THE INHERITANCE OF FAMILY TRAITS 137 



If 



Fig. 110. — Pedigree of a family with tylosis (black symbols). Note that 

 all affected persons have at least one parent affected — showing that tylosis 

 is due to a positive determiner, Unna, 1883. 



Fig. 111. — Pedigree of a family with tylosis palmae plantaris (black sym- 

 bols) — ^proof of its positive nature. 4Ar, four normals. Gossaqe, after Riz- 

 20LI, 1907. 



one was on the thigh), and Iwai (1904) cites many cases of 

 a mother and five to one of several children who possessed 

 supernumerary pectoral nipples. 



