Constitution of the State of Texas 1876 Art. 5, § 11. Disqualification of judges;  exchange of districts;  holding court for other judges

No judge shall sit in any case wherein the judge may be interested, or where either of the parties may be connected with the judge, either by affinity or consanguinity, within such a degree as may be prescribed by law, or when the judge shall have been counsel in the case.  When the Supreme Court, the Court of Criminal Appeals, the Court of Appeals, or any member of any of those courts shall be thus disqualified to hear and determine any case or cases in said court, the same shall be certified to the Governor of the State, who shall immediately commission the requisite number of persons learned in the law for the trial and determination of such cause or causes.  When a judge of the District Court is disqualified by any of the causes above stated, the parties may, by consent, appoint a proper person to try said case;  or upon their failing to do so, a competent person may be appointed to try the same in the county where it is pending, in such manner as may be prescribed by law.

And the District Judges may exchange districts, or hold courts for each other when they may deem it expedient, and shall do so when required by law.  This disqualification of judges of inferior tribunals shall be remedied and vacancies in their offices filled as may be prescribed by law.