In selecting the jury from the persons summoned, the names of such persons shall be called in the order in which they appear upon the list furnished the defendant. Each juror shall be tried and passed upon separately. A person who has been summoned, but who is not present, may, upon his appearance before the jury is completed, be tried as to his qualifications and impaneled as a juror, unless challenged, but no cause shall be unreasonably delayed on account of such absence.