"SEC. 29. Jurisdiction  of the Court  of Appeals.—The Court of Appeals shall have exclusive appellate jurisdiction over all cases, actions, and proceedings, not enumerated in section seventeen of this Act, properly brought to it, ex­cept final judgments or decisions of Courts of First Instance rendered after trial on the merits in the exercise of ap­pellate jurisdiction, which affirm in full the judgment or decision of a municipal or city court, in which cases the aggrieved party may elevate the matter to the Court of Appeals only on petition for review, to which the Court of Appeals shall give due course only when the petition shows prima facie that the court has committed errors of fact  and law that would warrant reversal or modification of the judgment or decision sought to be reviewed.  The decision of the Court of Appeals shall be final: Provided, however,That the Supreme Court in its discretion may, in any case involving a question of law, upon petition  of  the  party aggrieved by the decision and under rules  and conditions that it may prescribe, require by certiorari that the said case be certified to it for review and determination, as if the case had been brought before it on  appeal."