HEREDITi" 201 



In another case, a girl blind from aniridia was amazed to leam, upon 

 consulting a eeneticist, that half of her children of both sexes would be 

 expected to have the abnormalirv*. 



Fifth, a knowledge of human heredity- mav furnish the basis for ad- 

 \nce on prospective pregnancies. A voung man recentlv came to us for 

 adnce on a family histor\- of psoriasis, a skin disease. His father and grand- 

 father had the disease, as did several brothers and sisters and some nieces 

 and nephews. The young man's \^ ife was then pregnant. After becoming 

 pregnant she had learned of and seen the skin affliction of her husband's 

 relatives, which in the case of the girls and women, prevented the wearing 

 of sleeveless or low-necked gow ns. The voung wife became obsessed with 

 the idea that her child would have psoriasis. It preved on her mind to 

 such an extent that she was in danger of a nervous breakdown. Close ex- 

 amination of the familv histon* revealed that in this family the psoriasis 

 never appeared in a child unless one of the parents showed it. Onlv cer- 

 tain members of each familv showed it, although ail came in contact with 

 it. It was apparently behaving as a dominant character. Since the young 

 man in question was entirely free from the disease, it was possible to assure 

 his %\"ife that there was no danger of the child's inheriting: the condi- 

 tion. 



SLxth, a generic knowledge can provide the necessan* information for 

 setting up eugenic and euthenic programs for the protection of societ\% 

 a problem in which every citizen should be able to take an intelligent part, 

 based upon experimental data, not on opinions, prejudices or the exag- 

 geration of the uncertainties. 



Seventh and last, there is even' indication that with the discovery- of 

 more test factors of the sort exemplified by the blood agglutinogens, the 

 taste deficiencies and others which can be determined in early childhood, 

 we shall evenraaUy be able to predict in children the probabilit\- of the 

 occurrence of latent genetic diseases and abnormalities which may prove 

 to be closely linked in inheritance with such test factors. 



The various kinds of hereditary behavior now known are so compli- 

 cated that their undersranding requires a certain amount of study. This 

 means that no one is justided in stating on his own responsibilirv that a 

 given trait in man is or is not conditioned by hereditar\- factors unless: 

 (i) He is thoroughly familiar with the known kinds of hereditary* be- 

 havior. (2) He is familiar with the character under discussion in all its 

 varving manifestations. (3) He has carefully investigated the character in 

 a scientific manner from a genetic standpoint. This often involves the 

 cooperation of geneticists, physicians, dentists and ps\'cholcgists. 



As in other sciences any h\"pothesis of heredity, tiesides accounting for 

 the facts at hand, must stand the acid test of predictive value. 



In order to apply a knowledge of heredirv" to practical problems in 

 human beings, certain fundamental conclusions must be srranted. Among 



