No senator or representative shall, during the time for which he shall have been elected, be appointed to any civil office under this commonwealth; and no member of Congress or other person holding any office, except of attorney-at-law or in the militia, under the United States or this commonwealth, shall be a member of either House during his continuance in office. They shall receive no other compensation, fees or perquisites of office for their services from any source, nor hold any other office of profit under the United States, this state or any other state.