Not only have most diseases a living cause, and a consequent natural history and course, but they have a special method of attack, which looks almost like a preference. It seems little wonder that the terror-stricken imagination of our Stone Age ancestors should have personified them as demons, "attacking" or leaping upon their victims and "seizing" them with malevolent delight. The concrete comparison was ready to their hand in the attack of fierce beasts of prey; and as the tiger leaps for the head to break the neck with one stroke of his paw, the wildcat flies at the face, the wolf springs for the slack of the flank or the hamstring, so these different disease demons appear each to have its favorite point of attack: smallpox, the skin; cholera, the bowels; the Black Death, the armpits and the groin; and pneumonia, the lung.

There are probably few diseases which are so clearly recognized by every one and about which popular impressions are in the main so clear-cut and so correct as pneumonia. The stabbing pain in the chest, the cough, the rusty or blood-stained expectoration, the rapid breathing, all stamp it unmistakably as a disease of the lung. Its furious onset with a teeth-chattering chill, followed by a high fever and flushed face, and its rapid course toward recovery or death, mark it off sharply from all other lung infections.

Its popular names of "lung fever," "lung plague," "congestion of the lungs," are as graphic and distinctive as anything that medical science has invented. In fact, our most universally accepted term for it, pneumonia, is merely the Greek equivalent of the first of these.

It is remarkable how many of our disease-enemies appear to have a preference for the lung as a point of attack. In the language of Old Man Means in "The Hoosier Schoolmaster," the lung is "their fav'rit holt." Our deadliest diseases are lung diseases, headed by consumption, seconded by pneumonia, and followed by bronchitis, asthma, etc.; together, they manage to account for one-fourth to one-third of all the deaths that occur in a community, young or old. No other great organ or system of the body is responsible for more than half such a mortality. Now this bad eminence has long been a puzzle, since, foul as is the air or irritating as is the gas or dust that we may breathe into our lungs, they cannot compare for a moment with the awful concoctions in the shape of food which are loaded into our stomachs. Even from the point of view of infections, food is at least as likely to be contaminated with disease-germs as air is. Yet there is no disease or combination of diseases of the whole food canal which has half the mortality of consumption alone, in civilized communities, while in the Orient the pneumonic form of the plague is a greater scourge than cholera.

It has even been suggested that there may possibly be a historic or ancestral reason for this weakness to attack, and one dating clear back to the days of the mud-fish. It is pointed out that the lung is the last of our great organs to develop, inasmuch as over half of our family tree is under water. When our mud-loving ancestor, the lung-fish (who was probably "one of three brothers" who came over in the Mayflower—the records have not been kept) began to crawl out on the tide-flats, he had every organ that he needed for land-life in excellent working condition and a fair degree of complexity: brain, stomach, heart, liver, kidneys; but he had to manufacture a lung, which he proceeded to do out of an old swim-bladder. This, of course, was several years ago. But the lung has not quite caught up yet. The two or three million year lead of the other organs was too much to be overcome all at once. So carelessly and hastily was this impromptu lung rigged up that it was allowed to open from the front of the gullet or oesophagus, instead of the back, while the upper part of the mouth was cut off for its intake tube, as we have already seen in considering adenoids, thus making every mouthful swallowed cut right across the air-passages, which had to be provided with a special valve-trap (the epiglottis) to prevent food from falling into the lungs.

So, whenever you choke at table, you have a right to call down a benediction upon the soul of your long departed ancestor, the lung-fish. However applicable or remote we may regard "the bearin's of this observation," the practical and most undesirable fact confronts us to-day that this crossing and mutual interference of the air and the food-passages is a fertile cause of pneumonia, inasmuch as the germs of this disease have their habitat in the mouth, and are from that lurking-place probably inhaled into the lung, as is also the case with the germs of several milder bronchitic and catarrhal affections.

It may be also pointed out that, history apart, our lung-cells at the present day are at another disadvantage as compared with all the other cells of the body, except those of the skin; and that is, that they are in constant contact with air, instead of being submerged in water. Ninety-five per cent of our body-cells are still aquatic in their habits, and marine at that, and can live only saturated with, and bathed in, warm saline solution. Dry them, or even half-dry them, and they die. Even the pavement-cells coating our skin surfaces are practically dead before they reach the air, and are shed off daily in showers.

We speak of ourselves as "land animals," but it is only our lungs that are really so. All the rest of the body is still made up of sea creatures. It is little wonder that our lungs should pay the heaviest penalty of our change from the warm and equable sea water to the gusty and changeable air.

Even if we have set down the lung as a point of the least resistance in the body, we have by no means thereby explained its diseases. Our point of view has distinctly shifted in this respect within recent years. Twenty years ago pathologists were practically content with tracing a case of illness or death to an inflammation or disease of some particular organ, like the heart, the kidney, the lung, or the stomach. Now, however, we are coming to see that not only may the causation of this heart disease, kidney disease, lung disease, have lain somewhere entirely outside of the heart, kidney, or lung, but that, as a rule, the entire body is affected by the disease, which simply expresses itself more violently, focuses, as it were, in this particular organ. In other words, diseases of definite organs are most commonly the local expressions of general diseases or infections; and this local aggravation of the disease would never have occurred if the general resisting power and vigor of the entire body had not been depressed below par. So that even in guarding against or curing a disease of a particular organ it is necessary to consider and to treat the whole body.

Nowhere is this new attitude better illustrated than in pneumonia. Frank and unquestioned infection as it is, wreaking two-thirds of its visible damage in the lung itself, the liability to its occurrence and the outlook for its cure depend almost wholly upon the general vigor and rallying power of the entire body. It is perfectly idle to endeavor to avoid it by measures directed toward the protection of the lung or of the air-passages, and equally futile to attempt to arrest its course by treatment directed to the lung, or even the chest. The best place to wear a chest-protector is on the soles of the feet, and poulticing the chest for pneumonia is about as effective as shampooing the scalp for brain-fag.

This clears the ground of a good many ancient misconceptions; for instance, that the chief cause of pneumonia is direct exposure to cold or a wetting, or the inhalation of raw, cold air. Few beliefs were more firmly fixed in the popular mind—and, for the matter of that, in the medical—up to fifteen or twenty years ago. It has found its way into literature; and the hero of the shipwreck in an icy gale or of weeks of wandering in the Frozen North, who must be offered up for artistic reasons as a sacrifice to the plot, invariably dies a victim of pneumonia, from his "frightful exposure," just as the victim of disappointed love dies of "a broken heart," or the man who sees the ambitions of years come crashing about his ears, or the woman who has lost all that makes life worth living, invariably develops "brain fever."

There is a physical basis for all of these standard catastrophes, but it is much slenderer than is usually supposed. For instance, almost every one can tell you how friends of theirs have "brought on congestion of the lungs," or pneumonia, by going without an overcoat on a winter day, or breaking through the ice when skating, or even by getting their feet wet and not changing their stockings; and this single dramatic instance has firmly convinced them that the chief cause of "lung fever" is a chill or a wetting. Yet when we come to tabulate long series of causes, rising into thousands, we find that the percentage in which even the patients themselves attribute the disease to exposure, or a chill, sinks to a surprisingly small amount. For instance, in the largest series collected with this point in mind, that of Musser and Norris, out of forty-two hundred cases only seventeen per cent gave a history of exposure and "catching cold"; and the smaller series range from ten to fifteen per cent. So that, even in the face of the returns, not more than one-fifth of all cases of pneumonia can reasonably be attributed to chill. And when we further remember that under this heading of exposure and "catching cold" are included many mere coincidences and the chilly sensations attending the beginning of those milder infections which we term "common colds," it is probable that even this small percentage could be reduced one-half. Indeed, most cautious investigators of the question have expressed themselves to this effect. This harmonizes with a number of obstinate facts which have long proved stumbling-blocks in the way of the theory of exposure as a cause of pneumonia. One of the classic ones was that, during Napoleon's frightful retreat from Moscow in the dead of winter, while his wretched soldiers died by thousands of frost-bite and starvation, exceedingly little pneumonia developed among them. Another was that, as we have already seen with colds, instead of being commoner and more frequent in the extreme Northern climate and on the borders of the Arctic Zone, pneumonia is almost unknown there. Of course, given the presence of the germ, prolonged exposure to cold may depress the vital powers sufficiently to permit an attack to develop.

Again, the ages at which pneumonia is both most common and most deadly, namely, under five and over sixty-five, are precisely those at which this feature of exposure to the weather plays the most insignificant part. Last and most conclusive of all, since definite statistics have begun to be kept upon a large scale, pneumonia has been found to be emphatically a disease of cities, instead of country districts. Even under the favorable conditions existing in the United States, for instance, the death-rate per hundred thousand living, according to the last census, was in the cities two hundred and thirty-three, and for the country districts one hundred and thirty-five,—in other words, nearly seventy per cent greater in city populations.

How, then, did the impression become so widely spread and so firmly rooted that pneumonia is chiefly due to exposure? Two things, I think, will explain most of this. One is, that the disease is most common in the winter-time, the other, that like all febrile diseases it most frequently begins with sensations of chilliness, varying all the way from a light shiver to a violent chill, or rigor. The savage, bone-freezing, teeth-rattling chill which ushers in an attack of pneumonia is one of the most striking characteristics of the disease, and occurs in twenty-five to fifty per cent of all cases.

Its chief occurrence in the winter-time is an equally well-known and undisputed fact, and it has been for centuries set down in medical works as one of the diseases chiefly due to changes in temperature, humidity, and directions of the wind. Years of research have been expended in order to trace the relations between the different factors in the weather and the occurrence of pneumonia, and volumes, yes, whole libraries, published, pointing out how each one of these factors, the temperature, humidity, direction of wind, barometric pressure, and electric tension, is in succession the principal cause of the spread of this plague. Many interesting coincidences were shown. But one thing always puzzled us, and that was, that the heaviest mortality usually occurred, not just at the beginning of winter, when the shock of the cold would be severest, nor even in the months of lowest temperature, like December or January, but in the late winter and the early spring. Throughout the greater part of the temperate zone the death-rate for pneumonia begins to rise in December, increases in January, goes higher still in February, reaching its climax in that month or in March. April is almost as bad, and the decline often doesn't fairly set in until May.

No better illustration could probably be given of the danger of drawing conclusions when you are not in possession of all the facts. One thing was entirely overlooked in all this speculation until about twenty years ago,—that pneumonia was due not simply to the depressing effects of cold, but to a specific germ, the pneumococcus of Fraenkel. This threw an entirely new light upon our elaborate weather-causation theories. And while these still hold the field by weight of authority and that mental inertia which we term conservatism, yet the more thoughtful physicians and pathologists are now coming to regard these factors as chiefly important according to the extent to which we are crowded together in often badly lighted and ill-ventilated houses and rooms, with the windows and doors shut to save fuel, thus affording a magnificent hothouse hatching-ground for such germs as may be present, and ideal facilities for their communication from one victim to another. At the same time, by this crowding and the cutting off of life and exercise in the open air which accompanies it, the resisting power of our bodies is lowered. And when these two processes have had an opportunity of progressing side by side for from two to three months; when, in other words, the soil has been carefully prepared, the seed sown, and the moist heat applied as in a forcing-house, then we suddenly reap the harvest. In other words, the heavy crop of pneumonia in January, February, and March is the logical result of the seed-sowing and forcing of the preceding two or three months.

The warmth of summer is even more depressing in its immediate effects than the cold of winter, but the heat carries with it one blessing, in that it drives us, willy-nilly, into the open air, day and night. And on looking at statistics we find precisely what might have been expected on this theory, that the death-rate for pneumonia is lowest in July and August.

It might be said in passing that, in spite of our vivid dread of sunstroke, of cholera, and of pestilence in hot weather, the hot months of the year in temperate climates are invariably the months of fewest diseases and fewest deaths. Our extraordinary dread of the summer heat has but slender rational physical basis. It may be but a subconscious after-vibration in our brain cells from the simoons, the choleras, and the pestilences of our tropical origin as a race. Open air, whether hot, cold, wet, dry, windy, or still, is our best friend, and house air our deadliest enemy.

If this view be well founded, then the advance of modern civilization would tend to furnish a more and more favorable soil for the spread of this disease. This, unfortunately, is about the conclusion to which we are being most unwillingly driven. Almost every other known infectious disease is diminishing, both in frequency and in fatality, under civilization. Pneumonia alone defies our onslaughts. In fact, if statistics are to be taken at their surface-value, we are facing the appalling situation of an apparently marked increase both in its prevalence and in its mortality. For a number of years past, ever since, in fact, accurate statistics began to be kept, pneumonia has been listed as the second heaviest cause of death, its only superior being tuberculosis.

About ten years ago it began to be noticed that the second competitor in the race of death was overtaking its leader, and this ghastly rivalry continued until about three years ago pneumonia forged ahead. In some great American cities it now occupies the bad eminence of the most fatal single disease on the death-lists.

The situation is, however, far from being as serious and alarming as it might appear, simply from this bald statement of statistics. First of all, because the forging ahead of pneumonia has been due in greater degree to the falling behind of tuberculosis than to any actual advance on its part. The death-rate of tuberculosis within the last thirty years has diminished between thirty and forty per cent; and pneumonia at its worst has never yet equaled the old fatality of tuberculosis. Furthermore, all who have carefully studied the subject are convinced that much of this apparent increase is due to more accurate and careful diagnosis. Up to ten years or so ago it was generally believed that pneumonia was rare in young children. Now, however, that we make the diagnosis with a microscope, we discover that a large percentage of the cases of capillary bronchitis, broncho-pneumonia, and acute congestion of the lung in children are due to the presence of the pneumococcus. Similarly, at the other end of the line, deaths that were put down to bronchitis, asthma, heart failure, yes, even to old age, have now been shown on bacteriological examination to be due to this ubiquitous imp of malevolence; so that, on the whole, all that we are probably justified in saying is that pneumonia is not decreasing under civilization. This is not to be wondered at, inasmuch as the inevitable crowding and congestion which accompanies civilization, especially in its derivative sense of "citification," tends to foster it in every way, both by multiplying the opportunities for infection and lowering the resisting power of the crowded masses.

Moreover, it was only in the last ten years, yes, within the last five years, that we fairly grasped the real method and nature of the spread of the disease, and recognized the means that must be adopted against it. And as all of these factors are matters which are not only absolutely within our own control, but are included in that programme of general betterment of human comfort and vigor to which the truest intelligence and philanthropy of the nation are now being directed, the outlook for the future, instead of being gloomy, is distinctly encouraging.

Our chief difficulty in discovering the cause of pneumonia lay in the swarm of applicants for the honor. Almost every self-respecting bacteriologist seemed to think it his duty to discover at least one, and the abundance and variety of germs constantly or accidentally present in the human saliva made it so difficult positively to isolate the real criminal that, although it was identified and described as long ago as 1884 by Fraenkel, the validity of its claim was not generally recognized and established until nearly ten years later.

It is a tiny, inoffensive-looking little organism, of an oval or lance-head shape, which, after masquerading under as many aliases as a confidence man, has finally come to be called the pneumococcus, for short, or "lung germ." Though by those who are more precise it is still known as the Diplococcus pneumoniÆ or Diplococcus lanceolatus, from its faculty of usually appearing in pairs, and from its lance-like shape. Its conduct abounds in "ways that are dark and tricks that are vain," whose elucidation throws a flood of light upon a number of interesting problems in the spread of disease.

First of all, it literally fulfills the prognostic of Scripture, that "a man's foes shall be they of his own household," for its chosen abiding place and normal habitat is no less intimate a place than the human mouth. Outside of this warm and sheltering fold it perishes quickly, as cold, sunlight, and dryness are alike fatal to it.

We could hardly believe the evidence of our senses when studies of the saliva of perfectly healthy individuals showed this deadly little bacillus to be present in considerable numbers in from fifteen to forty-five per cent of the cases examined. Why, then, does not every one develop pneumonia? The answer to this strikes the keynote of our modern knowledge of infectious disease, namely, that while an invading germ is necessary, a certain breaking down of the body defenses and a lowering of the vital resistance are equally necessary. These invaders lie in wait at the very gates of the citadel, below the muzzles of our guns, as it were, waiting for some slackening of discipline or of watchfulness to rush in and put the fortress to sack. Nowhere is this more strikingly true than in pneumonia. It is emphatically a disease where, in the language of the brilliant pathologist-philosopher Moxon, "While it is most important to know what kind of a disease the patient has got, it is even more important to know what kind of a patient the disease has got."

The death-rate in pneumonia is an almost mathematically accurate deduction from the age, vigor, and nutrition of the patient attacked. No other disease has such a brutal and inveterate habit of killing the weaklings. The half-stifled baby in the tenement, the underfed, overworked laboring man, the old man with rigid arteries and stiffening muscles or waning life vigor, the chronic sufferer from malnutrition, alcoholism, Bright's disease, heart disease—these are its chosen victims.

Another interesting feature about the pneumococcus is its vitality outside of the body. If the saliva in which it is contained be kept moist, and not exposed to the direct sunlight and in a fairly warm place, it may survive as long as two weeks. If dried, but kept in the dark, it will survive four hours. If exposed to sunlight, or even diffuse daylight, it dies within an hour. In other words, under the conditions of dampness and darkness which often prevail in crowded tenements it may remain alive and malignant for weeks; in decently lighted and ventilated rooms, less than two hours. This explains why, in private practice and under civilized conditions, epidemics of this admittedly infectious disease are rare; while in jails, overcrowded barracks, prison ships, and winter camps of armies in the field they are by no means uncommon. This is vividly supported by the fact brought out in our later investigations of the sputum of slum-dwellers, carried out by city boards of health, that the percentage of individuals harboring the pneumococcus steadily increases all through the winter months, from ten per cent in December to forty-five, fifty, and even sixty per cent in February and March. The old proverb, "When want comes in at the door, Love flies out at the window," might be revised to read, "When sunlight comes in at the window the pneumococcus flies 'up the flue.'"

Authorities are still divided as to the meaning and even the precise frequency of the occurrence of the pneumococcus in the healthy human mouth. Some hold that its presence is due to recent infection which has either been unable to gain entrance to the system or is preparing its attack; others, that it is a survival from some previous mild attack of the disease, and the body tissues having acquired immunity against it, it remains in them as a harmless parasite, as is now well known to be the case with the germs of several of our infectious diseases—for instance, typhoid—for months and even years afterward. Others hold the highly suggestive view that it is a normal inhabitant of the healthy mouth, which can become injurious to the body, or pathogenic, only under certain depressed or disturbed conditions of the latter. In defense of this last it may be pointed out that dental bacteriologists have now already isolated and described some thirty different forms of organisms which inhabit the mouth and teeth; and the pneumococcus may well be one of these. Further, that a number of our most dangerous disease germs, like the typhoid bacillus, the bacillus of tuberculosis, and the bacillus of diphtheria, have almost perfect "doubles," law-abiding relatives, so to speak, among the germs that normally inhabit our throats, our intestines, or our immediate surroundings. The ultimate foundation question of the science of bacteriology is, How did the disease germs become disease germs? But the question is still unanswered.

However, fortunately, here, as in other human affairs, imperfect as our knowledge is, it is sufficient to serve as a guide for practical conduct. Widely present as the pneumococcus is, we know well that it is powerless for harm except in unhealthful surroundings. There is another interesting feature of its life history which is of practical importance, and that is, like many other bacilli it is increased in virulence and infectiousness by passing through the body of a patient. Flushed with victory over a weakened subject, it acquires courage to attack a stronger. This is the reason why, in those comparatively infrequent instances in which pneumonia runs through a family, it is the strongest and most vigorous members of the family who are the last to be attacked. It also explains one of the paradoxes of this disease, that, while emphatically a disease of overcrowding and foul air, and attacking chiefly weakened individuals, it is a veritable scourge of camps, whether mining or military. When once three or four cases of pneumonia have occurred in a mining camp, even though this consist almost exclusively of vigorous men, most of them in the prime of life, it acquires a virulence like that of a pestilence, so that, while ordinarily not more than fifteen to twenty per cent of those attacked die, death-rates of forty, fifty, and even seventy per cent are by no means uncommon in mining camps. The fury and swiftness of this "miners' pneumonia" is equally incredible. Strong, vigorous men are taken with a chill while working in their sluicing ditches, are delirious before night, and die within forty-eight hours. So widely known are these facts, and so dreaded is the disease throughout the Far West and in mountain regions generally, that there is a widespread belief that pneumonia at high altitudes is particularly deadly.

I had occasion to interest myself in this question some years ago, and by writing to colleagues practicing at high elevations and collecting reports from the literature, especially of the surgeons of army posts in mountain regions, was somewhat surprised to find that the mortality of all cases occurring above five thousand feet elevation was almost identical with that of a similar class of the population at sea-level. It is only when a sufficient number of cases occur in succession to raise the virulence of the pneumococcus in this curious manner that an epidemic with high fatality develops.

That this increase in virulence in the organism does occur was clearly demonstrated by a bacteriologist friend of mine, who succeeded in securing some of the sputum from a fatal case in the famous Tonopah epidemic of some years ago, an epidemic so fatal that it was locally known as the "Black Death." Upon injecting cultures from this sputum into guinea-pigs, the latter died in one-quarter of the time that it usually took them to succumb to a similar dose of an ordinary culture of the pneumococcus.

It is therefore evident that just as "no chain is stronger than its weakest link," so in the broad sense no community is stronger than its weakest group of individuals, and pneumonia, like other epidemics, may be well described as the vengeance which the "submerged tenth" may wreak from time to time upon their more fortunate brethren.

Now that we know that under decent and civilized conditions of light and ventilation the pneumococcus will live but an hour to an hour and a half, this reduces the risk of direct infection under these conditions to a minimum. It is obvious that the principal factors in the control of the disease are those which tend to build up the vigor and resisting power of all possible victims. The more broadly we study the disease the more clearly do the data point in this direction.

First of all, is the vivid and striking contrast between hospital statistics and those gathered from private practice. While many individuals of a fair wage-earner's income and good bodily vigor are treated in our hospitals, yet the vast majority of hospital patients are technically known as the "hospital classes," apt to be both underfed, overworked, and overcrowded. On the other hand, while a great many both of the very poor and even of the destitute are treated in private practice, yet the majority of such cases who feel "able to afford a doctor," as they say, are among the comparatively vigorous, well-fed, and well-housed section of the community. And the difference between the death-rate of the two classes in pneumonia is most significant. In private practice, while epidemics differ in virulence, the rate ranges all the way from five per cent to fifteen per cent, the average being not much in excess of ten per cent, occasionally falling as low as three per cent. In the hospital reports on the contrary the death-rate begins at twenty per cent and climbs to thirty, forty, and forty-five per cent. It is only fair to say, of course, that hospital statistics probably include a larger percentage of more serious cases, the milder ones being taken care of at home, or not presenting themselves for treatment at all. But even when this allowance has been made, the contrast is convincing.

A similar influence is exercised by age. Although pneumonia is common at all ages, its heaviest death-rate falls at the two extremes, under six years of age and over sixty, with a strong preponderance in the latter. Under five years of age, the mortality may reach twenty to thirty per cent; from five to twenty-five, not more than four to five per cent; from twenty-five to thirty-five, from fifteen to twenty per cent; and so on, increasing gradually with every decade until by sixty years of age the mortality has reached fifty per cent, and from sixty to seventy-five may be expressed in terms of the age of the patient. One consoling feature, however, about it is that its mortality is lowest in the ages at which it is most frequent, namely, from ten to thirty-five years of age. And its frequency diminishes even more rapidly than its fatality increases in later years. So that while it is much more serious in a middle-aged man, he is less liable to develop it than a younger one. Where the mortality from pneumonia is highest, is in the most densely populated wards, especially among negroes and foreigners of the hospital class, in individuals who are victims of chronic alcoholism, and also among those who are for long periods insufficiently nourished. Lastly, it is only within comparatively recent years that we have come clearly to recognize the large rÔle which pneumonia plays in giving the finishing stroke to chronic diseases and degenerative processes. It is, for instance, one of the commonest actual causes of death in Bright's disease, in diabetes, in lingering forms of tuberculosis, and in heart disease; and last of all, in that progressive process of normal degeneration and decay which we term "Old Age." It is one of the most frequent and fatal of what Flexner described a decade ago as "terminal infections." Very few human beings die by a gradual process of decay, still less go to pieces all at once, like the immortal "One-Hoss Shay." Just as soon as the process has progressed far enough to lower the resisting power below a certain level, some acute infection steps in and mercifully ends the scene. This is peculiarly true of pneumonia in old age.

To the medical profession to "die of old age" is practically equivalent to dying of pneumonia. The disease is so mild in its symptoms and so rapid in its course that it often utterly escapes recognition as such.

The old man complains of a little pain in his chest, a failure of appetite, a sense of weakness and dizziness. He takes to his bed, within forty-eight hours he becomes unconscious, and within twenty-four more he is peacefully breathing his last. After death, two-thirds of the lung will be found consolidated. So mild and rapid and painless is the process that one physician-philosopher actually described pneumonia as "the friend of old age."

When once the disease has obtained a foothold in the body its course, like one of Napoleon's campaigns, is short, sharp, and decisive. Beginning typically with a vigorous chill, sometimes so suddenly as to wake the patient out of a sound sleep, followed by a stabbing pain in the side, cough, high fever, rapid respiration, the sputum rusty or orange-colored from leakage of blood from the congested lung, within forty-eight hours the attacked area of the lung has become congested; in forty-eight more, almost solidified by the thick, sticky exudate poured out from the blood-vessels, which coagulates and clots in the air cells. So complete is this solidification that sections of the attacked lung, instead of floating in water as normal lung-tissue will, sink promptly. The severe pain usually subsides soon, but the fever, rapid respiration, flushed face, with or without delirium, will continue for from three to seven or eight days. Then, as suddenly as the initial attack, comes a plunge down of the temperature to normal. Pain and restlessness disappear, the respiration drops from thirty-five or forty to fifteen or twenty per minute, and the disease has practically ended by "crisis." Naturally, after such a furious onslaught, the patient is apt to be greatly weakened. He may have lost twenty or thirty pounds in the week of the fever, and from one to three weeks more in bed may be necessary for him to regain his strength. But the chief risk and danger are usually over within a week or ten days at the outside.

Violent and serious as are the changes in the lung, it is very seldom that death comes by interference with the breathing space. In fact, while regarded as a lung disease, we are now coming to recognize that the actual cause of death in fatal cases is the overwhelming of the heart by the toxins or poisons poured into the circulation from the affected lung. The mode of treatment is, therefore, to support the strength of the patient in every way, and measures directed to the affected lung are assuming less and less importance in our arsenal of remedies. Our attitude is now very similar to that in typhoid, to support the strength of the patient by judicious and liberal feeding, to reduce the fever and tone up his blood-vessels by cool sponging, packing, and even bathing; to relieve his pain by the mildest possible doses of sedatives, knowing that the disease is self-limited, and that in patients in comfortable surroundings and fair nutrition from eighty to ninety per cent will throw off the attack within a week. So completely have we abandoned all idea of medicating or protecting the lung as such, that in place of overheated rooms, loaded with vapor by means of a steam kettle, for its supposed soothing effect upon the inflamed lung, we now throw the windows wide open. And some of our more enthusiastic clinicians of wide experience are actually introducing the open-air cure, which has worked such wonders in tuberculosis, in the treatment of pneumonia. In more than one of our New York hospitals now, particularly those devoted to the care of children, following the brilliant example of Dr. William Northrup, wards are established for pneumonia cases out on the roof of the hospital, even when the snow is banked up on either side, and the covering is a canvas tent. Nurses, physicians, and ward attendants are clothed in fur coats and gloves, the patients are kept muffled up to the ears, with only the face exposed; but instead of perishing from exposure, little, gasping, struggling tots, whose cases were regarded as practically hopeless in the wards below, often fall into the sleep that is the turning point toward recovery within a few hours after being placed in this winter roof-garden.

In short, our motto may be said to be, "Take care of the patient, and the disease will take care of itself."

Though pneumonia is one of our most serious and most fatal of diseases, yet it is one over whose cause, spread, and cure we are obtaining greater and greater control every day, and which certainly should, within the next decade, yield to our attack, as tuberculosis and typhoid are already beginning to do.