; all the so-called vital processes take on an immensely increased activity; there begins at that moment vigorous muscular movement; the special senses, especially sight and hearing, are rapidly developed; the new being can digest, feel, smell, and taste;and, finally, intelligence begins to dawn. All these marvellous changes begin with the first act by which air is taken into the lungs. Nearly every important function in the body is dependent, directly or indirectly, upon what is called respiration. Without a circulation of the blood, there can be no digestion, no absorption or Becretion, or nutrition. Without respiration there can be no circulation of the blood; and without circulation, there can be no respiration. It is an error to suppose that the mere existance of air into the lungs constitutes respiration. A man may suffocate although his lungs be abundantly supplied with fresh air. Persons with extensive valvular disease of of the heart which impedes the circulation suffer terribly from want of air, even though the action of the lungs be perfect. In order to respire, the air must first be inhaled; and the blood passing throngh the lungs takes up the oxygen and carrio* it to every part of tho body. Circulating in the innumerable and minute capillary blood-vessels, some of which are not more than one-six-thous-

andtli of an inch in diameter, the oxygen is taken np and ixsod by every highly organized tissue and organ of the body. This appropriation of oxygen by the tissues really constitutes respiration, and the taking of oxygen into the lungs »nd its absorption of the circulating blood are simply the means of conveying oxygen to the party; but this demand on the part of the tissues for oxygen is so imperative, that life continues for hut a few minutes after the supply of dxygen is abolished. It is strange that so little was known of the processes of respiration, that up to the time of Lavoisier (about the year 1776) physiologists had really no definite idea of the mechanism of this function; and it is strangor still that the first statement pointing to the idea that the air taken iuto the lungs did anything more than cool the blood, was made, not by a physiologist, but by the great painter Leonardo da "Vinci, in the latter part of the fifteenth oentury. „ The year 1776, when the United States became a nation, was a momentous year in discoveries bearing upon the function of respiration. In this year, the celebrated Dr. Priestley discovered oxygen. At about the same time, Lavoisier, the father of modern chemistry, noted the consumption of ♦ oxygen in respiration, and the discharge of carbonic acid by the lungs. From 1776, the year of the discovery of oxygen, dates our first knowledge of the composition and uses of the air wo breathe.

When we investigate the wonders in ourselves, we are at once struck with the dependence upon one another of the important functions of the body; and we see, as was shown by Boyle, the founder of the Royal Society of London, in 167Q r that air is necessary to the life of all animals. Even those animals that Jive under water require air, which they obtain from the water holding air in solution. It must be interesting, therefore, and it is certainly useful to study the processes by which every part of every living being is supplied with oxygen. The air we breathe is composed of a mechanical mixture of oxygen and nitrogen, in the proportion of one part of the firmer to about four parts of the latter. Oxygen is the only agent concerned in respiration, the nitrogen •serving to dilute the respirable gas. A man takes a fresh supply of air into the lungs, or breathes about eighteen times per minute. The lungs contain usually about 200 cubic inches of air, but only about twenty cubic finches are charged with each respiratory apt These acta of respiration, as I have said before; are absolutely essential to life. They begin with the beginning of our independent existence, and they continue uninterruptedly to the end of

life. Sleeping or waking, sensible or the acts of respiration go on. The conditions of our existenoe require that we shoud be able to modify the respiratory acts, as in speaking, singing, blowihg, etc.; but, although we can nbld the breath for a time, we cannot arrest the breathing permanently, by a voluntary effort, any more than we can forget to breath.

There is a most wonderful and efficient provision in the nervous system by which the acts of respiration are maintained in their normal frequency,. Just beneath the brain, and at the very beginning of the spinal cord, in what is called the medulla oblongata, is a little mass of nerve-cells which preside over the respiratory movements. When these cells are injured, respiration instantly leases. This is the spot wounded by the skillful bull-fighters in the sport that is so popular in Spanish countries. The infuriated bull, with eyes closed and head low, rushes madly at his tormentor. When it is time to end the cruel play, the toreador, stepping to one side, plunges his sword intothe back of the neck and divides the medulla oblongata. The animal instantly stops breathing; and this is the most,sudden and painless mode of death. Thanks to recent experiment, the mechanism of the influence of the medulla oblongata ove'r respiration is now pretty well understood. /This part of the nervous system, like other parts, is supplied with arterial blood, which contains oxygen. Whenever the the oxygen in the blood circulating through the medulla oblongata becomes in the slightest degree diminished in quantity, an involuntary impuls is sent to the muscles which dilate the chest, and fresh air is taken into the lungs. When the oxygen thus taken in begins to be consumed, another impulse is sent out, and another inspiration takes place. These impulses occur about eight times per minute, or as often as we respire, and they keep the body supplied with the proper quantity of oxygen. They are entirely unconscious and involuntary; and this is the reason why our ordinary acts of respiration are involuntary and continue even when we are unconscious.

Let us suppose, however that there is a deficiency of fresh air, and that we are in danger of suffocation! The unconscious impression normally made upon the medulla oblongata becomes exaggerated and is conveyed to the brain, where it is recognized as a sense of suffocation. We then feel most acutely the sense of want of air and make violent voluntary efforts to breathe. If these be unsuccessful, we soon become insensible and die of asphyxia. The gentle movements by which the air is insensibly changed into the lungs are accomplished by the action of muscles which raise the oblique ribs and increase the width and depth of the chest, and a descent of the diaphragm, which increases its vertical diameter.

The diaphragm is a muscle lying between the chest and the abdomen: and, as it contracts, it draws the elastic lungs downward. With each of these acts, which are called movements of inspiration, about twenty cubic inches of fresh air are drawn into tho lungs. But the oxygen passes into the blood through the thin coat of the capillary blood-vessels in the air-cells situated in the deepest parts of the lungs; and, if the lungs have a normal capacity of 200 cubic inches and only twenty cubic inches of fresh air are taken in with each respiratory act, how is it that the fresh air is enabled to get to these air cells ?

This is explained by wKStr is known as the law of diffusion of gases. If we open a bottle of ammonia, for example, the vapor diffuses in the surrounding air and is recognized by the sense of smell. Such a process of diffusion tabes place very rapidly in the air in the lungs. The air-cells are constantly receiving from the blood a heavy, irrespirable gas, carbonic acid; and the vitiated air is constantly diffusing itself outward, the fresh air taking its place by diffusion towards the air-cells. It is in this way that carbonic acid is constantly thrown off by expiration and oxygen is supplied to the blood. But a small portion of the oxygen taken in at each respiratory act is absorbed in the lungs. If we assume that twenty cubic inches of air are inspired, this contains one-fifth of twenty, or four cubic inches of oxygen, of which'one cubic in oh only is taken up by the blood* — --- -- Expiration, bt the Expulsion of air from the lungs, is normally a passive process, and is due to the reaction of the elastic walls of the chest' and of the elastic tissue of the lungs after the contraction of the mnscles which have dilated the chest ceases; but, by voluntary efforts, we can draw the walls of the chest downward and press the diaphragm upward by contraction of the abdominal muscles, so as to produce the acts of blowing, singing, etc., which we so often perforin.

The mechanism of respiration after the air has penetrated to the air-cells is most interesting and curious. The air cells are little vesicles measuring from one two-lrund j edth to or e-ninetietli of an inch in diamdter; and in the deepest portion of the lungs, the air is separated 'from the blood by an excessively thin and pecmeable membrane which is the single coat of the capillary blood-vessels. The blood contains millions upon millions of minute red corpuscles, which have a remarkable affinity for .oxygen. These corpuscles seize upon the oxygen of the air with wonderful avidity; but they absorb little or no nitrogen. The oxygen thus absorbed instantly forms a union with the coloring matter of the corpuscles to every part of the organism. Every tissue and organ of the body,, for its life's work, needs oxygen. These parts, then, take up the oxygen carried to them by the blood-corpuscles and give off carbonic acid gas. The carbonic acid is taken up t>v the blear liquid of the blood in which the corpuscles, float, is carried back to the lungs, and is there discharged in the act of expiration. 4^ v When the blood loses its carbonic aeid and takes up oxygen in the lungs, it instantly changes freon a dark-blue to a Vivid-red color. Tnere is a very beautiful experiment, which I make

every year as a demonstration to a , medical olass, to illustrate this change! If we teke out the Inngs from an animal jUst killed, we can imitate, by means of a bellows, the acts of respiration. If we now inject through the lungs dark, venous blood, it gives off carbonic acid and takes up oxygen, as it does during life, and, as it comes from the lungs, it has a briliiaht red color. From what has been stated above, it is evident; that the real and essential process of respiration and the actual function of the breath of life take place, not in the lungs, not in the blood, but in the tissues themselves. When a bit of living mnscle is placed under a bell-glass containing air,- it absorbs oxygen and actually breathes, without the intervention of lungs or even of blood. An animal dies, and dies of suffocation, when the blood-cor-puscles, which cany oxygen to the tissues are paralyzed by poisoning with carbonic oxide gas, when the greatest part of the blood is drawn from the body, or when the great blood-vessel (the aorta) which supplies the body is tied, in essentially the same way as when strangled by a rope tied around the neck.

How remarkable and wonderful has been the progress of knowledge of ourselves within a little more than a single century! We knew nothing of physiology, because we did not know of the circulation of the blood, until early in jjhe seventeenth century; but how- little did we know, even after Harvey had taught the circulation, until the year 1778, when Priestly discovered oxygen and Lavoisier showed that oxygen really constituted the breath of life.— Dr. Austin Hint, Jr., in Youths’ Companion. i