At least 10 days and not more than 20 days before the holding of any term for the trial of jury cases in the justice court in any such city, the clerk of the justice court shall draw the names of 10 persons and any additional number that may be ordered by the justices of the peace of the city. Additional jurors may be drawn from time to time to fill vacancies in the jury panel for any term of court upon the order of the justices of the peace.