S8 THE POPULAR SCIENCE MONTHLY 



the units of heredity. From this point of view we may say that 

 feeble-minded persons are such as lack one or more mental traits that 

 are socially important. 



From this definition it follows that mental defectives differ quanti- 

 tatively in the number of socially important traits that they lack and 

 qualitatively in the kind of traits and the degree of their social impor- 

 tance. Defectiveness in one important trait only may be called uni- 

 def ectiveness ; in two traits^ di-defectiveness and so we may have tri- 

 defectiveness up to multi-defectiveness. For example, cases are well 

 known of number-defectiveness, attention-defectiveness, memory-defect- 

 iveness, imagination-defectiveness, emotion-defectiveness, inhibition- 

 defectiveness, moral-defectiveness, occurring quite without other de- 

 fects. Well-known unit defects are word-blindness, figure-blindness, 

 word-deafness, tone-deafness and color-blindness. Any of the defects 

 may occur isolated or two or more of them together in one individual. 

 Such defectives are often not recognized as such, if the missing trait 

 or traits have little social importance; but if gentleness gives way to 

 cruelty or self-restraint to self-indulgence the uni-defective becomes a 

 " moral imbecile," and such a moral imbecile may be good at his school 

 work and bright and active in most ways. It is, however, the multi- 

 defectives that constitute the main problem of the feeble-minded; for 

 they are fairly common and are a constant drag on that school system 

 which is not adapted to their capacities. Yet among such may be 

 good mathematicians, musicians, mechanicians, etc. It is clear, then, 

 that " feeble-mindedness " is not a simple trait, but a convenient group 

 in which to put all of the socially inadequate. 



Can we, in the midst of this heterogeneity find any general " cause " 

 of defectiveness in its varied manifestations? It seems to me we can 

 discover such a cause by attending to various features of defectiveness. 

 First of all we have to recognize that these defects are in general 

 hereditary. There are family strains with color-blindness, stuttering, 

 word-blindness, number-blindness, tone-deafness, and so on. The 

 deficiency of the uni-defective comes from a defect in the germ-plasm 

 of one or both of his parents. In a multi-defective, likewise, all the 

 absent traits are the result of corresponding defects in the germ-plasm 

 of the parents. And if both parents be multi-defectives that combina- 

 tion of germ-cells will be rare indeed that results in anything but a 

 feeble-minded child. 



And, secondly, it is to be observed that " defects " are not patholog- 

 ical conditions; they are merely deviations from the normal condition 

 of the adult. For every person shows these defects at some stage of 

 his life and only gradually overcomes them. My nine-months-old son 

 can not talk, nor dress himself, nor attend to his animal needs. He is 



