The delivery of three hundred dollars to the plaintiff by the defendant’s testator was either a payment, or a loan, of that amount. It could not possibly be both at the same time. As the parties saw fit, for reasons satisfactory to them *52selves, to put the transaction in the form of a promissory note, the defendant had a right to treat it. as such, and to enforce it accordingly. But having done so in a suit in her own favor, she cannot be permitted, in another suit between the same parties, in which she is defendant, to take the opposite ground and maintain that although in form a promissory note the transaction was in substance and effect a payment. To allow her to do so would be to give her an unjust advantage which no rule of law can sanction. What she sees fit to call a promissory note in one case she cannot treat as a mere receipt in the other, and the ruling of' the court to that effect was right. We see no valid ground for disturbing the verdict. Billings v. Billings, 10 Cush. 178. Hooker v. Hubbard, 102 Mass. 239. Sherer v. Collins, 106 Mass. 417.
Exceptions overruled.