In life they are commonly rhythmically opened and shut by a wavy movement.
Even small strips of the muscle of the heart, if taken immediately after the death of the animal, continue, when kept moist and warm and supplied with oxygen, to "beat" rhythmically for hours.
It seemed to her that something heavy was beating rhythmically against all the walls of the room: it was her own heart, sinking with alarm and terror and overflowing with love.
That shoulder rose and fell rhythmically and convulsively, but spadefuls of earth were already being thrown over the whole body.
One of his nails scratched her rhythmically, sending small streaks of pleasure through her.
Similar rhythmically contractile shell of Rostellaria rectirostris.
And suddenly the sequence of these thoughts broke off, and Prince Andrew heard (without knowing whether it was a delusion or reality) a soft whispering voice incessantly and rhythmically repeating "piti-piti- piti," and then "titi," and then again "piti-piti-piti," and "ti-ti" once more.