The firemen's civil service commission in each municipality shall make rules providing for both competitive and medical examinations for appointments and promotions to all positions in the paid fire department in the municipality, and for other matters as are necessary to carry out the purposes of the civil service provisions of this article. Any commission shall have the power and authority to require by rules a physical fitness examination as a part of its competitive examination or as a part of its medical examination: Provided, That after June 30, 1981, the medical requirements for appointment to all positions in the paid fire department in the municipality shall include, but not be limited to, the medical requirements stated in section sixteen, article twenty-two of this chapter. Due notice of the contents of the rules and of any modifications thereof shall be given, by mail, in due season, to the appointing officer; and the rules and any modifications thereof shall also be printed for public distribution. All original appointments to any positions in a paid fire department subject to the civil service provisions of this article shall be for a probationary period of one year: Provided, however, That at any time during the probationary period the probationer may be discharged for just cause, in the manner provided in section twenty-five of this article. If, at the close of this probationary term, the conduct or capacity of the probationer has not been satisfactory to the appointing officer, the probationer shall be notified, in writing, that he or she will not receive absolute appointment, whereupon his or her employment shall cease; otherwise, his or her retention in the service shall be equivalent to his or her final appointment.