In matters of arbitration, the exception relating to the existence of an arbitration clause is procedural in nature and constitutes a question of jurisdiction which is not of a mandatory character, and therefore is not susceptible to being raised *ex officio*, given that it is founded exclusively upon the will of the parties, who are free to choose whether or not to entrust the dispute to arbitrators. The exception of lack of jurisdiction of the court by reason of an arbitration agreement must be raised, on pain of waiver, in the statement of defence, and the failure to raise the exception excludes arbitral jurisdiction limited to the dispute decided in those proceedings.