Book II, Of Things - I. Division of Things
If the wheat of Titus is mixed with yours, when this takes place by
mutual consent, the mixed heap belongs to you
in common because
each body, that is, each grain, which before was the property of one or
other of you, has by your mutual consent been made your common
property; but, if the intermixture were accidental, or made by Titus
without your consent, the mixed wheat does not then belong to you
both in common; because the grains still remain distinct, and retain
their proper substance. ...if either of you keep the whole quantity of
mixed wheat, the other has a real action [claim or suit] for the amount
of wheat belonging to him, but it is in the province of the judge to
estimate the quantity [amount] of the wheat belonging to each.