Bapallo, J.

As the order of the General Term does not state that the reversal was on any question of fact, it cannot be sustained unless it be made to appear that some error of law was committed by the trial judge. The ease came before the General Term on appeal from the judgment, and exceptions, only, and it had no discretionary power to order a new trial in the absence of legal error.

The only exception to rulings at the trial, which has been argued, is that taken by the defendant to the exclusion of the question to him, on his being -recalled after the plaintiff had rested, whether he had had conversations with Mr. Miller in 1870 or 1871, at his office.

The question of fact at issue was whether the defendant had notified Mr. Miller of the sale of the mortgaged premises to Leslie, and had requested Miller to proceed to collect the amount which might become due -upon the mortgage at maturity. The defendant Davies, who had the affirmative of that issue, testified in his own behalf that he sold the property to Leslie in October, 1871, and that at about the time the first or second installment of interest on the mortgage became due, after the sale, he went to Miller’s office and there told him that he had sold the property to Leslie, who had assumed the payment of the mortgage, and asked Miller to collect the interest of Leslie, and also the principal when it became due, and if he did not pay it to foreclose the mortgage at once, and that Miller assented to that proposition, and that from the time of that interview until the *419 6th of January, 1877, he thought he had no further interview with Miller or the plaintiffs.

Miller being called on the part of the plaintiffs testified positively that no conversation of that kind ever took place. On cross-examination he was asked whether he had any conversation at all with the defendant Davies in 1870 or 1871, and he answered none that he remembered ; that he might have had conversations that he did not recollect, but none of the nature testified to by the defendant.

After, the plaintiffs had rested, the defendant Davies was recalled and asked whether he had had any conversation with Mr. Miller during the years 1870 or 1871, at his office. This question being objected to on the ground that the witness had already testified, was excluded, and exception taken.

The witness was then permitted to assert the positiveness of his recollection of the conversation to which he had already testified and to state the circumstances which enabled him to be positive.

We cannot discover any legal error in the ruling excepted to. The court went further than strict rules required it to go, in permitting the defendant to be re-examinéd as to his original statement. This however was purely discretionary. If the question which was excluded was intended to refer to this conversation, the exception is groundless. If the question related to any other conversation the exception is equally without foundation. Unless the conversation sought to be proved was material and tended to maintain the issue on the part of the defendant, it was irrelevant. If it was material, then it ivas entirely within the discretion of the court whether or not to permit the inquiry. The defendant had been examined in support of his allegation of notice and request to foreclose. He had testified to a conversation with Mr. Miller upon which he relied, and that he thought there was none subsequent. Having rested his case, and the plaintiff having closed his testimony, the defendant had no legal right to re-open his own case and introduce evi *420 dence to sustain his defense, which he might have introduced when the case was with him. No rule for the conduct of trials is more familiar than that the party holding the affirmative is bound to introduce all the evidence on his side before he closes. (Hastings v. Palmer, 20 Wend., 225.) He must exhaust all his testimony in support of the issue on his side, before the testimony on the opposite side has been heard. (Ford v. Niles, 1 Hill, 301; Rex v. Stimpson, 2 Carr & P., 415.) He can afterwards introduce evidence in rebuttal only. Rebutting evidence in such cases means, not merely evidence which contradicts the witnesses on the opposite side and corroborates those of the party who began, but evidence in denial of some affirmative fact which the answering party has endeavored to prove. (Silverman v. Foreman, 3 E. D. Smith, 322; 2 Carr & P., 416.) In the ptresent case, after having testified to one conversation, which was denied on the other side, the defendant was not entitled as matter of right to prove another as to which he had not previously testified, even though it tended to support his original statement. This was not evidence in rebuttal. The testimony on the 2>art of the plaintiff was that other conversations might have been had, but that no conversation of the nature testified to by the defendant ever took place. This was a mere denial, and not proof of any affirmative fact which the defendant had the right to rebut. These rules may in special cases be departed from in the discretion of the trial judge, but a refusal to depart from them is no ground of exception.

The findings of fact of the trial judge disclose no error in his conclusions of law. He finds no notice to the mortgagees of the conveyance from Davies to Leslie, and no request to the 2)laintiffs to foreclose, and there is no uncontroverted evidence in the case which required him to find those facts.

Whether, if they had been found, the defendant would have been entitled to judgment, we do not now decide. But clearly, in the absence of those facts, the defense cannot be sustained; As between the plaintiffs and the defendant *421 Davies; he was the principal debtor, and the plaintiffs were not bound to look after the taxes on the mortgaged premises. We have held that where the mortgagor conveys to a third party, who assumes the mortgage, the relation of principal and surety arises between the mortgagor and his vendee; and that after notice of this relation, the mortgagee is bound to observe it and abstain from doing any act to the prejudice of the mortgagor, or which would impair his recourse against the mortgaged premises in case he should be obliged to pay his bond and be subrogated to the mortgage. The mortgagee in such a case, after notice, cannot with impunity release the land, or extend the time "of payment, or do any other act to the prejudice of the mortgagor; and the prohibited acts are determined by the law of principal and surety. (Calvo v. Davies, 73 N. Y., 215.) But the actual relation of debtor and creditor between the mortgagor and mortgagee cannot he destroyed by any act of the mortgagor alone, where the mortgage is given to secure the bond of the mortgagor. The courts have gone no further than to hold that, in cases like the present, the relation of creditor and principal debtor is so far affected that the mortgagee is bound, after notice of the equitable rights of the mortgagor as between himself and his vendee, to respect them, and do no act to their prejudice; and when he forecloses, the equities of the mortgagee will be protected in the order of sale. But the mortgagee may sue upon the bond in the first instance, notwithstanding the transfer of the land. This has often been decided. In Marsh v. Pike (10 Paige, 595) it was held that where a vendee of the mortgaged premises had assumed the payment of the mortgage, the mortgagor could not compel his creditor to foreclose, when there was no good reason why he did not pay his bond according to Ms agreement, and take an assignment of the bond and mortgage, and proceed against the land and the subsequent grantees thereof, for his indemnity; and that he could also proceed in equity to compel such grantees, as to whom he stood in the situation of a mere surety, to discharge the *422 debt, for his protection. The defendant Davies having no right to compel the plaintiffs to foreclose the mortgage, it is questionable whether a request to do so would have been of any avail. His request to collect the debt might have been answered by bringing an action against him on his bond ; and the necessity of this he could have obviated by voluntarily paying it and being subrogated to the rights of the mortgagee. It is, to say the least, doubtful whether a mortgagor thus situated has any remedy except to protect himself by watching the security; and if he finds that it is becoming impaired by lapse of time and the accumulation of interest and taxes, to take the steps pointed out in Marsh v. Pike, supra.

It is very clear however that, in the absence of notice of any change in the position of the mortgagor, and of any request to foreclose, a mortgagee out of possession may rely upon the personal liability of Ms debtor, and is not bound to look after or protect the mortgaged premises; and that if he forecloses the mortgage, the debtor is entitled to credit only for the net proceeds of sale realized by Ms creditor, after the deduction of all liens for taxes, etc., and remains liable .for the deficiency. In the numerous foreclosures which have taken place in this State since the organization of the Court of Chancery, no claim to the contrary appears ever to have been made, and we can perceive no foundation upon which such a claim can rest.

The order of the General Term should be reversed, and the judgment at Special Term affirmed, with costs,

All concur.

Order reversed and judgment affirmed.