Every person who shall fail to attend when lawfully summoned to appear as a grand or petit juror, without having a reasonable excuse, shall be considered as guilty of a contempt, and shall be fined by the courts, respectively, in any sum not less than $5 nor more than $100, for the use of the proper county, unless good cause be shown for such default; and it shall be the duty of the court to enter an order of attachment, returnable forthwith, against all such delinquents, and upon the return thereof the court shall proceed to assess the fine unless the person or persons so attached shall show good cause for such delinquency: Provided, that the oath or affirmation of any such delinquent shall, at all times, be received as competent evidence.