delivered the opinion of the Court. The rules of practice in relation to parties are not very clearly defined, and the decisions are apparently at variance ; but they may, we think, be reconciled.

It is a well settled rule, that all parties interested in the subject matter of a suit are to be made parties, but to this rule, as Lord Redesdale observes, there are many exceptions. Another rule is, that no person is necessarily to be made a party, unless his interest may be affected by the decree. To reconcile these rules we must construe the first as extending only to persons interested in the event of the suit, and not to persons interested only in the question involved in the issue. And we think the rule is to be so understood. There is however another rule to be noticed, which is, that where a defendant is interested in having another made a party defendant, the plaintiff is obliged to make him a party, so that the principal defendant may have his assistance in the defence. This rule is an exception to the second rule mentioned, and must be understood with this limitation, that a defendant is not entitled to the assistance of a mere witness ; for if one be made a party against whom the plaintiff can have no decree, but who may be examined as a witness, the defendant may demur. Steward v. East India Co. 2 Vern. 380; Newman v. Godfrey, 2 Bro. Ch. R. 332; 3 P. Wms. 310.

A party, to entitle himself to the assistance of a third party, within the meaning of the rule, must make it appear that he has a right to claim through or rely upon the equitable title of the third party.

Thus, if this were a bill for specific performance, Russell should be made a co-plaintiff, for in equity the plaintiff Williams has a right to claim through him, and without his aid a bill for a specific performance could not be maintained. So if a defendant connects himself with the equitable title of a third person which rebuts the plaintiff’s claim, he would have a right to have the third person a party. This right is somewhat sim*166ilar to the right of praying aid in a real action. These rules being thus understood, we are of opinion that Ricketson and others, the promisors in the notes held by the banks, are not necessary parties in this suit. The Court can pass no decree aganst them. Their liabilities are legal liabilities, and are not within the equitable jurisdiction of this Court. They are not trustees, and cannot be bound by any decree in this case.

The defendants have no interest, within the meaning of the rule, to have them made parties, for they may be examined as witnesses, and thus may aid them in their defence as effectually as they would do if they were made parties.

Demurrer overruled.