Hygienic Physiology : with Special Reference to the Use of Alcoholic Drinks and Narcotics

Chapter VI: Hygiene (2)

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WONDERS OF RESPIRATION.--The perfection of the organs of respiration challenges our admiration. So delicate are they that the least pressure would cause exquisite pain, yet tons of air surge to and fro through their intricate passages, and bathe their innermost cells. We yearly perform at least seven million acts of breathing, inhaling one hundred thousand cubic feet of air, and purifying over three thousand five hundred tons of blood. This gigantic process goes on constantly, never wearies or worries us, and we wonder at it only when science reveals to us its magnitude. In addition, by a wise economy, the process of respiration is made to subserve a second use no less important, and the air we exhale, passing through the organs of voice, is transformed into prayers of faith, songs of hope, and words of social cheer.

FIG. 33.

DISEASES, ETC.--1. _Constriction of the Lungs_ is produced by tight clothing. The ribs are thus forced inward, the size of the chest is diminished, and the amount of inhaled air decreased. Stiff clothing, and especially a garment that will not admit of a full breath without inconvenience, will prevent that free movement of the ribs so essential to health. Any infraction of the laws of respiration, even though it be fashionable, will result in diminished vitality and vigor, and will be fearfully punished by sickness and weakness through the whole life.

2. _Bronchitis_ (bron-ki'-tis) is an inflammation (see Inflammation) of the mucous membrane of the bronchial tubes. It is accompanied by an increased secretion of mucus, and consequent coughing.

3. _Pleurisy_ is an inflammation of the pleura. It is sometimes caused by an injury to the ribs, and results in a secretion of water within the membrane.

4. _Pneumonia_ (_pneuma_, breath) is an inflammation of the lungs, affecting chiefly the air cells.

5. _Consumption_ is a disease which destroys the substance of the lungs. Like other lung difficulties, it is caused largely by a want of pure air, a liberal supply of which is the best treatment that can be prescribed for it. [Footnote: If I were seriously ill of consumption, I would live outdoors day and night, except in rainy weather or midwinter; then I would sleep in an unplastered log house. Physic has no nutriment, gaspings for air can not cure you, monkey capers in a gymnasium can not cure you, stimulants can not cure you. What consumptives want is pure air, not physic, plenty of meat and plenty of bread.--DR. MARSHALL HALL.]

6. _Asphyxia_ (as-fix'-i-a).--When a person is drowned, strangled, or choked in any way, what is called asphyxia occurs. The face turns black; the veins become turgid; insensibility and often convulsions ensue. If relief is not secured within a few minutes, death will be inevitable. [Footnote: The lack of oxygen, and the presence of carbonic-acid gas, are the combined causes. Oxygen starvation and carbonic-acid poisoning, each fatal in itself, work together to destroy life.] (See p. 264.)

7. _Diphtheria_ (_diphthera_, a membrane) is characterized by fever, debility, and a peculiar sore throat, in which exuding fibrinous matter forms a grayish white membrane, which afterward decomposes with a fetid odor. Its sudden and insidious approach, contagious character, and frequent fatality, render it an exceedingly dreaded disease. A diphtheritic patient should be quarantined, and everything connected with the sick room thoroughly disinfected.

8. _Croup_, which often attacks young children, is an inflammation of the mucous membrane of the larynx and trachea. It is commonly preceded by a cold. The child sneezes, coughs, and is hoarse, but the attack frequently comes on suddenly, and usually in the night. It is accompanied by a peculiar "brassy," ringing cough, which, once heard, can never be mistaken. It may prove fatal within a few hours. (See p. 260.)

9. _Stammering_ depends, not on defects of the muscles, but on a want of due control of the mind. When a stammerer is not too conscious of his lack, and tries to form his words slowly, he speaks plainly, and may sing well, for then his words must follow one another in rhythmic time. Many persons who stammer in common conversation can talk with fluency when making a speech. The stammerer should seek to discover the cause of his difficulty, and to overcome it by vocal and respiratory exercise, especially by speaking only after a full inspiration, and during a long, slow expiration.

PRACTICAL QUESTIONS.

1. What is the philosophy of "the change of voice" in a boy?

2. Why can we see our breath on a frosty morning?

3. When a law of health and a law of fashion conflict, which should we obey?

4. If we use a "bunk" bed, should we pack away the clothes when we first rise in the morning?

5. Why should a clothespress be well ventilated?

6. Should the weight of our clothing hang from the waist, or the shoulder?

7. Describe the effects of living in an overheated room.

8. What habits impair the power of the lungs?

9. For full, easy breathing in singing, should we use the diaphragm and lower ribs, or the upper ribs alone?

10. Why is it better to breathe through the nose than the mouth?

11. Why should not a speaker talk while returning home on a cold night after a lecture?

12. What part of the body needs the loosest clothing?

13. What part needs the warmest?

14. Why is a "spare bed" generally unhealthful?

15. Is there any good in sighing?

16. Should a hat be thoroughly ventilated? How?

17. Why do the lungs of people who live in cities become of a gray color?

18. How would you convince a person that a bedroom should be aired? [Footnote: "If the condensed breath collected on the cool windowpanes of a room where a number of persons have been assembled, be burned, a smell as of singed hair will show the presence of organic matter; and if the condensed breath be allowed to remain on the windows for a few days, it will be found, on examination by the microscope, that it is alive with animalculæ."]

19. What persons are most liable to catarrhs, consumption, etc.?

20. If a person is plunged under water, will it enter his lungs?

21. Are bed curtains healthful?

22. Why do some people take "short breaths" after a meal?

23 What is the special value of public parks?

24. Can a person become used to bad air, so that it will not injure him?

25. Why do we gape when we are sleepy?

26. Is a fashionable waist a model of art in sculpture or painting?

27. Should a fireplace be closed? [Footnote: Thousands of lives would be saved if all fireplaces were kept open. If you are so fortunate as to have a fireplace in your room, paint it when not in use, put a bouquet of fresh flowers in it every morning, if you please, or do anything to make it attractive, but never _close it_; better use the fireboards for kindling wood. It would be scarcely more absurd to take a piece of elegantly-tinted court-plaster and stop up the nose, trusting to the accidental opening and shutting of the mouth for fresh air, because you thought it spoiled the looks of your face to have two such great, ugly holes in it, than to stop your fireplace with elegantly-tinted paper, or a Japanese fan, because it looks better.--Leeds.]

28. Why does embarrassment or fright cause a stammerer to stutter still more painfully?

29. In the organs of voice, what parts have somewhat the same effect as the case of a violin and the sounding-board of a piano?

30. Why should we be careful not to "take the breath of a sick person"?

31. What special care should be taken with regard to keeping a cellar clean?

32. How is the air strained as it passes into the lungs?

33. Can one really "draw the air into his lungs"?

34. How often do we breathe?

35. Describe some approved method of ventilation.

36. What is at once the floor of the chest and the roof of the abdomen?

37. What would you do in a case of apparent death by drowning, or by coal gas? (See p. 264.)

38. What would you do in a case of croup, while the doctor was coming? (See p. 260.)

39. How would you treat a severe burn? (See p. 257.)

40. Describe the various ways in which the water in a well is liable to become unwholesome.

FIG. 34.

THE CIRCULATION.

"No rest this throbbing slave may ask, Forever quivering o'er his task, While far and wide a crimson jet Leaps forth to fill the woven net, Which in unnumber'd crossing tides The flood of burning life divides, Then, kindling each decaying part, Creeps back to find the throbbing heart."

HOLMES.

ANALYSIS OF THE CIRCULATION

THE CIRCULATION.

THE ORGANS OF THE CIRCULATION are the _heart_, the _arteries_, the _veins_, and the _capillaries_.

FIG. 35.

THE BLOOD is the liquid by means of which the circulation is effected. It permeates every part of the body, except the cuticle, nails, hair, etc. The average quantity in each person is about eighteen pounds. [Footnote: It is difficult to estimate the exact amount, and therefore authorities disagree. Foster places it at about one thirteenth of the body weight.] It is composed of a thin, colorless liquid, the _plasma_, filled with red disks or cells, [Footnote: There is also one white globular cell to every three or four hundred red ones. The blood is no more red than the water of a stream would be if you were to fill it with little red fishes. Suppose the fishes to be very, very small--as small as a grain of sand-- and closely crowded together through the whole depth of the stream; the water would look quite red, would it not? And this is the way in which, blood looks red--only observe one thing; a grain of sand is a mountain in comparison with the little red fishes in the blood. If I were to tell you they measured about 1/3500 of an inch in diameter, you would not be much wiser; so I prefer saying (by way of giving you a more perfect idea of their minuteness) that there would be about a million in such a drop of blood as would hang on the point of a needle. I say so on the authority of a scientific microscopist--M. Bouillet. Not that he has ever counted them, as you may suppose, any more than I have done; but this is as near an approach as can be made by calculation to the size of 1/3500 part of an inch in diameter.--JEAN MACE.] so small that about three thousand five hundred placed side by side would measure only an inch, and it would take sixteen thousand laid flatwise upon one another to make a column of that height. Under the microscope, they are found to be rounded at the edge and concave on both sides. [Footnote: By pricking the end of the finger with a needle, we can obtain a drop for examination. Place it on the slide, cover with a glass, and put it at once under the microscope. The red disks will be seen to group themselves in rows, while the white disks will seem to draw apart, and to be constantly changing their form. After a gradual evaporation, the crystals (Fig. 36) may be seen. In animals, they have various, though distinctive forms.] They have a tendency to collect in piles like rolls of coin. The size and shape vary in the blood of different animals. [Footnote: Authorities differ greatly in their estimate of the size of the disks (corpuscles) in human blood. The fact is that the size varies in different persons, probably also in the same individual. Many of the best microscopists therefore hesitate to state whether a particular specimen of blood belonged to a human being or to an animal. Others claim that they can distinguish with accuracy. Evidently, the question is one of great uncertainty. The following statement of the size of the cells in different animals is taken from Gulliver's tables: Cat, 1/4404 of an inch in diameter; whale, 1/3100; mouse, 1/3614; hog, 1/4230; camel, 1/3123; sheep, 1/3352; horse, 1/4800; Virginia deer, 1/5038; dog- faced baboon, 1/4861; brown baboon, 1/3493; red monkey, 1/3396; black monkey, 1/3530.] Disks are continually forming in the blood, and are constantly dying--twenty million at every breath.--DRAPER.

The plasma also contains fibrin, [Footnote: it is usual to say that fibrin is contained in the blood. It probably does not exist as such, but there are present in the blood certain substances known as _paraglobulin_ and _fibrinogen_, which by the action of a third substance, _fibrin ferment_ under certain circumstances, form fibrin and so cause coagulation. The exact nature of the process by which fibrin is produced by these three factors is not understood--See Foster's _Text Book of Physiology_, p 22.] albumin--which is found nearly pure in the white of an egg--and various mineral substances, as iron, [Footnote: Enough iron has been found in the ashes of a burned body to form a mourning ring.] lime, magnesia, phosphorus, potash, etc.

FIG. 36.

USES OF THE BLOOD.--The blood has been called "liquid flesh"; but it is more than that, since it contains the materials for making every organ. The plasma is rich in mineral matter for the bones, and in albumen for the muscles. The red disks are the air cells of the blood. They contain the oxygen so essential to every operation of life. Wherever there is work to be done or repairs to be made, there the oxygen is needed. It stimulates to action, and tears down all that is worn out. In this process, it combines with and actually burns out parts of the muscles and other tissues, as wood is burned in the stove. [Footnote: For the sake of simplicity, perhaps to conceal our own ignorance, we call this process "burning." The simile of a fire is good so far as it goes. But as to the real nature of the change which the physiologist briefly terms "oxidation," we know nothing. This much only can be asserted positively. A stream of oxygen is carried by the blood to the muscles (in fact to every tissue in the body), while, from the muscles the blood carries away a stream of carbonic acid and water. But what takes place in the muscles, when and what chemical change occurs, no one can tell. We see the first and the last stage. We know that contraction of the muscles somehow comes about, oxygen disappears, carbonic acid appears, energy is released, and force is exhibited as motion, heat, and electricity. But the intermediate step is hidden.

There are certain theories advanced, however, that are worth considering. Some physiologists hold that the muscle has the power of taking up the oxygen from the _hemoglobin_ (a body that comprises ninety per cent of the red corpuscles when dried, and is the oxygen carrier of the blood), and fixing it, as well as the raw material (food) furnished by the blood, thus forming a true contractile substance. The breaking down or decomposition of this contractile substance in the muscle, sets free its potential energy. The process is gentle so long as the muscle is at rest, but becomes excessive and violent when contraction occurs. (See "Foster's Physiology," p. 118.) It is also believed by some that the chemical change in the muscle partakes of a fermentive character; that, under the influence of the proper ferments, the substances break up into other and simpler products, thus setting free heat and force; and that this chemical change is followed by a secondary oxidation by the oxygen in the arterial blood, thereby forming carbonic acid and water, as in all putrefactive processes. But these and other views are not as yet fully understood; while they utterly fail to tell us how a collection of simple cells, filled merely with a semifluid mass of matter, can contract and set free muscular power. The commonness of this act hides from us its wonderful nature. But here, hidden in the cell--Nature's tiny laboratory--lies the mystery of life. Before its closed door we ponder in vain, confessing the unskillfulness of our labor, and fearing all the while lest the _Secret of the Cell_ will always elude our search.] The blood, now foul with the burned matter, the refuse of this fire, is caught up by the circulation, and whirled back to the lungs, where it is purified, and again sent bounding on its way.

There are then two different kinds of the blood in the body: the red or arterial, and the dark or venous.

TRANSFUSION.--As the blood is really the "vital fluid" it would seem that feeble persons might be restored to vigor by infusing healthy blood into their veins. This hypothesis, so valuable in its possible results in prolonging human life, has been carefully tested. Animals which have ceased to breathe have thus had their vitality recalled. In the seventeenth century the theory became a subject of special investigation. A maniac was restored to reason by the blood of a calf, and the most extravagant hopes were entertained. But many fatal accidents occurring, experiments upon human beings were forbidden by law, and transfusion soon fell into disuse. It has, however, been successfully practiced in several cases within the last few years, and is a method still in repute for saving lives.

COAGULATION.--When blood is exposed to the air, it coagulates. This is caused by the solidifying of the fibrin, which entangling the disks, forms the "clot." The remaining clear, yellow liquid is the _serum_. The value of this peculiar property of the blood can hardly be overestimated. The coagulation soon checks all ordinary cases of bleeding. [Footnote: In the case of the lower animals, which have no means of stopping hemorrhages as we have, the coagulation is generally still more rapid. In some species of birds it takes place almost instantaneously.] When a wound is made, and bleeding commences, the fibrin forms a temporary plug, as it were, which is absorbed when the healing process is finished. Thus we see how a Divine foresight has provided not only for the ordinary wants of the body, but also for the accidents to which it is liable. [Footnote: The fibrin is not an essential ingredient of the blood. All the functions of life are regularly performed in people whose blood lacks fibrin; and, in cases of transfusion, where blood deprived of its fibrin was used, the vivifying influence seemed to be the same. Its office, therefore, must mainly be to stanch any hemorrhage which may occur.--FLINT.]

FIG. 37.

THE HEART is the engine which propels the blood. It is a hollow, pear- shaped muscle, about the size of the fist. It hangs, point downward, just to the left of the center of the chest. (See Fig. 31.) It is inclosed in a loose sac of serous membrane, [Footnote: The mucous membrane lines the open cavities of the body; the serous, the closed. The pericardium is a sac composed of two layers--a fibrous membrane on the outside, and a serous one on the inside. The latter covers the external surface of the heart, and is reflected back upon itself in order to form, like all the membranes of this nature, a sac without an opening. The heart is thus covered by the pericardial sac, but not contained inside its cavity. A correct idea may be formed of the disposition of the pericardium around the heart by recalling a very common and very convenient, though now discarded headdress, the cotton nightcap. The pericardium incloses the heart exactly as this cap covered the heads of our forefathers.-- _Wonders of the Human Body_.] called the pericardium (_peri_, about; and _kardia_, the heart). This secretes a lubricating fluid, and is smooth as satin.

THE MOVEMENTS OF THE HEART consist of an alternate contraction and expansion. The former is called the _sys'-to-le_, and the latter the _di-as'-to-le_. During the diastole, the blood flows into the heart, to be expelled by the systole. The alternation of these movements constitutes the beating of the heart which we hear so distinctly between the fifth and sixth ribs. [Footnote: Two sounds are heard if we put our ear over the heart,--the first and longer as the blood is leading the organ, the second as it falls into the pockets of the two arteries, and the valves then striking together cause it. The first sound is mainly the noise made by the muscular tissue. During the first, the two ventricles contract; during the second the two auricles do so. The hand may feel the heart striking the ribs as it contracts,--a feeling called the impulse, or, if quicker and stronger than usual, palpitation. This is not always a sign of disease, but in hypochondriacs is often an effect of the mind on the nerves of the heart.--MAPOTHER]

FIG. 38.

THE AURICLES AND VENTRICLES--The heart is divided into four chambers. In an adult, each holds about a wineglassful. The upper ones, from appendages on the outside resembling the ears of a dog, are called _auricles (aures_, ears). are termed _ventricles_. The auricle and ventricle on each side communicate with each other, but the right and left halves of the heart are entirely distinct, and perform different offices. The left side propels the red blood; and the right, the dark. The auricles are merely reservoirs to receive the blood (the left auricle, as it filters in bright and pure from the lungs; the right, as it returns dark and foul from the tour of the body), and to furnish it to the ventricles as they need. Their work being so light, their walls are comparatively thin and weak. On the other hand, the ventricles force the blood (the left, to all parts of the body; the right, to the lungs), and are, therefore, made very strong. As the left ventricle drives the blood so much farther than the right, it is correspondingly thicker and stronger.

NEED OF VALVES IN THE HEART.--As the auricles do not need to contract with much force simply to empty their contents into the ventricles below them, there is no demand for any special contrivance to prevent the blood from setting back the wrong way. Indeed, it would naturally run down into the ventricle, which is at that moment open to receive it. But, when the strong ventricles contract, especially the left one, which must drive the blood to the extremities, some arrangement is necessary to prevent it from returning into the auricle. Besides, when they expand, the "suction power" would tend to draw back again from the arteries all the blood just forced out. This difficulty is obviated by means of little doors, or valves, which will not let it go the wrong way. [Footnote: The heart of an ox or a sheep may be used to show the chambers and valves. The aorta should be cut as far as possible from the heart, and then by pumping in water the perfection of these valves will be finely exhibited. Cutting the heart across near the middle will show the greater thickness of the left ventricle.]

THE TRICUSPID AND BICUSPID VALVES.--At the opening into the right ventricle, is a valve consisting of three folds or flaps of membrane, whence it is called the _tricuspid_ valve (_tri_, three; and _cuspides_, points), and in the left ventricle, one containing two flaps, and named the _bicuspid_ valve. These hang so loosely as to oppose no resistance to the passage of the blood into the ventricles; but, if any attempts to go the other way, it gets between the flaps and the walls of the heart, and, driving them outward, closes the orifice.

FIG. 39.

THESE FLAPS ARE STRENGTHENED like sails by slender cords, which prevent their being pressed back through the opening. If the cords were attached directly to the walls of the heart, they would be loosened in the systole, and so become useless when most needed. They are, therefore, fastened to little muscular pillars projecting from the sides of the ventricle; when that contracts, the pillars contract also, and thus the cords are held tight.

THE SEMILUNAR VALVES.--In the passages outward from the ventricles, are valves, called from their peculiar half-moon shape _semilunar_ valves (_semi_, half; _Luna_, Moon). Each consists of three little pocket-shaped folds of membrane, with their openings in the direction which the blood is to take. When it sets back, they fill, and, swelling out, close the passage (Fig. 40).

THE ARTERIES [Footnote: _Aer,_ air; and _tereo,_ I contain--so named because after death they contain air only, and hence the ancients supposed them to be air tubes leading through the body.] are the tube-like canals which convey the blood _from_ the heart. They carry the red blood (see note, p. 119). They are composed of an elastic tissue, which yields at every throb of the heart, and then slowly contracting again, keeps up the motion of the blood until the next systole. The elasticity of the arteries acts like the air chamber of a fire engine, which converts the intermittent jerks of the brakes or pump into the steady stream of the hose nozzle.

The arteries sometimes communicate by means of branches or by meshes of loops, so that if the blood be blocked in one, it can pass round through another, and so get by the obstacle. [Footnote: This occurs especially about the joints, where it serves to maintain the circulation during the bending of a limb, or when the main artery is obstructed by disease or injury, or has been tied by the surgeon. In the last case, the small adjacent arteries gradually enlarge, and form what is called a collateral circulation.] When an artery penetrates a muscle, it is often protected by a sheath or by fibrous rings, which prevent its being pulled out of place or compressed by the play of the muscles.

The arteries are generally located as far as possible beneath the surface, out of harm's way, and hence are found closely hugging the bones or creeping through safe passages provided for them. They are generally nearly straight, and take the shortest routes to the parts which they are to supply with blood.

THE ARTERIAL SYSTEM starts from the left ventricle by a single trunk--the _aorta_--which, after giving off branches to the head, sweeps back of the chest with a bold curve--the _arch of the aorta_ (_c_, Fig. 34)--and thence runs downward (_f_), dividing and subdividing, like a tree, into numberless branches, which, at last, penetrate every nook and corner of the body.

THE PULSE.--At the wrist (_k_, radial artery) and on the temple (temporal artery) we can feel the expansion of the artery by each little wave of blood set in motion by the contraction of the heart. In health, there are about seventy-two [Footnote: This number varies much with age, sex, and individuals. Napoleon's pulse is said to have been only forty, while it is not infrequent to find a healthy pulse at one hundred or over. In general, the pulse is quicker in children and in old people than in the middle-aged; in short persons than in tall; in women than in men. Shame makes the heart send more blood to the blushing cheek, and fear almost stops it. The will can not check the heart. There is said, however, to have been a notable exception to this in the case of one Colonel Townsend, of Dublin, who, after having succeeded several times in stopping the pulsation, at last lost his life in the act.] pulsations per minute. They increase with excitement or inflammation, weaken with loss of vigor, and are modified by nearly every disease. The physician, therefore, finds the pulse a good index of the state of the system and the character of the disorder. (See p. 314.)

THE VEINS are the tube-like canals which convey the blood _to_ the heart. [Footnote: There is one exception to the general course of the veins. The _portal_ vein carries the blood from the digestive organs to the liver, where it is acted upon, thence poured into the ascending vena cava, and goes back to the heart.] They carry the dark or venous blood (note, p. 119). As they do not receive the direct impulse of the heart, their walls are made much thinner and less elastic than those of the arteries. At first small, they increase in size and diminish in number as they gradually pour into one another, like tiny rills collecting to form two rivers, the vena cava ascending and the vena cava descending (_l, m_, Fig. 34), which empty into the right auricle.

Some of the veins creep along under the skin, where they can be seen, as in the back of the hand; while others accompany the arteries, some of which have two or more of these companions.

VALVES similar in construction to those already described (the semilunar valves of the heart, page 114) are placed at convenient intervals, in order to guide the blood in its course, and prevent its setting backward. [Footnote: Too much standing, or tight elastics, often cause the veins in the leg to swell, so that the valves can not work; the veins then become _varicose_, or permanently enlarged, and, if they burst, the bleeding may be profuse and even dangerous. Raising the leg and pressing the finger on the bleeding spot will stay it. Walking does not encourage this disease, for the active muscles force on the venous blood. Clerks who are subject to varicose veins should have seats behind the counters where they may rest when not actually employed. A deep breath helps the flow in the veins, and a wound may suck in air with fatal effect. A maimed horse is most mercifully killed by blowing a bubble of air into the veins of his neck. As the deep-sea pressure would burst valves, the whale has none; hence a small wound by the harpoon causes him to bleed to death.-- MAPOTHER.] We can easily examine the working of these valves. On baring the arm, blue veins may be seen running along the arm toward the hand. Their diameter is tolerably even, and they gradually decrease in size. If now the finger be pressed on the upper part of one of these veins, and then passed downward so as to drive its blood backward, swellings like little knots will make their appearance. Each of these marks the location of a valve, which is closed by the blood we push before our finger. Remove the pressure, and the valve will swing open, the blood set forward, and the vein collapse to its former size.

FIG. 40.

THE CAPILLARIES (_capillus,_ a hair) form a fine network of tubes, connecting the ends of the arteries with the veins. They blend, however, with the extremities of these two systems, so that it is not easy to tell just where an artery ends and a vein begins. So closely are they placed, that we can not prick the flesh with a needle without injuring, perhaps, hundreds of them. The air cells of the blood deposit there their oxygen, and receive carbonic acid, while in the delicate capillaries of the lungs [Footnote: The capillary tubes are there so fine that the disks of the blood have to go one by one, and are sadly squeezed at that. However, their elasticity enables them to resume their old shape as soon as they have escaped from this labyrinth.] they give up their load of carbonic acid in exchange for oxygen.

FIG. 41.

If, by means of a microscope, we examine the transparent web of a frog's foot, we can trace the route of the blood. [Footnote: With small splints and twine, a frog's foot can be easily stretched and tied so that the transparent web can be placed on the table of the microscope.] It is an experiment of wonderful interest. The crimson stream, propelled by the heart, rushes through the arteries, until it reaches the intricate meshes of the capillaries. Here it breaks into a thousand tiny rills. We can see the disks winding in single file through the devious passages, darting hither and thither, now pausing, swaying to and fro with an uncertain motion, and anon dashing ahead, until, at last, gathered in the veins, the blood sets steadily back on its return to the heart.

THE CIRCULATION [Footnote: The circulation of the blood was discovered by Harvey in 1619. For several years, he did not dare to publish his belief. When it became known, he was bitterly persecuted, and his practice as a physician greatly decreased in consequence. He lived, however, to see his theory universally adopted, and his name honored. Harvey is said to have declared that no man over forty years of age accepted his views.] consists of two parts--the _lesser_, and the _greater_.

FIG. 42.

1. _The Lesser Circulation_.--The dark blood from the veins collects in the right auricle, and, going through the tricuspid valve, empties into the right ventricle. Thence it is driven past the semilunar valves, through the pulmonary artery, to the lungs. After circulating through the fine capillaries of the air cells contained in the lungs, it is returned, bright and red, through the four pulmonary veins, [Footnote: It is noticeable that the pulmonary set of veins circulates red blood, and the pulmonary set of arteries circulates dark blood. Both are connected with the lungs.] to the left auricle.

2. _The Greater Circulation_.--From the left auricle, the blood is forced past the bicuspid valve to the left ventricle; thence it is driven through the semilunar valves into the great aorta, the main trunk of the arterial system. Passing through the arteries, capillaries, and veins, it returns through the venæ cavæ, ascending and descending, gathers again in the right auricle, and so completes the "grand round" of the body. Both these circulations are going on constantly, as the two auricles contract, and the two ventricles expand simultaneously, and _vice versa_.

THE VELOCITY OF THE BLOOD varies so much in different parts of the body, and is influenced by so many circumstances, that it can not be calculated with any degree of accuracy. It has been estimated that a portion of the blood will make the tour of the body in about twenty-three seconds (FLINT), and that the entire mass passes through the heart in from one to two minutes. [Footnote: The total amount of blood in an adult of average weight is about eighteen pounds. Dividing this by five ounces, the quantity discharged by the left ventricle at each systole, gives fifty- eight pulsations as the number necessary to transmit all the blood in the body. This, however, is an extremely unreliable basis of calculation, as the rapidity of the blood is itself so variable. Chauvreau has shown by experiments with his instrument that, corresponding to the first dilation of the vessels, the blood moves with immense rapidity; following this, the current suddenly becomes nearly arrested; this is succeeded by a second acceleration in the current, not quite so rapid as the first; and after this there is a gradual decline in the rapidity to the time of the next pulsation.] (See p. 314.)

DISTRIBUTION AND REGULATION OF THE HEAT OF THE BODY.--1. _Distribution_.--The natural temperature is not far from 98°. [Footnote: The average temperature is, however, easily departed from. Through some trivial cause the cooling agencies may be interfered with, and then, the heating processes getting the superiority, a high temperature or fever comes on. Or the reverse may ensue. In Asiatic cholera, the constitution of the blood is so changed that its disks can no longer carry oxygen into the system, the heat-making processes are put a stop to, and, the temperature declining, the body becomes of a marble coldness, characteristic of that terrible disease.--DRAPER.] This is maintained, as we have already seen, by the action of the oxygen within us. Each capillary tube is a tiny stove, where oxygen is combining with the tissues of the body (see note, p. 107). Every contraction of a muscle develops heat, the latent heat being set free by the breaking up of the tissue. The warmth so produced is distributed by the circulation of the blood. Thus the arteries, veins, and capillaries form a series of hot- water pipes, through which the heated liquid is forced by a pump--the heart--while the heat is kept up, not by a central furnace and boiler, but by a multitude of little fires placed here and there along its course.

2. _Regulation_.--The temperature of the body is regulated by means of the pores of the skin and the mucous membrane in the air passages. When the system becomes too warm, the blood vessels on the surface expand, the blood fills them, the fluid exudes into the perspiratory glands, pours out upon the exterior, and by evaporation cools the body. [Footnote: Just as water sprinkled on the floor cools a room.--_Popular Physics_, p. 255.] When the temperature of the body is too low, the vessels contract, less blood goes to the surface, the perspiration decreases, and the loss of heat by evaporation diminishes. [Footnote: Thus one is enabled to go into an oven where bread is baking, or into the arctic regions where the mountains are snow and the rivers ice. Even by these extremes the temperature of the blood will be but slightly affected. In the one case, the flood gates of perspiration will be opened and the superfluous heat expended in turning the water to vapor; and, in the other, they will be tightly closed and all the heat retained.]

LIFE BY DEATH.--The body is being incessantly corroded, and portions borne away by the tireless oxygen. The scales of the epidermis are constantly falling off and being replaced by secretion from the cutis. The disks of the blood die, and new ones spring into being. On the continuance of this interchange depend our health and vigor. Every act is a destructive one. Not a bend of the finger, not a wink of the eye, not a thought of the brain but is at some expense of the machine itself. Every process of life is thus a process of death. The more rapidly this change goes on, and fresh, vigorous tissue takes the place of the old, the more elasticity and strength we possess.

CHANGE OF OUR BODIES.--There is a belief that our bodies change once in seven years. From the nature of the case, the rate must vary with the labor we perform; the organs most used altering oftenest. Probably the parts of the body in incessant employment are entirely reorganized many times within a single year. [Footnote: To use a homely simile, our bodies are like the Irishman's knife, which, after having had several new blades, and at least one new handle, was yet the same old knife.]

THE THREE VITAL ORGANS.--Death is produced by the stoppage of the action of any one of the three organs--the heart, the lungs, or the brain. They have, therefore, been termed the "Tripod of Life." Really, however, as Huxley has remarked, "Life has but two legs to stand upon." If respiration and circulation be kept up artificially, the removal of the brain will not produce death. [Footnote: When death really does take place, _i. e._, when the vital organs are stopped, it is noticeable that the tissues do not die for some time thereafter. If suitable stimulants be applied, as the galvanic battery, transfusion of blood, etc., the muscles may be made to contract, and many of the phenomena of life be exhibited. Dr. Brown- Sequard thus produced muscular action in the hand of a criminal, fourteen hours after his execution.]

WONDERS OF THE HEART.--The ancients thought the heart to be the seat of love. There were located the purity and goodness as well as the evil passions of the soul. [Footnote: Our common words, hearty, large-hearted, courage (_cor_, the heart), are remains of this fanciful theory.] Modern science has found the seat of the mental powers to be in the brain. But while it has thus robbed the heart of its romance, it has revealed wonders which eclipse all the mysteries of the past. This marvelous little engine throbs on continually at the rate of one hundred thousand beats per day, forty millions per year, often three billions without a single stop. It is the most powerful of machines. "Its daily work is equal to one third that of all the muscles. If it should expend its entire force in lifting its own weight vertically, it would rise twenty thousand feet in an hour." [Footnote: "The greatest exploit ever accomplished by a locomotive, was to lift itself through less than one eighth of that distance." Vast and constant as is this process, so perfect is the machinery, that there are persons who do not even know where the heart lies until disease or accident reveals its location.] Its vitality is amazing. The most tireless of organs while life exists, it is one of the last to yield when life expires. So long as a flutter lingers at the heart, we know the spark of being is not quite extinguished, and there is hope of restoration. During a life such as we sometimes see, it has propelled half a million tons of blood, yet repaired itself as it has wasted, during its patient, unfaltering labor. The play of its valves and the rhythm of its throb have never failed until, at the command of the great Master Workman, the "wheels of life have stood still." [Footnote: Our brains are seventy-five- year clocks. The Angel of Life winds them up once for all, then closes the case, and gives the key into the hand of the Angel of the Resurrection. Ticktack! Ticktack! go the wheels of thought; our will can not stop them, they can not stop themselves; sleep can not stop them; madness only makes them go faster; death alone can break into the case, and, seizing the ever-swinging pendulum which we call the heart, silence at last the clicking of the terrible escapement we have carried so long beneath our wrinkled foreheads.--HOLMES.]

FIG. 43.

THE LYMPHATIC CIRCULATION is intimately connected with that of the blood. It is, however, more delicate in its organization, and less thoroughly understood. Nearly every part of the body is permeated by a second series of capillaries, closely interlaced with the blood capillaries already described, and termed the Lymphatic system. The larger number converge into the thoracic duct--a small tube, about the size of a goose quill, which empties into the great veins of the neck (Fig. 43). Along their course the lymphatics frequently pass through _glands_,--hard, pinkish bodies of all sizes, from that of a hemp seed to an almond. These glands are often enlarged by disease, and then are easily felt.

_The Lymph_, which circulates through the lymphatics like blood through the veins, is a thin, colorless liquid, very like the serum. This fluid, probably in great measure an overflow from the blood vessels, is gathered up by the lymphatics, undergoes in the glands some process of preparation not well understood, and is then returned to the circulation.

FIG. 44.

OFFICE OF THE LYMPHATICS.--It is thought that portions of the waste matter of the body capable of further use are thus, by a wise economy, retained and elaborated in the system.

The _lacteals_, a class of lymphatics which will be described under Digestion (p. 166), aid in taking up the food; after a meal they become milk white. In the lungs, the lymphatics are abundant; sometimes absorbing the poison of disease, and diffusing it through the system. [Footnote: Persons have thus been poisoned by tiny particles of arsenic which evaporate from green wall paper, and float in the air.]

The lymphatics of the skin we have already spoken of as producing the phenomena of absorption, [Footnote: Pain is often relieved by injecting under the cuticle a solution of morphine, which is taken up by the absorbents, and so carried through the system.] Nature in her effort to heal a cut deposits an excess of matter to fill up the breach. Soon, the lymphatics go to work and remove the surplus material to other parts of the body.

Animals that hibernate are supported during the winter by the fat which their absorbents carry into the circulation from the extra supply they have laid up during the summer. In famine or in sickness, a man unconsciously consumes his own flesh.

DISEASES, ETC.--l. _Congestion_ is an unnatural accumulation of blood in any part of the body. The excess is indicated by the redness. If we put our feet in hot water, the capillaries will expand by the heat, and the blood will set that way to fill them. The red nose and purplish face of the drunkard show a congestion of the capillaries. Those vessels have lost their power of contraction, and so are permanently increased in size and filled with blood. Blushing is a temporary congestion. The capillaries being expanded only for an instant by the nervous excitement, contract again and expel the blood. [Footnote: Blushing is a purely local modification of the circulation of this kind, and it will be instructive to consider how a blush is brought about. An emotion--sometimes pleasurable, sometimes painful--takes possession of the mind; thereupon a hot flush is felt, the skin grows red, and according to the intensity of the emotion these changes are confined to the cheeks only, or extend to the "roots of the hair," or "all over." What is the cause of these changes? The blood is a red and a hot fluid; the skin reddens and grows hot, because its vessels contain an increased quantity of this red and hot fluid; and its vessels contain more, because the small arteries suddenly dilate, the natural moderate contraction of their muscles being superseded by a state of relaxation. In other words, the action of the nerves which cause this muscular contraction is suspended. On the other hand, in many people, extreme terror causes the skin to grow cold, and the face to appear pale and pinched. Under these circumstances, in fact, the supply of blood to the skin is greatly diminished, in consequence of an excessive stimulation of the nerves of the small arteries, which causes them to contract and so to cut off the supply of blood more or less completely.-- Huxley's _Physiology_.]

2. _Inflammation_ means simply a burning. If there is irritation or an injury at any spot, the blood sets thither and reddens it. This extra supply, both by its presence and the friction of the swiftly moving currents, produces heat. The pressure of the distended vessels upon the nerves frets them, and produces pain. The swelling stretches the walls of the blood vessels, and the serum or lymph oozes through. The four characteristics of an inflammation are redness, heat, pain, and swelling.

3. _Bleeding_, if from an artery, will be of red blood, and will come in jets; [Footnote: The elasticity of the arteries (p. 114) is a physical property, as may easily be shown by removing one from a dead body. If they were rigid and unyielding, a considerable portion of the heart's force would be uselessly expended against their walls. Their expansion is a passive state, and depends on the pressure of the blood within them; but their vital contractility is an active property.--The intermittent movement of the blood through the arteries is strikingly shown in the manner in which they bleed when wounded. When an artery is cut across, the blood spurts out with great force to a distance of several feet, but the flow is not continuous. It escapes in a series of jets, the long, slender scarlet stream rising and falling with each beat of the heart, and this pulsation of the blood stream tells at once that it comes from a wounded artery. But as the blood traverses these elastic tubes, the abruptness of the heart's stroke becomes gradually broken and the current equalized, so that the greater the distance from the heart the less obvious is the pulsation, until at length in the capillaries the rate of the stream becomes uniform.] if from the veins, it will be of dark blood, and will flow in a steady stream. If only a small vessel be severed, it may be checked by a piece of cloth held or bound firmly upon the wound. If a large trunk be cut, especially in a limb, make a knot in a handkerchief and tie it loosely about the limb; then, placing the knot on the limb, with a short stick twist the handkerchief tightly enough to stop the flow. If you have a piece of cloth to use as a pad, the knot will be unnecessary. If it be an artery that is cut, the pressure should be applied between the wound and the heart; if a vein, beyond the wound. If you are alone, and are severely wounded, or in an emergency, like a railroad accident, use the remedy which has saved many a life upon the battlefield--bind or hold a handful of dry earth upon the wound, elevate the part, and await surgical assistance.

4. _Scrofula_ is generally inherited. It is a disease affecting the lymphatic glands, most commonly those of the neck, forming "kernels," as they are called. It is, however, liable to attack any organ. Persons inheriting this disease can hope to ward off its insidious approaches only by the utmost care in diet and exercise; by the use of pure air and warm clothing, and by avoiding late hours and undue stimulus of all kinds. Probably the most fatal and common excitants of the latent seeds of scrofula are insufficient or improper food, and want of ventilation.

5. _A COLD_.--We put on a thinner dress than usual, or, when heated, sit in a cool place. The skin is chilled, and the perspiration checked. The blood, no longer cleansed and reduced in volume by the drainage through the pores, sets to the lungs for purification. That organ is oppressed, breathing becomes difficult, and the extra mucus secreted by the irritated surface of the membrane is thrown off by coughing. The mucous membrane of the nasal chamber sympathizes with the difficulty, and we have "a cold in the head," or a catarrh. In general, the excess of blood seeks the weakest point, and develops there any latent disease [Footnote: A party go out for a walk and are caught in a rain, or, coming home heated from some close assembly, throw off their coats to enjoy the deliciously cool breeze. The next day, one has a fever, another a slight headache, another pleurisy, another pneumonia, another rheumatism, while some of the number escape without any ill feeling whatever. The last had vital force sufficient to withstand the disturbance, but in the others there were various weak points, and to these the excess of blood has gone, producing congestion.] Where one person has been killed in battle, thousands have died of colds.

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Hygienic Physiology : with Special Reference to the Use of Alcoholic Drinks and NarcoticsChapter VI: Hygiene (2)

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