Except in case of some accident or calamity requiring their discharge, the jury shall not be discharged after the cause is submitted to them until they have agreed upon a verdict and given it in open court, unless by the consent of both parties entered in the minutes or unless at the expiration of such period as the court deems proper it satisfactorily appears that there is no probability of an agreement of five-sixths of them. Five-sixths of the jury may render a verdict in civil actions.