Any policeman suspending the performance of his duty on account of disability may be summoned to appear before the board, herein provided for, at any time thereafter, and shall submit himself thereto for examination as to his fitness for duty, and shall abide by the decision and order of such board with reference thereto, and all members of the police force who may be retired under the provisions of this chapter, except those who voluntarily retire after twenty (20) years' service, shall report to the chief of police where so retired on the second Tuesday of each and every month, and in case of emergency may be assigned to and shall perform such duty as said chief of police may direct; and such person shall have no claim against the city, for payment for such duty so performed. (R.O. 1959, Ch. 32, Sec. 8)