Formerly there was a kind of obligation made by writing, and said to be contracted by the entry of a debt in a ledger; but such entries have nowadays gone out of use. Of course, if a man states in writing that he owes money which has never been paid over to him, he cannot be allowed, after a considerable interval, to defend himself by the plea that the money was not, in fact, advanced; for this is a point which has frequently been settled by imperial constitutions. The consequence is, that even at the present day a person who is estopped from this plea is bound by his written signature, which (even of course where there is no stipulation) is ground for a condiction. The length of time after which this defence could not be pleaded was formerly fixed by imperial constitutions at five years; but it has been reduced by our constitution, in order to save creditors from a more extended risk of being defrauded of their money, so that now it cannot be advanced after the lapse of two years from the date of the alleged payment.