Chapter VI: Hygiene (1)

HINTS ABOUT WASHING AND BATHING.--The moment of rising from bed is the proper time for the full wash or bath with which one should commence the day. The body is then warm, and can endure moderately cold water better than at any other time; it is relaxed, and needs bracing; and the nerves, deadened by the night's repose, require a gentle stimulus. If the system be strong enough to resist the shock, cold water is the most invigorating; if not, a tepid bath will answer. [Footnote: Many persons have not the conveniences for a bath. To them, the following plan, which the author has daily employed for years, is commended. The necessities are: a basin full of soft water, a mild soap, a large sponge or a piece of flannel, and two towels--one soft, the other rough. The temperature of the water should vary with the season of the year--cold in summer and tepid in winter. Rub quickly the entire body with the wet sponge or flannel. (If more agreeable, wash and wipe only a part at a time, protecting the rest in cold weather with portions of clothing.) Dry the skin gently with a soft towel, and when quite dry, with the rough towel or flesh brush rub the body briskly four or five minutes till the skin is all aglow. The chest and abdomen need the principal rubbing. The roughness of the towel should be accommodated to the condition of the skin. Enough friction, however, must be given to produce at least a gentle warmth, indicative of the reaction necessary to prevent subsequent chill or languor. An invalid will find it exceedingly beneficial if a stout, vigorous person produce the reaction by rubbing with the hands.]

Before dressing, the whole body should be thoroughly rubbed with a coarse towel or flesh brush. At first, the friction may be unpleasant, but this sensitiveness will soon be overcome, and the keenest pleasure be felt in the lively glow which follows. A bath should not be taken just before nor immediately after a meal, as it will interfere with the digestion of the food. Soap should be employed occasionally, but its frequent use tends to make the skin dry and hard.

REACTION.--After taking a cold bath, there should be a prompt reaction. When the surface is chilled by cold water, the blood sets to the heart and other vital organs, exciting them to more vigorous action, and then, being thrown back to the surface, it reddens, warms, and stimulates the skin to an unwonted degree. This is called the reaction, and in it lies the invigorating influence of the cold bath. When, on the contrary, the skin is heated by a hot bath, the blood is drawn to the surface, less blood goes to the heart, the circulation decreases, and languor ensues. A dash of cold water is both necessary and refreshing at the close of a hot bath. [Footnote: The Russians are very fond of vapor baths, taken in the following manner. A large room is heated by stoves. Red-hot stones being brought in, water is thrown upon them, filling the room with steam. The bathers sit on benches until they perspire profusely, when they are rubbed with soapsuds and dashed with cold water. Sometimes, while in this state of excessive perspiration, they run out of doors and leap into snow banks.]

If, after a cold bath, there be felt no glow of warmth, but only a chilliness and depression, we are thereby warned that either proper means were not taken to bring on this reaction, or that the circulation is not vigorous enough to make such a bath beneficial. The general effect of a cool bath is exhilarating, and that of a warm one depressing. [Footnote: The sudden plunge into a cold bath is good for the strong and healthy, but too severe for the delicate. One should always wet first the face, neck, and chest. It is extremely injurious to stand in a bath with only the feet and the lower limbs covered by the water, for the blood is thus sent from the extremities to the heart and internal organs, and they become so burdened that reaction may be out of their power. A brisk walk, or a thorough rubbing of the skin, before a cold bath or swim, adds greatly to its value and pleasure.] Hence the latter should not ordinarily be taken oftener than once a week, while the former may be enjoyed daily. (See p. 289.)

SEA BATHING is exceedingly stimulating, on account of the action of the salt and the exciting surroundings. Twenty minutes is the utmost limit for bathing or swimming in salt or fresh water. A chilly sensation should be the signal for instant removal. It is better to leave while the glow and buoyancy which follow the first plunge are still felt. Gentle exercise after a bath is beneficial.

CLOTHING in winter, to keep us warm, should repel the external cold and retain the heat of the body. In summer, to keep us cool, it should not absorb the rays of the sun, and should permit the passage of the heat of the body. At all seasons, it should be porous, to give ready escape to the perspiration, and a free admission of air to the skin. We can readily apply these essential conditions to the different kinds of clothing.

_Linen_ is soft to the touch, and is a good conductor of heat. Hence it is pleasant for summer wear, but, being apt to chill the surface too rapidly, it should not be worn next the skin.

_Cotton_ is a poorer conductor of heat and absorber of moisture, and is therefore warmer than linen. It is sufficiently cool for summer wear, and affords better protection against sudden changes.

_Woolen_ absorbs moisture slowly, and contains much air in its pores. It is therefore a poor conductor of heat, and guards the wearer against the vicissitudes of our climate.

The outer clothing may be adapted largely to ornament, and may be varied to suit our fancy and the requirements of society. The underclothing should always be sufficient to keep us warm. Woolen should be worn next the skin at all times; light gossamer garments in the heat of summer, and warm, porous flannels in midwinter.

Light-colored clothing is not only cooler in summer, but warmer in winter. As the warmth of clothing depends greatly on the amount of air contained in its fibers, fine, loose, porous cloth with a plenty of nap is best for winter wear. Firm and heavy goods are not necessarily the warmest. Furs are the perfection of winter clothing, since they combine warmth with lightness. Two light woolen garments are warmer than one heavy one, as there is between them a layer of nonconducting air.

All the body except the head should be equally protected by clothing. Whatever fashion may dictate, no part covered to-day can be uncovered tonight or to-morrow, except at the peril of health. It is a most barbarous and cruel custom to leave the limbs of little children unprotected, when adults would shiver at the very thought of exposure. Equally so is it for children to be thinly clad for the purpose of hardening them. To go shivering with cold is not the way to increase one's power of endurance. The system is made more vigorous by exercise and food; not by exposure. In winter, we should wear warm shoes with thick soles, and rubbers when it is damp. At night, and after exercise, we require extra clothing. (See p. 295.)

DISEASES, ETC.--l. _Erysipelas_ is an inflammation (see Inflammation) of the skin, and often begins in a spot not larger than a pin head, which spreads with great rapidity. It is very commonly checked by the application of a solution of iodine. The burning and contracting sensation may be relieved by cloths wrung out of hot water.

2. _Eczema_ (Salt Rheum, etc.) is of constitutional origin. It is characterized by an itching, burning, reddened eruption, in which a serous discharge exudes and dries into crusts or scales. The skin thickens in patches, and painful fissures are formed, which are irritated by exposure to air or water. Eczema denotes debility. It occurs in various forms, and, like erysipelas, should be treated by a physician.

3. _Corns_ are thickened cuticle, caused by pressure or friction. They most frequently occur on the feet; but are produced on the shoemaker's knee by constant hammering, and on the soldier's shoulder by the rubbing of his musket. This hard portion irritates the sensitive cutis beneath, and so causes pain. A corn will soften in hot water, when it may be pared with a sharp knife. If the cause be removed, the corn will not return.

4. _Ingrowing Nails_ are caused by pressure, which forces the edge of the toe nail into the flesh. They may be cured by carefully cutting away the part which has mal-grown, and then scraping the back of the nail till it is thin, making a small incision in the center, at the top. The two portions, uniting, will draw away the nail from the flesh at the edge. Ingrowing nails may be prevented by wearing broad-toed shoes.

5. _Warts_ are overgrown papillæ (Fig. 24). They may generally be removed by the application of glacial acetic acid, or a drop of nitric acid, repeated until the entire structure is softened. Care must be taken to keep the acid from touching the neighboring skin. The capricious character of warts has given rise to the popular delusion concerning the influence of charms upon them.

6. _Chilblain_ is a local inflammation affecting generally the feet, the hands, or the lobes of the ear. Liability to it usually passes away with manhood. It is not caused by "freezing the feet," as many suppose, though attacks are brought on, or aggravated, by exposure to cold, followed by sudden warming. Chilblain is subject to daily congestion (see Congestion), manifested by itching, soreness, etc., commonly occurring at night. The best preventive is a uniform temperature, and careful protection against the cold by warm clothing, especially for the feet.

PRACTICAL QUESTIONS.

1. If a hair be plucked out, will another grow in its place?

2. What causes the hair to "stand on end" when we are frightened?

3. Why is the skin roughened by riding in the cold?

4. Why is the back of a washerwoman's hand less water-soaked than the palm?

5. What would be the length of the perspiratory tubes in a single square inch of the palm, if placed end to end?

6. What colored clothing is best adapted to all seasons?

7. What is the effect of paint and powder on the skin?

8. Is waterproof clothing healthful for constant wear?

9. Why are rubbers cold to the feet?

10. Why does the heat seem oppressive when the air is moist?

11. Why is friction of the skin invigorating after a cold bath?

12. Why does the hair of domestic animals become roughened in winter?

13. Why do fowls spread their feathers before they perch for the night?

14. How can an extensive burn produce congestion of the lungs?

15. Why do we perspire so profusely after drinking cold water?

16. How can we best prevent skin diseases, colds, and rheumatism?

17. What causes the difference between the hard hand of a blacksmith and the soft hand of a woman?

18. Why should a painter avoid getting paint on the palm of his hand?

19. Why should we not use the soap or the soiled towel at a hotel?

20. Which teeth cut like a pair of scissors?

21. Which teeth cut like a chisel?

22. Which should be clothed the warmer, a merchant or a farmer? 23. Why should we not crack nuts with our teeth?

24. Do the edges of the upper and the lower teeth meet?

25. When fatigued, would you take a cold bath?

26. Why is the outer surface of a kid glove finer than the inner?

27. Why will a brunette endure the sun's rays better than a blonde?

28. Does patent leather form a healthful covering for the feet?

29. Why are men more frequently bald than women?

30. On what part of the head does baldness commonly occur? Why?

31. What does the combination in our teeth of canines and grinders suggest as to the character of our food?

32. Is a staid, formal promenade suitable exercise?

33. Is there any danger in changing the warm clothing of our daily wear for the thin one of a party?

34. Should we retain our overcoat, shawl, or furs when we come into a warm room?

35. Which should bathe the oftener, students or outdoor laborers?

36. Is abundant perspiration injurious?

37. How often should the ablution of the entire body be performed?

38. Why is cold water better than warm, for our daily ablution?

39. Why should our clothing always fit loosely?

40. Why should we take special pains to avoid clothing that is colored by poisonous dyestuffs? (See p. 296.)

41. What general principles should guide us as to the length and frequency of baths In salt or fresh water?

42. What is the beneficial effect of exercise upon the functions of the skin?

43. How can we best show our admiration and respect for the human body?

44. Why is the scar of a severe wound upon a negro sometimes white?

IV.

RESPIRATION AND THE VOICE.

"The smooth soft air with pulse-like waves Flows murmuring through its hidden caves, Whose streams of brightening purple rush, Fired with a new and livelier blush; While all their burden of decay The ebbing current steals away."

ANALYSIS OF RESPIRATION AND THE VOICE.

_ | 1. The Larnyx. _ | 2. The Vocal Cords. | 1. ORGANS OF VOICE.....| 3. Different Tones of Voice. | | 4. Speech. | |_5. Formation of Vocal Sounds. | _ | | 1. The Trachea. | | 2. The Bronchial Tubes. | 2. ORGANS OF RESPIRA- | 3. The Cells. | TION.........| 4. The Lung Wrapping. | |_5. The Cilia. | _ | | 1. Inspiration. | 3. HOW WE BREATHE......|_2. Expiration. | _ | | 1. Sighing. | | 2. Coughing. | | 3. Sneezing. | 4. MODIFICATIONS OF | 4. Snoring. | THE BREATH.......| 5. Laughing, and Crying. | | 6. Hiccough. | |_7. Yawning. | | 5. CAPACITY OF THE LUNGS. | _ | | 1. The Need of Air. | | 2. Action of Air in the Lungs. | | 3. Tests of the Breath. | | 4. Analysis of Expired Air. | | 5. Effect of Rebreathed Air. | | _ | 6. HYGIENE.............| | a. _The Sources of | | | Impurity._ | | | b. _The Sick Room._ | | 6. Concerning | c. _The Sitting Room._ | | the Need of | d. _The Bedroom._ | |_ Ventilation.| e. _The Church._ | | f. _The Schoolroom._ | | g. _How we should | |_ Ventilate._ | | 7. THE WONDERS OF RESPIRATION. | _ | | 1. Constriction of the Lungs. | | 2. Bronchitis. | | 3. Pleurisy. | | 4. Pneumonia. |_8. DISEASES............| 5. Consumption | 6. Asphyxia. | 7. Diptheria. | 8. Croup. |_9. Stammering.

RESPIRATION AND THE VOICE.

The Organs of Respiration and the Voice are the _larynx_, the _trachea_, and the _lungs_.

DESCRIPTION OF THE ORGANS OF THE VOICE.--l. _The Larynx_.--In the neck, is a prominence sometimes called Adam's apple. It is the front of the _larynx_. This is a small triangular, cartilaginous box, placed just below the root of the tongue, and at the top of the windpipe. The opening into it from the throat is called the _glottis_; and the cover, the _epiglottis_ (_epi_, upon; _glotta_, the tongue). The latter is a spoon-shaped lid, which opens when we breathe, but, by a nice arrangement, shuts when we try to swallow, and so lets our food slip over it into the _sophagus_ (e-sof'-a-gus), the tube leading from the pharynx to the stomach (Fig. 27).

If we laugh or talk when we swallow, our food is apt to "go the wrong way," _i. e._, little particles pass into the larynx, and the tickling sensation which they produce forces us to cough in order to expel the intruders.

2. _The Vocal Cords_.--On each side of the _glottis_ are the so- called _vocal cords_. They are not really cords, but merely elastic membranes projecting from the sides of the box across the opening. [Footnote: The cartilages and vocal cords may be readily seen in the larynx of an ox or sheep. If the flesh be cut off, the cartilages will dry, and will keep for years.] When not in use, they spread apart and leave a V-shaped orifice (Fig. 28), through which the air passes to and from the lungs. If the cords are tightened, the edges approach sometimes within 1/100 of an inch of each other, and, being thrown into vibration, cause corresponding vibrations in the current of air. Thus sound is produced in the same manner as by the vibrations of the tongues of an accordion, or the strings of a violin, only in this case the strings are scarcely an inch long.

FIG. 27.

DIFFERENT TONES OF THE VOICE.--The higher tones of the voice are produced when the cords are short, tight, and closely in contact; the lower, by the opposite conditions. Loudness is regulated by the quantity of air and force of expulsion. A falsetto voice is thought to be the result of a peculiarity in the pharynx (Fig. 27) at the back part of the nose; it is more probably produced by some muscular maneuver not yet fully understood. When boys are about fourteen years of age, the larynx enlarges, and the cords grow proportionately longer and coarser; hence, the voice becomes deeper, or, as we say, "changes." The peculiar harshness of the voice at this time seems to be due to a congestion of the mucous membrane of the cords. The change may occur very suddenly, the voice breaking in a single night.

FIG. 28.

Speech is voice modulated by the lips, tongue, [Footnote: The tongue is styled the "unruly member," and held responsible for all the tattling of the world; but when the tongue is removed, the adjacent organs in some way largely supply the deficiency, so that speech is still possible. Huxley describes the conversation of a man who had two and one half inches of his tongue preserved in spirits, and yet could converse intelligibly. Only the two letters _t_ and _d_ were beyond his power; the articulation of these involves the employment of the tip of the tongue; hence, "tin" he converted into "fin," and "dog" into "thog."] palate, and teeth. [Footnote: An artificial larynx may be made by using elastic bands to represent the vocal cords, and by placing above them chambers which by their resonance will produce the same effect as the cavities lying above the larynx. An artificial speaking machine was constructed by Kempelen, which could pronounce such sentences as, "I love you with all my heart," in different languages, by simply touching the proper keys.] Speech and voice are commonly associated, but speech may exist without the voice, for when we whisper we articulate the words, although there is no vocalization, _i. e._, no action of the larynx. [Footnote: We can observe this by placing the hand on the throat, and noticing the absence of vibrations when we whisper, and their presence when we talk. The difference between vocalization and non-vocalization is seen in a sigh and a groan, the latter being the former vocalized. Whistling is a pure mouth sound, and does not depend on the voice. Laughter is vocal, being the aspirated vowels, a, e, or o, convulsively repeated.] (See p. 297.)

FIG. 29.

FORMATION OF VOCAL SOUNDS.--The method of modulating voice into speech may be seen by producing the pure vowel sounds _a, e_, etc., from one expiration, the mouth being kept open while the form of the aperture is changed for each vowel by the tongue and the lips. _H_ is only an explosion, or forcible throwing of a vowel sound from the mouth. [Footnote: When, in sounding a vowel, the sound coincides with a sudden change in the position of the vocal cords from one of divergence to one of approximation, the vowel is pronounced with the _spiritus asper_. When the vocal cords are brought together before the blast of air begins, the vowel is pronounced with the _spiritus lenis._--FOSTER.]

The consonants, or short sounds, may also be made without interrupting the current of air, by various modifications of the vocal organs. In sounding singly any one of the letters, we can detect its peculiar requirements. Thus _m_ and _n_ can be made only by blocking the air in the mouth and sending it through the nose; _l_ lets the air escape at the sides of the tongue; _r_ needs a vibratory movement of the tongue; _b_ and _p_ stop the breath at the lips; _k_ and _g_ (hard), at the back of the palate. Consonants like _b_ and _d_ are abrupt, or, like _l_ and _s_, continuous. Those made by the lips are termed _labials_; those by pressing the tongue against the teeth, _dentals_; those by the tongue, _linguals_.

The child gains speech slowly, first learning to pronounce the vowel _a_, the consonants _b, m_, and _p_, and then their unions --_ba, ma, pa_.

DESCRIPTION OF THE ORGANS OF RESPIRATION.--Beneath the larynx is the windpipe, or _trachea_ (see Fig. 29), so called because of its roughness. It is strengthened by C-shaped cartilages with the openings behind, where they are attached to the sophagus. At the lower end, the trachea divides into two branches, called the right and left _bronchi_. These subdivide in the small bronchial tubes, which ramify through the lungs like the branches of a tree, the tiny twigs of which at last end in clusters of cells so small that there are six hundred million in all. This cellular structure renders the lungs exceedingly soft, elastic, and sponge-like. [Footnote: The lungs of slaughtered animals are vulgarly called "lights," probably on account of their lightness. They are similar in structure to those of man. They will float on water, and if a small piece be forcibly squeezed between the fingers (notice the creaking sound it gives), it will retain sufficient air to make it buoyant.]

FIG. 30.

The stiff, cartilaginous rings, so noticeable in the rough surface of the trachea and the bronchi, disappear as we reach the smaller bronchial tubes, so that while the former are kept constantly open for the free admission of air, the latter are provided with elastic fibers by which they may be almost closed.

WRAPPING OF THE LUNGS.--The lungs are invested with a double covering--the _pleura_--one layer being attached to the lungs and the other to the walls of the chest. It secretes a fluid which lubricates it, so that the layers glide upon each other with perfect ease. [Footnote: These pleural sacs are distinct and closed; hence, when the ribs are raised, a partial vacuum being formed in the sacs, air rushes in, and distends the pulmonary lobules.] The lungs are lined with mucous membrane, exceedingly delicate and sensitive to the presence of anything except pure air. We have all noticed this when we have breathed any thing offensive.

FIG. 31.

THE CILIA.--Along the air passages are minute filaments (_cilia_, Fig. 32), which are in constant motion, like a field of grain stirred by a gentle breeze. They serve to fan the air in the lungs, and produce an outward current, which is useful in catching dust and fine particles swept inward with the breath.

HOW WE BREATHE.--Respiration consists of two acts--taking in the air, or _inspiration_, and expelling the air, or _expiration_.

FIG. 32.

1. _Inspiration_.--When we draw in a full breath, we straighten the spine and throw the head and shoulders back, so as to give the greatest advantage to the muscles. [Footnote: If we examine the bony cage of the thorax or chest in Fig. 8, we shall see that the position of the ribs may alter its capacity in two ways.

1. As they run obliquely downward from the spine, if the sternum or breastbone be lifted in front, the diameter of the chest will be increased.

2. The ribs are fastened by elastic cartilages, which stretch as the muscles that lift the ribs contract, and so increase the breadth of the chest.]

At the same time, the diaphragm [Footnote: The diaphragm is the muscular partition between the chest and the abdomen. It is always convex toward the former, and concave toward the latter (Fig. 31). Long muscular fibers extend from its center toward the ribs in front and the spine at the back. When these contract, they depress and flatten the diaphragm; when they relax, it becomes convex again. In the former case, the bowels are pressed downward and the abdomen pushed outward; in the latter, the bowels spring upward, and the abdomen is drawn inward.] descends and presses the walls of the abdomen outward. Both these processes increase the size of the chest. Thereupon, the elastic lungs expand to occupy the extra space, while the air, rushing in through the windpipe, pours along the bronchial tubes and crowds into every cell. [Footnote: It is said that in drawing a full breath, the muscles exert a force equal to raising a weight of seven hundred and fifty pounds. When we are about to make a great effort, as in striking a heavy blow, we naturally take a deep inspiration, and shut the glottis. The confined air makes the chest tense and firm, and enables us to exert a greater force. As we let slip the blow, the glottis opens and the air escapes, often with a curious aspirated sound as is noticeable in workmen. To make a good shot with a rifle, we should take aim with a full chest and tight breath, since then the arms will have a steadier support.]

2. _Expiration_.--When we forcibly expel the air from our lungs, the operation is reversed. We bend forward, draw in the walls of the abdomen, and press the diaphragm upward, while the ribs are pulled downward,--all together diminishing the size of the chest, and forcing the air outward.

Ordinary, quiet breathing is performed mainly by the diaphragm,--one breath to every four beats of the heart, or eighteen per minute. (See p. 299.)

MODIFICATIONS OF THE BREATH.--_Sighing_ is merely a prolonged inspiration followed by an audible expiration. _Coughing_ is a violent expiration in which the air is driven through the mouth. _Sneezing_ differs from coughing, the air being forced through the nose. _Snoring_ is produced by the passage of the breath through the pharynx when the tongue and soft palate are in certain positions. [Footnote: The soft palate must have fallen back in such a manner as nearly or quite to close the entrance to the nasal cavity from the throat, and the tongue must also be thrown back so far as to leave only a narrow opening between it and the soft palate. The noise is produced by the air being forced either inward or outward through this opening. A snore results also when, with a closed mouth, the air is forced between the soft palate and the back wall of the pharynx into the nasal cavity. With deep breathing, perhaps accompanied by a variation in the position of the soft palate, a rattling noise may be heard in addition to the snoring, which is due to a vibration of the soft palate.--F. A. FERNALD, in "How we Sneeze, Laugh, Stammer, and Sigh."--_Popular Science Monthly_, Feb., 1884.] _Laughing_ and _crying_ are very much alike. The expression of the face is necessary to distinguish between them. The sounds are produced by short, rapid contractions of the diaphragm. _Hiccough_ is confined to inspiration. It is caused by a contraction of the diaphragm and a constriction of the glottis; the current of air just entering, as it strikes the closed glottis, gives rise to the well-known sound. _Yawning_, or _gaping_, is like sighing. [Footnote: The usefulness of a yawn lies in bringing up the arrears, as it were, of respiration, when it has fallen behindhand, either through fatigue or close attention to other occupation. The stretching of the jaws and limbs may also serve to equalize the nervous influence, certain muscles having become uneasy on account of being stretched or contracted for a long time.] It is distinguished by a wide opening of the mouth and a deep, profound inspiration. Both processes furnish additional air, and therefore probably meet a demand of the system for more oxygen. Frequently, however, they are like laughing, sobbing, etc., merely a sort of contagion, which runs through an audience, and seems almost irresistible.

THE CAPACITY OF THE LUNGS.--If we take a deep inspiration, and then forcibly exhale all the air we can expel from the lungs, this amount, which is termed the _breathing capacity_, will bear a very close correspondence to our stature. For a man of medium height (five feet eight inches) it will be about two hundred and thirty cubic inches, [Footnote: Of this amount, one hundred cubic inches can be forced in only by an extra effort, and is available for emergencies, or for purposes of training, as in singing, climbing, etc. It is of great importance, since, if the capacity of the lungs only equaled our daily wants, the least obstruction would prove fatal.] or a gallon, and for each inch of height between five and six feet there will be an increase of eight cubic inches. In addition, it is found that the lungs contain about one hundred cubic inches which can not be expelled, thus making their entire contents about three hundred and thirty cubic inches, or eleven pints. The extra amount always on hand in the lungs is of great value, since thereby the action of the air goes on continuously, even during a violent expiration. In ordinary breathing, only about twenty or thirty cubic inches (less than a pint) of air pass in and out.

THE NEED OF AIR.--The body needs food, clothing, sunshine, bathing, and. drink; but none of these wants is so pressing as that for air. The other demands may be met by occasional supplies, but air must be furnished every moment or we die. Now the vital element of the atmosphere is oxygen gas. [Footnote: See "Steele's Popular Chemistry," p. 30. The atmosphere consists of one fifth oxygen and four fifths nitrogen. The former is the active element; and the latter, the passive. Oxygen alone would be too stimulating, and must be restrained by the neutral nitrogen. Separately, either element of the air would kill us.] This is a stimulating, life- giving principle. No tonic will so invigorate as a few full, deep breaths of cold, pure air. Every organ will glow with the energy of the fiery oxygen.

ACTION OF THE AIR IN THE LUNGS.--In the delicate cells of the lungs, the air gives up its oxygen to the blood, and receives in turn carbonic-acid [Footnote: More properly _Carbon dioxide_.] gas and water, foul with waste matter which the blood has picked up in its circulation through the body. The blood, thus purified and laden with the inspiring oxygen, goes bounding through the system, while the air we exhale carries off the impurities. In this process, the blood changes from purple to red. If we examine our breath, we can readily see what it has removed from the blood.

TESTS OF THE BREATH.--1. Breathe into a jar, and on lowering into it a lighted candle, the flame will be instantly extinguished; thus indicating the presence of carbonic-acid gas. 2. Breathe upon a mirror, and a film of moisture will show the vapor. [Footnote: There is a close relation between the functions of the skin, the lungs, and the kidneys--the scavengers of the body. They all carry off water from the blood, and when the function of one of the three is, in this respect, interfered with, the others are called upon to perform its functions. When the function of perspiration is deranged, the lungs and kidneys are required to perform heavier duty, and this may lead to disease (see p. 62).] 3. If breath be confined in a bottle, the animal matter will decompose and give off an offensive odor.

ANALYSIS OF THE EXPIRED AIR shows that it has lost about twenty-five per cent of its oxygen, and gained an equal amount of carbonic-acid gas, besides moisture, and organic impurities. Our breath, then, is air robbed of its vitality, and containing in its place a gas as fatal to life [Footnote: Carbonic-acid gas can not be breathed when undiluted, as the glottis closes and forbids its passage into the lungs. Air containing only three or four per cent acts as a narcotic poison (MILLER), and a much smaller proportion will have an injurious effect. The great danger, however, lies in the organic particles constantly exhaled from the lungs and the skin, which, it is believed, are often direct and active poisons.] as it is to a flame, and effete matter which is disagreeable to the smell, injurious to the health, and which may contain the germs of serious disease.

THE EVIL EFFECT OF REBREATHING the air can not be overestimated. We take back into our bodies that which has just been rejected. The blood thereupon leaves the lungs, bearing, not the invigorating oxygen, but refuse matter to obstruct the whole system. We soon feel the effect. The muscles become inactive. The blood stagnates. The heart acts slowly. The food is undigested. The brain is clogged. The head aches. Instances of fatal results are only too frequent. [Footnote: During the English war in India, in the eighteenth century, one hundred and forty-six prisoners were shut up in a room scarcely large enough to hold them. The air could enter only by two narrow windows. At the end of eight hours, but twenty-three persons remained alive, and these were in a most deplorable condition. This prison is well called "The Black Hole of Calcutta."--Percy relates that after the battle of Austerlitz, three hundred Russian prisoners were confined in a cavern, where two hundred and sixty of them perished in a few hours.--The stupid captain of the ship _Londonderry_, during a storm at sea, shut the hatches. There were only seven cubic feet of space left for each person, and in six hours ninety of the passengers were dead.] The constant breathing of even the slightly impure air of our houses can not but tend to undermine the health. The blood is not purified, and is thus in a condition to receive the seeds of disease at any time. The system uninspired by the energizing oxygen is sensitive to cold. The pale cheek, the lusterless eye, the languid step, speak but too plainly of oxygen starvation. In such a soil, catarrh, scrofula, and kindred diseases run riot. [Footnote: One not very strong, or unable powerfully to resist conditions unfavorable to health, and with a predisposition to lung disease, will be sure, sooner or later, by partial lung starvation and blood poisoning, to develop pulmonary consumption. _The lack of what is so abundant and so cheap--good, pure air--is unquestionably the one great cause of this terrible disease_.--BLACK'S _Ten Laws of Health_.]

CONCERNING THE NEED FOR VENTILATION.--The foul air which passes off from the lungs and through the pores of the skin does not fall to the floor, but diffuses itself through the surrounding atmosphere. A single breath will to a trifling but certain extent taint the air of a whole room. [Footnote: This grows out of a well-known philosophical principle called the Diffusion of Gases, whereby two gases tend to mix in exact proportions, no matter what may be the quantity of each.--STEELE'S _Popular Chemistry,_ p. 86, and _Popular Physics,_ p. 52.] A light will vitiate as much air as a dozen persons. Many breaths and lights therefore rapidly unfit the air for our use.

The perfection of ventilation is reached when the air of a room is as pure as that out of doors. To accomplish this result, it is necessary to allow for each person six hundred cubic feet of space, while ventilation is still going on in the best manner known.

In spite of these well-known facts, scarcely any pains are taken to supply fresh air, while the doors and windows where the life-giving oxygen might creep in are hermetically stopped.

How often is this true of the sick room. Yet here the danger of bad air is intensified. The expired breath of the patient is peculiarly threatening to himself as well as to others. Nature is seeking to throw off the poison of the disease. The scavengers of the body are all at work. The breath and the insensible perspiration are loaded with impurities. [Footnote: The floating dust in the air, revealed to us by the sunbeam shining through a crack in the blinds, shows the abundance of these impurities, and also the presence of germs which, lodging in the lungs, may implant disease, unless thrown off by a vigorous constitution. "On uncovering a scarlet fever patient, a cloud of fine dust is seen to rise from the body--contagious dust, that for days will retain its poisonous properties."--YOUMANS. (See p. 300.)] The odor is oftentimes exceedingly offensive. Sick and well alike need an abundance of fresh air. But, too often, it is the only want not supplied.

Our sitting rooms, heated by furnaces or red-hot stoves, generally have no means of ventilation, or, if provided, they are seldom used. A window is occasionally dropped to give a little relief, as if pure air were a rarity, and must be doled out to the suffering lungs in morsels, instead of full and constant draughts. The inmates are starved by scanty lung food, and stupefied by foul air. The process goes on year by year. The weakened and poisoned body at last succumbs to disease, while we, in our blindness and ignorance, talk of the mysterious Providence which thus untimely cuts down the brightest intellects. The truth is, death is often simply the penalty for violating nature's laws. Bad air begets disease; disease begets death.

In our churches, the foul air left by the congregation on Sunday is shut up during the week, and heated for the next Lord's day, when the people assemble to rebreathe the polluted atmosphere. They are thus forced, with every breath they take, to violate the physical laws of Him whom they meet to worship,--laws written not three thousand years ago upon Mount Sinai on tables of stone, but to-day engraved in the constitution of their own living, breathing bodies. On brains benumbed and starving for oxygen, the purest truth and the highest eloquence fall with little force.

We sleep in a small bedroom from which every breath of fresh air is excluded, because we believe night air to be unhealthy, [Footnote: There is a singular prejudice against the night air. Yet, as Florence Nightingale aptly says, what other air can we breathe at night? We then have the choice between foul air within and pure air without. For, in large cities especially, the night air is far more wholesome than that of the daytime. To secure fresh air at night, we must open the windows of our bedroom.] and so we breathe its dozen hogsheads of air over and over again, and then wonder why we awaken in the morning so dull and unrefreshed! Return to our room after inhaling the fresh, morning air, and the fetid odor we meet on opening the door, is convincing proof how we have poisoned our lungs during the night.

Each room should be supplied with two thousand feet of fresh air per hour for every person it contains. Our ingenuity ought to find some way of doing this advantageously and pleasantly. A moiety of the care we devote to delicate articles of food, drink, and dress would abundantly meet this prime necessity of our bodies.

Open the windows a little at the top and the bottom. Put on plenty of clothing to keep warm by day and by night, and then let the inspiring oxygen come in as freely as God has given it. Pure air is the cheapest necessity and luxury of life. Let it not be the rarest!

SCHOOLROOM VENTILATION.--Who, on going from the open air of a clear, bracing winter's day, into a crowded schoolroom, late in the session, has not noticed the disagreeable odor, and been for a moment nauseated and half stifled by the oppressive atmosphere! It is not strange. See how many causes here combine to pollute the air. If the room is heated by a stove, quantities of carbonic-oxide and carbonic-acid gases, as well as other products of combustion, driven by downward drafts in the flue, escape through seams and cracks and the occasionally opened door of the stove. In the case of a furnace, the same effect is too often experienced, and the odor of coal gas is a common one, especially when the fire is replenished. The insensible perspiration is more active in children than in adults; they, moreover, rush in with their clothing saturated with the perspiration induced by their sports; so that, on the average, each pupil, during school hours, loads the air with about half a pint of aqueous vapor. The children come, oftentimes, from homes that are close, ill- ventilated, and uncleanly; and frequently from sick rooms, bringing in their clothing the germs of disease. (See p. 304.) Some of the pupils may even bear traces of illness, or have unsound organs, and so their breath and exhalations be poisonous.

In addition to all this, the air is filled with dust brought in and kept astir by many busy feet; with ashes floating from the stove or furnace; and especially with chalk dust. The modern method of teaching requires a large amount of blackboard work, and the air of the schoolroom is thus loaded with chalk particles. These collect in the nasal passages, and the upper part of the larynx, and irritate the membrane, perhaps laying the foundation of catarrh.

The usual schoolroom atmosphere bears in the pupils the natural fruit of frequent headaches, inattention, weariness, and stupor; but in the teacher its frightful influence is most apparent. His labor is severe, his worry of mind is constant, and, when he finishes his day's work, he is generally too tired to take proper physical exercise. He consequently labors on with impaired health, or is forced to abandon his profession.

Instead of six hundred feet of space being allowed for each pupil, as perfect ventilation demands--the lowest estimate being two hundred and fifty feet--often not over one hundred feet are afforded. Instead of two thousand cubic feet of fresh air being supplied every hour for each person, and as much foul air removed, which, all physiologists assert, is needed for perfect health, perhaps no means of ventilation at all are provided, and none is secured except what an occasionally opened door, or the benevolent cracks and chinks in the building furnish the suffering lungs. [Footnote: Imagine fifty pupils put into a class room thirty feet long, twenty-five feet wide, and ten feet high. This would generally be considered a very liberal provision. Such a room contains seven thousand five hundred cubic feet of air. But it furnishes only one hundred and fifty feet of space for each pupil. Allowing ten cubic feet of air per pupil each minute, in fifteen minutes after assembling, the entire atmosphere of the room is tainted, and unfit to be rebreathed. The demand of health is that at least one thousand five hundred cubic feet of pure air should be admitted into this room every minute, and as much be removed.]

HOW SHALL WE VENTILATE?--The usual method of ventilation depends upon the fact that hot air is lighter than cold air, and so the cold air tends, by the force of gravity, to fall and compel the warm air to rise. Thus, if we open the door of a heated room, and hold a lighted candle first at the top, and then at the bottom, we can see, by the deflection of the flame, that there is a current of air setting outward at the top, and another setting inward at the bottom of the opening. A handkerchief held loosely, or the smoke of a smoldering match, in front of a fireplace will show a current of air passing up the chimney; this is caused by the difference of temperature between the air in the room and the outside atmosphere. _Upon this difference of temperature, all ordinary ventilation is based_. [Footnote: Public buildings are sometimes ventilated by mechanical means, _i. e._, immense fans which are turned by machinery, and thus set the air in motion. Such methods are, however, expensive, and rarely adopted, except where power is also used for other purposes.] A proper treatment of this subject and its practical applications, would require a book by itself. There is room here for only a few general statements and suggestions.

1. Two openings are always necessary to produce a thorough change of air. (See "Popular Chemistry," p. 70.) Put a lighted candle in a bottle. The flame will soon be extinguished. The oxygen of the little air in the bottle is burned out, and carbonic acid has taken its place. Now place over the mouth of the bottle a lamp chimney, and insert in the chimney a strip of cardboard, thus dividing the passage. On relighting the candle, it will burn freely. The smoke of a bit of smoldering paper will show that two opposite currents of air are established, one setting into the bottle, the other outward.

2. In the winter, when our schoolrooms, churches, public halls, etc., are heated artificially, ventilation is comparatively easy if properly arranged. [Footnote: For the escape of bad air, Dr. Bell suggests that an efficient foul-air shaft may be fitted to the commonest of stoves by simply inclosing the stovepipe in a jacket--that is, in a pipe two or three inches greater in diameter. This should be braced round the stovepipe and left open at the end next the stove. At its entrance into the chimney, a perforated collar should separate it from the stovepipe.] The required difference of temperature is kept up with little difficulty. The fresh air admitted to the room should then be heated [Footnote: Ventilation is change of air, and, unless scientifically arranged, and especially unless the incoming volume of air be warmed in cold weather, such change of atmosphere means cold currents, with their attendant train of catarrhs, bronchitis, neuralgia, rheumatism, and all the evils that spring from these diseases. The raw, damp, frosty air of our ever-changing winter temperature ought not to have uncontrolled and constant ingress to our dwellings. Air out of doors is suited to out of door habits. It is healthy and bracing when the body is coated and wrapped, and prepared to meet it, and when exercise can be taken to keep up the circulation; but to live under cover is to live artificially, and such essential conditions must be observed as suit an abnormal state. All the evils attaching to ventilation, as it is generally effected, spring from the neglect of this consistency.--_Westminster Review_.] either by a furnace, or by passing over a stove, or through a coil of steam pipes. This cold air should always be taken directly from out of doors, and not from a cellar, or from under a piazza, where contamination is possible.

3. In order to remove the impure air, there should be ventilators provided at or near the floor, opening into air shafts, or pipes leading upward through the roof, with proper orifices at the top. These ventilating pipes should be heated artificially so as to produce a draught. They may form one of the flues of a chimney in which there is a constant fire; or be carried upward in a large flue through the center of which runs the smoke pipe of the furnace or stove; [Footnote: This plan has been adopted in the newer school buildings of Elmira, N. Y. The older buildings were provided with ventilating pipes, not heated artificially, and hence of no service. These pipes are rendered effective, however, by conducting them into a small room in the garret, heated by a coal stove. From this room, a large exit pipe leads to the roof, where it terminates in an Emerson's ventilator. So strong a draught is thus established that throughout the building air is taken from the floors, and consequently the cooler portion of the rooms, at a velocity of three to five feet per second or one hundred and eighty to three hundred cubic feet per minute for each square foot of flue opening. In perpendicular flues, heated throughout with a smoke flue from the furnace, ten feet per second is attained.] or the ventilating pipe be itself conveyed through the center of the larger chimney flue. If the register for hot air be on the floor at one side of the room, two or more ventilators may be placed near the floor on the opposite side. The warm air will thus make the complete circuit of the room, and thoroughly warm it before passing out.

If the ventilating shaft be not heated artificially; the ventilator must be placed at the top of the room in order that the hot air may escape through it, thus producing an upward draught. But the objection to this method is that it allows the warmer air to escape, while economy requires that the cooler air at the bottom of the room should be removed and the warm air be made to descend, thus securing uniformity of temperature.

4. In the summer, ventilation may be commonly provided for by opening windows _at the top and the bottom_, on the sheltered side of the building, so as to avoid draughts of air injurious to the occupants. On a dull, still, hot day, when there is little difference of temperature between the inner and the outer air, ventilation can be secured only by having a fire provided in the ventilating shaft; this, by exhausting the air from the room, will cause a fresh current to pour in through the open windows. At recess, all the children should, if the weather permit, be sent out of doors, to allow their clothing to be exposed to the purifying influence of the open air; meantime, the windows should be thrown wide open, that the room may be thoroughly ventilated during their absence. In bad weather, rapid marching or calisthenic exercises will furnish exercise, and also permit the airing of the room.

5. The school and the church are the centers for spreading contagious diseases. The former offers especially dangerous facilities for scattering disease germs. Great pains, therefore, should be taken to exclude pupils attacked by or recovering from diphtheria, scarlet fever, whooping cough, etc., and even those who live in houses where such sickness exists.

6. In our houses [Footnote: The air of our homes is often contaminated by decaying vegetables and other filth in the cellar; by bad air drawn up from the soil into the cellar, by the powerful draughts that our fires create; by defective gas and waste pipes that let the foul air from cesspool or sewer spread through the house; and by piles of refuse, or puddles of slops emptied at the back door. Too often, also, the water in our wells, or in the streams that supply our towns and cities, receives the drainage from outhouses and barnyards, and so introduces into our systems, in the liquid--and thus easily assimilated--form, the most dangerous poisons. The question of sanitary precautions is one that presses upon every observant mind, and demands constant and thoughtful attention. (See p. 305.)] open fireplaces are efficient ventilators, and they should never be closed for any cause. Fresh air admitted by a hot-air register and impure air passed out by a chimney, form a simple and thorough system. Our sleeping apartments demand especial care. As soon as the occupants leave the room, the bedclothes should be removed, and laid on the backs of chairs to air; the bed be shaken up; and the windows thrown open. In the summer, the windows may be closed before the sun is high; the house is then left filled with the cool morning air. In damp and cold weather, a fire should be lighted in sleeping apartments, particularly if used by children [Footnote: In winter, children should always be given a moderately warm, well-ventilated bedroom, with light, fleecy bed coverings. Says a recent English writer: "The loving care which prescribes for children a cold bedroom and a hot, sweltering bed is of the nature that kills. Buried in blankets, their delicate skins become overheated and relaxed, while they are irritated by perspiration; at the same time, the most delicate tissues of all, in the lungs, are dealing with air abnormally frigid. The poor little victims of combined ignorance and kindness thus toss and dream, feverish and troubled, under a mass of bedclothes, while the well-meaning mother, soothed by a bedroom fire, slumbers peacefully through this working out of the sad process of the 'survival of the fittest.'"] or delicate persons, to dry the bedclothing, and also to prevent a chill on the part of the occupants. It is not necessary to go shivering to bed in order to harden one's constitution.