I04 



HEREDITY AND EUGENICS 



this condition is recognised in each generation as a 

 mark of ro^^al distinction ! Ballowitz quotes from 

 the French hterature (1863) the case of an isolated 

 village in the Departement d'Isere, in which, through 

 inbreeding, nearly all the inhabitants had six fingers 

 and toes. Later, owing to increased communications, 

 marriages with normals took place, and the extra 

 fingers and toes in newborn children became smaller 

 and fewer, finally disappearing altogether. This is 

 a good example of the " weakening " and disappear- 

 ance of an abnormality through exogamy, but brachy- 

 dactyly does not appear to be affected in this way. 



D X 



6-6 

 ^6-6 



° □ X ^5 



1 1 I I I I 



6-6 



10 Other children, all having 6 Fingers and toes. 



m il«, X o 



66 



65 

 6-5 



1 6-6 

 \6-6 



i6-6 



w 



iff 6 i 



6-6 

 6-6 



i66 



I 6-6 



V — 



Twins 



^6-6 



mee 



Zerah 



^^ 



Fig. i8. — Pedigree of Hexadactyly. 



If such weakening of a character like hexadactyly 

 can take place through exogamy, it is an important 

 hereditary principle which requires further elucida- 

 tion, especial^ in comparison with conditions like 

 brachydactyly where no weakening effect is observed 

 even after many generations of outcrossing. 



An interesting hexadactylous family is described 

 by Carlisle (1814). Zerah Colburn, the son of Abiah 

 Colburn, born in \^ermont, was brought to London 

 on account of his " extraordinary powers in arith- 

 metical computations from memory." He had a 

 supernumerary little finger on each hand, and an 



