INHERITANCE OF HUMAN CHARACTERS 469 
individuals on a scale of 10. Ten represents very high ability, as 
determined by the comparative amount of space and laudation given 
to the individual in such standard works as Lippincott’s Biographical 
Dictionary. Five out of eight of Isabella’s great-grandparents rank 
very high. John the Great of Portugal, twice her great-grandfather, 
has a grade of 10. John of Gault, twice her great-grandfather, has a 
grade of 8, as does also John of Castile, while Henry ITI of Castile, one 
of her grandparents, is designated the model king. Ferdinand I of 
Aragon, the grandfather of Ferdinand, is a brother of this same 
Henry III of Castile, and is also an exceedingly able king. Of the 
children of Ferdinand and Isabella, most were mediocre or distinctly 
inferior. Joannawasinsane. In the next generation, however, appears 
Charles V, whose reign marked the acme of Spain’s greatness, partially 
due to his own ability, partially due to the momentum of those move- 
ments that were instituted by his illustrious grandparents. Charles V 
married his own cousin, as did also John III. Children of these two 
matings married, and Don Carlos, child of this latter marriage, was 
madly depraved and cruel. 
When insanity and brilliancy are found in the ancestry it seems 
merely a matter of chance as to whether the determiners for greatness 
will be thrown together in the union of sperm and egg or those for 
insanity. We can predict with some certainty,that, in a large number 
of offspring, ability will reappear and insanity will reappear, but just 
what individual each will strike it is impossible to prophesy without 
knowing much more definitely the nature of the germ plasm involved. 
One may say that the convergence of a number of lines of descent from 
great ancestors toward one individual makes it probable that he will 
be exceptionally able. 
This is nowhere better illustrated than in the family tree of 
Frederick the Great of the Prussian house of Hohenzollern, as will be 
seen from the chart on page 470. Of his great-grandparents, three 
scale 10, one 9, one 8, two 7, and one 6. Not one is below mediocrity, 
and the majority are of very high grade. Of his fourteen ancestors 
back three generations, only one is distinctly inferior. Of his brothers 
and sisters, four are distinctly great, three mediocre, and one inferior. 
It is interesting to trace the effect of the mating of such splendid 
stock with another brilliant line, that of the Swedish royal house. 
Gustavus I, or Gustavus Vasa, is another instance of the brilliant 
mutant, with some taint of neurosis. He married a gentle and tactful 
princess; their son Charles [X was a very able man, although of their 
