Preventable Diseases. Woods Hutchinson
OUR LEGACY OF HEALTH: THE POWER OF HEREDITY IN THE PREVENTION OF DISEASE
The evil in things always bulks large in our imaginations. It is no mere coincidence that the earliest gods of a race are invariably demons. Our first conception of the great forces of nature is that they are our enemies. This misconception is not only natural, but even necessary on the sternest of physical bases. The old darky, Jim, in Huckleberry Finn, hit upon a profound and far-reaching truth when he replied in answer to Huck's question whether among all the signs and portents with which his mind was crammed—like black cats and seeing the moon over your left shoulder and "harnts"—some were not indications of good luck instead of all being of evil omen:—
"Mighty few—an' dey ain't no use to a body. What fur you want to know when good luck's a-comin'? Want to keep it off?"
It isn't the good, either in the forces of nature or in our fellows, that keeps us watchful, but the evil. Hence our proneness to declare in all ages that evil is stronger than good and that "all men are liars." One injury done us by storm, by sunstroke, by lightning-flash, will make a more lasting impression upon our memories than a thousand benefits conferred by these same forces. Besides, evil has to be sharply looked out for and guarded against. Well enough can be safely let alone.
The conviction is steadily growing, among both physicians and biologists, that this attitude has caused a serious, if not vital, misconception of the influence of that great conservative and preservative force of nature—heredity. We hear a great deal of hereditary disease, hereditary defect, hereditary insanity, but very little of hereditary powers of recovery, of inherited vigor, and the fact that ninety-nine and seven-tenths per cent of us are sane.
One instance of hereditary defect, of inherited degeneracy, fills us with horror and stirs us to move Heaven and earth to prevent another such. The inheritance of vigor, of healthfulness, and of sanity we placidly accept as a matter of course and bank upon it in our plans for the future, without so much as a thank you to the force that underlies it.
When once we clear away these inherited misconceptions and look the facts of the situation squarely in the face, we find that heredity is at least ten times as potent and as frequently concerned in the transmission and securing of health and vigor as of disease and weakness; that its influence on the perpetuation of bodily and mental defects has been enormously exaggerated and that there are exceedingly few hereditary diseases.
It is not necessary for our present purpose to enter into a discussion of the innumerable theories of that inevitable tendency of like to beget like, of child to resemble parent, which we call heredity. One reference, however, may be permitted to the controversy that has divided the scientific world: whether acquired characters, changes occurring during the lifetime of the individual, can be inherited. Disease is nine times out of ten an acquired character; hence, instead of the probabilities being that it would be inherited, the balance of evidence to date points in exactly the opposite direction. The burden of proof as to the inheritance of disease is absolutely upon those who believe in its possibility.
Another fundamental fact which renders the inheritance of disease upon a priori grounds improbable and upon practical grounds obviously difficult, is that characters or peculiarities, in order to be inherited certainly for more than a few generations, must be beneficial and helpful in the struggle. A moment's reflection will show this to be mathematically necessary, in that any family or race which tended to inherit defects and injurious characters would rapidly go down in the struggle for survival and become extinct. An inherited disease of any seriousness could not run for more than two or three generations in any family, simply for the reason that by the end of that time there would be no family left for it to run in. A slight defect or small peculiarity of undesirable character might run for a somewhat longer period, but even this would tend toward disappearance and elimination by the stern, selective influence of environment.
Naturally, this great conservative tendency of nature has, like all other influences, "the defects of its virtues," as the French say. It has no gifts of prophecy, and in the process of handing down to successive generations those mechanisms and powers which have been found useful in the long, stern struggle of the past, it will also hand down some which, by reason of changes in the environment, are not only no longer useful, but even injurious. As the new light of biology has been turned on the human body and its diseases, it has revealed so many of these "left-overs," or remnants in the body-machine—some of most dramatic interest—that they at first sight have done much to justify the popular belief in the malignant tendencies of heredity.
Yet, broadly considered, the overwhelming majority of them should really be regarded as honorable scars, memorials of ancient victories, monuments to difficulties overcome, significant and encouraging indications of what our body-machine is still capable of accomplishing in the way of further adjustment to conditions in the future. The really surprising thing is not their number, but the infrequency with which they give rise to serious trouble.
The human automobile is not only astonishingly well built, with all the improvements that hundreds of thousands of generations of experience have been able to suggest, but it is self-repairing, self-cleaning, and self-improving. It never lets itself get out of date. If only given an adequate supply of fuel and water and not driven too hard, it will stand an astonishing amount of knocking about in all kinds of weather, repairing itself and recharging its batteries every night, supplying its own oil, its own paint and polish, and even regulating its own changes of gear, according to the nature of the work it has to do. Simply as an endurance racer it is the toughest and longest-winded thing on earth and can run down and tire out every paw, pad, or hoof that strikes the ground—wolf, deer, horse, antelope, wild goat. This is only a sample of its toughness and resisting power all along the line.
These wide powers of self-support and adjustment overbalance a hundred times any little remnant defects in its machinery or gearing. Easily ninety-nine per cent of all our troubles through life are due to inevitable wear and tear, scarcity of food-fuel, of water, of rest, and external accidents—injuries and infectious diseases. Still, it occasionally happens that these little defects may furnish the point of least resistance at which external stresses and strains will cause the machine to break down. They are often the things which prevent us from living and "going to pieces all at once, all at once and nothing fust, just as bubbles do when they bust," like the immortal One-Hoss Shay. It is just as well that they should, for, of all deaths to die, the loneliest and the most to be dreaded is that by extreme old age.
These vestigia or remnants—instances of apparently hidebound conservatism on nature's part—are very much in the public eye at present, partly on account of their novelty and of their exceptional and extraordinary character. Easily first among these trouble-breeding remnants is that famous, or rather notorious, scrap of intestine, the appendix vermiformis, an obvious survival from that peaceful, ancestral period when we were more largely herbivorous in our diet and required a longer and more complicated food-tube, with larger side pouches in the course of it, to dissolve and absorb our food. Its present utility is just about that of a grain of sand in the eye. Yet, considering that it is present in every human being born into the world, the really astonishing thing is not the frequency with which it causes trouble, but the surprisingly small amount of actual damage that arises from it. Never yet in even the most appendicitis-ridden community has it been found responsible for more than one half of one per cent of the deaths.
Then there is that curious and by no means uncommon tendency for a loop of the intestine to escape from the abdominal cavity, which we call hernia. This is one of a fair-sized group of dangers clearly due to the assumption of the erect position and our incomplete adjustment thereto. In the quadrupedal position this necessary weak spot—a partial opening through the abdominal wall—was developed in that region which was highest from the point of view of gravity and least exposed to strain. In the bipedal position it becomes