186 



EVOLUTION AND GENETICS 



American family of this sort, and Drinkwater that 

 of a British family, and later of a second family that 

 migrated from America back to England. As seen 

 in figure Qo, the fingers of the brachydactyl hand 

 are short owing to the absence of the middle segment 

 of each finger. The fingers are about half normal 

 length. A short-fingered man marrying a normal 

 woman transmits the defect to half of the children. 

 The character is dominant {jig. 67). There are no 

 recorded cases of the marriage of two short-fingered 

 persons and the pure (or double) dominant char- 

 acter is unknown. There is a possibility that such an 

 individual might not be viable. 



OB 



^ t^~i I 



S^ 





I 



II 





III 





cS^rtrt^mMl 



V 



Fig. 67. — Pedigree chart of the inheritance of Brachydactyly. 

 {After Farabee.) 



Drinkwater has also recorded other cases of minor 

 brachydactvlv in which the finoers are less short- 

 ened. Several other cases in which one or more of 



