If the debt is one which bears interest, and the principal of the debt is paid under an agreement on the part of the creditor to forego his claim for interest, a question is presented which is in some respects different from the ordinary case of payment of part of a liquidated and undisputed claim as consideration for the creditor's promise not to enforce his claim for the balance. If the original contract does not provide for the payment of interest in express terms, and the interest is allowed by law, such interest is often regarded as an incident of the principal debt; and, accordingly, payment of the principal debt, which is accepted as a full discharge of such principal debt, is said to discharge the creditor's right to recover the interest, since this right is merely incident to his right to recover the principal.1 Acceptance of the full amount due from a county treasurer, without interest, has been held to be a discharge of a claim for interest.2 In other jurisdictions, interest which is given by statute is regarded as a part of the original obligation and not as a mere incident, and recovery of such interest may be had after payment of the principal debt.3 If, however, the contract contains an express provision for the payment of interest, such interest is as much a part of the contract obligation as the obligation to pay the principal debt, and payment of the principal debt is not consideration for the promise of the creditor to forego his right to recover the unpaid interest.4