Corio, pp.

292 et seq., contain the details.
In the despotic families of Italy, as already hinted, there was a progressive tendency to degeneration.

The strain of tyranny sustained by force and craft for generations, the abuse of power and pleasure, the isolation and the dread in which the despots lived habitually, bred a kind of hereditary madness.[1] In the case of Giovanni Maria and Filippo Maria Visconti these predisposing causes of insanity were probably intensified by the fact that their father and mother were first cousins, the grandchildren of Stefano, son of Matteo il Grande.

Be this as it may, the constitutional ferocity of the race appeared as monomania in Giovanni, and its constitutional timidity as something akin to madness in his brother.

Gian Maria, Duke of Milan in nothing but in name, distinguished himself by cruelty and lust.