In every Action of Divorce for Adultery at the Instance of the Husband it shall be competent to cite, either at the Commencement or during the Dependence thereof, as a Co-Defender along with the Wife, the Person with whom she is alleged to have committed Adultery; and it shall be lawful for the Court in such Action to decern against the Person with whom the Wife is proved to have committed Adultery for the Payment of whole or any Part of the Expenses of Process, provided he has been cited as aforesaid, and the same shall be taxed as between Agent and Client: Provided always, that it shall be competent to examine the Person with whom the Wife is said to have committed Adultery as a Witness in the Cause, notwithstanding he is called as a Co-Defender in the Action, and in the Power of the Court, on Cause shown, to dismiss such Action as regards such Co-Defender, if in their Opinion such a Course is conducive to the Justice of the Case.