COGNĀTI, COGNĀTĬO. The _cognatio_ was the relationship of blood
which existed between those who were sprung from a common pair;
and all persons so related were called _cognati_. The foundation
of _cognatio_ is a legal marriage. The term _cognatus_ (with some
exceptions) comprehends _agnatus_; an _agnatus_ may be a _cognatus_,
but a _cognatus_ is only an _agnatus_ when his relationship by blood
is traced through males. Those who were of the same blood by both
parents were sometimes called _germani_; _consanguinei_ were those
who had a common father only; and _uterini_ those who had a common
mother only.