Complex sentence: Harrison served on the Senate Finance Committee and was chairman of that body from 1933 to 1941 (Seventy-third through Seventy-seventh Congresses) and served as President pro tempore of the Senate during the Seventy-seventh Congress.
Split into simpler sentences: Harrison served on the Committee on Finance and was chairman of that body from 1933 to 1941 (Seventy-third through Seventy-seventh Congresses). He served as President pro tempore of the Senate during the Seventy-seventh Congress.