In any judicial proceeding in Scotland, any fact relating to a bill of exchange, bank cheque, or promissory note, which is relevant to any question of liability thereon, may be proved by parole evidence: Provided that this enactment shall not in any way affect the existing law and practice whereby the party who is, according to the tenour of any bill of exchange, bank cheque, or promissory note, debtor to the holder in the amount thereof, may be required, as a condition of obtaining a sist of diligence, or suspension of a charge, or threatened charge, to make such consignation, or to find such caution as the court or judge before whom the cause is depending may require. This section shall not apply to any case where the bill of exchange, bank cheque, or promissory note has undergone the sesennial prescription.