A Treatise on Anatomy, Physiology, and Hygiene Part 32

[Ill.u.s.tration: Fig. 97. A side view of the chest and abdomen in respiration. 1, The cavity of the chest. 2, The cavity of the abdomen. 3, The line of direction for the diaphragm when relaxed in expiration. 4, The line of direction for the diaphragm when contracted in inspiration.

5, 6, The position of the front walls of the chest and abdomen in inspiration. 7, 8, The position of the front walls of the abdomen and chest in expiration.]

_Experiment._ Place the ear upon the chest of a person, and a murmuring sound will be heard, somewhat like the soft sighings of the wind through forest trees. This sound is caused by the air rushing in and out of the lungs, and is peculiarly distinct in the child.

Explain fig. 97. How may the murmur of respiration be heard?

483. It is not easy to decide how much air is taken into the lungs at each inspiration. The quant.i.ty, however, must vary in different individuals, from the difference in the condition and expansion of the lungs, together with the size of the chest. From numerous experiments, the quant.i.ty, at an ordinary inspiration, of a common-sized man, is fixed at forty cubic inches. It has been estimated that one hundred and seventy cubic inches can be thrown out of the lungs by a forcible expiration, and that there remain in the lungs two hundred and twenty cubic inches; so that these organs, in their quiescent state, may be considered as containing about three hundred and ninety cubic inches of air, or more than a gallon.

484. Respiration is more frequent in females and children than in adult men. In diseases, particularly those of the lungs, it is more increased in frequency than the action of the heart. In health, the smallest number of inspirations in a minute by an adult, is not less than fourteen, and they rarely exceed twenty-five. Eighteen may be considered an average number. The quant.i.ty of oxygen taken into the lungs at each inspiration is about eight cubic inches, one half of which disappears in every act of respiration.

_Observation._ Under different circ.u.mstances, however, the consumption of oxygen varies. It is greater when the temperature is low, than when it is high; and during digestion the consumption has been found one half greater than when the stomach was empty.

483. Can it be ascertained with accuracy how much air is taken into the lungs at each inspiration? Why not? What is the probable quant.i.ty that an ordinary sized man inspires? How much can be thrown out of the lungs at a forcible expiration, and how much remains in the lungs?

From these calculations, how much may they contain in their quiescent state? 484. In whom is respiration most frequent? How in disease? How in health? How many may be considered an average number? When is the consumption of oxygen the greatest?

485. Dr. Southwood Smith has lately performed a series of very interesting experiments, from which he deduces the following general results: "1st. The volume of air ordinarily present in the lungs is about twelve pints. 2d. The volume of air received by the lungs at an ordinary inspiration is one pint. 3d. The volume of air expelled from the lungs at an ordinary expiration, is a little less than one pint.

4th. Of the volume of air received by the lungs at one inspiration, only one fourth part is decomposed at one action of the heart. 5th.

The quant.i.ty of blood that flows to the lungs, to be acted upon by the air at one action of the heart, is two ounces, and this is acted on in less than one second of time. 6th. The quant.i.ty of blood in the whole body of the human adult, is twenty-five pounds avoirdupois, or twenty pints. 7th. In the mutual action that takes place between the air and blood, every twenty-four hours, the air loses thirty-seven ounces of oxygen, and the blood fourteen ounces of carbon."

486. Apparently, atmospheric air is a simple element. But chemical a.n.a.lysis shows its composition to be oxygen and nitrogen, in the proportion of twenty-one parts of the former, and about seventy-nine of the latter. In addition, there is a small amount of vapor of water and carbonic acid. The pressure of this invisible, elastic fluid upon the body of an ordinary sized adult, is estimated to equal thirty-five thousand pounds.

487. The princ.i.p.al substance of a vitiated character in the dark-colored blood is carbonic acid. And since there is no chemical affinity between the oxygen and nitrogen of the air, the former readily unites with some of the elements of the blood. Hence, whenever blood is presented to the air in the lungs, the oxygen leaves the nitrogen, and becomes mixed with the circulating fluid. (Appendix J.)

485. State the 1st, 2d, 3d, and 4th deductions from the experiments of Dr. Southwood Smith. The 5th, 6th, and 7th. 486. Of what is atmospheric air composed? What is the weight of air upon a common sized man? 487. What is the princ.i.p.al substance of a vitiated character in the dark-colored blood? What is said of the chemical affinity between oxygen and nitrogen?

488. Again, carbonic acid and water have a stronger affinity for atmospheric air than for the other elements of the blood. Consequently, when they are brought into contact with the air in the lungs, the carbonic acid and water leave the other const.i.tuents of the blood, and unite with the air. In this way the bluish, or impure blood is relieved of its impurities, and becomes the red, or pure blood, which contains the principles so essential to life. (Appendix K.)

489. The formation of carbonic acid and water, eliminated from the system through the lungs and skin, is explained by the following theory: In the lungs and upon the skin the oxygen separates from the nitrogen and unites with the blood in the capillary vessels of these organs. The oxygen is conveyed with the blood to the capillary arteries and veins of the different tissues of the system. In these membranes there is a chemical union of the oxygen with the carbon and hydrogen contained in the blood and waste atoms of the system. This combustion, or union of oxygen with carbon and hydrogen, is attended with the disengagement of heat, and the formation of carbonic acid and water. (Appendix L.)

490. The following experiment will ill.u.s.trate the pa.s.sage of fluids through membranes, and the different affinity of gases for each other.

Put a mixture of water and alcohol into a phial and leave it uncorked.

Both the water and alcohol have a greater affinity for air than for each other. Alcohol has a greater affinity for the air, and will be diffused through it more readily than the water, when there is no intervening obstacle. But tie a piece of bladder over the mouth of the phial, and let it stand a few days,--the water will leave the alcohol, and pa.s.s through the membrane. By the aid of this experiment, we shall endeavor to explain the interchange of fluids in the lungs.

488. What is formed when oxygen unites with carbon or hydrogen? 489.

Give the theory for the formation of carbonic acid and watery vapor thrown out of the system. 490. Ill.u.s.trate the pa.s.sage of fluids through membranes, and the different affinities of gases.

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

[Ill.u.s.tration: Fig. 98. 1, A bronchial tube divided into three branches.

2, 2, 2, Air-cells. 3, Branches of the pulmonary artery, that spread over the air-cells. Through the pulmonary artery the dark, impure blood is carried to the air-cells of the lungs. 4, Branches of the pulmonary vein, that commence at the minute terminations of the pulmonary artery. Through the pulmonary vein the red blood is returned to the heart.]

492. As the impure blood is pa.s.sing in the minute vessels over the air-cells, the oxygen pa.s.ses through the thin coats of the air-cells and blood-vessels, and unites with the blood. At the same time, the carbonic acid and water leave the blood, and pa.s.s through the coats of the blood-vessels and air-cells, and mix with the air in the cells.

These are thrown out of the system every time we breathe. This interchange of products produces the change in the color of the blood.

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

_Experiment._ Fill a bladder with dark blood drawn from any animal.

Tie the bladder closely, and suspend it in the air. In a few hours, the blood next to the membrane will have become of a bright red color.

This is owing to the oxygen from the air pa.s.sing through the bladder, and uniting with the blood, while the carbonic acid has escaped through the membrane.

[Ill.u.s.tration: Fig. 99. An ideal view of the pulmonary circulation. 1, 1, The right lung. 2, 2, The left lung. 3, The trachea. 4, The right bronchial tube. 5, The left bronchial tube. 6, 6, 6, 6, Air-cells. 7, The right auricle. 8, The right ventricle. 9, The tricuspid valves. 10, The pulmonary artery. 11, The branch to the right lung. 12, The branch to the left lung. 13, The right pulmonary vein. 14, The left pulmonary vein. 15, The left auricle. 16, The left ventricle. 17, The mitral valves.]

493. The presence of carbonic acid and watery vapor in the expired air, can be proved by the following experiments: 1st. Breathe into lime-water, and in a few minutes it will become of a milk-white color.

This is owing to the carbonic acid of the breath uniting with the lime, forming the _carbonate of lime_. 2d. Breathe upon a cold, dry mirror for a few minutes, and it will be covered with moisture. This is condensed vapor from the lungs. In warm weather, this watery vapor is invisible in the expired air, but in a cold, dry morning in winter, the successive jets of vapor issuing from the mouth and nose are sufficiently obvious.

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

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

_Ill.u.s.tration._ When spirituous liquors are taken into the stomach, they are absorbed by the veins and mixed with the dark-colored blood, in which they are carried to the lungs to be expelled from the body.

This will explain the fact, which is familiar to most persons, that the odor of different substances is perceptible in the breath, or expired air, long after the mouth is free from these substances.

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

Give the ill.u.s.tration.

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

CHAPTER XXV.