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 œsophagus, 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.