THAYER, Circuit Judge,
after stating the case as above, delivered the' opinion of the court.
No exception is taken by the appellants to the decree of the circuit court, in so far as it directs a sale of the strip of land 15 feet in width *331fronting on Jackson street; but it is strenuously insisted by them that the decree was and is erroneous, in so far as it permits a sale of the remaining 85 feet of the mortgaged property which was purchased by the appellants from William R. Marshall, the mortgagor, on November 12, 1891. A critical examination of the answer to the hill of complaint has satisfied us that: this contention is based solely on the theory that by suing the appellants in the first instance to compel them to pay the sum of $10,000, being the two-thirds' of the mortgage debt which they had assumed to pay, ihe plaintiff company thereby adopted all the covenants contained in the deed of November 12, 1891, and became hound thereby to the same extent as Marshall, the grantor in such deed. The argument is, in effect, that the plaintiff in this manner made itself a party to Marshall’s covenant to warrant and defend the title to that part of the mortgaged properly which was conveyed to the appellants, except as against that part of the mortgage indebtedness, to wit, $10,000, which the appellants had assumed, and that it cannot he heard to assert a lien against the property which the appellants purchased, for that part of the mortgage debt, to wit, the sum of $5,000, which Marshall undertook to pay. Whether this theory is tenable depends very largely, we think, on the nature of the right which the plaintiff acquired, and afterwards enforced by a suit against the appellants, by virtue of their agreement with Marshall to pay a portion of the mortgage debt. In some cases it has been held, in substance, that, where the purchaser of an equity of redemption agrees with the mortgagor to pay the whole or a part of the mortgage debt, such a promise may he treated as a contract made by the mortgagor for the mortgagee’s benefit, which the latter may adopt as his own, and enforce by a suit at law. Fitzgerald v. Barker, 4 Mo. App. 105; Beardslee v. Morgner, Id. 139; Lawrence v. Fox, 20 N. Y. 268; Burr v. Beers, 24 N. Y. 178; Rogers v. Gosnell, 51 Mo. 466, and cases there cited. In the opinion of the learned judge of the trial court, which is found in the record, it is stated that this is the rule in the state of Minnesota. The prevailing doctrine, however, is that which is stated and approved in Keller v. Ashford, 133 U. S. 610, 623, 624, 10 Sup. Ct. 494, namely, that the right of a mortgagee to enforce the payment of a mortgage debt as against a grantee of the mortgagor who has assumed its payment does not rest upon any contract existing between the mortgagee and grantee which is enforceable by the mortgagee by a suit at law, hut is founded altogether upon the fact that, by virtue of the agreement to assume the mortgage debt, the grantee becomes primarily liable to pay the same, while the mortgagor, with respect to his grani.ee, is merely a surety for its payment. Such being the relation existing between the mortgagor and his grantee, it is held that the mortgagee may be subrogated to the rights of the mortgagor, and, by a suit in equity for that purpose, may compel the grantee to keep his engagement wiih the mortgagor by paying the mortgage debt. But as the right which the mortgagee thus acquires by virtue of the agreement of a third party with the mortgagor to pay the mortgage debt is purely equitable, and does not rest on privity of contract, it will not be enforced if, for any reason, the contract between the mortgagor and his grantee could not be enforced by the former *332in a suit at law. If reasons exist which would enable the grantee to successfully defend an action brought by the mortgagor for nonpayment of the mortgage debt, the same reasons will preclude the mortgagee from enforcing his equitable right. Crowell v. Hospital, 27 N. J. Eq. 650; Palmeter v. Carey, 63 Wis. 426, 21 N. W. 793, and 23 N. W. 586; Boardman v. Larrabee, 51 Conn. 39; George v. Andrews, 60 Md. 26; Biddel v. Brizzolara, 64 Cal. 354, 30 Pac. 609; Flagg v. Geltmacher, 98 Ill. 293; Figart v. Halderman, 75 Ind. 564; National Bank v. Grand Lodge, 98 U. S. 123; Halsey v. Reed, 9 Paige, 446; Pardee v. Treat, 82 N. Y. 385, 389; Coffin v. Adams, 131 Mass. 133, 137; Jones, Mortg. §§ 740, 770.
In view of the doctrine last stated, which is sustained by the great weight of authority, and is approved by the federal supreme court, we are unable to concede that the plaintiff company adopted and became bound by the, mortgagor’s agreement with the purchaser of the equity of redemption to discharge a part of the mortgage debt merely because it sued the appellants to compel them to pay such portion of the mortgage debt as they had themselves assumed. It is obvious that, in bringing such suit, the mortgagee did not intend to release its lien upon any part of the mortgaged property. That proceeding cannot be regarded as an action at law, since the assumption agreement did not create any privity of contract between the plaintiff company and the appellants which would sustain such an action. Keller v. Ashford, 133 U. S. 610, 621, 622, 10 Sup. Ct. 494. In the state of Minnesota, where the suit was brought, there is but one form of action for the enforcement of private rights (Gen. St. Minn. 1894, § 5131, c. 66); and, whatever may have been the form of the suit in question, it was essentially an equitable proceeding to reach an additional obligation or security that had been given for the satisfaction of a part of the mortgage debt. The mortgagee was entitled to avail itself of that security by virtue of a well-established equitable doctrine, because the security or obligation was held by the mortgagor, who, with respect to the appellants, had become their surety for the payment of that part of the mortgage indebtedness which the appellants had assumed. Being an equitable proceeding to reach and appropriate the additional security that had been created by the assumption agreement, it is undoubtedly true that the appellants were entitled, by way of defense to the claim, to plead any facts or circumstances which rendered the enforcement of the additional obligation either unjust or inequitable. Such a defense was in fact attempted by the appellants, but the facts which they alleged and relied upon to defeat the suit were adjudged insufficient for that purpose by the supreme court of Minnesota (62 Minn. 407, 64 N. W. 1137); and in this proceeding that adjudication must be regarded as conclusive.
The suit at bar proceeds upon the theory that the lien of the mortgage has never been released as respects any part of the mortgaged property, except the 48 feet fronting on Tenth street, which was released by the plaintiff company on June 2, 1890. The mortgagee seeks to have the lien of its mortgage enforced simply as against the. mortgaged property. It did not demand a judgment over against the appellants in case there 'Should be a deficiency in the proceeds of the *333foreclosure sale; nor was provision made for the entry of such a judgment by the decree of the circuit court. In other words, the plaintiff company in this proceeding does not ask for any relief under or by virtue of the assumption agreement, because the rights created by that agreement were adjudicated in the suit which was brought in the state court. The relief prayed for in this action cannot he denied, unless it is held that the mortgagor has released its lien upon the 85 feet fronting on Jackson street, which the appellants purchased, or has heretofore entered into an agreement with the appellants not to enforce the lien of the mortgage, as against said property; and, for the reasons heretofore indicated, we are unable to so hold. The result is that the decree of the circuit court will he affirmed.