In the county where it may be necessary, in the discretion of the court or judge, the court may designate a certain portion of the time allotted for the holding of court exclusively to the civil business and a certain portion of the time exclusively to the hearing of criminal business, and in cases where the court or judge does this, the court or judge shall so allot the time as to meet the necessities of the criminal and civil business, and, in all cases where it is practical to do so, the court or judge shall separate the civil and criminal business, so that certain time shall be devoted to each.