  Through the movements of the blood and the lymph, materials entering the body are transported to the cells, and wastes formed at the cells are carried to the organs which remove them from the body. We are now to consider the passage of materials from outside the body to the cells and vice versa. One substance which the body constantly needs is oxygen, and one which it is constantly throwing off is carbon dioxide. Both of these are constituents of The Atmosphere.—The atmosphere, or air, completely surrounds the earth as a kind of envelope, and comes in contact with everything upon its surface. It is composed chiefly of oxygen and nitrogen,29 but it also contains a small per cent of other substances, such as water-vapor, carbon dioxide, and argon. All of the regular constituents of the atmosphere are gases, and these, as compared with liquids and solids, are very light. Nevertheless the atmosphere has weight and, on this account, exerts pressure upon everything on the earth. At the sea level, its pressure is nearly fifteen pounds to the square inch. The atmosphere forms an essential part of one's physical environment and serves various purposes. The process[pg 077] Respiration.—As usually defined, respiration, or breathing, consists of two simple processes—that of taking air into special contrivances in the body, called the lungs, and that of expelling air from the lungs. The first process is known as inspiration; the second as expiration. We must, however, distinguish between respiration by the lungs, called external respiration, and respiration by the cells, called internal respiration. The purpose of respiration is indicated by the changes that take place in the air while it is in the lungs. Air entering the lungs in ordinary breathing parts with about five per cent of itself in the form of oxygen and receives about four and one half per cent of carbon dioxide, considerable water-vapor, and a small amount of other impurities. These changes suggest a twofold purpose for respiration: 1. To obtain from the atmosphere the supply of oxygen needed by the body. 2. To transfer to the atmosphere certain materials (wastes) which must be removed from the body. The chief organs concerned in the work of respiration are The Lungs.—The lungs consist of two sac-like bodies suspended in the thoracic cavity, and occupying all the space not taken up by the heart. They are not simple sacs, however, but are separated into numerous divisions, as follows: 1. The lung on the right side of the thorax, called the right lung, is made up of three divisions, or lobes, and the left lung is made up of two lobes. 2. The lobes on either side are separated into smaller[pg 078]
Fig. 33 Fig. 33—Lungs and air passages seen from the front. The right lung shows the lobes and their divisions, the lobules. The tissue of the left lung has been dissected away to show the air tubes. 3. In the lobule the air tube divides into a number of smaller tubes, each ending in a thin-walled sac, called an infundibulum. The interior of the infundibulum is separated into many small spaces, known as the alveoli, or air cells. The lungs are remarkable for their lightness and delicacy of structure.30 They consist chiefly of the tissues that form their sacs, air tubes, and blood vessels; the membranes that line their inner and outer surfaces; and the connective tissue that binds these parts together. All these tissues are more or less elastic. The relation of the different parts of the lungs to[pg 079] Air Passages.—The air passages consist of a system of tubes which form a continuous passageway between the outside atmosphere and the different divisions of the lungs. The air passes through them as it enters and leaves the lungs, a fact which accounts for the name.
Fig. 34 Fig. 34—Model of section through the head, showing upper air passages and other parts. 1. Left nostril. 2. Pharynx. 3. Tongue and cavity of mouth. 4. Larynx. 5. Trachea. 6. Esophagus. The incoming air first enters the nostrils. These consist of two narrow passages lying side by side in the nose, and connecting with the pharynx behind. The lining of the nostrils, called mucous membrane is quite thick, and has its surface much extended by reason of being spread over some thin, scroll-shaped bones that project into the passage. This membrane is well supplied with blood vessels and secretes a considerable quantity of liquid. Because of the nature and arrangement of the membrane, the nostrils are able to warm and moisten the incoming air, and to free it from dust particles, preparing it, in this way, for entrance into the lungs (Fig. 34). The nostrils are separated from the mouth by a thin layer of bone, and back of both the mouth and the nostrils is the pharynx. The pharynx and the mouth serve as parts of the food canal, as well as air passages, and are[pg 080] From the larynx the air enters the trachea, or windpipe. This is a straight and nearly round tube, slightly less than an inch in diameter and about four and one half inches in length. Its walls contain from sixteen to twenty C-shaped, cartilaginous rings, one above the other and encircling the tube. These incomplete rings, with their openings directed backward, are held in place by thin layers of connective and muscular tissue. At the lower end the trachea divides into two branches, called the bronchi, each of which closely resembles it in structure. Each bronchus separates into a number of smaller divisions, called the bronchial tubes, and these in turn divide into still smaller branches, known as the lesser bronchial tubes (Fig. 33). The lesser bronchial tubes, and the branches into which they separate, are the smallest of the air tubes. One of these joins, or expands into, each of the minute lung sacs, or infundibula. Mucous membrane lines all of the air passages. General Condition of the Air Passages.—One necessary condition for the movement of the air into and from the lungs is an unobstructed passageway.31 The air passages[pg 081]
Fig. 35 Fig. 35—Ciliated epithelial cells. A. Two cells highly magnified. c. Cilia, n. Nucleus. B. Diagram of a small air tube showing the lining of cilia. The air passages are kept clean by cells especially adapted to this purpose, known as the ciliated epithelial cells. These are slender, wedge-shaped cells which have projecting from a free end many small, hair-like bodies, called cilia (Fig. 35). They line the mucous membrane in most of the air passages, and are so placed that the cilia project into the tubes. Here they keep up an inward and outward wave-like movement, which is quicker and has greater force in the outward direction. By this means the cilia are able to move small pieces of foreign matter, such as dust particles and bits of partly dried mucus, called phlegm, to places where they can be easily expelled from the lungs.32
Fig. 36 Fig. 36—Terminal air sacs. The two large sacs are infundibula; the small divisions are alveoli. (Enlarged.) [pg 082]
Fig. 37 Fig. 37—Inner lung surface (magnified), the blood vessels injected with coloring matter. The small pits are alveoli, and the vessels in their walls are chiefly capillaries.
Fig. 38 Fig. 38.—Diagram to show the double movement of air and blood through the lungs. The blood leaves the heart by the pulmonary artery and returns by the pulmonary veins. The air enters and leaves the lungs by the same system of tubes.
Fig. 39 Fig. 39—Diagram to show air and blood movements in a terminal air sac. While the air moves into and from the space within the sac, the blood circulates through the sac walls. Blood Supply to the Lungs.—To accomplish the purposes of respiration, not only the air, but the blood also, must be passed into and from the lungs. The chief[pg 084] The lungs also receive blood from two (in some individuals three) small arteries branching from the aorta, known as the bronchial arteries. These convey to the lungs blood that has already been supplied with oxygen, passing it into the capillaries in the walls of the bronchi, bronchial tubes, and large blood vessels, as well as the connective tissue between the lobes of the lungs. This blood leaves the lungs partly by the bronchial veins and partly by the pulmonary veins. No part of the body is so well supplied with blood as the lungs.
Fig. 40 Fig. 40—The pleurÆ. Diagram showing the general form of the pleural sacs as they surround the lungs and line the inner surfaces of the chest (other parts removed). A, A'. Places occupied by the lungs. B, B'. Slight space within the pleural sacs containing the pleural secretion, a, a'. Outer layer of pleura and lining of chest walls and upper surface of diaphragm. b, b'. Inner layer of pleura and outer lining of lungs. C. Space occupied by the heart. D. Diaphragm. The Pleura.—The pleura is a thin, smooth, elastic, and tough membrane which covers the outside of the lungs and lines the inside of the chest walls. The covering of each lung is continuous with the lining of the chest wall on its respective side and forms with it a closed sac by[pg 085] The Thorax.—The force required for breathing is supplied by the box-like portion of the body in which the lungs are placed. This is known as the thorax, or chest, and includes that part of the trunk between the neck and the abdomen. The space which it incloses, known as the thoracic cavity, is a variable space and the walls surrounding this space are air-tight. A framework for the thorax is supplied by the ribs which connect with the spinal column behind and with the sternum, or breast-bone, in front. They form joints with the spinal column, but connect with the sternum by strips of cartilage. The ribs do not encircle the cavity in a horizontal direction, but slope downward from the spinal column both toward the front and toward the sides, this being necessary to the service which they render in breathing. How Air is Brought into and Expelled from the Lungs.—The principle involved in breathing is that air flows from a place of greater to a place of less pressure. The construction of the thorax and the arrangement of the lungs within it provide for the application of this principle in a most practical manner. The lungs are suspended from the upper portion of the thoracic cavity, and the trachea and the upper air passages provide the only opening to the outside atmosphere. Air entering the thorax must on[pg 086]
Fig. 41 Fig. 41—Diagram illustrating the bellows principle in breathing. A. The human bellows. B. The hand bellows. Compare part for part. When the thorax is diminished in size, the air within the lungs is slightly compressed. This causes it to become denser and to exert on this account a pressure slightly greater than that of the atmosphere on the outside. The air now flows out until the equality of the pressure is again restored. Thus the thorax, by making the pressure within the lungs first slightly less and then slightly greater than the atmospheric pressure, causes the air to move into and out of the lungs. Breathing is well illustrated by means of the common hand bellows, its action being similar to that of the thorax. It will be observed that when the sides are spread apart air flows into the bellows. When they are pressed together the air flows out. If an air-tight sack were hung in the bellows with its mouth attached to the projecting tube, the arrangement would resemble closely the general plan of the breathing organs (Fig. 41). One respect, however, in which the bellows differs from the thorax should be noted. The thorax is never sufficiently compressed to drive out all the air. Air is always present in the lungs. This keeps them more or less distended and pressed against the thoracic walls. How the Thoracic Space is Varied.—One means of varying the size of the thoracic cavity is through the movements of the ribs and their resultant effect upon the walls[pg 087] 1. The scaleni muscles, three in number on each side, which connect at one end with the vertebrÆ of the neck and at the other with the first and second ribs. Their contraction slightly raises the upper portion of the thorax. 2. The elevators of the ribs, twelve in number on each side, which are so distributed that each single muscle is attached, at one end, to the back portion of a rib and, at the other, to a projection of the vertebra a few inches above. The effect of their contraction is to' elevate the middle portion of the ribs and to turn them outward or spread them apart. 3. The intercostal muscles, which form two thin layers between the ribs, known as the internal and the external intercostal muscles. The external intercostals are attached between the outer lower margin of the rib above and the outer upper margin of the rib below, and extend obliquely downward and forward. The internal intercostals are attached between the inner margins of adjacent ribs, and they extend obliquely downward and backward from the front. The contraction of the external intercostal muscles raises the ribs, and the contraction of the internal intercostals tends to lower them.
Fig. 42 Fig. 42—Simple apparatus for illustrating effect of movements of the ribs upon the thoracic space; strips of cardboard held together by pins, the front part being raised or lowered by threads moving through attachments at 1 and 2. As the front is raised the space between the uprights is increased. The front upright corresponds to the breastbone, the back one to the spinal column, the connecting strips to the ribs, and the threads to the intercostal muscles. By slightly raising and spreading apart the ribs the thoracic space is increased in two directions—from front to back and from side to side. Lowering and converging the ribs has, of course, the opposite effect (Fig. 42). Except in forced expirations the ribs are lowered and converged by their own weight and by the elastic reaction of the surrounding parts. [pg 088] The diaphragm, however, is not raised by the contraction of its own muscles, but is pushed up by the organs beneath. By the elastic reaction of the abdominal walls (after their having been pushed out by the lowering of the diaphragm), pressure is exerted on the organs of the abdomen and these in turn press against the diaphragm. This crowds it into the thoracic space. In forced expirations the muscles in the abdominal walls contract to push up the diaphragm. Interchange of Gases in the Lungs.—During each inspiration the air from the outside fills the entire system of bronchial tubes, but the alveoli are largely filled, at the same time, by the air which the last expiratory effort has left in the passages. By the action of currents and eddies and by the rapid diffusion of gas particles, the air from the outside mixes with that in the alveoli and comes in contact with the membranous walls. Here the oxygen, after being dissolved by the moisture in the membrane, diffuses into the blood. The carbon dioxide, on the other hand, being in excess in the blood, diffuses toward the air in the alveoli. The interchange of gases at the lungs, however, is not fully understood, and it is possible that other forces than osmosis play a part.
Fig. 43 Fig. 43—Diagram illustrating lung capacity. Capacity of the Lungs.—The air which passes into and from the lungs in ordinary breathing, called the tidal air, is but a small part of[pg 089]
Fig. 44 Fig. 44—Diagram illustrating internal respiration and its dependence on external respiration. (Modified from Hall.) (See text.) Internal, or Cell, Respiration.—The oxygen which enters the blood in the lungs leaves it in the tissues, passing through the lymph into the cells (Fig. 44). At the same time the carbon dioxide which is being formed at the cells passes into the blood. An exchange of gases is thus taking place between the cells and the blood, similar to[pg 090] HYGIENE OF RESPIRATORY ORGANSThe liability of the lungs to attacks from such dread diseases as consumption and pneumonia makes questions touching their hygiene of first importance. Consumption does not as a rule attack sound lung tissue, but usually has its beginning in some weak or enfeebled spot in the lungs which has lost its "power of resistance." Though consumption is not inherited, as some suppose, lung weaknesses may be transmitted from parents to children. This, together with the fact, now generally recognized, that consumption is contagious, accounts for the frequent appearance of this disease in the same family. Consumption as well as other respiratory affections can in the majority of cases be prevented, and in many cases cured, by an intelligent observation of well-known laws of health. Breathe through the Nostrils.—Pure air and plenty of it is the main condition in the hygiene of the lungs. One necessary provision for obtaining pure air is that of breathing through the nostrils. Air is the carrier of dust particles and not infrequently of disease germs.33 Partly through[pg 091]
Fig. 45 Fig. 45—Human air filter. Diagram of a section through the nostrils; shows projecting bones covered with moist membrane against which the air is made to strike by the narrow passages. 1. Air passages. 2. Cavities in the bones. 3. Front lower portion of the cranial cavity. In addition to removing dust particles and germs, other purposes are served by breathing through the nostrils. The warmth and moisture which the air receives in this way, prepare it for entering the lungs. Mouth breathing, on the other hand, looks bad and during sleep causes snoring. The habit of nose breathing should be established early in life.34 Cultivate Full Breathing.—Many people, while apparently taking in sufficient air to supply their need for oxygen, do not breathe deeply enough to "freely ventilate the lungs." "Shallow breathing," as this is called,[pg 092] Causes of Shallow Breathing.—Anything that impedes the free movement of air into the lungs tends to cause shallow breathing A drooping of the back or shoulders and a curved condition of the spinal column, such as is caused by an improper position in sitting, interfere with the free movements of the ribs and are recognized causes. Clothing also may impede the respiratory movements and lead to shallow breathing. If too tight around the chest, clothing interferes with the elevation of the ribs; and if too tight around the waist, it prevents the depression of the diaphragm. Other causes of shallow breathing are found in the absence of vigorous exercise, in the leading of an indoor and inactive life, in obstructions in the nostrils and upper pharynx, and in the lack of attention to proper methods of breathing. To prevent shallow breathing one should have the habit of sitting and standing erect. The clothing must not be allowed to interfere with the respiratory movements. The taking of exercise sufficiently vigorous to cause deep and[pg 093] Breathing Exercises.—In overcoming the habit of shallow breathing and in strengthening the lungs generally, the practicing of occasional deep breathing has been found most valuable and is widely recommended. With the hands on the hips, the shoulders drawn back and down, the chest pushed upward and forward, and the chin slightly depressed, draw the air slowly through the nostrils until the lungs are completely full. After holding this long enough to count three slowly, expel it quickly from the lungs. Avoid straining. To get the benefit of pure air, it is generally better to practice deep breathing out of doors or before an open window. By combining deep breathing with simple exercises of the arms, shoulders, and trunk much may be done towards straightening the spine, squaring the shoulders, and overcoming flatness of the chest. Though such movements are best carried on by the aid of a physical director, one can do much to help himself. One may safely proceed on the principle that slight deformities of the chest, spine, and shoulders are corrected by gaining and keeping the natural positions, and may employ any movements which will loosen up the parts and bring them where they naturally belong.36 [pg 094] Ventilation.—The process by which the air in a room is kept fresh and pure is known as ventilation. It is a[pg 095]
Fig. 46 Fig. 46—Window adjusted for ventilation without drafts. The method of ventilation must also be adapted to the construction of the building, the plan of heating, and the condition of the weather. Specific directions cannot be given, but the following suggestions will be found helpful in ventilating rooms where the air is not warmed before being admitted: 1. Introduce, the air through many small openings rather than a few large ones. If the windows are used for this purpose, raise the lower sash and drop the upper one slightly for several windows, varying the width to suit the conditions (Fig. 46). By this means sufficient air may be introduced without causing drafts. 2. Introduce the air at the warmest portions of the room.[pg 096] 3. If the wind is blowing, ventilate principally on the sheltered side of the house. Ample provision should be made for fresh air in sleeping rooms, and here again drafts must be avoided. Especially should the bed be so placed that strong air currents do not pass over the sleeper. In schoolhouses and halls for public gatherings the means for efficient ventilation should, if possible, be provided in the general plan of construction and method of heating.
Fig. 47 Fig. 47—Artificial respiration as a laboratory experiment. Expiration. Prone-posture method of Schaffer. Artificial Respiration.—When natural breathing is temporarily suspended, as in partial drowning, or when one has been overcome by breathing some poisonous gas, the saving of life often depends upon the prompt application of artificial respiration. This is accomplished by alternately compressing and enlarging the thorax by means of variable pressure on the outside, imitating the natural process as nearly as possible. Following is the method proposed by Professor E.A. Schaffer of England, and called by him "the prone-posture method of artificial respiration": [pg 097]
Fig. 48 Fig. 48—Artificial respiration. Inspiration. The special advantages of the prone-posture method over others that have been employed are: I. It may be applied by a single individual and fora long period of time without exhaustion. 2. It allows the mucus and water (in case of drowning) to run out of the mouth, and causes the tongue to fall forward so as not to obstruct the passageway. 3. It brings a sufficient amount of air into the lungs.40 [pg 098] Tobacco Smoke and the Air Passages.—Smoke consists of minute particles of unburnt carbon, or soot, such as collect in the chimneys of fireplaces and furnaces. If much smoke is taken into the lungs, it irritates the delicate linings and tends to clog them up. Tobacco smoke also contains the poison nicotine, which is absorbed into the blood. For these reasons the cigarette user who inhales the smoke does himself great harm, injuring his nervous system and laying the foundation for diseases of the air passages. The practice of smoking indoors is likewise objectionable, since every one in a room containing the smoke is compelled to breathe it. Alcohol and Diseases of the Lungs.—Pneumonia is a serious disease of the lungs caused by germs. The attacks occur as a result of exposure, especially when the body is in a weakened condition. A noted authority states that "alcoholism is perhaps the most potent predisposing cause" of pneumonia.41 A person addicted to the use of alcohol is also less likely to recover from the disease than one who has avoided its use, a result due in part to the weakening effect of alcohol upon the heart. The congestion of the lungs in pneumonia makes it very difficult for the heart to force the blood through them. The weakened heart of the drunkard gives way under the task. The statement sometimes made that alcohol is beneficial[pg 099] The Outdoor Cure for Lung Diseases—Among the many remedies proposed for consumption and kindred diseases, none have proved more beneficial, according to reports, than the so-called "outdoor" cure. The person having consumption is fed plentifully upon the most nourishing food, and is made to spend practically his entire time, including the sleeping hours, out of doors. Not only is this done during the pleasant months of summer, but also during the winter when the temperature is below freezing. Severe exposure is prevented by overhead protection at night and by sufficient clothing to keep the body warm. The abundant supply of pure, cold air toughens the lungs and invigorates the entire body, thereby enabling it to throw off the disease. The success attending this method of treating consumptives suggests the proper mode of strengthening lungs that are not diseased, but simply weak. The person having weak lungs should spend as much time as he conveniently can out of doors. He should provide the most ample ventilation at night and have a sleeping room to himself. He should practice deep breathing exercises and partake of a nourishing diet. While avoiding prolonged chilling and other conditions liable to induce colds, he should take advantage of every opportunity of exposing himself fully and freely to the outside atmosphere. Summary.—The purpose of respiration is to bring about an exchange of gases between the body and the atmosphere. The organs employed for this purpose, called the respiratory organs, are adapted to handling materials in the gaseous state, and are operated in accordance with principles governing the movements of the atmosphere. By alternately increasing and diminishing[pg 100]
Fig. 49 Fig. 49—Model for demonstrating the lungs. Exercises.—1. How does air entering the lungs differ in composition from air leaving the lungs? What purposes of respiration are indicated by these differences? 2. Name the divisions of the lungs. 3. Trace air from the outside atmosphere into the alveoli. Trace the blood from the right ventricle to the alveoli and back again to the left auricle. 4. How does the movement of air into and from the lungs differ from that of the blood through the lungs with respect to (a) the direction of the motion. (b) the causes of the motion, and (c) the tubes through which the motion takes place? 5. How are the air passages kept clean and open? 6. Describe the pleura. Into what divisions does it separate the thoracic cavity? 7. Describe and name uses of the diaphragm. 8. If 30 cubic inches of air are passed into the lungs at each inspiration and .05 of this is retained as oxygen, calculate the number of cubic feet of oxygen consumed each day, if the number of inspirations be 18 per minute. 9. Find the weight of a day's supply of oxygen, as found in the above problem, allowing 1.3 ounces as the weight of a cubic foot. 10. Make a study of the hygienic ventilation of the schoolroom. [pg 101] 12. How may a flat chest and round shoulders be a cause of consumption? How may these deformities be corrected? 13. Give general directions for applying artificial respiration. PRACTICAL WORKExamine a dissectible model of the chest and its contents (Fig. 49). Note the relative size of the two lungs and their position with reference to the heart and diaphragm. Compare the side to side and vertical diameters of the cavity. Trace the air tubes from the trachea to their smallest divisions. Observation of Lungs (Optional).—Secure from a butcher the lungs of a sheep, calf, or hog. The windpipe and heart should be left attached and the specimen kept in a moist condition until used. Demonstrate the trachea, bronchi, and the bronchial tubes, and the general arrangement of pulmonary arteries and veins. Examine the pleura and show lightness of lung tissue by floating a piece on water. To show the Changes that Air undergoes in the Lungs.—1. Fill a quart jar even full of water. Place a piece of cardboard over its mouth and invert, without spilling, in a pan of water. Inserting a tube under the jar, blow into it air that has been held as long as possible in the lungs. When filled with air, remove the jar from the pan, keeping the top well covered. Slipping the cover slightly to one side, insert a burning splinter and observe that the flame is extinguished. This proves the absence of sufficient oxygen to support combustion. Pour in a little limewater43 and shake to mix with the air. The change of the limewater to a milky white color proves the presence of carbon dioxide.
Fig. 50 Fig. 50—Apparatus for showing changes which air undergoes while in the lungs. 2. The effects illustrated in experiment 1 may be shown in a somewhat more striking manner as follows: Fill two bottles of the same[pg 102] 3. Blow the breath against a cold window pane. Note and account for the collection of moisture. 4. Note the temperature of the room as shown by a thermometer. Now breathe several times upon the bulb, noting the rise in the mercury. What does this experiment show the body to be losing through the breath? To show Changes in the Thoracic Cavity.—1. To a yard- or meter-stick, attach two vertical strips, each about eight inches long, as shown in Fig. 51. The piece at the end should be secured firmly in place by screws or nails. The other should be movable. With this contrivance measure the sideward and forward expansion of a boy's thorax. Take the diameter first during a complete inspiration and then during a complete expiration, reading the difference. Compare the forward with the sideward expansion.
Fig. 51 Fig. 51—Apparatus for measuring chest expansion. 2. With a tape-line take the circumference of the chest when all the air possible has been expelled from the lungs. Take it again when the lungs have been fully inflated. The difference is now read as the chest expansion.
Fig. 52 Fig. 52—Simple apparatus for illustrating the action of the diaphragm. To illustrate the Action of the Diaphragm.—Remove the bottom from a large bottle having a small neck. (Scratch a deep mark with a[pg 103] To estimate the Capacity of the Lungs.—Breathing as naturally as possible, expel the air into a spirometer (lung tester) during a period, say of ten respirations (Fig. 53). Note the total amount of air exhaled and the number of "breaths" and calculate the amount of air exhaled at each breath. This is called the tidal air.
Fig. 53 Fig. 53—Apparatus (spirometer) for measuring the capacity of the lungs. 2. After an ordinary inspiration empty the lungs as completely as possible into the spirometer, noting the quantity exhaled. This amount, less the tidal air, is known as the reserve air. The air which is now left in the lungs is called the residual air. On the theory that this is equal in amount to the reserve air, calculate the capacity of the lungs in an ordinary inspiration. 3. Now fill the lungs to the full expansion of the chest and empty them as completely as possible into the spirometer, noting the amount expelled. This, less the tidal air and the reserve air, is called the complemental air. Now calculate the total capacity of the lungs. |
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