Each committee provided for in this act, and its officers, shall have the powers usually exercised by such committees and by the officers thereof, insofar as is consistent with this act. The various officers and committees now in existence shall exercise the powers and perform the duties herein prescribed until their successors are chosen in accordance with this act. The duties of the chairman or secretary of any committee, when the committee is not in session, may be performed by members of such committees selected by such chairman or secretary. Any vacancy in any committee office shall be filled in the same manner as that in which such officer was originally chosen.