CONTROL OF HEREDITY: EUGENICS 437 



for useful citizenship will be prohibited by law 

 in all the States. Our immigration laws al- 

 ready exclude such aliens, and the number of 

 persons of the types named who seek legal 

 consent to marry is not large so that it need 

 not be expected that such laws will quickly 

 improve the general population. If in addi- 

 tion such persons are either segregated or 

 sterilized the danger of their leaving illegiti- 

 mate offspring will be removed; such pre- 

 cautions have been taken in certain of our 

 States and will probably become general, 

 though at present few of the laws on this sub- 

 ject are strictly enforced. 



The study of heredity shows that the nor- 

 mal brothers and sisters, and even more distant 

 relatives, of affected persons may carry a re- 

 cessive defect in their germ plasm and may 

 transmit it to their descendants though not 

 showing it themselves. It will be more diffi- 

 cult, perhaps an impossible thing, to apply 

 rigidly the principles of good breeding to such 

 persons and to exclude them from reproduc- 

 tion ; but if in each generation those persons in 

 whom this recessive trait appears are prevented 



