THE INHERITANCE OF FAMILY TRAITS 137 



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5 



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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. 



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io 



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

 bols) — proof of its positive nature. 4iV, four normals. Gossage, after Riz- 

 ZOLI, 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. 



