When a mortgagor conveys a part of the mortgaged premises as free from the mortgage, his grantee acquires an equity against him to have the part of the premises not conveyed first applied to the payment of the mortgage debt, and neither the mortgagor nor a subsequent purchaser from him can, upon paying the debt, call upon such prior purchaser for contribution ; and a mortgagee, who has notice of such conveyance, cannot defeat the equity of the purchaser by releasing from the mortgage other parts of the premises, but must account, in enforcing his lien upon the lands so conveyed, for the value of the lands released. Parkman v. Welch, 19 Pick. 231. George v. Kent, 7 Allen, 16. George v. Wood, 9 Allen, 80. Beard v. Fitzgerald, 105 Mass. 134.
The plaintiff was a purchaser with warranty from mortgagors. The defendant, the mortgagee, released a part of the mortgaged premises, which, after the conveyance to the plaintiff, the mortgagors had conveyed to one Smith, who had notice of the deed to the plaintiff, and who is not made a party to this bill. The value of the part of the premises released to Smith, with the part *467remaining unsold, is sufficient to pay the mortgage debt; and the plaintiff asks that the defendant may be enjoined from foreclosing the mortgage upon the part held by the plaintiff.
The answer to the plaintiff’s claim is, that the defendant is not merely the mortgagee of the whole mortgaged premises, bound to release the whole upon payment of the whole debt, and whose release of a part, upon payment of a part of the debt, would be a merely voluntary act; she "was also in the position of owner of as many parcels of land as the mortgagors might choose to divide the premises into, bound by special agreement to.release her interest in each separate parcel on the payment of a specified sum. This agreement of hers was for the benefit of the estate of the mortgagors, and the right to enforce it passed to purchasers from them. Both the plaintiff and Smith had the right to a release as against the defendant. The plaintiff’s case rests upon the ground that, from the relation between himself and Smith as prior and subsequent purchasers from the mortgagors, he had an equitable right to prevent Smith from availing himself of this agreement. If he had such a right, he could have asserted it before the release was given, in proceedings to which both Smith and the defendant should have been parties, but he could not require the defendant to set it up as a defence against her own "covenant. Even if it would have been a defence to Smith’s demand upon the defendant for a release, that the plaintiff had rights against Smith which might be impaired by the release, the defendant was not bound to make that defence; she was under no obligation to set up and litigate the plaintiff’s rights for him. The plaintiff himself had ample opportunity to pursue his remedy against Smith, and it would be inequitable to allow him to put the burden and responsibility of establishing it upon the defendant. ■ It is not necessary to consider what the equities are as between the plaintiff and Smith, nor whether any remedy the plaintiff had has been at all impaired by the release to Smith. Assuming that the plaintiff has all the rights that he claims to have against Smith, and that the effect of the release was to deprive him of the benefit of them, they were rights against Smith, to be established and enforced against him by the plaintiff, and which the defendant was under no obligation to assert as a defence against the performance of her own *468agreement. The defendant is not obliged, before she can foreclose her mortgage, to adjust the equities between the plaintiff and Smith, and she has not cut herself off, by giving the release, from enforcing the mortgage on the land not released. The plaintiff can procure a release by the payment of the specified sum, but he has not offered to do that; and his bill is brought solely to compel a release of his land from the mortgage without any payment by him. In the opinion of a majority of the court, he has shown no right to this relief. The plaintiff appears to have a right to redeem upon the payment of the agreed sum per foot, and the bill is to stand to allow him to move to amend by ma.Tring it a bill to redeem. If such amendment is not allowed, the bill to be dismissed, with costs. Ordered accordingly.