If the question raised by it is legally before us, and the court should be of opinion that the facts stated in it disqualify the plaintiff from becoming a citizen, in the sense in which that word is used in the Constitution of the United States, then the judgment of the Circuit Court is erroneous, and must be reversed. It is suggested, however, that this plea is not before us; and that as the judgment in the court below on this plea was in favor of the plaintiff, he does not seek to reverse it, or bring it before the court for revision by his writ of error; and also that the defendant waived this defence by pleading over, and thereby admitted the jurisdiction of the court. But, in making this objection, we think the peculiar and limited jurisdiction of courts of the United States has not been adverted to. This peculiar and limited jurisdiction has made it necessary, in these courts, to adopt different rules and principles of pleading, so far as jurisdiction is concerned, from those which regulate courts of common law in England, and in the different States of the Union which have adopted the common-law rules. In these last-mentioned courts, where their character and rank are analogous to that of a Circuit Court of the United States; in other words, where they are what the law terms courts of general jurisdiction; they are presumed to have jurisdiction, unless the contrary appears. No averment in the pleadings of the plaintiff is necessary, in order to give jurisdiction. If the defendant objects to it, he must plead it specially, and unless the fact on which he relies is found to be true by a jury, or admitted to be true by the plaintiff, the jurisdiction cannot be disputed in an appellate court. Now, it is not necessary to inquire whether in courts of that description a party who pleads over in bar, when a plea to the jurisdiction has been ruled against him, does or does not waive his plea; nor whether upon a judgment in his favor on the pleas in bar, and a writ of error brought by the plaintiff, the question upon the plea in abatement would be open for revision in the appellate court. Cases that may have been decided in such courts, or rules that may have been laid down by common-law pleaders, can have no influence in the decision in this court. Because, under the Constitution and laws of the United States, the rules which govern the pleadings in its courts, in questions of jurisdiction, stand on different principles and are regulated by different laws.