frank law
noun(Frank-Star-ling law)
a statement in physiology: the strength of the heart's systolic contraction is directly proportional to its diastolic expansion with the result that under normal physiological conditions the heart pumps out of the right atrium all the blood returned to it without letting any back up in the veins —called also Frank-Starling law, Frank-Starling law of the heart, Starling's law