Upon the service of such summons and affidavit, the defendant may answer within the time specified therein, denying the judgment, or setting up any defense which may have arisen subsequently to the taking of the judgment, or he may deny his liability on the obligation upon which the judgment was rendered, except a discharge from such liability by the statute of limitations.
[Code 1881 § 317; 1877 p 65 § 321; RRS § 439.]