476. (12) As long as this relationship with a mistress continues, physical conjunction with the wife is prohibited. It is prohibited because in such an event, conjugial love, which in itself is spiritual, chaste, pure and sacred, becomes natural, defiled and stale, and thus perishes. Therefore, in order to preserve this love, it is proper that the relationship in taking a mistress for real weighty reasons (nos. 472, 473) be carried on with the one, and not with both at the same time.