If the statement of claim be in proper form, the Collector, except as otherwise hereinafter especially provided, shall direct the issue of a summons to the defendant, and if the plaintiff require the personal attendance of the defendant, and satisfy the Collector that such personal attendance is necessary, or the Collector of his own accord require such personal attendance, the summons shall contain an order for the defendant to appear personally on a day to be specified in the summons, otherwise the summons shall order the defendant to appear personally or by an agent duly authorized on his behalf, who has personal knowledge of the subject, or who shall be accompanied by a person who has such personal knowledge.