subjection are the existing taints or defects of blood, and the continued application of their genetic causes. The third factor is what in political phrase "holds the balance of power." The tendency to the maintenance of durable types is in limine more potent than abnormal variations, else recovery would be the exception instead of the rule. But, if the genetic influences of a defect or of an abnormity be kept in continual action after its inception, the ultimate triumph of reversion is a very rare outcome. Great care in acute diseases is commonly taken that the third factor shall not turn the scale against the tendency to reversion, far less is expert systematic supervision as to this brought to bear in chronic disease, while in the diathetic there is as a rule worse than a fitful, or no care—the misjudged application of causes best calculated to increase and intensify the defect or taint in the blood. In illustration of the statement in reference to acute disease, take a case of pneumonia, the result of a protracted out-door exposure to a sudden fall of temperature, with an abundance of atmospheric humidity. Suppose these genetic conditions continued throughout the attack, the likelihood of reversion gaining the mastery would be reduced to a very small ratio. Yet this is the very course generally adopted by those who have a diathetic defect in their blood, actually oftentimes under the belief that it is the best mode of hindering the full development of a dreaded inheritance. Take for example that of pulmonary consumption. Its leading genetic causes are, an in-door sedentary life, unwholesome food for the stomach, and above all depraved and unwholesome air-food for the lungs. Yet the father and mother with this taint in their and their children's veins, realizing that their boys and girls are delicate, from the moment of birth upward seclude them far more than ordinary in close, ill-ventilated rooms, they coddle and pamper them with unwholesome delicacies, and in effect carefully attend to the very conditions which secure weak and foul air as nutriment for their lungs and blood. Thus it is that the precise causes which originate the defect are with more than ordinary assiduity kept in constant action, and the tendency to reversion utterly overwhelmed.
Every candid person will acknowledge that this is no fancy picture, but a true outline of the practices in nearly every household which has such a shadow over it, so that, if the complete supremacy of reversion over a diathesis is not often seen when compared with the frequency with which it gains the mastery over acute disorders, the difference in results is what might be anticipated, as the unfavorable influence of a third factor is brought to bear on the former and not on the latter. The power of reversion in acute disease is readily discerned, the necessity of observing favoring conditions well known; they are under expert supervision and not difficult to carry into effect. Precisely the opposite is true concerning a diathesis. In chronic disease the struggle between reversion and morbid tendency is often so mild and slow as to be almost imperceptible; in the diathesis it is as a rule entirely so,
