Page:Popular Science Monthly Volume 15.djvu/459

Rh only made obvious now and then before development by some mild aggravating cause, such as, when toward dyspepsia, by slight sensations of discomfort after hearty meals; when toward tuberculosis, by frequent signs of catarrh after ordinary weather-changes.

Not so much by plain evidences to the senses as by mental analysis can the reality of a struggle between a diathesis and reversion to the normal type be apprehended. Yet it is only the vis medicatrix naturæ of medical writers carried from the very obvious in acute disease to the less perceptible in chronic, and to the imperceptible in the diathetic. Although the opinion is very generally entertained that those who inherit a diathesis should be careful as to their mode of life, what effect there is on practice is commonly more injurious than beneficial. This arises from the lack of expert supervision, and the sway of some popular traditions as shallow as they are unsound. More frequently does their observance act as aids instead of hindrances to the development of an inherited dyscrasia. Then the observance of the true conditions which favor reversion in an inherited diathesis require no little judgment, self-denial, patience, and intelligence. In acute disease the physician and nurse see that the conditions of reversion are duly observed. Reputation, love, and alarm are all brought to bear for their enforcement. In a diathesis none of these are evoked until the development of all its signs renders the fact apparent that the fatal work has reached its culminating stage. The diathetic subject while in good health is himself indifferent and incredulous as to his danger. For the young to be always as careful of their health as an invalid, in other words, not to live and do as the careless multitude, presupposes unusual self-denial and discretion. Obstacles like these not only thwart the principle of reversion, but contrariwise strengthen and evolve abnormal variations.

Advantage being carefully taken of reversion in acute disease, less so in chronic, and scarcely at all in diathetic, that the eradication of unfortunate inheritances should have received so little credence is the natural outcome of the prevailing ignorance or neglect of the conditions. It is well, however, to bear in mind that this prevailing belief is simply and wholly the result of antecedents as they are and have been, not as they might and should be.

The instances in which the operation of the law of reversion has had anything like an unimpeded sway are far more commonly casual than designed. Circumstances render a change of environment and habits of life necessary or desirable, and these may happen to include its favoring conditions, or they may not. Those who recover from the tendency to an abnormal inheritance through intelligent design ought to be found, if anywhere, in the ranks of the medical profession, and especially among those of them who have given the science of health no little attention. A work assigned me by the American Medical Association brought some statements under my eye which confirm this