It is said that diseases of the lungs are the cause of four-fifths of all indispositions, ill health, and actual disease among civilized people, and that, between the age of fifteen and twenty-five, almost one-half of the mortality is due to pulmonary tuberculosis.

This almost universal weakness of the lungs, as it may be styled, is a product of modern civilization, and is caused by our unhygienic mode of life. Too little importance is attached to physical development, and well-developed lungs can only be found in a well-developed chest; too little time is spent in outdoor exercise; and private houses, public conveyances, and public assembly rooms are not properly ventilated.

Good development of the chest and lungs, and thorough and systematic ventilation of the lungs, are essential to a strong heart, a vigorous circulation, and power of the tissues to resist disease.

The Mechanics of Circulation and Respiration.—In order to understand the mechanics of circulation and respiration, it is necessary to appreciate four fundamental facts—that the thorax is a distensible, air-tight cage; that it contains and is filled by the heart, lungs, and great blood-vessels; that the exchange of gases in the blood takes place in the lungs; and that, on the development of the chest and respiratory muscles, depend the development of the lungs and the force of the circulation.

The Thorax.—The chest or thorax is a cone-shaped, distensible cage, formed of bones, elastic cartilage, and muscles. The spinal column forms the fixed part of this living cage, and the ribs are attached to this in such a way as to allow of their being raised in inspiration, thus increasing the anteroposterior and the lateral diameters of the chest.

The thorax is converted into an air-tight cavity by means of muscles. The base is made up of one huge muscle, the diaphragm. This is attached at its border to the ribs and posteriorly to the backbone. It is the diaphragm which separates the cavity of the thorax from that of the abdomen. When the diaphragm is relaxed, it has a concavoconvex form, the convexity being directed toward the chest, and the heart and lungs rest directly on it, while the concave surface covers or rests on the liver.

The Circulatory Apparatus.—This consists of a central force and suction-pump, the heart, and a series of elastic tubes that grow smaller the further from the heart they are situated; they divide and subdivide, like the branches of a tree. The smallest arteries, called capillaries, from their hair-like size, are so minute that they only allow the passage of a single corpuscle at a time and their walls are transparent.

The heart is a somewhat cone-shaped organ, placed between the two lungs; it is situated more or less obliquely in the chest, immediately back of the breast-bone. Roughly speaking, the base of the heart corresponds to the right edge of the sternum, while the apex lies a little below and to the right of the left nipple.

The heart is divided into a right and left side. The left side forms the force pump, whose motive power is supplied by the contraction of its own muscle-fibers. The bright red blood, with its fresh supply of oxygen—hence its color—flows from the lungs into the left heart, which then contracts automatically and forces the blood into the arteries of the body.

The arteries consist of a series of elastic tubings; hence, the smaller the tubing, the greater the resistance which has to be overcome by the force of the heart’s beat, so that during violent exercise, when the contraction of the muscles causes a pressure on the minute arteries and capillaries situated in them, the more forcible must be the beat of the heart to overcome this additional resistance. Likewise, when the surface of the body is suddenly chilled, as by a plunge into cold water, all the vessels situated here contract, and, again, more work is thrown on the heart.

The three chief factors in the mechanics of the circulation are the force and frequency of the heart’s beat, the peripheral resistance, and the elasticity of the arterial walls. Any disturbance between these relations brings about abnormal conditions.

The average frequency of the heart’s beat, or the pulse, is 72 times a minute. It is increased by exercise; it is quicker in the standing than in the sitting posture. It is quickened by meals, and, on the whole, it is quicker in the evening than in the early morning hours. Independent of muscular exertion, it is quickened by great altitudes. It is said to be quicker in summer than in winter. Its rate is profoundly influenced by mental conditions.

The whole of the blood of the body passes through the heart in 32 beats—that is, in less than half a minute. The greatest part of this time is spent in the capillaries. There the tissues are obtaining their fresh supplies of food and discharging their waste matter into it.

The heart, great blood-vessels, and the lungs are placed in the air-tight cavity of the thorax, and are subjected to the pumping action of the respiratory movements. The inspiratory muscles elevate the ribs, at the same time that the diaphragm, by its contraction, pushes the contents of the abdomen downward. The cavity of the chest, so enlarged, causes the pressure around the heart and the great blood-vessels within the chest to be less than that on the blood-vessels outside the chest; hence, during each inspiration the venous blood is sucked back into the right side of the heart.

The tissues deprive the blood of its oxygen, so that which flows back to the heart in the veins is blue. The right heart then sends this blue blood to the lungs, that it may get rid of its carbonic acid, which is not only not needed, but is actually injurious to the body, and to receive a fresh supply of oxygen, which has been carried into the lungs in breathing.

The blood is the great medium of exchange between all parts of the body. It is, at the same time, the nourisher and the scavenger of all the tissues. After the food has been liquefied and converted into new substances in the digestive system it is poured into the blood. From the blood all the tissues draw material to renew their own worn-out parts and other material which they store up as latent force, which, when it unites with the oxygen of the blood, becomes active force, such as heat and motion.

The blood holds in suspension a vast number of minute cells or corpuscles; the red corpuscles give its color to the blood, and are the oxygen carriers, while the white are the phagocytes or the protective agents of the body against disease.

The blood constitutes about one-thirteenth of the body weight. Of this, one-fourth is distributed to the heart, lungs, and great blood-vessels, one-fourth to the liver, one-fourth to the skeletal muscles, and the remainder to other organs.

In order that the blood may be a satisfactory medium of exchange between all the tissues of the body two things are necessary—first, there must be through all parts of the body a flow of blood of a certain rapidity and general constancy; and, second, this flow must be susceptible of general and local modifications.

The lungs are the essential organs of respiration or ventilators of the body. They are two in number, separated from each other by the heart, are placed in a semi-distended state in the air-tight thorax, which we have seen they, together with the heart and great blood-vessels, completely fill. The lungs ultimately consist of air-cells, surrounded by dense plexuses of capillaries and nerves. The air-cells communicate with the exterior through the bronchial tubes, trachea, larynx, throat, and nose.

The larynx is the organ of voice. It is situated between the trachea and the base of the tongue, at the upper and back part of the neck, where it forms a considerable projection in the middle line, called Adam’s apple.

The trachea is a cylindric tube, which extends from the larynx downward about 4½ inches, when it divides into the right and left bronchial tubes. The bronchial tubes, on entering the lungs, divide and subdivide, until finally they terminate in a lobule which is composed of air-cells and intercellular passages.

In inspiration the cavity of the thorax is enlarged by an active contraction of the muscles, in consequence of which the pressure of air within the lungs becomes less than that of the air outside of the body, and this difference of pressure causes a rush of air through the trachea into the lungs, until an equilibrium of pressure is established between the outside air and that within the lungs. This constitutes inspiration. Upon the relaxation of the respiratory muscles, the elasticity of the chest-walls and lungs, aided perhaps, to some extent, by the contraction of certain muscles, causes the chest to return to its original size. In consequence of this, the pressure within the lungs now becomes greater than that outside, and the air rushes out of the trachea, until the equilibrium is once more established—expiration.

During quiet respiration all parts of the lungs are not equally expanded; it is chiefly the apices of the lungs, reaching up into the region of the neck, and the central parts of the lungs, which undergo the least change of volume. This lack of a thorough distention and aëration of every part of the lungs is a cause of weakness of the lungs as well as of the entire body, for it is precisely those parts of the lungs which are the least active that are most prone to become the seat of tuberculosis.

In forced inspiration the cavity of the thorax is increased from 2 to 3 inches, partly by the elevation of the ribs and partly by the descent of the diaphragm, due to the contraction of its muscular fibers. In contracting, the diaphragm presses upon the abdominal viscera, pushing them downward about 3 inches, so that a projection of the flaccid abdominal walls occurs. The movements of the diaphragm are less extensive in women than in men, which is believed to be due to the corsets and general manner of dress. A perfectly free mobility is necessary for change in the size of the chest and lungs, in which the respiratory movements take place from sixteen to twenty times a minute.

The amount of air entering and leaving the lungs varies greatly in ordinary and forced respiration, being often three times as much in the latter. The volume of air is determined by the spirometer. Mr. Hutchinson, who invented the spirometer, has defined the vital capacity of the lungs as that amount of air which can be expelled by the most forcible expiration, and so the measure of the individual’s respiratory power. The vital capacity varies according to a number of conditions, as age, sex, weight, but, most important of all, is the height. It has been found that between five and six feet the vital capacity increases eight cubic inches for each inch in height.

The vital importance of the rôle which oxygen plays in the health and life of the individual may be better understood from the facts that about 10,000 liters of air are breathed daily, which makes the amount of food and drink consumed daily seem almost infinitesimal, and, important as the quality of the food is, the quality of the air is much more so, and, finally, that one can live for some days without either food or drink, but dies in a few minutes if the supply of air is cut off.

Secretion of the Lungs.—Like the lips and mouth, the lungs are invested on their free inner surface by a delicate mucous membrane, which constantly secretes a clear viscous fluid, the mucus. The lungs, therefore, like the nose, are always moist, and just as the nose is cleared by blowing it, so the lungs are cleared by hawking or coughing. A sense of discomfort or a feeling of irritation of the windpipe induces a deep inspiration, followed by an explosive expiration, which quickly brings up the mucus, so that it can be expectorated. The only difference between the mucus of the lungs and that of other organs is that the former is mixed with air and has, therefore, a frothy appearance.

The secretion of the lungs naturally flows down and accumulates, until it is voluntarily brought up and expelled. Any one with a cold on the chest, or who is subject to catarrh, will notice that, on moving about in the morning in making the toilet, especially on raising the arms to dress the hair, expectoration is greatly facilitated, and that this is followed by a feeling of clearing out of the throat and lungs.

Because of the great aid given to the lungs in clearing them of mucus, moderate exercise in the open air is a much better treatment of an ordinary cold than a prolonged stay in bed. And for the same reason, in the treatment of lung troubles, so soon as the temperature of the patient is down to normal, and her strength makes it safe to allow her to move about, the recovery of the patient is hastened by getting up and moving about the house.

Hygiene of the Lungs and Its Relation to the General Health.—Two conditions are essential for the preservation of the health and prevention of diseases of the lungs—good chest and lung development, and a continuous supply of fresh air for the proper ventilation of the lungs.

Fully one-third of the whole volume of blood is always circulating in the lungs, and each corpuscle passes through them 8000 times in the twenty-four hours. In other words, the lungs are the vitualizing stations of the corpuscles which unceasingly go hurrying by. If these carbonic-acid-laden corpuscles arrive in the lungs, and do not find the requisite amount of oxygen awaiting them, they return to the tissues, carrying part of their carbonic acid back to them instead of a fresh supply of oxygen, and so the tissues are weakened instead of being nourished, while the corpuscles themselves suffer from lack of proper nourishment and deteriorate in form and color. Imperfect ventilation of the lungs is the most frequent cause of anemia or thinness of the blood.

It must not be overlooked that the air may be fresh and pure, and yet not able to penetrate all parts of the lungs because of superficial and improper breathing.

Relation of Respiration to Body Heat.—The heat of the body is generated by the oxidation of the tissues. The chilliness experienced by persons engaged in sedentary occupations is by no means always caused by the low temperature of the room, as will be proved by the thermometer, but by the close air of the room and superficial respiration, which causes internal overheating with imperfect combustion. The correctness of this statement may be proved if the woman will throw the windows wide open and take deep breathing exercises for five minutes. She will then go back to her work thoroughly comfortable. In other words, she has breathed herself warm.

The Respiratory Function of the Abdominal Muscles.—Well-developed abdominal muscles play an important part in expiration, hence, in emptying the lungs of their impurities. Under normal conditions the pressure in the abdominal cavity is greater than that of the atmosphere; hence in the elastic recoil following inspiration, the abdominal viscera constitute a buffer, so to speak, and drive the diaphragm upward.

The chief causes of flabby abdominal muscles, with its consequent low intra-abdominal pressure, are a sedentary life, the wearing of corsets which prevent the free play of the abdominal muscles, and the overdistention of the abdominal walls by repeated pregnancies and by the accumulations of fat.

As a result of lax abdominal walls, there is very frequently an enteroptosis or a falling of the abdominal contents far below their normal position; this includes the liver, spleen, pancreas, the intestines and stomach, and is the most frequent cause of floating kidney.

Further, the accelerating influence of the diaphragmatic movements on the circulation is seriously interfered with.

The Importance of Good Chest Development.—The least chest development of the adult woman—that is, the underarm girth around the chest—consistent with good health is 28 inches, and this girth must be enlarged 3 inches on forced inspiration. In ordinary respiration the waist expansion should be from ½ to 1 inch, while during muscular activity it should be from 1½ to 3 or 4 inches.

In women the movements of the upper part of the chest are very conspicuous, the breast rising and falling with every respiration; whereas, in children and in men the movements are almost wholly confined to the lower part of the chest, and are called diaphragmatic, in contradistinction to those seen in women, which are called thoracic. It is now the opinion of many observers in this country and in Europe that the habit of thoracic breathing in women has been brought about by constricting the waist and the lower ribs. Observations made among the Indians and Chinese women show that the abdominal is there the type of breathing, and civilized women who wore no corset had relatively good abdominal breathing. Further, that a thoracic type of breathing can be produced in man by putting him in a corset.

Vital capacity is, as we have seen, the term employed to denote the amount of air that can be expired after the fullest possible inspiration. The amount for persons 5 feet in height has been estimated as 174 cubic inches, with an increase of 8 cubic inches for every inch in height above this. The relation between height and vital capacity is rather remarkable, since height is chiefly determined by the length of the legs, and not by the size of the trunk and thorax. This is due to the fact that mobility of the chest increases with stature.

The capacity of the chest is determined by the spirometer. A person who can only blow, say from 180 to 250 cubic inches, has a good pair of lungs, while, on the other hand, an ability to blow only 100, even where percussion and auscultation had revealed nothing, is suspicious.

One test by the spirometer is not sufficient to judge of the condition of the lungs, since the woman may be nervous or may not understand how to breathe into it, so that a number of tests should be made on different days, which may give a much better result, though no change has occurred in the lungs.

Proper relation between the height, weight, and chest measurement:

The Chemical Properties of Air.—It is of more vital importance that the air which we breathe should be pure than the food which we eat should be, although the latter is universally conceded to be a matter of prime importance. The reason is that the poisons in the air, inspired by the lungs, pass directly into the blood, whereas, taken into the stomach, the action is much slower, and there is at least the possibility of their passing through the digestive tract unassimilated.

The olfactory nerves are the normal guides as to the purity of the air, and, if they have not been dulled by long usage in breathing impure air, they are extremely sensitive to impurities in the atmosphere.

Country Air.—In the open air there is a constant, even though insensible, movement of the currents of air; the result is a constant renewal or ventilation of the air. There is, in addition, the evaporation from brooks, rivers, lakes, the dew and rain, which aid in cleansing the air from dust; the peculiar freshness of the air in the country after a heavy fall of rain is familiar to all.

The “bouquet” of the air, most noticeable and delightful in the early morning, especially in the spring of the year, is due to the fragrance given off from the flowers, plants, and trees, and imparts a feeling of exhilaration and a sense of the joy of living.

Sunshine increases the respiratory movements.

Wind clears the air of impurities, and is only harmful when it carries dust with it, or when it is so strong that it impedes the respiration or bodily movements. Very weak persons get out of breath easily when battling against the wind.

Town Air.—Even the outdoor air of towns has its full quota of oxygen,—21 per cent.,—and so is healthier than indoor air. The carbonic acid in the air varies from 0.2 to 0.6 per cent. Among the impurities of the air are smoke, fog, and dust.

Dust and Its Relation to Disease.—Dust, consisting of particles of all kinds of organic and inorganic matter, is a nuisance of indoor as well as outdoor life. That the dust in cities is the intolerable nuisance and menace to public health that it is, is due to the filthy condition of the streets.

The specific cause of tuberculosis is the tubercle bacillus. Considering the prevalence of the custom of spitting on the pavements, streets, floors of public conveyances, and public halls, that the dust from the streets is carried into the houses on the shoes and the trailing skirts of women, it is self-evident that anything which stirs up the dust, as sweeping, stamping on the floor with the feet, dancing, and on the streets strong currents of air and high winds are a most serious menace to the health and lives of the community.

In addition to the fact that dust is the great carrier of the tubercle bacillus, the particles of dust cause a direct irritation of the mucous membranes lining the nose, throat, larynx, and bronchial tubes.

That dust is an important factor in the causation of colds may be inferred from the facts that they are more common in the city than in the country, and that in the city they are more frequent in the spring and fall, when the streets are not watered.

The Rôle Played by Bacteria.—Bacteria are distributed nearly everywhere and in larger quantities than is generally believed. The air in open spaces in cities contains from 100 to 1000 bacteria per cubic meter, while the air of an inhabited room contains from 6000 to 10,000.

It can now be definitely stated that microörganisms are the immediate or exciting cause of bronchitis observed in diphtheria, in influenza, measles, whooping-cough, pneumonia, etc. These microörganisms are conveyed both directly from the sick to the well, and from the inhalations of the germs floating in the atmosphere. Whenever dust is raised, we breathe in a great number of microörganisms.

In influenza the bacilli are found in the secretions of the nose, throat, and in the expectorations from the lungs.

The bacilli are not only the cause of the acute infections, but also of chronic bronchitis.

The bacterial flora usually present in the throat and the respiratory passages is rich and varied. So long as the mucous membrane lining these passages remains in a healthy condition, an unfavorable condition is offered for their growth and development and these microörganisms are harmless. But just so soon as the general vitality is lowered, or there is an impairment of the normal condition of the epithelium lining the respiratory tract, a culture-medium is provided in which these germs flourish and grow. Anything which will cause an irritation or congestion of the mucous membrane of the throat and bronchial tubes furnishes the necessary conditions for the infection to take place. The germs themselves excite an acute inflammation, and the inflammation extends from the head or throat to the bronchial tubes, through the spread of the infective agent along the respiratory tract.

Ventilation.—Very few people in cities spend more than one hour a day in the open air, which means that they are housed up for the other twenty-three hours, so that no pains should be spared to bring up the quality of the indoor air to approximate as nearly as possible that of the outdoor air. The air of houses contains many more microbes than that of the street.

For dwelling-houses 3000 cubic feet of fresh air is needed every hour. It is said that in the country the only bad air is in farmers’ houses, whence it has no chance to escape.

Direct sunlight kills the tubercle bacillus in thin layers of sputum in five or six hours, and diffused sunlight in several days, and proper ventilation greatly facilitates this bactericidal action. A large cubic space is of little avail if the ventilation is inadequate. The windows should be at least one-seventh of the floor space.

The air of the house must be fresh, pure, and cool, to allow proper ventilation of the lungs and skin. Colds are prevalent in winter, because that is the season when people are housed up and breathe impure air.

The commonest causes of impurities of the air in houses are the expired air and the transudation of the skin; the production of the combustion of lights or unconsumed gas may come from the burner when lit, if the pressure is very strong, or the rubber fittings may retain the gas; tobacco smoke; the effluvia of simple uncleanliness of rooms and persons; and the products of the fluid or solid excreta retained in the room. In addition, there may be special conditions which allow the impure air to flow into the room, as from the basement or cellar of a house, from imperfectly trapped soil and waste-pipes, or from other impurities outside of the house.

In respiration the air is vitiated by a decrease in the amount of oxygen and an increase in the amount of carbonic acid; the expired air contains about 4 or 5 per cent. less oxygen and about that amount more of carbonic acid than the inspired air. It has been estimated that an individual takes into her lungs about 500 cubic inches of air per minute and exhales the same amount of vitiated air. The expired air is of a higher temperature, and is loaded with aqueous vapor. The organic substances present in expired air are in part the causes of the odor of the breath; it is probable that many of them are of a poisonous nature. The air is still further vitiated by the products of decomposition of persons having decayed teeth, nasal catarrh, and disorders of the digestive systems, as well as by personal emanations.

When the sensibilities of the sense of smell become dulled, they give no warning of the sense of danger, and the individual may not feel conscious of the harm, although the nervous centers may be greatly depressed, and, because discomfort has not been experienced in a vitiated atmosphere, it does not follow that harm has not been done. The effects are slowly and imperceptibly cumulative, but are on this account none the less injurious, and are now recognized as being among the most potent and wide-spread of all the predisposing causes of disease.

The physiologic effects of breathing vitiated air are that, owing to the impurities of the air, the respirations become quicker and shallower, the heart’s action more rapid and feeble; there is a more or less irritation of the mucous membranes lining the nose, throat, and larynx. In extreme cases, where many people are crowded together and the ventilation is totally inadequate, the air often becomes so impure as to cause headache, lassitude, nausea, and fainting.

The long-continued action of such impurities on the olfactory nerves may ultimately induce, through the central nervous system, alterations in the respiration, circulation, and nutrition. When moderately vitiated air is breathed more or less continuously, the individual becomes pale and loses her appetite; after a time there is a decline in the muscular strength and animal spirits. The aëration and nutrition of the blood is interfered with, and the general tone of the system falls below par.

It has further been maintained that metabolism is hindered by much-breathed atmosphere. In addition to the ordinary symptoms of discomfort, the long occupancy of so-called stuffy rooms so lowers the resistance as to be conducive to the contraction of colds and even to more serious infections.

People in this lowered condition of health, which is very common among those who spend the greater part of the day indoors, in offices, houses, schools, factories, and workrooms, offer much less resistance to attacks of acute diseases than do people who lead an outdoor life.

In considering the ventilation of a house, the purity of the air, the temperature, and the dryness of the air must all be considered.

The test now generally accepted as the standard of purity of the air is not the chemical one of the estimation of the amount of carbonic acid contained in the air of a closed space, but that, on entering a room or closed space from the outside fresh air, no sense of impurity or closeness should be noticeable.

The so-called natural ventilation of houses, which takes place through the porosity of the walls, the cracks around the doors and windows, is generally too inconsiderable to be taken into account.

Where houses are heated by furnaces, a certain amount of ventilation is furnished by this means, but the air is by no means so pure as the air of a house heated by hot air or steam pipes. In the latter case, the greatest drawback is the dryness of the air.

As the air contained in an inhabited room cannot be kept as pure as the outside air, the object of ventilation is, by the admission of the pure external air, so to minimize the impurities that the air respired may not be detrimental to health.

The most effective means for the ventilation of houses and apartments is the throwing wide open all doors and windows; the windows must be opened at both top and bottom, as the hot impure air rises and the cold air falls to the floor. The length of time which the house should be left open will depend on the outside temperature and the velocity of the winds. This ventilation of the entire house should be carried out three times a day—in the early morning, at noon, and again in the evening.

In addition to this, provision should be made for a constant access of fresh air to the room. A simple and rather primitive method is by raising the lower sash by a strip of wood several inches in height and the exact width of the window. The air will then enter the space between the upper and lower sashes. Some such or any better method of ventilation should be in continuous use, day and night, when the room is occupied. So soon as the weather is sufficiently mild, some of the windows should be left open all the time.

When the air of a room is fresh and pure, the human system is furnished with all the oxygen it can consume, and heat is thus introduced into the body, so that a lower external temperature is necessary for comfort. Hence, supplying a sufficient quantity of fresh air minimizes the amount of coal consumed, besides increasing the vigor of the body.

The temperature of the house will depend on the occupation, age, and health of the inhabitants. With a sedentary occupation, a temperature of from 64° to 70° F. is the most suitable. The temperature of the bedroom at night should not be allowed to fall below 50° F. Every room in the house should be furnished with a thermometer.

The Injurious Effects of Overheated Air.—A rise of temperature in the surrounding air diminishes the amount of oxygen consumed and the amount of carbon dioxid discharged; a fall of temperature has the opposite effect. In addition, this overheated air forms a hot jacket about the body, which prevents the radiation of heat necessary to keep the body in a healthy condition.

For the same reason, when out-of-doors, furs should not be worn close up around the neck, and fur coats should only be worn in the extremely cold weather. Paper and rubber worn about the body act in the same way, by preventing the radiation of heat and moisture—practically steam jackets are formed; the skin is rendered very sensitive and susceptible of chilling on the slightest fall of temperature.

The Proper Degree of Moisture of the Air of the House.—The air below the freezing-point is deprived of much of its moisture; brought into the house, and raised from 70° to 80° F., or drawn into the nostrils and raised to 98° F., it must take up its quota of moisture. This moisture must, therefore, be provided in the air of the house. In the case of houses heated by furnaces, some moisture is furnished by the water-pans of the furnace; but in the case of heating by hot air and steam pipes, there is less circulation of air, the air is very much drier, and generally of a very much higher temperature. A satisfactory method of furnishing these houses with the proper degree of moisture has not yet been invented.

One is only comfortable in a dry air when it is of a low temperature. When the dry air becomes heated, there is more moisture given off by the mucous membranes, which causes a feeling of dryness and irritation in the nose, throat, and larynx; there may also be a sensation of uneasiness of the chest, and, at the same time, the individual feels chilly.

Persons constantly breathing abnormally dry air lower the resisting power of the respiratory mucous membranes and become very susceptible of taking cold.

Since the degree of moisture of the air of a house is equally important as its temperature, every room should be furnished with a hygrometer, which should register from 65 to 70 per cent. of moisture.

The Ventilation of Bed-rooms.—The importance of the proper ventilation of the sleeping-room will be seen from the fact that two-thirds of the oxygen absorbed in the twenty-four hours is absorbed between 6 o’clock in the evening and 6 o’clock in the morning; and on the state of the air of the bed-room will depend greatly the vitality of the individual. During sleep inspiration occupies ten-twelfths of the respiratory period, while at other times it occupies only five-twelfths of that period. In a closed room the oxygen would eventually be consumed, the air become filled with impurities, and the body languish for want of oxygen and incapacity to throw off its impurities.

The air of the room should be perfectly fresh on retiring; where it has been used as a sitting-room, it should be thrown wide open and thoroughly ventilated just before going to bed. The temperature of the room should not be above 65° F. In the bed-room at night all the air coming into the room should come from the same side of the room, and the doors opposite should be closed. If the room is small, and the window is at the head or foot of the bed, some provision must be made to screen the bed, and to allow the air to enter the room without falling directly on the sleeper.

In the intense heat of summer, especially if the air is saturated with moisture, one sleeps much more comfortably on the side, with the face almost at the edge of the bed; in this way the formation of a stagnant pool of exhaled air about the face is prevented, which would otherwise be rebreathed, and greatly increase the feeling of discomfort and malaise.

On retiring at night the clothes worn during the day should be spread out over chairs to become thoroughly ventilated, instead of being hung up in a closed press or closet. From a sanitary point of view, it is essential that every article of clothing worn during the day should be removed at night. Both clothes and body need ventilation.

In the morning the clothes should all be taken off the bed, and they, as well as the night-clothes, should be spread out to be aired during the ventilation of the room. The windows are thrown wide open when one goes to breakfast.

The Care of the Nose, Throat, and Ears.—It will be most profitable to consider the care of the nose, throat, and ears together, since the mucous membrane lining these cavities is continuous, and so there is always great danger of an inflammation of one extending to the others.

It has been calculated that about one-third of our adult population are notably deaf in one or both ears. In the majority of cases deafness is the result of colds and throat troubles, and much can be done to prevent its occurrence.

The nose communicates through the nasal fossæ with the nasopharynx, and the mucous membrane lining the nose is continuous with that lining the throat.

The nose performs four important functions—it serves as a passageway for the air in breathing, and it warms, moistens, and filters the inspired air; it is the organ of smell; it aids in phonation; and it affords ventilation to the ears and accessory sinuses. But by far its most important function is the rôle which the nose plays in respiration. To supply the large amount of water necessary to moisten the inspired air, it has been calculated that about one pint of water must be secreted by the nose daily; part of this amount of moisture is furnished by the tears. Mouth-breathing always causes dryness of the throat.

The filtration of the air is accomplished first through the action of the hairs at the external margin of the nose, which hinder the entrance of large particles, and, second, by the adherence of small particles to the moist surface of the intricate passages of the nose and nasopharynx. The microbes are expelled with the dust; in addition to this, the nose probably has the power of destroying any bacteria through the action of its germicidal mucus.

Obstruction of the Nasal Passages.—In adults the commonest modes of obstruction are the bending of the nasal septum to one side, or by a thickening of the septum by which one nostril may be completely closed up. The occlusion may also be due to the swelling of the mucous membrane or the presence of polypi.

In children the most common form of obstruction of the nose is by the adenoids and the enlargement of the tonsils; this enlargement may be so great as to prevent nasal breathing and interfere with the normal ventilation of the ears.

The Throat or Pharynx.—The throat or pharynx is the upper and funnel-like portion of the alimentary canal, which is seen at the back part of the mouth. It extends up back of the nose. The cavity of the throat is somewhat separated from that of the mouth by the soft palate. This is a membranous curtain, which is attached to the posterior part of the hard palate. The pendulous part of the soft palate is known as the uvula. The uvula sometimes becomes so greatly relaxed that it rests on the base of the tongue, which causes a constant irritation and slight cough, a condition which is easily relieved by a few astringent applications.

On looking into a mirror there will be seen, on either side of the throat, two arches, formed by folds of mucous membrane; these are known as the pillars of the throat. Between these pillars, on either side, is an almond-shaped body called the tonsil. In health the tonsil should not protrude beyond the anterior pillar.

Causes of Diseases of the Nose and Throat.—Exposure to wet and cold, when insufficiently clad, or, even worse, sitting still with damp skirts or shoes on. A still more potent factor than exposure to cold is the relative degree of humidity of the atmosphere; great humidity is frequently accompanied by epidemics of influenza. Exposure to very high winds; sudden changes of temperature; the very dry air and the overheating of houses; insufficient covering at night; the inhalation of irritating vapors and finely divided mechanical irritants. Also, gastro-intestinal affections and uric acid.

Chronic enlargement of the tonsils predisposes to tonsillitis and to all the infective and contagious throat diseases. In addition, the breath is apt to be fetid, and swallowing the mucus, germs, and toxins has a deleterious effect on the stomach and general health. Mouth-breathing and anemia often follow, and there is an increased liability to inflammation of the eyes.

The Importance of a Healthy Condition of the Throat and Nose.—The nose and throat are the portals of entrance to the bronchial tubes and lungs, and it depends on the condition of their mucous membranes whether the germs of disease will find lodgment here and be carried down into the bronchial tubes and lungs, or whether they will be expelled with the mucus.

Any irritant which destroys the vitality of the epithelium covering the mucosa, or a local congestion which interferes with the nutrition, circulation, and secretions of the part, offers favorable conditions for the culture of bacteria normally present. Also, anything which will cause a lowering of the general health, and thereby lessen tissue resistance, acts as a predisposing cause to local inflammation, while the germs themselves excite inflammation by their active growth in loco.

From these facts will also be seen the importance of having cut short, as rapidly as possible, any congestion or inflammatory troubles of the nose and throat.

Prevention of Nasal Catarrh and Sore Throat.—First in importance comes attention to the general health. Under this must be considered the clothing, food, ventilation, and exercise.

The clothing should be light, yet sufficiently warm to be a protection against the cold and winds. Heavy shoes with thick soles are necessary to protect the feet, and it is not so much the matter of getting wet as it is of sitting down with damp clothing on.

An atmosphere filled with dust in sweeping should not be tolerated in any well-kept house.

Local Treatment for the Prevention and Cure of Mild Cases of Nasal Catarrh and Sore Throat.—The treatment is practically the same. The toilet of the nose and throat should be made at least as often, and at the same time, as that of the teeth; certainly, the first thing on getting up in the morning and again before dressing for dinner. In our seaboard cities and towns, at least, there is a very general predisposition to some degree of congestion of the mucous membrane of the nose and throat. This means an abnormal amount of mucus which collects in the parts during sleep. Again, on coming in from out-of-doors on a windy day a large amount of dust, which means microbes as well, has become lodged in the mucous membranes of the nose and throat.

This toilet of the nose and throat is best carried out by means of a nasal spray. The spray apparatus consists of a bottle holding some two ounces, a hard-rubber spray piece, and a bulb with tubing to force the liquid through the spray piece. The tip of the spray should have the form of a cone; this should be introduced into each nostril, the bulb squeezed several times, until the amount of fluid is sufficient to be hawked out, and this process is facilitated by holding the mouth open during the spraying of the nostrils. After the nostrils have been thoroughly cleansed, the throat should be sprayed directly.

The liquids used must be bland and unirritating, and only enough should be used at one time to cleanse the parts. There are on the market excellent alkaline and antiseptic tablets; one tablet should be dissolved in a spray-bottle not quite full of water. This solution keeps in perfect condition, and is always ready for use.

A solution of boric acid, in the proportion of two teaspoonfuls of boric acid to one pint of water, may also be used.

If the nose and throat are inflamed, this so-called water spray should be followed by an oil spray, which will be found to be most soothing and healing. A separate apparatus for this will be necessary, as an oily solution would clog an ordinary water-spray, but the principle of the spray is the same, and it is used in the same way. The following is an excellent formula: Take of menthol and carbolic acid each two grains; of eucalyptol, six drops; and of albolene, two ounces. Mix well, and fill the spray-bottle one-third full; it is to be used in the full strength. Use only enough of this spray to moisten the nose and throat; by inhaling simultaneously with squeezing the bulb, the very fine spray is carried into the larynx, and so is very useful when there is an irritation of that organ, as shown by hoarseness. If there is only a slight irritation of the parts, the use of the spray twice daily will be sufficient; the last time should be just before retiring. On windy days it will be a great protection to the mucous membrane of the throat to use it just before going out-of-doors, on the throat only. If the inflammation is severe, the spray may be used as often as every two hours. This prescription should be put up by a good druggist.

Ear specialists condemn all nasal douches as dangerous, on account of the possibility of the water being forced into the Eustachian tubes.

General Treatment.—First of all, the system must be toned up by the systematic use of cold baths, adapted to each particular case, tonics, iron, and cod-liver oil. It is a grave mistake to allow these cases to become chronic, as they may be the forerunners of influenza and even general tuberculosis. They need prompt and scientific treatment, which the physician alone is capable of giving.

The Ear.—The ear is divided into three parts—the external ear, the middle ear or tympanum, and the internal ear or labyrinth. The internal ear is the essential part of the organ of hearing in which the auditory nerve ends. Its structure is very complicated. The external ear is separated from the middle ear by the tympanic membrane or drumhead. This is a thin, small, membranous sheet, which is stretched tautly across the junction of these two cavities, and vibrates inward and outward between them. The external ear collects and conducts the waves of sound to the tympanum.

The middle ear, or tympanum, is an irregular cavity, situated within the bone. It is traversed by a chain of movable bones, which connect the drumhead with the internal ear, and serves to convey vibrations of sound to it. The middle ear, or drum cavity, is filled with air, and communicates with the pharynx by means of the Eustachian tube. The middle ear is lined throughout with mucous membrane, which is continuous with that of the throat and nose.

The Eustachian tube is continuous with the middle ear, and extends downward and forward about an inch to connect it with the pharynx, where it opens by a trumpet-like expansion, just above the soft palate, at the junction of the throat and nose. It serves to carry off the excess of fluid from the middle ear and to preserve the equilibrium of the pressure between the gaseous contents of this cavity and the atmosphere. The walls of the Eustachian tube are in close contact, but they are normally opened during every act of swallowing, yawning, etc., when the air finds its way into the middle ear. A stoppage of the nose reverses the process, and when the tubes are not likewise stopped up, every swallowing motion draws air out of the tubes. If the openings of the tubes become closed, deafness, dizziness, and subjective noises will result.

The middle ear is the seat of about two-thirds of all aural troubles, and, since much of this could be prevented, this becomes a matter of great practical importance.

Causes of Impairment of Hearing.—The majority of the affections of the middle ear originate from extensions of catarrhal inflammations, from the nose and throat, through the Eustachian tubes. In children adenoids are the most frequent cause of deafness. The so-called hereditary deafness is probably due to an inherited configuration of the septum of the nose, a bending of the septum to one side, or a tendency to catarrhal affections of its mucous membranes.

Every cold in the head tends to mechanically involve the ears, and, while recovery may seem complete, there is likely to be some unrelieved trouble which insidiously but steadily increases—first one ear, and then the other, shows signs of defective hearing. If only one ear is involved, the condition may progress seriously before the patient is aware of the trouble.

Preventive Measures Against Deafness.—From what has been said, it naturally follows that the preventive measures must be chiefly those already given against taking cold. If one does take cold, instead of leaving it to run its course, as is too often done, proper therapeutic measures should be at once adopted to bring as speedy a cure as possible.

Impacted Ear-wax and its Removal.—A healthy ear should never show more than enough wax to render the hairs within soft, and the individual should be unconscious of the wax coming away. Wax does not collect in a healthy ear. When it does occur, there is a stopped-up feeling in the ears, due to the occlusion of the meatus by wax.

The only procedure that is safe to follow in order to remove the wax from the ear is to gently douche the ear with warm water, at a temperature from 105° to 110° F. If this does not suffice, a physician must be consulted, as all efforts to remove the wax after it has become impacted are dangerous and futile except in skilled hands.

Earache.—The best thing for the relief of earache is the external application of heat by means of a hot-water bag. If this does not give relief, the ear may be douched with warm water. Earache can often be prevented, by those subject to it, by placing a very small piece of absorbent cotton in the ear before going out in very high winds or in automobiling.

Impediments to Normal Respiration.—These are, for the most part, acquired through improper habits of posture, dress, lack of muscular and chest development. Other impediments to respiration are a deviation of the septum of the nose to one side, marked curvature of the spine, and deformities of the chest which may be the results of rickets.

Curvature of the spine is frequently the result of muscular weakness, combined with faulty position at the desk.

The clothing must be sufficiently loose to admit of the fullest possible chest expansion; the measurements for the clothing, and most especially for corsets, must be taken during full chest expansion.

Heavy clothing suspended from the shoulders is also hurtful, because it renders impossible the expansion of the apices of the lungs. Obviously, all tight bands around the neck interfere with the respiratory movements.

Bodily position plays a very important part in maintaining the symmetric development of the chest and in the proper ventilation of the lungs; and this is a matter of the greatest importance to students, clerks, and writers who spend a great part of every day at the desk.

The faulty attitude, together with the weak muscles and the poor muscular development, are fruitful sources of spinal curvatures and flat chests; and free respiration is interfered with. Writing with a pen is most apt to be accompanied by a peculiarly cramped position of the body, rendering normal respiration impossible.

The Correct Attitude at the Desk.—The chair should be of such a height that the woman may rest her feet firmly and easily on the floor or upon a foot-rest, the seat being deep enough from before backward to accommodate about three-fourths of the length of the thighs, while the back of the chair should be so curved as to support the spine easily in its natural curves, both at the waist and at the level of the shoulder-blades.

The chair and desk should be sufficiently close together so that the student may sit erect to read from books, since leaning forward at the desk causes round shoulders, flat chest, and short-sightedness. When the desk and chair are properly arranged, two-thirds of the forearm can be rested upon the desk without raising the shoulders.

In reading, the distance of the book from the eyes should be twelve inches, and the book-rest should be inclined, sloping downward toward the reader, at about an angle of 85 degrees.

If the woman has any great amount of writing to do, she should learn to use a typewriter. In using this machine she not only writes very much more rapidly and easily, but the position of the body is much more erect than that assumed when using the pen, and it is not nearly so fatiguing to the muscles of the hands and arms.

All closely confining sedentary occupations, as writing, sewing, etc., should be frequently interrupted to move about for a few minutes, rest the eyes, and take a few deep breathing exercises before an open window; this is necessary for the eyes as well as for the ventilation of the lungs.

Ventilation of the Lungs and Breathing Exercises.—Forced respiration is essential to completely change the air in the lungs, to maintain the elasticity of the lung tissue, and to expand the chest in every direction. Only in this way can a thorough ventilation of the lungs take place; a full supply of oxygen is taken in, which stirs up, disinfects, and cools the stagnant residual air, and forced expiration expels the respiratory excretions. One of the frequent causes of foul breath is lack of ventilation of the lungs, so that the expired air becomes laden with impurities.

In normal breathing the current of air which passes in and out of the lungs travels through the nose, not the mouth. The ingoing air, by exposure to the vascular mucous membrane of the narrow and winding nasal passages, is warmed and moistened, and at the same time the mouth is protected from the desiccating effects of the continual inroad of comparatively dry air.

By means of respiratory exercises the mobility of the chest may be greatly augmented; there is an increased flexibility of the ribs and sternum, as well as loosening of the thoracic joints, which may have become stiff, and these exercises also lead to a development of the respiratory muscles.

In this manner only can the frame work of the chest become thoroughly inflated from within, and thus all parts of the lungs, which run the risk of becoming incapacitated from lack of use, be brought into play.

It is highly important that this thorough ventilation of the lungs should take place at least three times a day—the first thing in the morning, while making the toilet, again about the middle of the day, and at night just before retiring.

To obtain the greatest benefit from these exercises they must be taken without corsets, the clothing must be light and loose, and the body lightly clad. The air in the room must be fresh, and after they have been learned, they can, as a rule, be taken before an open window. In the morning they are best taken just after the cold bath, when, by removing the impurities and filling the lungs with fresh air, and at the same time starting up a good vigorous circulation, they cause one to begin the day with energy and zest.

The respiratory movements are diminished during sleep, and at the same time there is a large accumulation of blood in the splanchnic veins, so that, particularly when there is any tendency to difficulty with the breathing at night, the trouble is greatly lessened by filling the lungs with pure air just before retiring.

It is necessary, first of all, to learn the art of breathing, to be able to dissociate the clavicular, the costal, and the diaphragmatic. By clavicular breathing is meant the raising of the collar-bone and shoulders as high as possible by means of a slow but deep inspiration—this expands the apices of the lungs; costal breathing is the throwing out and expanding the chest to its utmost capacity, and so enlarging the chest in its transverse and anteroposterior diameters; diaphragmatic breathing is the depression of the diaphragm and the protrusion of the abdomen without raising the lower ribs. The last is the most readily learned in the supine position; the bed supports the weight of the body, so that the individual is able to concentrate her entire attention on fixing the bony thorax, depressing the diaphragm, and protruding the abdomen at every inspiration and retracting it to the utmost with every expiration. This, of course, develops and gives tone to the abdominal muscles.

When the woman has conquered these first principles of respiration, she is ready to put them into practice in the standing posture. They should be learned before a mirror, and after that taken before an open window. The hands should be placed on the hips; first elevating the collar-bones and the shoulders to the utmost, while still holding the breath, she expands the chest, always breathing in from above downward, and, lastly, the diaphragm is depressed. With the lungs thus expanded to their utmost capacity, the breath is held as long as possible, then the lungs are emptied by an abrupt and forced expiration.

These exercises should be repeated at first ten times, gradually increasing to thirty times. It is well to take one or two ordinary respirations between the forced ones.

It will be found that, as these exercises proceed and the lungs are filled with purer air, the breath can be held for a longer period of time, and that with practice the length of time that the breath can be held is greatly increased; it should be held for half a minute. Public speakers, singers, and divers are all skilful in this respect.

When these simple breathing exercises have been mastered, breathing exercises can be combined with other exercises, which have as their aim the development of the muscles of the chest.

Reading aloud, singing, talking, laughing, are all good exercises for developing the capacity of the lungs.

The Cure of Chronic Bronchitis by Deep-breathing Exercises.—The upper part of the body must be nude and the exercises taken before a mirror, so that the woman can watch the movements of the chest and abdomen, see that all the hollows of the chest are filled out during forced inspiration, and that the muscles of the abdomen are properly retracted. For the average woman this last will be the most difficult; in beginning these exercises she will find that it will require all her concentrated energy and will power to cause a retraction of these disused muscles.

Patients with chronic bronchitis do not have the ability to perform forced respiration properly. The respirations are too superficial, and the respiratory movements are not properly performed.

As respiration is ordinarily performed, the partial expansion of the upper part of the chest is accompanied by a contraction of the abdominal muscles, whereby the diaphragm is forced upward, with the result that the lower part of the lungs remains very slightly expanded, whereby the circulation as well as the removal of mucus is imperfectly performed. This lack of forced respiration is a frequent cause of acute bronchitis running into a chronic form.

In chronic bronchitis it is especially in the lower part of the lungs that stagnation of the secretions takes place, and they can only be dislodged from the mucous membrane by forced abdominal expiration and the ascent of the diaphragm. This causes a cough which expels the mucus, and forcible abdominal expiration and cough are the only means of drainage of the lower and deep-seated parts of the lungs. Further, in forced respiration the muscle tissue of the bronchial tubes contracts, which certainly does not take place in ordinary respiration, but, on the contrary, this tissue atrophies.

Other beneficial results from forced respiration are increased oxygenation, improved nutrition, changes of a mechanical nature, ventilation, and disinfection of the lungs, massage of the lungs and pleura, and drainage.

No other method of treatment is so successful in the cure of chronic bronchitis not dependent on disease of the nose and throat. In from two to six weeks of treatment, in which there is a profuse discharge of mucus, it will be found that the bronchial tubes have cleared up, provided that the patient is supplied with an abundant supply of fresh air day and night. Methodically practised, deep breathing is not only the surest cure, but also the safest stimulating expectorant.

Relation of Colds and Influenza to Pneumonia and Tuberculosis and their Prevention.—We have already seen that bacilli are not only the cause of acute infections, but also of chronic bronchitis, and that this was especially true of the bacillus of influenza and the pneumococcus of pneumonia.

It is well known that influenza is an infectious disease, which rapidly spreads through the family and the community, but it is not so well known that the so-called “common colds,” ordinary sore throat, and tonsillitis are also highly contagious. The infection is carried from one person to another by direct contagion; the air is being constantly sprayed with the germs of disease in talking, laughing, sneezing, and coughing. In coughing and sneezing it is not sufficient to hold the hand before the mouth—a handkerchief must be used for this purpose.

Colds are among the most frequent of the so-called minor ailments in this country. The causes are the overheating of the houses, the great dryness of the air, badly ventilated houses and public assembly rooms, which render people very susceptible to the great variations in temperature.

Prophylaxis, or the prevention of colds, combine all those measures which promote the general tone of the system, and may be said to embrace all the elements of personal hygiene. Good digestion and proper nourishment of the body with suitable food; the proper ventilation of houses, all public buildings and conveyances, for in these latter the public are brought into very close contact with their fellow-men.

Local prophylaxis would consist in the toilet of the nose and throat—the removing of adenoids and enlarged tonsils.

The individual must remember that she can reinfect herself; for this reason, an abundant supply of handkerchiefs must be used; they should be placed in a handkerchief bag and washed separately. Packs of cards should be thrown away before they become soiled. Sprays and atomizers must be individual property, and be kept thoroughly cleansed.

With the exception of deep-seated chest colds, in the early stages a cold may often be nipped in the bud by a few hours of hard sudorific work in the open air. In half a day the nasal ducts and respiratory system will throw off irritating matter that would take much longer time if the patient remained indoors and relied on the action of drugs alone.

Treatment.—Other methods of treatment are a hot tub-bath on retiring, an active but not too severe cathartic, as two grains of calomel, taken just before going to bed, and, if the individual is chilly, a hot lemonade should be taken at the same time. Both the cathartic and the free perspiration will aid in relieving the internal congestion and thus aid in its abortion. A cold sponge should be taken the following morning to tone up the system. Turkish baths are also useful in breaking up colds; again, the precaution must be taken to avoid chilling on leaving the bath.

The following tablet is a very simple and very efficacious remedy for breaking up a cold in the early stages: Take of powdered camphor ¼ gr.; of the sulphate of quinin ¼ gr.; and of the fluidextract of belladonna root ⅛ minim. This should be well mixed, and made up into one tablet or a capsule. One tablet is taken every half-hour, until four doses have been taken; after that one tablet every three hours, until the running of the nose has ceased, which generally occurs within twenty-four hours. If there is not marked improvement at the end of this time, or if there is any fever, a physician should be consulted at once.

Quinin, when given alone to abort colds, must be given in sufficiently large doses to produce cinchonism, the subjective symptom of which is a slight deafness or ringing of the ears. The natural tendency of cold is to cause inflammation of the middle ear, and since the use of quinin in large doses causes a congestion, and so predisposes to inflammation of the middle ear, its use should be avoided.

The great amount of illness and mortality from pneumonia during and following epidemics of influenza is too familiar to the public to need more than mentioning. The patient is so rapidly and extremely prostrated by the attack of influenza as to be susceptible to the ready action of the pneumococcus, which, as we have seen, is ever present, and the extension of the inflammation from the fine bronchial tubes to the air-cells of the lungs rapidly takes place. In the exhausted condition of the patient she is not able to resist this invasion, the heart is already weakened, and death frequently rapidly ensues as the immediate result of heart failure.

The Prevention of Tuberculosis.—The tubercle bacillus is practically ubiquitous, and the prevalence of tuberculosis is universal. Hence it is imperative to raise the resistance of the individual in every way possible, as well as to limit the spread of the infection. This means the employment of all the resources of public and personal hygiene, public and private sanitation, and the education of the public in how the disease is disseminated, and how its spread may be prevented; also the teaching of the individual, her duty to the family and society, as well as to herself, in order not to spread the contagion.

Tuberculosis attacks the crippled and poorly developed lung just as surely as it shuns the one which is fully expanded and in constant and active service. Numerous observations have established the existence of a constant ratio between tuberculosis of the lungs and deficient chest expansion.

Diet.—The doctrine has been growing among the laity that the child’s likes and dislikes should determine what food it should eat. Thus a finical taste is cultivated and a lack of proper nourishment follows, and it is this finical diet class of people which forms a large percentage of tuberculous invalids. It has long been recognized that a proper diet and the tolerance of it is of the utmost importance in the treatment of tuberculous patients, but from the foregoing it would appear that a proper diet throughout life is also of the utmost importance in the prevention of disease; a sufficiency, not only as to quantity, but also as regards variety.

It is the patient who can eat everything who stands a good chance of getting well. So, too, it is the individual whose diet for years has been perverse, who could not eat meat, to whom eggs were distasteful, who could not stand milk, who was infected with the vegetarian fad, or the two-meal-a-day fad, who stands a fair chance of falling a victim to tuberculosis, through a lowered tone of the system, because it offers but a feeble resistance to a powerful and insidious enemy. And the mode of the preparation of the food is an equally important factor. It has been shown that the poor cooking among the lower classes is a powerful predisposing cause to intemperance and tuberculosis.

Influenza is a frequent and important agent in bringing to light latent tuberculosis, and must be classed as an important exciting if not predisposing cause. Low, damp climates predispose to the infection by lowering the vitality. Tuberculosis is more prevalent in cities than in rural communities, due to the manner of housing and the character of the occupation.

Summary of the Present Views of Infection.—The doctrine of inherited and acquired susceptibility still holds sway; next, that all infants are susceptible, and that susceptibility lessens with increase in age; that adults are comparatively insusceptible when free from general and local lowered resistance and repeated and prolonged exposure.