THE INHERITANCE OF FAMILY TRAITS 139 



Hair-coat Color. — Ordinarily the hair of the scalp is of 

 uniform color but in man, no less than in horses, a piebald 

 condition is possible. This shows itself in locks of white 

 hair in the midst of a prevailing brown or red. This spotted 

 condition is due to a definite positive factor, even as in the 

 coat of mice, and two parents who lack spotted hair-coat 

 will have only uniform-coated children. This is illustrated 





UEiii 



Fig. 112. — Inheritance of monilithrix-^a positive character. Black s3anbols 

 represent affected individuals. Anderson. 



in the pedigree (Fig. 113) frOm Gossage. The hair-coat also 

 varies in thickness and that this quality runs in families 

 can hardly be doubted (Fig. 114). 



c. Nails. — Hereditary nail defects are almost always as- 

 sociated with hair defects, as in the cases of hair peculiari- 

 ties already described. One family pedigree must suffice 

 for nail and hair defect (Fig. 115). 



d. Teeth. — ^As is well known each half of either jaw has 

 typically 2 incisors, 1 canine, 2 bicuspids and 3 molars. 

 To this formula there are, however, exceptions and these 

 exceptional conditions may run in families. Thus McQuillen 

 records a family in which father, son and grandson lacked 



