CASUS amissionis, in Scots law. In actions of proving the tenor of obligations extinguishable by the debtor's retiring or cancelling them, it is necessary for the pursuer, before he is allowed a proof of the tenor, to condescend upon such a casus amissionis, or accident, by which the writing was destroyed, as shews it was lost while in the creditor's possession. See SCOTS LAW, title, Actions.