Preventable Diseases. Woods Hutchinson
most exposed; hence the much greater frequency of hernia in the human species as compared with any of the animals.
Another fragment, of the impertinence of whose presence many of us have had painful proof, is the third or last molar, so absurdly misnamed the wisdom tooth. If there be any wisdom involved in its appearance it is of the sort characterized by William Allen White's delicious definition: "That type of ponderous folly of the middle-aged which we term 'mature judgment.'" The last is sometimes worst as well as best, and this belated remnant is not only the last to appear, but the first to disappear. In a considerable percentage of cases it is situated so far back in the jaw that there is no room for it to erupt properly, and it produces inflammatory disturbances and painful pressure upon the nerves of the face and the jaw.
Even when it does appear it is often imperfectly developed, has fewer cusps and fewer roots than the other molars, is imperfectly covered with enamel and badly calcified. In no small percentage of cases it does not meet its fellow of the jaw below and hence is almost useless for purposes of mastication. But it comes in every child born into the world, simply because at an earlier day, when our jaws were longer—to give our canine teeth the swing they needed as our chief weapons of defense—there was plenty of room for it in the jaw and it was of some service to the organism. If the Indiana State Legislature would only pass a law prohibiting the eruption of wisdom teeth in future, and enforce it, it would save a large amount of suffering, inconvenience, and discomfort, with little appreciable lack of efficiency!
In this list of admitted charges against heredity must also come the gall-bladder, that curious little pouch budded out from the bile ducts, which has so little known utility as compared with its possibility as a starting-point for inflammations, gall-stones, and cancer.
Then there is that disfiguring facial defect, hare-lip, due to a failure of the three parts of which our upper jaw is built to unite properly—this triple construction of the jaw being an echo of ancestral fishlike and reptilian times when our jaws were built in five pieces to permit of wide distention in the act of swallowing our prey alive. All over the surface of the body are to be found innumerable little sebaceous glands originally intended to lubricate hairs, which have now atrophied and disappeared. These useless scraps, under various forms of irritation, both external and internal, become inflamed and give rise to pimples, acne, or "a bad complexion."
And so the list might be drawn out to most impressive length. But this length would be no indication of its real importance, inasmuch as the vast majority of entries upon it would come under the head of pathological curiosities, or conditions which were chiefly interesting on account of their rareness and unusual character. With the exception of the appendix, the gall-bladder, and hernia, these vestigial conditions may be practically disregarded as factors in the death-rate.
In the main, when the fullest possible study and recognition have been made of all the traces of experimentation and even of ancient failure that are to be found in this Twentieth Century body-machine of ours, the resulting impression is one of enormously increased respect for and confidence in the machine and its capabilities. While they are of great interest as indicating what the past history and experiences of the engine have been, and of highest value as enabling us to interpret and even anticipate certain weak spots in its construction and joints in its armor, their most striking influence is in the direction of emphasizing the enormous elasticity and resourcefulness of the creature.
Not only has it met and survived all these difficulties, but it is continuing the selfsame processes to-day. So far as we are able to judge, it is as young and as adaptable as it ever was, and just as ready to "with a frolic welcome greet the thunder and the sunshine" as it ever was in the dawn of history.
These ancestral and experimental flaws, even when unrecognized and unguarded against, have probably not at any time been responsible for more than one or two per cent of the body's breakdowns; while, on the other hand, every process with which it fights disease, every trick of strategy which it uses against invading organisms, every step in the process of repair after wounds or injury, is a trick which it has learned in its million-year battle with its surroundings.
Take such a simple thing as the mere apparently blind habit possessed by the blood of coagulating as soon as it comes in contact with the edges of a cut or torn blood-vessel, and think what an enormous safeguard this has been and is against the possibility of death by hemorrhage. So well is it developed and so rapidly does it act that it is practically impossible to bleed some animals to death by cutting across any vessel smaller than one of the great aortic trunks. The rapidity and toughness of the clotting, combined with the other ancestral tricks of lowering the blood pressure and weakening down the heart, are so immensely effective that a slash across the great artery of the thigh in the groin of a dog will be closed completely before he can bleed to death. So delicate and so purposeful is this adjustment that the blood will continue as fluid as milk for ten, twenty, forty, eighty years—as long as it remains in contact with healthy blood-vessels. But the instant it is brought in contact with a broken or wounded piece of a vessel-wall, that instant it will begin to clot. So inevitable is this result that it gives rise to some of the sudden forms of death by bloodclot in the brain or lung (apoplexy, "stroke"), the clot having formed upon the roughened inner surface of the heart or of one of the blood-vessels and then floated into the brain or lung.
Then take that matchless and ingenious process of the healing of wounds, whose wondrousness increases with every step that we take into the deeper details of its study. First, the quick outpouring and clotting of the blood after enough has escaped to wash most poisonous or offending substances out of the wound. This living, surgical cement, elastic, self-moulding, soothing, not only plugs the cut or torn mouths of the blood-vessels, but fills the gap of the wound level with the surface. Here, by contact with the air and in combination with the hairs of the animal it forms a tough, firm, protective coating or scab, completely shutting out cold, heat, irritants, or infectious germs.
Into the wedge-shaped, elastic clot which now fills the wound from bottom to top like jelly in a mould, the leucocytes or white blood-cells promptly migrate and convert it into a mesh of living cells. They are merely the cavalry and skirmishers of the repair brigade and are quickly followed by the heavy infantry of the line in the shape of cells born of the injured tissues on either side of the wound. These join hands across the gap, the engineer corps and the commissariat department move up promptly to their support in the form of little vein-construction switches, which bud out from the wounded blood-vessels. The clot is transformed into what we term granulation tissue and begins to organize. A few days later this granulation tissue begins to contract and pull the lips of the wound together. If the gap has not been too wide the wound will be completely closed, its lips and deeper parts drawn together in nearly perfect line, separated only by a thin scar on the surface with a vertical keel of scar tissue descending from it. If the lips cannot be drawn together and there be no surgical skill at hand to assist them with stitches or bandages, then the gap will be filled up by the fibrous transformation of this granulation tissue and a thick, heavy scar result. Meanwhile, the skin-cells of the surface have not been idle, but are budding out on either side of the healing wound, pushing a little line of colonists forward across the raw surface. In longer or shorter time, according to the width of the gap, these two lines meet, and the site of our wound or the scar that it has left is perfectly coated over with a layer of healthy skin. This drama has occurred so many score of times in every one of us that custom has blinded our eyes to its ingenious perfection, but it took a million years to bring it to its present finish.
It may be a healthy corrective to our overweening conceit to remind ourselves that, remarkable and valuable as it is, it is a mere infant in arms compared to the superb powers of replacement and repair possessed by our more remote ancestors. Most invertebrates and many of the lowest two classes of backboned animals, the fishes and the amphibians, cannot merely stop up a rent, but renew an entire limb, fin—yes, even eye or head. Cut an earthworm in two and the rear half will grow a new head and the front half a new tail. It may even be cut in four or five segments, each of which will proceed to form a head at one end and a tail at the other. The lobster can regrow a complete gill and any number of claws or an eye. A salamander will reproduce a foot and part of a limb. Take out the crystalline lens in the eye of a salamander and the edge of the iris, or colored part of the eye, will grow another