138 HEREDITY IN RELATION TO EUGENICS 



b. Hair. — Peculiarities of hair, apart from pigmentation, 

 are not infrequent as family traits. Thus a family with 

 curled, woolly hair is described by Gossage, the curly condi- 

 tion being clearly dominant over its absence. Hair may be 

 entirely absent even from birth. Such a case is described by 

 Molenes (1890). There was brought to him a girl of 4 years 

 who was hairless from birth until 19 months old. She had 

 a brother who was bald at six and the mother lost her hair 

 at 19. Another case, described in the Medi-chirurgical Trans- 

 actions, is that of a boy of three who was nearly bald. His 

 sisters had normal hair but his mother had complete 

 alopecia areata from the age of six. 



A third case is that described by White who knew a family that came 

 from France to Canada. One grandfather was nearly hairless and the 

 nails were faulty; the parents were normal; but in the next generation of 

 6 sons and 2 daughters one daughter was almost hairless and the nails 

 abnormal in her and in two sons. This daughter married (presumably a 

 normal man) and had a son who at 19 retains on his scalp the nearly invis- 

 ible downy coat with which he was bom. His only sister has a thick, 

 downy scalp-covering quite different from normal hair. One of the uncles 

 of these children has a son of 9 and a daughter of 4; the latter was 

 born entirely without hair or nails. The data are not very full but the 

 fact that normals carry the trait indicates that it may be accompanied by 

 a definite defect in the germ plasm. Baer describes a family of ten chil- 

 dren of two normal parents of which one was born hairless and has con- 

 tinued so while three were born with heavy hair but lost it; in two cases 

 at 14 days and in one at 9 months. 



The form of the hair may show family pecuharities. Thus, 

 in some cases, it is thickened at intervals resembling a string 

 of beads — ^hence called "monihthrix." A pedigree of a 

 family of this sort has been recorded by Anderson (Fig. 

 112). Unaffected parents apparently yield only normals 

 and abnormal parents are usually simplex, so that about half 

 of the offspring have the new character. 



The facts of inheritance of curliness have been considered 

 on page 35. 



