2 74 



Heredity and Eugenics 



ha\-e affected children (in the illustrative case nothing is 

 known about one of the t^\'o parents). When one parent 

 only is affected about half of the children are affected, since 

 each affected person is simplex. 



Again, some family strains exhibit imperfection of hair 

 or even baldness associated with imperfect nails (Fig. 8i). 

 Here there seems to be a determiner that stops the develop- 

 ment of these organs of the skin. Normal persons are with- 

 out this determiner and so cannot have affected children. 



D 



D 







r >/yr /■//>/• 



-n 1 



T 



o 



f5*¥¥S^¥6 [5i SoWl tf*o^b 



*¥¥ft 



Fig. 8i. — Pedigree of a family with poorly nourished nails and hair (black 

 ?\-mbols). — XicOLLE ET Halipre. 



Still another peculiarity of the skin is due to a positive 

 character. This is a thickening of the palms of the hands 

 and soles of the feet (Fig. 82). Here all, or half, of the 

 children of an affected parent are aft'ected, but normals of 

 the strain, who marry outside of the family, will have no 

 thick-skinned children. 



In some persons the color of the hair of the head is not 

 uniform, but there are patches of white hair in the midst 



