418 THE NEW INDIVIDUAL Part IV 



melanin play key parts. Melanin is present in all human eye colors from black 

 to pale blue (Chap. 17). Black and brown eyes occur in a majority of the 

 human race, and the genes for dark pigments were probably the pre-eminent 

 ones in early human history. 



Table 20.1 

 Certain Traits Inherited in Man 



Mental Disorders. A number of mental disorders are known to be in- 

 herited. The inheritance of a few of these is known; for others it is suspected 

 and still being studied. Superior mental ability and special aptitudes run in 

 families but are also strongly influenced by upbringing and other surroundings. 



Eugenics 



The increasing knowledge of human inheritance has brought with it numer- 

 ous plans for racial betterment. Eugenics includes study, plans, and action for 

 the betterment of the human race. Eugenics may be negative with education 

 and regulations against the reproduction by which feeble-mindedness, insanity, 

 and appalling physical defects are continued. Positive eugenics encourages the 

 continuation of the qualities of health and good citizenship. 



The greatest problem of negative eugenics is feeble-mindedness since 5 per 

 cent of the American population has an intelligence rating of 70 or much less. 

 This group includes: paupers due to laziness and inability; criminals, large 

 numbers of them hopelessly defective; many persons who have grown up in 

 institutions for defectives and must remain there; and great numbers of morons 

 who hang to the fringes of life but contribute nothing but inertia and children 

 like themselves. 



The reproduction of definitely unfit persons has been to some extent pre- 

 vented by segregating them in institutions and by sterilization. However, con- 

 finement is a heavy financial load on the state and is unhappiness for the in- 

 dividual. Sterilization, on the other hand, is a simple operation; severance of 

 both sperm ducts of the male (Fig. 18.5) or both oviducts of the female (Fig. 

 18.10). It prevents the outlet of the sex cells, but in no way aflfects the sensa- 

 tions or health of the person. The operation is performed upon the advice of 



