Preventable Diseases

by Woods Hutchinson

In fact, the consensus of intelligent expert opinion upon the subject of heredity of cancer is, that though it may occur, we have comparatively little proof of the fact; that the percentage of cases in which there is cancer in the family is but little larger than might be expected on the doctrine of probabilities from the average distribution. Though possibly the offspring of a cancerous individual may display a slightly greater tendency toward the development of that strange, curious process of "autonomy" than the offspring of the average individual, this tendency is so small and occurs so infrequently as to be a factor of small practical importance in the propagation and spread of the disease.

In insanity and epilepsy we have probably the last refuge and almost only valid instance of the old belief in the remorseless heredity of disease. But even here the part played by heredity is probably only a fraction of that which it is popularly, and even professionally, believed to play. It is, of course, obvious that diseases which tend quickly to destroy the life of the patient, especially those which kill or seriously cripple him before he has reached the age of reproduction, or prevent his long surviving that epoch, will not, for mechanical reasons, become hereditary. The Black Death, or the cholera, for instance, could not "run in a family." Supposing that children were born with a special susceptibility to this disease, there would obviously soon be no family left.

The same is true in a lesser degree of milder or more chronic diseases. The family which was hereditarily predisposed to scarlet fever, measles, smallpox, or tuberculosis would not last long, and in fact the whole progress of civilization has been a continuous process of the weeding out of those who were most susceptible and the survival of those who were least so.

But when we come to deal with certain conditions, fortunately rare, such as functional disturbances of the nervous system, which neither seriously unfit their possessor for the struggle of life nor prevent him from reproducing his kind, then it becomes possible that a tendency to such disease may be transmitted through several successive generations.

Such is the case with insanity, with epilepsy, with hemophilia, or "bleeders," and with certain rare and curious disturbances of the nervous system, such as the hereditary ataxias and "tics" of various sorts. However, even here the only conditions on which these diseases can continue to run in a family for more than one or two generations is either that they shall be mild in form or that only a comparatively small percentage of the total family shall be affected by them. If, for instance, two-thirds, one-half, or even a third of the descendants of a mentally unsound individual were to become insane, it would only need a few generations for that family to be crushed to the wall.

While the descendants of insane persons are distinctly more liable to become insane than the rest of the community, yet, on account of their fewness, this tendency probably does not account for more than a small fraction of the total insanity. We should, by all means, prevent the marriage of the insane and discourage that of their children, and the development of any well-defined form of insanity should act at once, ipso facto, as a ground and cause of divorce.

But the consoling fact remains that even of such children, providing, of course, as usually happens, that the other parent—husband or wife—is sound and sane, not more than ten or fifteen per cent would probably become insane. In other words, insanity is acquired and the result of individual stress and strain at least five times as frequently as it is inherited. We have absolutely no rational or statistical basis for gloomy predictions that, at present rates, within a couple of centuries more, we shall all be shut up in asylums with nobody left to support us and pay the taxes. The apparent increase of insanity of recent decades is probably only "on paper," due to better registration.

To put it very roughly, probably ninety-eight per cent of us are so born, thanks to heredity, that the possibility of our becoming insane, even under the severest stress, is almost infinitesimal. Of the two per cent born with this taint, this possible tendency to mental unbalance, only about one-tenth now become completely insane,[1] and this percentage might be greatly diminished by general sanitary improvements. Our alienists now claim that, by checking the reproduction of the obviously unstable, and careful hygienic treatment and training of the predisposed two per cent, insanity is almost as preventable as tuberculosis.

In fine, from all the broad field of pathology, the mists of tradition which have dimmed the fair name and reputation of heredity are slowly but surely lifting, until we now behold it, not as our worst enemy, but as our best friend in the prevention of disease and the upbuilding of the race.