¶1delivered the opinion of the cour-t.
¶2The main objection taken to the plaintiffs’ right of recovery is, that the lease under which they claim is void ; first, because it is in violation of the condition on which the grant of the lands was made by Congress; and, secondly, because the mortgage to the treasurer of the state, which had been previously executed by the lessor, was still outstanding. Whatever title the state of Missouri acquired by the act of Congress of the 10th of June, 1852, was vested in the Pacific Railroad by the act of the general assembly approved December 25, 1852 ; and whether the state acquired the fee simple title to the lands, clothed with a trust for. the execution of which the public faith was pledged by accepting the grant, or whether the act of Congress granted an estate upon conditions subsequent, is immaterial to the decision of this case. Whenever the United States interpose for the purpose of having a trust executed, or enter for a broken condition, it will be time then to determine the legal character and conditions of the grant; but a mere trespasser can not protect himself under any right which the United States might assert; (Cooper v. Roberts, 18 How. 181;) and, as conditions are only reserved for the benefit of the grantor, a stranger can not take advantage of the broach of them. (4 Kent, 127.)
¶3The modern doctrine is well established that a mortgage is but a security for the payment of the debt or the discharge of the engagement for which it was originally given, and until the mortgagee enters for breach of the condition, and in many respects until final foreclosure of the mortgage, the *146mortgagor continues the owner of the estate, and has a right to lease, sell, and in every respect to deal with the mortgaged premises as owner, so long as he is permitted to remain in possession. (4 Kent, 157.) Of course he can not impair the rights of the mortgagee, and every person taking under him will hold subject to the mortgage and to all the rights of the mortgagee. It does not appear that the mortgagee has ever objected to the lease as interfering with his rights or as impairing the security the mortgage was intended to give, or that there has been any forfeiture of the conditions ; and a stranger surely should not be permitted to volunteer such objections, which are strictly technical, to avoid liability for unauthorized trespasses.
¶4The demurrer was improperly sustained, and the judgment will be reversed and the cause remand;