HEREDITARY TYPE OF CHARACTER STUDIED. 61 



It is hardly necessary to emphasize further the hypothetical character 

 of the interpretation here given. In human material where experiments 

 are excluded the only way is to test whether the carefully collected 

 data are in accordance with the principles sufficiently well established 

 through experimental genetic work. This is what has been done here 

 and the result is positive. 



VII. SUMMARY. 



The investigation deals with a symmetrical shortening of the second 

 phalanx of the second fingers and toes inherited within a Norwegian 

 family, some members of which emigrated to North America. 



The malformation is always restricted to this phalanx only, a rela- 

 tion which makes the character especially favorable for genetic investi- 

 gation, since an exact numerical expression for the character studied 

 can be obtained by direct measurements from the radiographs. 



The hands and feet are in every other respect perfectly normal. The 

 affected individuals show no shortness of stature. 



The anomaly manifests itself under two distinctly different somatic 

 types, one " slightly" shortened, so-called B-type, which is generally 

 overlooked by the affected individuals, and one very "much" shortened, 

 so-called B !-type, which is very striking in its somatic appearance. 

 No case of an intermediate condition has been observed. 



In the affected phalanges of the B-type there is no premature ossi- 

 fying of the epiphysial cartilages. Radiographs from hands of children 

 having the B !-type brachyphalangy demonstrate at the age of 12 years 

 a total ossification of the epiphysial cartilage of the affected phalanx. 



The inheritance of the malformation is followed without any break 

 through 6 generations, including and descending from an individual 

 born in 1764. The lines descending from one affected daughter and 

 one affected son of this individual form the main subject for the present 

 investigation. Within these lines every individual is recorded. In 

 addition, several families belonging to the IV, V, and VI generation, 

 descending from another affected son, are discussed. 



A detailed family record is presented with exact information also 

 concerning the earlier generations. This was possible, because the 

 family owns an old "Family book" with elaborate information con- 

 cerning each individual belonging to the earlier generations. 



The photographs of brachyphalangy cover 5 generations, the radio- 

 graphs cover 4. 



The brachyphalangy is inherited as a dominant, not a sex-linked 

 character. The numerical ratio between the affected and unaffected 

 individuals in the offspring of brachyphalangous members of the 

 family is in accordance with the theoretical expectation. 



