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UNIVERSITY OF VIRGINIA PUBLICATIONS 



On the contrary the condition is due to the pecuhar shape- of the hallux nail. 

 The nail arches sharply over the side of the nail-bed (fig. 43), whereas 

 in the usual or normal condition the nail lies more nearly flat (fig. 44). 

 The condition of "ingrowing toe-nails" accordingly is coincident to an 

 anatomic variation in the shape of the nail. In the case of some of the 

 affected members of this family, including both the father (A) and mother 



0-r-« 



Al— 



O-T-a 





^5M5) 



Fig. 42 Onyxis. 



of B the condition appeared to a degree requiring surgical treatment; 

 similarly with respect to B, in whom the condition appeared before the 

 end of the first year, and before walking or wearing shoes. Moreover, in 

 the case of the father (A) there is present a decided tendency to lateral 

 arching of the nail on all fingers and toes. 



Fig. 43. 



Fig. 44. 



Onyxis is evidently recessive to the normal condition; otherwise two 

 normals, as the mother's parents, could not have abnormal offspring. More- 

 over, it is probably due to the presence of a determiner or factor; otherwise 

 two abnormals as the father's parents, could not have any normal offspring. 

 In view of the paternal history — which suggests dominance of the abnormal 

 — a complete explanation of the pedigree involves the assumption of degrees 

 of dominance. 



