implied authority to fill blanks

Where a party to a negotiable bill of exchange or promissory note containing blanks, intrusts it to the custody of another...such bill or note, especially if it be indorsed in blank, or is made payable to bearer, carries on its face an implied authority, in the person to whom it is so intrusted, to fill up the blanks in his discretion; and, as between such party to the bill or note and innocent third parties, holding the bill or note as transferees for value, in the usual course of business, the person to whom it is so intrusted must be deemed to be the agent of the party who committed such bill or note to his custody; and the legal conclusion is, that in filling up the blanks he acted under the authority of that party, and with his approbation and consent.