If a mortgagee, after having assigned the mortgage, receives a conveyance of the mortgaged premises from the mortgagor, agreeing to discharge the latter from liability on the note, the subsequent assent of the assignee to such discharge does not estop him from insisting upon the mortgage security as against the mortgagee and his grantees. An assignment of a recorded mortgage and the note by a mortgagee, after the debt has been paid to him, is not valid as against his subsequent assignment of a second mortgage executed and recorded prior to the first assignment. If a mortgagor conveys the land to the mortgagee in payment of the mortgage debt, but does not have the mortgage discharged on the record or the note cancelled, and the mortgagee assigns the mortgage to another for value, the latter's title will prevail over that of subsequent grantees of the mortgagee. The union of the mortgagor's and mortgagee's title in the latter does not necessarily amount to a merger. An assignment and delivery of a mortgage-note transfers the mortgagee's title under the mortgage. A conveyance of land to be held by the grantee on a secret trust for the benefit of the grantor is void as against mechanics' liens for labor subsequently performed in erecting a building upon the land under a contract with the grantor. A grantee of land is not entitled to have a previous conveyance by the grantor set aside, because it was fraudulent as to creditors.