442 THE POPULAR SCIENCE MONTHLY. 



subjection are the existing taints or defects of blood, and the continued 

 application of their genetic causes. The third factor is what in politi- 

 cal phrase " holds the balance of power." The tendency to the main- 

 tenance of durable types is in limine more potent than abnormal varia- 

 tions, 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 con- 

 tinual 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 re- 

 version, 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 cal- 

 culated 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. Sup- 

 pose 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 con- 

 sumption. Its leading genetic causes are, an in-door sedentary life, un- 

 wholesome food for the stomach, and above all depraved and unwhole- 

 some 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 origi- 

 nate 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 neces- 

 sity of observing favoring conditions well known ; they are under ex- 

 pert 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, 



