296 OTTO L. MOHR 

was found to be a hereditary one and that it was transmitted directly 
from parents to children. Apparent deviations from this rule are in 
the whole literature, dating back to 1857, mere exceptions. And in 
these cases the malformation was always present in one of the parents 
of the individual who transmitted th® abnormality. 
From what we with certainty know concerning the mode of in- 
heritance of these malformations only the following facts shall here 
be mentioned: 
1. When a person suffering from such an anomaly begets off- 
spring with a normal individual, we will expect half of the children 
to exhibit the malformation. 
2. A person suffering from such a malformation has inherited 
the anomaly from one of his parents '. 
In the present case we are accordingly justified in the following” 
assumptions: 
Karen Hansen’s son Ole Kristian has inherited his malformation 
from one of his parents. The hands and feet of Karen Hansen are 
entirely normal. Her father and mother and her seven brothers and 
sisters have, according to the information obtained, normal hands. 
Her son must accordingly have inherited the malformation from his 
father. 
The following possibilities consequently present themselves: the 
child has either inherited the malformation from Hans Olsen or from 
another man suffering from the same abnormality. 
Under these conditions it was of interest, if possible, to find out 
from whom Hans Olsen had inherited his malformation. I examined 
his mother, Anna Olsen, and found that her hands were normal. 
Close interrogation concerning her relatives (father, mother, two bro- 
thers and sisters, three half-brothers and sisters) brought out the fact 
that no members of her family are known to have had malformed 
hands. It must accordingly be assumed that Hans Olsen has inherited 
the malformation from his father Kristian Johnsen. His mother has 
not observed that the latter had malformed hands, but importance 
cannot be attributed to this fact, since her acquaintance with Kristian 
Johnsen clearly has been very superficial (cf. her information in the 

church register quoted above — occupation: first » travelling agent», later 
' The facts already presented may explain why it was in this case regarded 
superfluous to bring under discussion the question of the first occurrence of the 
mutation. 
