§ 73. Examination of insolvent. At the hearing or trial, the petitioner must be examined under oath, at the instance of any creditor, touching his property or debts, or any other matter stated in his schedule, or any changes that have occurred in the situation of his property, since the making of the schedule; and particularly whether he has collected any debts or demands, or made any transfers of, or otherwise affected, his real or personal property. Any creditor may contradict or impeach, by other competent evidence, the testimony of the insolvent or of his wife.